ANSSI-BP-028 (intermediary)


Mapping CCE Rule Title Description Rationale Variable Setting
R5 CCE-80828-7 Set Boot Loader Password in grub2 The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings.

Since plaintext passwords are a security risk, generate a hash for the password by running the following command: 
# grub2-setpassword
When prompted, enter the password that was selected.

Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode.
R5 CCE-80829-5 Set the UEFI Boot Loader Password The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings.

Since plaintext passwords are a security risk, generate a hash for the password by running the following command: 
# grub2-setpassword
When prompted, enter the password that was selected.

Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode.
R8 CCE-88123-5 Configure L1 Terminal Fault mitigations L1 Terminal Fault (L1TF) is a hardware vulnerability which allows unprivileged speculative access to data which is available in the Level 1 Data Cache when the page table entry isn't present. Select the appropriate mitigation by adding the argument l1tf=full_force to the default GRUB 2 command line for the Linux operating system. To ensure that l1tf=full_force is added as a kernel command line argument to newly installed kernels, add l1tf=full_force to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... l1tf=full_force ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="l1tf=full_force"
Since Linux Kernel 4.19 you can check the L1TF vulnerability state with the following command: cat /sys/devices/system/cpu/vulnerabilities/l1tf 		The L1TF vulnerability allows an attacker to bypass memory access security controls imposed by the system or hypervisor. The L1TF vulnerability allows read access to any physical memory location that is cached in the L1 Data Cache. var_l1tf_options=full_force
R8 CCE-87098-0 Force kernel panic on uncorrected MCEs A Machine Check Exception is an error generated by the CPU itdetects an error in itself, memory or I/O devices. These errors may be corrected and generate a check log entry, if an error cannot be corrected the kernel may panic or SIGBUS. To force the kernel to panic on any uncorrected error reported by Machine Check set the MCE tolerance to zero by adding mce=0 to the default GRUB 2 command line for the Linux operating system. To ensure that mce=0 is added as a kernel command line argument to newly installed kernels, add mce=0 to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... mce=0 ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="mce=0"
 Allowing uncorrected errors to result on a SIGBUS may allow an attacker to continue trying to exploit a vulnerability such as Rowhammer.
R8 CCE-80944-2 Enable page allocator poisoning To enable poisoning of free pages, add the argument page_poison=1 to the default GRUB 2 command line for the Linux operating system. To ensure that page_poison=1 is added as a kernel command line argument to newly installed kernels, add page_poison=1 to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... page_poison=1 ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="page_poison=1"
 Poisoning writes an arbitrary value to freed pages, so any modification or reference to that page after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory.
R8 CCE-82194-2 Enable Kernel Page-Table Isolation (KPTI) To enable Kernel page-table isolation, add the argument pti=on to the default GRUB 2 command line for the Linux operating system. To ensure that pti=on is added as a kernel command line argument to newly installed kernels, add pti=on to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... pti=on ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="pti=on"
 Kernel page-table isolation is a kernel feature that mitigates the Meltdown security vulnerability and hardens the kernel against attempts to bypass kernel address space layout randomization (KASLR).
R8 CCE-89567-2 Configure the confidence in TPM for entropy The TPM security chip that is available in most modern systems has a hardware RNG. It is also used to feed the entropy pool, but generally not credited entropy. Use rng_core.default_quality in the kernel command line to set the trust level on the hardware generators. The trust level defines the amount of entropy to credit. A value of 0 tells the system not to trust the hardware random number generators available, and doesn't credit any entropy to the pool. A value of 1000 assigns full confidence in the generators, and credits all the entropy it provides to the pool. Note that the value of rng_core.default_quality is global, affecting the trust on all hardware random number generators. Select the appropriate confidence by adding the argument rng_core.default_quality=500 to the default GRUB 2 command line for the Linux operating system. To ensure that rng_core.default_quality=500 is added as a kernel command line argument to newly installed kernels, add rng_core.default_quality=500 to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... rng_core.default_quality=500 ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="rng_core.default_quality=500"
 A system may struggle to initialize its entropy pool and end up starving. Crediting entropy from the hardware number generators available in the system helps fill up the entropy pool. var_rng_core_default_quality=500
R8 CCE-86777-0 Disable merging of slabs with similar size The kernel may merge similar slabs together to reduce overhead and increase cache hotness of objects. Disabling merging of slabs keeps the slabs separate and reduces the risk of kernel heap overflows overwriting objects in merged caches. To disable merging of slabs in the Kernel add the argument slab_nomerge=yes to the default GRUB 2 command line for the Linux operating system. To ensure that slab_nomerge=yes is added as a kernel command line argument to newly installed kernels, add slab_nomerge=yes to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... slab_nomerge=yes ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="slab_nomerge=yes"
 Disabling the merge of slabs of similar sizes prevents the kernel from merging a seemingly useless but vulnerable slab with a useful and valuable slab. This increase the risk that a heap overflow could overwrite objects from merged caches, with unmerged caches the heap overflow would only affect the objects in the same cache. Overall, this reduces the kernel attack surface area by isolating slabs from each other.
R8 CCE-80945-9 Enable SLUB/SLAB allocator poisoning To enable poisoning of SLUB/SLAB objects, add the argument slub_debug=FZP to the default GRUB 2 command line for the Linux operating system. To ensure that slub_debug=FZP is added as a kernel command line argument to newly installed kernels, add slub_debug=FZP to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... slub_debug=FZP ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="slub_debug=FZP"
 Poisoning writes an arbitrary value to freed objects, so any modification or reference to that object after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory. var_slub_debug_options=FZP
R8 CCE-89234-9 Configure Speculative Store Bypass Mitigation Certain CPUs are vulnerable to an exploit against a common wide industry wide performance optimization known as Speculative Store Bypass (SSB). In such cases, recent stores to the same memory location cannot always be observed by later loads during speculative execution. However, such stores are unlikely and thus they can be detected prior to instruction retirement at the end of a particular speculation execution window. Since Linux Kernel 4.17 you can check the SSB mitigation state with the following command: cat /sys/devices/system/cpu/vulnerabilities/spec_store_bypass Select the appropriate SSB state by adding the argument spec_store_bypass_disable=seccomp to the default GRUB 2 command line for the Linux operating system. To ensure that spec_store_bypass_disable=seccomp is added as a kernel command line argument to newly installed kernels, add spec_store_bypass_disable=seccomp to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... spec_store_bypass_disable=seccomp ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="spec_store_bypass_disable=seccomp"
 In vulnerable processsors, the speculatively forwarded store can be used in a cache side channel attack. An example of this is reading memory to which the attacker does not directly have access, for example inside the sandboxed code. var_spec_store_bypass_disable_options=seccomp
R8 CCE-89345-3 Enforce Spectre v2 mitigation Spectre V2 is an indirect branch poisoning attack that can lead to data leakage. An exploit for Spectre V2 tricks the indirect branch predictor into executing code from a future indirect branch chosen by the attacker, even if the privilege level is different. Since Linux Kernel 4.15 you can check the Spectre V2 mitigation state with the following command: cat /sys/devices/system/cpu/vulnerabilities/spectre_v2 Enforce the Spectre V2 mitigation by adding the argument spectre_v2=on to the default GRUB 2 command line for the Linux operating system. To ensure that spectre_v2=on is added as a kernel command line argument to newly installed kernels, add spectre_v2=on to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below: 
GRUB_CMDLINE_LINUX="... spectre_v2=on ..."
Run the following command to update command line for already installed kernels:
# grubby --update-kernel=ALL --args="spectre_v2=on"
 The Spectre V2 vulnerability allows an attacker to read memory that he should not have access to.
R8 CCE-83363-2 Prevent applications from mapping low portion of virtual memory To set the runtime status of the vm.mmap_min_addr kernel parameter, run the following command: 
$ sudo sysctl -w vm.mmap_min_addr=65536
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
vm.mmap_min_addr = 65536
 The vm.mmap_min_addr parameter specifies the minimum virtual address that a process is allowed to mmap. Allowing a process to mmap low portion of virtual memory can have security implications such as such as heightened risk of kernel null pointer dereference defects.
R9 CCE-80913-7 Restrict Access to Kernel Message Buffer To set the runtime status of the kernel.dmesg_restrict kernel parameter, run the following command: 
$ sudo sysctl -w kernel.dmesg_restrict=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.dmesg_restrict = 1
 Unprivileged access to the kernel syslog can expose sensitive kernel address information.
R9 CCE-80915-2 Restrict Exposed Kernel Pointer Addresses Access To set the runtime status of the kernel.kptr_restrict kernel parameter, run the following command: 
$ sudo sysctl -w kernel.kptr_restrict=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.kptr_restrict = 2
 Exposing kernel pointers (through procfs or seq_printf()) exposes kernel writeable structures which may contain functions pointers. If a write vulnerability occurs in the kernel, allowing write access to any of this structure, the kernel can be compromised. This option disallow any program without the CAP_SYSLOG capability to get the addresses of kernel pointers by replacing them with 0. sysctl_kernel_kptr_restrict_value=2
R9 CCE-87666-4 Kernel panic on oops To set the runtime status of the kernel.panic_on_oops kernel parameter, run the following command: 
$ sudo sysctl -w kernel.panic_on_oops=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.panic_on_oops = 1
 An attacker trying to exploit the kernel may trigger kernel OOPSes, panicking the system will impede them from continuing.
R9 CCE-83373-1 Limit CPU consumption of the Perf system To set the runtime status of the kernel.perf_cpu_time_max_percent kernel parameter, run the following command: 
$ sudo sysctl -w kernel.perf_cpu_time_max_percent=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.perf_cpu_time_max_percent = 1
 The kernel.perf_cpu_time_max_percent configures a treshold of maximum percentile of CPU that can be used by Perf system. Restricting usage of Perf system decreases risk of potential availability problems.
R9 CCE-83368-1 Limit sampling frequency of the Perf system To set the runtime status of the kernel.perf_event_max_sample_rate kernel parameter, run the following command: 
$ sudo sysctl -w kernel.perf_event_max_sample_rate=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.perf_event_max_sample_rate = 1
 The kernel.perf_event_max_sample_rate parameter configures maximum frequency of collecting of samples for the Perf system. It is expressed in samples per second. Restricting usage of Perf system decreases risk of potential availability problems.
R9 CCE-81054-9 Disallow kernel profiling by unprivileged users To set the runtime status of the kernel.perf_event_paranoid kernel parameter, run the following command: 
$ sudo sysctl -w kernel.perf_event_paranoid=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.perf_event_paranoid = 2
 Kernel profiling can reveal sensitive information about kernel behaviour.
R9 CCE-83366-5 Configure maximum number of process identifiers To set the runtime status of the kernel.pid_max kernel parameter, run the following command: 
$ sudo sysctl -w kernel.pid_max=65536
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.pid_max = 65536
 The kernel.pid_max parameter configures upper limit on process identifiers (PID). If this number is not high enough, it might happen that forking of new processes is not possible, because all available PIDs are exhausted. Increasing this number enhances availability.
R9 CCE-80916-0 Enable Randomized Layout of Virtual Address Space To set the runtime status of the kernel.randomize_va_space kernel parameter, run the following command: 
$ sudo sysctl -w kernel.randomize_va_space=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.randomize_va_space = 2
 Address space layout randomization (ASLR) makes it more difficult for an attacker to predict the location of attack code they have introduced into a process's address space during an attempt at exploitation. Additionally, ASLR makes it more difficult for an attacker to know the location of existing code in order to re-purpose it using return oriented programming (ROP) techniques.
R9 CCE-83355-8 Disallow magic SysRq key To set the runtime status of the kernel.sysrq kernel parameter, run the following command: 
$ sudo sysctl -w kernel.sysrq=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.sysrq = 0
 The Magic SysRq key allows sending certain commands directly to the running kernel. It can dump various system and process information, potentially revealing sensitive information. It can also reboot or shutdown the machine, disturbing its availability.
R9 CCE-82974-7 Disable Access to Network bpf() Syscall From Unprivileged Processes To set the runtime status of the kernel.unprivileged_bpf_disabled kernel parameter, run the following command: 
$ sudo sysctl -w kernel.unprivileged_bpf_disabled=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.unprivileged_bpf_disabled = 1
 Loading and accessing the packet filters programs and maps using the bpf() syscall has the potential of revealing sensitive information about the kernel state.
R11 CCE-80953-3 Restrict usage of ptrace to descendant processes To set the runtime status of the kernel.yama.ptrace_scope kernel parameter, run the following command: 
$ sudo sysctl -w kernel.yama.ptrace_scope=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
kernel.yama.ptrace_scope = 1
 Unrestricted usage of ptrace allows compromised binaries to run ptrace on another processes of the user. Like this, the attacker can steal sensitive information from the target processes (e.g. SSH sessions, web browser, ...) without any additional assistance from the user (i.e. without resorting to phishing).
R12 CCE-82934-1 Harden the operation of the BPF just-in-time compiler To set the runtime status of the net.core.bpf_jit_harden kernel parameter, run the following command: 
$ sudo sysctl -w net.core.bpf_jit_harden=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.core.bpf_jit_harden = 2
 When hardened, the extended Berkeley Packet Filter just-in-time compiler will randomize any kernel addresses in the BPF programs and maps, and will not expose the JIT addresses in /proc/kallsyms.
R12 CCE-88789-3 Disable Accepting Packets Routed Between Local Interfaces To set the runtime status of the net.ipv4.conf.all.accept_local kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.accept_local=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.accept_local = 0
 Configure net.ipv4.conf.all.accept_local=0 to consider as invalid the packets received from outside whose source is the 127.0.0.0/8 address block. In combination with suitable routing, this can be used to direct packets between two local interfaces over the wire and have them accepted properly.
R12 CCE-80917-8 Disable Accepting ICMP Redirects for All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.accept_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.accept_redirects = 0
 ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required."
R12 CCE-81011-9 Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.accept_source_route kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.accept_source_route = 0
 Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
R12 CCE-88555-8 Configure ARP filtering for All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.arp_filter kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.arp_filter=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.arp_filter = 0
 Prevents the Linux Kernel from handling the ARP table globally. By default, the kernel may respond to an ARP request from a certain interface with information from another interface. sysctl_net_ipv4_conf_all_arp_filter_value=0
R12 CCE-88889-1 Configure Response Mode of ARP Requests for All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.arp_ignore kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.arp_ignore=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.arp_ignore = 2
 Avoids ARP Flux on system that have more than one interface on the same subnet. sysctl_net_ipv4_conf_all_arp_ignore_value=2
R12 CCE-88001-3 Drop Gratuitious ARP frames on All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.drop_gratuitous_arp kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.drop_gratuitous_arp=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.drop_gratuitous_arp = 1
 Drop Gratuitous ARP frames to prevent ARP poisoning.
R12 CCE-88023-7 Prevent Routing External Traffic to Local Loopback on All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.route_localnet kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.route_localnet=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.route_localnet = 0
 Refuse the routing of packets whose source or destination address is the local loopback. This prohibits the use of network 127/8 for local routing purposes. Enabling route_localnet can expose applications listening on localhost to external traffic.
R12 CCE-81021-8 Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.rp_filter kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.rp_filter=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.rp_filter = 1
 Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.
R12 CCE-81016-8 Disable Kernel Parameter for Accepting Secure ICMP Redirects on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.secure_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.secure_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.secure_redirects = 0
 Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.
R12 CCE-80918-6 Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.send_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.send_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.send_redirects = 0
 ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.
R12 CCE-88333-0 Configure Sending and Accepting Shared Media Redirects for All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.shared_media kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.all.shared_media=disabled
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.all.shared_media = disabled
 This setting should be aligned with net.ipv4.conf.all.secure_redirects because it overrides it. If shared_media is enabled for an interface secure_redirects will be enabled too. sysctl_net_ipv4_conf_all_shared_media_value=disabled
R12 CCE-80919-4 Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv4 Interfaces To set the runtime status of the net.ipv4.conf.default.accept_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.default.accept_redirects = 0
 ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required.
R12 CCE-80920-2 Disable Kernel Parameter for Accepting Source-Routed Packets on IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.accept_source_route kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.default.accept_source_route = 0
 Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures.
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required, such as when IPv4 forwarding is enabled and the system is legitimately functioning as a router.
R12 CCE-81022-6 Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.rp_filter kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.default.rp_filter=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.default.rp_filter = 1
 Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.
R12 CCE-81017-6 Configure Kernel Parameter for Accepting Secure Redirects By Default To set the runtime status of the net.ipv4.conf.default.secure_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.default.secure_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.default.secure_redirects = 0
 Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.
R12 CCE-80921-0 Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.send_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.default.send_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.default.send_redirects = 0
 ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.
R12 CCE-88444-5 Configure Sending and Accepting Shared Media Redirects by Default To set the runtime status of the net.ipv4.conf.default.shared_media kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.conf.default.shared_media=disabled
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.conf.default.shared_media = disabled
 This setting should be aligned with net.ipv4.conf.default.secure_redirects because it overrides it. If shared_media is enabled for an interface secure_redirects will be enabled too. sysctl_net_ipv4_conf_default_shared_media_value=disabled
R12 CCE-81023-4 Enable Kernel Parameter to Ignore Bogus ICMP Error Responses on IPv4 Interfaces To set the runtime status of the net.ipv4.icmp_ignore_bogus_error_responses kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.icmp_ignore_bogus_error_responses = 1
 Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged.
R12 CCE-81024-2 Disable Kernel Parameter for IP Forwarding on IPv4 Interfaces To set the runtime status of the net.ipv4.ip_forward kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.ip_forward=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.ip_forward = 0
 Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network.
R12 CCE-84277-3 Set Kernel Parameter to Increase Local Port Range To set the runtime status of the net.ipv4.ip_local_port_range kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.ip_local_port_range=32768 65535
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.ip_local_port_range = 32768 65535
 This setting defines the local port range that is used by TCP and UDP to choose the local port. The first number is the first, the second the last local port number.
R12 CCE-84270-8 Enable Kernel Parameter to Use TCP RFC 1337 on IPv4 Interfaces To set the runtime status of the net.ipv4.tcp_rfc1337 kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.tcp_rfc1337=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.tcp_rfc1337 = 1
 Enable TCP behavior conformant with RFC 1337. When disabled, if a RST is received in TIME_WAIT state, we close the socket immediately without waiting for the end of the TIME_WAIT period.
R12 CCE-80923-6 Enable Kernel Parameter to Use TCP Syncookies on Network Interfaces To set the runtime status of the net.ipv4.tcp_syncookies kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv4.tcp_syncookies=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv4.tcp_syncookies = 1
 A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected, and enables the system to continue servicing valid connection requests.
R13 CCE-84272-4 Configure Accepting Default Router in Router Advertisements on All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_ra_defrtr kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.accept_ra_defrtr=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.accept_ra_defrtr = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-84280-7 Configure Accepting Prefix Information in Router Advertisements on All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_ra_pinfo kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.accept_ra_pinfo=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.accept_ra_pinfo = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-84288-0 Configure Accepting Router Preference in Router Advertisements on All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_ra_rtr_pref kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.accept_ra_rtr_pref=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.accept_ra_rtr_pref = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-81009-3 Disable Accepting ICMP Redirects for All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.accept_redirects = 0
 An illicit ICMP redirect message could result in a man-in-the-middle attack.
R13 CCE-81013-5 Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.accept_source_route kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.accept_source_route = 0
 Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
R13 CCE-84266-6 Configure Auto Configuration on All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.autoconf kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.autoconf=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.autoconf = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-84259-1 Configure Maximum Number of Autoconfigured Addresses on All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.max_addresses kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.max_addresses=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.max_addresses = 1
 The number of global unicast IPv6 addresses for each interface should be limited exactly to the number of statically configured addresses.
R13 CCE-84109-8 Configure Denying Router Solicitations on All IPv6 Interfaces To set the runtime status of the net.ipv6.conf.all.router_solicitations kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.all.router_solicitations=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.all.router_solicitations = 0
 To prevent discovery of the system by other systems, router solicitation requests should be denied.
R13 CCE-84268-2 Configure Accepting Default Router in Router Advertisements on All IPv6 Interfaces By Default To set the runtime status of the net.ipv6.conf.default.accept_ra_defrtr kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.accept_ra_defrtr=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.accept_ra_defrtr = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-84051-2 Configure Accepting Prefix Information in Router Advertisements on All IPv6 Interfaces By Default To set the runtime status of the net.ipv6.conf.default.accept_ra_pinfo kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.accept_ra_pinfo=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.accept_ra_pinfo = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-84291-4 Configure Accepting Router Preference in Router Advertisements on All IPv6 Interfaces By Default To set the runtime status of the net.ipv6.conf.default.accept_ra_rtr_pref kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.accept_ra_rtr_pref=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.accept_ra_rtr_pref = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-81010-1 Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv6 Interfaces To set the runtime status of the net.ipv6.conf.default.accept_redirects kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.accept_redirects = 0
 An illicit ICMP redirect message could result in a man-in-the-middle attack.
R13 CCE-81015-0 Disable Kernel Parameter for Accepting Source-Routed Packets on IPv6 Interfaces by Default To set the runtime status of the net.ipv6.conf.default.accept_source_route kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.accept_source_route = 0
 Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router. Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
R13 CCE-84264-1 Configure Auto Configuration on All IPv6 Interfaces By Default To set the runtime status of the net.ipv6.conf.default.autoconf kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.autoconf=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.autoconf = 0
 An illicit router advertisement message could result in a man-in-the-middle attack.
R13 CCE-84257-5 Configure Maximum Number of Autoconfigured Addresses on All IPv6 Interfaces By Default To set the runtime status of the net.ipv6.conf.default.max_addresses kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.max_addresses=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.max_addresses = 1
 The number of global unicast IPv6 addresses for each interface should be limited exactly to the number of statically configured addresses.
R13 CCE-83477-0 Configure Denying Router Solicitations on All IPv6 Interfaces By Default To set the runtime status of the net.ipv6.conf.default.router_solicitations kernel parameter, run the following command: 
$ sudo sysctl -w net.ipv6.conf.default.router_solicitations=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
net.ipv6.conf.default.router_solicitations = 0
 To prevent discovery of the system by other systems, router solicitation requests should be denied.
R14 CCE-81027-5 Enable Kernel Parameter to Enforce DAC on Hardlinks To set the runtime status of the fs.protected_hardlinks kernel parameter, run the following command: 
$ sudo sysctl -w fs.protected_hardlinks=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
fs.protected_hardlinks = 1
 By enabling this kernel parameter, users can no longer create soft or hard links to files which they do not own. Disallowing such hardlinks mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().
R14 CCE-81030-9 Enable Kernel Parameter to Enforce DAC on Symlinks To set the runtime status of the fs.protected_symlinks kernel parameter, run the following command: 
$ sudo sysctl -w fs.protected_symlinks=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
fs.protected_symlinks = 1
 By enabling this kernel parameter, symbolic links are permitted to be followed only when outside a sticky world-writable directory, or when the UID of the link and follower match, or when the directory owner matches the symlink's owner. Disallowing such symlinks helps mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().
R14 CCE-80912-9 Disable Core Dumps for SUID programs To set the runtime status of the fs.suid_dumpable kernel parameter, run the following command: 
$ sudo sysctl -w fs.suid_dumpable=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d: 
fs.suid_dumpable = 0
 The core dump of a setuid program is more likely to contain sensitive data, as the program itself runs with greater privileges than the user who initiated execution of the program. Disabling the ability for any setuid program to write a core file decreases the risk of unauthorized access of such data.
R28 CCE-83316-0 Add noexec Option to /boot The noexec mount option can be used to prevent binaries from being executed out of /boot. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /boot. The /boot partition contains the kernel and the bootloader. No binaries should be executed from this partition after the booting process finishes.
R28 CCE-81033-3 Add nosuid Option to /boot The nosuid mount option can be used to prevent execution of setuid programs in /boot. The SUID and SGID permissions should not be required on the boot partition. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /boot. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from boot partitions.
R28 CCE-83328-5 Add noexec Option to /home The noexec mount option can be used to prevent binaries from being executed out of /home. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /home. The /home directory contains data of individual users. Binaries in this directory should not be considered as trusted and users should not be able to execute them.
R28 CCE-81050-7 Add nosuid Option to /home The nosuid mount option can be used to prevent execution of setuid programs in /home. The SUID and SGID permissions should not be required in these user data directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /home. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from user home directory partitions.
R28 CCE-82069-6 Add nodev Option to Non-Root Local Partitions The nodev mount option prevents files from being interpreted as character or block devices. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of any non-root local partitions. The nodev mount option prevents files from being interpreted as character or block devices. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails, for which it is not advised to set nodev on these filesystems.
R28 CCE-83319-4 Add nosuid Option to /opt The nosuid mount option can be used to prevent execution of setuid programs in /opt. The SUID and SGID permissions should not be required in this directory. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /opt. The presence of SUID and SGID executables should be tightly controlled. The /opt directory contains additional software packages. Users should not be able to execute SUID or SGID binaries from this directory.
R28 CCE-83322-8 Add nosuid Option to /srv The nosuid mount option can be used to prevent execution of setuid programs in /srv. The SUID and SGID permissions should not be required in this directory. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /srv. The presence of SUID and SGID executables should be tightly controlled. The /srv directory contains files served by various network services such as FTP. Users should not be able to execute SUID or SGID binaries from this directory.
R28 CCE-82139-7 Add noexec Option to /tmp The noexec mount option can be used to prevent binaries from being executed out of /tmp. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. Allowing users to execute binaries from world-writable directories such as /tmp should never be necessary in normal operation and can expose the system to potential compromise.
R28 CCE-82140-5 Add nosuid Option to /tmp The nosuid mount option can be used to prevent execution of setuid programs in /tmp. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
R28 CCE-82008-4 Add noexec Option to /var/log The noexec mount option can be used to prevent binaries from being executed out of /var/log. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /var/log. Allowing users to execute binaries from directories containing log files such as /var/log should never be necessary in normal operation and can expose the system to potential compromise.
R28 CCE-82065-4 Add nosuid Option to /var/log The nosuid mount option can be used to prevent execution of setuid programs in /var/log. The SUID and SGID permissions should not be required in directories containing log files. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /var/log. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from partitions designated for log files.
R28 CCE-83330-1 Add noexec Option to /var The noexec mount option can be used to prevent binaries from being executed out of /var. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /var. The /var directory contains variable system data such as logs, mails and caches. No binaries should be executed from this directory.
R28 CCE-83383-0 Add nosuid Option to /var The nosuid mount option can be used to prevent execution of setuid programs in /var. The SUID and SGID permissions should not be required for this directory. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /var. The presence of SUID and SGID executables should be tightly controlled.
R28 CCE-82151-2 Add noexec Option to /var/tmp The noexec mount option can be used to prevent binaries from being executed out of /var/tmp. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /var/tmp. Allowing users to execute binaries from world-writable directories such as /var/tmp should never be necessary in normal operation and can expose the system to potential compromise.
R28 CCE-82154-6 Add nosuid Option to /var/tmp The nosuid mount option can be used to prevent execution of setuid programs in /var/tmp. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /var/tmp. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
R28 CCE-83336-8 Ensure /boot Located On Separate Partition It is recommended that the /boot directory resides on a separate partition. This makes it easier to apply restrictions e.g. through the noexec mount option. Eventually, the /boot partition can be configured not to be mounted automatically with the noauto mount option. The /boot partition contains the kernel and bootloader files. Access to this partition should be restricted.
R28 CCE-81044-0 Ensure /home Located On Separate Partition If user home directories will be stored locally, create a separate partition for /home at installation time (or migrate it later using LVM). If /home will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later. Ensuring that /home is mounted on its own partition enables the setting of more restrictive mount options, and also helps ensure that users cannot trivially fill partitions used for log or audit data storage.
R28 CCE-83340-0 Ensure /opt Located On Separate Partition It is recommended that the /opt directory resides on a separate partition. The /opt partition contains additional software, usually installed outside the packaging system. Putting this directory on a separate partition makes it easier to apply restrictions e.g. through the nosuid mount option.
R28 CCE-83387-1 Ensure /srv Located On Separate Partition If a file server (FTP, TFTP...) is hosted locally, create a separate partition for /srv at installation time (or migrate it later using LVM). If /srv will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later. Srv deserves files for local network file server such as FTP. Ensuring that /srv is mounted on its own partition enables the setting of more restrictive mount options, and also helps ensure that users cannot trivially fill partitions used for log or audit data storage.
R28 CCE-83343-4 Ensure /usr Located On Separate Partition It is recommended that the /usr directory resides on a separate partition. The /usr partition contains system software, utilities and files. Putting it on a separate partition allows limiting its size and applying restrictions through mount options.
R28 CCE-80852-7 Ensure /var Located On Separate Partition The /var directory is used by daemons and other system services to store frequently-changing data. Ensure that /var has its own partition or logical volume at installation time, or migrate it using LVM. Ensuring that /var is mounted on its own partition enables the setting of more restrictive mount options. This helps protect system services such as daemons or other programs which use it. It is not uncommon for the /var directory to contain world-writable directories installed by other software packages.
R28 CCE-80853-5 Ensure /var/log Located On Separate Partition System logs are stored in the /var/log directory. Ensure that /var/log has its own partition or logical volume at installation time, or migrate it using LVM. Placing /var/log in its own partition enables better separation between log files and other files in /var/.
R28 CCE-82730-3 Ensure /var/tmp Located On Separate Partition The /var/tmp directory is a world-writable directory used for temporary file storage. Ensure it has its own partition or logical volume at installation time, or migrate it using LVM. The /var/tmp partition is used as temporary storage by many programs. Placing /var/tmp in its own partition enables the setting of more restrictive mount options, which can help protect programs which use it.
R28 CCE-86890-1 Ensure tmp.mount Unit Is Enabled The /tmp directory is a world-writable directory used for temporary file storage. This directory is managed by systemd-tmpfiles. Ensure that the tmp.mount systemd unit is enabled. The /tmp directory is used as temporary storage by many programs. Placing /tmp in a tmpfs filesystem enables the setting of more restrictive mount options, which can help protect programs which use it. The tmp.mount unit configures the tmpfs filesystem and ensures the /tmp directory is wiped during reboot.
R31 CCE-80652-1 Set Password Minimum Length in login.defs To specify password length requirements for new accounts, edit the file /etc/login.defs and add or correct the following line: 
PASS_MIN_LEN 15


The DoD requirement is 15. The FISMA requirement is 12. The profile requirement is 15. If a program consults /etc/login.defs and also another PAM module (such as pam_pwquality) during a password change operation, then the most restrictive must be satisfied. See PAM section for more information about enforcing password quality requirements. 		Requiring a minimum password length makes password cracking attacks more difficult by ensuring a larger search space. However, any security benefit from an onerous requirement must be carefully weighed against usability problems, support costs, or counterproductive behavior that may result. var_accounts_password_minlen_login_defs=15
R31 CCE-80653-9 Ensure PAM Enforces Password Requirements - Minimum Digit Characters The pam_pwquality module's dcredit parameter controls requirements for usage of digits in a password. When set to a negative number, any password will be required to contain that many digits. When set to a positive number, pam_pwquality will grant +1 additional length credit for each digit. Modify the dcredit setting in /etc/security/pwquality.conf to require the use of a digit in passwords. Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Requiring digits makes password guessing attacks more difficult by ensuring a larger search space.
R31 CCE-80655-4 Ensure PAM Enforces Password Requirements - Minimum Lowercase Characters The pam_pwquality module's lcredit parameter controls requirements for usage of lowercase letters in a password. When set to a negative number, any password will be required to contain that many lowercase characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each lowercase character. Modify the lcredit setting in /etc/security/pwquality.conf to require the use of a lowercase character in passwords. Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.
Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possble combinations that need to be tested before the password is compromised. Requiring a minimum number of lowercase characters makes password guessing attacks more difficult by ensuring a larger search space.
R31
R68		 CCE-80656-2 Ensure PAM Enforces Password Requirements - Minimum Length The pam_pwquality module's minlen parameter controls requirements for minimum characters required in a password. Add minlen=15 after pam_pwquality to set minimum password length requirements. The shorter the password, the lower the number of possible combinations that need to be tested before the password is compromised.
Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to exponentially increase the time and/or resources required to compromise the password. 		var_password_pam_minlen=15
R31 CCE-80663-8 Ensure PAM Enforces Password Requirements - Minimum Special Characters The pam_pwquality module's ocredit= parameter controls requirements for usage of special (or "other") characters in a password. When set to a negative number, any password will be required to contain that many special characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each special character. Modify the ocredit setting in /etc/security/pwquality.conf to equal 1 to require use of a special character in passwords. Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Requiring a minimum number of special characters makes password guessing attacks more difficult by ensuring a larger search space. 		var_password_pam_ocredit=1
R31 CCE-80665-3 Ensure PAM Enforces Password Requirements - Minimum Uppercase Characters The pam_pwquality module's ucredit= parameter controls requirements for usage of uppercase letters in a password. When set to a negative number, any password will be required to contain that many uppercase characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each uppercase character. Modify the ucredit setting in /etc/security/pwquality.conf to require the use of an uppercase character in passwords. Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.
R31 CCE-80666-1 Limit Password Reuse Do not allow users to reuse recent passwords. This can be accomplished by using the remember option for the pam_unix or pam_pwhistory PAM modules. Preventing re-use of previous passwords helps ensure that a compromised password is not re-used by a user.
R31 CCE-87667-2 Set Root Account Password Maximum Age Configure the root account to enforce a 365-day maximum password lifetime restriction by running the following command: 
$ sudo chage -M 365 root
 Any password, no matter how complex, can eventually be cracked. Therefore, passwords need to be changed periodically. If the operating system does not limit the lifetime of passwords and force users to change their passwords, there is the risk that the operating system passwords could be compromised. var_accounts_maximum_age_root=365
R31 CCE-80667-9 Lock Accounts After Failed Password Attempts This rule configures the system to lock out accounts after a number of incorrect login attempts using pam_faillock.so. pam_faillock.so module requires multiple entries in pam files. These entries must be carefully defined to work as expected. Ensure that the file /etc/security/faillock.conf contains the following entry: deny = <count> Where count should be less than or equal to 3 and greater than 0. In order to avoid errors when manually editing these files, it is recommended to use the appropriate tools, such as authselect or authconfig, depending on the OS version. By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, also known as brute-forcing, is reduced. Limits are imposed by locking the account. var_accounts_passwords_pam_faillock_deny=3
R31 CCE-80668-7 Configure the root Account for Failed Password Attempts This rule configures the system to lock out the root account after a number of incorrect login attempts using pam_faillock.so. pam_faillock.so module requires multiple entries in pam files. These entries must be carefully defined to work as expected. In order to avoid errors when manually editing these files, it is recommended to use the appropriate tools, such as authselect or authconfig, depending on the OS version. By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, also known as brute-forcing, is reduced. Limits are imposed by locking the account.
R31 CCE-80669-5 Set Interval For Counting Failed Password Attempts Utilizing pam_faillock.so, the fail_interval directive configures the system to lock out an account after a number of incorrect login attempts within a specified time period. Ensure that the file /etc/security/faillock.conf contains the following entry: fail_interval = <interval-in-seconds> where interval-in-seconds is 900 or greater. In order to avoid errors when manually editing these files, it is recommended to use the appropriate tools, such as authselect or authconfig, depending on the OS version. By limiting the number of failed logon attempts the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced. Limits are imposed by locking the account. var_accounts_passwords_pam_faillock_fail_interval=900
R31 CCE-80670-3 Set Lockout Time for Failed Password Attempts This rule configures the system to lock out accounts during a specified time period after a number of incorrect login attempts using pam_faillock.so. Ensure that the file /etc/security/faillock.conf contains the following entry: unlock_time=<interval-in-seconds> where interval-in-seconds is 900 or greater. pam_faillock.so module requires multiple entries in pam files. These entries must be carefully defined to work as expected. In order to avoid any errors when manually editing these files, it is recommended to use the appropriate tools, such as authselect or authconfig, depending on the OS version. If unlock_time is set to 0, manual intervention by an administrator is required to unlock a user. This should be done using the faillock tool. By limiting the number of failed logon attempts the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced. Limits are imposed by locking the account. var_accounts_passwords_pam_faillock_unlock_time=900
R31 CCE-88248-0 Enable authselect Configure user authentication setup to use the authselect tool. If authselect profile is selected, the rule will enable the minimal profile. Authselect is a successor to authconfig. It is a tool to select system authentication and identity sources from a list of supported profiles instead of letting the administrator manually build the PAM stack. That way, it avoids potential breakage of configuration, as it ships several tested profiles that are well tested and supported to solve different use-cases. var_authselect_profile=minimal
R32 CCE-80673-7 Set Interactive Session Timeout Setting the TMOUT option in /etc/profile ensures that all user sessions will terminate based on inactivity. The value of TMOUT should be exported and read only. The TMOUT setting in a file loaded by /etc/profile, e.g. /etc/profile.d/tmout.sh should read as follows: 
typeset -xr TMOUT=10_min
or 
declare -xr TMOUT=10_min
Using the typeset keyword is preferred for wider compatibility with ksh and other shells. 		Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. var_accounts_tmout=10_min
R32 CCE-90784-0 Configure Logind to terminate idle sessions after certain time of inactivity To configure logind service to terminate inactive user sessions after 10_minutes seconds, edit the file /etc/systemd/logind.conf. Ensure that there is a section 
[Login]
which contains the configuration 
StopIdleSessionSec=10_minutes
. 		Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been let unattended. var_logind_session_timeout=10_minutes
R33 CCE-80737-0 Ensure auditd Collects Information on the Use of Privileged Commands - sudo At a minimum, the audit system should collect the execution of privileged commands for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add a line of the following form to a file with suffix .rules in the directory /etc/audit/rules.d: 
-a always,exit -F path=/usr/bin/sudo -F perm=x -F auid>=1000 -F auid!=unset -F key=privileged
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add a line of the following form to /etc/audit/audit.rules: 
-a always,exit -F path=/usr/bin/sudo -F perm=x -F auid>=1000 -F auid!=unset -F key=privileged
 Misuse of privileged functions, either intentionally or unintentionally by authorized users, or by unauthorized external entities that have compromised system accounts, is a serious and ongoing concern and can have significant adverse impacts on organizations. Auditing the use of privileged functions is one way to detect such misuse and identify the risk from insider and advanced persistent threats.

Privileged programs are subject to escalation-of-privilege attacks, which attempt to subvert their normal role of providing some necessary but limited capability. As such, motivation exists to monitor these programs for unusual activity.
R33 CCE-80840-2 Direct root Logins Not Allowed To further limit access to the root account, administrators can disable root logins at the console by editing the /etc/securetty file. This file lists all devices the root user is allowed to login to. If the file does not exist at all, the root user can login through any communication device on the system, whether via the console or via a raw network interface. This is dangerous as user can login to the system as root via Telnet, which sends the password in plain text over the network. By default, Red Hat Enterprise Linux 8's /etc/securetty file only allows the root user to login at the console physically attached to the system. To prevent root from logging in, remove the contents of this file. To prevent direct root logins, remove the contents of this file by typing the following command: 
$ sudo echo > /etc/securetty
Disabling direct root logins ensures proper accountability and multifactor authentication to privileged accounts. Users will first login, then escalate to privileged (root) access via su / sudo. This is required for FISMA Low and FISMA Moderate systems.
R33
R73		 CCE-81043-2 Ensure the audit Subsystem is Installed The audit package should be installed. The auditd service is an access monitoring and accounting daemon, watching system calls to audit any access, in comparison with potential local access control policy such as SELinux policy.
R33 CCE-82214-8 Install sudo Package The sudo package can be installed with the following command: 
$ sudo yum install sudo
 sudo is a program designed to allow a system administrator to give limited root privileges to users and log root activity. The basic philosophy is to give as few privileges as possible but still allow system users to get their work done.
R33
R73		 CCE-80872-5 Enable auditd Service The auditd service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The auditd service can be enabled with the following command: 
$ sudo systemctl enable auditd.service
 Without establishing what type of events occurred, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack. Ensuring the auditd service is active ensures audit records generated by the kernel are appropriately recorded.

Additionally, a properly configured audit subsystem ensures that actions of individual system users can be uniquely traced to those users so they can be held accountable for their actions.
R33 CCE-80901-2 Disable SSH Root Login The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in /etc/ssh/sshd_config: 
PermitRootLogin no
 Even though the communications channel may be encrypted, an additional layer of security is gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account provides individual accountability of actions performed on the system and also helps to minimize direct attack attempts on root's password.
R37
R79		 CCE-80869-1 Ensure SELinux State is Enforcing The SELinux state should be set to enforcing at system boot time. In the file /etc/selinux/config, add or correct the following line to configure the system to boot into enforcing mode: 
SELINUX=enforcing
 Setting the SELinux state to enforcing ensures SELinux is able to confine potentially compromised processes to the security policy, which is designed to prevent them from causing damage to the system or further elevating their privileges. var_selinux_state=enforcing
R39 CCE-83820-1 Ensure sudo Runs In A Minimal Environment - sudo env_reset The sudo env_reset tag, when specified, will run the command in a minimal environment, containing the TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER and SUDO_* variables. On Red Hat Enterprise Linux 8, env_reset is enabled by default This should be enabled by making sure that the env_reset tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/. Forcing sudo to reset the environment ensures that environment variables are not passed on to the command accidentaly, preventing leak of potentially sensitive information.
R39 CCE-83810-2 Ensure sudo Ignores Commands In Current Dir - sudo ignore_dot The sudo ignore_dot tag, when specified, will ignore the current directory in the PATH environment variable. On Red Hat Enterprise Linux 8, ignore_dot is enabled by default This should be enabled by making sure that the ignore_dot tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/. Ignoring the commands in the user's current directory prevents an attacker from executing commands downloaded locally.
R39 CCE-83747-6 Ensure Privileged Escalated Commands Cannot Execute Other Commands - sudo NOEXEC The sudo NOEXEC tag, when specified, prevents user executed commands from executing other commands, like a shell for example. This should be enabled by making sure that the NOEXEC tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/. Restricting the capability of sudo allowed commands to execute sub-commands prevents users from running programs with privileges they wouldn't have otherwise.
R39 CCE-83790-6 Ensure Only Users Logged In To Real tty Can Execute Sudo - sudo requiretty The sudo requiretty tag, when specified, will only execute sudo commands from users logged in to a real tty. This should be enabled by making sure that the requiretty tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/. Restricting the use cases in which a user is allowed to execute sudo commands reduces the attack surface.
R39 CCE-83860-7 Ensure sudo umask is appropriate - sudo umask The sudo umask tag, when specified, will be added the to the user's umask in the command environment. On Red Hat Enterprise Linux 8, the default umask value is 0022. The umask should be configured by making sure that the umask=0077 tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/. The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users. var_sudo_umask=0077
R39 CCE-83798-9 Ensure Only Users Logged In To Real tty Can Execute Sudo - sudo use_pty The sudo use_pty tag, when specified, will only execute sudo commands from users logged in to a real tty. This should be enabled by making sure that the use_pty tag exists in /etc/sudoers configuration file or any sudo configuration snippets in /etc/sudoers.d/. Requiring that sudo commands be run in a pseudo-terminal can prevent an attacker from retaining access to the user's terminal after the main program has finished executing.
R40 CCE-83598-3 Don't target root user in the sudoers file The targeted users of a user specification should be, as much as possible, non privileged users (i.e.: non-root). User specifications have to explicitly list the runas spec (i.e. the list of target users that can be impersonated), and ALL or root should not be used. It is common that the command to be executed does not require superuser rights (editing a file whose the owner is not root, sending a signal to an unprivileged process,etc.). In order to limit any attempt of privilege escalation through a command, it is better to apply normal user rights.
R42 CCE-83518-1 Don't define allowed commands in sudoers by means of exclusion Policies applied by sudo through the sudoers file should not involve negation. Each user specification in the sudoers file contains a comma-delimited list of command specifications. The definition can make use glob patterns, as well as of negations. Indirect definition of those commands by means of exclusion of a set of commands is trivial to bypass, so it is not allowed to use such constructs. Specifying access right using negation is inefficient and can be easily circumvented. For example, it is expected that a specification like 
# To avoid absolutely , this rule can be easily circumvented!
user ALL = ALL ,!/ bin/sh
prevents the execution of the shell but that’s not the case: just copy the binary /bin/sh to a different name to make it executable again through the rule keyword ALL.
R43 CCE-83632-0 Explicit arguments in sudo specifications All commands in the sudoers file must strictly specify the arguments allowed to be used for a given user. If the command is supposed to be executed only without arguments, pass "" as an argument in the corresponding user specification. Any argument can modify quite significantly the behavior of a program, whether regarding the realized operation (read, write, delete, etc.) or accessed resources (path in a file system tree). To avoid any possibility of misuse of a command by a user, the ambiguities must be removed at the level of its specification. For example, on some systems, the kernel messages are only accessible by root. If a user nevertheless must have the privileges to read them, the argument of the dmesg command has to be restricted in order to prevent the user from flushing the buffer through the -c option: 
user ALL = dmesg ""
R50 CCE-86314-2 User Initialization Files Must Be Group-Owned By The Primary Group Change the group owner of interactive users files to the group found in 
/etc/passwd
for the user. To change the group owner of a local interactive user home directory, use the following command: 
$ sudo chgrp USER_GROUP /home/USER/.INIT_FILE
This rule ensures every initialization file related to an interactive user is group-owned by an interactive user. 		Local initialization files for interactive users are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.
R50 CCE-86316-7 User Initialization Files Must Be Owned By the Primary User Set the owner of the user initialization files for interactive users to the primary owner with the following command: 
$ sudo chown USER /home/USER/.*
This rule ensures every initialization file related to an interactive user is owned by an interactive user. 		Local initialization files are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.
R50 CCE-86534-5 All User Files and Directories In The Home Directory Must Be Group-Owned By The Primary Group Change the group of a local interactive users files and directories to a group that the interactive user is a member of. To change the group owner of a local interactive users files and directories, use the following command: 
$ sudo chgrp USER_GROUP /home/USER/FILE_DIR
This rule ensures every file or directory under the home directory related to an interactive user is group-owned by an interactive user. 		If a local interactive users files are group-owned by a group of which the user is not a member, unintended users may be able to access them.
R50 CCE-87040-2 All User Files and Directories In The Home Directory Must Have a Valid Owner Either remove all files and directories from the system that do not have a valid user, or assign a valid user to all unowned files and directories. To assign a valid owner to a local interactive user's files and directories, use the following command: 
$ sudo chown -R USER /home/USER
This rule ensures every file or directory under the home directory related to an interactive user is owned by an interactive user. 		If local interactive users do not own the files in their directories, unauthorized users may be able to access them. Additionally, if files are not owned by the user, this could be an indication of system compromise.
R50 CCE-85888-6 All User Files and Directories In The Home Directory Must Have Mode 0750 Or Less Permissive Set the mode on files and directories in the local interactive user home directory with the following command: 
$ sudo chmod 0750 /home/USER/FILE_DIR
Files that begin with a "." are excluded from this requirement. 		If a local interactive user files have excessive permissions, unintended users may be able to access or modify them.
R50 CCE-87022-0 Verify that system commands directories have root as a group owner System commands are stored in the following directories: by default: 
/bin 
/sbin 
/usr/bin 
/usr/sbin 
/usr/local/bin 
/usr/local/sbin
All these directories should have root user as a group owner. If any system command directory is not group owned by a user other than root correct its ownership with the following command: 
$ sudo chgrp root DIR
 If the operating system were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process. This requirement applies to operating systems with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs which execute with escalated privileges. Only qualified and authorized individuals must be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications.
R50 CCE-87028-7 Verify that system commands directories have root ownership System commands are stored in the following directories by default: 
/bin 
/sbin 
/usr/bin 
/usr/sbin 
/usr/local/bin 
/usr/local/sbin
All these directories should be owned by the root user. If any system command directory is not owned by a user other than root correct its ownership with the following command: 
$ sudo chown root DIR
 If the operating system were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process. This requirement applies to operating systems with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs which execute with escalated privileges. Only qualified and authorized individuals must be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications.
R50 CCE-86438-9 Verify Group Who Owns /etc/ipsec.d Directory To properly set the group owner of /etc/ipsec.d, run the command: 
$ sudo chgrp root /etc/ipsec.d
 The ownership of the /etc/ipsec.d directory by the root group is important because this directory hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.
R50 CCE-86426-4 Verify Group Who Owns /etc/iptables Directory To properly set the group owner of /etc/iptables, run the command: 
$ sudo chgrp root /etc/iptables
 The ownership of the /etc/iptables directory by the root group is important because this directory hosts iptables configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the iptables configuration.
R50 CCE-86308-4 Verify Group Who Owns /etc/nftables Directory To properly set the group owner of /etc/nftables, run the command: 
$ sudo chgrp root /etc/nftables
 The ownership of the /etc/nftables directory by the root group is important because this directory hosts nftables configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the nftables configuration.
R50 CCE-86273-0 Verify Group Who Owns /etc/selinux Directory To properly set the group owner of /etc/selinux, run the command: 
$ sudo chgrp root /etc/selinux
 The ownership of the /etc/selinux directory by the root group is important because this directory hosts SELinux configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.
R50 CCE-86340-7 Verify Group Who Owns /etc/sudoers.d Directory To properly set the group owner of /etc/sudoers.d, run the command: 
$ sudo chgrp root /etc/sudoers.d
 The ownership of the /etc/sudoers.d directory by the root group is important because this directory hosts sudo configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.
R50 CCE-86324-1 Verify Group Who Owns /etc/sysctl.d Directory To properly set the group owner of /etc/sysctl.d, run the command: 
$ sudo chgrp root /etc/sysctl.d
 The ownership of the /etc/sysctl.d directory by the root group is important because this directory hosts kernel configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the kernel configuration.
R50 CCE-86302-7 Verify User Who Owns /etc/ipsec.d Directory To properly set the owner of /etc/ipsec.d, run the command: 
$ sudo chown root /etc/ipsec.d
The ownership of the /etc/ipsec.d directory by the root user is important because this directory hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.
R50 CCE-86429-8 Verify User Who Owns /etc/iptables Directory To properly set the owner of /etc/iptables, run the command: 
$ sudo chown root /etc/iptables
The ownership of the /etc/iptables directory by the root user is important because this directory hosts iptables configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the iptables configuration.
R50 CCE-86311-8 Verify User Who Owns /etc/nftables Directory To properly set the owner of /etc/nftables, run the command: 
$ sudo chown root /etc/nftables
The ownership of the /etc/nftables directory by the root user is important because this directory hosts nftables configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the nftables configuration.
R50 CCE-86270-6 Verify User Who Owns /etc/selinux Directory To properly set the owner of /etc/selinux, run the command: 
$ sudo chown root /etc/selinux
The ownership of the /etc/selinux directory by the root user is important because this directory hosts SELinux configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.
R50 CCE-86355-5 Verify User Who Owns /etc/sudoers.d Directory To properly set the owner of /etc/sudoers.d, run the command: 
$ sudo chown root /etc/sudoers.d
The ownership of the /etc/sudoers.d directory by the root user is important because this directory hosts sudo configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.
R50 CCE-86329-0 Verify User Who Owns /etc/sysctl.d Directory To properly set the owner of /etc/sysctl.d, run the command: 
$ sudo chown root /etc/sysctl.d
The ownership of the /etc/sysctl.d directory by the root user is important because this directory hosts kernel configuration. Protection of this directory is critical for system security. Assigning the ownership to root ensures exclusive control of the kernel configuration.
R50 CCE-86305-0 Verify Permissions On /etc/ipsec.d Directory To properly set the permissions of /etc/ipsec.d, run the command: 
$ sudo chmod 0700 /etc/ipsec.d
 Setting correct permissions on the /etc/ipsec.d directory is important because this directory hosts Libreswan configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the Libreswan configuration.
R50 CCE-86435-5 Verify Permissions On /etc/iptables Directory To properly set the permissions of /etc/iptables, run the command: 
$ sudo chmod 0700 /etc/iptables
 Setting correct permissions on the /etc/iptables directory is important because this directory hosts iptables configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the iptables configuration.
R50 CCE-86318-3 Verify Permissions On /etc/nftables Directory To properly set the permissions of /etc/nftables, run the command: 
$ sudo chmod 0700 /etc/nftables
 Setting correct permissions on the /etc/nftables directory is important because this directory hosts nftables configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the nftables configuration.
R50 CCE-86278-9 Verify Permissions On /etc/selinux Directory To properly set the permissions of /etc/selinux, run the command: 
$ sudo chmod 0755 /etc/selinux
 Setting correct permissions on the /etc/selinux directory is important because this directory hosts SELinux configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the SELinux configuration.
R50 CCE-86359-7 Verify Permissions On /etc/sudoers.d Directory To properly set the permissions of /etc/sudoers.d, run the command: 
$ sudo chmod 0750 /etc/sudoers.d
 Setting correct permissions on the /etc/sudoers.d directory is important because this directory hosts sudo configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the sudo configuration.
R50 CCE-86332-4 Verify Permissions On /etc/sysctl.d Directory To properly set the permissions of /etc/sysctl.d, run the command: 
$ sudo chmod 0755 /etc/sysctl.d
 Setting correct permissions on the /etc/sysctl.d directory is important because this directory hosts kernel configuration. Protection of this directory is critical for system security. Restricting the permissions ensures exclusive control of the kernel configuration.
R50 CCE-86373-8 Verify Group Who Owns /etc/chrony.keys File To properly set the group owner of /etc/chrony.keys, run the command: 
$ sudo chgrp chrony /etc/chrony.keys
 The ownership of the /etc/chrony.keys file by the chrony group is important because this file hosts chrony cryptographic keys. Protection of this file is critical for system security. Assigning the ownership to chrony ensures exclusive control of the chrony cryptography keys.
R50 CCE-86362-1 Verify Group Who Owns /etc/crypttab File To properly set the group owner of /etc/crypttab, run the command: 
$ sudo chgrp root /etc/crypttab
 The ownership of the /etc/crypttab file by the root group is important because this file hosts encrypted block devices configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the encrypted block devices configuration.
R50 CCE-80796-6 Verify Group Who Owns group File To properly set the group owner of /etc/group, run the command: 
$ sudo chgrp root /etc/group
 The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security.
R50 CCE-80797-4 Verify Group Who Owns gshadow File To properly set the group owner of /etc/gshadow, run the command: 
$ sudo chgrp root /etc/gshadow
 The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security.
R50 CCE-86386-0 Verify Group Who Owns /etc/ipsec.conf File To properly set the group owner of /etc/ipsec.conf, run the command: 
$ sudo chgrp root /etc/ipsec.conf
 The ownership of the /etc/ipsec.conf file by the root group is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.
R50 CCE-86397-7 Verify Group Who Owns /etc/ipsec.secrets File To properly set the group owner of /etc/ipsec.secrets, run the command: 
$ sudo chgrp root /etc/ipsec.secrets
 The ownership of the /etc/ipsec.secrets file by the root group is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.
R50 CCE-80798-2 Verify Group Who Owns passwd File To properly set the group owner of /etc/passwd, run the command: 
$ sudo chgrp root /etc/passwd
 The /etc/passwd file contains information about the users that are configured on the system. Protection of this file is critical for system security.
R50 CCE-86288-8 Verify Group Who Owns /etc/sestatus.conf File To properly set the group owner of /etc/sestatus.conf, run the command: 
$ sudo chgrp root /etc/sestatus.conf
 The ownership of the /etc/sestatus.conf file by the root group is important because this file hosts SELinux configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.
R50 CCE-80799-0 Verify Group Who Owns shadow File To properly set the group owner of /etc/shadow, run the command: 
$ sudo chgrp root /etc/shadow
 The /etc/shadow file stores password hashes. Protection of this file is critical for system security.
R50 CCE-87030-3 Verify Group Who Owns /etc/shells File To properly set the group owner of /etc/shells, run the command: 
$ sudo chgrp root /etc/shells
 The /etc/shells file contains the list of full pathnames to shells on the system. Since this file is used by many system programs this file should be protected.
R50 CCE-86413-2 Verify Group Who Owns /etc/sudoers File To properly set the group owner of /etc/sudoers, run the command: 
$ sudo chgrp root /etc/sudoers
 The ownership of the /etc/sudoers file by the root group is important because this file hosts sudo configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.
R50 CCE-82901-0 Verify Group Who Owns SSH Server config file To properly set the group owner of /etc/ssh/sshd_config, run the command: 
$ sudo chgrp root /etc/ssh/sshd_config
 Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
R50 CCE-86126-0 Verify Group Ownership on SSH Server Private *_key Key Files SSH server private keys, files that match the /etc/ssh/*_key glob, must be group-owned by ssh_keys group. If an unauthorized user obtains the private SSH host key file, the host could be impersonated.
R50 CCE-86133-6 Verify Group Ownership on SSH Server Public *.pub Key Files SSH server public keys, files that match the /etc/ssh/*.pub glob, must be group-owned by root group. If a public host key file is modified by an unauthorized user, the SSH service may be compromised.
R50 CCE-86519-6 Verify that system commands files are group owned by root or a system account System commands files are stored in the following directories by default: 
/bin
/sbin
/usr/bin
/usr/sbin
/usr/local/bin
/usr/local/sbin
All files in these directories should be owned by the root group, or a system account. If the directory, or any file in these directories, is found to be owned by a group other than root or a a system account correct its ownership with the following command: 
$ sudo chgrp root FILE
 If the operating system allows any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process. This requirement applies to operating systems with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs which execute with escalated privileges. Only qualified and authorized individuals must be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications.
R50 CCE-86379-5 Verify User Who Owns /etc/chrony.keys File To properly set the owner of /etc/chrony.keys, run the command: 
$ sudo chown root /etc/chrony.keys
The ownership of the /etc/chrony.keys file by the chrony user is important because this file hosts chrony cryptographic keys. Protection of this file is critical for system security. Assigning the ownership to chrony ensures exclusive control of the chrony cryptographic keys.
R50 CCE-86365-4 Verify User Who Owns /etc/crypttab File To properly set the owner of /etc/crypttab, run the command: 
$ sudo chown root /etc/crypttab
The ownership of the /etc/crypttab file by the root user is important because this file hosts encrypted block devices configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the encrypted block devices configuration.
R50 CCE-80801-4 Verify User Who Owns group File To properly set the owner of /etc/group, run the command: 
$ sudo chown root /etc/group
The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security.
R50 CCE-80802-2 Verify User Who Owns gshadow File To properly set the owner of /etc/gshadow, run the command: 
$ sudo chown root /etc/gshadow
The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security.
R50 CCE-86389-4 Verify User Who Owns /etc/ipsec.conf File To properly set the owner of /etc/ipsec.conf, run the command: 
$ sudo chown root /etc/ipsec.conf
The ownership of the /etc/ipsec.conf file by the root user is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.
R50 CCE-86400-9 Verify User Who Owns /etc/ipsec.secrets File To properly set the owner of /etc/ipsec.secrets, run the command: 
$ sudo chown root /etc/ipsec.secrets
The ownership of the /etc/ipsec.secrets file by the root user is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the Libreswan configuration.
R50 CCE-80803-0 Verify User Who Owns passwd File To properly set the owner of /etc/passwd, run the command: 
$ sudo chown root /etc/passwd
The /etc/passwd file contains information about the users that are configured on the system. Protection of this file is critical for system security.
R50 CCE-86285-4 Verify User Who Owns /etc/sestatus.conf File To properly set the owner of /etc/sestatus.conf, run the command: 
$ sudo chown root /etc/sestatus.conf
The ownership of the /etc/sestatus.conf file by the root user is important because this file hosts SELinux configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the SELinux configuration.
R50 CCE-80804-8 Verify User Who Owns shadow File To properly set the owner of /etc/shadow, run the command: 
$ sudo chown root /etc/shadow
The /etc/shadow file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.
R50 CCE-87055-0 Verify Who Owns /etc/shells File To properly set the owner of /etc/shells, run the command: 
$ sudo chown root /etc/shells
The /etc/shells file contains the list of full pathnames to shells on the system. Since this file is used by many system programs this file should be protected.
R50 CCE-86416-5 Verify User Who Owns /etc/sudoers File To properly set the owner of /etc/sudoers, run the command: 
$ sudo chown root /etc/sudoers
The ownership of the /etc/sudoers file by the root user is important because this file hosts sudo configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the sudo configuration.
R50 CCE-82898-8 Verify Owner on SSH Server config file To properly set the owner of /etc/ssh/sshd_config, run the command: 
$ sudo chown root /etc/ssh/sshd_config
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
R50 CCE-80806-3 Verify that System Executables Have Root Ownership System executables are stored in the following directories by default: 
/bin
/sbin
/usr/bin
/usr/libexec
/usr/local/bin
/usr/local/sbin
/usr/sbin
All files in these directories should be owned by the root user. If any file FILE in these directories is found to be owned by a user other than root, correct its ownership with the following command: 
$ sudo chown root FILE
 System binaries are executed by privileged users as well as system services, and restrictive permissions are necessary to ensure that their execution of these programs cannot be co-opted.
R50 CCE-86118-7 Verify Ownership on SSH Server Private *_key Key Files SSH server private keys, files that match the /etc/ssh/*_key glob, must be owned by root user. If an unauthorized user obtains the private SSH host key file, the host could be impersonated.
R50 CCE-86129-4 Verify Ownership on SSH Server Public *.pub Key Files SSH server public keys, files that match the /etc/ssh/*.pub glob, must be owned by root user. If a public host key file is modified by an unauthorized user, the SSH service may be compromised.
R50 CCE-84043-9 Ensure All User Initialization Files Have Mode 0740 Or Less Permissive Set the mode of the user initialization files to 0740 with the following command: 
$ sudo chmod 0740 /home/USER/.INIT_FILE
 Local initialization files are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.
R50 CCE-80809-7 Verify that System Executables Have Restrictive Permissions System executables are stored in the following directories by default: 
/bin
/sbin
/usr/bin
/usr/libexec
/usr/local/bin
/usr/local/sbin
/usr/sbin
All files in these directories should not be group-writable or world-writable. If any file FILE in these directories is found to be group-writable or world-writable, correct its permission with the following command: 
$ sudo chmod go-w FILE
 System binaries are executed by privileged users, as well as system services, and restrictive permissions are necessary to ensure execution of these programs cannot be co-opted.
R50 CCE-86383-7 Verify Permissions On /etc/chrony.keys File To properly set the permissions of /etc/chrony.keys, run the command: 
$ sudo chmod 0640 /etc/chrony.keys
 Setting correct permissions on the /etc/chrony.keys file is important because this file hosts chrony cryptographic keys. Protection of this file is critical for system security. Assigning the correct mode ensures exclusive control of the chrony cryptographic keys.
R50 CCE-86369-6 Verify Permissions On /etc/crypttab File To properly set the permissions of /etc/crypttab, run the command: 
$ sudo chmod 0600 /etc/crypttab
 Setting correct permissions on the /etc/crypttab file is important because this file hosts encrypted block devices configuration. Protection of this file is critical for system security. Assigning the ownership to root ensures exclusive control of the encrypted block devices configuration.
R50 CCE-80810-5 Verify Permissions on group File To properly set the permissions of /etc/group, run the command: 
$ sudo chmod 0644 /etc/group
 The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security.
R50 CCE-80811-3 Verify Permissions on gshadow File To properly set the permissions of /etc/gshadow, run the command: 
$ sudo chmod 0000 /etc/gshadow
 The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security.
R50 CCE-86393-6 Verify Permissions On /etc/ipsec.conf File To properly set the permissions of /etc/ipsec.conf, run the command: 
$ sudo chmod 0644 /etc/ipsec.conf
 Setting correct permissions on the /etc/ipsec.conf file is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the Libreswan configuration.
R50 CCE-86410-8 Verify Permissions On /etc/ipsec.secrets File To properly set the permissions of /etc/ipsec.secrets, run the command: 
$ sudo chmod 0644 /etc/ipsec.secrets
 Setting correct permissions on the /etc/ipsec.secrets file is important because this file hosts Libreswan configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the Libreswan configuration.
R50 CCE-80812-1 Verify Permissions on passwd File To properly set the permissions of /etc/passwd, run the command: 
$ sudo chmod 0644 /etc/passwd
 If the /etc/passwd file is writable by a group-owner or the world the risk of its compromise is increased. The file contains the list of accounts on the system and associated information, and protection of this file is critical for system security.
R50 CCE-86291-2 Verify Permissions On /etc/sestatus.conf File To properly set the permissions of /etc/sestatus.conf, run the command: 
$ sudo chmod 0644 /etc/sestatus.conf
 Setting correct permissions on the /etc/sestatus.conf file is important because this file hosts SELinux configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the SELinux configuration.
R50 CCE-80813-9 Verify Permissions on shadow File To properly set the permissions of /etc/shadow, run the command: 
$ sudo chmod 0000 /etc/shadow
 The /etc/shadow file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.
R50 CCE-86634-3 Verify Permissions on /etc/shells File To properly set the permissions of /etc/shells, run the command: 
$ sudo chmod 0644 /etc/shells
 The /etc/shells file contains the list of full pathnames to shells on the system. Since this file is used by many system programs this file should be protected.
R50 CCE-86419-9 Verify Permissions On /etc/sudoers File To properly set the permissions of /etc/sudoers, run the command: 
$ sudo chmod 0440 /etc/sudoers
 Setting correct permissions on the /etc/sudoers file is important because this file hosts sudo configuration. Protection of this file is critical for system security. Restricting the permissions ensures exclusive control of the sudo configuration.
R50 CCE-82894-7 Verify Permissions on SSH Server config file To properly set the permissions of /etc/ssh/sshd_config, run the command: 
$ sudo chmod 0600 /etc/ssh/sshd_config
 Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
R50 CCE-82424-3 Verify Permissions on SSH Server Private *_key Key Files SSH server private keys - files that match the /etc/ssh/*_key glob, have to have restricted permissions. If those files are owned by the root user and the root group, they have to have the 0600 permission or stricter. If they are owned by the root user, but by a dedicated group ssh_keys, they can have the 0640 permission or stricter. If an unauthorized user obtains the private SSH host key file, the host could be impersonated.
R50 CCE-82428-4 Verify Permissions on SSH Server Public *.pub Key Files To properly set the permissions of /etc/ssh/*.pub, run the command: 
$ sudo chmod 0644 /etc/ssh/*.pub
 If a public host key file is modified by an unauthorized user, the SSH service may be compromised.
R53 CCE-83497-8 Ensure All Files Are Owned by a Group If any file is not group-owned by a group present in /etc/group, the cause of the lack of group-ownership must be investigated. Following this, those files should be deleted or assigned to an appropriate group. Locate the mount points related to local devices by the following command: 
$ findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,)
For all mount points listed by the previous command, it is necessary to search for files which do not belong to a valid group using the following command: 
$ sudo find MOUNTPOINT -xdev -nogroup 2>/dev/null
 Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account, or other similar cases. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.
R53 CCE-83499-4 Ensure All Files Are Owned by a User If any files are not owned by a user, then the cause of their lack of ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate user. Locate the mount points related to local devices by the following command: 
$ findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,)
For all mount points listed by the previous command, it is necessary to search for files which do not belong to a valid user using the following command: 
$ sudo find MOUNTPOINT -xdev -nouser 2>/dev/null
 Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account, or other similar cases. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.
R54 CCE-83375-6 Ensure All World-Writable Directories Are Owned by root User All directories in local partitions which are world-writable should be owned by root. If any world-writable directories are not owned by root, this should be investigated. Following this, the files should be deleted or assigned to root user. Allowing a user account to own a world-writable directory is undesirable because it allows the owner of that directory to remove or replace any files that may be placed in the directory by other users.
R54 CCE-80783-4 Verify that All World-Writable Directories Have Sticky Bits Set When the so-called 'sticky bit' is set on a directory, only the owner of a given file may remove that file from the directory. Without the sticky bit, any user with write access to a directory may remove any file in the directory. Setting the sticky bit prevents users from removing each other's files. In cases where there is no reason for a directory to be world-writable, a better solution is to remove that permission rather than to set the sticky bit. However, if a directory is used by a particular application, consult that application's documentation instead of blindly changing modes.
To set the sticky bit on a world-writable directory DIR, run the following command: 
$ sudo chmod +t DIR
 Failing to set the sticky bit on public directories allows unauthorized users to delete files in the directory structure.

The only authorized public directories are those temporary directories supplied with the system, or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system, by users for temporary file storage (such as /tmp), and for directories requiring global read/write access.
R54 CCE-80818-8 Ensure No World-Writable Files Exist It is generally a good idea to remove global (other) write access to a file when it is discovered. However, check with documentation for specific applications before making changes. Also, monitor for recurring world-writable files, as these may be symptoms of a misconfigured application or user account. Finally, this applies to real files and not virtual files that are a part of pseudo file systems such as sysfs or procfs. Data in world-writable files can be modified by any user on the system. In almost all circumstances, files can be configured using a combination of user and group permissions to support whatever legitimate access is needed without the risk caused by world-writable files.
R55 CCE-83732-8 Configure Polyinstantiation of /tmp Directories To configure polyinstantiated /tmp directories, first create the parent directories which will hold the polyinstantiation child directories. Use the following command: 
$ sudo mkdir --mode 000 /tmp/tmp-inst
Then, add the following entry to /etc/security/namespace.conf: 
/tmp     /tmp/tmp-inst/            level      root,adm
 Polyinstantiation of temporary directories is a proactive security measure which reduces chances of attacks that are made possible by /tmp directories being world-writable.
R55 CCE-83778-1 Configure Polyinstantiation of /var/tmp Directories To configure polyinstantiated /tmp directories, first create the parent directories which will hold the polyinstantiation child directories. Use the following command: 
$ sudo mkdir --mode 000 /var/tmp/tmp-inst
Then, add the following entry to /etc/security/namespace.conf: 
/var/tmp /var/tmp/tmp-inst/    level      root,adm
 Polyinstantiation of temporary directories is a proactive security measure which reduces chances of attacks that are made possible by /var/tmp directories being world-writable.
R55 CCE-83744-3 Set Up a Private Namespace in PAM Configuration To setup a private namespace add the following line to /etc/pam.d/login: 
session    required     pam_namespace.so
 The pam_namespace PAM module sets up a private namespace for a session with polyinstantiated directories. A polyinstantiated directory provides a different instance of itself based on user name, or when using SELinux, user name, security context or both. The polyinstatied directories can be used to dedicate separate temporary directories to each account.
R55 CCE-84230-2 Configure the polyinstantiation_enabled SELinux Boolean By default, the SELinux boolean polyinstantiation_enabled is disabled. This setting should be configured to on.
To set the polyinstantiation_enabled SELinux boolean, run the following command: 
$ sudo setsebool -P polyinstantiation_enabled on
 var_polyinstantiation_enabled=on
R56 CCE-80816-2 Ensure All SGID Executables Are Authorized The SGID (set group id) bit should be set only on files that were installed via authorized means. A straightforward means of identifying unauthorized SGID files is determine if any were not installed as part of an RPM package, which is cryptographically verified. Investigate the origin of any unpackaged SGID files. This configuration check considers authorized SGID files those which were installed via RPM. It is assumed that when an individual has sudo access to install an RPM and all packages are signed with an organizationally-recognized GPG key, the software should be considered an approved package on the system. Any SGID file not deployed through an RPM will be flagged for further review. Executable files with the SGID permission run with the privileges of the owner of the file. SGID files of uncertain provenance could allow for unprivileged users to elevate privileges. The presence of these files should be strictly controlled on the system.
R56 CCE-80817-0 Ensure All SUID Executables Are Authorized The SUID (set user id) bit should be set only on files that were installed via authorized means. A straightforward means of identifying unauthorized SUID files is determine if any were not installed as part of an RPM package, which is cryptographically verified. Investigate the origin of any unpackaged SUID files. This configuration check considers authorized SUID files those which were installed via RPM. It is assumed that when an individual has sudo access to install an RPM and all packages are signed with an organizationally-recognized GPG key, the software should be considered an approved package on the system. Any SUID file not deployed through an RPM will be flagged for further review. Executable files with the SUID permission run with the privileges of the owner of the file. SUID files of uncertain provenance could allow for unprivileged users to elevate privileges. The presence of these files should be strictly controlled on the system.
R59 CCE-80790-9 Ensure gpgcheck Enabled In Main yum Configuration The gpgcheck option controls whether RPM packages' signatures are always checked prior to installation. To configure yum to check package signatures before installing them, ensure the following line appears in /etc/yum.conf in the [main] section: 
gpgcheck=1
 Changes to any software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor.
Accordingly, patches, service packs, device drivers, or operating system components must be signed with a certificate recognized and approved by the organization.
Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA).
R59 CCE-80791-7 Ensure gpgcheck Enabled for Local Packages yum should be configured to verify the signature(s) of local packages prior to installation. To configure yum to verify signatures of local packages, set the localpkg_gpgcheck to 1 in /etc/yum.conf. Changes to any software components can have significant effects to the overall security of the operating system. This requirement ensures the software has not been tampered and has been provided by a trusted vendor.

Accordingly, patches, service packs, device drivers, or operating system components must be signed with a certificate recognized and approved by the organization.
R59 CCE-80792-5 Ensure gpgcheck Enabled for All yum Package Repositories To ensure signature checking is not disabled for any repos, remove any lines from files in /etc/yum.repos.d of the form: 
gpgcheck=0
 Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA)."
R59 CCE-80795-8 Ensure Red Hat GPG Key Installed To ensure the system can cryptographically verify base software packages come from Red Hat (and to connect to the Red Hat Network to receive them), the Red Hat GPG key must properly be installed. To install the Red Hat GPG key, run: 
$ sudo subscription-manager register
If the system is not connected to the Internet or an RHN Satellite, then install the Red Hat GPG key from trusted media such as the Red Hat installation CD-ROM or DVD. Assuming the disc is mounted in /media/cdrom, use the following command as the root user to import it into the keyring: 
$ sudo rpm --import /media/cdrom/RPM-GPG-KEY
Alternatively, the key may be pre-loaded during the RHEL installation. In such cases, the key can be installed by running the following command: 
sudo rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
 Changes to software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor. The Red Hat GPG key is necessary to cryptographically verify packages are from Red Hat.
R61 CCE-82494-6 Configure dnf-automatic to Install Available Updates Automatically To ensure that the packages comprising the available updates will be automatically installed by dnf-automatic, set apply_updates to yes under [commands] section in /etc/dnf/automatic.conf. Installing software updates is a fundamental mitigation against the exploitation of publicly-known vulnerabilities. If the most recent security patches and updates are not installed, unauthorized users may take advantage of weaknesses in the unpatched software. The lack of prompt attention to patching could result in a system compromise. The automated installation of updates ensures that recent security patches are applied in a timely manner.
R61 CCE-82267-6 Configure dnf-automatic to Install Only Security Updates To configure dnf-automatic to install only security updates automatically, set upgrade_type to security under [commands] section in /etc/dnf/automatic.conf. By default, dnf-automatic installs all available updates. Reducing the amount of updated packages only to updates that were issued as a part of a security advisory increases the system stability.
R61 CCE-82985-3 Install dnf-automatic Package The dnf-automatic package can be installed with the following command: 
$ sudo yum install dnf-automatic
 dnf-automatic is an alternative command line interface (CLI) to dnf upgrade suitable for automatic, regular execution.
R61 CCE-80865-9 Ensure Software Patches Installed If the system is joined to the Red Hat Network, a Red Hat Satellite Server, or a yum server, run the following command to install updates: 
$ sudo yum update
If the system is not configured to use one of these sources, updates (in the form of RPM packages) can be manually downloaded from the Red Hat Network and installed using rpm.

NOTE: U.S. Defense systems are required to be patched within 30 days or sooner as local policy dictates. 		Installing software updates is a fundamental mitigation against the exploitation of publicly-known vulnerabilities. If the most recent security patches and updates are not installed, unauthorized users may take advantage of weaknesses in the unpatched software. The lack of prompt attention to patching could result in a system compromise.
R61 CCE-82360-9 Enable dnf-automatic Timer The dnf-automatic timer can be enabled with the following command: 
$ sudo systemctl enable dnf-automatic.timer
 The dnf-automatic is an alternative command line interface (CLI) to dnf upgrade with specific facilities to make it suitable to be executed automatically and regularly from systemd timers, cron jobs and similar. The tool is controlled by dnf-automatic.timer SystemD timer.
R62 CCE-83385-5 Uninstall DHCP Server Package If the system does not need to act as a DHCP server, the dhcp package can be uninstalled. The dhcp-server package can be removed with the following command: 
$ sudo yum erase dhcp-server
 Removing the DHCP server ensures that it cannot be easily or accidentally reactivated and disrupt network operation.
R62 CCE-82184-3 Uninstall rsh-server Package The rsh-server package can be removed with the following command: 
$ sudo yum erase rsh-server
 The rsh-server service provides unencrypted remote access service which does not provide for the confidentiality and integrity of user passwords or the remote session and has very weak authentication. If a privileged user were to login using this service, the privileged user password could be compromised. The rsh-server package provides several obsolete and insecure network services. Removing it decreases the risk of those services' accidental (or intentional) activation.
R62 CCE-82183-5 Uninstall rsh Package The rsh package contains the client commands for the rsh services These legacy clients contain numerous security exposures and have been replaced with the more secure SSH package. Even if the server is removed, it is best to ensure the clients are also removed to prevent users from inadvertently attempting to use these commands and therefore exposing their credentials. Note that removing the rsh package removes the clients for rsh,rcp, and rlogin.
R62 CCE-81039-0 Uninstall Sendmail Package Sendmail is not the default mail transfer agent and is not installed by default. The sendmail package can be removed with the following command: 
$ sudo yum erase sendmail
 The sendmail software was not developed with security in mind and its design prevents it from being effectively contained by SELinux. Postfix should be used instead.
R62 CCE-82180-1 Uninstall talk-server Package The talk-server package can be removed with the following command: 
 $ sudo yum erase talk-server
 The talk software presents a security risk as it uses unencrypted protocols for communications. Removing the talk-server package decreases the risk of the accidental (or intentional) activation of talk services.
R62 CCE-80848-5 Uninstall talk Package The talk package contains the client program for the Internet talk protocol, which allows the user to chat with other users on different systems. Talk is a communication program which copies lines from one terminal to the terminal of another user. The talk package can be removed with the following command: 
$ sudo yum erase talk
 The talk software presents a security risk as it uses unencrypted protocols for communications. Removing the talk package decreases the risk of the accidental (or intentional) activation of talk client program.
R62 CCE-82182-7 Uninstall telnet-server Package The telnet-server package can be removed with the following command: 
$ sudo yum erase telnet-server
 It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities are often overlooked and therefore may remain unsecure. They increase the risk to the platform by providing additional attack vectors.
The telnet service provides an unencrypted remote access service which does not provide for the confidentiality and integrity of user passwords or the remote session. If a privileged user were to login using this service, the privileged user password could be compromised.
Removing the telnet-server package decreases the risk of the telnet service's accidental (or intentional) activation.
R62 CCE-80849-3 Remove telnet Clients The telnet client allows users to start connections to other systems via the telnet protocol. The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal credentials. The ssh package provides an encrypted session and stronger security and is included in Red Hat Enterprise Linux 8.
R62 CCE-82436-7 Uninstall tftp-server Package The tftp-server package can be removed with the following command: 
 $ sudo yum erase tftp-server
 Removing the tftp-server package decreases the risk of the accidental (or intentional) activation of tftp services.

If TFTP is required for operational support (such as transmission of router configurations), its use must be documented with the Information Systems Securty Manager (ISSM), restricted to only authorized personnel, and have access control rules established.
R62 CCE-83590-0 Remove tftp Daemon Trivial File Transfer Protocol (TFTP) is a simple file transfer protocol, typically used to automatically transfer configuration or boot files between systems. TFTP does not support authentication and can be easily hacked. The package tftp is a client program that allows for connections to a tftp server. It is recommended that TFTP be removed, unless there is a specific need for TFTP (such as a boot server). In that case, use extreme caution when configuring the services.
R62 CCE-80850-1 Uninstall xinetd Package The xinetd package can be removed with the following command: 
$ sudo yum erase xinetd
 Removing the xinetd package decreases the risk of the xinetd service's accidental (or intentional) activation.
R62 CCE-82181-9 Remove NIS Client The Network Information Service (NIS), formerly known as Yellow Pages, is a client-server directory service protocol used to distribute system configuration files. The NIS client (ypbind) was used to bind a system to an NIS server and receive the distributed configuration files. The NIS service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor authentication for querying NIS maps. NIS generally has been replaced by such protocols as Lightweight Directory Access Protocol (LDAP). It is recommended that the service be removed.
R62 CCE-82432-6 Uninstall ypserv Package The ypserv package can be removed with the following command: 
$ sudo yum erase ypserv
 The NIS service provides an unencrypted authentication service which does not provide for the confidentiality and integrity of user passwords or the remote session. Removing the ypserv package decreases the risk of the accidental (or intentional) activation of NIS or NIS+ services.
R67 CCE-82416-9 Configure LDAP Client to Use TLS For All Transactions This check verifies cryptography has been implemented to protect the integrity of remote LDAP authentication sessions.

To determine if LDAP is being used for authentication, use the following command: 
$ sudo grep -i useldapauth /etc/sysconfig/authconfig


If USELDAPAUTH=yes, then LDAP is being used. To check if LDAP is configured to use TLS, use the following command: 
$ sudo grep -i ssl /etc/pam_ldap.conf
 Without cryptographic integrity protections, information can be altered by unauthorized users without detection. The ssl directive specifies whether to use TLS or not. If not specified it will default to no. It should be set to start_tls rather than doing LDAP over SSL.
R67 CCE-82417-7 Configure Certificate Directives for LDAP Use of TLS Ensure a copy of a trusted CA certificate has been placed in the file /etc/pki/tls/CA/cacert.pem. Configure LDAP to enforce TLS use and to trust certificates signed by that CA. First, edit the file /etc/nslcd.conf, and add or correct either of the following lines: 
tls_cacertdir /etc/pki/tls/CA
or 
tls_cacertfile /etc/pki/tls/CA/cacert.pem
Then review the LDAP server and ensure TLS has been configured. 		The tls_cacertdir or tls_cacertfile directives are required when tls_checkpeer is configured (which is the default for openldap versions 2.1 and up). These directives define the path to the trust certificates signed by the site CA.
R67 CCE-82444-1 Install the SSSD Package The sssd package should be installed. The sssd package can be installed with the following command: 
$ sudo yum install sssd
R67 CCE-82440-9 Enable the SSSD Service The SSSD service should be enabled. The sssd service can be enabled with the following command: 
$ sudo systemctl enable sssd.service
R67 CCE-82446-6 Configure PAM in SSSD Services SSSD should be configured to run SSSD pam services. To configure SSSD to known SSH hosts, add pam to services under the [sssd] section in /etc/sssd/sssd.conf. For example: 
[sssd]
services = sudo, autofs, pam
Using an authentication device, such as a CAC or token that is separate from the information system, ensures that even if the information system is compromised, that compromise will not affect credentials stored on the authentication device.
R67 CCE-84062-9 Configure SSSD LDAP Backend Client to Demand a Valid Certificate from the Server Configure SSSD to demand a valid certificate from the server to protect the integrity of LDAP remote access sessions by setting the 
ldap_tls_reqcert
option in 
/etc/sssd/sssd.conf
to demand. 		Without a valid certificate presented to the LDAP client backend, the identity of a server can be forged compromising LDAP remote access sessions.
R67 CCE-82437-5 Configure SSSD LDAP Backend to Use TLS For All Transactions The LDAP client should be configured to implement TLS for the integrity of all remote LDAP authentication sessions. If the id_provider is set to ldap or ipa in /etc/sssd/sssd.conf or any of the /etc/sssd/sssd.conf.d configuration files, ldap_id_use_start_tls must be set to true.

To check if LDAP is configured to use TLS when id_provider is set to ldap or ipa, use the following command: 
$ sudo grep -i ldap_id_use_start_tls /etc/sssd/sssd.conf /etc/sssd/conf.d/*.conf
 Without cryptographic integrity protections, information can be altered by unauthorized users without detection. The ssl directive specifies whether to use TLS or not. If not specified it will default to no. It should be set to start_tls rather than doing LDAP over SSL.
R68 CCE-82046-4 Ensure PAM Enforces Password Requirements - Minimum Different Categories The pam_pwquality module's minclass parameter controls requirements for usage of different character classes, or types, of character that must exist in a password before it is considered valid. For example, setting this value to three (3) requires that any password must have characters from at least three different categories in order to be approved. The default value is zero (0), meaning there are no required classes. There are four categories available: 
* Upper-case characters
* Lower-case characters
* Digits
* Special characters (for example, punctuation)
Modify the minclass setting in /etc/security/pwquality.conf entry to require 4 differing categories of characters when changing passwords. 		Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

Requiring a minimum number of character categories makes password guessing attacks more difficult by ensuring a larger search space. 		var_password_pam_minclass=4
R68 CCE-80664-6 Ensure PAM Enforces Password Requirements - Authentication Retry Prompts Permitted Per-Session To configure the number of retry prompts that are permitted per-session: Edit the /etc/security/pwquality.conf to include retry=3, or a lower value if site policy is more restrictive. The DoD requirement is a maximum of 3 prompts per session. Setting the password retry prompts that are permitted on a per-session basis to a low value requires some software, such as SSH, to re-connect. This can slow down and draw additional attention to some types of password-guessing attacks. Note that this is different from account lockout, which is provided by the pam_faillock module. var_password_pam_retry=3
R68 CCE-83403-6 Set number of Password Hashing Rounds - password-auth Configure the number or rounds for the password hashing algorithm. This can be accomplished by using the rounds option for the pam_unix PAM module.

In file /etc/pam.d/password-auth append rounds=65536 to the pam_unix.so entry, as shown below: 
password sufficient pam_unix.so ...existing_options... rounds=65536
The system's default number of rounds is 5000. 		Using a higher number of rounds makes password cracking attacks more difficult. var_password_pam_unix_rounds=65536
R68 CCE-83386-3 Set number of Password Hashing Rounds - system-auth Configure the number or rounds for the password hashing algorithm. This can be accomplished by using the rounds option for the pam_unix PAM module.

In file /etc/pam.d/system-auth append rounds=65536 to the pam_unix.so entry, as shown below: 
password sufficient pam_unix.so ...existing_options... rounds=65536
The system's default number of rounds is 5000. 		Using a higher number of rounds makes password cracking attacks more difficult. var_password_pam_unix_rounds=65536
R68 CCE-80893-1 Set PAM''s Password Hashing Algorithm The PAM system service can be configured to only store encrypted representations of passwords. In "/etc/pam.d/system-auth", the password section of the file controls which PAM modules to execute during a password change. Set the pam_unix.so module in the password section to include the option sha512 and no other hashing algorithms as shown below: 
password    sufficient    pam_unix.so sha512 other arguments...

This will help ensure that new passwords for local users will be stored using the sha512 algorithm. 		Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised. Passwords that are encrypted with a weak algorithm are no more protected than if they are kept in plain text.

This setting ensures user and group account administration utilities are configured to store only encrypted representations of passwords. Additionally, the crypt_style configuration option in /etc/libuser.conf ensures the use of a strong hashing algorithm that makes password cracking attacks more difficult. 		var_password_hashing_algorithm_pam=sha512
R69 CCE-86076-7 Name Service Switch does not use NIS Each call to a function which retrieves data from a system database like the password or group database is handled by the Name Service Switch implementation in the GNU C library. The various services provided are implemented by independent modules, each of which naturally varies widely from the other. One of such modules is the nis module, which allows to get information from NIS servers. NIS service is insecure and should not be used.
R74 CCE-82174-4 Disable Postfix Network Listening Edit the file /etc/postfix/main.cf to ensure that only the following inet_interfaces line appears: 
inet_interfaces = loopback-only
 This ensures postfix accepts mail messages (such as cron job reports) from the local system only, and not from the network, which protects it from network attack. var_postfix_inet_interfaces=loopback-only
R75 CCE-82381-5 Configure System to Forward All Mail For The Root Account Make sure that mails delivered to root user are forwarded to a monitored email address. Make sure that the address change_me@localhost is a valid email address reachable from the system in question. Use the following command to configure the alias: 
$ sudo echo "root: change_me@localhost" >> /etc/aliases
$ sudo newaliases
 A number of system services utilize email messages sent to the root user to notify system administrators of active or impending issues. These messages must be forwarded to at least one monitored email address. var_postfix_root_mail_alias=change_me@localhost
R76
R79		 CCE-80675-2 Build and Test AIDE Database Run the following command to generate a new database: 
$ sudo /usr/sbin/aide --init
By default, the database will be written to the file /var/lib/aide/aide.db.new.gz. Storing the database, the configuration file /etc/aide.conf, and the binary /usr/sbin/aide (or hashes of these files), in a secure location (such as on read-only media) provides additional assurance about their integrity. The newly-generated database can be installed as follows: 
$ sudo cp /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz
To initiate a manual check, run the following command: 
$ sudo /usr/sbin/aide --check
If this check produces any unexpected output, investigate. 		For AIDE to be effective, an initial database of "known-good" information about files must be captured and it should be able to be verified against the installed files.
R76
R79		 CCE-80844-4 Install AIDE The aide package can be installed with the following command: 
$ sudo yum install aide
 The AIDE package must be installed if it is to be available for integrity checking.