Vulnerability Discussion

Unrestricted usage of ptrace allows compromised binaries to run ptrace on other processes of the user. Like this, the attacker can steal sensitive information from the target processes (e.g., SSH sessions, web browser, etc.) without any additional assistance from the user (i.e., without resorting to phishing).

Satisfies: SRG-OS-000132-GPOS-00067, SRG-OS-000480-GPOS-00227

Check

Verify RHEL 9 restricts the usage of ptrace to descendant processes with the following commands:

$ sysctl kernel.yama.ptrace_scope

kernel.yama.ptrace_scope = 1

If the returned line does not have a value of "1", or a line is not returned, this is a finding.

Check that the configuration files are present to enable this kernel parameter.

$ sudo /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F kernel.yama.ptrace_scope| tail -1

kernel.yama.ptrace_scope = 1

If the network parameter "kernel.yama.ptrace_scope" is not equal to "1", or nothing is returned, this is a finding.

Fix

Configure the currently loaded kernel parameter to the secure setting:

$ sudo sysctl -w kernel.yama.ptrace_scope=1

Configure RHEL 9 to restrict usage of ptrace to descendant processes by adding the following line to a file in the "/etc/sysctl.d" directory:

kernel.yama.ptrace_scope = 1

The system configuration files must be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sysctl --system