cyberstrikeus 9.5 Restrict Access to the su Command (Scored)
Profile Applicability
- Level 1
Description
The su command allows a user to run a command or shell as another user. The program has been superseded by sudo, which allows for more granular control over privileged access. Normally, the su command can be executed by any user. By uncommenting the pam_wheel.so statement in /etc/pam.d/su, the su command will only allow users in the wheel group to execute su.
Rationale
Restricting the use of su, and using sudo in its place, provides system administrators better control of the escalation of user privileges to execute privileged commands. The sudo utility also provides a better logging and audit mechanism, as it can log each command executed via sudo, whereas su can only record that a user executed the su program.
Audit Procedure
Using Command Line
grep pam_wheel.so /etc/pam.d/su
grep wheel /etc/group
Expected Result
auth required pam_wheel.so use_uid
wheel:x:10:root, <user list>
Remediation
Using Command Line
Add the following line to the /etc/pam.d/su file:
auth required pam_wheel.so use_uid
Once this is done, create a comma separated list of users in the wheel statement in the /etc/group file.
Default Value
The pam_wheel.so line is commented out by default in /etc/pam.d/su.
References
- CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
Profile
Level 1 - Scored