Vulnerability Discussion

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.

Satisfies: SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005

Check

Verify the operating system automatically locks the root account until it is released by an administrator when three unsuccessful logon attempts in 15 minutes are made.

# grep pam_faillock.so /etc/pam.d/password-auth
auth required pam_faillock.so preauth silent audit deny=3 even_deny_root fail_interval=900 unlock_time=900
auth [default=die] pam_faillock.so authfail audit deny=3 even_deny_root fail_interval=900 unlock_time=900
account required pam_faillock.so

If the "even_deny_root" setting is not defined on both lines with the "pam_faillock.so" module, is commented out, or is missing from a line, this is a finding.

# grep pam_faillock.so /etc/pam.d/system-auth
auth required pam_faillock.so preauth silent audit deny=3 even_deny_root fail_interval=900 unlock_time=900
auth [default=die] pam_faillock.so authfail audit deny=3 even_deny_root fail_interval=900 unlock_time=900
account required pam_faillock.so

If the "even_deny_root" setting is not defined on both lines with the "pam_faillock.so" module, is commented out, or is missing from a line, this is a finding.

Fix

Configure the operating system to lock automatically the root account until the locked account is released by an administrator when three unsuccessful logon attempts in 15 minutes are made.

Modify the first three lines of the auth section and the first line of the account section of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth silent audit deny=3 even_deny_root fail_interval=900 unlock_time=900
auth sufficient pam_unix.so try_first_pass
auth [default=die] pam_faillock.so authfail audit deny=3 even_deny_root fail_interval=900 unlock_time=900
account required pam_faillock.so

Note: Manual changes to the listed files may be overwritten by the "authconfig" program. The "authconfig" program should not be used to update the configurations listed in this requirement.