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

Check that the system locks an account for a minimum of 15 minutes after three unsuccessful logon attempts within a period of 15 minutes with the following command:

# 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 "deny" parameter is set to "0" or a value greater than "3" on both "auth" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

If the "even_deny_root" parameter is not set on both "auth" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

If the "fail_interval" parameter is set to "0" or is set to a value less than "900" on both "auth" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

If the "unlock_time" parameter is not set to "0", "never", or is set to a value less than "900" on both "auth" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

Note: The maximum configurable value for "unlock_time" is "604800".

If any line referencing the "pam_faillock.so" module is commented out, 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 "deny" parameter is set to "0" or a value greater than "3" on both "auth" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

If the "even_deny_root" parameter is not set on both "auth" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

If the "fail_interval" parameter is set to "0" or is set to a value less than "900" on both "auth" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

If the "unlock_time" parameter is not set to "0", "never", or is set to a value less than "900" on both "auth" lines with the "pam_faillock.so" module or is missing from these lines, this is a finding.

Note: The maximum configurable value for "unlock_time" is "604800".

If any line referencing the "pam_faillock.so" module is commented out, this is a finding.

Fix

Configure the operating system to lock an account for the maximum period when three unsuccessful logon attempts in 15 minutes are made.

Add/Modify the appropriate sections 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: Per requirement OL07-00-010199, Oracle Linux 7 must be configured to not overwrite custom authentication configuration settings while using the authconfig utility, otherwise manual changes to the listed files will be overwritten whenever the authconfig utility is used.