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V-268081

CAT II (Medium)

NixOS must enforce the limit of three consecutive invalid logon attempts by a user during a 15-minute time period.

Rule ID

SV-268081r1130954_rule

STIG

Anduril NixOS Security Technical Implementation Guide

Version

V1R2

CCIs

CCI-000044, CCI-002238, CCI-000172

Discussion

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-force attacks, is reduced. Limits are imposed by locking the account. Satisfies: SRG-OS-000021-GPOS-00005, SRG-OS-000329-GPOS-00128, SRG-OS-000470-GPOS-00214

Check Content

Verify that NixOS locks an account after three unsuccessful logon attempts within 15 minutes with the following commands:

$ cat /etc/pam.d/login

auth required pam_faillock.so preauth deny=3 even_deny_root fail_interval=900 unlock_time=0 dir=/var/log/faillock

If the "fail_interval" option is not set to "900" or less (but not "0") on the "preauth" lines with the "pam_faillock" module, or is missing from this line, this is a finding.

Fix Text

Configure NixOS to lock an account when three unsuccessful logon attempts occur within 15 minutes. 

Update the NixOS config, typically stored either in /etc/nixos/configuration.nix or /etc/nixos/flake.nix, to include the following lines:

 security.pam.services = let pamfile = ''
  auth required pam_faillock.so preauth silent audit deny=3 fail_interval=900 unlock_time=0
  auth sufficient pam_unix.so nullok try_first_pass
  auth [default=die] pam_faillock.so authfail audit deny=3 fail_interval=900 unlock_time=0
  auth sufficient pam_faillock.so authsucc

  account required pam_faillock.so
 '';
 in {
  login.text = pkgs.lib.mkDefault pamfile;
  sshd.text = pkgs.lib.mkDefault pamfile;
 };

Note that the entire pam file must be entered as this pamfile string.

Rebuild and switch to the new NixOS configuration:
$ sudo nixos-rebuild switch