Cis Ubuntu1604 V200 5 4 1

Ensure password creation requirements are configured

Profile Applicability:

• Level 1 - Server
• Level 1 - Workstation

Assessment Status: Automated

Description

The pam_pwquality.so module checks the strength of passwords. It performs checks such as making sure a password is not a dictionary word, it is a certain length, contains a mix of characters (e.g. alphabet, numeric, other) and more. The following are definitions of the pam_pwquality.so options.

The following options are set in the /etc/security/pwquality.conf file:

• Password Length:

  • minlen = 14 - password must be 14 characters or more

• Password complexity:

  • minclass = 4 - The minimum number of required classes of characters for the new password (digits, uppercase, lowercase, others)

  OR

  • dcredit = -1 - provide at least one digit
  • ucredit = -1 - provide at least one uppercase character
  • ocredit = -1 - provide at least one special character
  • lcredit = -1 - provide at least one lowercase character

The following is set in the /etc/pam.d/common-password file:

• retry=3 - Allow 3 tries before sending back a failure. The settings shown above are one possible policy. Alter these values to conform to your own organization's password policies.

Rationale

Strong passwords protect systems from being hacked through brute force methods.

Audit Procedure

Command Line

Verify password creation requirements conform to organization policy. Run the following command to verify the minimum password length is 14 or more characters:

grep '^\s*minlen\s*' /etc/security/pwquality.conf

Expected output:

minlen = 14

Run one of the following commands to verify the required password complexity:

grep '^\s*minclass\s*' /etc/security/pwquality.conf

Expected output:

minclass = 4

OR

grep -E '^\s*[duol]credit\s*' /etc/security/pwquality.conf

Expected output:

dcredit = -1
ucredit = -1
lcredit = -1
ocredit = -1

Run the following command to verify the number of attempts allowed before sending back a failure are no more than 3:

grep -E '^\s*password\s+(requisite|required)\s+pam_pwquality\.so\s+(\S+\s+)*retry=[1-3]\s*(\s+\S+\s*)*(\s+#.*)?$' /etc/pam.d/common-password

Expected output:

password        requisite                       pam_pwquality.so retry=3

Remediation

Command Line

Run the following command to install the pam_pwquality module:

apt install libpam-pwquality

Edit the file /etc/security/pwquality.conf and add or modify the following line for password length to conform to site policy:

minlen = 14

Edit the file /etc/security/pwquality.conf and add or modify the following line for password complexity to conform to site policy:

minclass = 4

OR

dcredit = -1
ucredit = -1
ocredit = -1
lcredit = -1

Edit the /etc/pam.d/common-password file to include the appropriate options for pam_pwquality.so and to conform to site policy:

password requisite pam_pwquality.so retry=3

Additional Information

Additional module options may be set, recommendation requirements only cover including try_first_pass and minlen set to 14 or more.

Settings in /etc/security/pwquality.conf must use spaces around the = symbol.

References

None

CIS Controls

Profile

• Level 1 - Server
• Level 1 - Workstation