The operating system must prohibit password reuse for a minimum of five generations.

From Apple OS X 10.11 Security Technical Implementation Guide

Part of SRG-OS-000077-GPOS-00045

Associated with: CCI-000200

SV-82151r1_rule The operating system must prohibit password reuse for a minimum of five generations.

Vulnerability discussion

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. If the information system or application allows the user to consecutively reuse their password when that password has exceeded its defined lifetime, the end result is a password that is not changed as per policy requirements.

Check content

Password policy can be set with the "Passcode Policy" configuration profile or the "pwpolicy" utility. If password policy is set with a configuration profile, run the following command to check if the system is configured to require that users cannot reuse one of their five previously used passwords: system_profiler SPConfigurationProfileDataType | /usr/bin/grep pinHistory If "pinHistory" is not set to "5" or higher, or is undefined, this is a finding. If password policy is set with the "pwpolicy" utility, run the following command instead: /usr/bin/sudo /usr/bin/pwpolicy getaccountpolicies Look for the line "policyCategoryPasswordContent". If it does not exist, and password policy is not controlled by a directory server, this is a finding. Otherwise, in the array section that follows it, there should be a section that contains a check such as "none policyAttributePasswordHashes in policyAttributePasswordHistory". This searches for the hash of the user-entered password in the list of previous password hashes. In the "policyParameters" section that follows it, "policyAttributePasswordHistoryDepth" must be set to "5" or greater. If this parameter is not set to "5" or greater, or if no such check exists, this is a finding.

Fix text

This setting may be enforced using the "Passcode Policy" configuration profile or by a directory server. To set the password policy without a configuration profile, run the following command to save a copy of the current "pwpolicy" account policy file: /usr/bin/sudo /usr/bin/pwpolicy getaccountpolicies | tail -n +2 > pwpolicy.plist Open the generated file in a text editor. If the file does not yet contain any policy settings, replace with . If there already is a policy block that refers to password history, ensure it is set to "5". If the line "policyCategoryPasswordContent" is not present in the file, add the following text immediately after the opening tag in the file: policyCategoryPasswordContent policyContent none policyAttributePasswordHashes in policyAttributePasswordHistory policyIdentifier Password History policyParameters policyAttributePasswordHistoryDepth 5 If the line "policyCategoryPasswordContent" is already present in the file, the following text should be added just after the opening tag that follows the line instead: policyContent none policyAttributePasswordHashes in policyAttributePasswordHistory policyIdentifier Password History policyParameters policyAttributePasswordHistoryDepth 5 After saving the file and exiting to the command prompt, run the following command to load the new policy file: /usr/bin/sudo /usr/bin/pwpolicy setaccountpolicies pwpolicy.plist Note: Updates to password restrictions must be thoroughly evaluated in a test environment. Mistakes in configuration may block password change and local user creation operations, as well as, lock out all local users, including administrators.

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