The macOS system must enforce the limit of three consecutive invalid logon attempts by a user before the user account is locked.

From Apple OS X 10.13 Security Technical Implementation Guide

Part of SRG-OS-000329-GPOS-00128

Associated with: CCI-002238

SV-96439r1_rule The macOS system must enforce the limit of three consecutive invalid logon attempts by a user before the user account is locked.

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. Setting a lockout expiration of 15 minutes is an effective deterrent against brute forcing that also makes allowances for legitimate mistakes by users.

Check content

Password policy can be set with a configuration profile or the "pwpolicy" utility. If password policy is set with a configuration profile, run the following command to check if the system has the correct setting for the number of permitted failed logon attempts and the logon reset timer: /usr/sbin/system_profiler SPConfigurationProfileDataType | /usr/bin/grep 'maxFailedAttempts\|minutesUntilFailedLoginReset' If "maxFailedAttempts" is not set to "3" and "minutesUntilFailedLoginReset" is not set to "15", this is a finding. If password policy is set with the "pwpolicy" utility, the variable names may vary depending on how the policy was set. To check if the password policy is configured to disable an account for 15 minutes after 3 unsuccessful logon attempts, run the following command to output the password policy to the screen: /usr/bin/sudo /usr/bin/pwpolicy getaccountpolicies Look for the line "policyCategoryAuthentication". If this does not exist, and password policy is not controlled by a directory service, this is a finding. In the array that follows, there should be one or more sections that describe policy checks. One should contain a that allows users to log on if "policyAttributeFailedAuthentications" is less than "policyAttributeMaximumFailedAuthentications". Under policyParameters, "policyAttributeMaximumFailedAuthentications" should be set to "3". If "policyAttributeMaximumFailedAuthentications" is not set to "3", this is a finding. In the same check or in another section, there should be a that allows users to log on if the "policyAttributeCurrentTime" is greater than the result of adding "15" minutes (900 seconds) to "policyAttributeLastFailedAuthenticationTime". The check might use a variable defined in its "policyParameters" section. If the check does not exist or if the check adds too great an amount of time, this is a finding.

Fix text

This setting may be enforced using the "Passcode Policy" configuration profile or by a directory service. 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 and ensure it contains the following text after the opening tag and before the closing tag. Replace first with if necessary. policyCategoryAuthentication policyContent (policyAttributeFailedAuthentications < policyAttributeMaximumFailedAuthentications) OR (policyAttributeCurrentTime > (policyAttributeLastFailedAuthenticationTime + autoEnableInSeconds)) policyIdentifier Authentication Lockout policyParameters autoEnableInSeconds 900 policyAttributeMaximumFailedAuthentications 3 If the line "policyCategoryAuthentication" already exists, the following text should be used instead and inserted after the first tag that follows it: policyContent (policyAttributeFailedAuthentications < policyAttributeMaximumFailedAuthentications) OR (policyAttributeCurrentTime > (policyAttributeLastFailedAuthenticationTime + autoEnableInSeconds)) policyIdentifier Authentication Lockout policyParameters autoEnableInSeconds 900 policyAttributeMaximumFailedAuthentications 3 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 or bugs in OS X may block password change and local user creation operations, as well as lock out all local users, including administrators.

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