5.3.4 Ensure password hashing algorithm is SHA-512

Information

The commands below change password encryption from md5 to sha512 (a much stronger
hashing algorithm). All existing accounts will need to perform a password change to
upgrade the stored hashes to the new algorithm.

Rationale:

The SHA-512 algorithm provides much stronger hashing than MD5, thus providing
additional protection to the system by increasing the level of effort for an attacker to
successfully determine passwords.

Note that these change only apply to accounts configured on the local system.

Solution

Set password hashing algorithm to sha512. Many distributions provide tools for updating
PAM configuration, consult your documentation for details. If no tooling is provided edit
the appropriate /etc/pam.d/ configuration file and add or modify the pam_unix.so lines to
include the sha512 option:

password sufficient pam_unix.so sha512

Notes:

Consult your documentation for the appropriate PAM file and module.

Additional module options may be set, recommendation only covers those listed here.

If it is determined that the password algorithm being used is not SHA-512, once it is
changed, it is recommended that all user ID's be immediately expired and forced to change
their passwords on next login. To accomplish that, the following commands can be used.
Any system accounts that need to be expired should be carefully done separately by the
system administrator to prevent any potential problems.

# cat /etc/passwd | awk -F: '( $3 >= 500 && $1 != "nfsnobody" ) { print $1 }'
| xargs -n 1 chage -d 0

This command assumes a system UID split at 500. Some distributions split at UID 1000
instead, consult your documentation and/or the UID_MIN setting in /etc/login.defs to
determine which is appropriate for you.

See Also

https://workbench.cisecurity.org/files/2420