Solaris Password Policy

From Brandonhutchinson.com

Revision as of 15:01, 7 December 2007

The following steps are for Solaris 9, although are probably also applicable for Solaris 2.6, 7, and 8. Solaris 10 has much better password controls built-in.

Password Aging

New Accounts

/etc/default/passwd is the file related to password aging on new accounts.

• MAXWEEKS= is the maximum number of weeks a password may be used.
• MINWEEKS= is the minimum number of weeks allowed between password changes.
• WARNWEEKS= (not present by default) is the number of weeks' warning given before a password expires.

Existing Accounts

/usr/bin/passwd is used to modify password aging on existing accounts. passwd does not update the last password change field (field 3) in /etc/shadow, so passwords could expire immediately after running it.

Example

User hutchib was already created with no password aging (MAXWEEKS= in /etc/default/passwd). To configure the following:

• A minimum of 7 days between password changes.
• Password expiration after 90 days.
• Begin warning about password expiration 14 days in advance.

# /usr/bin/passwd -n 7 -w 14 -x 90 hutchib

What happens when your password expires?

When your password expires, you are allowed a "grace login" where your old password is accepted, but you must immediately change your password. After changing your password, the connection is closed and you must login again.

WARNING: Your password has expired.
You must change your password now and login again!
passwd: Changing password for hutchib
Enter existing login password: 
New Password: 
Re-enter new Password: 
passwd: password successfully changed for hutchib
Connection to host closed.

Password Length and Complexity

Minimum password length is configured using the PASSLENGTH= value in /etc/default/passwd.

The default Solaris install does not provide pam_cracklib or pam_passwdqc. If the default password complexity rules are insufficient, these PAM modules (preferably pam_passwdqc) should be used.

Default password complexity rules from passwd(1):

    Passwords must be constructed to meet the following require-
    ments:

       o  Each password must have PASSLENGTH  characters,  where
          PASSLENGTH  is  defined  in /etc/default/passwd and is
          set to 6. Only the first eight characters are signifi-
          cant.

       o  Each password must contain  at  least  two  alphabetic
          characters and at least one numeric or special charac-
          ter. In this case, "alphabetic" refers to all upper or
          lower case letters.

       o  Each password must differ from the user's  login  name
          and  any reverse or circular shift of that login name.
          For comparison purposes, an upper case letter and  its
          corresponding lower case letter are equivalent.

       o  New passwords must differ from the  old  by  at  least
          three  characters.  For  comparison purposes, an upper
          case letter and its corresponding  lower  case  letter
          are equivalent.

Password History

Password history--i.e., preventing re-use of old passwords--may be enabled using the third-party PAM module pam_history[1]

Example: Prevent re-use of each user's last 24 passwords.

• Install the COMSpamph package.

• Create a password history database that will store 24 passwords. Without this step, only 5 passwords would be stored.

# /usr/local/sbin/mkhistory -c -h 24

• Configure PAM.

Relevant entry in bold in /etc/pam.conf:

other   password required       pam_dhkeys.so.1
other   password requisite      pam_authtok_get.so.1
other   password requisite      pam_authtok_check.so.1
other   password requisite      pam_history.so.1 func=$1$
other   password required       pam_authtok_store.so.1

The func=$1$ is used to store the passwords in MD5 format in the password history database. By default, they would be stored in crypt format with only 8 characters of significance.

The func= option is only available in COMSpamph for Solaris 9 and later. See the Documentation and release notes for more information.

Problems with pam_history

Although the pam_history module works in preventing password re-use, I experience the following two problems on my Solaris 9 SPARC system.

• /usr/local/sbin/mkhistory always returns a last change date of the epoch.

# /usr/local/sbin/mkhistory
         hutchib:       Wed Dec 31 18:00:00 1969

• A non-descriptive error message--"Please try again"--is returned when attempting to re-use a password in the history.

$ passwd
passwd: Changing password for hutchib
Enter existing login password: 
New Password: 

Please try again
New Password:

Account Lockout

Account lockout after a number of unsuccessful authentication attempts may be enabled using the third-party PAM module pam_login_limit[2]. In this example, accounts are locked out for 30 minutes after 5 failed login attempts. During this 30 minutes, any authentication attempts for the user account, both successful or unsuccessful, will reset the 30 minute timer.

To enable account lockout:

• Install the COMSpamll package.

• Configure PAM.

Relevant entries in bold in /etc/pam.conf:

Lines preceding pam_login_limit must be a sufficient control. The order of pam_dial_auth and pam_unix_auth are switched to accommodate this. If not specified, the default count_limit is 3.

login   auth requisite          pam_authtok_get.so.1
login   auth required           pam_dhkeys.so.1
login   auth required           pam_dial_auth.so.1
login   auth sufficient         pam_unix_auth.so.1
login   auth required           pam_login_limit.so.1 count_limit=5 timeout_account=1800

ssh does not use the PAM login service unless UseLogin yes is defined in sshd_config. ssh uses the sshd PAM login service if it's defined, or other if not.

other   auth requisite          pam_authtok_get.so.1
other   auth required           pam_dhkeys.so.1
other   auth sufficient         pam_unix_auth.so.1
other   auth required           pam_login_limit.so.1 count_limit=5 timeout_account=1800

The following line in bold resets the failed login count after a successful login.

other   account required        pam_login_limit.so.1 count_limit=5 timeout_account=1800
other   account requisite       pam_roles.so.1
other   account required        pam_projects.so.1
other   account required        pam_unix_account.so.1

The following optional line in bold resets the failed login count after a successful password change. Without this line, if an administrator resets the password, the user will still have to wait timeout_account seconds until the password is unlocked. Or, the administrator could manually run /usr/local/sbin/login_account -c user to clear the counter.

other   password required       pam_dhkeys.so.1
other   password requisite      pam_authtok_get.so.1
other   password requisite      pam_authtok_check.so.1
other   password requisite      pam_history.so.1 history=24 func=$1$
other   password required       pam_authtok_store.so.1
other   password optional       pam_login_limit.so.1

• If you are using ssh:
  • Make sure PAM support is enabled by setting UsePAM yes in sshd_config.
  • You may want to disable password authentication by setting PasswordAuthentcation no in sshd_config. Without this, you will be prompted two additional times for your password if your account is locked (although you still won't be able to authenticate).

With PasswordAuthentication yes:

$ ssh hutchib@host
Password: 
Password: 
Password: 
hutchib@host's password: 
Permission denied, please try again.
hutchib@host's password: 
Received disconnect from 10.209.180.14: 2: Too many authentication failures for hutchib

With PasswordAuthentication no:

$ ssh hutchib@sprcmdo001
Password: 
Password: 
Password: 
Permission denied (publickey,keyboard-interactive,hostbased).

Links

• Changing the Default Algorithm for Password Encryption
• PAM Modules Version 1.05
• PAM Modules FAQ