Less known Solaris features: On passwords - Part 3: Using a password policy

User have the habit to break any security policy. At least as long you don’t enforce it. One of the most annoying habit from the view of the security people is the tendency to choose weak passwords, the name of the boy or girl friend, the prefered brand of cars, birthdays … you name it. This passwords are everything but secure. But you can configure Solaris to check the new passwords.

Specifing a password policy

There is a central file in Solaris controling the password policy. In /etc/default/passwd you define what requirements a password must fulfill before Solaris allows the user to set this password. Let´s have a look in the actual file of a standard solaris system. You have to log into your system as root. One important note for trying out this feature. You need to log into your system as a normal user in a different window.root can set any password without a check by the password policy thus it would look like that your configuration changes had no effect:

# cat passwd<br />
[... omitted CDDL header ...]<br />
#<br />
#HISTORY=0<br />
#MINDIFF=3<br />
#MINALPHA=2<br />
#MINUPPER=0<br />
#MINLOWER=0<br />
#MINDIGIT=0<br />

You enable the checks by uncommenting it and set a reasonable value to the line. When you enable all the checks, it´s actually harder to find a valid password than a non-valid one. Whenever thinking about a really hard password policy you should take into consideration, that people tend to make notes about their password when they can´t remember it. And a strong password under the keyboard is obviously less secure than a weak password in the head of the user.

<table width=90%
Parameter Description MAXWEEKS This variable specifies the maximum age for a password. MINWEEKS This variable specifies the minimum age for a password. The rationale for this settings gets clearer when i talk about the HISTORY setting PASSLENGTH The minimum length for a password HISTORY This variable specifies the length of a history buffer. You can specify a length of up to 26 passwords in the buffer. The MINWEEKS buffer is useful in conjunction with this parameter. There is a trick to circumvent this buffer and to get you old password back. Just change it as often as the length of the buffer plus one time. The MINWEEK parameter prevents this. WHITESPACE This variable defines if you you are allowed to use a whitespace in your password NAMECHECK When you set this variable to YES, the system checks if the password and login name are identical. So using the password root for the use root would be denied by this setting. The default, by the way is, yes </table>

Besides of this basic checks you can use /etc/default/passwd/ enforce checks for the complexity of passwords. So you can prevent the user from setting to simple passwords.

<table width=90%
Parameter Description MINDIFF Let´s assume you´ve used 3 here. If your old password was batou001, a new password would be denied, if you try to use batou002 as only on character was changed. batou432 would be a valid password. MINUPPER With this variable you can force the usage of upper case characters. Let´s assume you´ve specified 3 here, a password like wasabi isn´t an allowed choice, but you could use WaSaBi MINLOWER With this variable you enable the check for the amount of lower case characters in your password. In the case you´ve specified 2 here, a password like WASABI isn´t allowed, but you can use WaSaBI
</tr> MAXREPEATS Okay, some users try to use passwords like aaaaaa2=. Obviously this isn´t really a strong password. When you set this password to 2 you, it checks if at most 2 consecutive characters are identical. A password like waasabi would be allowed, but not a password like waaasabi MINSPECIAL The class SPECIAL consists out of characters like !=(). Let´s assume you´ve specified 2, a password like !ns!st= would be fine, but the password insist is not a valid choice. MINDIGIT With this password you can specify the amount of the numbers in your password. Let´s a assume you specify 2, a password like snafu01 would will be allowed. A password like snafu1 will be denied. MINALPHA You can check with this variable for a minimum amount of alpha chars (a-z and A-Z) . When you set a value of 2 on this variable, a password like aa23213 would be allowed, a password like 0923323 would be denied MINNONALPHA This checks for the amount of non-alpha characters (0-9 and special chars). A value of 2 would lead to the denial of wasabi, but a password like w2sab! is okay </table> </center>

Using wordlists

There is another way to force stronger passwords. You can deny every password that is located in a list of words. The program for changing password is capable to compare the new password against a list of words. With this function you can deny the most obvious choices of passwords. But you should initialize the dictionary with a list of words before you can use this feature.
# mkpwdict -s /usr/share/lib/dict/words<br />
mkpwdict: using default database location: /var/passwd.
The file /usr/share/lib/dicts/words is a file in the Solaris Operating System containing a list of words. It´s normally used by spell checking tools. Obviously you should use a workdlist in your own language, as user tend do choose words from their own language as passwords. So an english wordlist in Germany may be not that effective.You find a list of other wordlists here
Now you have to tell Solaris to use this lists. There are some parameters in the /etc/default/password i didn´t covered before:
<table width=90%
Parameter Description DICTIONLIST This variable can contain a list of dictionary files seperated by a comma. You must specify full pathnames. The words from these files are merged into a database that is used to determine whether a password is based on a dictionary word DICTIONDBDIR The directory where the generated dictionary databases reside </table>

When none of the both variables is specified in the /etc/default/passwd then no dictionary check is performed. Let´s try it. I´ve uncommented the DICTIONDBDIR line of the /etc/default/passwd file and used the standard value /var/passwd. One of the word in the dictionary i imported is the word airplane:
<br />
$ passwd<br />
passwd: Changing password for jmoekamp<br />
Enter existing login password: <b>chohw!2</b><br />
New Password: <b>airplane</b><br />
passwd: password is based on a dictionary word.
Solaris denies the password as it´s based on a word in the imported dictionary.