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Full Discussion: Shadow file password policy
Operating Systems Linux Red Hat Shadow file password policy Post 302458509 by pinga123 on Friday 1st of October 2010 03:04:13 AM
Old 10-01-2010
Shadow file password policy

Today i was going through some of security guides written on linux .

Under shadow file security following points were mentioned.

1)The encrypted password stored under /etc/shadow file should have more than 14-25 characters.
2)Usernames in shadow file must satisfy to all the same rules as usernames in /etc/passwd.
3)password for application Username should display * if username is not locked.
4)If a user is locked it should be displayed as ! as the first character in second field of shadow file.

Confusion for point 1 and 2:
Now i m confused as why the encrypted password should be more than 14-25 characters.
Also what rules to satisfy How to check it?

Confusion for point 3 and 4:
There are lot of users with * as second field i guess they are not locked but according to 4th point there are lot of users with ! as first characters.
How would i check whether they are actually locked or not.

I m posting the output of /etc/shadow and /etc/passwd files for the account.

/etc/passwd
Quote:
admin:x:500:500::/home/admin:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
/etc/shadow

Quote:
admin:$1$YSmsjgr7$m3YjwsZNdQ/Z24QXGWj8O1:14879:0:99999:7:::
ntp:!!:14866:0:99999:7:::
mail:*:14866:0:99999:7:::
 

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SHADOW(5)							File Formats Manual							 SHADOW(5)

NAME
shadow - encrypted password file DESCRIPTION
shadow contains the encrypted password information for user's accounts and optional the password aging information. Included is Login name Encrypted password Days since Jan 1, 1970 that password was last changed Days before password may be changed Days after which password must be changed Days before password is to expire that user is warned Days after password expires that account is disabled Days since Jan 1, 1970 that account is disabled A reserved field The password field must be filled. The encryped password consists of 13 to 24 characters from the 64 character alphabet a thru z, A thru Z, 0 thru 9, . and /. Refer to crypt(3) for details on how this string is interpreted. The date of the last password change is given as the number of days since Jan 1, 1970. The password may not be changed again until the proper number of days have passed, and must be changed after the maximum number of days. If the minimum number of days required is greater than the maximum number of day allowed, this password may not be changed by the user. An account is considered to be inactive and is disabled if the password is not changed within the specified number of days after the pass- word expires. An account will also be disabled on the specified day regardless of other password expiration information. This information supercedes any password or password age information present in /etc/passwd. This file must not be readable by regular users if password security is to be maintained. FILES
/etc/passwd - user account information /etc/shadow - encrypted user passwords SEE ALSO
chage(1), login(1), passwd(1), su(1), passwd(5), pwconv(8), pwunconv(8), sulogin(8) AUTHOR
Julianne Frances Haugh (jockgrrl@ix.netcom.com) SHADOW(5)
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