atnonis has asked for the wisdom of the Perl Monks concerning the following question:

Hello monks!
I wanna create a script which will authenticate user against /etc/passwd. Is this possibly with perl!? If yes what should I look for, else any suggestion!?

Atnonis!
  • Comment on how to use /etc/passwd with perl programs

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Re: how to use /etc/passwd with perl programs
by TVSET (Chaplain) on Jul 02, 2003 at 22:26 UTC
    Although sauoq has alredy answered your question, I'd like to point out few things that you might find useful:
    • Rarely this days passwords are stored in /etc/passwd. Most probably you'll need to make use of /etc/shadow.
    • Rarely this days system passwords are stored plainly crypt()-ed. Most probably you'll need to work with MD5 or some other stronger cryptography.
    • If your system is using PAM, then you should do so too. Cpan has modules for you. With PAM you will not have to care about crypt/md5, /etc/passwd or /etc/shador, or even LDAP authentication for that matter.

    Leonid Mamtchenkov aka TVSET

[reply]
      Those are good points except for the second one. On my system at least, and I believe on all systems that provide nonstandard crypt(3) implementations, crypt will detect and use the right hash function if you pass the entire crypted password as the SALT. For example, I have a user with a password "test". His crypted password is $1$V80MC/nB$s/9nJGRaDB3xtUNpI7k0O.. Running this Perl code: 
      print crypt('test',
            '$1$V80MC/nB$s/9nJGRaDB3xtUNpI7k0O.'),
      "\n";

      [download]
      prints the correctly encrypted password.
[reply]
[d/l]
        Good catch - you are mostly right. Here is a quote from the man page: 

        GNU EXTENSION
       The glibc2 version of this function has the following  addition
+al  fea-
       tures.   If  salt is a character string starting with the three
+ charac-
       ters "$1$" followed by at most eight characters, and optionally
+  termi-
       nated  by  "$",  then instead of using the DES machine, the gli
+bc crypt
       function uses an MD5-based algorithm,  and  outputs  up  to  34
+  bytes,
       namely  "$1$<string>$", where "<string>" stands for the up to 8
+ charac-
       ters following "$1$" in the salt, followed by 22 bytes chosen f
+rom  the
       set [a-zA-Z0-9./].  The entire key is significant here (instead
+ of only
       the first 8 bytes).

       Programs using this function must be linked with -lcrypt.

        [download]

        ++

        Leonid Mamtchenkov aka TVSET

[reply]
[d/l]
Re: how to use /etc/passwd with perl programs
by sauoq (Abbot) on Jul 02, 2003 at 21:56 UTC

    Yes, it is possible. Read up on the getpwnam() and crypt() functions.

    If your system uses shadow passwords, you will need the script to run with the proper privs. (And, even then there is a small chance you might have some trouble. Everything should be fine if the system is sane though.)

    -sauoq
"My two cents aren't worth a dime.";
[reply]
Re: how to use /etc/passwd with perl programs
by LazerRed (Pilgrim) on Jul 02, 2003 at 21:59 UTC
    Could you be more specific? Why exactly do you want to do this? If a user is logged in, they're already authenticated. Is this perhaps a cgi type of situation, or some wierd network service? I think you'll find that your question is a bit too generic.

    Update: I'm a goober :) ignore me!

[reply]
      thank you LazerRed but sauoq had answer my query. thanks a lot guys!
      atnonis
[reply]

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