School assignment #3

pchange.pl

#!/usr/bin/perl -w
#
# Check if original password has changed.
#
# Gets user ssn from passwd comment field and hashing it with Crypt::PasswdMD5.
# Program checks if the hashed reversed ssn is the same as the current password.
# Prints message if a user has not changed his/hers password.

# Include Crypt::PasswdMD5 Module.
use Crypt::PasswdMD5;

# Open file $shadow and assign to @shadow array.
$shadow = "shadow";
open(SHAD, $shadow) or die($!);
@shadow = <SHAD>;
# As the file is loaded into @shadow array, it can be closed.
close(SHAD);

# Open passwd file.
$users = "passwd";
open(USRS, $users) or die($!);
@users = <USRS>;
close(USRS);

# Set all users with passwords in hash.
foreach (@shadow) {
  # Split values in shadow.
  @shadow_posts = split(":", $_);
  # If username match a letter, two numbers and a few letters.
  if ($shadow_posts[0] =~ /\w(\d\d)(\w+)/) {
    # Add username as key, password as value.
    $usrh{$shadow_posts[0]} = $shadow_posts[1];
  }
}

# Get usernames and personalnumbers from passwd.
foreach (@users) {
  # Split values, if username exists in hash add comment pnr.
  @users_posts = split(":", $_);
  if (exists($usrh{$users_posts[0]})) {
    # Comment field is 4, string is reversed and last 11 chars (pnr) is used.
    @pnr = split(' ', $users_posts[4]); 
    # Set reverse pnr in hash with username as key.
    $usrc{$users_posts[0]} = reverse($pnr[2]);
  }
}

# Print Users and passwords.
foreach (keys %usrh) {
  # If password does not exist in $usrc{username} set string NULL.
  if (!exists($usrc{$_})) {$pw = "NULL";} 
  else {$pw = $usrc{$_};}
  # If the password contains $1$ it is unix md5, therefor it can be checked.
  @pass = split(/\$/,$usrh{$_});
  if ($pass[0] eq "" ) {
    # Crypt pnr with salt in passwd.
    $cryptedpassword = unix_md5_crypt($pw, $pass[2]);
    @cpass = split(/\$/,$cryptedpassword);
    print "User $_: $pass[3] - $cpass[3] ($pw)\n";
    # See if password is unchanged.
    if ($pass[3] eq $cpass[3]) {
       print "\tUser $_ has not changed his/her password since add.";
    }
  }
}