Bug 815516

+++ This bug was initially created as a clone of Bug #768087 +++

Description of problem:
The remember functionality of pam_unix can compare against the wrong username’s old passwords if the username is a substring of another username.  The substring must be at the beginning of both usernames for this to occur.  For example, a username ‘test’ will look at the old passwords of ‘test123’.

Version-Release number of selected component (if applicable):
pam-0.99.6.2-6.el5_5.2.i386.rpm

How reproducible:
Always

Steps to Reproduce:
1.  Make sure remember=8 or something similar is enabled on pam_unix in the password stack
2.  Create a user ‘test1’ and change the password a few times
3.  Create a user ‘test’ and change the password to a previous password of test1

  
Actual results:
The password change is denied, however, it should not have been.

Expected results:
The password change is allowed.

Additional info:

You can see the erroneous code in pam_unix_passwd.c inside of the pam_unix module directory (in function save_old_password):

    while (fgets(buf, 16380, opwfile)) {
    if (!strncmp(buf, forwho, strlen(forwho))) {

The fix is to search for a line that starts with the username followed immediately by a colon.  


The same erroneous code exists in "pam_unix_passwd.c" in function check_old_password:

    while (fgets(buf, 16380, opwfile)) {
        if (!strncmp(buf, forwho, strlen(forwho))) {