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php3-list | 199903

RE: [PHP3] .htpasswd From: mike grommet (mgrommet <email protected>)
Date: 03/05/99

Sorry to step in here, but it should be noted that this method, while
much better than nothing, still does not eliminate the possibility of
concurrent
attempts to write... After all, what if two processes at the same time, look
for the lock file,
it doesnt exist yet, so both processes attempt to create a lock file and
then happily
attempt to modify your file. Semaphores are the only complete way of
eliminating this problem.

The chances of this happening in the general case is slim, but the
exceptions to the rule
are always the problems you have to be the most on top of.

Just my $.02

-----Original Message-----
From: Cameron Just [mailto:ccjust <email protected>]
Sent: Thursday, March 04, 1999 10:31 PM
To: Matthew Joseff
Cc: php3 <email protected>
Subject: Re: [PHP3] .htpasswd

Heres some code we just wrote which adds users to a htpasswd file.

1. Creates a temp file called $htpasswdfile.".lock"
2. If this file exists then it waits until doesn't(This stops the
occurrence of two people adding at once)
3. It reads in an existing htpasswd file and dumps contents into and array.
4. Makes sure the new username doesn't already exist.(If it does removes
lock file and exits.)
5. Generates the new username password combination and tacks it onto the
end.
6. Writes the new htpasswd file.
7. Removes Lock file.

The Lock file never gets written to it's just there to let other processes
know that the htpasswd file is currently being modified.
This could be done using semaphores but we didn't want to re-learn them
just yet :)
You could also write other functions to delete and modify users using the
same principles.

VARIABLES USED
.............................
$username
$password
$htpasswdfile
............................

function useradd($username,$password) {
global $htpasswdfile;

          while (file_exists($htpasswdfile.".lock")) {
                sleep(1);
                clearstatcache();
          }

        symlink($htpasswdfile,$htpasswdfile.".lock");
        $userfile = file($htpasswdfile);

        for ($i=0;$i<count($userfile);$i++) {
                $uppairs[] = explode(":",$userfile[$i]);
                $uppairs[$i][1] = trim($uppairs[$i][1]);
                if ($uppairs[$i][0] == $username) {
                        unlink($htpasswdfile.".lock");
                        return -1;
                }
        }
        $uoutfile .= $username.":".crypt($password)."\n";

        $ufp = fopen($htpasswdfile,"a");
        fputs($ufp,$uoutfile);
        fclose($ufp);
        unlink($htpasswdfile.".lock");
}
********************************************************************
Cameron Just
Web Development ( Information Technology Services )
University of Queensland
Ph 3365 7412
******************************************************************** 

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