Re: [BackupPC-users] CGI question

[Johnny L. W. <jo...@ma...>]

On Mon, 26 Aug 2002, Craig Barratt wrote:

> > change suggested in an earlier thread. Then, I get a page with a Status/PC
> > Summary/etc on the left side. There's a green bar across the top that says
> > "Error:Wrong user: my userid is 48, instead of 541 (backuppc)"
> > 
> > Now then, my permissions on BackupPC_Admin are as follows:
> > 
> > -r-sr-xr-x    1 backuppc bacuppc     83096 Aug 23 13:59 BackupPC_Admin
> > 
> > And permissions on config.pl have also been changed so I could get it
> > readable enough to allow me to see the error messages generated by
> > BackupPC_Admin. 
> > 
> > NOW for the freaky part:
> > 
> > [root@hylafax httpd]# ls -l /bin | grep perl
> > lrwxrwxrwx    1 root     root           13 Aug 16 13:35 perl ->
> > /usr/bin/perl
> > -rws--x--x    1 root     root       790752 Aug 23 14:10 sperl5.6.0
> > [root@hylafax httpd]#
> > 
> > There's also a copy of sperl5.6.0 in /usr/bin. Still, I'm getting errors
> > about being the wrong user. What's the deal?
> 
> Ok, there is some problem with setuid perl scripts on your machine.  And
> you are not alone: several other users have had similar problems.  But
> lots of other users have not.
> 
> One solution is to switch to mod_perl: by running apache as user backuppc
> in the first place you avoid the need for setuid.

In my current environment, this would be all but impossible. The machine
I'm setting this up on is mission-critical and I can't just change the
webserver out willy-nilly. If there was a minor problem that took the
regular apache down for 10 minutes, I'd hear about it from at least 3
managers. :)

> But I would like to get to the bottom of this.
> 
> Please create a short test program, testsetuid, that looks like this:
> 
>     #!/bin/perl
> 
>     printf("My userid is $> (%s)\n", (getpwuid($>))[0]);
> 
> then chown it to backuppc and chmod u+s:
> 
>     root# chown backuppc testsetuid
>     root# chmod u+s testsetuid
>     root# ls -l testsetuid
>     -rwsr-xr-x    1 backuppc  wheel          76 Aug 26 09:46 testsetuid*
> 

Ok. Copied and pasted the script exactly from this email into a file, and
did this:

[root@hylafax backuppc]# chown backuppc:backuppc testsetuid
[root@hylafax backuppc]# chmod u+s testsetuid
[root@hylafax backuppc]# chmod u+x testsetuid
[root@hylafax backuppc]# ls -l testsetuid
-rwsr--r--    1 backuppc backuppc       68 Aug 26 13:09 testsetuid

> Now run this program as a normal user.
> 
>   - What uid does it print?

[root@hylafax backuppc]# ./testsetuid
My userid is 0 (root)
[root@hylafax backuppc]# su jeff
[jeff@hylafax backuppc]$ ./testsetuid
bash: ./testsetuid: Permission denied
[jeff@hylafax backuppc]$

Therefore, I'll assume you meant something a little more like:
[root@hylafax backuppc]# chmod a+s testsetuid
[root@hylafax backuppc]# chmod a+x testsetuid
[root@hylafax backuppc]# su jeff
[jeff@hylafax backuppc]$ ls -l testsetuid
-rwsr-sr-x    1 backuppc backuppc       68 Aug 26 13:09 testsetuid
[jeff@hylafax backuppc]$ ./testsetuid
My userid is 542 (jeff)
[jeff@hylafax backuppc]$

>   - If it doesn't print backuppc, try changing the first line of the script
>     to be:
> 
> 	#!/usr/bin/sperl5.6.0

[Edit stuff]
[root@hylafax backuppc]# ls -l testsetuid
-rwsr-sr-x    1 backuppc backuppc       74 Aug 26 13:16 testsetuid
[root@hylafax backuppc]# ./testsetuid
My userid is 541 (backuppc)
[root@hylafax backuppc]# su jeff
[jeff@hylafax backuppc]$ ./testsetuid
My userid is 541 (backuppc)
[jeff@hylafax backuppc]$


>     If this works, then change the first line of BackupPC_Admin to the
>     same thing and see if it now works.

[Edit Stuff]
[root@hylafax cgi-bin]# ls -l BackupPC_Admin
-r-sr-sr-x    1 backuppc backuppc    83102 Aug 26 13:17 BackupPC_Admin

Ran it from the web, got an error about the backuppc daemon not
running. Lemme go start that and try again....

    *  The server's PID is 29147 on host hylafax.internal.booksys.com,
version 1.5.0, started at 8/26 13:31.
    * This status was generated at 8/26 13:31.
    * PCs will be next queued at 8/26 14:00.
    * Other info:
          o 0 pending backup requests from last scheduled wakeup,
          o 0 pending user backup requests,
          o 0 pending command requests,
          o Pool is 0.00GB comprising 0 files and 1 directories (as of
8/20 22:30),
          o Pool hashing gives 0 repeated files with longest chain 0,
          o Nightly cleanup removed 0 files of size 0.00GB (around 8/20
22:30),
o Pool file system was recently at 61% (8/20 22:30), today's max is 61%
(8/20 22:30) and yesterday's max was 61%


>   - If the original test does print backuppc, then it looks like it is
>     something specific to setuid cgi scripts in apache.

I'm not exactly sure what we've discovered here, but it looks like the web
interface is working now. :)

--Me