Re: [BackupPC-users] PackupPC CGI interface and Plesk

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Les Mikesell wrote:

>> -r-sr-x---  1 backuppc psaserv 3912 Jun  7 11:48 BackupPC_Admin
>>
>> I can execute this as user backuppc, apache and root, but still it's
>> not working when I access it through a browser. I'm slowly starting
>> to go nuts from this...
>
> Is there a more informative error in the httpd error_log now?

No. I get this in my browser window:

----
500 Internal Server Error

The server encountered an internal error or misconfiguration and was  
unable to complete your request.

Please contact the server administrator, root@localhost and inform  
them of the time the error occurred, and anything you might have done  
that may have caused the error.

More information about this error may be available in the server  
error log.
----

And in error_log I find:

----
[Thu Jun 08 15:30:17 2006] [error] [client xxx.xxx.xxx.xxx] Premature  
end of script headers: BackupPC_Admin
----

That's all. When I reload the page I just get another one of those.

> A brute-force way to debug is to 'strace -p ' one of the httpd
> process id's, then hit the page until that process handles it,
> then look for failed systems calls where you might be able
> to see what file it is trying to access.

I didn't find anything this way. I only keep hitting traces of the  
404 error served for the favicon.ico. However, I thought of one more  
thing. I believe Plesk uses suexec for perl scripts. In the  
httpd.include for the vhost (generated by Plesk) I find:

SuexecUserGroup         lemonbitbackup psacln

Could this maybe override the setuid on BackupPC_Admin? In /var/log/ 
httpd/suexec_log I find:

[2006-06-08 15:57:52]: uid: (10011/lemonbitbackup) gid: (10001/10001)  
cmd: BackupPC_Admin
[2006-06-08 15:57:52]: file is either setuid or setgid: (/var/www/ 
vhosts/backup.lemonbit.nl/cgi-bin/BackupPC_Admin)

Could it be that that SuexecUserGroup directive somehow overrides the  
setuid bit on BackupPC_Admin?

Thanks for the great help so far,

Nils Breunese.