paths and permissions

[Tom Allison]

Dave Lovelace wrote:
> David Relson wrote:
> 
>>Hi Jesse,
>>
>>Sounds right.  Since that posting, I learned that procmail runs suid. 
>>It's been pointed out that that's potentially dangerous since users can
>>have their own .procmailrc files.
>>
>>David
>>
> 
> Anything that runs SUID root is in principle insecure, but the software's
> authors attempt to wall off the sections where it's actually running as
> root.  I don't know procmail's code, but I'd presume that by the time it's
> running the user's .procmailrc it's running as the user.
> 

man procmail:
        If no rcfiles and no -p have been specified on the command
        line,  procmail  will, prior to reading $HOME/.procmailrc,
        interpret  commands  from  /etc/procmailrc  (if  present).
        Care must be taken when creating /etc/procmailrc, because,
        if circumstances permit, it will  be  executed  with  root
        privileges  (contrary  to  the  $HOME/.procmailrc  file of
        course).

procmail only runs root if you have a file in /etc/procmailrc.
All files that are ~/.procmailrc are executed under the permissions of 
the user.  Fewer and fewer distros provide a /etc/procmailrc file.


 From man procmailrc, the environment variables that may be affected by 
the '-p' option include:

        UMASK       The name says it all (if it doesn't, then for­
                    get  about this one :-).  Anything assigned to
                    UMASK is taken as an  octal  number.   If  not
                    specified,  the umask defaults to 077.  If the
                    umask permits o+x, all the mailboxes  procmail
                    delivers  to directly will receive an o+x mode
                    change.  This can be used to check if new mail
                    arrived.

        DROPPRIVS   If  set to `yes' procmail will drop all privi­
                    leges it might have had (suid or sgid).   This
                    is  only  useful if you want to guarantee that
                    the bottom half of the /etc/procmailrc file is
                    executed on behalf of the recipient.