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Date: Sat, 20 Oct 2001 07:50:25 -0700 (PDT)
From: Colin Percival <cperciva@sfu.ca>
To: freebsd-gnats-submit@FreeBSD.org
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Subject: bin/31387: When getuid()=0, mailwrapper should drop priviledges
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>Number:         31387
>Category:       bin
>Synopsis:       When getuid()=0, mailwrapper should drop priviledges
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Sat Oct 20 08:00:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Colin Percival
>Release:        4.4-RELEASE
>Organization:
>Environment:
>Description:
qmail (and possibly other MTAs), for security reasons, use suid mail queuing programs which are not owned by root.  This has the apparent advantage that a security hole will not lead to root compromise; however, since root normally sends mail on a daily basis, an attacker could gain root by overwriting the mail queuing program and removing the suid bit.  (Similar to the UUCP security hole).
>How-To-Repeat:
1. Install qmail.
2. Find a security hole in qmail-queue.
3. Exploit the hole with code which overwrites qmail-queue with your favorite trojan and then removes the suid bit.
4. Wait until `periodic daily` sends an email from uid 0.
>Fix:
If mailwrapper(8) is run by root, it should drop priviledges, either to 'nobody', or ideally to a user specified in /etc/mail/mailer.conf

>Release-Note:
>Audit-Trail:
>Unformatted:

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