Significant OpenSSH Vulnerability

    Date24 Jun 2002
    CategoryCryptography
    2306
    Posted ByAnthony Pell
    In an email addressed to many in the security community today, including LinuxSecurity, Theo de Raadt, lead developer for OpenBSD and OpenSSH, announced an OpenSSH vulnerability. The details of the vulnerability have not yet been made public, but has acknowledged that it is remotely exploitable. Included below are details on what Linux users can do to mitigate the risks until vendors release their updated versions.. . . In an email addressed to many in the security community today, including LinuxSecurity, Theo de Raadt, lead developer for OpenBSD and OpenSSH, announced an OpenSSH vulnerability. The details of the vulnerability have not yet been made public, but has acknowledged that it is remotely exploitable. Included below are details on what Linux users can do to mitigate the risks until vendors release their updated versions.

     Subject: Upcoming OpenSSH vulnerability Date: Mon, 24 Jun 2002 15:00:10 -0600 From: Theo de Raadt   There is an upcoming OpenSSH vulnerability that we're working on with ISS.  Details will be published early next week.  However, I can say that when OpenSSH's sshd(8) is running with priv seperation, the bug cannot be exploited.  OpenSSH 3.3p was released a few days ago, with various improvements but in particular, it significantly improves the Linux and Solaris support for priv sep.  However, it is not yet perfect.  Compression is disabled on some systems, and the many varieties of PAM are causing major headaches.  However, everyone should update to OpenSSH 3.3 immediately, and enable priv seperation in their ssh daemons, by setting this in your /etc/ssh/sshd_config file:  	UsePrivilegeSeparation yes  Depending on what your system is, privsep may break some ssh functionality.  However, with privsep turned on, you are immune from at least one remote hole.  Understand?  3.3 does not contain a fix for this upcoming bug.  If priv seperation does not work on your operating system, you need to work with your vendor so that we get patches to make it work on your system.  Our developers are swamped enough without trying to support the myriad of PAM and other issues which exist in various systems. You must call on your vendors to help us.  Basically, OpenSSH sshd(8) is something like 27000 lines of code.  A lot of that runs as root.  But when UsePrivilegeSeparation is enabled, the daemon splits into two parts.  A part containing about 2500 lines of code remains as root, and the rest of the code is shoved into a chroot-jail without any privs.  This makes the daemon less vulnerable to attack.  We've been trying to warn vendors about 3.3 and the need for privsep, but they really have not heeded our call for assistance.  They have basically ignored us.  Some, like Alan Cox, even went further stating that privsep was not being worked on because "Nobody provided any info which proves the problem, and many people dont trust you theo" and suggested I "might be feeding everyone a trojan" (I think I'll publish that letter -- it is just so funny).  HP's representative was downright rude, but that is OK because Compaq is retiring him.  Except for Solar Designer, I think none of them has helped the OpenSSH portable developers make privsep work better on their systems. Apparently Solar Designer is the only person who understands the need for this stuff.  So, if vendors would JUMP and get it working better, and send us patches IMMEDIATELY, we can perhaps make a 3.3.1p release on Friday which supports these systems better.  So send patches by Thursday night please.  Then on Tuesday or Wednesday the complete bug report with patches (and exploits soon after I am sure) will hit BUGTRAQ.  Let me repeat: even if the bug exists in a privsep'd sshd, it is not exploitable.  Clearly we cannot yet publish what the bug is, or provide anyone with the real patch, but we can try to get maximum deployement of privsep, and therefore make it hurt less when the problem is published.  So please push your vendor to get us maximally working privsep patches as soon as possible!  We've given most vendors since Friday last week until Thursday to get privsep working well for you so that when the announcement comes out next week their customers are immunized.  That is nearly a full week (but they have already wasted a weekend and a Monday).  Really I think this is the best we can hope to do (this thing will eventually leak, at which point the details will be published).  Customers can judge their vendors by how they respond to this issue.  OpenBSD and NetBSD users should also update to OpenSSH 3.3 right away. On OpenBSD privsep works flawlessly, and I have reports that is also true on NetBSD.  All other systems appear to have minor or major weaknesses when this code is running.  
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