OpenSSL ASN.1 vulnerability: sshd not affected

Damien Miller djm at
Thu Apr 19 22:19:10 EST 2012


Tavis Ormandy found some bugs in OpenSSL's ASN.1 and buffer code that
can be exploited to cause a heap overflow:

Fortunately OpenSSH's sshd is not vulnerable - it has avoided the use
of ASN.1 parsing since 2002 when Markus wrote a custom RSA verification
function (openssh_RSA_verify):;content-type=text%2Fplain

That's now eight exploitable bugs that this change has saved us from.
It's a good lesson in how excising even a relatively small amount of
complex attack surface can make a substantial difference to the security
of an application.

This gloating only applies to sshd though - private key loading still
uses the affected OpenSSL code, so if you are somehow allowing untrusted
users to supply private keys to ssh, ssh-keygen or ssh-add in a
privileged context then you should apply the OpenSSL fixes forthwith.


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