Date: Wed, 14 Nov 2012 00:19:39 -0700 From: Kurt Seiifried <kseifried@...hat.com> To: oss-security@...ts.openwall.com Subject: Re: Gajim fails to handle invalid certificates -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 11/10/2012 09:02 PM, y33t wrote: > Gajim does not seem to properly handle invalid/broken/expired > certificates. The _ssl_verify_callback function in tls_nb.py is > called by OpenSSL for every certificate in the certificate chain > (CA first, server certificate last) but always return True whether > an error was encountered or not. > > This forces OpenSSL to verify each certificate until none is left, > at which points it will call _ssl_verify_callback one last time > with an error number of 0. > > (This behavior is documented here: man 3 SSL_CTX_set_verify "If > verify_callback returns 1, the verification process is continued. > If verify_callback always returns 1, the TLS/SSL handshake will not > be terminated with respect to verification failures and the > connection will be established." And can be observed in function > crypto/x509/x509_vfy.c:internal_verify() in OpenSSL source code.) > > _ssh_verify_callback only stores the last error code, which always > is 0 unless an error was encountered in the deepest level of the > chain (the CA), so gajim will not warn as long as the CA is > recognized. > > > (...) > > This problem goes beyond expired certificates. It is also possible > to edit any existing and valid server certificate by changing the > CN manually. The certificate's signature will be become invalid and > OpenSSL will detect it and return errnum 7 ("Certificate signature > failure") but gajim will not warn and will proceed with the > connection anyway... > > > References: https://trac.gajim.org/ticket/7252 So do we consider this to be an OpenSSL issue of gajim? I'm sure gajim is not the only program that does something like this. - -- Kurt Seifried Red Hat Security Response Team (SRT) PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iQIcBAEBAgAGBQJQo0YLAAoJEBYNRVNeJnmTu3MQAI3+hlMRTPjdJzUnm/ymKK6N pqlerX9VVxyHWuW8pPqTZqAUpENLMErHTaNEPp2bLYv63zYvmibKcGMqwH4s/rrM SvaxFrlZxJvaw8vCx5c046lDiH5DhjhUkQW/kriR7zdXzvxDwt/ZyfLu92LSQ7VR ahoEYcyTZEEBZpi11ZyPt6N2iqeHRpngMXFtCztiBcyMTzKiscQ9gwgGSVOe8Owg WopP35XgaxwohzIgzV4yF7ydff+/fZ/TFY2Y5Wl2iXs9LzgwHxVftfjVuoAI9A0q amYG15i2BfrHzkqqToenAJv/mrraGUg7972rgDGNayU+DQr3IllaY4kSa711rB+J vK6TWbQT5nIEnOCxsCHJRlrIAZfI727dvBPr7gapIafYw2EYInRHkfRJIwRVggAt zwYDEW8cEkGnkUxg85OGJhPUU8uVVa9oKOjdDCeaGLhdYYC4j49kRJefRHX4sUHa OPhJF61aeZOTR7q39gbdmjYerkrbW2XDwo/18aM8Brf6Q0hSPyq380D2/1Fh4cRb HHsmWqPTP7S/16jUN9oePNR1/lj2u/kz+GlQlyfoNoXT2gknLOeRnVGnvofUDT4U 81qjpbdecoLCKJyHWMjQ1WCLnm21mu8FQTTxBfjOoj0lAbFcZH4Eps/VZBLWFj0N EZZnSNg788Lgek8lxl09 =2ckv -----END PGP SIGNATURE-----
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