+1. Thanks! Which tests?
On Wednesday, April 4, 2018, Christian Heimes <christ...@python.org> wrote: > Hi, > > I like to share the story of a critical security bug with you. Contrary > to other issues in TLS/SSL, it's a story with happy ending. Nobody was > harmed. The bug was fixed before it affected the general population. > > > Introduction > ------------ > > Python's ssl.match_hostname() function was a source of several CVEs and > other security bugs. After a long struggle, I decided to drop support > for old OpenSSL releases and uses a new OpenSSL method to offload host > name verification to OpenSSL. The improvement [1] eventually landed in > Python 3.7. Nowadays OpenSSL verifies host name or IP address during the > TLS/SSL handshake. > > Later I discovered that LibreSSL <= 2.6 did not have > X509_VERIFY_PARAM_set1_host() [2]. We had to temporarily suspend support > for LibreSSL. About two months later, LibreSSL caught up and released > version 2.7.0 with support for the function. > > > The bug > ------- > > One day after the release of LibreSSL 2.7.0, I started to port Python > 3.7 to LibreSSL. In matter of minutes I got the ssl module to compile > and work with LibreSSL. All tests were passing -- except for negative > the host name verification tests. LibreSSL was accepting all invalid > host names as correct! Python's vigorous test suite had discovered a > critical security bug in LibreSSL. > > It turned out that LibreSSL copied the implementation of > X509_VERIFY_PARAM_set1_host(param, name, namelen) from BoringSSL and the > documentation from OpenSSL. BoringSSL's implementation didn't support > the special case of 0 as namelen parammeter. OpenSSL supports namelen = > 0, which is interpreted as namelen=strlen(name). It is documented in > OpenSSL's man page and was even recommended on OpenSSL's wiki as > preferred way. > > > Happy Ending > ------------ > > So I got in contact with LibreSSL's security team and BoringSSL's > security team [3]. Less than a day later, both libraries released fixes > for the bug [4]. Mitre has assigned CVE-2018-8970 [5] to the bug. > Disaster averted! > > BoringSSL's security issue [3] contains more information. Adam Langley > lifted the restriction about an hour ago. > > I like to thank Bob Beck (LibreSSL), Adam Langley (Google) and David > Benjamin (Google) for their assistance and cooperation. > > Regards, > Christian > > [1] https://bugs.python.org/issue31399 > [2] https://github.com/libressl-portable/portable/issues/381 > [3] https://bugs.chromium.org/p/chromium/issues/detail?id=824799 > [4] https://www.libressl.org/releases.html > [5] https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-8970 > > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/ > wes.turner%40gmail.com >
_______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
