Bulletproof TLS Newsletter

Bulletproof TLS Newsletter is a free periodic newsletter bringing you commentary and news surrounding SSL/TLS and Internet PKI, designed to keep you informed about the latest developments in this space. Maintained by Hanno Böck.

OpenSSL recently released a security update fixing a bug in the certificate validation code. The SSL_check_chain() function can crash due to a NULL pointer dereference when an invalid signature algorithm is detected. This bug could be used to crash OpenSSL-based servers. Only relatively recent versions of OpenSSL 1.1.1 are affected (1.1.1d through 1.1.1f); the OpenSSL team has released version 1.1.1g with a fix for the bug.

Of note about the bug is that it has been detected with a new static code analyzer tool introduced by GCC. This feature will be part of the upcoming version 10 of GCC and can be tested with a Git build of the current GCC code.

David Malcom, a Red Hat developer who has developed the feature, has explained its details in a blog post. The -fanalyzer flag in GCC 10 allows for finding common bug classes via the compiler, with a first focus on double-free bugs.

While the bug found shows that this is a powerful feature that can find real security bugs, a discussion in the OpenSSL bug tracker also indicates that -fanalyzer creates difficult-to-analyze false positives. A common property of static code analysis is that it can produce false positives, and it is a challenge to keep the false positive rate low enough that you avoid getting too many false alarms while at the same time keep the tool useful.

Short news

• Microsoft released updated plans for disabling TLS 1.0 and 1.1 in Edge. Recently, Firefox reverted and delayed the deprecation due to COVID-19, as reported in our last newsletter.
• CAcert.org has an issue with certificate issuance. According to a blogpost from March 27, “Certificates are currently not created.” Fixing this requires access to the data center, which seems to be a problem due to COVID-19. As of the time of writing (April 26), the CAcert web page is using a certificate that expired on April 4. CAcert.org is a free certificate authority that is currently not included in any major certificate root store.
• At the RSA conference, Matt Caswell from OpenSSL gave an overview of the state of OpenSSL and FIPS certification.
• For the Netflix Tech Blog, Sekwon Choi wrote a blog post about the background and benchmarks of Netflix’s use of TLS 1.3.
• The EFF is announcing the end of the STARTTLS Everywhere project. STARTTLS Everywhere was a project to allow mail servers to verify certificates based on a static list. This was often seen as problematic due to potentially outdated data and scalability. MTA-STS and DANE are named as alternatives in the blog post.
• In a blog post, Let’s Encrypt explains the technical details of ASN.1, the technology that is used to encode X.509 certificates.
• For several days, the Identrust OCSP server produced errors. Identrust is the root certificate authority that signed the Let’s Encrypt intermediate certificate. As OCSP checks on intermediate certificates are not performed by most clients, the incident had little noticeable impact.
• OpenSSL has released an alpha release of its upcoming version 3.0.0.