Validate DH public keys for RFC 5114 groups.

This is CVE-2016-0701 for OpenSSL, reported by Antonio Sanso. It is a no-op for
us as we'd long removed SSL_OP_DH_SINGLE_USE and static DH cipher suites. (We
also do not parse or generate X9.42 DH parameters.)

However, we do still have the APIs which return RFC 5114 groups, so we should
perform the necessary checks in case later consumers reuse keys.

Unlike groups we generate, RFC 5114 groups do not use "safe primes" and have
many small subgroups. In those cases, the subprime q is available. Before using
a public key, ensure its order is q by checking y^q = 1 (mod p). (q is assumed
to be prime and the existing range checks ensure y is not 1.)

(Imported from upstream's 878e2c5b13010329c203f309ed0c8f2113f85648 and
75374adf8a6ff69d6718952121875a491ed2cd29, but with some bugs fixed. See

Change-Id: Ib18c3e84819002fa36a127ac12ca00ee33ea018a
Reviewed-by: Adam Langley <>
3 files changed
tree: 372333002675556770acf64c2d74adc981d57f22
  1. .clang-format
  2. .gitignore
  4. CMakeLists.txt
  10. codereview.settings
  11. crypto/
  12. decrepit/
  13. fuzz/
  14. include/
  15. ssl/
  16. tool/
  17. util/


BoringSSL is a fork of OpenSSL that is designed to meet Google's needs.

Although BoringSSL is an open source project, it is not intended for general use, as OpenSSL is. We don't recommend that third parties depend upon it. Doing so is likely to be frustrating because there are no guarantees of API or ABI stability.

Programs ship their own copies of BoringSSL when they use it and we update everything as needed when deciding to make API changes. This allows us to mostly avoid compromises in the name of compatibility. It works for us, but it may not work for you.

BoringSSL arose because Google used OpenSSL for many years in various ways and, over time, built up a large number of patches that were maintained while tracking upstream OpenSSL. As Google's product portfolio became more complex, more copies of OpenSSL sprung up and the effort involved in maintaining all these patches in multiple places was growing steadily.

Currently BoringSSL is the SSL library in Chrome/Chromium, Android (but it's not part of the NDK) and a number of other apps/programs.

There are other files in this directory which might be helpful:

  • how to port OpenSSL-using code to BoringSSL.
  • how to build BoringSSL
  • rules and guidelines for coding style.
  • include/openssl: public headers with API documentation in comments. Also available online.
  • information about fuzzing BoringSSL.