Add an option to disable NPN on a per-SSL basis.

Right whether NPN is advertised can only be configured globally on the SSL_CTX.
Rather than adding two pointers to each SSL*, add an options bit to disable it
so we may plumb in a field trial to disable NPN.

Chromium wants to be able to route a bit in to disable NPN, but it uses SSL_CTX
incorrectly and has a global one, so it can't disconnect the callback. (That
really needs to get fixed. Although it's not clear this necessarily wants to be
lifted up to SSL_CTX as far as Chromium's SSLClientSocket is concerned since
NPN doesn't interact with the session cache.)


Change-Id: I49c86828b963eb341c6ea6a442557b7dfa190ed3
Reviewed-by: Adam Langley <>
6 files changed
tree: f5269e36d92f7fc29f00704565d5bb3c845891c8
  1. .clang-format
  2. .gitignore
  4. CMakeLists.txt
  9. codereview.settings
  10. crypto/
  11. decrepit/
  12. include/
  13. ssl/
  14. tool/
  15. 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.