Simplify RSA key exchange padding check.

This check was fixed a while ago, but it could have been much simpler.

In the RSA key exchange, the expected size of the output is known, making the
padding check much simpler. There isn't any use in exporting the more general
RSA_message_index_PKCS1_type_2. (Without knowing the expected size, any
integrity check or swap to randomness or other mitigation is basically doomed
to fail.)

Verified with the valgrind uninitialized memory trick that we're still

Also update rsa.h to recommend against using the PKCS#1 v1.5 schemes.

Thanks to Ryan Sleevi for the suggestion.

Change-Id: I4328076b1d2e5e06617dd8907cdaa702635c2651
Reviewed-by: Adam Langley <>
3 files changed
tree: fae576431fde62f609d3e1523dd2475966b207e6
  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.