Make ec_GFp_simple_cmp constant-time.

We need a constant-time point equality for two reasons. First, although
multiplication results are usually public, their Jacobian Z coordinates
may be secret, or at least are not obviously public. Second, more
complex protocols will sometimes manipulate secret points, notably
PMBTokens.

While here I've renamed the inner function to points_equal without the
flipped return value, to be less confusing.

Update-Note: This does mean that we pay a 6M+2S Jacobian comparison
where comparing two publicly affine points should cost no field
operations at all. Code which compares two EC public keys for equality
will be slightly slower. I wouldn't expect this to matter (if you
actually use the public keys, you'll pay much much more) If it does, we
can restore this optimization by keeping better track of affine vs.
Jacobian forms. See https://crbug.com/boringssl/326.

Bug: 326, chromium:1014199
Change-Id: I67c9a56bc9b66f30c0b500a29e8bf90427d89061
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/40665
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
4 files changed
tree: db7d5c217348cb6b9466979d19cd8b3350ab2968
  1. .github/
  2. crypto/
  3. decrepit/
  4. fuzz/
  5. include/
  6. ssl/
  7. third_party/
  8. tool/
  9. util/
  10. .clang-format
  11. .gitignore
  12. API-CONVENTIONS.md
  13. BREAKING-CHANGES.md
  14. BUILDING.md
  15. CMakeLists.txt
  16. codereview.settings
  17. CONTRIBUTING.md
  18. FUZZING.md
  19. go.mod
  20. INCORPORATING.md
  21. LICENSE
  22. PORTING.md
  23. README.md
  24. sources.cmake
  25. STYLE.md
README.md

BoringSSL

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.

Project links:

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