Make BN_mod_inverse() deal with repeated arguments

BN_nnmod() can deal with the situation that the first and the second
arguments are the same, but it cannot deal with the first and the
second argument being equal. In that situation, if BN_mod(x, y, x, ctx)
results in a negative x, then the result of BN_nnmod() is zero. This
breaks the strange BN_mod_inverse(m, a, m, ctx).

Reported by Guido Vranken in

Change-Id: I8584720660f214f172b3b33716a5e3b29e8f2fd8
Reviewed-by: Bob Beck <>
Reviewed-by: David Benjamin <>
Commit-Queue: David Benjamin <>
2 files changed
tree: 6a059a2214de31509ca1bbb62537cbf3b6eebcef
  1. .github/
  2. cmake/
  3. crypto/
  4. decrepit/
  5. fuzz/
  6. include/
  7. rust/
  8. ssl/
  9. third_party/
  10. tool/
  11. util/
  12. .clang-format
  13. .gitignore
  17. CMakeLists.txt
  18. codereview.settings
  21. go.mod
  22. go.sum
  28. sources.cmake


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.

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