Clarify CBS/CBB with respect to high tag number form.

We may need to implement high tag number form someday. CBS_get_asn1 has
an unsigned output to allow for this, but CBB_add_asn1 takes a uint8_t
(I think this might be my fault). Fix that which also fixes a
-Wconversion warning.

Simply leaving room in tag representation will still cause troubles
because the class and constructed bits overlap with bits for tag numbers
above 31. Probably the cleanest option would be to shift them to the top
3 bits of a u32 and thus not quite match the DER representation. Then
CBS_get_asn1 and CBB_add_asn1 will internally munge that into the DER
representation and consumers may continue to write things like:

   tag_number | CBS_ASN1_CONTEXT_SPECIFIC

I haven't done that here, but in preparation for that, document that
consumers need to use the values and should refrain from assuming the
correspond to DER.

Change-Id: Ibc76e51f0bc3b843e48e89adddfe2eaba4843d12
Reviewed-on: https://boringssl-review.googlesource.com/10502
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
3 files changed
tree: e50a56e8ef1cd6561f4d6e05ebf51573cc3bfc3d
  1. .github/
  2. crypto/
  3. decrepit/
  4. fuzz/
  5. include/
  6. infra/
  7. ssl/
  8. third_party/
  9. tool/
  10. util/
  11. .clang-format
  12. .gitignore
  13. API-CONVENTIONS.md
  14. BUILDING.md
  15. CMakeLists.txt
  16. codereview.settings
  17. CONTRIBUTING.md
  18. FUZZING.md
  19. INCORPORATING.md
  20. LICENSE
  21. PORTING.md
  22. README.md
  23. 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.

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