Handle CBB_cleanup on child CBBs more gracefully.

Child and root CBBs share a type, but are different kinds of things. C++
programmers sometimes mistakenly believe they should use ScopedCBB for
everything. This mostly works because we NULL cbb->child->base on flush,
making CBB_cleanup a no-op. This zeroing also skips the assert in
CBB_cleanup. (If we ran it unconditionally, CBB_zero + CBB_cleanup would
not work.)

However, if a CBB operation fails and a function returns early, the
child CBB is not cleared. ScopedCBB will then call CBB_cleanup which
trips the assert but, in release build, misbehaves.

Run the assert unconditionally and, when the assert fails, still behave
well. To make this work with CBB_zero, negate is_top_level to is_child,
so a flushed child CBB and a (presumably) root CBB in the zero state are

Update-Note: Code that was using CBB wrong may trip an assert in debug builds.
Change-Id: Ifea7759e1d0331f2e727c59bbafa355d70fb9dba
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/35524
Reviewed-by: Adam Langley <agl@google.com>
2 files changed
tree: 837d0737ba03a96f871d9967c593414842517b3b
  1. .clang-format
  2. .github/
  3. .gitignore
  6. BUILDING.md
  7. CMakeLists.txt
  9. FUZZING.md
  12. PORTING.md
  13. README.md
  14. STYLE.md
  15. codereview.settings
  16. crypto/
  17. decrepit/
  18. fipstools/
  19. fuzz/
  20. go.mod
  21. include/
  22. sources.cmake
  23. ssl/
  24. third_party/
  25. tool/
  26. 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: