SSL_set_fd should create socket BIOs, not fd BIOs.

In OpenSSL, they create socket BIOs. The distinction isn't important on UNIX.
On Windows, file descriptors are provided by the C runtime, while sockets must
use separate recv and send APIs. Document how these APIs are intended to work.

Also add a TODO to resolve the SOCKET vs int thing. This code assumes that
Windows HANDLEs only use the bottom 32 bits of precision. (Which is currently
true and probably will continue to be true for the foreseeable future[*], but
it'd be nice to do this right.)

Thanks to Gisle Vanem and Daniel Stenberg for reporting the bug.

[*] Both so Windows can continue to run 32-bit programs and because of all the
random UNIX software, like OpenSSL and ourselves, out there which happily
assumes sockets are ints.

Change-Id: I67408c218572228cb1a7d269892513cda4261c82
Reviewed-by: David Benjamin <>
3 files changed
tree: 75f68ef2ea91c766e6ca2bd9cc1aaa1fdf87c574
  1. .clang-format
  2. .gitignore
  4. CMakeLists.txt
  11. codereview.settings
  12. crypto/
  13. decrepit/
  14. fuzz/
  15. include/
  16. ssl/
  17. tool/
  18. 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: