Fix error-handling convention in x509_vfy.c and avoid -1 returns

This CL makes two changes. First, it removes the couple of places where
X509_verify_cert may return -1 and switches to our standard 0/1 return
convention. The only -1 cases were get_issuer returning < 0 and the
caller error cases at the top. It seems implausible that any caller
would care about the latter and the former is actually impossible.
get_issuer never returns < 0.

Second, OpenSSL's original implementation did not follow the usual
error-handling convention. The usual convention is that there's a
cleanup epilog, and a variable (usually called 'ret' or 'ok') that
stores the return value. This variable is initialized in the failure
case and may only be modified immediately before a goto or when falling
through to the epilog. This allows error conditions to simply 'goto err'
and rely on the variable's value.

X509_verify_cert instead overwrite 'ok' throughout the function, which
is tedious and error-prone. Fix this to follow the usual convention.
Also remove uses of this pattern when there isn't anything to cleanup.

As part of this cleanup, we fix a near miss: the three cert_self_signed
call sites did not correctly account for this non-standard pattern.
Fortunately (as demonstrated by existing unit tests), the first call
site is fine. The remainder are only called on "trusted" certificates
from the X509_STORE. An attacker with control over trust anchors already
controls certificate verification, so this is moot. Moreover, all such
certificates first go through get_issuer, which calls X509_check_issued,
which already handles EXFLAG_INVALID, so the error condition was
redundant.

Update-Note: X509_verify_cert no longer returns -1 on some error
conditions, only zero.

Change-Id: I88d5e845cd4cb8f48d5c5df6782bf6730c682642
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/65067
Auto-Submit: David Benjamin <davidben@google.com>
Commit-Queue: Bob Beck <bbe@google.com>
Reviewed-by: Bob Beck <bbe@google.com>
2 files changed
tree: 9d1fdd995598c3de8f24e9e4241053081a57eec4
  1. .github/
  2. cmake/
  3. crypto/
  4. decrepit/
  5. fuzz/
  6. include/
  7. pki/
  8. rust/
  9. ssl/
  10. third_party/
  11. tool/
  12. util/
  13. .clang-format
  14. .gitignore
  15. API-CONVENTIONS.md
  16. BREAKING-CHANGES.md
  17. BUILDING.md
  18. CMakeLists.txt
  19. codereview.settings
  20. CONTRIBUTING.md
  21. FUZZING.md
  22. go.mod
  23. go.sum
  24. INCORPORATING.md
  25. LICENSE
  26. PORTING.md
  27. README.md
  28. SANDBOXING.md
  29. sources.cmake
  30. 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: