This improves the error-handling and uses CBB instead. It also resolves
a pile of -Wshorten-64-to-32 warnings. It also removes some of the calls
to ASN_put_object within the library.
The parsing uses NUL-terminated strings a bit because several of the
functions called at the end actually rely on the string being
NUL-terminated. Rather than pipe through (ptr, len) versions through
everything, I just used const char * or CBS based on whether the string
could be assumed to have a trailing NUL.
As part of this, I've made it reject [UNIVERSAL 0], matching all our
parsers. Rejecting that value means, since we don't have a nice
Option<T> in C, we can use zero in all the recursive calls to mean "no
implicit tag".
This does tighten the forms allowed for UTCTime a bit. I've disabled
allow_timezone_offset, while crypto/asn1 broadly still allows it. The
reasoning is this is code for constructing new certificates, not
consuming existing ones. If anything is calling this (hopefully not!) to
accidentally generate an invalid UTCTime, it should be fixed.
Update-Note: This code is reachable from the deprecated, string-based
X.509 extensions API. I've added tests for this, so it should behave
generally compatibly, but if anything changes for a caller using these
APIs, this CL is the likely cause. (NB: No one should be using these
APIs. They're fundamentally prone to string injection vulnerabilities.)
Bug: 516
Change-Id: I87f95e01ffbd22c4487d82c89ac098d095126cc1
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/56166
Reviewed-by: Bob Beck <bbe@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
David Benjamin