While allocating near INT_MAX BIGNUMs or stack frames would never happen, we
should properly handle overflow here. Rewrite it to just be a STACK_OF(BIGNUM)
plus a stack of indices. Also simplify the error-handling. If we make the
errors truly sticky (rather than just sticky per frame), we don't need to keep
track of err_stack and friends.
Thanks to mlbrown for reporting the integer overflows in the original
implementation.
Bug: chromium:942269
Change-Id: Ie9c9baea3eeb82d65d88b1cb1388861f5cd84fe5
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/35328
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
4ca8d131d3