This guarantees that we never read beyond the first record, even if the
first record is empty. Between removing SSL_set_read_ahead and DTLS
enforcing record boundaries, this means the buffer need never memmove
data.
The memmove isn't really much of a burden and we can probably just put
SSL_set_read_ahead back after the cleanup if desired. But while the
non-existant read_ahead is off, we should avoid reading more than needed.
(Also the current memmove logic is completely wrong for TLS. Checking
align != 0 doesn't make sense. The real reason to memmove is that the
next record may still be full size. So now line 209 of s3_pkt.c should
*actually* be unreachable.)
SSL_R_HTTPS_PROXY_REQUEST detection is now slightly less accurate, but
OpenSSL was already not parsing HTTP completely. We could asynchronously
read the extra 3 bytes once the first 5 match, but that seems
unnecessary. (Shall we just get rid of all these HTTP detectors? The
only consumer of those error codes is some diagnostics logic.)
BUG=468889
Change-Id: Ie3bf148ae7274795e1d048d78282d1d8063278ea
Reviewed-on: https://boringssl-review.googlesource.com/5714
Reviewed-by: Adam Langley <agl@google.com>
894f48c6b3