If gnutls_bye() fails with a fatal error, we would reattempt it again
and again, even though this may then go on to e.g. cause a segmentation
fault.
Now we just keep retrying if it was interrupted, in line with the other
backends, up to a maximum of 3 retries.
Yeah, I know, I said I was happy with it and wouldn't be changing it.
However, the new GNUTLS backend I'm working on has prompted this.
E.g. MbedTLS error codes and GNUTLS error codes are both negative ints,
but GNUTLS will not tolerate positive input values. Let's treat
both backends the same.
* Move file/data assignments to the top of the function
* Don't attempt to set a hardcoded P-384 ECDH key if we have the new
SSL_CTX_set1_curves_list() function (OpenSSL 1.0.2+)
* Rename variables consistent with other backends and wrap the function
arguments.
* Disable OpenSSL's disabling of TLS 1/n-1 record splitting.
In other words, enable TLS 1/n-1 record splitting.
* Other misc cleanups.
OpenSSL is perfectly capable of having a single context that is shared
by both client and server sessions alike; one simply needs to call
SSL_set_accept_state (for server) or SSL_set_connect_state (for client)
before attempting handshaking.
OpenSSL uses `unsigned long' type for its error codes, so that's
what (lib)ratbox used to store the error values.
Unfortunately, MbedTLS uses int, and its error codes are negative.
On machines where `int' and `long' are the same size, this could
result in storing a truncated error code.
This patch inverts the sign bit on error codes and then casts them
to unsigned long for storage.
MbedTLS itself (specifically, `mbedtls_strerror()') will function
properly with negative or positive input values. It even converts
negative input values to positive before checking them against the
list of known error codes!
See also: `library/error.c' in the MbedTLS 2.1+ distribution.
All 3 backends (MbedTLS, OpenSSL, GNUTLS) are going to have the same
function name for returning error strings. This will help to reduce the
diffs between them.
