Make sure that the error buffer is always initialized and simplify the
use of it to make the logic easier.

Bug: https://github.com/bagder/curl/issues/318
Reported-by: sneis

OPENSSL_load_builtin_modules does not exist in BoringSSL. Regression
from cae43a10

The symbol SSL3_MT_NEWSESSION_TICKET appears to have been introduced at
around openssl 0.9.8f, and the use of it in lib/vtls/openssl.c breaks
builds with older openssls (certainly with 0.9.8b, which is the latest
older version I have to try with).

This commit is several drafts squashed together. The changes from each
draft are noted below. If any changes are similar and possibly
contradictory the change in the latest draft takes precedence.

Bug: https://github.com/bagder/curl/issues/244
Reported-by: Chris Araman

%%
%% Draft 1
%%
- return 0 if len == 0. that will have to be documented.
- continue on and process the caches regardless of raw recv
- if decrypted data will be returned then set the error code to CURLE_OK
and return its count
- if decrypted data will not be returned and the connection has closed
(eg nread == 0) then return 0 and CURLE_OK
- if decrypted data will not be returned and the connection *hasn't*
closed then set the error code to CURLE_AGAIN --only if an error code
isn't already set-- and return -1
- narrow the Win2k workaround to only Win2k

%%
%% Draft 2
%%
- Trying out a change in flow to handle corner cases.

%%
%% Draft 3
%%
- Back out the lazier decryption change made in draft2.

%%
%% Draft 4
%%
- Some formatting and branching changes
- Decrypt all encrypted cached data when len == 0
- Save connection closed state
- Change special Win2k check to use connection closed state

%%
%% Draft 5
%%
- Default to CURLE_AGAIN in cleanup if an error code wasn't set and the
connection isn't closed.

%%
%% Draft 6
%%
- Save the last error only if it is an unrecoverable error.

Prior to this I saved the last error state in all cases; unfortunately
the logic to cover that in all cases would lead to some muddle and I'm
concerned that could then lead to a bug in the future so I've replaced
it by only recording an unrecoverable error and that state will persist.

- Do not recurse on renegotiation.

Instead we'll continue on to process any trailing encrypted data
received during the renegotiation only.

- Move the err checks in cleanup after the check for decrypted data.

In either case decrypted data is always returned but I think it's easier
to understand when those err checks come after the decrypted data check.

%%
%% Draft 7
%%
- Regardless of len value go directly to cleanup if there is an
unrecoverable error or a close_notify was already received. Prior to
this change we only acknowledged those two states if len != 0.

- Fix a bug in connection closed behavior: Set the error state in the
cleanup, because we don't know for sure it's an error until that time.

- (Related to above) In the case the connection is closed go "greedy"
with the decryption to make sure all remaining encrypted data has been
decrypted even if it is not needed at that time by the caller. This is
necessary because we can only tell if the connection closed gracefully
(close_notify) once all encrypted data has been decrypted.

- Do not renegotiate when an unrecoverable error is pending.

%%
%% Draft 8
%%
- Don't show 'server closed the connection' info message twice.

- Show an info message if server closed abruptly (missing close_notify).

Some servers will request a client certificate, but not require one.
This change allows libcurl to connect to such servers when using
schannel as its ssl/tls backend. When a server requests a client
certificate, libcurl will now continue the handshake without one,
rather than terminating the handshake. The server can then decide
if that is acceptable or not. Prior to this change, libcurl would
terminate the handshake, reporting a SEC_I_INCOMPLETE_CREDENTIALS
error.

Although OpenSSL 1.1.0+ deprecated SSLv23_client_method in favor of
TLS_client_method LibreSSL and BoringSSL didn't and still use
SSLv23_client_method.

Bug: https://github.com/bagder/curl/commit/49a6642#commitcomment-11578009


Reported-by:  <asavah@users.noreply.github.com>

- Try building a chain using issuers in the trusted store first to avoid
problems with server-sent legacy intermediates.

Prior to this change server-sent legacy intermediates with missing
legacy issuers would cause verification to fail even if the client's CA
bundle contained a valid replacement for the intermediate and an
alternate chain could be constructed that would verify successfully.

https://rt.openssl.org/Ticket/Display.html?id=3621&user=guest&pass=guest

ERR_error_string_n() was introduced in 0.9.6, no need to #ifdef anymore

Code for OpenSSL 0.9.4 serves no purpose anymore!

It was present for OpenSSL 0.9.5 code but we only support 0.9.7 or
later.

The existing callback served no purpose.

- Change fopen calls to use FOPEN_READTEXT instead of "r" or "rt"
- Change fopen calls to use FOPEN_WRITETEXT instead of "w" or "wt"

This change is to explicitly specify when we need to read/write text.
Unfortunately 't' is not part of POSIX fopen so we can't specify it
directly. Instead we now have FOPEN_READTEXT, FOPEN_WRITETEXT.

Prior to this change we had an issue on Windows if an application that
uses libcurl overrides the default file mode to binary. The default file
mode in Windows is normally text mode (translation mode) and that's what
libcurl expects.

Bug: https://github.com/bagder/curl/pull/258#issuecomment-107093055
Reported-by: Orgad Shaneh

SSLv23_client_method is deprecated starting in OpenSSL 1.1.0. The
equivalent is TLS_client_method.

https://github.com/openssl/openssl/commit/13c9bb3#diff-708d3ae0f2c2973b272b811315381557

Stop curl from failing when non-fatal alert is received during
handshake.  This e.g. fixes lots of problems when working with https
sites through proxies.

BoringSSL removed support for direct callers of SSL_CTX_callback_ctrl
and SSL_CTX_ctrl, so move to a way that should work on BoringSSL and
OpenSSL.

re #275

Also print the revocation reason if appropriate.

The symbol is fairly new.

Reported-by: Kamil Dudka

The OpenSSL trace callback is wonderfully undocumented but given a
journey in the source code, it seems the cases were ssl_ver is zero
doesn't follow the same pattern and thus turned out confusing and
misleading. For now, we skip doing any CURLINFO_TEXT logging on those
but keep sending them as CURLINFO_SSL_DATA_OUT/IN.

Also, I added direction to the text info and I edited some functions
slightly.

Bug: https://github.com/bagder/curl/issues/219
Reported-by: Jay Satiro, Ashish Shukla

https://github.com/bagder/curl/issues/244

Commit 145c263a changed the behavior when Curl_read_plain returns
CURLE_AGAIN. We now handle CURLE_AGAIN and SEC_I_CONTEXT_EXPIRED
correctly.

Commit: https://github.com/bagder/curl/commit/926cb9f
Reported-by: Ray Satiro

Bug born in changes made several days ago 9a91e805.

Bug: http://curl.haxx.se/mail/lib-2015-04/0199.html
Reported-by: Brian Chrisman

Bug: http://curl.haxx.se/mail/lib-2015-04/0095.html

Reported-by: Brian Chrisman

white space changes only

To have engine modules work, we must tell openssl to load builtin
modules first.

Bug: https://github.com/bagder/curl/pull/206

The code extracting the cert serial number was broken and didn't display
it properly.

Bug: https://github.com/bagder/curl/issues/235
Reported-by: dkjjr89

Also add public key extraction example to CURLOPT_PINNEDPUBLICKEY doc.

Bug: https://bugzilla.redhat.com/1195771

Prior to this change CyaSSL's build options could redefine some generic
build symbols.

http://curl.haxx.se/mail/lib-2015-04/0069.html