This implies ticket key size of 80 bytes instead of previously used 48,
as both HMAC and AES keys are 32 bytes now.  When an old 48-byte ticket key
is provided, we fall back to using backward-compatible AES128 encryption.

OpenSSL switched to using AES256 in 1.1.0, and we are providing equivalent
security.  While here, order of HMAC and AES keys was reverted to make
the implementation compatible with keys used by OpenSSL with
SSL_CTX_set_tlsext_ticket_keys().

Prodded by Christian Klinger.

Changeset e7cb5deb951d breaks build on CentOS 5 with "dereferencing
type-punned pointer will break strict-aliasing rules" warning.  It is
backed out.

Instead, to keep builds with BoringSSL happy, type of the "value"
variable changed to "char *", and an explicit cast added before calling
ngx_parse_http_time().

Fixes build with BoringSSL.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

The variable contains a list of curves as supported by the client.
Known curves are listed by their names, unknown ones are shown
in hex, e.g., "0x001d:prime256v1:secp521r1:secp384r1".

Note that OpenSSL uses session data for SSL_get1_curves(), and
it doesn't store full list of curves supported by the client when
serializing a session.  As a result $ssl_curves is only available
for new sessions (and will be empty for reused ones).

The variable is only meaningful when using OpenSSL 1.0.2 and above.
With older versions the variable is empty.

The variable contains list of ciphers as supported by the client.
Known ciphers are listed by their names, unknown ones are shown
in hex, e.g., ""AES128-SHA:AES256-SHA:0x00ff".

The variable is fully supported only when using OpenSSL 1.0.2 and above.
With older version there is an attempt to provide some information
using SSL_get_shared_ciphers().  It only lists known ciphers though.
Moreover, as OpenSSL uses session data for SSL_get_shared_ciphers(),
and it doesn't store relevant data when serializing a session.  As
a result $ssl_ciphers is only available for new sessions (and not
available for reused ones) when using OpenSSL older than 1.0.2.

Now in case of a verification failure $ssl_client_verify contains
"FAILED:<reason>", similar to Apache's SSL_CLIENT_VERIFY, e.g.,
"FAILED:certificate has expired".

Detailed description of possible errors can be found in the verify(1)
manual page as provided by OpenSSL.

It now logs the IP address of the responder used (if it's already known),
as well as the certificate name.