The client sent ciphers in the ClientHello are unparsed and thus require
the user to convert u16s into SslCipher instances. It could be worth
doing this parsing in the library itself to make things consistent and
always return a StackRef<SslCipher>.
This feature expects a recent boringssl checkout (such as the one
found in boring-sys/deps/boringssl), so it should not be using
the same bindings as the fips feature, which are based on
boring-sys/deps/boringssl-fips, which is older and with a different
API.
This helps drive async callbacks from outside tokio-boring, such as in quiche.
Not a breaking change because every public item in tokio-boring is preserved as is.
Setting callbacks multiple times on a SslContextBuilder causes the previous callback
installed to leak, using replace_ex_data internally prevents that.
We also start using it in tokio-boring in with_ex_data_future, my understanding
is that the futures currently in use are never installed twice by that function
but that could change in the future with the addition of more async callbacks.
We introduce new methods replace_ex_data for both SslContextBuilder
and Ssl in case anyone is relying on the leaking behaviour of their
set_ex_data methods, but we do document that they leak now.
To handle lifetimes better and allow returning a &mut SslRef from
the client hello struct passed to the closure from
SslContextBuilder::set_select_certificate_callback, we make
the ClientHello struct itself own a reference to the FFI
client hello struct.
These two new kinds of methods immediately return a MidHandshakeSslStream
instead of actually initiating a handshake. This greatly simplifies
loops around MidHandshakeSslStream::WouldBlock.
Overwrite boringSSL's default key exchange preferences with safe
defaults using feature flags:
* "kx-pq-supported" enables support for PQ key exchange algorithms.
Classical key exchange is still preferred, but will be upgraded to PQ
if requested.
* "kx-pq-preferred" enables preference for PQ key exchange,
with fallback to classical key exchange if requested.
* "kx-nist-required" disables non-NIST key exchange.
Each feature implies "kx-safe-default". When this feature is enabled,
don't compile bindings for `SSL_CTX_set1_curves()` and `SslCurve`. This
is to prevent the feature flags from silently overriding curve
preferences chosen by the user.
Ideally we'd allow both: that is, use "kx-*" to set defaults, but still
allow the user to manually override them. However, this doesn't work
because by the time the `SSL_CTX` is constructed, we don't yet know
whether we're the client or server. (The "kx-*" features set different
preferences for each.) If "kx-sfe-default" is set, then the curve
preferences are set just before initiating a TLS handshake
(`SslStreamBuilder::connect()`) or waiting for a TLS handshake
(`SslStreamBuilder::accept()`).
Rushil Mehra