Expose SSL_set_enable_ech_grease (#49)

* RTG-3333 Support X25519MLKEM768 by default, but don't sent it as client

X25519MLKEM768 is the standardised successor of the preliminary
X25519Kyber768Draft00. Latest browsers have switched to X25519MLKEM768.
Cloudflare supports both on the edge.

We've had support for X25519MLKEM768 in this crate for a while, but
didn't enable by default. We're now enabling serverside support by
default. We also let clients advertise support when set
to kx-client-pq-supported.

We don't enable support by default yet for clients set to
kx-client-pq-preferred, as that would cause an extra round-trip due to
HelloRetryRequest if the server doesn't support X25519MLKEM768 yet.

BoringSSL against which we build must support X25519MLKEM768, otherwise
this will fail.

* replace once_cell with LazyLock

We can drop the once_cell dependency since the same functionality is
implemented in std now.

Requires bumping MSRV to 1.80.

* fix manual_c_str_literals clippy warning

* chore: Fix docs on SslRef::replace_ex_data

* Detailed error codes

* Clean up boring_sys::init()

We don't need the workaround that was initially introduced for a bug in
openssl, and OPENSSL_init_ssl always calls into CRYPTO_library_init on
boringssl, so just call it explicitly.

* Expose EVP_HPKE_KEY

* Expose client/server-side ECH

Resolves https://github.com/cloudflare/boring/issues/282

* Clean up ECH tests

* Expose SSL_set_enable_ech_grease

* update

---------

Co-authored-by: Bas Westerbaan <bas@cloudflare.com>
Co-authored-by: Alessandro Ghedini <alessandro@cloudflare.com>
Co-authored-by: Evan Rittenhouse <erittenhouse@cloudflare.com>
Co-authored-by: Kornel <kornel@cloudflare.com>
Co-authored-by: Rushil Mehra <rmehra@cloudflare.com>

boring/src/ssl/connector.rs

@@ -269,6 +269,7 @@ impl ConnectConfiguration {
     /// # Safety
     ///
     /// This function is unsafe because it calls an FFI function.
+    #[cfg(not(feature = "fips"))]
     #[corresponds(SSL_set_enable_ech_grease)]
     pub fn set_enable_ech_grease(&mut self, enable: bool) {
         unsafe { ffi::SSL_set_enable_ech_grease(self.as_ptr(), enable as _) }

boring/src/ssl/mod.rs

@@ -3658,6 +3658,17 @@ impl SslRef {
     pub fn ech_accepted(&self) -> bool {
         unsafe { ffi::SSL_ech_accepted(self.as_ptr()) != 0 }
     }
+
+    // Whether or not to enable ECH grease on `SSL`.
+    #[cfg(not(feature = "fips"))]
+    #[corresponds(SSL_set_enable_ech_grease)]
+    pub fn set_enable_ech_grease(&self, enable: bool) {
+        let enable = if enable { 1 } else { 0 };
+
+        unsafe {
+            ffi::SSL_set_enable_ech_grease(self.as_ptr(), enable);
+        }
+    }
 }
 
 /// An SSL stream midway through the handshake process.

boring/src/ssl/test/ech.rs

@@ -1,6 +1,6 @@
 use crate::hpke::HpkeKey;
 use crate::ssl::ech::SslEchKeys;
-use crate::ssl::test::Server;
+use crate::ssl::test::server::{ClientSslBuilder, Server};
 use crate::ssl::HandshakeError;
 
 // For future reference, these configs are generated by building the bssl tool (the binary is built
@@ -15,12 +15,11 @@ static ECH_KEY: &[u8] = include_bytes!("../../../test/echkey");
 static ECH_CONFIG_2: &[u8] = include_bytes!("../../../test/echconfig-2");
 static ECH_KEY_2: &[u8] = include_bytes!("../../../test/echkey-2");
 
-#[test]
+fn bootstrap_ech(config: &[u8], key: &[u8], list: &[u8]) -> (Server, ClientSslBuilder) {
-fn ech() {
     let server = {
-        let key = HpkeKey::dhkem_p256_sha256(ECH_KEY).unwrap();
+        let key = HpkeKey::dhkem_p256_sha256(key).unwrap();
         let mut ech_keys = SslEchKeys::new().unwrap();
-        ech_keys.add_key(true, ECH_CONFIG, key).unwrap();
+        ech_keys.add_key(true, config, key).unwrap();
 
         let mut builder = Server::builder();
         builder.ctx().set_ech_keys(ech_keys).unwrap();
@@ -29,35 +28,29 @@ fn ech() {
     };
 
     let mut client = server.client_with_root_ca().build().builder();
-    client.ssl().set_ech_config_list(ECH_CONFIG_LIST).unwrap();
+    client.ssl().set_ech_config_list(list).unwrap();
     client.ssl().set_hostname("foobar.com").unwrap();
 
+    (server, client)
+}
+
+#[test]
+fn ech() {
+    let (_server, client) = bootstrap_ech(ECH_CONFIG, ECH_KEY, ECH_CONFIG_LIST);
+
     let ssl_stream = client.connect();
     assert!(ssl_stream.ssl().ech_accepted())
 }
 
 #[test]
 fn ech_rejection() {
-    let server = {
-        let key = HpkeKey::dhkem_p256_sha256(ECH_KEY_2).unwrap();
-        let mut ech_keys = SslEchKeys::new().unwrap();
-        ech_keys.add_key(true, ECH_CONFIG_2, key).unwrap();
-
-        let mut builder = Server::builder();
-        builder.ctx().set_ech_keys(ech_keys).unwrap();
-
-        builder.build()
-    };
-
-    let mut client = server.client_with_root_ca().build().builder();
     // Server is initialized using `ECH_CONFIG_2`, so using `ECH_CONFIG_LIST` instead of
     // `ECH_CONFIG_LIST_2` should trigger rejection.
-    client.ssl().set_ech_config_list(ECH_CONFIG_LIST).unwrap();
+    let (_server, client) = bootstrap_ech(ECH_CONFIG_2, ECH_KEY_2, ECH_CONFIG_LIST);
-    client.ssl().set_hostname("foobar.com").unwrap();
+
     let HandshakeError::Failure(failed_ssl_stream) = client.connect_err() else {
         panic!("wrong HandshakeError failure variant!");
     };
-
     assert_eq!(
         failed_ssl_stream.ssl().get_ech_name_override(),
         Some(b"ech.com".to_vec().as_ref())
@@ -65,3 +58,15 @@ fn ech_rejection() {
     assert!(failed_ssl_stream.ssl().get_ech_retry_configs().is_some());
     assert!(!failed_ssl_stream.ssl().ech_accepted())
 }
+
+#[test]
+fn ech_grease() {
+    let server = Server::builder().build();
+
+    let mut client = server.client_with_root_ca().build().builder();
+    // Verified with a pcap locally that the ECH extension gets sent due to GREASE
+    client.ssl().set_enable_ech_grease(true);
+
+    let ssl_stream = client.connect();
+    assert!(!ssl_stream.ssl().ech_accepted())
+}