Don't build dh code on BoringSSL

It doesn't support DH via EVP

Author: alex

src/cryptography/hazmat/primitives/asymmetric/dh.py

@@ -154,7 +154,8 @@ def parameter_numbers(self) -> DHParameterNumbers:
 
 
 DHParametersWithSerialization = DHParameters
-DHParameters.register(rust_openssl.dh.DHParameters)
+if hasattr(rust_openssl, "dh"):
+    DHParameters.register(rust_openssl.dh.DHParameters)
 
 
 class DHPublicKey(metaclass=abc.ABCMeta):
@@ -195,7 +196,8 @@ def __eq__(self, other: object) -> bool:
 
 
 DHPublicKeyWithSerialization = DHPublicKey
-DHPublicKey.register(rust_openssl.dh.DHPublicKey)
+if hasattr(rust_openssl, "dh"):
+    DHPublicKey.register(rust_openssl.dh.DHPublicKey)
 
 
 class DHPrivateKey(metaclass=abc.ABCMeta):
@@ -244,4 +246,5 @@ def private_bytes(
 
 
 DHPrivateKeyWithSerialization = DHPrivateKey
-DHPrivateKey.register(rust_openssl.dh.DHPrivateKey)
+if hasattr(rust_openssl, "dh"):
+    DHPrivateKey.register(rust_openssl.dh.DHPrivateKey)

src/rust/src/backend/mod.rs

@@ -2,6 +2,7 @@
 // 2.0, and the BSD License. See the LICENSE file in the root of this repository
 // for complete details.
 
+#[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))]
 pub(crate) mod dh;
 pub(crate) mod dsa;
 #[cfg(any(not(CRYPTOGRAPHY_IS_LIBRESSL), CRYPTOGRAPHY_LIBRESSL_370_OR_GREATER))]
@@ -19,6 +20,7 @@ pub(crate) mod x25519;
 pub(crate) mod x448;
 
 pub(crate) fn add_to_module(module: &pyo3::prelude::PyModule) -> pyo3::PyResult<()> {
+    #[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))]
     module.add_submodule(dh::create_module(module.py())?)?;
     module.add_submodule(dsa::create_module(module.py())?)?;