Allow Connection.get_peer_cert_chain to return cryptography certificates

CHANGELOG.rst

@@ -21,7 +21,7 @@ Deprecations:
 Changes:
 ^^^^^^^^
 
-* ``OpenSSL.SSL.Connection.get_certificate`` now takes an ``as_cryptography`` keyword-argument. When ``True`` is passed then a ``cryptography.x509.Certificate`` is returned, instead of an ``OpenSSL.crypto.X509``. In the future, passing ``False`` (the default) will be deprecated.
+* ``OpenSSL.SSL.Connection.get_certificate`` and ``OpenSSL.SSL.Connection.get_peer_cert_chain`` now take an ``as_cryptography`` keyword-argument. When ``True`` is passed then ``cryptography.x509.Certificate`` are returned, instead of ``OpenSSL.crypto.X509``. In the future, passing ``False`` (the default) will be deprecated.
 
 
 24.2.1 (2024-07-20)

src/OpenSSL/SSL.py

@@ -2762,17 +2762,57 @@ def _cert_stack_to_list(cert_stack: Any) -> list[X509]:
             result.append(pycert)
         return result
 
-    def get_peer_cert_chain(self) -> list[X509] | None:
+    @staticmethod
+    def _cert_stack_to_cryptography_list(
+        cert_stack: Any,
+    ) -> list[x509.Certificate]:
+        """
+        Internal helper to convert a STACK_OF(X509) to a list of X509
+        instances.
+        """
+        result = []
+        for i in range(_lib.sk_X509_num(cert_stack)):
+            cert = _lib.sk_X509_value(cert_stack, i)
+            _openssl_assert(cert != _ffi.NULL)
+            res = _lib.X509_up_ref(cert)
+            _openssl_assert(res >= 1)
+            pycert = X509._from_raw_x509_ptr(cert)
+            result.append(pycert.to_cryptography())
+        return result
+
+    @typing.overload
+    def get_peer_cert_chain(
+        self, *, as_cryptography: typing.Literal[True]
+    ) -> list[x509.Certificate] | None:
+        pass
+
+    @typing.overload
+    def get_peer_cert_chain(
+        self, *, as_cryptography: typing.Literal[False] = False
+    ) -> list[X509] | None:
+        pass
+
+    def get_peer_cert_chain(
+        self,
+        *,
+        as_cryptography: typing.Literal[True] | typing.Literal[False] = False,
+    ) -> list[X509] | list[x509.Certificate] | None:
         """
         Retrieve the other side's certificate (if any)
 
+        :param bool as_cryptography: Controls whether a list of
+            ``cryptography.x509.Certificate`` or ``OpenSSL.crypto.X509``
+            object should be returned.
+
         :return: A list of X509 instances giving the peer's certificate chain,
                  or None if it does not have one.
         """
         cert_stack = _lib.SSL_get_peer_cert_chain(self._ssl)
         if cert_stack == _ffi.NULL:
             return None
 
+        if as_cryptography:
+            return self._cert_stack_to_cryptography_list(cert_stack)
         return self._cert_stack_to_list(cert_stack)
 
     def get_verified_chain(self) -> list[X509] | None:

tests/test_ssl.py

@@ -2604,6 +2604,14 @@ def test_get_peer_cert_chain(self):
         assert "Intermediate Certificate" == chain[1].get_subject().CN
         assert "Authority Certificate" == chain[2].get_subject().CN
 
+        cryptography_chain = client.get_peer_cert_chain(as_cryptography=True)
+        assert len(cryptography_chain) == 3
+        assert chain[0].subject.rfc4514_string() == "CN=Server Certificate"
+        assert (
+            chain[1].subject.rfc4514_string() == "CN=Intermediate Certificate"
+        )
+        assert chain[2].subject.rfc4514_string() == "CN=Authority Certificate"
+
     def test_get_peer_cert_chain_none(self):
         """
         `Connection.get_peer_cert_chain` returns `None` if the peer sends