Add support for converting sessions to / from ASN1 representation

CHANGELOG.rst

@@ -4,6 +4,21 @@ Changelog
 Versions are year-based with a strict backward-compatibility policy.
 The third digit is only for regressions.
 
+24.4.0 (UNRELEASED)
+-------------------
+
+Backward-incompatible changes:
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Deprecations:
+^^^^^^^^^^^^^
+
+Changes:
+^^^^^^^^
+
+* Added ``OpenSSL.SSL.Session.i2d`` to convert session objects to ASN1. Updated ``OpenSSL.SSL.Session`` constructor to support conversion from ASN1. `#1373 <https://github.com/pyca/pyopenssl/pull/1373>`_.
+* ``cryptography`` minimum version is now 44.0.x.
+
 24.3.0 (2024-11-27)
 -------------------
 

doc/api/ssl.rst

@@ -154,6 +154,7 @@ Context, Connection.
    :noindex:
 
 .. autoclass:: Session
+   :noindex:
 
 
 .. py:class:: Connection(context, socket)
@@ -247,8 +248,10 @@ Context objects have the following methods:
 Session objects
 ---------------
 
-Session objects have no methods.
+Session objects have the following methods:
 
+.. autoclass:: OpenSSL.SSL.Session
+               :members:
 
 .. _openssl-connection:
 

src/OpenSSL/SSL.py

@@ -821,10 +821,51 @@ class Session:
     parameters which may be re-used to speed up the setup of subsequent
     connections.
 
+    :param data: An optional bytes object of an ASN1 encoded Session.
+
     .. versionadded:: 0.14
     """
 
-    _session: Any
+    _session: Any = None
+
+    def __init__(self, data: bytes | None = None) -> None:
+        if data is None:
+            return
+
+        p = _ffi.new("unsigned char[]", data)
+        pp = _ffi.new("unsigned char **")
+        pp[0] = p
+        length = _ffi.cast("long", len(data))
+
+        session = _lib.d2i_SSL_SESSION(_ffi.NULL, pp, length)
+        if session == _ffi.NULL:
+            _raise_current_error()
+
+        self._session = _ffi.gc(session, _lib.SSL_SESSION_free)
+
+    def i2d(self) -> bytes:
+        """
+        Convert the Session object to an ASN1 encoded bytes object.
+
+        :return A bytes object representing the ASN1 encoded session.
+        """
+
+        if self._session is None:
+            raise ValueError("Not a valid session")
+
+        length = _lib.i2d_SSL_SESSION(self._session, _ffi.NULL)
+        if length == 0:
+            raise ValueError("Not a valid session")
+
+        pp = _ffi.new("unsigned char **")
+        p = _ffi.new("unsigned char[]", length)
+        pp[0] = p
+
+        length = _lib.i2d_SSL_SESSION(self._session, pp)
+        if length == 0:
+            raise ValueError("Not a valid session")
+
+        return _ffi.buffer(p, length)[:]
 
 
 class Context:

tests/test_ssl.py

@@ -321,17 +321,21 @@ def _create_certificate_chain():
     ]
 
 
-def loopback_client_factory(socket, version=SSLv23_METHOD):
+def loopback_client_factory(socket, version=SSLv23_METHOD, session_data=None):
     client = Connection(Context(version), socket)
+    if session_data is not None:
+        client.set_session(Session(session_data))
     client.set_connect_state()
     return client
 
 
-def loopback_server_factory(socket, version=SSLv23_METHOD):
+def loopback_server_factory(socket, version=SSLv23_METHOD, session_data=None):
     ctx = Context(version)
     ctx.use_privatekey(load_privatekey(FILETYPE_PEM, server_key_pem))
     ctx.use_certificate(load_certificate(FILETYPE_PEM, server_cert_pem))
     server = Connection(ctx, socket)
+    if session_data is not None:
+        server.set_session(Session(session_data))
     server.set_accept_state()
     return server
 
@@ -2176,6 +2180,94 @@ def test_construction(self):
         new_session = Session()
         assert isinstance(new_session, Session)
 
+    def test_d2i_fail(self):
+        with pytest.raises(Error) as e:
+            Session(b"abc" * 1000)
+
+        assert e.value.args[0][0] in [
+            # 1.1.x
+            (
+                "asn1 encoding routines",
+                "asn1_check_tlen",
+                "wrong tag",
+            ),
+            # 3.0.x
+            (
+                "asn1 encoding routines",
+                "",
+                "wrong tag",
+            ),
+        ]
+
+        assert e.value.args[0][1] in [
+            # 1.1.x
+            (
+                "asn1 encoding routines",
+                "asn1_item_embed_d2i",
+                "nested asn1 error",
+            ),
+            # 3.0.x
+            (
+                "asn1 encoding routines",
+                "",
+                "nested asn1 error",
+            ),
+        ]
+
+    def test_session_success(self):
+        session_id = (
+            b"\x51\x6d\x1d\x18\xc3\xb5\x86\x81\xc6\x79\x89\x2c\x89\x3e\x56\x33"
+            b"\xa7\x9c\xcd\x9b\x87\xbb\xb3\xdc\xf6\x76\x70\xf9\xc0\xdd\xf4\xef"
+        )
+
+        master_key = (
+            b"\x0f\xb2\x51\xe3\x15\x60\x2d\xef\x6e\x6d\xd2\x94\x2d\xe5\x37\x96"
+            b"\x72\xfa\xce\xb0\x39\xcc\x8d\xdf\xab\x32\xcc\x75\x0c\x66\xf9\xfd"
+            b"\xef\xbc\xc6\x2a\x8f\x9c\x35\x16\xfd\x4d\x38\xd9\xf9\xeb\x1d\xe4"
+        )
+
+        session_data = (
+            # sequence length=0x71
+            b"\x30\x71"
+            # integer (version)
+            b"\x02\x01\x01"
+            # integer (SSL version)
+            b"\x02\x02\x03\x03"
+            # octet-string (cipher suite)
+            b"\x04\x02\xc0\x30"
+            # octet-string length=0x20 (session id)
+            b"\x04\x20"
+            + session_id
+            # octet-string length=0x30 (master secret)
+            + b"\x04\x30"
+            + master_key
+            # application (1), integer (time)
+            + b"\xa1\x06\x02\x04"
+            b"\x66\xec\x4c\x2d"
+            # application (2), integer (timeout)
+            b"\xa2\x04\x02\x02"
+            b"\x02\x58"
+            # application (4), octet-string (session id context)
+            b"\xa4\x02\x04"
+            b"\x00"
+        )
+        serverSocket, clientSocket = socket_pair()
+
+        client = loopback_client_factory(
+            clientSocket, session_data=session_data
+        )
+        server = loopback_server_factory(
+            serverSocket, session_data=session_data
+        )
+
+        assert client.master_key() == master_key
+        assert server.master_key() == master_key
+
+        handshake(client, server)
+
+        client.send(b"hello world")
+        assert b"hello world" == server.recv(len(b"hello world"))
+
 
 @pytest.fixture(params=["context", "connection"])
 def ctx_or_conn(request) -> Union[Context, Connection]:

tox.ini

@@ -18,7 +18,7 @@ extras =
     test
 deps =
     coverage>=4.2
-    cryptographyMinimum: cryptography==41.0.5
+    cryptographyMinimum: cryptography==44.0.0
     randomorder: pytest-randomly
 setenv =
     # Do not allow the executing environment to pollute the test environment