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Issue #12551: Provide a get_channel_binding() method on SSL sockets so as 

to get channel binding data for the current SSL session (only the
"tls-unique" channel binding is implemented).  This allows the
implementation of certain authentication mechanisms such as SCRAM-SHA-1-PLUS.

Patch by Jacek Konieczny.
This commit is contained in:
Antoine Pitrou 2011-07-21 01:11:30 +02:00
parent 875048bd4c
commit d649480739
6 changed files with 196 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
Doc/library/ssl.rst
View File

@ -386,6 +386,13 @@ Constants
.. versionadded:: 3.2
.. data:: CHANNEL_BINDING_TYPES
List of supported TLS channel binding types. Strings in this list
can be used as arguments to :meth:`SSLSocket.get_channel_binding`.
.. versionadded:: 3.3
.. data:: OPENSSL_VERSION
The version string of the OpenSSL library loaded by the interpreter::
@ -495,6 +502,18 @@ SSL sockets also have the following additional methods and attributes:
version of the SSL protocol that defines its use, and the number of secret
bits being used. If no connection has been established, returns ``None``.
.. method:: SSLSocket.get_channel_binding(cb_type="tls-unique")
Get channel binding data for current connection, as a bytes object. Returns
``None`` if not connected or the handshake has not been completed.
The *cb_type* parameter allow selection of the desired channel binding
type. Valid channel binding types are listed in the
:data:`CHANNEL_BINDING_TYPES` list. Currently only the 'tls-unique' channel
binding, defined by :rfc:`5929`, is supported. :exc:`ValueError` will be
raised if an unsupported channel binding type is requested.
.. versionadded:: 3.3
.. method:: SSLSocket.unwrap()

19
Lib/ssl.py
View File

@ -99,6 +99,10 @@ import base64 # for DER-to-PEM translation
import traceback
import errno
if _ssl.HAS_TLS_UNIQUE:
CHANNEL_BINDING_TYPES = ['tls-unique']
else:
CHANNEL_BINDING_TYPES = []
class CertificateError(ValueError):
pass
@ -495,6 +499,21 @@ class SSLSocket(socket):
self.do_handshake_on_connect),
addr)
def get_channel_binding(self, cb_type="tls-unique"):
"""Get channel binding data for current connection. Raise ValueError
if the requested `cb_type` is not supported. Return bytes of the data
or None if the data is not available (e.g. before the handshake).
"""
if cb_type not in CHANNEL_BINDING_TYPES:
raise ValueError("Unsupported channel binding type")
if cb_type != "tls-unique":
raise NotImplementedError(
"{0} channel binding type not implemented"
.format(cb_type))
if self._sslobj is None:
return None
return self._sslobj.tls_unique_cb()
def __del__(self):
# sys.stderr.write("__del__ on %s\n" % repr(self))
self._real_close()

91
Lib/test/test_ssl.py
View File

@ -321,6 +321,25 @@ class BasicSocketTests(unittest.TestCase):
self.assertRaises(ValueError, ctx.wrap_socket, sock, True,
server_hostname="some.hostname")
def test_unknown_channel_binding(self):
# should raise ValueError for unknown type
s = socket.socket(socket.AF_INET)
ss = ssl.wrap_socket(s)
with self.assertRaises(ValueError):
ss.get_channel_binding("unknown-type")
@unittest.skipUnless("tls-unique" in ssl.CHANNEL_BINDING_TYPES,
"'tls-unique' channel binding not available")
def test_tls_unique_channel_binding(self):
# unconnected should return None for known type
s = socket.socket(socket.AF_INET)
ss = ssl.wrap_socket(s)
self.assertIsNone(ss.get_channel_binding("tls-unique"))
# the same for server-side
s = socket.socket(socket.AF_INET)
ss = ssl.wrap_socket(s, server_side=True, certfile=CERTFILE)
self.assertIsNone(ss.get_channel_binding("tls-unique"))
class ContextTests(unittest.TestCase):
@skip_if_broken_ubuntu_ssl
@ -826,6 +845,11 @@ else:
self.sslconn = None
if support.verbose and self.server.connectionchatty:
sys.stdout.write(" server: connection is now unencrypted...\n")
elif stripped == b'CB tls-unique':
if support.verbose and self.server.connectionchatty:
sys.stdout.write(" server: read CB tls-unique from client, sending our CB data...\n")
data = self.sslconn.get_channel_binding("tls-unique")
self.write(repr(data).encode("us-ascii") + b"\n")
else:
if (support.verbose and
self.server.connectionchatty):
@ -1625,6 +1649,73 @@ else:
t.join()
server.close()
@unittest.skipUnless("tls-unique" in ssl.CHANNEL_BINDING_TYPES,
"'tls-unique' channel binding not available")
def test_tls_unique_channel_binding(self):
"""Test tls-unique channel binding."""
if support.verbose:
sys.stdout.write("\n")
server = ThreadedEchoServer(CERTFILE,
certreqs=ssl.CERT_NONE,
ssl_version=ssl.PROTOCOL_TLSv1,
cacerts=CERTFILE,
chatty=True,
connectionchatty=False)
flag = threading.Event()
server.start(flag)
# wait for it to start
flag.wait()
# try to connect
s = ssl.wrap_socket(socket.socket(),
server_side=False,
certfile=CERTFILE,
ca_certs=CERTFILE,
cert_reqs=ssl.CERT_NONE,
ssl_version=ssl.PROTOCOL_TLSv1)
s.connect((HOST, server.port))
try:
# get the data
cb_data = s.get_channel_binding("tls-unique")
if support.verbose:
sys.stdout.write(" got channel binding data: {0!r}\n"
.format(cb_data))
# check if it is sane
self.assertIsNotNone(cb_data)
self.assertEqual(len(cb_data), 12) # True for TLSv1
# and compare with the peers version
s.write(b"CB tls-unique\n")
peer_data_repr = s.read().strip()
self.assertEqual(peer_data_repr,
repr(cb_data).encode("us-ascii"))
s.close()
# now, again
s = ssl.wrap_socket(socket.socket(),
server_side=False,
certfile=CERTFILE,
ca_certs=CERTFILE,
cert_reqs=ssl.CERT_NONE,
ssl_version=ssl.PROTOCOL_TLSv1)
s.connect((HOST, server.port))
new_cb_data = s.get_channel_binding("tls-unique")
if support.verbose:
sys.stdout.write(" got another channel binding data: {0!r}\n"
.format(new_cb_data))
# is it really unique
self.assertNotEqual(cb_data, new_cb_data)
self.assertIsNotNone(cb_data)
self.assertEqual(len(cb_data), 12) # True for TLSv1
s.write(b"CB tls-unique\n")
peer_data_repr = s.read().strip()
self.assertEqual(peer_data_repr,
repr(new_cb_data).encode("us-ascii"))
s.close()
finally:
server.stop()
server.join()
def test_main(verbose=False):
if support.verbose:

1
Misc/ACKS
View File

@ -516,6 +516,7 @@ Lenny Kneler
Pat Knight
Greg Kochanski
Damon Kohler
Jacek Konieczny
Марк Коренберг
Vlad Korolev
Joseph Koshy

6
Misc/NEWS
View File

@ -234,6 +234,12 @@ Core and Builtins
Library
-------
- Issue #12551: Provide a get_channel_binding() method on SSL sockets so as
to get channel binding data for the current SSL session (only the
"tls-unique" channel binding is implemented). This allows the implementation
of certain authentication mechanisms such as SCRAM-SHA-1-PLUS. Patch by
Jacek Konieczny.
- Issue #665194: email.utils now has format_datetime and parsedate_to_datetime
functions, allowing for round tripping of RFC2822 format dates.

60
Modules/_ssl.c
View File

@ -124,6 +124,17 @@ static unsigned int _ssl_locks_count = 0;
# undef HAVE_SSL_CTX_CLEAR_OPTIONS
#endif
/* In case of 'tls-unique' it will be 12 bytes for TLS, 36 bytes for
* older SSL, but let's be safe */
#define PySSL_CB_MAXLEN 128
/* SSL_get_finished got added to OpenSSL in 0.9.5 */
#if OPENSSL_VERSION_NUMBER >= 0x0090500fL
# define HAVE_OPENSSL_FINISHED 1
#else
# define HAVE_OPENSSL_FINISHED 0
#endif
typedef struct {
PyObject_HEAD
SSL_CTX *ctx;
@ -135,6 +146,7 @@ typedef struct {
SSL *ssl;
X509 *peer_cert;
int shutdown_seen_zero;
enum py_ssl_server_or_client socket_type;
} PySSLSocket;
static PyTypeObject PySSLContext_Type;
@ -328,6 +340,7 @@ newPySSLSocket(SSL_CTX *ctx, PySocketSockObject *sock,
SSL_set_accept_state(self->ssl);
PySSL_END_ALLOW_THREADS
self->socket_type = socket_type;
self->Socket = PyWeakref_NewRef((PyObject *) sock, NULL);
return self;
}
@ -1377,6 +1390,41 @@ PyDoc_STRVAR(PySSL_SSLshutdown_doc,
Does the SSL shutdown handshake with the remote end, and returns\n\
the underlying socket object.");
#if HAVE_OPENSSL_FINISHED
static PyObject *
PySSL_tls_unique_cb(PySSLSocket *self)
{
PyObject *retval = NULL;
char buf[PySSL_CB_MAXLEN];
int len;
if (SSL_session_reused(self->ssl) ^ !self->socket_type) {
/* if session is resumed XOR we are the client */
len = SSL_get_finished(self->ssl, buf, PySSL_CB_MAXLEN);
}
else {
/* if a new session XOR we are the server */
len = SSL_get_peer_finished(self->ssl, buf, PySSL_CB_MAXLEN);
}
/* It cannot be negative in current OpenSSL version as of July 2011 */
assert(len >= 0);
if (len == 0)
Py_RETURN_NONE;
retval = PyBytes_FromStringAndSize(buf, len);
return retval;
}
PyDoc_STRVAR(PySSL_tls_unique_cb_doc,
"tls_unique_cb() -> bytes\n\
\n\
Returns the 'tls-unique' channel binding data, as defined by RFC 5929.\n\
\n\
If the TLS handshake is not yet complete, None is returned");
#endif /* HAVE_OPENSSL_FINISHED */
static PyMethodDef PySSLMethods[] = {
{"do_handshake", (PyCFunction)PySSL_SSLdo_handshake, METH_NOARGS},
@ -1391,6 +1439,10 @@ static PyMethodDef PySSLMethods[] = {
{"cipher", (PyCFunction)PySSL_cipher, METH_NOARGS},
{"shutdown", (PyCFunction)PySSL_SSLshutdown, METH_NOARGS,
PySSL_SSLshutdown_doc},
#if HAVE_OPENSSL_FINISHED
{"tls_unique_cb", (PyCFunction)PySSL_tls_unique_cb, METH_NOARGS,
PySSL_tls_unique_cb_doc},
#endif
{NULL, NULL}
};
@ -2221,6 +2273,14 @@ PyInit__ssl(void)
Py_INCREF(r);
PyModule_AddObject(m, "HAS_SNI", r);
#if HAVE_OPENSSL_FINISHED
r = Py_True;
#else
r = Py_False;
#endif
Py_INCREF(r);
PyModule_AddObject(m, "HAS_TLS_UNIQUE", r);
/* OpenSSL version */
/* SSLeay() gives us the version of the library linked against,
which could be different from the headers version.