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.
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index d2d2480..1a367f2 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -124,6 +124,17 @@
# 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 @@
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 @@
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 @@
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 @@
{"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 @@
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.