[Python-checkins] cpython: Issue #13626: Add support for SSL Diffie-Hellman key exchange, through the

Thu Dec 22 10:04:20 CET 2011

http://hg.python.org/cpython/rev/33dea851f918
changeset: 74129:33dea851f918
user: Antoine Pitrou <solipsis at pitrou.net>
date: Thu Dec 22 10:03:38 2011 +0100
summary:
 Issue #13626: Add support for SSL Diffie-Hellman key exchange, through the
SSLContext.load_dh_params() method and the ssl.OP_SINGLE_DH_USE option.
files:
 Doc/library/ssl.rst | 30 ++++++++++++++++++++----
 Lib/ssl.py | 2 +-
 Lib/test/ssl_servers.py | 4 +++
 Lib/test/test_ssl.py | 29 ++++++++++++++++++++++++
 Misc/NEWS | 3 ++
 Modules/_ssl.c | 35 +++++++++++++++++++++++++++++
 Python/fileutils.c | 6 ++++
 7 files changed, 103 insertions(+), 6 deletions(-)

diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -428,9 +428,17 @@
 
 .. versionadded:: 3.3
 
+.. data:: OP_SINGLE_DH_USE
+
+ Prevents re-use of the same DH key for distinct SSL sessions. This
+ improves forward secrecy but requires more computational resources.
+ This option only applies to server sockets.
+
+ .. versionadded:: 3.3
+
 .. data:: OP_SINGLE_ECDH_USE
 
- Prevents re-use of the same ECDH key for several SSL sessions. This
+ Prevents re-use of the same ECDH key for distinct SSL sessions. This
 improves forward secrecy but requires more computational resources.
 This option only applies to server sockets.
 
@@ -707,12 +715,24 @@
 when connected, the :meth:`SSLSocket.cipher` method of SSL sockets will
 give the currently selected cipher.
 
+.. method:: SSLContext.load_dh_params(dhfile)
+
+ Load the key generation parameters for Diffie-Helman (DH) key exchange.
+ Using DH key exchange improves forward secrecy at the expense of
+ computational resources (both on the server and on the client).
+ The *dhfile* parameter should be the path to a file containing DH
+ parameters in PEM format.
+
+ This setting doesn't apply to client sockets. You can also use the
+ :data:`OP_SINGLE_DH_USE` option to further improve security.
+
+ .. versionadded:: 3.3
+
 .. method:: SSLContext.set_ecdh_curve(curve_name)
 
- Set the curve name for Elliptic Curve-based Diffie-Hellman (abbreviated
- ECDH) key exchange. Using Diffie-Hellman key exchange improves forward
- secrecy at the expense of computational resources (both on the server and
- on the client). The *curve_name* parameter should be a string describing
+ Set the curve name for Elliptic Curve-based Diffie-Hellman (ECDH) key
+ exchange. ECDH is significantly faster than regular DH while arguably
+ as secure. The *curve_name* parameter should be a string describing
 a well-known elliptic curve, for example ``prime256v1`` for a widely
 supported curve.
 
diff --git a/Lib/ssl.py b/Lib/ssl.py
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -68,7 +68,7 @@
 from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
 from _ssl import (
 OP_ALL, OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_TLSv1,
- OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_ECDH_USE,
+ OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE, OP_SINGLE_ECDH_USE,
 )
 try:
 from _ssl import OP_NO_COMPRESSION
diff --git a/Lib/test/ssl_servers.py b/Lib/test/ssl_servers.py
--- a/Lib/test/ssl_servers.py
+++ b/Lib/test/ssl_servers.py
@@ -180,6 +180,8 @@
 parser.add_argument('--curve-name', dest='curve_name', type=str,
 action='store',
 help='curve name for EC-based Diffie-Hellman')
+ parser.add_argument('--dh', dest='dh_file', type=str, action='store',
+ help='PEM file containing DH parameters')
 args = parser.parse_args()
 
 support.verbose = args.verbose
@@ -192,6 +194,8 @@
 context.load_cert_chain(CERTFILE)
 if args.curve_name:
 context.set_ecdh_curve(args.curve_name)
+ if args.dh_file:
+ context.load_dh_params(args.dh_file)
 
 server = HTTPSServer(("", args.port), handler_class, context)
 if args.verbose:
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -56,6 +56,8 @@
 BADKEY = data_file("badkey.pem")
 NOKIACERT = data_file("nokia.pem")
 
+DHFILE = data_file("dh512.pem")
+BYTES_DHFILE = os.fsencode(DHFILE)
 
 def handle_error(prefix):
 exc_format = ' '.join(traceback.format_exception(*sys.exc_info()))
@@ -99,6 +101,7 @@
 ssl.CERT_OPTIONAL
 ssl.CERT_REQUIRED
 ssl.OP_CIPHER_SERVER_PREFERENCE
+ ssl.OP_SINGLE_DH_USE
 ssl.OP_SINGLE_ECDH_USE
 if ssl.OPENSSL_VERSION_INFO >= (1, 0):
 ssl.OP_NO_COMPRESSION
@@ -538,6 +541,19 @@
 # Issue #10989: crash if the second argument type is invalid
 self.assertRaises(TypeError, ctx.load_verify_locations, None, True)
 
+ def test_load_dh_params(self):
+ ctx = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+ ctx.load_dh_params(DHFILE)
+ if os.name != 'nt':
+ ctx.load_dh_params(BYTES_DHFILE)
+ self.assertRaises(TypeError, ctx.load_dh_params)
+ self.assertRaises(TypeError, ctx.load_dh_params, None)
+ with self.assertRaises(FileNotFoundError) as cm:
+ ctx.load_dh_params(WRONGCERT)
+ self.assertEqual(cm.exception.errno, errno.ENOENT)
+ with self.assertRaisesRegex(ssl.SSLError, "PEM routines"):
+ ctx.load_dh_params(CERTFILE)
+
 @skip_if_broken_ubuntu_ssl
 def test_session_stats(self):
 for proto in PROTOCOLS:
@@ -1802,6 +1818,19 @@
 chatty=True, connectionchatty=True)
 self.assertIs(stats['compression'], None)
 
+ def test_dh_params(self):
+ # Check we can get a connection with ephemeral Diffie-Hellman
+ context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+ context.load_cert_chain(CERTFILE)
+ context.load_dh_params(DHFILE)
+ context.set_ciphers("kEDH")
+ stats = server_params_test(context, context,
+ chatty=True, connectionchatty=True)
+ cipher = stats["cipher"][0]
+ parts = cipher.split("-")
+ if "ADH" not in parts and "EDH" not in parts and "DHE" not in parts:
+ self.fail("Non-DH cipher: " + cipher[0])
+
 
 def test_main(verbose=False):
 if support.verbose:
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -419,6 +419,9 @@
 Library
 -------
 
+- Issue #13626: Add support for SSL Diffie-Hellman key exchange, through the
+ SSLContext.load_dh_params() method and the ssl.OP_SINGLE_DH_USE option.
+
 - Issue #11006: Don't issue low level warning in subprocess when pipe2() fails.
 
 - Issue #13620: Support for Chrome browser in webbrowser.py Patch contributed
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -1922,6 +1922,38 @@
 }
 
 static PyObject *
+load_dh_params(PySSLContext *self, PyObject *filepath)
+{
+ FILE *f;
+ DH *dh;
+
+ f = _Py_fopen(filepath, "rb");
+ if (f == NULL) {
+ if (!PyErr_Occurred())
+ PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, filepath);
+ return NULL;
+ }
+ errno = 0;
+ PySSL_BEGIN_ALLOW_THREADS
+ dh = PEM_read_DHparams(f, NULL, NULL, NULL);
+ PySSL_END_ALLOW_THREADS
+ if (dh == NULL) {
+ if (errno != 0) {
+ ERR_clear_error();
+ PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, filepath);
+ }
+ else {
+ _setSSLError(NULL, 0, __FILE__, __LINE__);
+ }
+ return NULL;
+ }
+ if (SSL_CTX_set_tmp_dh(self->ctx, dh) == 0)
+ _setSSLError(NULL, 0, __FILE__, __LINE__);
+ DH_free(dh);
+ Py_RETURN_NONE;
+}
+
+static PyObject *
 context_wrap_socket(PySSLContext *self, PyObject *args, PyObject *kwds)
 {
 char *kwlist[] = {"sock", "server_side", "server_hostname", NULL};
@@ -2050,6 +2082,8 @@
 METH_VARARGS, NULL},
 {"load_cert_chain", (PyCFunction) load_cert_chain,
 METH_VARARGS | METH_KEYWORDS, NULL},
+ {"load_dh_params", (PyCFunction) load_dh_params,
+ METH_O, NULL},
 {"load_verify_locations", (PyCFunction) load_verify_locations,
 METH_VARARGS | METH_KEYWORDS, NULL},
 {"session_stats", (PyCFunction) session_stats,
@@ -2505,6 +2539,7 @@
 PyModule_AddIntConstant(m, "OP_NO_TLSv1", SSL_OP_NO_TLSv1);
 PyModule_AddIntConstant(m, "OP_CIPHER_SERVER_PREFERENCE",
 SSL_OP_CIPHER_SERVER_PREFERENCE);
+ PyModule_AddIntConstant(m, "OP_SINGLE_DH_USE", SSL_OP_SINGLE_DH_USE);
 PyModule_AddIntConstant(m, "OP_SINGLE_ECDH_USE", SSL_OP_SINGLE_ECDH_USE);
 #ifdef SSL_OP_NO_COMPRESSION
 PyModule_AddIntConstant(m, "OP_NO_COMPRESSION",
diff --git a/Python/fileutils.c b/Python/fileutils.c
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -310,6 +310,12 @@
 wchar_t wmode[10];
 int usize;
 
+ if (!PyUnicode_Check(path)) {
+ PyErr_Format(PyExc_TypeError,
+ "str file path expected under Windows, got %R",
+ Py_TYPE(path));
+ return NULL;
+ }
 wpath = PyUnicode_AsUnicode(path);
 if (wpath == NULL)
 return NULL;
-- 
Repository URL: http://hg.python.org/cpython
