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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.
This commit is contained in:
Antoine Pitrou 2011-12-22 10:03:38 +01:00
parent 5ad1af076c
commit 0e576f1f50
7 changed files with 103 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
Doc/library/ssl.rst
View File

@ -428,9 +428,17 @@ Constants
.. 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 @@ to speed up repeated connections from the same clients.
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.

2
Lib/ssl.py
View File

@ -68,7 +68,7 @@ from _ssl import (
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

4
Lib/test/ssl_servers.py
View File

@ -180,6 +180,8 @@ if __name__ == "__main__":
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 @@ if __name__ == "__main__":
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:

29
Lib/test/test_ssl.py
View File

@ -56,6 +56,8 @@ WRONGCERT = data_file("XXXnonexisting.pem")
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 @@ class BasicSocketTests(unittest.TestCase):
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 @@ class ContextTests(unittest.TestCase):
# 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 @@ else:
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:

3
Misc/NEWS
View File

@ -419,6 +419,9 @@ Core and Builtins
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

35
Modules/_ssl.c
View File

@ -1921,6 +1921,38 @@ load_verify_locations(PySSLContext *self, PyObject *args, PyObject *kwds)
Py_RETURN_NONE;
}
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)
{
@ -2050,6 +2082,8 @@ static struct PyMethodDef context_methods[] = {
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 @@ PyInit__ssl(void)
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",

6
Python/fileutils.c
View File

@ -310,6 +310,12 @@ _Py_fopen(PyObject *path, const char *mode)
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;