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bpo-35050: AF_ALG length check off-by-one error (GH-10058) 

The length check for AF_ALG salg_name and salg_type had a off-by-one
error. The code assumed that both values are not necessarily NULL
terminated. However the Kernel code for alg_bind() ensures that the last
byte of both strings are NULL terminated.

Signed-off-by: Christian Heimes <christian@python.org>
This commit is contained in:
Christian Heimes 2018-12-10 11:22:37 +01:00 committed by Victor Stinner
parent 8e04186889
commit 2eb6ad8578
3 changed files with 24 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
Lib/test/test_socket.py
View File

@ -5969,6 +5969,24 @@ class LinuxKernelCryptoAPI(unittest.TestCase):
with self.assertRaises(TypeError):
sock.sendmsg_afalg(op=socket.ALG_OP_ENCRYPT, assoclen=-1)
def test_length_restriction(self):
# bpo-35050, off-by-one error in length check
sock = socket.socket(socket.AF_ALG, socket.SOCK_SEQPACKET, 0)
self.addCleanup(sock.close)
# salg_type[14]
with self.assertRaises(FileNotFoundError):
sock.bind(("t" * 13, "name"))
with self.assertRaisesRegex(ValueError, "type too long"):
sock.bind(("t" * 14, "name"))
# salg_name[64]
with self.assertRaises(FileNotFoundError):
sock.bind(("type", "n" * 63))
with self.assertRaisesRegex(ValueError, "name too long"):
sock.bind(("type", "n" * 64))
@unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
class TestMSWindowsTCPFlags(unittest.TestCase):
knownTCPFlags = {

1
Misc/NEWS.d/next/Core and Builtins/2018-10-23-15-03-53.bpo-35050.49wraS.rst Normal file
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@ -0,0 +1 @@
:mod:`socket`: Fix off-by-one bug in length check for ``AF_ALG`` name and type.

8
Modules/socketmodule.c
View File

@ -2245,13 +2245,15 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
{
return 0;
}
/* sockaddr_alg has fixed-sized char arrays for type and name */
if (strlen(type) > sizeof(sa->salg_type)) {
/* sockaddr_alg has fixed-sized char arrays for type, and name
* both must be NULL terminated.
*/
if (strlen(type) >= sizeof(sa->salg_type)) {
PyErr_SetString(PyExc_ValueError, "AF_ALG type too long.");
return 0;
}
strncpy((char *)sa->salg_type, type, sizeof(sa->salg_type));
if (strlen(name) > sizeof(sa->salg_name)) {
if (strlen(name) >= sizeof(sa->salg_name)) {
PyErr_SetString(PyExc_ValueError, "AF_ALG name too long.");
return 0;
}