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bpo-35746: Fix segfault in ssl's cert parser (GH-11569) 

Fix a NULL pointer deref in ssl module. The cert parser did not handle CRL
distribution points with empty DP or URI correctly. A malicious or buggy
certificate can result into segfault.

Signed-off-by: Christian Heimes <christian@python.org>

https://bugs.python.org/issue35746
(cherry picked from commit a37f52436f)

Co-authored-by: Christian Heimes <christian@python.org>
This commit is contained in:
Miss Islington (bot) 2019-01-15 15:11:52 -08:00 committed by GitHub
parent 1462234baf
commit 06b15424b0
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4 changed files with 51 additions and 0 deletions
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22
Lib/test/talos-2019-0758.pem Normal file
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@ -0,0 +1,22 @@
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

22
Lib/test/test_ssl.py
View File

@ -72,6 +72,7 @@ NONEXISTINGCERT = data_file("XXXnonexisting.pem")
BADKEY = data_file("badkey.pem")
NOKIACERT = data_file("nokia.pem")
NULLBYTECERT = data_file("nullbytecert.pem")
TALOS_INVALID_CRLDP = data_file("talos-2019-0758.pem")
DHFILE = data_file("ffdh3072.pem")
BYTES_DHFILE = DHFILE.encode(sys.getfilesystemencoding())
@ -227,6 +228,27 @@ class BasicSocketTests(unittest.TestCase):
self.assertEqual(p['crlDistributionPoints'],
('http://SVRIntl-G3-crl.verisign.com/SVRIntlG3.crl',))
def test_parse_cert_CVE_2019_5010(self):
p = ssl._ssl._test_decode_cert(TALOS_INVALID_CRLDP)
if support.verbose:
sys.stdout.write("\n" + pprint.pformat(p) + "\n")
self.assertEqual(
p,
{
'issuer': (
(('countryName', 'UK'),), (('commonName', 'cody-ca'),)),
'notAfter': 'Jun 14 18:00:58 2028 GMT',
'notBefore': 'Jun 18 18:00:58 2018 GMT',
'serialNumber': '02',
'subject': ((('countryName', 'UK'),),
(('commonName',
'codenomicon-vm-2.test.lal.cisco.com'),)),
'subjectAltName': (
('DNS', 'codenomicon-vm-2.test.lal.cisco.com'),),
'version': 3
}
)
def test_parse_cert_CVE_2013_4238(self):
p = ssl._ssl._test_decode_cert(NULLBYTECERT)
if support.verbose:

3
Misc/NEWS.d/next/Security/2019-01-15-18-16-05.bpo-35746.nMSd0j.rst Normal file
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@ -0,0 +1,3 @@
[CVE-2019-5010] Fix a NULL pointer deref in ssl module. The cert parser did
not handle CRL distribution points with empty DP or URI correctly. A
malicious or buggy certificate can result into segfault.

4
Modules/_ssl.c
View File

@ -1223,6 +1223,10 @@ _get_crl_dp(X509 *certificate) {
STACK_OF(GENERAL_NAME) *gns;
dp = sk_DIST_POINT_value(dps, i);
if (dp->distpoint == NULL) {
/* Ignore empty DP value, CVE-2019-5010 */
continue;
}
gns = dp->distpoint->name.fullname;
for (j=0; j < sk_GENERAL_NAME_num(gns); j++) {