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Issue #18709: Fix CVE-2013-4238. The SSL module now handles NULL bytes

inside subjectAltName correctly. Formerly the module has used OpenSSL's
GENERAL_NAME_print() function to get the string represention of ASN.1
strings for rfc822Name (email), dNSName (DNS) and
uniformResourceIdentifier (URI).
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tiran committed Aug 16, 2013
1 parent 29c3fc5 commit 824f7f366d1b54d2d3100c3130c04cf1dfb4b47c
Showing with 184 additions and 5 deletions.
  1. +90 −0 Lib/test/nullbytecert.pem
  2. +29 −0 Lib/test/test_ssl.py
  3. +6 −0 Misc/NEWS
  4. +59 −5 Modules/_ssl.c
View
@@ -0,0 +1,90 @@
Certificate:
Data:
Version: 3 (0x2)
Serial Number: 0 (0x0)
Signature Algorithm: sha1WithRSAEncryption
Issuer: C=US, ST=Oregon, L=Beaverton, O=Python Software Foundation, OU=Python Core Development, CN=null.python.org\x00example.org/emailAddress=python-dev@python.org
Validity
Not Before: Aug 7 13:11:52 2013 GMT
Not After : Aug 7 13:12:52 2013 GMT
Subject: C=US, ST=Oregon, L=Beaverton, O=Python Software Foundation, OU=Python Core Development, CN=null.python.org\x00example.org/emailAddress=python-dev@python.org
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (2048 bit)
Modulus:
00:b5:ea:ed:c9:fb:46:7d:6f:3b:76:80:dd:3a:f3:
03:94:0b:a7:a6:db:ec:1d:df:ff:23:74:08:9d:97:
16:3f:a3:a4:7b:3e:1b:0e:96:59:25:03:a7:26:e2:
88:a9:cf:79:cd:f7:04:56:b0:ab:79:32:6e:59:c1:
32:30:54:eb:58:a8:cb:91:f0:42:a5:64:27:cb:d4:
56:31:88:52:ad:cf:bd:7f:f0:06:64:1f:cc:27:b8:
a3:8b:8c:f3:d8:29:1f:25:0b:f5:46:06:1b:ca:02:
45:ad:7b:76:0a:9c:bf:bb:b9:ae:0d:16:ab:60:75:
ae:06:3e:9c:7c:31:dc:92:2f:29:1a:e0:4b:0c:91:
90:6c:e9:37:c5:90:d7:2a:d7:97:15:a3:80:8f:5d:
7b:49:8f:54:30:d4:97:2c:1c:5b:37:b5:ab:69:30:
68:43:d3:33:78:4b:02:60:f5:3c:44:80:a1:8f:e7:
f0:0f:d1:5e:87:9e:46:cf:62:fc:f9:bf:0c:65:12:
f1:93:c8:35:79:3f:c8:ec:ec:47:f5:ef:be:44:d5:
ae:82:1e:2d:9a:9f:98:5a:67:65:e1:74:70:7c:cb:
d3:c2:ce:0e:45:49:27:dc:e3:2d:d4:fb:48:0e:2f:
9e:77:b8:14:46:c0:c4:36:ca:02:ae:6a:91:8c:da:
2f:85
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Basic Constraints: critical
CA:FALSE
X509v3 Subject Key Identifier:
88:5A:55:C0:52:FF:61:CD:52:A3:35:0F:EA:5A:9C:24:38:22:F7:5C
X509v3 Key Usage:
Digital Signature, Non Repudiation, Key Encipherment
X509v3 Subject Alternative Name:
*************************************************************
WARNING: The values for DNS, email and URI are WRONG. OpenSSL
doesn't print the text after a NULL byte.
*************************************************************
DNS:altnull.python.org, email:null@python.org, URI:http://null.python.org, IP Address:192.0.2.1, IP Address:2001:DB8:0:0:0:0:0:1
Signature Algorithm: sha1WithRSAEncryption
ac:4f:45:ef:7d:49:a8:21:70:8e:88:59:3e:d4:36:42:70:f5:
a3:bd:8b:d7:a8:d0:58:f6:31:4a:b1:a4:a6:dd:6f:d9:e8:44:
3c:b6:0a:71:d6:7f:b1:08:61:9d:60:ce:75:cf:77:0c:d2:37:
86:02:8d:5e:5d:f9:0f:71:b4:16:a8:c1:3d:23:1c:f1:11:b3:
56:6e:ca:d0:8d:34:94:e6:87:2a:99:f2:ae:ae:cc:c2:e8:86:
de:08:a8:7f:c5:05:fa:6f:81:a7:82:e6:d0:53:9d:34:f4:ac:
3e:40:fe:89:57:7a:29:a4:91:7e:0b:c6:51:31:e5:10:2f:a4:
60:76:cd:95:51:1a:be:8b:a1:b0:fd:ad:52:bd:d7:1b:87:60:
d2:31:c7:17:c4:18:4f:2d:08:25:a3:a7:4f:b7:92:ca:e2:f5:
25:f1:54:75:81:9d:b3:3d:61:a2:f7:da:ed:e1:c6:6f:2c:60:
1f:d8:6f:c5:92:05:ab:c9:09:62:49:a9:14:ad:55:11:cc:d6:
4a:19:94:99:97:37:1d:81:5f:8b:cf:a3:a8:96:44:51:08:3d:
0b:05:65:12:eb:b6:70:80:88:48:72:4f:c6:c2:da:cf:cd:8e:
5b:ba:97:2f:60:b4:96:56:49:5e:3a:43:76:63:04:be:2a:f6:
c1:ca:a9:94
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
View
@@ -55,6 +55,7 @@
WRONGCERT = data_file("XXXnonexisting.pem")
BADKEY = data_file("badkey.pem")
NOKIACERT = data_file("nokia.pem")
NULLBYTECERT = data_file("nullbytecert.pem")
DHFILE = data_file("dh512.pem")
BYTES_DHFILE = os.fsencode(DHFILE)
@@ -162,6 +163,27 @@ def test_parse_cert(self):
('DNS', 'projects.forum.nokia.com'))
)
def test_parse_cert_CVE_2013_4238(self):
p = ssl._ssl._test_decode_cert(NULLBYTECERT)
if support.verbose:
sys.stdout.write("\n" + pprint.pformat(p) + "\n")
subject = ((('countryName', 'US'),),
(('stateOrProvinceName', 'Oregon'),),
(('localityName', 'Beaverton'),),
(('organizationName', 'Python Software Foundation'),),
(('organizationalUnitName', 'Python Core Development'),),
(('commonName', 'null.python.org\x00example.org'),),
(('emailAddress', 'python-dev@python.org'),))
self.assertEqual(p['subject'], subject)
self.assertEqual(p['issuer'], subject)
self.assertEqual(p['subjectAltName'],
(('DNS', 'altnull.python.org\x00example.com'),
('email', 'null@python.org\x00user@example.org'),
('URI', 'http://null.python.org\x00http://example.org'),
('IP Address', '192.0.2.1'),
('IP Address', '2001:DB8:0:0:0:0:0:1\n'))
)
def test_DER_to_PEM(self):
with open(SVN_PYTHON_ORG_ROOT_CERT, 'r') as f:
pem = f.read()
@@ -294,6 +316,13 @@ def fail(cert, hostname):
fail(cert, 'foo.a.com')
fail(cert, 'bar.foo.com')
# NULL bytes are bad, CVE-2013-4073
cert = {'subject': ((('commonName',
'null.python.org\x00example.org'),),)}
ok(cert, 'null.python.org\x00example.org') # or raise an error?
fail(cert, 'example.org')
fail(cert, 'null.python.org')
# Slightly fake real-world example
cert = {'notAfter': 'Jun 26 21:41:46 2011 GMT',
'subject': ((('commonName', 'linuxfrz.org'),),),
View
@@ -66,6 +66,12 @@ Core and Builtins
Library
-------
- Issue #18709: Fix CVE-2013-4238. The SSL module now handles NULL bytes
inside subjectAltName correctly. Formerly the module has used OpenSSL's
GENERAL_NAME_print() function to get the string represention of ASN.1
strings for ``rfc822Name`` (email), ``dNSName`` (DNS) and
``uniformResourceIdentifier`` (URI).
- Issue #18405: Improve the entropy of crypt.mksalt().
- Issue #18676: Change 'positive' to 'non-negative' in queue.py put and get
View
@@ -771,12 +771,14 @@ _get_peer_alt_names (X509 *certificate) {
ext->value->length));
for(j = 0; j < sk_GENERAL_NAME_num(names); j++) {
/* get a rendering of each name in the set of names */
int gntype;
ASN1_STRING *as = NULL;
name = sk_GENERAL_NAME_value(names, j);
if (name->type == GEN_DIRNAME) {
gntype = name-> type;
switch (gntype) {
case GEN_DIRNAME:
/* we special-case DirName as a tuple of
tuples of attributes */
@@ -798,11 +800,62 @@ _get_peer_alt_names (X509 *certificate) {
goto fail;
}
PyTuple_SET_ITEM(t, 1, v);
break;
} else {
case GEN_EMAIL:
case GEN_DNS:
case GEN_URI:
/* GENERAL_NAME_print() doesn't handle NULL bytes in ASN1_string
correctly, CVE-2013-4238 */
t = PyTuple_New(2);
if (t == NULL)
goto fail;
switch (gntype) {
case GEN_EMAIL:
v = PyUnicode_FromString("email");
as = name->d.rfc822Name;
break;
case GEN_DNS:
v = PyUnicode_FromString("DNS");
as = name->d.dNSName;
break;
case GEN_URI:
v = PyUnicode_FromString("URI");
as = name->d.uniformResourceIdentifier;
break;
}
if (v == NULL) {
Py_DECREF(t);
goto fail;
}
PyTuple_SET_ITEM(t, 0, v);
v = PyUnicode_FromStringAndSize((char *)ASN1_STRING_data(as),
ASN1_STRING_length(as));
if (v == NULL) {
Py_DECREF(t);
goto fail;
}
PyTuple_SET_ITEM(t, 1, v);
break;
default:
/* for everything else, we use the OpenSSL print form */
switch (gntype) {
/* check for new general name type */
case GEN_OTHERNAME:
case GEN_X400:
case GEN_EDIPARTY:
case GEN_IPADD:
case GEN_RID:
break;
default:
if (PyErr_WarnFormat(PyExc_RuntimeWarning, 1,
"Unknown general name type %d",
gntype) == -1) {
goto fail;
}
break;
}
(void) BIO_reset(biobuf);
GENERAL_NAME_print(biobuf, name);
len = BIO_gets(biobuf, buf, sizeof(buf)-1);
@@ -829,6 +882,7 @@ _get_peer_alt_names (X509 *certificate) {
goto fail;
}
PyTuple_SET_ITEM(t, 1, v);
break;
}
/* and add that rendering to the list */

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