[Python-checkins] bpo-32819: Simplify and improve ssl.match_hostname (#5620)
Christian Heimes
webhook-mailer at python.org
Sat Feb 24 08:35:59 EST 2018
https://github.com/python/cpython/commit/aef1283ba428e33397d87cee3c54a5110861552d
commit: aef1283ba428e33397d87cee3c54a5110861552d
branch: master
author: Christian Heimes <christian at python.org>
committer: GitHub <noreply at github.com>
date: 2018-02-24T14:35:56+01:00
summary:
bpo-32819: Simplify and improve ssl.match_hostname (#5620)
ssl.match_hostname() has been simplified and no longer depends on re and
ipaddress module for wildcard and IP addresses. Error reporting for invalid
wildcards has been improved.
Signed-off-by: Christian Heimes <christian at python.org>
files:
A Misc/NEWS.d/next/Library/2018-02-11-15-54-41.bpo-32819.ZTRX2Q.rst
M Lib/ssl.py
M Lib/test/test_ssl.py
diff --git a/Lib/ssl.py b/Lib/ssl.py
index f2537698d303..ecdbb7076283 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -90,8 +90,6 @@
ALERT_DESCRIPTION_UNKNOWN_PSK_IDENTITY
"""
-import ipaddress
-import re
import sys
import os
from collections import namedtuple
@@ -160,6 +158,7 @@
from socket import socket, AF_INET, SOCK_STREAM, create_connection
from socket import SOL_SOCKET, SO_TYPE
+import socket as _socket
import base64 # for DER-to-PEM translation
import errno
import warnings
@@ -183,55 +182,75 @@
def _dnsname_match(dn, hostname):
"""Matching according to RFC 6125, section 6.4.3
- http://tools.ietf.org/html/rfc6125#section-6.4.3
+ - Hostnames are compared lower case.
+ - For IDNA, both dn and hostname must be encoded as IDN A-label (ACE).
+ - Partial wildcards like 'www*.example.org', multiple wildcards, sole
+ wildcard or wildcards in labels other then the left-most label are not
+ supported and a CertificateError is raised.
+ - A wildcard must match at least one character.
"""
- pats = []
if not dn:
return False
- leftmost, *remainder = dn.split(r'.')
+ wildcards = dn.count('*')
+ # speed up common case w/o wildcards
+ if not wildcards:
+ return dn.lower() == hostname.lower()
+
+ if wildcards > 1:
+ raise CertificateError(
+ "too many wildcards in certificate DNS name: {!r}.".format(dn))
- wildcards = leftmost.count('*')
- if wildcards == 1 and len(leftmost) > 1:
+ dn_leftmost, sep, dn_remainder = dn.partition('.')
+
+ if '*' in dn_remainder:
# Only match wildcard in leftmost segment.
raise CertificateError(
- "wildcard can only be present in the leftmost segment: " + repr(dn))
+ "wildcard can only be present in the leftmost label: "
+ "{!r}.".format(dn))
- if wildcards > 1:
- # Issue #17980: avoid denials of service by refusing more
- # than one wildcard per fragment. A survey of established
- # policy among SSL implementations showed it to be a
- # reasonable choice.
+ if not sep:
+ # no right side
raise CertificateError(
- "too many wildcards in certificate DNS name: " + repr(dn))
+ "sole wildcard without additional labels are not support: "
+ "{!r}.".format(dn))
- # speed up common case w/o wildcards
- if not wildcards:
- return dn.lower() == hostname.lower()
+ if dn_leftmost != '*':
+ # no partial wildcard matching
+ raise CertificateError(
+ "partial wildcards in leftmost label are not supported: "
+ "{!r}.".format(dn))
- # RFC 6125, section 6.4.3, subitem 1.
- # The client SHOULD NOT attempt to match a presented identifier in which
- # the wildcard character comprises a label other than the left-most label.
- if leftmost == '*':
- # When '*' is a fragment by itself, it matches a non-empty dotless
- # fragment.
- pats.append('[^.]+')
- elif leftmost.startswith('xn--') or hostname.startswith('xn--'):
- # RFC 6125, section 6.4.3, subitem 3.
- # The client SHOULD NOT attempt to match a presented identifier
- # where the wildcard character is embedded within an A-label or
- # U-label of an internationalized domain name.
- pats.append(re.escape(leftmost))
- else:
- # Otherwise, '*' matches any dotless string, e.g. www*
- pats.append(re.escape(leftmost).replace(r'\*', '[^.]*'))
+ hostname_leftmost, sep, hostname_remainder = hostname.partition('.')
+ if not hostname_leftmost or not sep:
+ # wildcard must match at least one char
+ return False
+ return dn_remainder.lower() == hostname_remainder.lower()
- # add the remaining fragments, ignore any wildcards
- for frag in remainder:
- pats.append(re.escape(frag))
- pat = re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
- return pat.match(hostname)
+def _inet_paton(ipname):
+ """Try to convert an IP address to packed binary form
+
+ Supports IPv4 addresses on all platforms and IPv6 on platforms with IPv6
+ support.
+ """
+ # inet_aton() also accepts strings like '1'
+ if ipname.count('.') == 3:
+ try:
+ return _socket.inet_aton(ipname)
+ except OSError:
+ pass
+
+ try:
+ return _socket.inet_pton(_socket.AF_INET6, ipname)
+ except OSError:
+ raise ValueError("{!r} is neither an IPv4 nor an IP6 "
+ "address.".format(ipname))
+ except AttributeError:
+ # AF_INET6 not available
+ pass
+
+ raise ValueError("{!r} is not an IPv4 address.".format(ipname))
def _ipaddress_match(ipname, host_ip):
@@ -241,14 +260,19 @@ def _ipaddress_match(ipname, host_ip):
(section 1.7.2 - "Out of Scope").
"""
# OpenSSL may add a trailing newline to a subjectAltName's IP address
- ip = ipaddress.ip_address(ipname.rstrip())
+ ip = _inet_paton(ipname.rstrip())
return ip == host_ip
def match_hostname(cert, hostname):
"""Verify that *cert* (in decoded format as returned by
SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 and RFC 6125
- rules are followed, but IP addresses are not accepted for *hostname*.
+ rules are followed.
+
+ The function matches IP addresses rather than dNSNames if hostname is a
+ valid ipaddress string. IPv4 addresses are supported on all platforms.
+ IPv6 addresses are supported on platforms with IPv6 support (AF_INET6
+ and inet_pton).
CertificateError is raised on failure. On success, the function
returns nothing.
@@ -258,7 +282,7 @@ def match_hostname(cert, hostname):
"SSL socket or SSL context with either "
"CERT_OPTIONAL or CERT_REQUIRED")
try:
- host_ip = ipaddress.ip_address(hostname)
+ host_ip = _inet_paton(hostname)
except ValueError:
# Not an IP address (common case)
host_ip = None
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index a48eb890da43..7aa112335cdb 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -622,14 +622,16 @@ def fail(cert, hostname):
fail(cert, 'example.net')
# -- IPv6 matching --
- cert = {'subject': ((('commonName', 'example.com'),),),
- 'subjectAltName': (('DNS', 'example.com'),
- ('IP Address', '2001:0:0:0:0:0:0:CAFE\n'),
- ('IP Address', '2003:0:0:0:0:0:0:BABA\n'))}
- ok(cert, '2001::cafe')
- ok(cert, '2003::baba')
- fail(cert, '2003::bebe')
- fail(cert, 'example.net')
+ if hasattr(socket, 'AF_INET6'):
+ cert = {'subject': ((('commonName', 'example.com'),),),
+ 'subjectAltName': (
+ ('DNS', 'example.com'),
+ ('IP Address', '2001:0:0:0:0:0:0:CAFE\n'),
+ ('IP Address', '2003:0:0:0:0:0:0:BABA\n'))}
+ ok(cert, '2001::cafe')
+ ok(cert, '2003::baba')
+ fail(cert, '2003::bebe')
+ fail(cert, 'example.net')
# -- Miscellaneous --
@@ -665,14 +667,45 @@ def fail(cert, hostname):
# Issue #17980: avoid denials of service by refusing more than one
# wildcard per fragment.
- cert = {'subject': ((('commonName', 'a*b.com'),),)}
- fail(cert, 'axxb.com')
- cert = {'subject': ((('commonName', 'a*b.co*'),),)}
- fail(cert, 'axxb.com')
- cert = {'subject': ((('commonName', 'a*b*.com'),),)}
- with self.assertRaises(ssl.CertificateError) as cm:
- ssl.match_hostname(cert, 'axxbxxc.com')
- self.assertIn("too many wildcards", str(cm.exception))
+ cert = {'subject': ((('commonName', 'a*b.example.com'),),)}
+ with self.assertRaisesRegex(
+ ssl.CertificateError,
+ "partial wildcards in leftmost label are not supported"):
+ ssl.match_hostname(cert, 'axxb.example.com')
+
+ cert = {'subject': ((('commonName', 'www.*.example.com'),),)}
+ with self.assertRaisesRegex(
+ ssl.CertificateError,
+ "wildcard can only be present in the leftmost label"):
+ ssl.match_hostname(cert, 'www.sub.example.com')
+
+ cert = {'subject': ((('commonName', 'a*b*.example.com'),),)}
+ with self.assertRaisesRegex(
+ ssl.CertificateError,
+ "too many wildcards"):
+ ssl.match_hostname(cert, 'axxbxxc.example.com')
+
+ cert = {'subject': ((('commonName', '*'),),)}
+ with self.assertRaisesRegex(
+ ssl.CertificateError,
+ "sole wildcard without additional labels are not support"):
+ ssl.match_hostname(cert, 'host')
+
+ cert = {'subject': ((('commonName', '*.com'),),)}
+ with self.assertRaisesRegex(
+ ssl.CertificateError,
+ r"hostname 'com' doesn't match '\*.com'"):
+ ssl.match_hostname(cert, 'com')
+
+ # extra checks for _inet_paton()
+ for invalid in ['1', '', '1.2.3', '256.0.0.1', '127.0.0.1/24']:
+ with self.assertRaises(ValueError):
+ ssl._inet_paton(invalid)
+ for ipaddr in ['127.0.0.1', '192.168.0.1']:
+ self.assertTrue(ssl._inet_paton(ipaddr))
+ if hasattr(socket, 'AF_INET6'):
+ for ipaddr in ['::1', '2001:db8:85a3::8a2e:370:7334']:
+ self.assertTrue(ssl._inet_paton(ipaddr))
def test_server_side(self):
# server_hostname doesn't work for server sockets
diff --git a/Misc/NEWS.d/next/Library/2018-02-11-15-54-41.bpo-32819.ZTRX2Q.rst b/Misc/NEWS.d/next/Library/2018-02-11-15-54-41.bpo-32819.ZTRX2Q.rst
new file mode 100644
index 000000000000..7d57bf697826
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-02-11-15-54-41.bpo-32819.ZTRX2Q.rst
@@ -0,0 +1,3 @@
+ssl.match_hostname() has been simplified and no longer depends on re and
+ipaddress module for wildcard and IP addresses. Error reporting for invalid
+wildcards has been improved.
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