bpo-37463: match_hostname requires quad-dotted IPv4 (GH-14499)

ssl.match_hostname() no longer accepts IPv4 addresses with additional text
after the address and only quad-dotted notation without trailing
whitespaces. Some inet_aton() implementations ignore whitespace and all data
after whitespace, e.g. '127.0.0.1 whatever'.

Short notations like '127.1' for '127.0.0.1' were already filtered out.

The bug was initially found by Dominik Czarnota and reported by Paul Kehrer.

Signed-off-by: Christian Heimes <christian@python.org>
https://bugs.python.org/issue37463

diff --git a/Lib/ssl.py b/Lib/ssl.py
index 61bd775f759b09adda6ef4dcfad718f76eecf127..0726caee49aa579d5eb6d05c01f8aa0b04b17cb5 100644 (file)
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -327,12 +327,22 @@ def _inet_paton(ipname):
     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
+    # inet_aton() also accepts strings like '1', '127.1', some also trailing
+    # data like '127.0.0.1 whatever'.
+    try:
+        addr = _socket.inet_aton(ipname)
+    except OSError:
+        # not an IPv4 address
+        pass
+    else:
+        if _socket.inet_ntoa(addr) == ipname:
+            # only accept injective ipnames
+            return addr
+        else:
+            # refuse for short IPv4 notation and additional trailing data
+            raise ValueError(
+                "{!r} is not a quad-dotted IPv4 address.".format(ipname)
+            )
 
     try:
         return _socket.inet_pton(_socket.AF_INET6, ipname)
@@ -346,14 +356,15 @@ def _inet_paton(ipname):
     raise ValueError("{!r} is not an IPv4 address.".format(ipname))
 
 
-def _ipaddress_match(ipname, host_ip):
+def _ipaddress_match(cert_ipaddress, host_ip):
     """Exact matching of IP addresses.
 
     RFC 6125 explicitly doesn't define an algorithm for this
     (section 1.7.2 - "Out of Scope").
     """
-    # OpenSSL may add a trailing newline to a subjectAltName's IP address
-    ip = _inet_paton(ipname.rstrip())
+    # OpenSSL may add a trailing newline to a subjectAltName's IP address,
+    # commonly woth IPv6 addresses. Strip off trailing \n.
+    ip = _inet_paton(cert_ipaddress.rstrip())
     return ip == host_ip
 
 

diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index ef1723903a159bd0e15f1dbeeadc5a5b5ae46d03..d2b9e2046d0eecf7132db24640474f7f19c5ae45 100644 (file)
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -669,9 +669,14 @@ class BasicSocketTests(unittest.TestCase):
         cert = {'subject': ((('commonName', 'example.com'),),),
                 'subjectAltName': (('DNS', 'example.com'),
                                    ('IP Address', '10.11.12.13'),
-                                   ('IP Address', '14.15.16.17'))}
+                                   ('IP Address', '14.15.16.17'),
+                                   ('IP Address', '127.0.0.1'))}
         ok(cert, '10.11.12.13')
         ok(cert, '14.15.16.17')
+        # socket.inet_ntoa(socket.inet_aton('127.1')) == '127.0.0.1'
+        fail(cert, '127.1')
+        fail(cert, '14.15.16.17 ')
+        fail(cert, '14.15.16.17 extra data')
         fail(cert, '14.15.16.18')
         fail(cert, 'example.net')
 
@@ -684,6 +689,8 @@ class BasicSocketTests(unittest.TestCase):
                         ('IP Address', '2003:0:0:0:0:0:0:BABA\n'))}
             ok(cert, '2001::cafe')
             ok(cert, '2003::baba')
+            fail(cert, '2003::baba ')
+            fail(cert, '2003::baba extra data')
             fail(cert, '2003::bebe')
             fail(cert, 'example.net')
 

diff --git a/Misc/NEWS.d/next/Security/2019-07-01-08-46-14.bpo-37463.1CHwjE.rst b/Misc/NEWS.d/next/Security/2019-07-01-08-46-14.bpo-37463.1CHwjE.rst
new file mode 100644 (file)
index 0000000..4f4a62e
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2019-07-01-08-46-14.bpo-37463.1CHwjE.rst
@@ -0,0 +1,4 @@
+ssl.match_hostname() no longer accepts IPv4 addresses with additional text
+after the address and only quad-dotted notation without trailing
+whitespaces. Some inet_aton() implementations ignore whitespace and all data
+after whitespace, e.g. '127.0.0.1 whatever'.