From 3d7524ab7da01cab4d7dd3857e56fd11e82c061e Mon Sep 17 00:00:00 2001
From: Bob Halley <halley@nominum.com>
Date: Fri, 8 Jul 2011 09:57:41 -0700
Subject: [PATCH] make IP address parsing stricter

---
 ChangeLog   | 10 ++++++++++
 dns/ipv4.py | 34 +++++++++++++++++-----------------
 dns/ipv6.py | 13 ++++++++++---
 3 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 94eca92a..08d93d83 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2011-07-08  Bob Halley  <halley@dnspython.org>
+
+	* dns/ipv4.py: dnspython now provides its own, stricter, versions
+	  of IPv4 inet_ntoa() and inet_aton() instead of using the OS's
+	  versions.
+
+	* dns/ipv6.py: inet_aton() now bounds checks embedded IPv4 addresses
+	  more strictly.  Also, now only dns.exception.SyntaxError can be
+	  raised on bad input.
+
 2011-04-05  Bob Halley  <halley@dnspython.org>
 
 	* Old DNSSEC types (KEY, NXT, and SIG) have been removed.
diff --git a/dns/ipv4.py b/dns/ipv4.py
index 8d45b44e..ec7d2d24 100644
--- a/dns/ipv4.py
+++ b/dns/ipv4.py
@@ -15,22 +15,22 @@
 
 """IPv4 helper functions."""
 
-import socket
-import sys
+import struct
 
-if sys.hexversion < 0x02030000 or sys.platform == 'win32':
-    #
-    # Some versions of Python 2.2 have an inet_aton which rejects
-    # the valid IP address '255.255.255.255'.  It appears this
-    # problem is still present on the Win32 platform even in 2.3.
-    # We'll work around the problem.
-    #
-    def inet_aton(text):
-        if text == '255.255.255.255':
-            return '\xff' * 4
-        else:
-            return socket.inet_aton(text)
-else:
-    inet_aton = socket.inet_aton
+import dns.exception
 
-inet_ntoa = socket.inet_ntoa
+def inet_ntoa(address):
+    if len(address) != 4:
+        raise dns.exception.SyntaxError
+    return '%u.%u.%u.%u' % (ord(address[0]), ord(address[1]),
+                            ord(address[2]), ord(address[3]))
+
+def inet_aton(text):
+    parts = text.split('.')
+    if len(parts) != 4:
+        raise dns.exception.SyntaxError
+    try:
+        bytes = [int(part) for part in parts]
+        return struct.pack('BBBB', *bytes)
+    except:
+        raise dns.exception.SyntaxError
diff --git a/dns/ipv6.py b/dns/ipv6.py
index 8363fe42..78fe82ec 100644
--- a/dns/ipv6.py
+++ b/dns/ipv6.py
@@ -113,9 +113,16 @@ def inet_aton(text):
     #
     m = _v4_ending.match(text)
     if not m is None:
-        text = "%s:%04x:%04x" % (m.group(1),
-                                 int(m.group(2)) * 256 + int(m.group(3)),
-                                 int(m.group(4)) * 256 + int(m.group(5)))
+        try:
+            b1 = int(m.group(2))
+            b2 = int(m.group(3))
+            b3 = int(m.group(4))
+            b4 = int(m.group(5))
+        except:
+            raise dns.exception.SyntaxError
+        if b1 > 255 or b2 > 255 or b3 > 255 or b4 > 255:
+            raise dns.exception.SyntaxError
+        text = "%s:%04x:%04x" % (m.group(1), b1 * 256 + b2, b3 * 256 + b4)
     #
     # Try to turn '::<whatever>' into ':<whatever>'; if no match try to
     # turn '<whatever>::' into '<whatever>:'
-- 
2.47.3