[Python-checkins] [3.8] bpo-36384: Leading zeros in IPv4 addresses are no longer tolerated (GH-25099) (GH-27801)
ambv
webhook-mailer at python.org
Tue Aug 17 19:46:43 EDT 2021
https://github.com/python/cpython/commit/03dd89d62413c4a92831ed1b36e2ae8983bcb2d4
commit: 03dd89d62413c4a92831ed1b36e2ae8983bcb2d4
branch: 3.8
author: achraf-mer <51244975+achraf-mer at users.noreply.github.com>
committer: ambv <lukasz at langa.pl>
date: 2021-08-18T01:46:37+02:00
summary:
[3.8] bpo-36384: Leading zeros in IPv4 addresses are no longer tolerated (GH-25099) (GH-27801)
Reverts commit e653d4d8e820a7a004ad399530af0135b45db27a and makes
parsing even more strict. Like socket.inet_pton() any leading zero
is now treated as invalid input.
Signed-off-by: Christian Heimes <christian at python.org>
Co-authored-by: Łukasz Langa <lukasz at langa.pl>
files:
A Misc/NEWS.d/next/Security/2021-03-30-16-29-51.bpo-36384.sCAmLs.rst
M Doc/library/ipaddress.rst
M Doc/whatsnew/3.8.rst
M Lib/ipaddress.py
M Lib/test/test_ipaddress.py
diff --git a/Doc/library/ipaddress.rst b/Doc/library/ipaddress.rst
index 2cdfddb02e96c4..5e21d5db2ed9c3 100644
--- a/Doc/library/ipaddress.rst
+++ b/Doc/library/ipaddress.rst
@@ -104,8 +104,7 @@ write code that handles both IP versions correctly. Address objects are
1. A string in decimal-dot notation, consisting of four decimal integers in
the inclusive range 0--255, separated by dots (e.g. ``192.168.0.1``). Each
integer represents an octet (byte) in the address. Leading zeroes are
- tolerated only for values less than 8 (as there is no ambiguity
- between the decimal and octal interpretations of such strings).
+ not tolerated to prevent confusion with octal notation.
2. An integer that fits into 32 bits.
3. An integer packed into a :class:`bytes` object of length 4 (most
significant octet first).
@@ -117,6 +116,18 @@ write code that handles both IP versions correctly. Address objects are
>>> ipaddress.IPv4Address(b'\xC0\xA8\x00\x01')
IPv4Address('192.168.0.1')
+
+ .. versionchanged:: 3.8
+
+ Leading zeros are tolerated, even in ambiguous cases that look like
+ octal notation.
+
+ .. versionchanged:: 3.8.12
+
+ Leading zeros are no longer tolerated and are treated as an error.
+ IPv4 address strings are now parsed as strict as glibc
+ :func:`~socket.inet_pton`.
+
.. attribute:: version
The appropriate version number: ``4`` for IPv4, ``6`` for IPv6.
diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst
index 109a06e92efb7d..7a3460adb3827f 100644
--- a/Doc/whatsnew/3.8.rst
+++ b/Doc/whatsnew/3.8.rst
@@ -2307,3 +2307,19 @@ URL by the parser in :mod:`urllib.parse` preventing such attacks. The removal
characters are controlled by a new module level variable
``urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE``. (See :issue:`43882`)
+
+Notable changes in Python 3.8.12
+================================
+
+Changes in the Python API
+-------------------------
+
+Starting with Python 3.8.12 the :mod:`ipaddress` module no longer accepts
+any leading zeros in IPv4 address strings. Leading zeros are ambiguous and
+interpreted as octal notation by some libraries. For example the legacy
+function :func:`socket.inet_aton` treats leading zeros as octal notatation.
+glibc implementation of modern :func:`~socket.inet_pton` does not accept
+any leading zeros.
+
+(Originally contributed by Christian Heimes in :issue:`36384`, and backported
+to 3.8 by Achraf Merzouki)
diff --git a/Lib/ipaddress.py b/Lib/ipaddress.py
index 28b7b6159a62ef..d351f07a5bd960 100644
--- a/Lib/ipaddress.py
+++ b/Lib/ipaddress.py
@@ -1173,6 +1173,11 @@ def _parse_octet(cls, octet_str):
if len(octet_str) > 3:
msg = "At most 3 characters permitted in %r"
raise ValueError(msg % octet_str)
+ # Handle leading zeros as strict as glibc's inet_pton()
+ # See security bug bpo-36384
+ if octet_str != '0' and octet_str[0] == '0':
+ msg = "Leading zeros are not permitted in %r"
+ raise ValueError(msg % octet_str)
# Convert to integer (we know digits are legal)
octet_int = int(octet_str, 10)
if octet_int > 255:
diff --git a/Lib/test/test_ipaddress.py b/Lib/test/test_ipaddress.py
index 2f1c5b6b6fb9c8..1297b8371d8583 100644
--- a/Lib/test/test_ipaddress.py
+++ b/Lib/test/test_ipaddress.py
@@ -97,10 +97,23 @@ def pickle_test(self, addr):
class CommonTestMixin_v4(CommonTestMixin):
def test_leading_zeros(self):
- self.assertInstancesEqual("000.000.000.000", "0.0.0.0")
- self.assertInstancesEqual("192.168.000.001", "192.168.0.1")
- self.assertInstancesEqual("016.016.016.016", "16.16.16.16")
- self.assertInstancesEqual("001.000.008.016", "1.0.8.16")
+ # bpo-36384: no leading zeros to avoid ambiguity with octal notation
+ msg = "Leading zeros are not permitted in '\d+'"
+ addresses = [
+ "000.000.000.000",
+ "192.168.000.001",
+ "016.016.016.016",
+ "192.168.000.001",
+ "001.000.008.016",
+ "01.2.3.40",
+ "1.02.3.40",
+ "1.2.03.40",
+ "1.2.3.040",
+ ]
+ for address in addresses:
+ with self.subTest(address=address):
+ with self.assertAddressError(msg):
+ self.factory(address)
def test_int(self):
self.assertInstancesEqual(0, "0.0.0.0")
diff --git a/Misc/NEWS.d/next/Security/2021-03-30-16-29-51.bpo-36384.sCAmLs.rst b/Misc/NEWS.d/next/Security/2021-03-30-16-29-51.bpo-36384.sCAmLs.rst
new file mode 100644
index 00000000000000..f956cde948ec57
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2021-03-30-16-29-51.bpo-36384.sCAmLs.rst
@@ -0,0 +1,6 @@
+:mod:`ipaddress` module no longer accepts any leading zeros in IPv4 address
+strings. Leading zeros are ambiguous and interpreted as octal notation by
+some libraries. For example the legacy function :func:`socket.inet_aton`
+treats leading zeros as octal notatation. glibc implementation of modern
+:func:`~socket.inet_pton` does not accept any leading zeros. For a while
+the :mod:`ipaddress` module used to accept ambiguous leading zeros.
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