IP Recognizer has bugs when ipv6 contains double colon ::

[yungyuchen521]

Describe the bug

The regex doesn't work correctly on ipv6 with double colons ::

Case	Example	Matches	Expected
Valid address with ::	A099::09C0:876A:130B	["A099::"]	["A099::09C0:876A:130B"]
Invalid address with multiple ::	2001::25de::cade	["2001::", "25de::"]	[]

To Reproduce

import re

PATTERN = re.compile(r"\b(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))\b")

VALID_IP_WITH_DOUBLE_COLON = "A099::09C0:876A:130B"
INVALID_IP_WITH_MULTI_DOUBLE_COLON = "2001::25de::cade"

print([r for r in PATTERN.finditer(VALID_IP_WITH_DOUBLE_COLON)])
print([r for r in PATTERN.finditer(INVALID_IP_WITH_MULTI_DOUBLE_COLON)])

# output
[<re.Match object; span=(0, 6), match='A099::'>]
[<re.Match object; span=(0, 6), match='2001::'>, <re.Match object; span=(6, 12), match='25de::'>]

Fixes

Valid address with ::

Root Cause

The regex begins with {1,7}::, then {1,6}::{1}, then {1,5}::{1,2}, ..., and finally {1}::{1,6} and ::{1,7}. For A099::09C0:876A:130B, it stops when seeing A099:: (corresponds to {1,7}::). But it should match {1}::{1,6}.

Solution

Reverse the order of patterns with ::
i.e. ([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)
-> :((:[0-9a-fA-F]{1,4}){1,7}|:)|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:

Invalid address with multiple ::

Root Cause

\b treats colon : as a non-word character. Consequently, 1:, :2 and e: in 2001::25de::cade are consider word boundary.

Solution

Replace \b with a look-around which denies :
i.e. \b......\b -> (?<![\w:])......(?![\w:])