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#!/usr/bin/env python2.7

from lxml import etree

import regex

# XXX: this doesn't work for from patterns that use the ?: in (?:www\.)?

# (one of many examples in Zoosk.com.xml)

# XXX: this doesn't figure out if a target host causes a particular rule

# to be completely inapplicable (in which case it should probably be

# ignored) for determining simplicity

# XXX: this doesn't catch simple rules that use alternation with

# backreferences, like from="^http://(foo|bar)\.example\.com/"

# to="\1.example.com"

def simple(f):

tree = etree.parse(f)

targets = [target.attrib["host"] for target in tree.xpath("/ruleset/target")]

return all([

# ruleset must not be default_off

"default_off" not in tree.xpath("/ruleset")[0].attrib,

# ruleset must not contain a match_rule

"match_rule" not in tree.xpath("/ruleset")[0].attrib,

# XXX: maybe also check for platform="mixedcontent" here

# ruleset must not apply any securecookie patterns

not tree.xpath("/ruleset/securecookie"),

# ruleset must not contain any exclusions

not tree.xpath("/ruleset/exclusion"),

# targets must not contain any wildcards

not any("*" in target for target in targets),

# ruleset must not contain any downgrade rules

not any("downgrade" in rule.attrib for rule in tree.xpath("/ruleset/rule")),

# and every rule must itself be simple according to the criteria below

all(simple_rule(rule, targets) for rule in tree.xpath("/ruleset/rule"))

])

def simple_rule(rule, targets):

"""Is this rule a simple rule? A simple rule rewrites a single hostname,

perhaps with an optional leading www\., to itself or to itself plus www.,

at the top level with no other effects."""

rule_from = rule.attrib["from"]

rule_to = rule.attrib["to"]

# Simple rule with no capture

if regex.match(r"^\^http://[-A-Za-z0-9.\\]+/$", rule_from):

applicable_host = unescape(regex.search(r"^\^http://([-A-Za-z0-9.\\])+/$", rule_from).groups()[0])

if regex.match(r"^https://%s/" % applicable_host, rule_to) or regex.match("r^https://%s/" % applicable_host, rule_to):

return True

else:

return False

# Optional www

if regex.match(r"^\^http://\(www\\\.\)\?[-A-Za-z0-9.\\]+/$", rule_from):

applicable_host = unescape(regex.search(r"^\^http://\(www\\\.\)\?([-A-Za-z0-9.\\]+)/$", rule_from).groups()[0])

if regex.match(r"^https://www\.%s/" % applicable_host, rule_to) or regex.match(r"^https://%s/" % applicable_host, rule_to):

return True

else:

return False

return False

def unescape(s):

return s.replace(r"\.", ".")