commit 428e8e827e6f457aaf987be753b4f99c5127f750 Author: Arturo Filastò art@torproject.org Date: Mon Jul 9 12:41:49 2012 +0200
Port Isis's captive portal test to the new framework. --- ooni/plugins/captiveportal.py | 625 +++++++++++++++++++++++++++++++++++++++++ 1 files changed, 625 insertions(+), 0 deletions(-)
diff --git a/ooni/plugins/captiveportal.py b/ooni/plugins/captiveportal.py new file mode 100644 index 0000000..9b7bee3 --- /dev/null +++ b/ooni/plugins/captiveportal.py @@ -0,0 +1,625 @@ +# -*- coding: utf-8 -*- +""" + captiveportal + ************* + + This test is a collection of tests to detect the presence of a + captive portal. Code is taken, in part, from the old ooni-probe, + which was written by Jacob Appelbaum and Arturo Filastò. + + :copyright: (c) 2012 Isis Lovecruft + :license: see LICENSE for more details +""" +import base64 +import os +import random +import re +import string +import urllib2 +from urlparse import urlparse + +from zope.interface import implements +from twisted.python import usage +from twisted.plugin import IPlugin + +from ooni.plugoo.assets import Asset +from ooni.plugoo.tests import ITest, OONITest +from ooni.protocols import http +from ooni import log + +try: + from dns import resolver +except ImportError: + print "The dnspython module was not found. https://crate.io/packages/dnspython/" + +__plugoo__ = "captiveportal" +__desc__ = "Captive portal detection test" + +class CaptivePortalArgs(usage.Options): + optParameters = [['asset', 'a', None, 'Asset file'], + ['resume', 'r', 0, 'Resume at this index'], + ['experiment-url', 'e', 'http://google.com/', 'Experiment URL'], + ['user-agent', 'u', random.choice(http.useragents), + 'User agent for HTTP requests'] + ] + +class CaptivePortal(OONITest): + """ + Compares content and status codes of HTTP responses, and attempts + to determine if content has been altered. + """ + + implements(IPlugin, ITest) + + shortName = "captivep" + description = "Captive Portal Test" + requirements = None + options = CaptivePortalArgs + # Tells this to be blocking. + blocking = True + + def http_fetch(self, url, headers={}): + """ + Parses an HTTP url, fetches it, and returns a urllib2 response + object. + """ + url = urlparse(url).geturl() + request = urllib2.Request(url, None, headers) + response = urllib2.urlopen(request) + response_headers = dict(response.headers) + return response, response_headers + + def http_content_match_fuzzy_opt(self, experimental_url, control_result, + headers=None, fuzzy=False): + """ + Makes an HTTP request on port 80 for experimental_url, then + compares the response_content of experimental_url with the + control_result. Optionally, if the fuzzy parameter is set to + True, the response_content is compared with a regex of the + control_result. If the response_content from the + experimental_url and the control_result match, returns True + with the HTTP status code and headers; False, status code, and + headers if otherwise. + """ + + if headers is None: + default_ua = self.local_options['user-agent'] + headers = {'User-Agent': default_ua} + + response, response_headers = self.http_fetch(experimental_url, headers) + response_content = response.read() + response_code = response.code + if response_content is not None: + if fuzzy: + pattern = re.compile(control_result) + match = pattern.search(response_content) + if not match: + log.msg("Fuzzy HTTP content comparison for experiment URL") + log.msg("'%s'" % experimental_url) + log.msg("does not match!") + return False, response_code, response_headers + else: + log.msg("Fuzzy HTTP content comparison of experiment URL") + log.msg("'%s'" % experimental_url) + log.msg("and the expected control result yielded a match.") + return True, response_code, response_headers + else: + if str(response_content) != str(control_result): + log.msg("HTTP content comparison of experiment URL") + log.msg("'%s'" % experimental_url) + log.msg("and the expected control result do not match.") + return False, response_code, response_headers + else: + return True, response_code, response_headers + else: + log.warn("HTTP connection appears to have failed.") + return False, False, False + + def http_status_code_match(self, experiment_code, control_code): + """ + Compare two HTTP status codes, returns True if they match. + """ + if int(experiment_code) != int(control_code): + return False + return True + + def http_status_code_no_match(self, experiment_code, control_code): + """ + Compare two HTTP status codes, returns True if they do not match. + """ + if self.http_status_code_match(experiment_code, control_code): + return False + return True + + def dns_resolve(self, hostname, nameserver=None): + """ + Resolves hostname(s) though nameserver to corresponding + address(es). hostname may be either a single hostname string, + or a list of strings. If nameserver is not given, use local + DNS resolver, and if that fails try using 8.8.8.8. + """ + + if isinstance(hostname, str): + hostname = [hostname] + + if nameserver is not None: + res = resolver.Resolver(configure=False) + res.nameservers = [nameserver] + else: + res = resolver.Resolver() + + response = [] + answer = None + + for hn in hostname: + try: + answer = res.query(hn) + except resolver.NoNameservers: + res.nameservers = ['8.8.8.8'] + try: + answer = res.query(hn) + except resolver.NXDOMAIN: + log.msg("DNS resolution for %s returned NXDOMAIN" % hn) + response.append('NXDOMAIN') + except resolver.NXDOMAIN: + log.msg("DNS resolution for %s returned NXDOMAIN" % hn) + response.append('NXDOMAIN') + finally: + if answer: + for addr in answer: + response.append(addr.address) + return response + + def dns_resolve_match(self, experiment_hostname, control_address): + """ + Resolve experiment_hostname, and check to see that it returns + an experiment_address which matches the control_address. If + they match, returns True and experiment_address; otherwise + returns False and experiment_address. + """ + experiment_address = self.dns_resolve(experiment_hostname) + if experiment_address: + if len(set(experiment_address) & set([control_address])) > 0: + return True, experiment_address + else: + log.msg("DNS comparison of control '%s' does not" % control_address) + log.msg("match experiment response '%s'" % experiment_address) + return False, experiment_address + else: + log.debug("dns_resolve() for %s failed" % experiment_hostname) + return None, experiment_address + + def get_auth_nameservers(self, hostname): + """ + Many CPs set a nameserver to be used. Let's query that + nameserver for the authoritative nameservers of hostname. + + The equivalent of: + $ dig +short NS ooni.nu + """ + res = resolver.Resolver() + answer = res.query(hostname, 'NS') + auth_nameservers = [] + for auth in answer: + auth_nameservers.append(auth.to_text()) + return auth_nameservers + + def hostname_to_0x20(self, hostname): + """ + MaKEs yOur HOsTnaME lOoK LiKE THis. + + For more information, see: + D. Dagon, et. al. "Increased DNS Forgery Resistance + Through 0x20-Bit Encoding". Proc. CSS, 2008. + """ + hostname_0x20 = '' + for char in hostname: + l33t = random.choice(['caps', 'nocaps']) + if l33t == 'caps': + hostname_0x20 = hostname_0x20 + char.capitalize() + else: + hostname_0x20 = hostname_0x20 + char.lower() + return hostname_0x20 + + def check_0x20_to_auth_ns(self, hostname, sample_size=None): + """ + Resolve a 0x20 DNS request for hostname over hostname's + authoritative nameserver(s), and check to make sure that + the capitalization in the 0x20 request matches that of the + response. Also, check the serial numbers of the SOA (Start + of Authority) records on the authoritative nameservers to + make sure that they match. + + If sample_size is given, a random sample equal to that number + of authoritative nameservers will be queried; default is 5. + """ + log.msg("") + log.msg("Testing random capitalization of DNS queries...") + log.msg("Testing that Start of Authority serial numbers match...") + + auth_nameservers = self.get_auth_nameservers(hostname) + + if sample_size is None: + sample_size = 5 + resolved_auth_ns = random.sample(self.dns_resolve(auth_nameservers), + sample_size) + + querynames = [] + answernames = [] + serials = [] + + # Even when gevent monkey patching is on, the requests here + # are sent without being 0x20'd, so we need to 0x20 them. + hostname = self.hostname_to_0x20(hostname) + + for auth_ns in resolved_auth_ns: + res = resolver.Resolver(configure=False) + res.nameservers = [auth_ns] + try: + answer = res.query(hostname, 'SOA') + except resolver.Timeout: + continue + querynames.append(answer.qname.to_text()) + answernames.append(answer.rrset.name.to_text()) + for soa in answer: + serials.append(str(soa.serial)) + + if len(set(querynames).intersection(answernames)) == 1: + log.msg("Capitalization in DNS queries and responses match.") + name_match = True + else: + log.msg("The random capitalization '%s' used in" % hostname) + log.msg("DNS queries to that hostname's authoritative") + log.msg("nameservers does not match the capitalization in") + log.msg("the response.") + name_match = False + + if len(set(serials)) == 1: + log.msg("Start of Authority serial numbers all match.") + serial_match = True + else: + log.msg("Some SOA serial numbers did not match the rest!") + serial_match = False + + ret = name_match, serial_match, querynames, answernames, serials + + if name_match and serial_match: + log.msg("Your DNS queries do not appear to be tampered.") + return ret + elif name_match or serial_match: + log.msg("Something is tampering with your DNS queries.") + return ret + elif not name_match and not serial_match: + log.msg("Your DNS queries are definitely being tampered with.") + return ret + + def get_random_url_safe_string(self, length): + """ + Returns a random url-safe string of specified length, where + 0 < length <= 256. The returned string will always start with + an alphabetic character. + """ + if (length <= 0): + length = 1 + elif (length > 256): + length = 256 + + random_ascii = base64.urlsafe_b64encode(os.urandom(int(length))) + + while not random_ascii[:1].isalpha(): + random_ascii = base64.urlsafe_b64encode(os.urandom(int(length))) + + three_quarters = int((len(random_ascii)) * (3.0/4.0)) + random_string = random_ascii[:three_quarters] + return random_string + + def get_random_hostname(self, length=None): + """ + Returns a random hostname with SLD of specified length. If + length is unspecified, length=32 is used. + + These *should* all resolve to NXDOMAIN. If they actually + resolve to a box that isn't part of a captive portal that + would be rather interesting. + """ + if length is None: + length = 32 + + random_sld = self.get_random_url_safe_string(length) + + # if it doesn't start with a letter, chuck it. + while not random_sld[:1].isalpha(): + random_sld = self.get_random_url_safe_string(length) + + tld_list = ['.com', '.net', '.org', '.info', '.test', '.invalid'] + random_tld = urllib2.random.choice(tld_list) + random_hostname = random_sld + random_tld + return random_hostname + + def compare_random_hostnames(self, hostname_count=None, hostname_length=None): + """ + Get hostname_count number of random hostnames with SLD length + of hostname_length, and then attempt DNS resolution. If no + arguments are given, default to three hostnames of 32 bytes + each. These random hostnames *should* resolve to NXDOMAIN, + except in the case where a user is presented with a captive + portal and remains unauthenticated, in which case the captive + portal may return the address of the authentication page. + + If the cardinality of the intersection of the set of resolved + random hostnames and the single element control set + (['NXDOMAIN']) are equal to one, then DNS properly resolved. + + Returns true if only NXDOMAINs were returned, otherwise returns + False with the relative complement of the control set in the + response set. + """ + if hostname_count is None: + hostname_count = 3 + + log.msg("Generating random hostnames...") + log.msg("Resolving DNS for %d random hostnames..." % hostname_count) + + control = ['NXDOMAIN'] + responses = [] + + for x in range(hostname_count): + random_hostname = self.get_random_hostname(hostname_length) + response_match, response_address = self.dns_resolve_match(random_hostname, + control[0]) + for address in response_address: + if response_match is False: + log.msg("Strangely, DNS resolution of the random hostname") + log.msg("%s actually points to %s" + % (random_hostname, response_address)) + responses = responses + [address] + else: + responses = responses + [address] + + intersection = set(responses) & set(control) + relative_complement = set(responses) - set(control) + r = set(responses) + + if len(intersection) == 1: + log.msg("All %d random hostnames properly resolved to NXDOMAIN." + % hostname_count) + return True, relative_complement + elif (len(intersection) == 1) and (len(r) > 1): + log.msg("Something odd happened. Some random hostnames correctly") + log.msg("resolved to NXDOMAIN, but several others resolved to") + log.msg("to the following addresses: %s" % relative_complement) + return False, relative_complement + elif (len(intersection) == 0) and (len(r) == 1): + log.msg("All random hostnames resolved to the IP address ") + log.msg("'%s', which is indicative of a captive portal." % r) + return False, relative_complement + else: + log.debug("Apparently, pigs are flying on your network, 'cause a") + log.debug("bunch of hostnames made from 32-byte random strings") + log.debug("just magically resolved to a bunch of random addresses.") + log.debug("That is definitely highly improbable. In fact, my napkin") + log.debug("tells me that the probability of just one of those") + log.degug("hostnames resolving to an address is 1.68e-59, making") + log.debug("it nearly twice as unlikely as an MD5 hash collision.") + log.debug("Either someone is seriously messing with your network,") + log.debug("or else you are witnessing the impossible. %s" % r) + return False, relative_complement + + def google_dns_cp_test(self): + """ + Google Chrome resolves three 10-byte random hostnames. + """ + subtest = "Google Chrome DNS-based" + + log.msg("") + log.msg("Running the Google Chrome DNS-based captive portal test...") + + gmatch, google_dns_result = self.compare_random_hostnames(3, 10) + + if gmatch: + log.msg("Google Chrome DNS-based captive portal test did not") + log.msg("detect a captive portal.") + return google_dns_result + else: + log.msg("Google Chrome DNS-based captive portal test believes") + log.msg("you are in a captive portal, or else something very") + log.msg("odd is happening with your DNS.") + return google_dns_result + + def ms_dns_cp_test(self): + """ + Microsoft "phones home" to a server which will always resolve + to the same address. + """ + subtest = "Microsoft NCSI DNS-based" + + log.msg("") + log.msg("Running the Microsoft NCSI DNS-based captive portal") + log.msg("test...") + + msmatch, ms_dns_result = self.dns_resolve_match("dns.msftncsi.com", + "131.107.255.255") + if msmatch: + log.msg("Microsoft NCSI DNS-based captive portal test did not") + log.msg("detect a captive portal.") + return ms_dns_result + else: + log.msg("Microsoft NCSI DNS-based captive portal test ") + log.msg("believes you are in a captive portal.") + return ms_dns_result + + def run_vendor_dns_tests(self): + """ + Run the vendor DNS tests. + """ + report = {} + report['google_dns_cp'] = self.google_dns_cp_test() + report['ms_dns_cp'] = self.ms_dns_cp_test() + + return report + + def run_vendor_tests(self, *a, **kw): + """ + These are several vendor tests used to detect the presence of + a captive portal. Each test compares HTTP status code and + content to the control results and has its own User-Agent + string, in order to emulate the test as it would occur on the + device it was intended for. Vendor tests are defined in the + format: + [exp_url, ctrl_result, ctrl_code, ua, test_name] + """ + + vendor_tests = [['http://www.apple.com/library/test/success.html', + 'Success', + '200', + 'Mozilla/5.0 (iPhone; U; CPU like Mac OS X; en) AppleWebKit/420+ (KHTML, like Gecko) Version/3.0 Mobile/1A543a Safari/419.3', + 'Apple HTTP Captive Portal'], + ['http://tools.ietf.org/html/draft-nottingham-http-portal-02', + '428 Network Authentication Required', + '428', + 'Mozilla/5.0 (Windows NT 6.1; rv:5.0) Gecko/20100101 Firefox/5.0', + 'W3 Captive Portal'], + ['http://www.msftncsi.com/ncsi.txt', + 'Microsoft NCSI', + '200', + 'Microsoft NCSI', + 'MS HTTP Captive Portal',]] + + cm = self.http_content_match_fuzzy_opt + sm = self.http_status_code_match + snm = self.http_status_code_no_match + + def compare_content(status_func, fuzzy, experiment_url, control_result, + control_code, headers, test_name): + log.msg("") + log.msg("Running the %s test..." % test_name) + + content_match, experiment_code, experiment_headers = cm(experiment_url, + control_result, + headers, fuzzy) + status_match = status_func(experiment_code, control_code) + + if status_match and content_match: + log.msg("The %s test was unable to detect" % test_name) + log.msg("a captive portal.") + return True + else: + log.msg("The %s test shows that your network" % test_name) + log.msg("is filtered.") + return False + + result = [] + for vt in vendor_tests: + report = {} + report['vt'] = vt + + experiment_url = vt[0] + control_result = vt[1] + control_code = vt[2] + headers = {'User-Agent': vt[3]} + test_name = vt[4] + + args = (experiment_url, control_result, control_code, headers, test_name) + + if test_name == "MS HTTP Captive Portal": + report['result'] = compare_content(sm, False, *args) + + elif test_name == "Apple HTTP Captive Portal": + report['result'] = compare_content(sm, True, *args) + + elif test_name == "W3 Captive Portal": + report['result'] = compare_content(snm, True, *args) + + else: + log.warn("Ooni is trying to run an undefined CP vendor test.") + result.append(report) + return result + + def control(self, experiment_result, args): + """ + Compares the content and status code of the HTTP response for + experiment_url with the control_result and control_code + respectively. If the status codes match, but the experimental + content and control_result do not match, fuzzy matching is enabled + to determine if the control_result is at least included somewhere + in the experimental content. Returns True if matches are found, + and False if otherwise. + """ + experiment_url = self.local_options['experiment-url'] + control_result = 'XX' + control_code = 200 + ua = self.local_options['user-agent'] + + cm = self.http_content_match_fuzzy_opt + sm = self.http_status_code_match + snm = self.http_status_code_no_match + + log.msg("Running test for '%s'..." % experiment_url) + content_match, experiment_code, experiment_headers = cm(experiment_url, + control_result) + status_match = sm(experiment_code, control_code) + if status_match and content_match: + log.msg("The test for '%s'" % experiment_url) + log.msg("was unable to detect a captive portal.") + return experiment_result, True + + elif status_match and not content_match: + log.msg("Retrying '%s' with fuzzy match enabled." + % experiment_url) + fuzzy_match, experiment_code, experiment_headers = cm(experiment_url, + control_result, + fuzzy=True) + if fuzzy_match: + return experiment_result, True + else: + log.msg("Found modified content on '%s'," % experiment_url) + log.msg("which could indicate a captive portal.") + + return experiment_result, False + else: + log.msg("The content comparison test for ") + log.msg("'%s'" % experiment_url) + log.msg("shows that your HTTP traffic is filtered.") + return experiment_result, False + + def experiment(self, args): + """ + Runs the CaptivePortal(Test). + + CONFIG OPTIONS + -------------- + + If "do_captive_portal_vendor_tests" is set to "true", then vendor + specific captive portal HTTP-based tests will be run. + + If "do_captive_portal_dns_tests" is set to "true", then vendor + specific captive portal DNS-based tests will be run. + + If "check_dns_requests" is set to "true", then Ooni-probe will + attempt to check that your DNS requests are not being tampered with + by a captive portal. + + If "captive_portal" = "yourfilename.txt", then user-specified tests + will be run. + + Any combination of the above tests can be run. + """ + report = {} + + log.msg("") + log.msg("Running vendor tests...") + report['vendor_tests'] = self.run_vendor_tests() + + log.msg("") + log.msg("Running vendor DNS-based tests...") + report['vendor_dns_tests'] = self.run_vendor_dns_tests() + + log.msg("") + log.msg("Checking that DNS requests are not being tampered...") + report['check0x20'] = self.check_0x20_to_auth_ns('ooni.nu') + + log.msg("") + log.msg("Captive portal test finished!") + return report + +cp = CaptivePortal(None, None, None)