cscan.py

# Copyright 2016(c) Hubert Kario
# This work is released under the Mozilla Public License Version 2.0
"""tlslite-ng based server configuration (and bug) scanner."""

from __future__ import print_function
from tlslite.messages import ClientHello, ServerHello, ServerHelloDone, Alert
from tlslite.constants import CipherSuite, \
        AlertLevel
import sys
import json
import getopt
import itertools

from cscan.scanner import Scanner
from cscan.config import Firefox_42
from cscan.modifiers import set_hello_version


def scan_with_config(host, port, conf, hostname, __sentry=None, __cache={}):
    """Connect to server and return set of exchanged messages."""
    assert __sentry is None
    key = (host, port, conf, hostname)
    if key in __cache:
        if verbose and not json_out:
            print(":", end='')
        return __cache[key]

    scanner = Scanner(conf, host, port, hostname)
    ret = scanner.scan()
    __cache[key] = ret
    if verbose and not json_out:
        print(".", end='')
        sys.stdout.flush()
    return ret


def simple_inspector(result):
    """
    Perform simple check to see if connection was successful.

    Returns True is connection was successful, server replied with
    ServerHello and ServerHelloDone messages, and the cipher selected
    was present in ciphers advertised by client, False otherwise
    """
    if any(isinstance(x, ServerHelloDone) for x in result):
        ch = next((x for x in result if isinstance(x, ClientHello)), None)
        sh = next((x for x in result if isinstance(x, ServerHello)), None)
        if ch and sh:
            if sh.cipher_suite not in ch.cipher_suites:
                # FAILURE cipher suite mismatch
                return False
            return True
    # incomplete response or error
    return False


def verbose_inspector(desc, result):
    """Describe the connection result in human-readable form."""
    ret = "{0}:".format(desc)
    if any(isinstance(x, ServerHelloDone) for x in result):
        ch = next((x for x in result if isinstance(x, ClientHello)), None)
        sh = next((x for x in result if isinstance(x, ServerHello)), None)
        if sh and ch:
            if sh.cipher_suite not in ch.cipher_suites:
                ret += " FAILURE cipher suite mismatch"
                return ret
            name = CipherSuite.ietfNames[sh.cipher_suite] \
                if sh.cipher_suite in CipherSuite.ietfNames \
                else hex(sh.cipher_suite)
            ret += " ok: {0}, {1}".format(sh.server_version,
                                          name)
            return ret
    ret += " FAILURE "
    errors = []
    for msg in result:
        if isinstance(msg, ClientHello):
            continue
        # check if returned message supports custom formatting
        if msg.__class__.__format__ is not object.__format__:
            errors += ["{:vxm}".format(msg)]
        else:
            errors += [repr(msg)]
        # skip printing close errors after fatal alerts, they are expected
        if isinstance(msg, Alert) and msg.level == AlertLevel.fatal:
            break
    ret += "\n".join(errors)
    return ret

configs = {}


def load_configs():
    """Load known client configurations for later use in scanning."""
    base_configs = [Firefox_42]
    for conf in base_configs:
        for version in ((3, 1), (3, 2), (3, 3), (3, 4), (3, 5), (3, 254)):
            if conf().version != version:
                # just changed version
                gen = set_hello_version(conf(), version)
                if gen.record_version > version:
                    gen.record_version = version
                configs[gen.name] = gen

    # Firefox 42 configs
    gen = Firefox_42()
    configs[gen.name] = gen


def scan_TLS_intolerancies(host, port, hostname):
    """Look for intolerancies (version, extensions, ...) in a TLS server."""
    results = {}

    def result_iterator(predicate):
        """
        Selecting iterator over cached results.

        Looks for matching result from already performed scans
        """
        return (not simple_inspector(results[name]) for name in results
                if predicate(configs[name]))

    def result_cache(name, conf):
        """Perform scan if config is not in results, caches result."""
        return results[name] if name in results \
            else results.setdefault(name, scan_with_config(host, port, conf,
                                                           hostname))

    def conf_iterator(predicate):
        """
        Caching, selecting iterator over configs.

        Returns an iterator that will go over configs that match the provided
        predicate (a function that returns true or false depending if given
        config is ok for test at hand) while saving the results to the
        cache/verbose `results` log/dictionary

        The iterator returns False for every connection that succeeded
        (meaning the server is NOT intolerant to config and True to mean
        that server IS intolerant to config.
        """
        scan_iter = (not simple_inspector(result_cache(name, conf))
                     for name, conf in configs.items()
                     if predicate(conf))
        return itertools.chain(result_iterator(predicate), scan_iter)

    host_up = not all(conf_iterator(lambda conf: True))

    intolerancies = {}
    if not host_up:
        if json_out:
            print(json.dumps(intolerancies))
        else:
            print("Host does not seem to support SSL or TLS protocol")
        return

    intolerancies["SSL 3.254"] = all(conf_iterator(lambda conf:
                                                   conf.version == (3, 254)))
    intolerancies["TLS 1.4"] = all(conf_iterator(lambda conf:
                                                 conf.version == (3, 5)))
    intolerancies["TLS 1.3"] = all(conf_iterator(lambda conf:
                                                 conf.version == (3, 4)))
    intolerancies["TLS 1.2"] = all(conf_iterator(lambda conf:
                                                 conf.version == (3, 3)))
    intolerancies["TLS 1.1"] = all(conf_iterator(lambda conf:
                                                 conf.version == (3, 2)))
    intolerancies["TLS 1.0"] = all(conf_iterator(lambda conf:
                                                 conf.version == (3, 1)))

    if json_out:
        print(json.dumps(intolerancies))
    else:
        if not no_header:
            if verbose:
                print()
            print("Host {0}:{1} scan complete".format(host, port))
            if hostname:
                print("SNI hostname used: {0}".format(hostname))
        if verbose:
            print()
            print("Individual probe results:")
            for desc, ret in sorted(results.items()):
                print(verbose_inspector(desc, ret))

        print()
        print("Intolerance to:")
        for intolerance, value in sorted(intolerancies.items()):
            print(" {0:20}: {1}".format(intolerance,
                                        "PRESENT" if value else "absent"))


def single_probe(name):
    """Run a single probe against a server, print result."""
    print(verbose_inspector(name, scan_with_config(host, port,
          configs[name], hostname)))


def usage():
    """Print usage information."""
    print("./cscan.py [ARGUMENTS] host[:port] [SNI-HOST-NAME]")
    print()
    print("-l, --list           List probe names")
    print("-p name, --probe     Run just a single probe")
    print("-j, --json           Output in JSON format")
    print("-v, --verbose        Use verbose output")

if __name__ == "__main__":
    try:
        opts, args = getopt.getopt(sys.argv[1:],
                                   "jvhlp:",
                                   ["json", "verbose", "help", "list",
                                    "probe=", "no-header"])
    except getopt.GetoptError as err:
        print(err)
        usage()
        sys.exit(2)

    json_out = False
    verbose = False
    list_probes = False
    run_probe = None
    no_header = False

    for opt, arg in opts:
        if opt in ('-j', '--json'):
            json_out = True
        elif opt in ('-v', '--verbose'):
            verbose = True
        elif opt in ('-h', '--help'):
            usage()
            sys.exit(0)
        elif opt in ('-l', '--list'):
            list_probes = True
        elif opt in ('-p', '--probe'):
            run_probe = arg
        elif opt in ('--no-header', ):
            no_header = True
        else:
            raise AssertionError("Unknown option {0}".format(opt))

    if len(args) > 2:
        print("Too many arguments")
        usage()
        sys.exit(2)

    load_configs()

    if list_probes:
        for desc, ret in sorted(configs.items()):
            print("{0}: {1}".format(desc, ret.__doc__))
        sys.exit(0)

    hostname = None
    if len(args) == 2:
        hostname = args[1]
    hostaddr = args[0].split(":")
    if len(hostaddr) > 1:
        host, port = hostaddr
    else:
        host = hostaddr[0]
        port = 443

    if run_probe:
        single_probe(run_probe)
    else:
        scan_TLS_intolerancies(host, port, hostname)