Module refinery.units.pattern.xtp

Classes

class LetterWeight (weight)

Expand source code Browse git

class LetterWeight:
    def __init__(self, weight):
        try:
            self._weights = weight._weights
        except AttributeError:
            pass
        else:
            return
        self._weights = {
            letter: weight for letters, weight in weight.items() for letter in letters
        }
        for letter in range(0x100):
            self._weights.setdefault(letter, 0)

    def __call__(self, data: AnyStr) -> float:
        if isinstance(data, str):
            data = data.encode('latin1')
        return sum(self._weights[c] for c in data) / len(data) / max(self._weights.values())

Subclasses

• LetterWeights

class LetterWeights (weight)

An enumeration.

Expand source code Browse git

class LetterWeights(LetterWeight, Enum):
    IOC = LetterWeight({
        B'^`': 1,
        B'!$%&()*+-<=>?[]{}~\t': 2,
        B'ABCDEFGHIJKLMNOPQRSTUVWXYZ': 4,
        B'.,:;#/\\|@_ ': 5,
        B'0123456789abcdefghijklmnopqrstuvwxyz': 8,
    })
    Path = LetterWeight({
        B'^`': 1,
        B'$%&()*+-<=>?[]{}~\t': 2,
        B'.,:;#/\\|@_ ': 4,
        B'0123456789': 4,
        B'ABCDEFGHIJKLMNOPQRSTUVWXYZ': 5,
        B'abcdefghijklmnopqrstuvwxyz': 8,
    })

Ancestors

• LetterWeight
• enum.Enum

Class variables

var IOC

var Path

class xtp (*pattern, filter=0, min=1, max=None, len=None, stripspace=False, duplicates=False, longest=False, take=None)

Extract Patterns: Uses regular expressions to extract indicators from the input data and optionally filters these results heuristically. The unit is designed to extract indicators such as domain names and IP addresses, see below for a complete list. To extract data formats such as hex-encoded data, use carve.

Expand source code Browse git

class xtp(PatternExtractor):
    """
    Extract Patterns: Uses regular expressions to extract indicators from the input data and
    optionally filters these results heuristically. The unit is designed to extract indicators
    such as domain names and IP addresses, see below for a complete list. To extract data
    formats such as hex-encoded data, use `refinery.carve`.
    """

    def __init__(
        self,
        *pattern: Arg('pattern', type=str,
            default=(
                indicators.hostname.name,
                indicators.url.name,
                indicators.email.name,
            ), help=(
                'Choose the pattern to extract. The unit uses {{default}} by default. Use an '
                'asterix character to select all available patterns. The available patterns '
                'are: {}'.format(', '.join(p.display for p in indicators))
            )
        ),
        filter: Arg('-f', dest='filter', action='count',
            help=(
                'If this setting is enabled, the xtp unit will attempt to reduce the number '
                'of false positives by certain crude heuristics. Specify multiple times to '
                'make the filtering more aggressive.'
            )
        ) = 0,
        min=1, max=None, len=None, stripspace=False, duplicates=False, longest=False, take=None
    ):
        self.superinit(super(), **vars(), ascii=True, utf16=True)

        patterns = {
            p for name in pattern for p in indicators if fnmatch(p.display, name)
        }
        # if indicators.hostname in patterns:
        #     patterns.remove(indicators.hostname)
        #     patterns.add(indicators.ipv4)
        #     patterns.add(indicators.domain)
        patterns = [F'(?P<{p.name}>{p.value})' for p in patterns]
        if not patterns:
            raise RefineryCriticalException('The given mask does not match any known indicator pattern.')
        pattern = '|'.join(patterns)
        self.args.pattern = re.compile(pattern.encode(self.codec), flags=re.DOTALL)
        self.args.filter = filter

    _ALPHABETIC = ascii_letters.encode('ASCII')
    _LEGITIMATE_HOSTS = {
        'acm.org'                 : 1,
        'adobe.com'               : 1,
        'aka.ms'                  : 1,
        'android.com'             : 1,
        'apache.org'              : 1,
        'apple.com'               : 1,
        'archive.org'             : 2,
        'azure.com'               : 1,
        'baidu.com'               : 2,
        'bootstrapcdn.com'        : 2,
        'cdnjs.cloudflare.com'    : 4,
        'comodo.net'              : 1,
        'comodoca.com'            : 1,
        'curl.haxx.se'            : 1,
        'curl.se'                 : 1,
        'digicert.com'            : 1,
        'dublincore.org'          : 1,
        'fontawesome.com'         : 1,
        'facebook.com'            : 4,
        'github.com'              : 3,
        'globalsign.com'          : 1,
        'globalsign.net'          : 1,
        'godaddy.com'             : 1,
        'google.com'              : 4,
        'googleapis.com'          : 5,
        'googleusercontent.com'   : 5,
        'gov'                     : 2,
        'gstatic.com'             : 2,
        'iana.org'                : 1,
        'intel.com'               : 1,
        'jquery.com'              : 1,
        'jsdelivr.net'            : 2,
        'live.com'                : 1,
        'microsoft.com'           : 1,
        'msdn.com'                : 1,
        'msn.com'                 : 1,
        'office.com'              : 1,
        'office365.com'           : 2,
        'openssl.org'             : 1,
        'openxmlformats.org'      : 1,
        'purl.org'                : 1,
        'python.org'              : 1,
        'schema.org'              : 2,
        'sectigo.com'             : 1,
        'skype.com'               : 1,
        'sourceforge.net'         : 4,
        'sway-cdn.com'            : 1,
        'sway-extensions.com'     : 1,
        'symantec.com'            : 1,
        'symauth.com'             : 1,
        'symcb.com'               : 1,
        'symcd.com'               : 1,
        'thawte.com'              : 1,
        'usertrust.com'           : 1,
        'verisign.com'            : 1,
        'w3.org'                  : 1,
        'wikipedia.org'           : 1,
        'wolfram.com'             : 1,
        'xml.org'                 : 1,
        'xmlsoap.org'             : 1,
        'yahoo.com'               : 1,
    }

    _DOMAIN_WHITELIST = [
        'system.net',
        'wscript.shell',
    ]

    _BRACKETING = {
        B"'"[0]: B"'",
        B'"'[0]: B'"',
        B'('[0]: B')',
        B'{'[0]: B'}',
        B'['[0]: B']',
        B'<'[0]: B'>',
    }

    def _check_match(self, data: Union[memoryview, bytearray], pos: int, name: str, value: bytes):
        term = self._BRACKETING.get(data[pos - 1], None)
        if term:
            pos = value.find(term)
            if pos > 0:
                value = value[:pos]
        if not self.args.filter:
            return value
        if name == indicators.hostname.name:
            if all(part.isdigit() for part in value.split(B'.')):
                name = indicators.ipv4.name
            elif B'.' not in value:
                name = indicators.ipv6.name
            else:
                name = indicators.domain.name
        if name == indicators.ipv4.name:
            ocets = [int(x) for x in value.split(B'.')]
            if ocets.count(0) >= 3:
                return None
            if self.args.filter > 2 and sum(ocets) < 10:
                return None
            for area in (
                bytes(data[pos - 20 : pos + 20]),
                bytes(data[pos * 2 - 40 : pos * 2 + 40 : 2]),
                bytes(data[pos * 2 - 41 : pos * 2 + 39 : 2]),
            ):
                if B'version' in area.lower():
                    return None
            ip = ip_address(value.decode(self.codec))
            if not ip.is_global:
                if self.args.filter >= 3 or not ip.is_private:
                    return None
        elif name in {
            indicators.url.name,
            indicators.socket.name,
            indicators.hostname.name,
            indicators.domain.name,
            indicators.subdomain.name
        }:
            if self.args.filter >= 2:
                if LetterWeights.IOC(value) < 0.6:
                    self.log_info(value)
                    self.log_info('excluding indicator because of low IOC score')
                    return None
                if name != indicators.url.name and len(value) > 0x100:
                    self.log_info(value)
                    self.log_info('excluding indicator because it is too long')
                    return None
            ioc = value.decode(self.codec)
            if '://' not in ioc: ioc = F'tcp://{ioc}'
            parts = urlparse(ioc)
            host, _, _ = parts.netloc.partition(':')
            hl = host.lower()
            for white, level in self._LEGITIMATE_HOSTS.items():
                if self.args.filter >= level and (hl == white or hl.endswith(F'.{white}')):
                    self.log_info(value)
                    self.log_info(
                        F'excluding indicator because domain {hl} is whitelisted via {white}; '
                        F'reduce level below {level} to allow, current level is {self.args.filter}'
                    )
                    return None
            if name == indicators.url.name:
                scheme = parts.scheme.lower()
                for p in ('http', 'https', 'ftp', 'file', 'mailto'):
                    if scheme.endswith(p):
                        pos = scheme.find(p)
                        value = value[pos:]
                        break
            if any(hl == w for w in self._DOMAIN_WHITELIST):
                self.log_info(value)
                self.log_info(F'excluding indicator because domain {hl} is whitelisted')
                return None
            if name in {
                indicators.hostname.name,
                indicators.domain.name,
                indicators.subdomain.name
            }:
                if data[pos - 1] in b'/\\' and self.args.filter >= 2:
                    return None
                hostparts = host.split('.')
                if self.args.filter >= 2:
                    if not all(p.isdigit() for p in hostparts) and all(len(p) < 4 for p in hostparts):
                        self.log_info(value)
                        self.log_info('excluding host with too many short parts')
                        return None
                if self.args.filter >= 3:
                    if len(hostparts) <= sum(3 for p in hostparts if p != p.lower() and p != p.upper()):
                        self.log_info(value)
                        self.log_info('excluding host with too many mixed case parts')
                        return None
                # These heuristics attempt to filter out member access to variables in
                # scripts which can be mistaken for domains because of the TLD inflation
                # we've had.
                uppercase = sum(1 for c in host if c.isalpha() and c.upper() == c)
                lowercase = sum(1 for c in host if c.isalpha() and c.lower() == c)
                if lowercase and uppercase:
                    caseratio = uppercase / lowercase
                    if 0.1 < caseratio < 0.9:
                        self.log_info(value)
                        self.log_info('excluding indicator with too much uppercase letters')
                        return None
                if all(x.isidentifier() for x in hostparts):
                    if len(hostparts) == 2 and hostparts[0] in ('this', 'self'):
                        self.log_info(value)
                        self.log_info('excluding host that looks like a code snippet')
                        return None
                    if len(hostparts[-2]) < 3:
                        self.log_info(value)
                        self.log_info('excluding host with too short root domain name')
                        return None
                    if any(x.startswith('_') for x in hostparts):
                        self.log_info(value)
                        self.log_info('excluding host with underscores')
                        return None
                    if len(hostparts[-1]) > 3:
                        prefix = '.'.join(hostparts[:-1])
                        seen_before = len(set(re.findall(
                            R'{}(?:\.\w+)+'.format(prefix).encode('ascii'), data)))
                        if seen_before > 2:
                            self.log_debug(value)
                            self.log_debug('excluding indicator that was already seen')
                            return None
        elif name == indicators.email.name:
            at = value.find(B'@')
            ix = 0
            while value[ix] not in self._ALPHABETIC:
                ix += 1
            return None if at - ix < 3 else value[ix:]
        elif name in (
            indicators.path.name,
            indicators.winpath.name,
            indicators.nixpath.name,
        ):
            if len(value) < 8:
                return None
            if len(value) > 16 and len(re.findall(RB'\\x\d\d', value)) > len(value) // 10:
                return None
            try:
                path_string = value.decode(self.codec)
            except Exception:
                return None
            try:
                path = Path(path_string)
            except Exception as E:
                self.log_debug(F'error parsing path "{path}": {E!s}')
                return None
            path_likeness = sum(v for v, x in [
                (1, path.suffix),
                (1, path_string.startswith('/')),
                (2, path_string.startswith('%')),
                (2, path_string.startswith('\\\\')),
                (2, path_string[1:3] == ':\\'),
            ] if x)
            if path_likeness < min(self.args.filter, 2):
                return None
            if self.args.filter >= 2:
                for k, part in enumerate(path.parts):
                    if not k:
                        drive, colon, slash = part.partition(':')
                        if colon and len(drive) == 1 and len(slash) <= 1:
                            continue
                        if part[0] == part[~0] == '%':
                            continue
                    if LetterWeights.Path(part) < 0.4 + (min(self.args.filter, 5) * 0.1):
                        return None
        return value

    def process(self, data):
        whitelist = set()

        def check(match: re.Match):
            for name, value in match.groupdict().items():
                if value is not None:
                    break
            else:
                raise RefineryCriticalException('Received empty match.')
            if value in whitelist:
                return None
            result = self._check_match(match.string, match.start(), name, value)
            if result is not None:
                return self.labelled(result, pattern=name)
            whitelist.add(value)

        transforms = [check]
        yield from self.matches_filtered(memoryview(data), self.args.pattern, *transforms)

Ancestors

• PatternExtractor
• PatternExtractorBase
• Unit
• UnitBase
• Entry

Class variables

var required_dependencies

var optional_dependencies

Inherited members

• PatternExtractor:
  • Arg
  • assemble
  • filter
  • finish
  • handles
  • labelled
  • log_debug
  • log_detach
  • log_fail
  • log_info
  • log_level
  • log_warn
  • matches
  • matches_filtered
  • nozzle
  • process
  • read
  • read1
  • reverse
  • run
  • source
  • superinit