failregex.py

# emacs: -*- mode: python; py-indent-offset: 4; indent-tabs-mode: t -*-
# vi: set ft=python sts=4 ts=4 sw=4 noet :

# This file is part of Fail2Ban.
#
# Fail2Ban is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# Fail2Ban is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Fail2Ban; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

__author__ = "Cyril Jaquier"
__copyright__ = "Copyright (c) 2004 Cyril Jaquier"
__license__ = "GPL"

import re
import sre_constants
import sys

from .ipdns import IPAddr

##
# Regular expression class.
#
# This class represents a regular expression with its compiled version.

class Regex:

	##
	# Constructor.
	#
	# Creates a new object. This method can throw RegexException in order to
	# avoid construction of invalid object.
	# @param value the regular expression
	
	def __init__(self, regex, **kwargs):
		self._matchCache = None
		# Perform shortcuts expansions.
		# Resolve "<HOST>" tag using default regular expression for host:
		regex = Regex._resolveHostTag(regex, **kwargs)
		# Replace "<SKIPLINES>" with regular expression for multiple lines.
		regexSplit = regex.split("<SKIPLINES>")
		regex = regexSplit[0]
		for n, regexLine in enumerate(regexSplit[1:]):
			regex += "\n(?P<skiplines%i>(?:(.*\n)*?))" % n + regexLine
		if regex.lstrip() == '':
			raise RegexException("Cannot add empty regex")
		try:
			self._regexObj = re.compile(regex, re.MULTILINE)
			self._regex = regex
		except sre_constants.error:
			raise RegexException("Unable to compile regular expression '%s'" %
								 regex)

	def __str__(self):
		return "%s(%r)" % (self.__class__.__name__, self._regex)

	##
	# Replaces "<HOST>", "<IP4>", "<IP6>", "<FID>" with default regular expression for host
	#
	# (see gh-1374 for the discussion about other candidates)
	# @return the replaced regular expression as string

	@staticmethod
	def _resolveHostTag(regex, useDns="yes"):
		# separated ipv4:
		r_host = []
		r = r"""(?:::f{4,6}:)?(?P<ip4>%s)""" % (IPAddr.IP_4_RE,)
		regex = regex.replace("<IP4>", r); # self closed
		regex = regex.replace("<F-IP4/>", r); # closed
		r_host.append(r)
		# separated ipv6:
		r = r"""(?P<ip6>%s)""" % (IPAddr.IP_6_RE,)
		regex = regex.replace("<IP6>", r); # self closed
		regex = regex.replace("<F-IP6/>", r); # closed
		r_host.append(r"""\[?%s\]?""" % (r,)); # enclose ipv6 in optional [] in host-regex
		# 2 address groups instead of <ADDR> - in opposition to `<HOST>`, 
		# for separate usage of 2 address groups only (regardless of `usedns`), `ip4` and `ip6` together
		regex = regex.replace("<ADDR>", "(?:%s)" % ("|".join(r_host),))
		# separated dns:
		r = r"""(?P<dns>[\w\-.^_]*\w)"""
		regex = regex.replace("<DNS>", r); # self closed
		regex = regex.replace("<F-DNS/>", r); # closed
		if useDns not in ("no",):
			r_host.append(r)
		# 3 groups instead of <HOST> - separated ipv4, ipv6 and host (dns)
		regex = regex.replace("<HOST>", "(?:%s)" % ("|".join(r_host),))
		# default failure-id as no space tag:
		regex = regex.replace("<F-ID/>", r"""(?P<fid>\S+)"""); # closed
		# default failure port, like 80 or http :
		regex = regex.replace("<F-PORT/>", r"""(?P<port>\w+)"""); # closed
		# default failure groups (begin / end tag) for customizable expressions:
		for o,r in (('IP4', 'ip4'), ('IP6', 'ip6'), ('DNS', 'dns'), ('ID', 'fid'), ('PORT', 'fport')):
			regex = regex.replace("<F-%s>" % o, "(?P<%s>" % r); # open tag
			regex = regex.replace("</F-%s>" % o, ")"); # close tag

		return regex

	##
	# Gets the regular expression.
	#
	# The effective regular expression used is returned.
	# @return the regular expression
	
	def getRegex(self):
		return self._regex
	
	##
	# Searches the regular expression.
	#
	# Sets an internal cache (match object) in order to avoid searching for
	# the pattern again. This method must be called before calling any other
	# method of this object.
	# @param a list of tupples. The tupples are ( prematch, datematch, postdatematch )
	
	def search(self, tupleLines):
		self._matchCache = self._regexObj.search(
			"\n".join("".join(value[::2]) for value in tupleLines) + "\n")
		if self.hasMatched():
			# Find start of the first line where the match was found
			try:
				self._matchLineStart = self._matchCache.string.rindex(
					"\n", 0, self._matchCache.start() +1 ) + 1
			except ValueError:
				self._matchLineStart = 0
			# Find end of the last line where the match was found
			try:
				self._matchLineEnd = self._matchCache.string.index(
					"\n", self._matchCache.end() - 1) + 1
			except ValueError:
				self._matchLineEnd = len(self._matchCache.string)

			lineCount1 = self._matchCache.string.count(
				"\n", 0, self._matchLineStart)
			lineCount2 = self._matchCache.string.count(
				"\n", 0, self._matchLineEnd)
			self._matchedTupleLines = tupleLines[lineCount1:lineCount2]
			self._unmatchedTupleLines = tupleLines[:lineCount1]

			n = 0
			for skippedLine in self.getSkippedLines():
				for m, matchedTupleLine in enumerate(
					self._matchedTupleLines[n:]):
					if "".join(matchedTupleLine[::2]) == skippedLine:
						self._unmatchedTupleLines.append(
							self._matchedTupleLines.pop(n+m))
						n += m
						break
			self._unmatchedTupleLines.extend(tupleLines[lineCount2:])

	# Checks if the previous call to search() matched.
	#
	# @return True if a match was found, False otherwise
	
	def hasMatched(self):
		if self._matchCache:
			return True
		else:
			return False

	##
	# Returns skipped lines.
	#
	# This returns skipped lines captured by the <SKIPLINES> tag.
	# @return list of skipped lines
	
	def getSkippedLines(self):
		if not self._matchCache:
			return []
		skippedLines = ""
		n = 0
		while True:
			try:
				if self._matchCache.group("skiplines%i" % n) is not None:
					skippedLines += self._matchCache.group("skiplines%i" % n)
				n += 1
			except IndexError:
				break
			# KeyError is because of PyPy issue1665 affecting pypy <= 2.2.1 
			except KeyError:
				if 'PyPy' not in sys.version: # pragma: no cover - not sure this is even reachable
					raise
				break
		return skippedLines.splitlines(False)

	##
	# Returns unmatched lines.
	#
	# This returns unmatched lines including captured by the <SKIPLINES> tag.
	# @return list of unmatched lines

	def getUnmatchedTupleLines(self):
		if not self.hasMatched():
			return []
		else:
			return self._unmatchedTupleLines

	def getUnmatchedLines(self):
		if not self.hasMatched():
			return []
		else:
			return ["".join(line) for line in self._unmatchedTupleLines]

	##
	# Returns matched lines.
	#
	# This returns matched lines by excluding those captured
	# by the <SKIPLINES> tag.
	# @return list of matched lines

	def getMatchedTupleLines(self):
		if not self.hasMatched():
			return []
		else:
			return self._matchedTupleLines

	def getMatchedLines(self):
		if not self.hasMatched():
			return []
		else:
			return ["".join(line) for line in self._matchedTupleLines]


##
# Exception dedicated to the class Regex.

class RegexException(Exception):
	pass


##
# Groups used as failure identifier.
#
# The order of this tuple is important while searching for failure-id
#
FAILURE_ID_GROPS = ("fid", "ip4", "ip6", "dns")

##
# Regular expression class.
#
# This class represents a regular expression with its compiled version.

class FailRegex(Regex):

	##
	# Constructor.
	#
	# Creates a new object. This method can throw RegexException in order to
	# avoid construction of invalid object.
	# @param value the regular expression

	def __init__(self, regex, **kwargs):
		# Initializes the parent.
		Regex.__init__(self, regex, **kwargs)
		# Check for group "dns", "ip4", "ip6", "fid"
		if not [grp for grp in FAILURE_ID_GROPS if grp in self._regexObj.groupindex]:
			raise RegexException("No failure-id group in '%s'" % self._regex)
	
	##
	# Returns all matched groups.
	#

	def getGroups(self):
		return self._matchCache.groupdict()

	##
	# Returns the matched failure id.
	#
	# This corresponds to the pattern matched by the named group from given groups.
	# @return the matched failure-id
	
	def getFailID(self, groups=FAILURE_ID_GROPS):
		fid = None
		for grp in groups:
			try:
				fid = self._matchCache.group(grp)
			except (IndexError, KeyError):
				continue
			if fid is not None:
				break
		if fid is None:
			# Gets a few information.
			s = self._matchCache.string
			r = self._matchCache.re
			raise RegexException("No group found in '%s' using '%s'" % (s, r))
		return str(fid)

	##
	# Returns the matched host.
	#
	# This corresponds to the pattern matched by the named group "ip4", "ip6" or "dns".
	# @return the matched host
	
	def getHost(self):
		return self.getFailID(("ip4", "ip6", "dns"))