blue-team-tools/tools/sigma/backends/misc.py

# Output backends for sigmac
# Copyright 2016-2017 Thomas Patzke

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program 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 Lesser General Public License for more details.

# You should have received a copy of the GNU Lesser General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import re
from .base import BaseBackend
from .mixins import QuoteCharMixin

class GrepBackend(BaseBackend, QuoteCharMixin):
    """Generates Perl compatible regular expressions and puts 'grep -P' around it"""
    identifier = "grep"
    active = True
    config_required = False

    reEscape = re.compile("([\\|()\[\]{}.^$+])")

    def generateQuery(self, parsed):
        return "grep -P '^%s'" % self.generateNode(parsed.parsedSearch)

    def cleanValue(self, val):
        val = super().cleanValue(val)
        val = val.replace("'","'\"'\"'")
        return re.sub("\\*", ".*", val)

    def generateORNode(self, node):
        return "(?:%s)" % "|".join([".*" + self.generateNode(val) for val in node])

    def generateANDNode(self, node):
        return "".join(["(?=.*%s)" % self.generateNode(val) for val in node])

    def generateNOTNode(self, node):
        return "(?!.*%s)" % self.generateNode(node.item)

    def generateSubexpressionNode(self, node):
        return "(?:.*%s)" % self.generateNode(node.items)

    def generateListNode(self, node):
        if not set([type(value) for value in node]).issubset({str, int}):
            raise TypeError("List values must be strings or numbers")
        return self.generateORNode(node)

    def generateMapItemNode(self, node):
        key, value = node
        if value is None:
            return self.generateNULLValueNode(node)
        else:
            return self.generateNode(value)

    def generateValueNode(self, node):
        return self.cleanValue(str(node))

    def generateNULLValueNode(self, node):
        key, value = node
        return "(?!%s)" % key