Thomas Patzke
213 lines
9.4 KiB
Python
213 lines
9.4 KiB
Python
# Output backends for sigmac
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# Copyright 2016-2018 Thomas Patzke, Florian Roth, Roey
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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# You should have received a copy of the GNU Lesser General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import re
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import sigma
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from .base import SingleTextQueryBackend
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from .mixins import MultiRuleOutputMixin
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class SplunkBackend(SingleTextQueryBackend):
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"""Converts Sigma rule into Splunk Search Processing Language (SPL)."""
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identifier = "splunk"
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active = True
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index_field = "index"
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# \ -> \\
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# \* -> \*
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# \\* -> \\*
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reEscape = re.compile('("|(?<!\\\\)\\\\(?![*?\\\\]))')
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reClear = None
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andToken = " "
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orToken = " OR "
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notToken = "NOT "
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subExpression = "(%s)"
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listExpression = "(%s)"
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listSeparator = " "
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valueExpression = "\"%s\""
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nullExpression = "NOT %s=\"*\""
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notNullExpression = "%s=\"*\""
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mapExpression = "%s=%s"
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mapListsSpecialHandling = True
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mapListValueExpression = "%s IN %s"
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def generateMapItemListNode(self, key, value):
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if not set([type(val) for val in value]).issubset({str, int}):
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raise TypeError("List values must be strings or numbers")
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return "(" + (" OR ".join(['%s=%s' % (key, self.generateValueNode(item)) for item in value])) + ")"
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def generateAggregation(self, agg):
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if agg == None:
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return ""
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if agg.aggfunc == sigma.parser.condition.SigmaAggregationParser.AGGFUNC_NEAR:
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raise NotImplementedError("The 'near' aggregation operator is not yet implemented for this backend")
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if agg.groupfield == None:
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if agg.aggfunc_notrans == 'count':
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if agg.aggfield == None :
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return " | eventstats count as val | search val %s %s" % (agg.cond_op, agg.condition)
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else:
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agg.aggfunc_notrans = 'dc'
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return " | eventstats %s(%s) as val | search val %s %s" % (agg.aggfunc_notrans, agg.aggfield or "", agg.cond_op, agg.condition)
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else:
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if agg.aggfunc_notrans == 'count':
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if agg.aggfield == None :
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return " | eventstats count as val by %s| search val %s %s" % (agg.groupfield, agg.cond_op, agg.condition)
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else:
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agg.aggfunc_notrans = 'dc'
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return " | eventstats %s(%s) as val by %s | search val %s %s" % (agg.aggfunc_notrans, agg.aggfield or "", agg.groupfield or "", agg.cond_op, agg.condition)
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def generate(self, sigmaparser):
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"""Method is called for each sigma rule and receives the parsed rule (SigmaParser)"""
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columns = list()
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mapped =None
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try:
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for field in sigmaparser.parsedyaml["fields"]:
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mapped = sigmaparser.config.get_fieldmapping(field).resolve_fieldname(field, sigmaparser)
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if type(mapped) == str:
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columns.append(mapped)
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elif type(mapped) == list:
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columns.extend(mapped)
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else:
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raise TypeError("Field mapping must return string or list")
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fields = ",".join(str(x) for x in columns)
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fields = " | table " + fields
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except KeyError: # no 'fields' attribute
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mapped = None
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pass
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for parsed in sigmaparser.condparsed:
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query = self.generateQuery(parsed)
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before = self.generateBefore(parsed)
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after = self.generateAfter(parsed)
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result = ""
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if before is not None:
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result = before
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if query is not None:
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result += query
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if after is not None:
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result += after
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if mapped is not None:
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result += fields
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return result
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class SplunkXMLBackend(SingleTextQueryBackend, MultiRuleOutputMixin):
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"""Converts Sigma rule into XML used for Splunk Dashboard Panels"""
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identifier = "splunkxml"
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active = True
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index_field = "index"
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panel_pre = "<row><panel><title>"
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panel_inf = "</title><table><search><query>"
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panel_suf = "</query><earliest>$field1.earliest$</earliest><latest>$field1.latest$</latest><sampleRatio>1</sampleRatio>" \
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"</search><option name=\"count\">20</option><option name=\"dataOverlayMode\">none</option><option name=\"" \
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"drilldown\">row</option><option name=\"percentagesRow\">false</option><option name=\"refresh.display\">" \
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"progressbar</option><option name=\"rowNumbers\">false</option><option name=\"totalsRow\">false</option>" \
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"<option name=\"wrap\">true</option></table></panel></row>"
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dash_pre = "<form><label>MyDashboard</label><fieldset submitButton=\"false\"><input type=\"time\" token=\"field1\">" \
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"<label></label><default><earliest>-24h@h</earliest><latest>now</latest></default></input></fieldset>"
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dash_suf = "</form>"
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queries = dash_pre
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reEscape = re.compile('("|(?<!\\\\)\\\\(?![*?\\\\]))')
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reClear = SplunkBackend.reClear
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andToken = SplunkBackend.andToken
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orToken = SplunkBackend.orToken
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notToken = SplunkBackend.notToken
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subExpression = SplunkBackend.subExpression
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listExpression = SplunkBackend.listExpression
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listSeparator = SplunkBackend.listSeparator
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valueExpression = SplunkBackend.valueExpression
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nullExpression = SplunkBackend.nullExpression
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notNullExpression = SplunkBackend.notNullExpression
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mapExpression = SplunkBackend.mapExpression
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mapListsSpecialHandling = SplunkBackend.mapListsSpecialHandling
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mapListValueExpression = SplunkBackend.mapListValueExpression
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def generateMapItemListNode(self, key, value):
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return "(" + (" OR ".join(['%s=%s' % (key, self.generateValueNode(item)) for item in value])) + ")"
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def generateAggregation(self, agg):
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if agg == None:
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return ""
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if agg.aggfunc == sigma.parser.condition.SigmaAggregationParser.AGGFUNC_NEAR:
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return ""
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if agg.groupfield == None:
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return " | stats %s(%s) as val | search val %s %s" % (agg.aggfunc_notrans, agg.aggfield or "", agg.cond_op, agg.condition)
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else:
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return " | stats %s(%s) as val by %s | search val %s %s" % (agg.aggfunc_notrans, agg.aggfield or "", agg.groupfield or "", agg.cond_op, agg.condition)
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def generate(self, sigmaparser):
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"""Method is called for each sigma rule and receives the parsed rule (SigmaParser)"""
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for parsed in sigmaparser.condparsed:
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query = self.generateQuery(parsed)
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if query is not None:
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self.queries += self.panel_pre
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self.queries += sigmaparser.parsedyaml.get("title") or ""
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self.queries += self.panel_inf
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query = query.replace("<", "<")
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query = query.replace(">", ">")
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self.queries += query
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self.queries += self.panel_suf
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def finalize(self):
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self.queries += self.dash_suf
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return self.queries
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class CrowdStrikeBackend(SplunkBackend):
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"""Converts Sigma rule into CrowdStrike Search Processing Language (SPL)."""
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identifier = "crowdstrike"
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def generate(self, sigmaparser):
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lgs = sigmaparser.parsedyaml.get("logsource")
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if lgs.get("product") == "windows" and (lgs.get("service") == "sysmon" or lgs.get("category") == "process_creation"):
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fieldmappings = sigmaparser.config.fieldmappings
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detections = sigmaparser.definitions
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all_fields = dict()
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for det in detections.values():
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try:
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for field, value in det.items():
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if "|" in field:
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field = field.split("|")[0]
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if any([item for item in fieldmappings.keys() if field == item]):
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if field == "EventID" and str(value) == str(1) and lgs.get("service") == "sysmon":
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all_fields.update(det)
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elif field != "EventID":
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all_fields.update(det)
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else:
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raise NotImplementedError("Not supported fields!")
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else:
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raise NotImplementedError("Not supported fields!")
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except AttributeError: # ignore if detection is not a dict
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pass
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table_fields = sigmaparser.parsedyaml.get("fields", [])
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res_table_fields = []
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for fl in table_fields:
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if fl in fieldmappings.keys():
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res_table_fields.append(fl)
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sigmaparser.parsedyaml["fields"] = res_table_fields
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return super().generate(sigmaparser)
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else:
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raise NotImplementedError("Not supported logsources!")
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def generateMapItemTypedNode(self, fieldname, value):
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return super().generateMapItemTypedNode(fieldname=fieldname, value=value) |