add: Sigma syntax validator expansion module

--> Checks sigma rules syntax
- Updated the expansion modules list as well
- Updated the requirements list

REQUIREMENTS

@@ -20,3 +20,4 @@ pygeoip
 bs4
 oauth2
 yara
+sigmatools

misp_modules/modules/expansion/__init__.py

@@ -1,3 +1,3 @@
 from . import _vmray
 
-__all__ = ['vmray_submit', 'asn_history', 'circl_passivedns', 'circl_passivessl', 'countrycode', 'cve', 'dns', 'domaintools', 'eupi', 'farsight_passivedns', 'ipasn', 'passivetotal', 'sourcecache', 'virustotal', 'whois', 'shodan', 'reversedns', 'geoip_country', 'wiki', 'iprep', 'threatminer', 'otx', 'threatcrowd', 'vulndb', 'crowdstrike_falcon', 'yara_syntax_validator', 'hashdd', 'onyphe', 'onyphe_full', 'rbl', 'xforceexchange']
+__all__ = ['vmray_submit', 'asn_history', 'circl_passivedns', 'circl_passivessl', 'countrycode', 'cve', 'dns', 'domaintools', 'eupi', 'farsight_passivedns', 'ipasn', 'passivetotal', 'sourcecache', 'virustotal', 'whois', 'shodan', 'reversedns', 'geoip_country', 'wiki', 'iprep', 'threatminer', 'otx', 'threatcrowd', 'vulndb', 'crowdstrike_falcon', 'yara_syntax_validator', 'hashdd', 'onyphe', 'onyphe_full', 'rbl', 'xforceexchange', 'sigma_syntax_validator']

misp_modules/modules/expansion/sigma_syntax_validator.py

@@ -0,0 +1,35 @@
+import json
+try:
+    import yaml
+    from sigma.parser import SigmaParser
+    from sigma.config import SigmaConfiguration
+except ModuleNotFoundError:
+    print("sigma or yaml is missing, use 'pip3 install sigmatools' to install it.")
+
+misperrors = {'error': 'Error'}
+mispattributes = {'input': ['sigma'], 'output': ['text']}
+moduleinfo = {'version': '0.1', 'author': 'Christian Studer', 'module-type': ['expansion', 'hover'],
+              'description': 'An expansion hover module to perform a syntax check on sigma rules'}
+moduleconfig = []
+
+def handler(q=False):
+    if q is False:
+        return False
+    request = json.loads(q)
+    if not request.get('sigma'):
+        misperrors['error'] = 'Sigma rule missing'
+        return misperrors
+    config = SigmaConfiguration()
+    try:
+        parser = SigmaParser(yaml.load(request.get('sigma')), config)
+        result = ("Syntax valid: {}".format(parser.values))
+    except Exception as e:
+        result = ("Syntax error: {}".format(str(e)))
+    return {'results': [{'types': mispattributes['output'], 'values': result}]}
+
+def introspection():
+    return mispattributes
+
+def version():
+    moduleinfo['config'] = moduleconfig
+    return moduleinfo