From 3a7160d52b720408ec899558d147e6e8a3d50994 Mon Sep 17 00:00:00 2001
From: christophetd <christophetd@hotmail.fr>
Date: Sat, 23 Feb 2019 13:20:20 +0100
Subject: [PATCH] Accept backend options from a configuration file (closes
 #213)

---
 tools/sigma/backends/base.py | 57 ++++++++++++++++++++++++++++++++----
 tools/sigmac                 |  4 ++-
 2 files changed, 54 insertions(+), 7 deletions(-)

diff --git a/tools/sigma/backends/base.py b/tools/sigma/backends/base.py
index 2b6cab3cb..0c4c32c84 100644
--- a/tools/sigma/backends/base.py
+++ b/tools/sigma/backends/base.py
@@ -14,28 +14,73 @@
 # 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 sys
+
 import sigma
+import yaml
+
 from .mixins import RulenameCommentMixin, QuoteCharMixin
 
+
 class BackendOptions(dict):
-    """Object contains all options that should be passed to the backend from command line (or other user interfaces)"""
+    """
+    Object containing all the options that should be passed to the backend.
+    
+    The options can come from command line and a YAML configuration file, and will be merged together.
+    Options from the command line take precedence.
+    """
 
-    def __init__(self, options):
+    def __init__(self, options, config_file):
+        """
+        :param options: unparsed options coming from the CLI
+        :param config_file: path to a YAML configuration file
         """
-        Receives the argparser result from the backend option paramater value list (nargs=*) and builds the dict from it. There are two option types:
 
-        * key=value: self{key} = value
-        * key: self{key} = True
+        self._load_config_file(config_file)
+        self._parse_options(options)
+
+    def _parse_options(self, options):
         """
-        if options == None:
+        Populates options from the unparsed options of the CLI
+
+        :param options: list unparsed options from the CLI.
+            Each option can have one of the following formats:
+            - "key=value": the option key:value will be passed to the backend
+            - "key": the option key:True will be passed to the backend
+        """
+
+        if options is None:
             return
+
         for option in options:
             parsed = option.split("=", 1)
             try:
                 self[parsed[0]] = parsed[1]
             except IndexError:
+                # If the option is present but doesn't map to a value, treat it as a boolean flag
                 self[parsed[0]] = True
 
+    def _load_config_file(self, path):
+        """
+        Populates options from a configuration file
+
+        :param path: Path to the configuration file
+        """
+        if path is None:
+            return
+
+        try:
+            with open(path, 'r') as config_file:
+                backend_config = yaml.safe_load(config_file.read())
+                for key in backend_config:
+                    self[key] = backend_config[key]
+        except (IOError, OSError) as e:
+            print("Failed to open backend configuration file '%s': %s" % (path, str(e)), file=sys.stderr)
+            exit(1)
+        except yaml.YAMLError as e:
+            print("Failed to parse backend configuration file '%s' as valid YAML: %s" % (path, str(e)), file=sys.stderr)
+            exit(1)
+
 ### Generic backend base classes
 class BaseBackend:
     """Base class for all backends"""
diff --git a/tools/sigmac b/tools/sigmac
index 0d8e0a02d..0bb58f824 100755
--- a/tools/sigmac
+++ b/tools/sigmac
@@ -90,6 +90,7 @@ argparser.add_argument("--target-list", "-l", action="store_true", help="List av
 argparser.add_argument("--config", "-c", help="Configuration with field name and index mapping for target environment")
 argparser.add_argument("--output", "-o", default=None, help="Output file or filename prefix if multiple files are generated")
 argparser.add_argument("--backend-option", "-O", action="append", help="Options and switches that are passed to the backend")
+argparser.add_argument("--backend-config", help="Configuration file containing options to pass to the backend")
 argparser.add_argument("--defer-abort", "-d", action="store_true", help="Don't abort on parse or conversion errors, proceed with next rule. The exit code from the last error is returned")
 argparser.add_argument("--ignore-backend-errors", "-I", action="store_true", help="Only return error codes for parse errors and ignore errors for rules that cause backend errors. Useful, when you want to get as much queries as possible.")
 argparser.add_argument("--verbose", "-v", action="store_true", help="Be verbose")
@@ -133,7 +134,8 @@ if cmdargs.config:
         print("Sigma configuration parse error in %s: %s" % (conffile, str(e)), file=sys.stderr)
         exit(7)
 
-backend_options = BackendOptions(cmdargs.backend_option)
+ 
+backend_options = BackendOptions(cmdargs.backend_option, cmdargs.backend_config)
 backend = backends.getBackend(cmdargs.target)(sigmaconfig, backend_options)
 filename = cmdargs.output
 if filename: