event-handler: T3083: Extended event-handler features

* Added the ability to filter by a syslog identifier
* Added the ability to pass arguments to a script
* Added the ability to pass preconfigured environment variables to a script
* A message that triggered a script is now passed in the `message` variable and
can be used in a script
* Replaced `call()` to `run()`, since stdout are not need to be printed

3 files changed, 100 insertions, 41 deletions

diff --git a/interface-definitions/service-event-handler.xml.in b/interface-definitions/service-event-handler.xml.in
index 3e96013c7..ed6d41d1b 100644
--- a/interface-definitions/service-event-handler.xml.in
+++ b/interface-definitions/service-event-handler.xml.in
@@ -7,11 +7,23 @@
           <help>Event handler name</help>
         </properties>
         <children>
-          <leafNode name="pattern">
+          <node name="filter">
             <properties>
-              <help>Match pattern (regex)</help>
+              <help>Logs filter settings</help>
             </properties>
-          </leafNode>
+            <children>
+              <leafNode name="pattern">
+                <properties>
+                  <help>Match pattern (regex)</help>
+                </properties>
+              </leafNode>
+              <leafNode name="syslog-identifier">
+                <properties>
+                  <help>Identifier of a process in syslog (string)</help>
+                </properties>
+              </leafNode>
+            </children>
+          </node>
           <node name="script">
             <properties>
               <help>Event handler script file</help>
diff --git a/src/conf_mode/service_event_handler.py b/src/conf_mode/service_event_handler.py
index cf4aba49b..bb12da11d 100755
--- a/src/conf_mode/service_event_handler.py
+++ b/src/conf_mode/service_event_handler.py
@@ -18,7 +18,7 @@ import json
 from pathlib import Path
 
 from vyos.config import Config
-from vyos.util import call
+from vyos.util import call, dict_search
 from vyos import ConfigError
 from vyos import airbag
 
@@ -48,9 +48,16 @@ def verify(config):
         return None
 
     for name, event_config in config.items():
-        if 'pattern' not in event_config or 'script' not in event_config:
+        if not dict_search('filter.pattern', event_config) or not dict_search(
+                'script.path', event_config):
             raise ConfigError(
-                'Event-handler: both pattern and script items are mandatory!')
+                'Event-handler: both pattern and script path items are mandatory'
+            )
+
+        if dict_search('script.environment.message', event_config):
+            raise ConfigError(
+                'Event-handler: "message" environment variable is reserved for log message text'
+            )
 
 
 def generate(config):
diff --git a/src/system/vyos-event-handler.py b/src/system/vyos-event-handler.py
index f4b793dbe..691f674b2 100755
--- a/src/system/vyos-event-handler.py
+++ b/src/system/vyos-event-handler.py
@@ -18,12 +18,12 @@ import argparse
 import select
 import re
 import json
-from os import getpid
+from os import getpid, environ
 from pathlib import Path
 from signal import signal, SIGTERM, SIGINT
 from systemd import journal
 from sys import exit
-from vyos.util import call
+from vyos.util import run, dict_search
 
 # Identify this script
 my_pid = getpid()
@@ -41,25 +41,72 @@ def handle_signal(signal_type, frame):
     exit(0)
 
 
-# Execute script safely
-def script_run(pattern: str, script_path: str) -> None:
-    try:
-        call(script_path)
-        journal.send(
-            f'Pattern found: "{pattern}", script executed: "{script_path}"',
-            SYSLOG_IDENTIFIER=my_name)
-    except Exception as err:
-        journal.send(
-            f'Pattern found: "{pattern}", failed to execute script "{script_path}": {err}',
-            SYSLOG_IDENTIFIER=my_name)
-
-
-# iterate trough regexp items
-def analyze_message(message: str, regex_patterns: dict) -> None:
-    for pattern_compiled, pattern_config in regex_patterns.items():
-        if pattern_compiled.match(message):
-            script_run(pattern_config['pattern_raw'],
-                       pattern_config['pattern_script'])
+# Class for analyzing and process messages
+class Analyzer:
+    # Initialize settings
+    def __init__(self, config: dict) -> None:
+        self.config = {}
+        # Prepare compiled regex objects
+        for event_id, event_config in config.items():
+            script = dict_search('script.path', event_config)
+            # Check for arguments
+            if dict_search('script.arguments', event_config):
+                script_arguments = dict_search('script.arguments', event_config)
+                script = f'{script} {script_arguments}'
+            # Prepare environment
+            environment = environ
+            # Check for additional environment options
+            if dict_search('script.environment', event_config):
+                for env_variable, env_value in dict_search(
+                        'script.environment', event_config).items():
+                    environment[env_variable] = env_value.get('value')
+            # Create final config dictionary
+            pattern_raw = event_config['filter']['pattern']
+            pattern_compiled = re.compile(
+                rf'{event_config["filter"]["pattern"]}')
+            pattern_config = {
+                pattern_compiled: {
+                    'pattern_raw':
+                        pattern_raw,
+                    'syslog_id':
+                        dict_search('filter.syslog_identifier', event_config),
+                    'pattern_script': {
+                        'path': script,
+                        'environment': environment
+                    }
+                }
+            }
+            self.config.update(pattern_config)
+
+    # Execute script safely
+    def script_run(self, pattern: str, script_path: str,
+                   script_env: dict) -> None:
+        try:
+            run(script_path, env=script_env)
+            journal.send(
+                f'Pattern found: "{pattern}", script executed: "{script_path}"',
+                SYSLOG_IDENTIFIER=my_name)
+        except Exception as err:
+            journal.send(
+                f'Pattern found: "{pattern}", failed to execute script "{script_path}": {err}',
+                SYSLOG_IDENTIFIER=my_name)
+
+    # Analyze a message
+    def process_message(self, message: dict) -> None:
+        for pattern_compiled, pattern_config in self.config.items():
+            # Check if syslog id is presented in config and matches
+            syslog_id = pattern_config.get('syslog_id')
+            if syslog_id and message['SYSLOG_IDENTIFIER'] != syslog_id:
+                continue
+            if pattern_compiled.fullmatch(message['MESSAGE']):
+                # Add message to environment variables
+                pattern_config['pattern_script']['environment'][
+                    'message'] = message['MESSAGE']
+                # Run script
+                self.script_run(
+                    pattern=pattern_config['pattern_raw'],
+                    script_path=pattern_config['pattern_script']['path'],
+                    script_env=pattern_config['pattern_script']['environment'])
 
 
 if __name__ == '__main__':
@@ -76,6 +123,8 @@ if __name__ == '__main__':
     try:
         config_path = Path(args.config)
         config = json.loads(config_path.read_text())
+        # Create an object for analazyng messages
+        analyzer = Analyzer(config)
     except Exception as err:
         print(
             f'Configuration file "{config_path}" does not exist or malformed: {err}'
@@ -93,19 +142,6 @@ if __name__ == '__main__':
     p = select.poll()
     p.register(data, data.get_events())
 
-    # Prepare compiled regex objects
-    patterns = {}
-    for name, event_config in config.items():
-        pattern_raw = f'{event_config["pattern"]}'
-        pattern_compiled = re.compile(rf'{event_config["pattern"]}')
-        pattern_config = {
-            pattern_compiled: {
-                'pattern_raw': pattern_raw,
-                'pattern_script': event_config['script']
-            }
-        }
-        patterns.update(pattern_config)
-
     journal.send(f'Started with configuration: {config}',
                  SYSLOG_IDENTIFIER=my_name)
 
@@ -117,4 +153,8 @@ if __name__ == '__main__':
             pid = entry['_PID']
             # Skip empty messages and messages from this process
             if message and pid != my_pid:
-                analyze_message(message, patterns)
+                try:
+                    analyzer.process_message(entry)
+                except Exception as err:
+                    journal.send(f'Unable to process message: {err}',
+                                 SYSLOG_IDENTIFIER=my_name)