From f7da091437b991fd860d1dac90af9fe111633c20 Mon Sep 17 00:00:00 2001
From: Steven Hiscocks <steven@hiscocks.me.uk>
Date: Mon, 9 Jun 2014 22:27:51 +0100
Subject: [PATCH] ENH: Log unhandled exceptions to Fail2Ban log

---
 ChangeLog                        |  1 +
 fail2ban/helpers.py              |  7 +++++++
 fail2ban/server/jailthread.py    | 13 +++++++++++++
 fail2ban/server/server.py        |  5 ++++-
 fail2ban/tests/servertestcase.py | 13 ++++++++++++-
 5 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index ff70f07cc..a77438015 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -40,6 +40,7 @@ ver. 0.9.1 (2014/xx/xx) - better, faster, stronger
    * Match non "Bye Bye" disconnect messages for sshd locked account regex
    * Realign fail2ban log output with white space to improve readability. Does
      not affect SYSLOG output.
+   * Log unhandled exceptions
 
 ver. 0.9.0 (2014/03/14) - beta
 ----------
diff --git a/fail2ban/helpers.py b/fail2ban/helpers.py
index c3e50336b..35c7ebc39 100644
--- a/fail2ban/helpers.py
+++ b/fail2ban/helpers.py
@@ -112,3 +112,10 @@ def getF2BLogger(name):
 	"""Get logging.Logger instance with Fail2Ban logger name convention
 	"""
 	return logging.getLogger("fail2ban.%s" % name.rpartition(".")[-1])
+
+def fail2ban_excepthook(exctype, value, traceback):
+	"""Except hook used to log unhandled exceptions to Fail2Ban log
+	"""
+	logging.getLogger("fail2ban").critical(
+		"Unhandled exception in Fail2Ban:", exc_info=True)
+	return sys.__excepthook__(exctype, value, traceback)
diff --git a/fail2ban/server/jailthread.py b/fail2ban/server/jailthread.py
index 7dcdb2d7e..4f640f8b4 100644
--- a/fail2ban/server/jailthread.py
+++ b/fail2ban/server/jailthread.py
@@ -24,9 +24,12 @@ __author__ = "Cyril Jaquier"
 __copyright__ = "Copyright (c) 2004 Cyril Jaquier"
 __license__ = "GPL"
 
+import sys
 from threading import Thread
 from abc import abstractproperty, abstractmethod
 
+from ..helpers import fail2ban_excepthook
+
 class JailThread(Thread):
 	"""Abstract class for threading elements in Fail2Ban.
 
@@ -53,6 +56,16 @@ class JailThread(Thread):
 		## The time the thread sleeps in the loop.
 		self.sleeptime = 1
 
+		# excepthook workaround for threads, derived from:
+		# http://bugs.python.org/issue1230540#msg91244
+		run = self.run
+		def run_with_except_hook(*args, **kwargs):
+			try:
+				run(*args, **kwargs)
+			except:
+				fail2ban_excepthook(*sys.exc_info())
+		self.run = run_with_except_hook
+
 	@abstractproperty
 	def status(self): # pragma: no cover - abstract
 		"""Abstract - Should provide status information.
diff --git a/fail2ban/server/server.py b/fail2ban/server/server.py
index 2f227517c..a6be18ac6 100644
--- a/fail2ban/server/server.py
+++ b/fail2ban/server/server.py
@@ -32,7 +32,7 @@ from .filter import FileFilter, JournalFilter
 from .transmitter import Transmitter
 from .asyncserver import AsyncServer, AsyncServerException
 from .. import version
-from ..helpers import getF2BLogger
+from ..helpers import getF2BLogger, fail2ban_excepthook
 
 # Gets the instance of the logger.
 logSys = getF2BLogger(__name__)
@@ -70,6 +70,9 @@ class Server:
 		signal.signal(signal.SIGTERM, self.__sigTERMhandler)
 		signal.signal(signal.SIGINT, self.__sigTERMhandler)
 		
+		# Ensure unhandled exceptions are logged
+		sys.excepthook = fail2ban_excepthook
+
 		# First set the mask to only allow access to owner
 		os.umask(0077)
 		if self.__daemon: # pragma: no cover
diff --git a/fail2ban/tests/servertestcase.py b/fail2ban/tests/servertestcase.py
index 1dfe13ca3..6ce6e54fd 100644
--- a/fail2ban/tests/servertestcase.py
+++ b/fail2ban/tests/servertestcase.py
@@ -35,6 +35,8 @@ import logging
 from ..server.failregex import Regex, FailRegex, RegexException
 from ..server.server import Server
 from ..server.jail import Jail
+from ..server.jailthread import JailThread
+from .utils import LogCaptureTestCase
 from ..helpers import getF2BLogger
 
 try:
@@ -797,10 +799,19 @@ class RegexTests(unittest.TestCase):
 		self.assertTrue(fr.hasMatched())
 		self.assertRaises(RegexException, fr.getHost)
 
-class LoggingTests(unittest.TestCase):
+class _BadThread(JailThread):
+	def run(self):
+		int("cat")
+
+class LoggingTests(LogCaptureTestCase):
 
 	def testGetF2BLogger(self):
 		testLogSys = getF2BLogger("fail2ban.some.string.with.name")
 		self.assertEqual(testLogSys.parent.name, "fail2ban")
 		self.assertEqual(testLogSys.name, "fail2ban.name")
 
+	def testFail2BanExceptHook(self):
+		badThread = _BadThread()
+		badThread.start()
+		badThread.join()
+		self.assertTrue(self._is_logged("Unhandled exception"))