Implement support for systemd-based distributions

.gitignore

@@ -2,3 +2,4 @@
 .idea
 MANIFEST
 dist
+venv/

knockknock-daemon.py

@@ -24,9 +24,6 @@
 """
 
 import os, sys, pwd, grp
-
-from knockknock.LogEntry import LogEntry
-from knockknock.LogFile import LogFile
 from knockknock.Profiles import Profiles
 from knockknock.PortOpener import PortOpener
 from knockknock.DaemonConfiguration import DaemonConfiguration
@@ -48,6 +45,25 @@ def checkConfiguration():
         print "/etc/knockknock.d/profiles/ does not exist.  You need to setup your profiles first..."
         sys.exit(3)
 
+    # Retreive the system init type from /proc
+    with open('/proc/1/status', 'r') as f:
+        global initprocname
+        initprocname = f.readline().split()[1]
+
+    # Verify whether or not the python-systemd dependency is required as well
+    # as whether or not it is fulfilled (optimistically written with python3
+    # support)
+    if (sys.version_info > (3, 0)):
+        import importlib
+        if initprocname == "systemd" and importlib.util.find_spec("systemd") is None:
+            print "Your init system was detected as systemd but the python systemd module is not installed. You need to install it first..."
+            sys.exit(3)
+    else:
+        import pkgutil
+        if initprocname == "systemd" and pkgutil.find_loader("systemd") is None:
+            print "Your init system was detected as systemd but the python systemd module is not installed. You need to install it first..."
+            sys.exit(3)
+
 def dropPrivileges():
     nobody = pwd.getpwnam('nobody')
     adm    = grp.getgrnam('adm')
@@ -62,10 +78,20 @@ def handleFirewall(input, config):
 
 def handleKnocks(output, profiles, config):
     dropPrivileges()
-
-    logFile      = LogFile('/var/log/kern.log')
+    # Attempt to determine logging source here (since it shouldn't require
+    # elevated privileges to verify this information) based on the system
+    # init process
+    if initprocname == "systemd":
+        from knockknock.LogJournald import JournalReader
+        logSource      = JournalReader()
+    elif initprocname in ["init", "preinit"]:
+        from knockknock.LogFile import LogFile
+        logSource      = LogFile('/var/log/kern.log')
+    else:
+        print "Failed to find logging source for your init system. Exiting"
+        sys.exit(3)
     portOpener   = PortOpener(output, config.getDelay())
-    knockWatcher = KnockWatcher(config, logFile, profiles, portOpener)
+    knockWatcher = KnockWatcher(config, logSource, profiles, portOpener)
 
     knockWatcher.tailAndProcess()
 
@@ -90,6 +116,6 @@ def main(argv):
     else:
         os.close(output)
         handleFirewall(os.fdopen(input, 'r'), config)
-                
+
 if __name__ == '__main__':
     main(sys.argv[1:])

knockknock/LogJournald.py

@@ -0,0 +1,54 @@
+"""
+Journald log reader event loop for knockknock-daemon.
+
+Contains the JournalReader class which takes no parameters and has 1 method:
+(tail)
+"""
+# Copyright (c) 2015 Jason Ritzke
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+# USA
+#
+
+import select
+import time
+from systemd import journal
+
+
+class JournalReader:
+    """
+    Journald reader for knockknock-daemon.
+
+    Takes no parameters on initialization. Has a single event loop method
+    called tail that yields new messages in the kernel log.
+    """
+
+    def __init__(self):
+        """Initalization method for JournalReader class."""
+        self.j = journal.Reader()
+        self.j.seek_tail()
+        self.j.add_match('_TRANSPORT=kernel')
+        self.p = select.poll()
+        self.p.register(self.j, self.j.get_events())
+
+    def tail(self):
+        """Generator that yields messages from the kernel log."""
+        while True:
+            self.p.poll()
+            line = self.j.get_next()
+            if 'MESSAGE' not in line:
+                time.sleep(.25)
+            else:
+                yield line['MESSAGE']