Init script for the Rascal's autossh daemon

rascal-autossh.conf

# command looks like:
#   ssh -R *:8080:localhost:8080 [email protected] -N &
#

[autossh_tunnel]
enabled = 1
ssh_keys = /home/root/.ssh/id_rsa
remote_host = rascalmicro.com
remote_username = root
port = 8000

rascal-autossh.py

#!/usr/bin/env python
"""rascal-autossh.py - starts and stops the autossh tunnel according to parameters in /etc/rascal-autossh.conf

Usage:
    rascal-autossh.py [start|stop|restart]
"""

import os
import sys
import getopt
import subprocess
import ConfigParser

RASCAL_AUTOSSH_CONFIG_FILE_PATH = '/etc/rascal-autossh.conf'

def ssh_keypair_exists(keypair_file_path):
    priv_key_path = keypair_file_path
    pub_key_path = keypair_file_path + '.pub'
    return os.path.exists(priv_key_path) and os.path.exists(pub_key_path)

def generate_ssh_keypair(keypair_file_path):
    priv_key_path = keypair_file_path
    pub_key_path = keypair_file_path + '.pub'

    # force full regeneration by deleting any old remnant files
    for filename in [priv_key_path,pub_key_path]:
        try:
            os.unlink(filename)
        except:
            pass

    # generate a new key pair
    p = subprocess.Popen([ '/usr/bin/ssh-keygen', '-b', '768', '-N', '', '-f', priv_key_path ], 
        stdout=subprocess.PIPE, 
        stderr=subprocess.PIPE)
    (stdoutdata, stderrdata) = p.communicate()
    rc = p.returncode

    if not (rc==0):
        print stdoutdata
        print stderrdata
        print "%s error:  ssh-keygen failed with code %i"%(sys.argv[0],rc)
        raise

# pub_key_path = keypair_file_path + '.pub'
# f = open(pub_key_path, 'r')
# pub_key = f.read()
# f.close()

def read_config_file(config_file_path):
    ret = {}
    config = ConfigParser.ConfigParser()
    config.read([ config_file_path ])
    if config.has_section('autossh_tunnel'):
        #tunnel_params = config.options('autossh_tunnel')
        required_params = ['ssh_keys','remote_host','remote_username','port','enabled']
        for param_name in required_params:
            if config.has_option('autossh_tunnel',param_name):
                ret[param_name] = config.get('autossh_tunnel',param_name)
            else:
                return None
    else:
        return None
    return ret

def start_autossh():
    print "Rascal autossh tunnel:  ",

    tunnel_params = read_config_file(RASCAL_AUTOSSH_CONFIG_FILE_PATH)
    if (tunnel_params == None) or (not tunnel_params['enabled'] == '1'):
        print 'no tunnel enabled in %s' % RASCAL_AUTOSSH_CONFIG_FILE_PATH
    else:
        # generate RSA key files if they don't exist yet
        if not ssh_keypair_exists(tunnel_params['ssh_keys']):
            print "\nGenerating SSH key pair in '%s'" % tunnel_params['ssh_keys']
            generate_ssh_keypair(tunnel_params['ssh_keys'])

        # start autossh
        p = subprocess.Popen([ 
            '/usr/local/bin/autossh', 
            '-M', '20000', 
            '-f', 
            '-i', tunnel_params['ssh_keys'],
            '-R', '*:%s:localhost:80'%(tunnel_params['port']),
            '-R', '*:2200:localhost:22',
            '%s@%s'%(tunnel_params['remote_username'],tunnel_params['remote_host']),
            '-N',
            ], 
            stdout=subprocess.PIPE, 
            stderr=subprocess.PIPE)
        (stdoutdata, stderrdata) = p.communicate()
        rc = p.returncode
        if rc == 0:
            print "started"
        else:
            print "failed to start (return code %i)" % rc
        
def stop_autossh():
    print 'Rascal autossh tunnel:  ',
    p = subprocess.Popen( ['killall', '-SIGINT', 'autossh'], stdout=subprocess.PIPE, stderr=subprocess.PIPE )
    (stdoutdata, stderrdata) = p.communicate()
    rc = p.returncode
    if rc == 0:
        print "stopped"
    else:
        print "failed to kill autossh (was it running?), return code %i" % rc

def main(argv=None):
    # parse command line options
    if argv is None:
        argv = sys.argv
    try:
        opts, args = getopt.getopt(argv[1:], "h", ["help"])
    except getopt.error, msg:
        print msg
        print "for help use --help"
        return 2
    # process options
    for o, a in opts:
        if o in ("-h", "--help"):
            print __doc__
            return 0

    # expecting 1 argument ('start', 'stop' or 'restart')
    if not len(args) == 1:
        print "%s error:  wrong number of arguments; -h for help" % argv[0]
        return 2

    command = args[0]
    if command == 'start':
        start_autossh()
    elif command == 'stop':
        stop_autossh()
    elif command == 'restart':
        stop_autossh()
        start_autossh()
    else:
        print "%s error:  '%s' is not a valid command; -h for help" % (argv[0], command)
        return 2

    return 0

if __name__ == "__main__":
    sys.exit(main())