schsh

   1 #!/usr/bin/python
   2 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~#
   3 # Configuration
   4 shell = None # set to "/bin/bash" or similar to allow shell access
   5
   6 def allowSCP(run):
   7         if len(run) != 3: return False
   8         if run[0] != "scp": return False
   9         if run[1] not in ("-f", "-t"): return False
  10         if run[2].startswith('-'): return False
  11         return True
  12
  13 def allowRSync(run):
  14         if len(run) < 3: return False
  15         if run[0] != "rsync": return False
  16         if run[1] != "--server": return False
  17         return True
  18
  19 def allowSFTP(run):
  20         if len(run) != 1: return False
  21         return run[0] == "/usr/lib/openssh/sftp-server"
  22
  23 allowCommands = [allowSCP, allowRSync, allowSFTP]
  24 commandPaths = ["/usr/bin", "/bin"]
  25
  26 # END of Configuration
  27 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~#
  28 # DO NOT TOUCH ANYTHING BELOW THIS LINE
  29
  30 import logging, logging.handlers
  31 import os, sys, shlex, pwd
  32
  33 logger = logging.getLogger("schsh")
  34 logger.setLevel(logging.INFO)
  35 logger.addHandler(logging.handlers.SysLogHandler(address = '/dev/log',
  36                                                 facility = logging.handlers.SysLogHandler.LOG_AUTH))
  37
  38 def get_username():
  39     return pwd.getpwuid(os.getuid()).pw_name
  40
  41 def log(msg, lvl = logging.INFO):
  42         logger.log(lvl, "%s[%d]: <%s> %s" % ("schsh", os.getpid(), get_username(), msg))
  43
  44 def logquit(msg):
  45         log(msg, logging.ERROR)
  46         sys.exit(1)
  47
  48 def commandAllowed(run):
  49         for allowed in allowCommands:
  50                 if allowed(run):
  51                         return True
  52         return False
  53
  54 def addPath(prog):
  55         if prog.startswith("/"):
  56                 return prog
  57         # look for it in the paths
  58         for path in commandPaths:
  59                 fullprog = os.path.join(path, prog)
  60                 if os.path.exists(fullprog):
  61                         return fullprog
  62         return None
  63
  64 # parse arguments
  65 run = []
  66 if len(sys.argv) == 1:
  67         if shell is None:
  68                 print "No shell for you!"
  69                 logquit("Shell access not allowed")
  70         else:
  71                 run = [shell]
  72 elif len(sys.argv) == 3 and sys.argv[1] == "-c":
  73         # check if the command is allowed, and add path
  74         run = shlex.split(sys.argv[2])
  75         if commandAllowed(run):
  76                 run[0] = addPath(run[0])
  77                 log("Running '"+str(run)+"'")
  78         else:
  79                 print "You are not allowed to run this command."
  80                 logquit("Attempt to run invalid command '"+sys.argv[2]+"'")
  81 else:
  82         logquit("Invalid arguments for schsh: "+str(sys.argv))
  83
  84 assert len(run) > 0
  85 os.execl("/usr/bin/schroot", "/usr/bin/schroot", "-c", "schsh-"+get_username(), "-d", "/data", "--", *run)