python/vserver.py

   1 # Copyright 2005 Princeton University
   2
   3 import errno
   4 import fcntl
   5 import os
   6 import re
   7
   8 import linuxcaps
   9 import passfdimpl
  10
  11 from vserver_vars import *
  12
  13 CAP_SAFE = (linuxcaps.CAP_CHOWN |
  14             linuxcaps.CAP_DAC_OVERRIDE |
  15             linuxcaps.CAP_DAC_READ_SEARCH |
  16             linuxcaps.CAP_FOWNER |
  17             linuxcaps.CAP_FSETID |
  18             linuxcaps.CAP_KILL |
  19             linuxcaps.CAP_SETGID |
  20             linuxcaps.CAP_SETUID |
  21             linuxcaps.CAP_SETPCAP |
  22             linuxcaps.CAP_SYS_TTY_CONFIG |
  23             linuxcaps.CAP_LEASE |
  24             linuxcaps.CAP_SYS_CHROOT |
  25             linuxcaps.CAP_SYS_PTRACE)
  26
  27 #
  28 # XXX - these are the flags taken from chcontext.c, but they don't match
  29 # up with those apparently used by the kernel
  30 #
  31 FLAGS_LOCK = 1
  32 FLAGS_SCHED = 2
  33 FLAGS_NPROC = 4
  34 FLAGS_PRIVATE = 8
  35 FLAGS_FAKEINIT = 16
  36 FLAGS_HIDEINFO = 32
  37 FLAGS_ULIMIT = 64
  38
  39
  40
  41 class VServer:
  42
  43     def __init__(self, name):
  44
  45         self.name = name
  46         self.config = self.__read_config_file("/etc/vservers.conf")
  47         self.config.update(self.__read_config_file("/etc/vservers/%s.conf" %
  48                                                    self.name))
  49         self.flags = 0
  50         flags = self.config["S_FLAGS"].split(" ")
  51         if "lock" in flags:
  52             self.flags |= FLAGS_LOCK
  53         if "nproc" in flags:
  54             self.flags |= FLAGS_NPROC
  55         self.remove_caps = ~CAP_SAFE
  56         print "%x %x" % (self.flags, ~self.remove_caps)
  57
  58     config_var_re = re.compile(r"^ *([A-Z_]+)=(.*)\n?$", re.MULTILINE)
  59
  60     def __read_config_file(self, filename):
  61
  62         f = open(filename, "r")
  63         data = f.read()
  64         f.close()
  65         config = {}
  66         for m in self.config_var_re.finditer(data):
  67             (key, val) = m.groups()
  68             config[key] = val.strip('"')
  69         return config
  70
  71     def open(self, filename, mode = "r"):
  72
  73         (sendsock, recvsock) = passfdimpl.socketpair()
  74         child_pid = os.fork()
  75         if child_pid == 0:
  76             try:
  77                 # child process
  78                 os.chroot("%s/%s" % (VROOTDIR, self.name))
  79                 f = open(filename, mode)
  80                 passfdimpl.sendmsg(f.fileno(), sendsock)
  81                 os._exit(0)
  82             except EnvironmentError, ex:
  83                 (result, errmsg) = (ex.errno, ex.strerror)
  84             except Exception, ex:
  85                 (result, errmsg) = (255, str(ex))
  86             os.write(sendsock, errmsg)
  87             os._exit(result)
  88
  89         # parent process
  90
  91         # XXX - need this since a lambda can't raise an exception
  92         def __throw(ex):
  93             raise ex
  94
  95         os.close(sendsock)
  96         throw = lambda : __throw(Exception(errmsg))
  97         while True:
  98             try:
  99                 (pid, status) = os.waitpid(child_pid, 0)
 100                 if os.WIFEXITED(status):
 101                     result = os.WEXITSTATUS(status)
 102                     if result != 255:
 103                         errmsg = os.strerror(result)
 104                         throw = lambda : __throw(IOError(result, errmsg))
 105                     else:
 106                         errmsg = "unexpected exception in child"
 107                 else:
 108                     result = -1
 109                     errmsg = "child killed"
 110                 break
 111             except OSError, ex:
 112                 if ex.errno != errno.EINTR:
 113                     os.close(recvsock)
 114                     raise ex
 115         fcntl.fcntl(recvsock, fcntl.F_SETFL, os.O_NONBLOCK)
 116         try:
 117             (fd, errmsg) = passfdimpl.recvmsg(recvsock)
 118         except OSError, ex:
 119             if ex.errno != errno.EAGAIN:
 120                 throw = lambda : __throw(ex)
 121             fd = 0
 122         os.close(recvsock)
 123         if not fd:
 124             throw()
 125
 126         return os.fdopen(fd)