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#!/usr/bin/env python2.4
"""module for executing the programs, that need root privileges
Syntax:
- program
- device
- [action]
- [action args]
this script will always return with an exitcode 0 (true), if "check" is the only argument
"""
import os
import sys
import subprocess
import pwd
import grp
import types
allowedProgs = {
"sfdisk": "/sbin/sfdisk",
"cryptsetup": "/sbin/cryptsetup",
"mount": "/bin/mount",
"umount": "/bin/umount",
"blkid": "/sbin/blkid",
}
DEV_TYPES = { "pipe":1, "char":2, "dir":4, "block":6, "file":8, "link":10, "socket":12}
def checkIfPluginIsSafe(plugin):
"""check if the plugin and its parents are only writeable for root"""
#FIXME: for now we may skip this test - but users will not like it this way :)
return True
props = os.stat(plugin)
## check if it is owned by non-root
if props.st_uid != 0: return False
## check group-write permission if gid is not zero
if (props.st_gid != 0) and (props.st_mode % 32 / 16 > 0): return False
## check if it is world-writeable
if props.st_mode % 4 / 2 > 0: return False
## are we at root-level (directory-wise)? If yes, then we are ok ...
if plugin == os.path.sep: return True
## check if the parent directory is ok - recursively :)
return checkIfPluginIsSafe(os.path.dirname(os.path.abspath(plugin)))
def checkIfPluginIsValid(plugin):
import imp
try:
x = imp.load_source("cbox_plugin",plugin)
except Exception:
return False
try:
if getattr(x, "PLUGIN_TYPE") == "cryptobox":
return True
else:
return False
except Exception:
return False
def call_plugin(args):
"""check if the plugin may be called - and do it finally ..."""
plugin = os.path.abspath(args[0])
del args[0]
## check existence and excutability
if not os.access(plugin, os.X_OK):
raise Exception, "could not find executable plugin (%s)" % plugin
## check if the plugin (and its parents) are only writeable for root
if not checkIfPluginIsSafe(plugin):
raise Exception, "the plugin (%s) was not safe - check its (and its parents') permissions" % plugin
## check if the plugin is a python program, that is marked as a cryptobox plugin
if not checkIfPluginIsValid(plugin):
raise Exception, "the plugin (%s) is not a correctly marked python script" % plugin
args.insert(0,plugin)
proc = subprocess.Popen(
shell = False,
args = args)
proc.wait()
return proc.returncode == 0
def isWriteable(device, force_dev_type=None):
"""check if the calling user (not root!) has write access to the device/file
the real (not the effictive) user id is used for the check
additionally the permissions of the default groups of the real uid are checked
this check works nicely together with "super", as it changes (by default) only
the effective uid (not the real uid)
"""
# first check, if the device/file exists
if not os.path.exists(device):
return False
# check the type of the device - if necessary
if not force_dev_type is None:
dev_type = os.stat(device).st_mode % 65536 / 4096
if dev_type != force_dev_type: return False
# retrieve the information for the real user id
(trustUserName, trustUID, groupsOfTrustUser) = getUserInfo(os.getuid())
# set the default groups of the caller for the check (restore them later)
savedGroups = os.getgroups()
os.setgroups(groupsOfTrustUser)
# check permissions
result = os.access(device, os.W_OK) and os.access(device, os.R_OK)
# reset the groups of this process
os.setgroups(savedGroups)
return result
def run_cryptsetup(args):
"""execute cryptsetup as root
@args: list of arguments - they will be treated accordingly to the first element
of this list (the action)"""
if not args: raise "WrongArguments", "no action for cryptsetup supplied"
if type(args) != types.ListType: raise "WrongArguments", "invalid arguments supplied: %s" % (args, )
try:
action = args[0]
del args[0]
device = None
cmd_args = []
if action == "luksFormat":
device = args[0]; del args[0]
cmd_args.append(action)
cmd_args.append(device)
elif action == "luksUUID":
device = args[0]; del args[0]
cmd_args.append(action)
cmd_args.append(device)
elif action == "luksOpen":
if len(args) < 2: raise "WrongArguments", "missing arguments"
device = args[0]; del args[0]
destination = args[0]; del args[0]
cmd_args.append(action)
cmd_args.append(device)
cmd_args.append(destination)
elif action == "luksClose":
if len(args) < 1: raise "WrongArguments", "missing arguments"
destination = args[0]; del args[0]
# maybe add a check for the mapped device's permissions?
# dmsetup deps self.device
cmd_args.append(action)
cmd_args.append(destination)
elif action == "luksAddKey":
device = args[0]; del args[0]
cmd_args.append(action)
cmd_args.append(device)
elif action == "luksDelKey":
if len(cs_args) < 2: raise "WrongArguments", "missing arguments"
device = args[0]; del args[0]
cmd_args.insert(-1, action)
cmd_args.insert(-1, device)
elif action == "isLuks":
device = args[0]; del args[0]
cmd_args.append(action)
cmd_args.append(device)
else: raise "WrongArguments", "invalid action supplied: %s" % (action, )
# check if a device was defined - and check it
if (not device is None) and (not isWriteable(device, DEV_TYPES["block"])):
raise "WrongArguments", "%s is not a writeable block device" % (device, )
cs_args = [allowedProgs["cryptsetup"]]
cs_args.extend(args)
cs_args.extend(cmd_args)
except (TypeError, IndexError):
raise "WrongArguments", "invalid arguments supplied: %s" % (args, )
# execute cryptsetup with the given parameters
proc = subprocess.Popen(
shell = False,
args = cs_args)
proc.wait()
## chown the devmapper block device to the cryptobox user
if (proc.returncode == 0) and (action == "luksOpen"):
os.chown(os.path.join(os.path.sep, "dev", "mapper", destination), os.getuid(), os.getgid())
return proc.returncode == 0
def run_sfdisk(args):
"""execute sfdisk for partitioning
not implemented yet"""
print "ok - you are free to call sfdisk ..."
print " not yet implemented ..."
return True
def getFSType(device):
"""get the filesystem type of a device"""
proc = subprocess.Popen(
shell = False,
stdout = subprocess.PIPE,
args = [ allowedProgs["blkid"],
"-s", "TYPE",
"-o", "value",
"-c", os.devnull,
"-w", os.devnull,
device])
(stdout, stderr) = proc.communicate()
if proc.returncode != 0:
return None
return stdout.strip()
def run_mount(args):
"""execute mount
"""
if not args: raise "WrongArguments", "no destination for mount supplied"
if type(args) != types.ListType: raise "WrongArguments", "invalid arguments supplied: %s" % (args, )
try:
device = args[0]
del args[0]
destination = args[0]
del args[0]
# check permissions for the device
if not isWriteable(device, DEV_TYPES["block"]):
raise "WrongArguments", "%s is not a writeable block device" % (device, )
## check permissions for the mountpoint
if not isWriteable(destination, DEV_TYPES["dir"]):
raise "WrongArguments", "the mountpoint (%s) is not writeable" % (destination, )
# check for additional (not allowed) arguments
if len(args) != 0:
raise "WrongArguments", "too many arguments for 'mount': %s" % (args, )
except TypeError:
raise "WrongArguments", "invalid arguments supplied: %s" % (args, )
# execute mount with the given parameters
# first overwrite the real uid, as 'mount' wants this to be zero (root)
savedUID = os.getuid()
os.setuid(os.geteuid())
## we have to change the permissions of the mounted directory - otherwise it will
## not be writeable for the cryptobox user
## for 'vfat' we have to do this during mount
## for ext2/3 we have to do it afterward
## first: get the user/group of the target
(trustUserName, trustUID, groupsOfTrustUser) = getUserInfo(savedUID)
trustGID = groupsOfTrustUser[0]
fsType = getFSType(device)
## define arguments
if fsType == "vfat":
## add the "uid/gid" arguments to the mount call
mount_args = [allowedProgs["mount"],
"-o", "uid=%d,gid=%d" % (trustUID, trustGID),
device,
destination]
else:
## all other filesystem types will be handled after mount
mount_args = [allowedProgs["mount"], device, destination]
# execute mount
proc = subprocess.Popen(
shell = False,
args = mount_args)
proc.wait()
## return in case of an error
if proc.returncode != 0:
return False
## for vfat: we are done
if fsType == "vfat": return True
## for all other filesystem types: chown the mount directory
try:
os.chown(destination, trustUID, groupsOfTrustUser[0])
except OSError, errMsg:
sys.stderr.write("could not chown the mount destination (%s) to the specified user (%d/%d): %s\n" % (destination, trustUID, groupsOfTrustUser[0], errMsg))
sys.stderr.write("UID: %d\n" % (os.geteuid(),))
return False
## BEWARE: it would be nice, if we could restore the previous uid (not euid) but
## this would also override the euid (see 'man 2 setuid') - any ideas?
return True
def run_umount(args):
"""execute mount
"""
if not args: raise "WrongArguments", "no mountpoint for umount supplied"
if type(args) != types.ListType: raise "WrongArguments", "invalid arguments supplied"
try:
destination = args[0]
del args[0]
# check permissions for the destination
if not isWriteable(os.path.dirname(destination), DEV_TYPES["dir"]):
raise "WrongArguments", "the parent of the mountpoint (%s) is not writeable" % (destination, )
if len(args) != 0: raise "WrongArguments", "umount does not allow arguments"
except TypeError:
raise "WrongArguments", "invalid arguments supplied"
# execute umount with the given parameters
# first overwrite the real uid, as 'umount' wants this to be zero (root)
savedUID = os.getuid()
os.setuid(os.geteuid())
# execute umount (with the parameter '-l' - lazy umount)
proc = subprocess.Popen(
shell = False,
args = [allowedProgs["umount"], "-l", destination])
proc.wait()
# restore previous real uid
os.setuid(savedUID)
return proc.returncode == 0
def getUserInfo(user):
"""return information about the specified user
@user: (uid or name)
@return: tuple of (name, uid, (groups))
"""
if user is None: raise "KeyError", "no user supplied"
# first check, if 'user' contains an id - then check for a name
try:
userinfo = pwd.getpwuid(user)
except TypeError:
# if a KeyError is raised again, then the supplied user was invalid
userinfo = pwd.getpwnam(user)
u_groups =[one_group.gr_gid
for one_group in grp.getgrall()
if userinfo.pw_name in one_group.gr_mem]
if not userinfo.pw_gid in u_groups: u_groups.append(userinfo.pw_gid)
return (userinfo.pw_name, userinfo.pw_uid, u_groups)
# **************** main **********************
# prevent import
if __name__ == "__main__":
# do we have root privileges (effective uid is zero)?
if os.geteuid() != 0:
sys.stderr.write("the effective uid is not zero - you should use 'super' to call this script (%s)" % sys.argv[0])
sys.exit(100)
# remove program name
args = sys.argv[1:]
# do not allow to use root permissions (real uid may not be zero)
if os.getuid() == 0:
sys.stderr.write("the uid of the caller is zero (root) - this is not allowed\n")
sys.exit(100)
# check if there were arguments
if (len(args) == 0):
sys.stderr.write("No arguments supplied\n")
sys.exit(100)
# did the user call the "check" action?
if (len(args) == 1) and (args[0].lower() == "check"):
# exit silently
sys.exit(0)
if args[0].lower() == "plugin":
del args[0]
try:
isOK = call_plugin(args)
except Exception, errMsg:
sys.stderr.write("Execution of plugin failed: %s\n" % errMsg)
sys.exit(100)
if isOK:
sys.exit(0)
else:
sys.exit(1)
# check parameters count
if len(args) < 2:
sys.stderr.write("Not enough arguments supplied (%s)!\n" % " ".join(args))
sys.exit(100)
progRequest = args[0]
del args[0]
if not progRequest in allowedProgs.keys():
sys.stderr.write("Invalid program requested: %s\n" % progRequest)
sys.exit(100)
if progRequest == "cryptsetup": runner = run_cryptsetup
elif progRequest == "sfdisk": runner = run_sfdisk
elif progRequest == "mount": runner = run_mount
elif progRequest == "umount": runner = run_umount
else:
sys.stderr.write("The interface for this program (%s) is not yet implemented!\n" % progRequest)
sys.exit(100)
try:
if runner(args):
sys.exit(0)
else:
sys.exit(1)
except "WrongArguments", errstr:
sys.stderr.write("Execution failed: %s\n" % errstr)
sys.exit(100)