#!/usr/bin/python
#
#Copyright (c) 2010 Cloud Linux LTD
#All rights reserved.
#
#Redistribution and use in source and binary forms, with or without
#modification, are permitted provided that the following conditions
#are met:
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following
# disclaimer in the documentation and/or other materials provided
# with the distribution.
# * The names of its contributors may not be used to endorse or
# promote products derived from this software without specific
# prior written permission.
#
#THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
#"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
#LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
#FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
#COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
#INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
#BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
#LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
#CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
#LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
#ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
#POSSIBILITY OF SUCH DAMAGE.
#
# This module provides functions for secure I/O and filesystem operations
import os
from ctypes import *
libc = cdll.LoadLibrary("libc.so.6")
liblve = cdll.LoadLibrary("liblve.so.0")
# --- libc functions -----------------------------------------------
ino_t = c_long
off_t = c_long
class DIRENTRY(Structure):
_fields_ = [
('d_ino', ino_t), # inode number
('d_off', off_t), # offset to the next dirent
('d_reclen', c_ushort), # length of this record
('d_type', c_ubyte), # type of file; not supported by all file system types
('d_name', c_char * 256), # filename
]
DIRENTRY_P = POINTER(DIRENTRY)
fchown = libc.fchown
fchown.argtypes = [c_int, c_int, c_int]
fchown.restype = c_int
fchmod = libc.fchmod
fchmod.argtypes = [c_int, c_int]
fchmod.restype = c_int
fdopendir = libc.fdopendir
# accepts file/dir descriptor (integer)
fdopendir.argtypes = [c_int]
# returns pointer to DIR structure
fdopendir.restype = c_void_p
readdir = libc.readdir
# accepts pointer to DIR structure
readdir.argtypes = [c_void_p]
# returns pointer to DIRENTRY structure
readdir.restype = DIRENTRY_P
rewinddir = libc.rewinddir
# accepts pointer to DIR structure
rewinddir.argtypes = [c_void_p]
# returns void
rewinddir.restype = None
closedir = libc.closedir
# accepts pointer to DIR structure
closedir.argtypes = [c_void_p]
closedir.restype = c_int
# --- liblve functions -----------------------------------------------
# Opens path for reading not following symlinks and verifies that opened path is inside parent_path
# Returns:
# descriptor if successful
# -1 if path does not exist or is a symlink
# -2 if opened path is NOT inside parent_path or cannot be determined
# accepts path, parent_path
open_not_symlink = liblve.open_not_symlink
open_not_symlink.argtypes = [c_char_p, c_char_p]
open_not_symlink.restype = c_int
# Closes descriptor (if it is not equal -1)
# accepts file/dir descriptor (integer)
liblve.closefd.argtypes = [c_int]
# returns void
liblve.closefd.restype = None
# Tries to read first directory entry in order to ensure that descriptor is valid
# Returns 0 if reading succeeded or -1 if error has occured
check_dir = liblve.check_dir
# accepts descriptor
check_dir.argtypes = [c_int]
check_dir.restype = c_int
# Checks if path is a directory (in secure manner)
# Also opens path (if descriptor fd == -1) and then checks that opened path is inside parent_path
# Returns descriptor if path refers to directory
# Returns -1 if path does not exist or is not a directory
# Returns -2 if opened path is NOT inside parent_path or cannot be determined
isdir = liblve.isdir
# accepts path, descriptor, parent_path
isdir.argtypes = [c_char_p, c_int, c_char_p]
isdir.restype = c_int
# Sets permissions to directory (in secure manner)
# Returns descriptor if successful
# Returns -1 if error has occured
# Returns -2 if opened path is NOT inside parent_path or cannot be determined
# accepts: const char *path, mode_t perm, int fd, const char *parent_path
liblve.set_perm_dir_secure.argtypes = [c_char_p, c_int, c_int, c_char_p]
liblve.set_perm_dir_secure.restype = c_int
# Sets owner and group of directory (in secure manner)
# Returns descriptor if successful
# Returns -1 if error has occured
# Returns -2 if opened path is NOT inside parent_path or cannot be determined
# accepts: const char *path, uid_t uid, gid_t gid, int fd, const char *parent_path
liblve.set_owner_dir_secure.argtypes = [c_char_p, c_int, c_int, c_int, c_char_p]
liblve.set_owner_dir_secure.restype = c_int
# Creates directory if it does not exist, sets permissions/owner otherwise
# Returns descriptor if successful
# Returns -1 if error has occured
# accepts: const char *path, mode_t perm, uid_t uid, gid_t gid, int fd, const char *parent_path
liblve.create_dir_secure.argtypes = [c_char_p, c_int, c_int, c_int, c_int, c_char_p]
liblve.create_dir_secure.restype = c_int
# Recursive directory creation function
# Returns 0 if successful
# Returns -1 if error has occured
# accepts: const char *path, mode_t perm, uid_t uid, gid_t gid, const char *parent_path
liblve.makedirs_secure.argtypes = [c_char_p, c_int, c_int, c_int, c_char_p]
liblve.makedirs_secure.restype = c_int
# Writes absolute path pointed by descriptor fd to buffer *buf
# Returns buf if successful
# Returns NULL if error has occured
get_path_from_descriptor = liblve.get_path_from_descriptor
get_path_from_descriptor.argtypes = [c_int, c_char_p]
get_path_from_descriptor.restype = c_char_p
# Returns 1 if subdir is subdirectory of dir, 0 otherwise
is_subdir = liblve.is_subdir
is_subdir.argtypes = [c_char_p, c_char_p]
is_subdir.restype = c_int
# Returns list of entries of directory pointed by descriptor
def flistdir(fd):
# Duplicate descriptor, because closedir() closes descriptor associated with directory stream
fd2 = os.dup(fd)
# Open directory stream
dirp = fdopendir(fd2)
if not dirp:
raise Exception("fdopendir error")
# Reset position of directory stream
# (so it will be possible to read content of directory multiple times
# via other descriptors that refer to the directory)
rewinddir(dirp)
dirlist = []
while True:
entryp = readdir(dirp)
if not entryp:
break
entry = entryp.contents
dirlist.append(entry.d_name)
rewinddir(dirp)
closedir(dirp)
return dirlist
def closefd(fd):
if fd is not None:
try:
os.close(fd)
except OSError:
pass
# Sets permissions to directory (in secure manner)
# Returns descriptor if successful
# Returns None if error has occured
def set_perm_dir_secure(path, perm, parent_path, fd = None, logger = None):
if fd == None:
fd = -1
fd = liblve.set_perm_dir_secure(path, perm, fd, parent_path)
if fd > 0:
return fd
if logger is not None:
logger('Error: failed to set permissions of directory ' + path, False, True)
return None
# Sets owner and group of directory (in secure manner)
# Returns descriptor if successful
# Returns None if error has occured
def set_owner_dir_secure(path, uid, gid, parent_path, fd = None, logger = None):
if fd == None:
fd = -1
fd = liblve.set_owner_dir_secure(path, uid, gid, fd, parent_path)
if fd > 0:
return fd
if logger is not None:
logger('Error: failed to set owner of directory ' + path, False, True)
return None
# Creates directory if it does not exist, sets permissions/owner otherwise
# Returns descriptor if successful
# Returns None if error has occured
def create_dir_secure(path, perm, uid, gid, parent_path, fd = None, logger = None):
if fd == None:
fd = -1
fd = liblve.create_dir_secure(path, perm, uid, gid, fd, parent_path)
if fd > 0:
return fd
if logger is not None:
logger('Error: failed to create directory ' + path, False, True)
return None
# Recursive directory creation function
# Returns 0 if successful
# Returns -1 if error has occured
def makedirs_secure(path, perm, uid, gid, parent_path, logger = None):
res = liblve.makedirs_secure(path, perm, uid, gid, parent_path)
if res and logger:
logger('Error: failed to create directory ' + path, False, True)
return res
def set_capability(clear=False):
"""
Set CAP_SYS_RESOURCE capability
:param bool clear: Set on if it's true, set off otherwise
:return: 0 for success, -1 otherwise
:rtype: int
"""
if clear:
return liblve.disable_quota_capability()
else:
return liblve.enable_quota_capability()
def change_uid(uid):
"""
Change effective uid of current process and set CAP_SYS_RESOURCE capbality
to prevent "Disk quota exceeded" error
:param int euid: User ID to set it as current effective UID
:return: 0 if capability was set successfuly, -1 otherwise
:rtype: int
"""
os.setuid(uid)
return set_capability()