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# maybe - see what a program does before deciding whether you really want it to happen
#
# Copyright (c) 2016 Philipp Emanuel Weidmann <pew@worldwidemann.com>
#
# Nemo vir est qui mundum non reddat meliorem.
#
# Released under the terms of the GNU General Public License, version 3
# (https://gnu.org/licenses/gpl.html)
from pwd import getpwuid
from grp import getgrgid
from collections import namedtuple
from os.path import abspath, dirname, basename, exists
from os import O_WRONLY, O_RDWR, O_APPEND, O_CREAT, O_TRUNC
from stat import S_IFCHR, S_IFBLK, S_IFIFO, S_IFSOCK
from .utilities import T, format_permissions
def format_delete(path):
return "%s %s" % (T.red("delete"), T.underline(abspath(path)))
def format_move(path_old, path_new):
path_old = abspath(path_old)
path_new = abspath(path_new)
if dirname(path_old) == dirname(path_new):
label = "rename"
path_new = basename(path_new)
else:
label = "move"
return "%s %s to %s" % (T.green(label), T.underline(path_old), T.underline(path_new))
def format_change_permissions(path, permissions):
return "%s of %s to %s" % (T.yellow("change permissions"), T.underline(abspath(path)),
T.bold(format_permissions(permissions)))
def format_change_owner(path, owner, group):
if owner == -1:
label = "change group"
owner = getgrgid(group)[0]
elif group == -1:
label = "change owner"
owner = getpwuid(owner)[0]
else:
label = "change owner"
owner = getpwuid(owner)[0] + ":" + getgrgid(group)[0]
return "%s of %s to %s" % (T.yellow(label), T.underline(abspath(path)), T.bold(owner))
def format_create_directory(path):
return "%s %s" % (T.cyan("create directory"), T.underline(abspath(path)))
def format_create_link(path_source, path_target, symbolic):
label = "create symbolic link" if symbolic else "create hard link"
return "%s from %s to %s" % (T.cyan(label), T.underline(abspath(path_source)), T.underline(abspath(path_target)))
# Start with a large number to avoid collisions with other FDs
# TODO: This approach is extremely brittle!
next_file_descriptor = 1000
file_descriptors = {}
def get_next_file_descriptor():
global next_file_descriptor
file_descriptor = next_file_descriptor
next_file_descriptor += 1
return file_descriptor
def get_file_descriptor_path(file_descriptor):
return file_descriptors.get(file_descriptor, "/dev/fd/%d" % file_descriptor)
allowed_files = set(["/dev/null", "/dev/zero", "/dev/tty"])
def format_open(path, flags):
path = abspath(path)
if path in allowed_files:
return None
elif (flags & O_CREAT) and not exists(path):
return "%s %s" % (T.cyan("create file"), T.underline(path))
elif (flags & O_TRUNC) and exists(path):
return "%s %s" % (T.red("truncate file"), T.underline(path))
else:
return None
def substitute_open(path, flags):
path = abspath(path)
if path in allowed_files:
return None
elif (flags & O_WRONLY) or (flags & O_RDWR) or (flags & O_APPEND) or (format_open(path, flags) is not None):
# File might be written to later, so we need to track the file descriptor
file_descriptor = get_next_file_descriptor()
file_descriptors[file_descriptor] = path
return file_descriptor
else:
return None
def format_mknod(path, type):
path = abspath(path)
if exists(path):
return None
elif (type & S_IFCHR):
label = "create character special file"
elif (type & S_IFBLK):
label = "create block special file"
elif (type & S_IFIFO):
label = "create named pipe"
elif (type & S_IFSOCK):
label = "create socket"
else:
# mknod(2): "Zero file type is equivalent to type S_IFREG"
label = "create file"
return "%s %s" % (T.cyan(label), T.underline(path))
def substitute_mknod(path, type):
return None if (format_mknod(path, type) is None) else 0
def format_write(file_descriptor, byte_count):
if file_descriptor in file_descriptors:
path = file_descriptors[file_descriptor]
return "%s %s to %s" % (T.red("write"), T.bold("%d bytes" % byte_count), T.underline(path))
else:
return None
def substitute_write(file_descriptor, byte_count):
return None if (format_write(file_descriptor, byte_count) is None) else byte_count
def substitute_dup(file_descriptor_old, file_descriptor_new=None):
if file_descriptor_old in file_descriptors:
if file_descriptor_new is None:
file_descriptor_new = get_next_file_descriptor()
# Copy tracked file descriptor
file_descriptors[file_descriptor_new] = file_descriptors[file_descriptor_old]
return file_descriptor_new
else:
return None
SyscallFilter = namedtuple("SyscallFilter", ["name", "signature", "format", "substitute"])
# Make returning zero the default substitute function
# Source: http://stackoverflow.com/a/18348004
SyscallFilter.__new__.__defaults__ = (lambda args: 0,)
SYSCALL_FILTERS = [
# Delete
SyscallFilter(
name="unlink",
signature=("int", (("const char *", "pathname"),)),
format=lambda args: format_delete(args[0]),
),
SyscallFilter(
name="unlinkat",
signature=("int", (("int", "dirfd"), ("const char *", "pathname"), ("int", "flags"),)),
format=lambda args: format_delete(args[1]),
),
SyscallFilter(
name="rmdir",
signature=("int", (("const char *", "pathname"),)),
format=lambda args: format_delete(args[0]),
),
# Move
SyscallFilter(
name="rename",
signature=("int", (("const char *", "oldpath"), ("const char *", "newpath"),)),
format=lambda args: format_move(args[0], args[1]),
),
SyscallFilter(
name="renameat",
signature=("int", (("int", "olddirfd"), ("const char *", "oldpath"),
("int", "newdirfd"), ("const char *", "newpath"),)),
format=lambda args: format_move(args[1], args[3]),
),
SyscallFilter(
name="renameat2",
signature=("int", (("int", "olddirfd"), ("const char *", "oldpath"),
("int", "newdirfd"), ("const char *", "newpath"), ("unsigned int", "flags"),)),
format=lambda args: format_move(args[1], args[3]),
),
# Change permissions
SyscallFilter(
name="chmod",
signature=("int", (("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_change_permissions(args[0], args[1]),
),
SyscallFilter(
name="fchmod",
signature=("int", (("int", "fd"), ("mode_t", "mode"),)),
format=lambda args: format_change_permissions(get_file_descriptor_path(args[0]), args[1]),
),
SyscallFilter(
name="fchmodat",
signature=("int", (("int", "dirfd"), ("const char *", "pathname"), ("mode_t", "mode"), ("int", "flags"),)),
format=lambda args: format_change_permissions(args[1], args[2]),
),
# Change owner
SyscallFilter(
name="chown",
signature=("int", (("const char *", "pathname"), ("uid_t", "owner"), ("gid_t", "group"),)),
format=lambda args: format_change_owner(args[0], args[1], args[2]),
),
SyscallFilter(
name="fchown",
signature=("int", (("int", "fd"), ("uid_t", "owner"), ("gid_t", "group"),)),
format=lambda args: format_change_owner(get_file_descriptor_path(args[0]), args[1], args[2]),
),
SyscallFilter(
name="lchown",
signature=("int", (("const char *", "pathname"), ("uid_t", "owner"), ("gid_t", "group"),)),
format=lambda args: format_change_owner(args[0], args[1], args[2]),
),
SyscallFilter(
name="fchownat",
signature=("int", (("int", "dirfd"), ("const char *", "pathname"),
("uid_t", "owner"), ("gid_t", "group"), ("int", "flags"),)),
format=lambda args: format_change_owner(args[1], args[2], args[3]),
),
# Create directory
SyscallFilter(
name="mkdir",
signature=("int", (("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_create_directory(args[0]),
),
SyscallFilter(
name="mkdirat",
signature=("int", (("int", "dirfd"), ("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_create_directory(args[1]),
),
# Create link
SyscallFilter(
name="link",
signature=("int", (("const char *", "oldpath"), ("const char *", "newpath"),)),
format=lambda args: format_create_link(args[1], args[0], False),
),
SyscallFilter(
name="linkat",
signature=("int", (("int", "olddirfd"), ("const char *", "oldpath"),
("int", "newdirfd"), ("const char *", "newpath"), ("int", "flags"),)),
format=lambda args: format_create_link(args[3], args[1], False),
),
SyscallFilter(
name="symlink",
signature=("int", (("const char *", "target"), ("const char *", "linkpath"),)),
format=lambda args: format_create_link(args[1], args[0], True),
),
SyscallFilter(
name="symlinkat",
signature=("int", (("const char *", "target"), ("int", "newdirfd"), ("const char *", "linkpath"),)),
format=lambda args: format_create_link(args[2], args[0], True),
),
# Open/create file
SyscallFilter(
name="open",
# TODO: "open" is overloaded (a version with 3 arguments also exists). Are both handled properly?
signature=("int", (("const char *", "pathname"), ("int", "flags"),)),
format=lambda args: format_open(args[0], args[1]),
substitute=lambda args: substitute_open(args[0], args[1]),
),
SyscallFilter(
name="creat",
signature=("int", (("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_open(args[0], O_CREAT | O_WRONLY | O_TRUNC),
substitute=lambda args: substitute_open(args[0], O_CREAT | O_WRONLY | O_TRUNC),
),
SyscallFilter(
name="openat",
# TODO: "openat" is overloaded (see above)
signature=("int", (("int", "dirfd"), ("const char *", "pathname"), ("int", "flags"),)),
format=lambda args: format_open(args[1], args[2]),
substitute=lambda args: substitute_open(args[1], args[2]),
),
SyscallFilter(
name="mknod",
signature=("int", (("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_mknod(args[0], args[1]),
substitute=lambda args: substitute_mknod(args[0], args[1]),
),
SyscallFilter(
name="mknodat",
signature=("int", (("int", "dirfd"), ("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_mknod(args[1], args[2]),
substitute=lambda args: substitute_mknod(args[1], args[2]),
),
SyscallFilter(
name="mkfifo",
signature=("int", (("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_mknod(args[0], S_IFIFO),
substitute=lambda args: substitute_mknod(args[0], S_IFIFO),
),
SyscallFilter(
name="mkfifoat",
signature=("int", (("int", "dirfd"), ("const char *", "pathname"), ("mode_t", "mode"),)),
format=lambda args: format_mknod(args[1], S_IFIFO),
substitute=lambda args: substitute_mknod(args[1], S_IFIFO),
),
# Write to file
SyscallFilter(
name="write",
signature=("ssize_t", (("int", "fd"), ("const void *", "buf"), ("size_t", "count"),)),
format=lambda args: format_write(args[0], args[2]),
substitute=lambda args: substitute_write(args[0], args[2]),
),
SyscallFilter(
name="pwrite",
signature=("ssize_t", (("int", "fd"), ("const void *", "buf"), ("size_t", "count"), ("off_t", "offset"),)),
format=lambda args: format_write(args[0], args[2]),
substitute=lambda args: substitute_write(args[0], args[2]),
),
SyscallFilter(
name="writev",
signature=("ssize_t", (("int", "fd"), ("const struct iovec *", "iov"), ("int", "iovcnt"),)),
# TODO: Actual byte count is iovcnt * iov.iov_len
format=lambda args: format_write(args[0], args[2]),
substitute=lambda args: substitute_write(args[0], args[2]),
),
SyscallFilter(
name="pwritev",
signature=("ssize_t", (("int", "fd"), ("const struct iovec *", "iov"), ("int", "iovcnt"), ("off_t", "offset"),)),
# TODO: Actual byte count is iovcnt * iov.iov_len
format=lambda args: format_write(args[0], args[2]),
substitute=lambda args: substitute_write(args[0], args[2]),
),
# Duplicate file descriptor
SyscallFilter(
name="dup",
signature=("int", (("int", "oldfd"),)),
format=lambda args: None,
substitute=lambda args: substitute_dup(args[0]),
),
SyscallFilter(
name="dup2",
signature=("int", (("int", "oldfd"), ("int", "newfd"),)),
format=lambda args: None,
substitute=lambda args: substitute_dup(args[0], args[1]),
),
SyscallFilter(
name="dup3",
signature=("int", (("int", "oldfd"), ("int", "newfd"), ("int", "flags"),)),
format=lambda args: None,
substitute=lambda args: substitute_dup(args[0], args[1]),
),
]
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