shell bypass 403
import os
import sys
import stat
import select
import time
import errno
try:
InterruptedError
except NameError:
# Alias Python2 exception to Python3
InterruptedError = select.error
if sys.version_info[0] >= 3:
string_types = (str,)
else:
string_types = (unicode, str)
def is_executable_file(path):
"""Checks that path is an executable regular file, or a symlink towards one.
This is roughly ``os.path isfile(path) and os.access(path, os.X_OK)``.
"""
# follow symlinks,
fpath = os.path.realpath(path)
if not os.path.isfile(fpath):
# non-files (directories, fifo, etc.)
return False
mode = os.stat(fpath).st_mode
if (sys.platform.startswith('sunos')
and os.getuid() == 0):
# When root on Solaris, os.X_OK is True for *all* files, irregardless
# of their executability -- instead, any permission bit of any user,
# group, or other is fine enough.
#
# (This may be true for other "Unix98" OS's such as HP-UX and AIX)
return bool(mode & (stat.S_IXUSR |
stat.S_IXGRP |
stat.S_IXOTH))
return os.access(fpath, os.X_OK)
def which(filename, env=None):
'''This takes a given filename; tries to find it in the environment path;
then checks if it is executable. This returns the full path to the filename
if found and executable. Otherwise this returns None.'''
# Special case where filename contains an explicit path.
if os.path.dirname(filename) != '' and is_executable_file(filename):
return filename
if env is None:
env = os.environ
p = env.get('PATH')
if not p:
p = os.defpath
pathlist = p.split(os.pathsep)
for path in pathlist:
ff = os.path.join(path, filename)
if is_executable_file(ff):
return ff
return None
def split_command_line(command_line):
'''This splits a command line into a list of arguments. It splits arguments
on spaces, but handles embedded quotes, doublequotes, and escaped
characters. It's impossible to do this with a regular expression, so I
wrote a little state machine to parse the command line. '''
arg_list = []
arg = ''
# Constants to name the states we can be in.
state_basic = 0
state_esc = 1
state_singlequote = 2
state_doublequote = 3
# The state when consuming whitespace between commands.
state_whitespace = 4
state = state_basic
for c in command_line:
if state == state_basic or state == state_whitespace:
if c == '\\':
# Escape the next character
state = state_esc
elif c == r"'":
# Handle single quote
state = state_singlequote
elif c == r'"':
# Handle double quote
state = state_doublequote
elif c.isspace():
# Add arg to arg_list if we aren't in the middle of whitespace.
if state == state_whitespace:
# Do nothing.
None
else:
arg_list.append(arg)
arg = ''
state = state_whitespace
else:
arg = arg + c
state = state_basic
elif state == state_esc:
arg = arg + c
state = state_basic
elif state == state_singlequote:
if c == r"'":
state = state_basic
else:
arg = arg + c
elif state == state_doublequote:
if c == r'"':
state = state_basic
else:
arg = arg + c
if arg != '':
arg_list.append(arg)
return arg_list
def select_ignore_interrupts(iwtd, owtd, ewtd, timeout=None):
'''This is a wrapper around select.select() that ignores signals. If
select.select raises a select.error exception and errno is an EINTR
error then it is ignored. Mainly this is used to ignore sigwinch
(terminal resize). '''
# if select() is interrupted by a signal (errno==EINTR) then
# we loop back and enter the select() again.
if timeout is not None:
end_time = time.time() + timeout
while True:
try:
return select.select(iwtd, owtd, ewtd, timeout)
except InterruptedError:
err = sys.exc_info()[1]
if err.args[0] == errno.EINTR:
# if we loop back we have to subtract the
# amount of time we already waited.
if timeout is not None:
timeout = end_time - time.time()
if timeout < 0:
return([], [], [])
else:
# something else caused the select.error, so
# this actually is an exception.
raise
def poll_ignore_interrupts(fds, timeout=None):
'''Simple wrapper around poll to register file descriptors and
ignore signals.'''
if timeout is not None:
end_time = time.time() + timeout
poller = select.poll()
for fd in fds:
poller.register(fd, select.POLLIN | select.POLLPRI | select.POLLHUP | select.POLLERR)
while True:
try:
timeout_ms = None if timeout is None else timeout * 1000
results = poller.poll(timeout_ms)
return [afd for afd, _ in results]
except InterruptedError:
err = sys.exc_info()[1]
if err.args[0] == errno.EINTR:
# if we loop back we have to subtract the
# amount of time we already waited.
if timeout is not None:
timeout = end_time - time.time()
if timeout < 0:
return []
else:
# something else caused the select.error, so
# this actually is an exception.
raise