# Authors: Simo Sorce # # Copyright (C) 2007-2016 Red Hat, Inc. # see file 'COPYING' for use and warranty information # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program. If not, see . # from __future__ import print_function import codecs import string import tempfile import subprocess import random import math import os import sys import copy import stat import shutil import socket import re import datetime import netaddr import netifaces import time import pwd import grp from contextlib import contextmanager import locale import collections from subprocess import CalledProcessError from dns import resolver, reversename from dns.exception import DNSException import six from six.moves import input from six.moves import urllib from ipapython.ipa_log_manager import root_logger from ipapython.dn import DN # only for OTP password that is manually retyped by user TMP_PWD_ENTROPY_BITS = 128 PROTOCOL_NAMES = { socket.SOCK_STREAM: 'tcp', socket.SOCK_DGRAM: 'udp' } class UnsafeIPAddress(netaddr.IPAddress): """Any valid IP address with or without netmask.""" # Use inet_pton() rather than inet_aton() for IP address parsing. We # will use the same function in IPv4/IPv6 conversions + be stricter # and don't allow IP addresses such as '1.1.1' in the same time netaddr_ip_flags = netaddr.INET_PTON def __init__(self, addr): if isinstance(addr, UnsafeIPAddress): self._net = addr._net super(UnsafeIPAddress, self).__init__(addr, flags=self.netaddr_ip_flags) return elif isinstance(addr, netaddr.IPAddress): self._net = None # no information about netmask super(UnsafeIPAddress, self).__init__(addr, flags=self.netaddr_ip_flags) return elif isinstance(addr, netaddr.IPNetwork): self._net = addr super(UnsafeIPAddress, self).__init__(self._net.ip, flags=self.netaddr_ip_flags) return # option of last resort: parse it as string self._net = None addr = str(addr) try: try: addr = netaddr.IPAddress(addr, flags=self.netaddr_ip_flags) except netaddr.AddrFormatError: # netaddr.IPAddress doesn't handle zone indices in textual # IPv6 addresses. Try removing zone index and parse the # address again. addr, sep, _foo = addr.partition('%') if sep != '%': raise addr = netaddr.IPAddress(addr, flags=self.netaddr_ip_flags) if addr.version != 6: raise except ValueError: self._net = netaddr.IPNetwork(addr, flags=self.netaddr_ip_flags) addr = self._net.ip super(UnsafeIPAddress, self).__init__(addr, flags=self.netaddr_ip_flags) def __getstate__(self): state = { '_net': self._net, 'super_state': super(UnsafeIPAddress, self).__getstate__(), } return state def __setstate__(self, state): super(UnsafeIPAddress, self).__setstate__(state['super_state']) self._net = state['_net'] class CheckedIPAddress(UnsafeIPAddress): """IPv4 or IPv6 address with additional constraints. Reserved or link-local addresses are never accepted. """ def __init__(self, addr, match_local=False, parse_netmask=True, allow_loopback=False, allow_multicast=False): try: super(CheckedIPAddress, self).__init__(addr) except netaddr.core.AddrFormatError as e: raise ValueError(e) if isinstance(addr, CheckedIPAddress): self.prefixlen = addr.prefixlen return if not parse_netmask and self._net: raise ValueError( "netmask and prefix length not allowed here: {}".format(addr)) if self.version not in (4, 6): raise ValueError("unsupported IP version {}".format(self.version)) if not allow_loopback and self.is_loopback(): raise ValueError("cannot use loopback IP address {}".format(addr)) if (not self.is_loopback() and self.is_reserved()) \ or self in netaddr.ip.IPV4_6TO4: raise ValueError( "cannot use IANA reserved IP address {}".format(addr)) if self.is_link_local(): raise ValueError( "cannot use link-local IP address {}".format(addr)) if not allow_multicast and self.is_multicast(): raise ValueError("cannot use multicast IP address {}".format(addr)) if match_local: if self.version == 4: family = netifaces.AF_INET elif self.version == 6: family = netifaces.AF_INET6 else: raise ValueError( "Unsupported address family ({})".format(self.version) ) iface = None for interface in netifaces.interfaces(): for ifdata in netifaces.ifaddresses(interface).get(family, []): # link-local addresses contain '%suffix' that causes parse # errors in IPNetwork ifaddr = ifdata['addr'].split(u'%', 1)[0] ifnet = netaddr.IPNetwork('{addr}/{netmask}'.format( addr=ifaddr, netmask=ifdata['netmask'] )) if ifnet == self._net or ( self._net is None and ifnet.ip == self): self._net = ifnet iface = interface break if iface is None: raise ValueError('no network interface matches the IP address ' 'and netmask {}'.format(addr)) if self._net is None: if self.version == 4: self._net = netaddr.IPNetwork( netaddr.cidr_abbrev_to_verbose(str(self))) elif self.version == 6: self._net = netaddr.IPNetwork(str(self) + '/64') self.prefixlen = self._net.prefixlen def __getstate__(self): state = { 'prefixlen': self.prefixlen, 'super_state': super(CheckedIPAddress, self).__getstate__(), } return state def __setstate__(self, state): super(CheckedIPAddress, self).__setstate__(state['super_state']) self.prefixlen = state['prefixlen'] def is_network_addr(self): return self == self._net.network def is_broadcast_addr(self): return self.version == 4 and self == self._net.broadcast def valid_ip(addr): return netaddr.valid_ipv4(addr) or netaddr.valid_ipv6(addr) def format_netloc(host, port=None): """ Format network location (host:port). If the host part is a literal IPv6 address, it must be enclosed in square brackets (RFC 2732). """ host = str(host) try: socket.inet_pton(socket.AF_INET6, host) host = '[%s]' % host except socket.error: pass if port is None: return host else: return '%s:%s' % (host, str(port)) def realm_to_suffix(realm_name): 'Convert a kerberos realm to a IPA suffix.' s = realm_name.split(".") suffix_dn = DN(*[('dc', x.lower()) for x in s]) return suffix_dn def suffix_to_realm(suffix_dn): 'Convert a IPA suffix to a kerberos realm.' assert isinstance(suffix_dn, DN) realm = '.'.join([x.value for x in suffix_dn]) return realm def template_str(txt, vars): val = string.Template(txt).substitute(vars) # eval() is a special string one can insert into a template to have the # Python interpreter evaluate the string. This is intended to allow # math to be performed in templates. pattern = re.compile('(eval\s*\(([^()]*)\))') val = pattern.sub(lambda x: str(eval(x.group(2))), val) return val def template_file(infilename, vars): """Read a file and perform template substitutions""" with open(infilename) as f: return template_str(f.read(), vars) def copy_template_file(infilename, outfilename, vars): """Copy a file, performing template substitutions""" txt = template_file(infilename, vars) with open(outfilename, 'w') as file: file.write(txt) def write_tmp_file(txt): fd = tempfile.NamedTemporaryFile('w+') fd.write(txt) fd.flush() return fd def shell_quote(string): if isinstance(string, str): return "'" + string.replace("'", "'\\''") + "'" else: return b"'" + string.replace(b"'", b"'\\''") + b"'" if six.PY3: def _log_arg(s): """Convert string or bytes to a string suitable for logging""" if isinstance(s, bytes): return s.decode(locale.getpreferredencoding(), errors='replace') else: return s else: _log_arg = str class _RunResult(collections.namedtuple('_RunResult', 'output error_output returncode')): """Result of ipautil.run""" def run(args, stdin=None, raiseonerr=True, nolog=(), env=None, capture_output=False, skip_output=False, cwd=None, runas=None, suplementary_groups=[], capture_error=False, encoding=None, redirect_output=False): """ Execute an external command. :param args: List of arguments for the command :param stdin: Optional input to the command :param raiseonerr: If True, raises an exception if the return code is not zero :param nolog: Tuple of strings that shouldn't be logged, like passwords. Each tuple consists of a string to be replaced by XXXXXXXX. Example: We have a command ['/usr/bin/setpasswd', '--password', 'Secret123', 'someuser'] and we don't want to log the password so nolog would be set to: ('Secret123',) The resulting log output would be: /usr/bin/setpasswd --password XXXXXXXX someuser If a value isn't found in the list it is silently ignored. :param env: Dictionary of environment variables passed to the command. When None, current environment is copied :param capture_output: Capture stdout :param skip_output: Redirect the output to /dev/null and do not log it :param cwd: Current working directory :param runas: Name of a user that the command should be run as. The spawned process will have both real and effective UID and GID set. :param suplementary_groups: List of group names that will be used as suplementary groups for subporcess. The option runas must be specified together with this option. :param capture_error: Capture stderr :param encoding: For Python 3, the encoding to use for output, error_output, and (if it's not bytes) stdin. If None, the current encoding according to locale is used. :param redirect_output: Redirect (error) output to standard (error) output. :return: An object with these attributes: `returncode`: The process' exit status `output` and `error_output`: captured output, as strings. Under Python 3, these are encoded with the given `encoding`. None unless `capture_output` or `capture_error`, respectively, are given `raw_output`, `raw_error_output`: captured output, as bytes. `output_log` and `error_log`: The captured output, as strings, with any unencodable characters discarded. These should only be used for logging or error messages. If skip_output is given, all output-related attributes on the result (that is, all except `returncode`) are None. For backwards compatibility, the return value can also be used as a (output, error_output, returncode) triple. """ assert isinstance(suplementary_groups, list) p_in = None p_out = None p_err = None if isinstance(nolog, six.string_types): # We expect a tuple (or list, or other iterable) of nolog strings. # Passing just a single string is bad: strings are iterable, so this # would result in every individual character of that string being # replaced by XXXXXXXX. # This is a sanity check to prevent that. raise ValueError('nolog must be a tuple of strings.') if skip_output and (capture_output or capture_error): raise ValueError('skip_output is incompatible with ' 'capture_output or capture_error') if redirect_output and (capture_output or capture_error): raise ValueError('redirect_output is incompatible with ' 'capture_output or capture_error') if skip_output and redirect_output: raise ValueError('skip_output is incompatible with redirect_output') if env is None: # copy default env env = copy.deepcopy(os.environ) env["PATH"] = "/bin:/sbin:/usr/kerberos/bin:/usr/kerberos/sbin:/usr/bin:/usr/sbin" if stdin: p_in = subprocess.PIPE if skip_output: p_out = p_err = open(os.devnull, 'w') elif redirect_output: p_out = sys.stdout p_err = sys.stderr else: p_out = subprocess.PIPE p_err = subprocess.PIPE if encoding is None: encoding = locale.getpreferredencoding() if six.PY3 and isinstance(stdin, str): stdin = stdin.encode(encoding) arg_string = nolog_replace(' '.join(_log_arg(a) for a in args), nolog) root_logger.debug('Starting external process') root_logger.debug('args=%s' % arg_string) preexec_fn = None if runas is not None: pent = pwd.getpwnam(runas) suplementary_gids = [ grp.getgrnam(group).gr_gid for group in suplementary_groups ] root_logger.debug('runas=%s (UID %d, GID %s)', runas, pent.pw_uid, pent.pw_gid) if suplementary_groups: for group, gid in zip(suplementary_groups, suplementary_gids): root_logger.debug('suplementary_group=%s (GID %d)', group, gid) preexec_fn = lambda: ( os.setgroups(suplementary_gids), os.setregid(pent.pw_gid, pent.pw_gid), os.setreuid(pent.pw_uid, pent.pw_uid), ) try: p = subprocess.Popen(args, stdin=p_in, stdout=p_out, stderr=p_err, close_fds=True, env=env, cwd=cwd, preexec_fn=preexec_fn) stdout, stderr = p.communicate(stdin) except KeyboardInterrupt: root_logger.debug('Process interrupted') p.wait() raise except: root_logger.debug('Process execution failed') raise finally: if skip_output: p_out.close() # pylint: disable=E1103 root_logger.debug('Process finished, return code=%s', p.returncode) # The command and its output may include passwords that we don't want # to log. Replace those. if skip_output or redirect_output: output_log = None error_log = None else: if six.PY3: output_log = stdout.decode(locale.getpreferredencoding(), errors='replace') else: output_log = stdout if six.PY3: error_log = stderr.decode(locale.getpreferredencoding(), errors='replace') else: error_log = stderr output_log = nolog_replace(output_log, nolog) root_logger.debug('stdout=%s' % output_log) error_log = nolog_replace(error_log, nolog) root_logger.debug('stderr=%s' % error_log) if capture_output: if six.PY2: output = stdout else: output = stdout.decode(encoding) else: output = None if capture_error: if six.PY2: error_output = stderr else: error_output = stderr.decode(encoding) else: error_output = None if p.returncode != 0 and raiseonerr: raise CalledProcessError(p.returncode, arg_string, str(output)) result = _RunResult(output, error_output, p.returncode) result.raw_output = stdout result.raw_error_output = stderr result.output_log = output_log result.error_log = error_log return result def nolog_replace(string, nolog): """Replace occurences of strings given in `nolog` with XXXXXXXX""" for value in nolog: if not isinstance(value, six.string_types): continue quoted = urllib.parse.quote(value) shquoted = shell_quote(value) for nolog_value in (shquoted, value, quoted): string = string.replace(nolog_value, 'XXXXXXXX') return string def file_exists(filename): try: mode = os.stat(filename)[stat.ST_MODE] return bool(stat.S_ISREG(mode)) except Exception: return False def dir_exists(filename): try: mode = os.stat(filename)[stat.ST_MODE] return bool(stat.S_ISDIR(mode)) except Exception: return False def install_file(fname, dest): # SELinux: use copy to keep the right context if file_exists(dest): os.rename(dest, dest + ".orig") shutil.copy(fname, dest) os.remove(fname) def backup_file(fname): if file_exists(fname): os.rename(fname, fname + ".orig") class CIDict(dict): """ Case-insensitive but case-respecting dictionary. This code is derived from python-ldap's cidict.py module, written by stroeder: http://python-ldap.sourceforge.net/ This version extends 'dict' so it works properly with TurboGears. If you extend UserDict, isinstance(foo, dict) returns false. """ def __init__(self, default=None, **kwargs): super(CIDict, self).__init__() self._keys = {} # mapping of lowercased keys to proper case if default: self.update(default) if kwargs: self.update(kwargs) def __getitem__(self, key): return super(CIDict, self).__getitem__(key.lower()) def __setitem__(self, key, value, seen_keys=None): """cidict[key] = value The ``seen_keys`` argument is used by ``update()`` to keep track of duplicate keys. It should be an initially empty set that is passed to all calls to __setitem__ that should not set duplicate keys. """ lower_key = key.lower() if seen_keys is not None: if lower_key in seen_keys: raise ValueError('Duplicate key in update: %s' % key) seen_keys.add(lower_key) self._keys[lower_key] = key return super(CIDict, self).__setitem__(lower_key, value) def __delitem__(self, key): lower_key = key.lower() del self._keys[lower_key] return super(CIDict, self).__delitem__(lower_key) def update(self, new=None, **kwargs): """Update self from dict/iterable new and kwargs Functions like ``dict.update()``. Neither ``new`` nor ``kwargs`` may contain two keys that only differ in case, as this situation would result in loss of data. """ seen = set() if new: try: keys = new.keys except AttributeError: self.update(dict(new)) else: for key in keys(): self.__setitem__(key, new[key], seen) seen = set() for key, value in kwargs.items(): self.__setitem__(key, value, seen) def __contains__(self, key): return super(CIDict, self).__contains__(key.lower()) if six.PY2: def has_key(self, key): # pylint: disable=no-member return super(CIDict, self).has_key(key.lower()) # pylint: enable=no-member def get(self, key, failobj=None): try: return self[key] except KeyError: return failobj def __iter__(self): return six.itervalues(self._keys) def keys(self): if six.PY2: return list(self.iterkeys()) else: return self.iterkeys() def items(self): if six.PY2: return list(self.iteritems()) else: return self.iteritems() def values(self): if six.PY2: return list(self.itervalues()) else: return self.itervalues() def copy(self): """Returns a shallow copy of this CIDict""" return CIDict(list(self.items())) def iteritems(self): return ((k, self[k]) for k in six.itervalues(self._keys)) def iterkeys(self): return six.itervalues(self._keys) def itervalues(self): return (v for k, v in six.iteritems(self)) def setdefault(self, key, value=None): try: return self[key] except KeyError: self[key] = value return value def pop(self, key, *args): try: value = self[key] del self[key] return value except KeyError: if len(args) == 1: return args[0] raise def popitem(self): (lower_key, value) = super(CIDict, self).popitem() key = self._keys[lower_key] del self._keys[lower_key] return (key, value) def clear(self): self._keys.clear() return super(CIDict, self).clear() def viewitems(self): raise NotImplementedError('CIDict.viewitems is not implemented') def viewkeys(self): raise NotImplementedError('CIDict.viewkeys is not implemented') def viewvvalues(self): raise NotImplementedError('CIDict.viewvvalues is not implemented') class GeneralizedTimeZone(datetime.tzinfo): """This class is a basic timezone wrapper for the offset specified in a Generalized Time. It is dst-ignorant.""" def __init__(self,offsetstr="Z"): super(GeneralizedTimeZone, self).__init__() self.name = offsetstr self.houroffset = 0 self.minoffset = 0 if offsetstr == "Z": self.houroffset = 0 self.minoffset = 0 else: if (len(offsetstr) >= 3) and re.match(r'[-+]\d\d', offsetstr): self.houroffset = int(offsetstr[0:3]) offsetstr = offsetstr[3:] if (len(offsetstr) >= 2) and re.match(r'\d\d', offsetstr): self.minoffset = int(offsetstr[0:2]) offsetstr = offsetstr[2:] if len(offsetstr) > 0: raise ValueError() if self.houroffset < 0: self.minoffset *= -1 def utcoffset(self, dt): return datetime.timedelta(hours=self.houroffset, minutes=self.minoffset) def dst(self): return datetime.timedelta(0) def tzname(self): return self.name def parse_generalized_time(timestr): """Parses are Generalized Time string (as specified in X.680), returning a datetime object. Generalized Times are stored inside the krbPasswordExpiration attribute in LDAP. This method doesn't attempt to be perfect wrt timezones. If python can't be bothered to implement them, how can we...""" if len(timestr) < 8: return None try: date = timestr[:8] time = timestr[8:] year = int(date[:4]) month = int(date[4:6]) day = int(date[6:8]) hour = min = sec = msec = 0 tzone = None if (len(time) >= 2) and re.match(r'\d', time[0]): hour = int(time[:2]) time = time[2:] if len(time) >= 2 and (time[0] == "," or time[0] == "."): hour_fraction = "." time = time[1:] while (len(time) > 0) and re.match(r'\d', time[0]): hour_fraction += time[0] time = time[1:] total_secs = int(float(hour_fraction) * 3600) min, sec = divmod(total_secs, 60) if (len(time) >= 2) and re.match(r'\d', time[0]): min = int(time[:2]) time = time[2:] if len(time) >= 2 and (time[0] == "," or time[0] == "."): min_fraction = "." time = time[1:] while (len(time) > 0) and re.match(r'\d', time[0]): min_fraction += time[0] time = time[1:] sec = int(float(min_fraction) * 60) if (len(time) >= 2) and re.match(r'\d', time[0]): sec = int(time[:2]) time = time[2:] if len(time) >= 2 and (time[0] == "," or time[0] == "."): sec_fraction = "." time = time[1:] while (len(time) > 0) and re.match(r'\d', time[0]): sec_fraction += time[0] time = time[1:] msec = int(float(sec_fraction) * 1000000) if (len(time) > 0): tzone = GeneralizedTimeZone(time) return datetime.datetime(year, month, day, hour, min, sec, msec, tzone) except ValueError: return None def ipa_generate_password(entropy_bits=256, uppercase=1, lowercase=1, digits=1, special=1, min_len=0): """ Generate token containing at least `entropy_bits` bits and with the given character restraints. :param entropy_bits: The minimal number of entropy bits attacker has to guess: 128 bits entropy: secure 256 bits of entropy: secure enough if you care about quantum computers Integer values specify minimal number of characters from given character class and length. Value None prevents given character from appearing in the token. Example: TokenGenerator(uppercase=3, lowercase=3, digits=0, special=None) At least 3 upper and 3 lower case ASCII chars, may contain digits, no special chars. """ special_chars = '!$%&()*+,-./:;<>?@[]^_{|}~' pwd_charsets = { 'uppercase': { 'chars': string.ascii_uppercase, 'entropy': math.log(len(string.ascii_uppercase), 2) }, 'lowercase': { 'chars': string.ascii_lowercase, 'entropy': math.log(len(string.ascii_lowercase), 2) }, 'digits': { 'chars': string.digits, 'entropy': math.log(len(string.digits), 2) }, 'special': { 'chars': special_chars, 'entropy': math.log(len(special_chars), 2) }, } req_classes = dict( uppercase=uppercase, lowercase=lowercase, digits=digits, special=special ) # 'all' class is used when adding entropy to too-short tokens # it contains characters from all allowed classes pwd_charsets['all'] = { 'chars': ''.join([ charclass['chars'] for charclass_name, charclass in pwd_charsets.items() if req_classes[charclass_name] is not None ]) } pwd_charsets['all']['entropy'] = math.log( len(pwd_charsets['all']['chars']), 2) rnd = random.SystemRandom() todo_entropy = entropy_bits password = u'' # Generate required character classes: # The order of generated characters is fixed to comply with check in # NSS function sftk_newPinCheck() in nss/lib/softoken/fipstokn.c. for charclass_name in ['digits', 'uppercase', 'lowercase', 'special']: charclass = pwd_charsets[charclass_name] todo_characters = req_classes[charclass_name] if todo_characters is None: continue while todo_characters > 0: password += rnd.choice(charclass['chars']) todo_entropy -= charclass['entropy'] todo_characters -= 1 # required character classes do not provide sufficient entropy # or does not fulfill minimal length constraint allchars = pwd_charsets['all'] while todo_entropy > 0 or len(password) < min_len: password += rnd.choice(allchars['chars']) todo_entropy -= allchars['entropy'] return password def user_input(prompt, default = None, allow_empty = True): if default == None: while True: try: ret = input("%s: " % prompt) if allow_empty or ret.strip(): return ret.strip() except EOFError: if allow_empty: return '' raise RuntimeError("Failed to get user input") if isinstance(default, six.string_types): while True: try: ret = input("%s [%s]: " % (prompt, default)) if not ret and (allow_empty or default): return default elif ret.strip(): return ret.strip() except EOFError: return default if isinstance(default, bool): choice = "yes" if default else "no" while True: try: ret = input("%s [%s]: " % (prompt, choice)) ret = ret.strip() if not ret: return default elif ret.lower()[0] == "y": return True elif ret.lower()[0] == "n": return False except EOFError: return default if isinstance(default, int): while True: try: ret = input("%s [%s]: " % (prompt, default)) ret = ret.strip() if not ret: return default ret = int(ret) except ValueError: pass except EOFError: return default else: return ret def host_port_open(host, port, socket_type=socket.SOCK_STREAM, socket_timeout=None, log_errors=False): """ host: either hostname or IP address; if hostname is provided, port MUST be open on ALL resolved IPs returns True is port is open, False otherwise """ port_open = True # port has to be open on ALL resolved IPs for res in socket.getaddrinfo(host, port, socket.AF_UNSPEC, socket_type): af, socktype, proto, _canonname, sa = res s = None try: s = socket.socket(af, socktype, proto) if socket_timeout is not None: s.settimeout(socket_timeout) s.connect(sa) if socket_type == socket.SOCK_DGRAM: s.send('') s.recv(512) except socket.error: port_open = False if log_errors: msg = ('Failed to connect to port %(port)d %(proto)s on ' '%(addr)s' % dict(port=port, proto=PROTOCOL_NAMES[socket_type], addr=sa[0])) # Do not log udp failures as errors (to be consistent with # the rest of the code that checks for open ports) if socket_type == socket.SOCK_DGRAM: root_logger.warning(msg) else: root_logger.error(msg) finally: if s is not None: s.close() return port_open def reverse_record_exists(ip_address): """ Checks if IP address have some reverse record somewhere. Does not care where it points. Returns True/False """ reverse = reversename.from_address(str(ip_address)) try: resolver.query(reverse, "PTR") except DNSException: # really don't care what exception, PTR is simply unresolvable return False return True def config_replace_variables(filepath, replacevars=dict(), appendvars=dict()): """ Take a key=value based configuration file, and write new version with certain values replaced or appended All (key,value) pairs from replacevars and appendvars that were not found in the configuration file, will be added there. It is responsibility of a caller to ensure that replacevars and appendvars do not overlap. It is responsibility of a caller to back up file. returns dictionary of affected keys and their previous values One have to run restore_context(filepath) afterwards or security context of the file will not be correct after modification """ pattern = re.compile(''' (^ \s* (?P