/usr/lib/python2.7/dist-packages/oslo_policy/_parser.py is in python-oslo.policy 1.33.1-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 | # -*- coding: utf-8 -*-
#
# Copyright (c) 2015 OpenStack Foundation.
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import logging
import re
import six
from oslo_policy import _checks
LOG = logging.getLogger(__name__)
def reducer(*tokens):
"""Decorator for reduction methods.
Arguments are a sequence of tokens, in order, which should trigger running
this reduction method.
"""
def decorator(func):
# Make sure we have a list of reducer sequences
if not hasattr(func, 'reducers'):
func.reducers = []
# Add the tokens to the list of reducer sequences
func.reducers.append(list(tokens))
return func
return decorator
class ParseStateMeta(type):
"""Metaclass for the :class:`.ParseState` class.
Facilitates identifying reduction methods.
"""
def __new__(mcs, name, bases, cls_dict):
"""Create the class.
Injects the 'reducers' list, a list of tuples matching token sequences
to the names of the corresponding reduction methods.
"""
reducers = []
for key, value in cls_dict.items():
if not hasattr(value, 'reducers'):
continue
for reduction in value.reducers:
reducers.append((reduction, key))
cls_dict['reducers'] = reducers
return super(ParseStateMeta, mcs).__new__(mcs, name, bases, cls_dict)
@six.add_metaclass(ParseStateMeta)
class ParseState(object):
"""Implement the core of parsing the policy language.
Uses a greedy reduction algorithm to reduce a sequence of tokens into
a single terminal, the value of which will be the root of the
:class:`Check` tree.
.. note::
Error reporting is rather lacking. The best we can get with this
parser formulation is an overall "parse failed" error. Fortunately, the
policy language is simple enough that this shouldn't be that big a
problem.
"""
def __init__(self):
"""Initialize the ParseState."""
self.tokens = []
self.values = []
def reduce(self):
"""Perform a greedy reduction of the token stream.
If a reducer method matches, it will be executed, then the
:meth:`reduce` method will be called recursively to search for any more
possible reductions.
"""
for reduction, methname in self.reducers:
if (len(self.tokens) >= len(reduction) and
self.tokens[-len(reduction):] == reduction):
# Get the reduction method
meth = getattr(self, methname)
# Reduce the token stream
results = meth(*self.values[-len(reduction):])
# Update the tokens and values
self.tokens[-len(reduction):] = [r[0] for r in results]
self.values[-len(reduction):] = [r[1] for r in results]
# Check for any more reductions
return self.reduce()
def shift(self, tok, value):
"""Adds one more token to the state.
Calls :meth:`reduce`.
"""
self.tokens.append(tok)
self.values.append(value)
# Do a greedy reduce...
self.reduce()
@property
def result(self):
"""Obtain the final result of the parse.
:raises ValueError: If the parse failed to reduce to a single result.
"""
if len(self.values) != 1:
raise ValueError('Could not parse rule')
return self.values[0]
@reducer('(', 'check', ')')
@reducer('(', 'and_expr', ')')
@reducer('(', 'or_expr', ')')
def _wrap_check(self, _p1, check, _p2):
"""Turn parenthesized expressions into a 'check' token."""
return [('check', check)]
@reducer('check', 'and', 'check')
def _make_and_expr(self, check1, _and, check2):
"""Create an 'and_expr'.
Join two checks by the 'and' operator.
"""
return [('and_expr', _checks.AndCheck([check1, check2]))]
@reducer('or_expr', 'and', 'check')
def _mix_or_and_expr(self, or_expr, _and, check):
"""Modify the case 'A or B and C'"""
or_expr, check1 = or_expr.pop_check()
if isinstance(check1, _checks.AndCheck):
and_expr = check1
and_expr.add_check(check)
else:
and_expr = _checks.AndCheck([check1, check])
return [('or_expr', or_expr.add_check(and_expr))]
@reducer('and_expr', 'and', 'check')
def _extend_and_expr(self, and_expr, _and, check):
"""Extend an 'and_expr' by adding one more check."""
return [('and_expr', and_expr.add_check(check))]
@reducer('check', 'or', 'check')
@reducer('and_expr', 'or', 'check')
def _make_or_expr(self, check1, _or, check2):
"""Create an 'or_expr'.
Join two checks by the 'or' operator.
"""
return [('or_expr', _checks.OrCheck([check1, check2]))]
@reducer('or_expr', 'or', 'check')
def _extend_or_expr(self, or_expr, _or, check):
"""Extend an 'or_expr' by adding one more check."""
return [('or_expr', or_expr.add_check(check))]
@reducer('not', 'check')
def _make_not_expr(self, _not, check):
"""Invert the result of another check."""
return [('check', _checks.NotCheck(check))]
def _parse_check(rule):
"""Parse a single base check rule into an appropriate Check object."""
# Handle the special checks
if rule == '!':
return _checks.FalseCheck()
elif rule == '@':
return _checks.TrueCheck()
try:
kind, match = rule.split(':', 1)
except Exception:
LOG.exception('Failed to understand rule %s', rule)
# If the rule is invalid, we'll fail closed
return _checks.FalseCheck()
# Find what implements the check
extension_checks = _checks.get_extensions()
if kind in extension_checks:
return extension_checks[kind](kind, match)
elif kind in _checks.registered_checks:
return _checks.registered_checks[kind](kind, match)
elif None in _checks.registered_checks:
return _checks.registered_checks[None](kind, match)
else:
LOG.error('No handler for matches of kind %s', kind)
return _checks.FalseCheck()
def _parse_list_rule(rule):
"""Translates the old list-of-lists syntax into a tree of Check objects.
Provided for backwards compatibility.
"""
# Empty rule defaults to True
if not rule:
return _checks.TrueCheck()
# Outer list is joined by "or"; inner list by "and"
or_list = []
for inner_rule in rule:
# Skip empty inner lists
if not inner_rule:
continue
# Handle bare strings
if isinstance(inner_rule, six.string_types):
inner_rule = [inner_rule]
# Parse the inner rules into Check objects
and_list = [_parse_check(r) for r in inner_rule]
# Append the appropriate check to the or_list
if len(and_list) == 1:
or_list.append(and_list[0])
else:
or_list.append(_checks.AndCheck(and_list))
# If we have only one check, omit the "or"
if not or_list:
return _checks.FalseCheck()
elif len(or_list) == 1:
return or_list[0]
return _checks.OrCheck(or_list)
# Used for tokenizing the policy language
_tokenize_re = re.compile(r'\s+')
def _parse_tokenize(rule):
"""Tokenizer for the policy language.
Most of the single-character tokens are specified in the
_tokenize_re; however, parentheses need to be handled specially,
because they can appear inside a check string. Thankfully, those
parentheses that appear inside a check string can never occur at
the very beginning or end ("%(variable)s" is the correct syntax).
"""
for tok in _tokenize_re.split(rule):
# Skip empty tokens
if not tok or tok.isspace():
continue
# Handle leading parens on the token
clean = tok.lstrip('(')
for i in range(len(tok) - len(clean)):
yield '(', '('
# If it was only parentheses, continue
if not clean:
continue
else:
tok = clean
# Handle trailing parens on the token
clean = tok.rstrip(')')
trail = len(tok) - len(clean)
# Yield the cleaned token
lowered = clean.lower()
if lowered in ('and', 'or', 'not'):
# Special tokens
yield lowered, clean
elif clean:
# Not a special token, but not composed solely of ')'
if len(tok) >= 2 and ((tok[0], tok[-1]) in
[('"', '"'), ("'", "'")]):
# It's a quoted string
yield 'string', tok[1:-1]
else:
yield 'check', _parse_check(clean)
# Yield the trailing parens
for i in range(trail):
yield ')', ')'
def _parse_text_rule(rule):
"""Parses policy to the tree.
Translates a policy written in the policy language into a tree of
Check objects.
"""
# Empty rule means always accept
if not rule:
return _checks.TrueCheck()
# Parse the token stream
state = ParseState()
for tok, value in _parse_tokenize(rule):
state.shift(tok, value)
try:
return state.result
except ValueError:
# Couldn't parse the rule
LOG.exception('Failed to understand rule %s', rule)
# Fail closed
return _checks.FalseCheck()
def parse_rule(rule):
"""Parses a policy rule into a tree of :class:`.Check` objects."""
# If the rule is a string, it's in the policy language
if isinstance(rule, six.string_types):
return _parse_text_rule(rule)
return _parse_list_rule(rule)
|