# This file is part of Checkbox.
#
# Copyright 2013, 2014 Canonical Ltd.
# Written by:
# Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
#
# Checkbox is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 3,
# as published by the Free Software Foundation.
#
# Checkbox 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 Checkbox. If not, see <http://www.gnu.org/licenses/>.
"""
:mod:`plainbox.impl.secure.qualifiers` -- Job Qualifiers
========================================================
Qualifiers are callable objects that can be used to 'match' a job definition to
some set of rules.
"""
import abc
import itertools
import logging
import os
import re
from plainbox.abc import IJobQualifier
from plainbox.impl.secure.rfc822 import FileTextSource
from plainbox.impl.secure.rfc822 import Origin
from plainbox.impl.secure.rfc822 import UnknownTextSource
_logger = logging.getLogger("plainbox.secure.qualifiers")
[docs]class SimpleQualifier(IJobQualifier):
"""
Abstract base class that implements common features of simple (non
composite) qualifiers. This allows two concrete subclasses below to
have share some code.
"""
def __init__(self, inclusive=True):
self._inclusive = inclusive
@property
[docs] def inclusive(self):
return self._inclusive
@property
[docs] def is_primitive(self):
return True
[docs] def designates(self, job):
return self.get_vote(job) == self.VOTE_INCLUDE
@abc.abstractmethod
[docs] def get_simple_match(self, job):
"""
Get a simple yes-or-no boolean answer if the given job matches the
simple aspect of this qualifier. This method should be overridden by
concrete subclasses.
"""
[docs] def get_vote(self, job):
"""
Get one of the ``VOTE_IGNORE``, ``VOTE_INCLUDE``, ``VOTE_EXCLUDE``
votes that this qualifier associated with the specified job.
:param job:
A IJobDefinition instance that is to be visited
:returns:
* ``VOTE_INCLUDE`` if the job matches the simple qualifier concept
embedded into this qualifier and this qualifier is **inclusive**.
* ``VOTE_EXCLUDE`` if the job matches the simple qualifier concept
embedded into this qualifier and this qualifier is **not
inclusive**.
* ``VOTE_IGNORE`` otherwise.
.. versionadded: 0.5
"""
if self.get_simple_match(job):
if self.inclusive:
return self.VOTE_INCLUDE
else:
return self.VOTE_EXCLUDE
else:
return self.VOTE_IGNORE
[docs] def get_primitive_qualifiers(self):
"""
Return a list of primitives that constitute this qualifier.
:returns:
A list of IJobQualifier objects that each is the smallest,
indivisible entity. Here it just returns a list of one element,
itself.
.. versionadded: 0.5
"""
return [self]
[docs]class RegExpJobQualifier(SimpleQualifier):
"""
A JobQualifier that designates jobs by matching their id to a regular
expression
"""
def __init__(self, pattern, inclusive=True):
"""
Initialize a new RegExpJobQualifier with the specified pattern.
"""
super().__init__(inclusive)
self._pattern = re.compile(pattern)
self._pattern_text = pattern
[docs] def get_simple_match(self, job):
"""
Check if the given job matches this qualifier.
This method should not be called directly, it is an implementation
detail of SimpleQualifier class.
"""
return self._pattern.match(job.id) is not None
@property
[docs] def pattern_text(self):
"""
text of the regular expression embedded in this qualifier
"""
return self._pattern_text
def __repr__(self):
return "{0}({1!r}, inclusive={2})".format(
self.__class__.__name__, self._pattern_text, self._inclusive)
[docs]class JobIdQualifier(SimpleQualifier):
"""
A JobQualifier that designates a single job with a particular id
"""
def __init__(self, id, inclusive=True):
super().__init__(inclusive)
self._id = id
[docs] def get_simple_match(self, job):
"""
Check if the given job matches this qualifier.
This method should not be called directly, it is an implementation
detail of SimpleQualifier class.
"""
return self._id == job.id
def __repr__(self):
return "{0}({1!r}, inclusive={2})".format(
self.__class__.__name__, self._id, self._inclusive)
[docs]class NonLocalJobQualifier(SimpleQualifier):
"""
A JobQualifier that designates only non local jobs
"""
def __init__(self, inclusive=True):
super().__init__(inclusive)
[docs] def get_simple_match(self, job):
"""
Check if the given job matches this qualifier.
This method should not be called directly, it is an implementation
detail of SimpleQualifier class.
"""
return job.plugin != 'local'
def __repr__(self):
return "{0}(inclusive={1})".format(
self.__class__.__name__, self._inclusive)
[docs]class IMatcher(metaclass=abc.ABCMeta):
"""
Interface for objects that perform some kind of comparison on a value
"""
@abc.abstractmethod
[docs] def match(self, value):
"""
Match (or not) specified value
:param value:
value to match
:returns:
True if it matched, False otherwise
"""
[docs]class OperatorMatcher(IMatcher):
"""
A matcher that applies a binary operator to the value
"""
def __init__(self, op, value):
self._op = op
self._value = value
[docs] def match(self, value):
return self._op(self._value, value)
def __repr__(self):
return "{0}({1!r}, {2!r})".format(
self.__class__.__name__, self._op, self._value)
[docs]class PatternMatcher(IMatcher):
"""
A matcher that compares values by regular expression pattern
"""
def __init__(self, pattern):
self._pattern_text = pattern
self._pattern = re.compile(pattern)
[docs] def match(self, value):
return self._pattern.match(value) is not None
def __repr__(self):
return "{0}({1!r})".format(
self.__class__.__name__, self._pattern_text)
[docs]class FieldQualifier(SimpleQualifier):
"""
A SimpleQualifer that uses matchers to compare particular fields
"""
def __init__(self, field, matcher, inclusive=True):
"""
Initialize a new FieldQualifier with the specified field, matcher and
inclusive flag
:param field:
Name of the JobDefinition field to use
:param matcher:
A IMatcher object
:param inclusive:
Inclusive selection flag (default: True)
"""
super().__init__(inclusive)
self._field = field
self._matcher = matcher
[docs] def get_simple_match(self, job):
"""
Check if the given job matches this qualifier.
This method should not be called directly, it is an implementation
detail of SimpleQualifier class.
"""
field_value = getattr(job, str(self._field))
return self._matcher.match(field_value)
def __repr__(self):
return "{0}({1!r}, {2!r}, inclusive={3})".format(
self.__class__.__name__, self._field, self._matcher,
self._inclusive)
[docs]class CompositeQualifier(IJobQualifier):
"""
A JobQualifier that has qualifies jobs matching any inclusive qualifiers
while not matching all of the exclusive qualifiers
"""
def __init__(self, qualifier_list):
self.qualifier_list = qualifier_list
@property
[docs] def is_primitive(self):
return False
[docs] def designates(self, job):
return self.get_vote(job) == self.VOTE_INCLUDE
[docs] def get_vote(self, job):
"""
Get one of the ``VOTE_IGNORE``, ``VOTE_INCLUDE``, ``VOTE_EXCLUDE``
votes that this qualifier associated with the specified job.
:param job:
A IJobDefinition instance that is to be visited
:returns:
* ``VOTE_INCLUDE`` if the job matches at least one qualifier voted
to select it and no qualifiers voted to deselect it.
* ``VOTE_EXCLUDE`` if at least one qualifier voted to deselect it
* ``VOTE_IGNORE`` otherwise or if the list of qualifiers is empty.
.. versionadded: 0.5
"""
if self.qualifier_list:
return min([
qualifier.get_vote(job)
for qualifier in self.qualifier_list])
else:
return self.VOTE_IGNORE
[docs] def get_primitive_qualifiers(self):
return get_flat_primitive_qualifier_list(self.qualifier_list)
# NOTE: using CompositeQualifier seems strange but it's a tested proven
# component so all we have to ensure is that we read the whitelist files
# correctly.
[docs]class WhiteList(CompositeQualifier):
"""
A qualifier that understands checkbox whitelist files.
A whitelist file is a plain text, line oriented file. Each line represents
a regular expression pattern that can be matched against the id of a job.
The file can contain simple shell-style comments that begin with the pound
or hash key (#). Those are ignored. Comments can span both a fraction of a
line as well as the whole line.
For historical reasons each pattern has an implicit '^' and '$' prepended
and appended (respectively) to the actual pattern specified in the file.
"""
def __init__(self, pattern_list, name=None, origin=None,
implicit_namespace=None):
"""
Initialize a WhiteList object with the specified list of patterns.
The patterns must be already mangled with '^' and '$'.
"""
self._name = name
self._origin = origin
self._implicit_namespace = implicit_namespace
if implicit_namespace is not None:
# If we have an implicit namespace then transform all the patterns
# without the namespace operator ('::')
namespace_pattern = implicit_namespace.replace('.', '\\.')
def transform_pattern(maybe_partial_id_pattern):
if "::" not in maybe_partial_id_pattern:
return "^{}::{}$".format(
namespace_pattern, maybe_partial_id_pattern[1:-1])
else:
return maybe_partial_id_pattern
qualifier_list = [
RegExpJobQualifier(transform_pattern(pattern), inclusive=True)
for pattern in pattern_list]
else:
# Otherwise just use the patterns directly
qualifier_list = [
RegExpJobQualifier(pattern, inclusive=True)
for pattern in pattern_list]
super().__init__(qualifier_list)
def __repr__(self):
return "<{} name:{!r}>".format(self.__class__.__name__, self.name)
@property
def name(self):
"""
name of this WhiteList (might be None)
"""
return self._name
@name.setter
[docs] def name(self, value):
"""
set a new name for a WhiteList
"""
self._name = value
@property
[docs] def origin(self):
"""
origin object associated with this WhiteList (might be None)
"""
return self._origin
@property
[docs] def implicit_namespace(self):
"""
namespace used to qualify patterns without explicit namespace
"""
return self._implicit_namespace
@classmethod
[docs] def from_file(cls, pathname, implicit_namespace=None):
"""
Load and initialize the WhiteList object from the specified file.
:param pathname:
file to load
:param implicit_namespace:
(optional) implicit namespace for jobs that are using partial
identifiers (all jobs)
:returns:
a fresh WhiteList object
"""
pattern_list, max_lineno = cls._load_patterns(pathname)
name = os.path.splitext(os.path.basename(pathname))[0]
origin = Origin(FileTextSource(pathname), 1, max_lineno)
return cls(pattern_list, name, origin, implicit_namespace)
@classmethod
[docs] def from_string(cls, text, *, filename=None, name=None, origin=None,
implicit_namespace=None):
"""
Load and initialize the WhiteList object from the specified string.
:param text:
full text of the whitelist
:param filename:
(optional, keyword-only) filename from which text was read from.
This simulates a call to :meth:`from_file()` which properly
computes the name and origin of the whitelist.
:param name:
(optional) name of the whitelist, only used if filename is not
specified.
:param origin:
(optional) origin of the whitelist, only used if a filename is not
specified. If omitted a default origin value will be constructed
out of UnknownTextSource instance
:param implicit_namespace:
(optional) implicit namespace for jobs that are using partial
identifiers (all jobs)
:returns:
a fresh WhiteList object
The optional filename or a pair of name and origin arguments may be
provided in order to have additional meta-data. This is typically
needed when the :meth:`from_file()` method cannot be used as the caller
already has the full text of the intended file available.
"""
_logger.debug("Loaded whitelist from %r", filename)
pattern_list, max_lineno = cls._parse_patterns(text)
# generate name and origin if filename is provided
if filename is not None:
name = WhiteList.name_from_filename(filename)
origin = Origin(FileTextSource(filename), 1, max_lineno)
else:
# otherwise generate origin if it's not specified
if origin is None:
origin = Origin(UnknownTextSource(), 1, max_lineno)
return cls(pattern_list, name, origin, implicit_namespace)
@classmethod
[docs] def name_from_filename(cls, filename):
"""
Compute the name of a whitelist based on the name
of the file it is stored in.
"""
return os.path.splitext(os.path.basename(filename))[0]
@classmethod
def _parse_patterns(cls, text):
"""
Load whitelist patterns from the specified text
:param text:
string of text, including newlines, to parse
:returns:
(pattern_list, lineno) where lineno is the final line number
(1-based) and pattern_list is a list of regular expression strings
parsed from the whitelist.
"""
pattern_list = []
lineno = 0
# Load the file
for lineno, line in enumerate(text.splitlines(), 1):
# Strip shell-style comments if there are any
try:
index = line.index("#")
except ValueError:
pass
else:
line = line[:index]
# Strip whitespace
line = line.strip()
# Skip empty lines (especially after stripping comments)
if line == "":
continue
# Surround the pattern with ^ and $
# so that it wont just match a part of the job name.
regexp_pattern = r"^{pattern}$".format(pattern=line)
# Accumulate patterns into the list
pattern_list.append(regexp_pattern)
return pattern_list, lineno
@classmethod
def _load_patterns(cls, pathname):
"""
Load whitelist patterns from the specified file
:param pathname:
pathname of the file to load and parse
:returns:
(pattern_list, lineno) where lineno is the final line number
(1-based) and pattern_list is a list of regular expression strings
parsed from the whitelist.
"""
with open(pathname, "rt", encoding="UTF-8") as stream:
return cls._parse_patterns(stream.read())
[docs]def get_flat_primitive_qualifier_list(qualifier_list):
return list(itertools.chain(*[
qual.get_primitive_qualifiers()
for qual in qualifier_list]))
[docs]def select_jobs(job_list, qualifier_list):
"""
Select desired jobs.
:param job_list:
A list of JobDefinition objects
:param qualifier_list:
A list of IJobQualifier objects.
:returns:
A sub-list of JobDefinition objects, selected from job_list.
"""
# Flatten the qualifier list, so that we can see the fine structure of
# composite objects, such as whitelists.
flat_qualifier_list = get_flat_primitive_qualifier_list(qualifier_list)
# Short-circuit if there are no jobs to select. Min is used later and this
# will allow us to assume that the matrix is not empty.
if not flat_qualifier_list:
return []
# Vote matrix, encodes the vote cast by a particular qualifier for a
# particular job. Visually it's a two-dimensional array like this:
#
# ^
# q |
# u | X
# a |
# l | ........
# i |
# f | .
# i | .
# e | .
# r |
# ------------------->
# job
#
# The vertical axis represents qualifiers from the flattened qualifier
# list. The horizontal axis represents jobs from job list. Dots represent
# inclusion, X represents exclusion.
#
# The result of the select_job() function is a list of jobs that have at
# least one inclusion and no exclusions. The resulting list is ordered by
# increasing qualifier index.
#
# The algorithm implemented below is composed of two steps.
#
# The first step iterates over the vote matrix (row-major, meaning that we
# visit all columns for each visit of one row) and constructs two
# structures: a set of jobs that got VOTE_INCLUDE and a list of those jobs,
# in the order of discovery. All VOTE_EXCLUDE votes are collected in
# another set.
#
# The second step filters-out all items from the excluded job set from the
# selected job list. For extra efficiency the algorithm operates on
# integers representing the index of a particular job in job_list.
#
# The final complexity is O(N x M) + O(M), where N is the number of
# qualifiers (flattened) and M is the number of jobs. The algorithm assumes
# that set lookup is a O(1) operation which is true enough for python.
#
# A possible optimization would differentiate qualifiers that may select
# more than one job and fall-back to the current implementation while
# short-circuiting qualifiers that may select at most one job with a
# separate set lookup. That would make the algorithm "mostly" linear in the
# common case.
#
# As a separate feature, we might return a list of qualifiers that never
# matched anything. That may be helpful for debugging.
included_list = []
included_set = set()
excluded_set = set()
for qualifier in flat_qualifier_list:
for j_index, job in enumerate(job_list):
vote = qualifier.get_vote(job)
if vote == IJobQualifier.VOTE_INCLUDE:
if j_index in included_set:
continue
included_set.add(j_index)
included_list.append(j_index)
elif vote == IJobQualifier.VOTE_EXCLUDE:
excluded_set.add(j_index)
elif vote == IJobQualifier.VOTE_IGNORE:
pass
return [job_list[index] for index in included_list
if index not in excluded_set]