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Editing: access.py
# Authors: Karl MacMillan <kmacmillan@mentalrootkit.com> # # Copyright (C) 2006 Red Hat # 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; version 2 only # # 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, write to the Free Software # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA # """ Classes representing basic access. SELinux - at the most basic level - represents access as the 4-tuple subject (type or context), target (type or context), object class, permission. The policy language elaborates this basic access to facilitate more concise rules (e.g., allow rules can have multiple source or target types - see refpolicy for more information). This module has objects for representing the most basic access (AccessVector) and sets of that access (AccessVectorSet). These objects are used in Madison in a variety of ways, but they are the fundamental representation of access. """ from . import refpolicy from . import util from selinux import audit2why def is_idparam(id): """Determine if an id is a parameter in the form $N, where N is an integer. Returns: True if the id is a parameter False if the id is not a parameter """ if len(id) > 1 and id[0] == '$': try: int(id[1:]) except ValueError: return False return True else: return False class AccessVector(util.Comparison): """ An access vector is the basic unit of access in SELinux. Access vectors are the most basic representation of access within SELinux. It represents the access a source type has to a target type in terms of an object class and a set of permissions. Access vectors are distinct from AVRules in that they can only store a single source type, target type, and object class. The simplicity of AccessVectors makes them useful for storing access in a form that is easy to search and compare. The source, target, and object are stored as string. No checking done to verify that the strings are valid SELinux identifiers. Identifiers in the form $N (where N is an integer) are reserved as interface parameters and are treated as wild cards in many circumstances. Properties: .src_type - The source type allowed access. [String or None] .tgt_type - The target type to which access is allowed. [String or None] .obj_class - The object class to which access is allowed. [String or None] .perms - The permissions allowed to the object class. [IdSet] .audit_msgs - The audit messages that generated this access vector [List of strings] .xperms - Extended permissions attached to the AV. [Dictionary {operation: xperm set}] """ def __init__(self, init_list=None): if init_list: self.from_list(init_list) else: self.src_type = None self.tgt_type = None self.obj_class = None self.perms = refpolicy.IdSet() self.audit_msgs = [] self.type = audit2why.TERULE self.data = [] self.xperms = {} # when implementing __eq__ also __hash__ is needed on py2 # if object is muttable __hash__ should be None self.__hash__ = None # The direction of the information flow represented by this # access vector - used for matching self.info_flow_dir = None def from_list(self, list): """Initialize an access vector from a list. Initialize an access vector from a list treating the list as positional arguments - i.e., 0 = src_type, 1 = tgt_type, etc. All of the list elements 3 and greater are treated as perms. For example, the list ['foo_t', 'bar_t', 'file', 'read', 'write'] would create an access vector list with the source type 'foo_t', target type 'bar_t', object class 'file', and permissions 'read' and 'write'. This format is useful for very simple storage to strings or disc (see to_list) and for initializing access vectors. """ if len(list) < 4: raise ValueError("List must contain at least four elements %s" % str(list)) self.src_type = list[0] self.tgt_type = list[1] self.obj_class = list[2] self.perms = refpolicy.IdSet(list[3:]) def to_list(self): """ Convert an access vector to a list. Convert an access vector to a list treating the list as positional values. See from_list for more information on how an access vector is represented in a list. """ l = [self.src_type, self.tgt_type, self.obj_class] l.extend(sorted(self.perms)) return l def merge(self, av): """Add permissions and extended permissions from AV""" self.perms.update(av.perms) for op in av.xperms: if op not in self.xperms: self.xperms[op] = refpolicy.XpermSet() self.xperms[op].extend(av.xperms[op]) def __str__(self): return self.to_string() def to_string(self): return "allow %s %s:%s %s;" % (self.src_type, self.tgt_type, self.obj_class, self.perms.to_space_str()) def _compare(self, other, method): try: x = list(self.perms) a = (self.src_type, self.tgt_type, self.obj_class, x) y = list(other.perms) x.sort() y.sort() b = (other.src_type, other.tgt_type, other.obj_class, y) return method(a, b) except (AttributeError, TypeError): # trying to compare to foreign type return NotImplemented def avrule_to_access_vectors(avrule): """Convert an avrule into a list of access vectors. AccessVectors and AVRules are similarly, but differ in that an AVRule can more than one source type, target type, and object class. This function expands a single avrule into a list of one or more AccessVectors representing the access defined in the AVRule. """ if isinstance(avrule, AccessVector): return [avrule] a = [] for src_type in avrule.src_types: for tgt_type in avrule.tgt_types: for obj_class in avrule.obj_classes: access = AccessVector() access.src_type = src_type access.tgt_type = tgt_type access.obj_class = obj_class access.perms = avrule.perms.copy() a.append(access) return a class AccessVectorSet: """A non-overlapping set of access vectors. An AccessVectorSet is designed to store one or more access vectors that are non-overlapping. Access can be added to the set incrementally and access vectors will be added or merged as necessary. For example, adding the following access vectors using add_av: allow $1 etc_t : read; allow $1 etc_t : write; allow $1 var_log_t : read; Would result in an access vector set with the access vectors: allow $1 etc_t : { read write}; allow $1 var_log_t : read; """ def __init__(self): """Initialize an access vector set. """ self.src = {} # The information flow direction of this access vector # set - see objectmodel.py for more information. This # stored here to speed up searching - see matching.py. self.info_dir = None def __iter__(self): """Iterate over all of the unique access vectors in the set.""" for tgts in self.src.values(): for objs in tgts.values(): for av in objs.values(): yield av def __len__(self): """Return the number of unique access vectors in the set. Because of the internal representation of the access vector set, __len__ is not a constant time operation. Worst case is O(N) where N is the number of unique access vectors, but the common case is probably better. """ l = 0 for tgts in self.src.values(): for objs in tgts.values(): l += len(objs) return l def to_list(self): """Return the unique access vectors in the set as a list. The format of the returned list is a set of nested lists, each access vector represented by a list. This format is designed to be simply serializable to a file. For example, consider an access vector set with the following access vectors: allow $1 user_t : file read; allow $1 etc_t : file { read write}; to_list would return the following: [[$1, user_t, file, read] [$1, etc_t, file, read, write]] See AccessVector.to_list for more information. """ l = [] for av in self: l.append(av.to_list()) return l def from_list(self, l): """Add access vectors stored in a list. See to list for more information on the list format that this method accepts. This will add all of the access from the list. Any existing access vectors in the set will be retained. """ for av in l: self.add_av(AccessVector(av)) def add(self, src_type, tgt_type, obj_class, perms, audit_msg=None, avc_type=audit2why.TERULE, data=[]): """Add an access vector to the set. """ av = AccessVector() av.src_type = src_type av.tgt_type = tgt_type av.obj_class = obj_class av.perms = perms av.data = data av.type = avc_type self.add_av(av, audit_msg) def add_av(self, av, audit_msg=None): """Add an access vector to the set.""" tgt = self.src.setdefault(av.src_type, { }) cls = tgt.setdefault(av.tgt_type, { }) if (av.obj_class, av.type) in cls: cls[av.obj_class, av.type].merge(av) else: cls[av.obj_class, av.type] = av if audit_msg: cls[av.obj_class, av.type].audit_msgs.append(audit_msg) def avs_extract_types(avs): types = refpolicy.IdSet() for av in avs: types.add(av.src_type) types.add(av.tgt_type) return types def avs_extract_obj_perms(avs): perms = { } for av in avs: if av.obj_class in perms: s = perms[av.obj_class] else: s = refpolicy.IdSet() perms[av.obj_class] = s s.update(av.perms) return perms class RoleTypeSet: """A non-overlapping set of role type statements. This class allows the incremental addition of role type statements and maintains a non-overlapping list of statements. """ def __init__(self): """Initialize an access vector set.""" self.role_types = {} def __iter__(self): """Iterate over all of the unique role allows statements in the set.""" for role_type in self.role_types.values(): yield role_type def __len__(self): """Return the unique number of role allow statements.""" return len(self.role_types.keys()) def add(self, role, type): if role in self.role_types: role_type = self.role_types[role] else: role_type = refpolicy.RoleType() role_type.role = role self.role_types[role] = role_type role_type.types.add(type)
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