Jeff Vander Stoep | 74e4f93 | 2016-02-08 15:27:10 -0800 | [diff] [blame^] | 1 | # Authors: Karl MacMillan <kmacmillan@mentalrootkit.com> |
| 2 | # |
| 3 | # Copyright (C) 2006 Red Hat |
| 4 | # see file 'COPYING' for use and warranty information |
| 5 | # |
| 6 | # This program is free software; you can redistribute it and/or |
| 7 | # modify it under the terms of the GNU General Public License as |
| 8 | # published by the Free Software Foundation; version 2 only |
| 9 | # |
| 10 | # This program is distributed in the hope that it will be useful, |
| 11 | # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | # GNU General Public License for more details. |
| 14 | # |
| 15 | # You should have received a copy of the GNU General Public License |
| 16 | # along with this program; if not, write to the Free Software |
| 17 | # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 18 | # |
| 19 | |
| 20 | """ |
| 21 | Classes representing basic access. |
| 22 | |
| 23 | SELinux - at the most basic level - represents access as |
| 24 | the 4-tuple subject (type or context), target (type or context), |
| 25 | object class, permission. The policy language elaborates this basic |
| 26 | access to faciliate more concise rules (e.g., allow rules can have multiple |
| 27 | source or target types - see refpolicy for more information). |
| 28 | |
| 29 | This module has objects for representing the most basic access (AccessVector) |
| 30 | and sets of that access (AccessVectorSet). These objects are used in Madison |
| 31 | in a variety of ways, but they are the fundamental representation of access. |
| 32 | """ |
| 33 | |
| 34 | from . import refpolicy |
| 35 | from . import util |
| 36 | |
| 37 | from selinux import audit2why |
| 38 | |
| 39 | def is_idparam(id): |
| 40 | """Determine if an id is a paramater in the form $N, where N is |
| 41 | an integer. |
| 42 | |
| 43 | Returns: |
| 44 | True if the id is a paramater |
| 45 | False if the id is not a paramater |
| 46 | """ |
| 47 | if len(id) > 1 and id[0] == '$': |
| 48 | try: |
| 49 | int(id[1:]) |
| 50 | except ValueError: |
| 51 | return False |
| 52 | return True |
| 53 | else: |
| 54 | return False |
| 55 | |
| 56 | class AccessVector(util.Comparison): |
| 57 | """ |
| 58 | An access vector is the basic unit of access in SELinux. |
| 59 | |
| 60 | Access vectors are the most basic representation of access within |
| 61 | SELinux. It represents the access a source type has to a target |
| 62 | type in terms of an object class and a set of permissions. |
| 63 | |
| 64 | Access vectors are distinct from AVRules in that they can only |
| 65 | store a single source type, target type, and object class. The |
| 66 | simplicity of AccessVectors makes them useful for storing access |
| 67 | in a form that is easy to search and compare. |
| 68 | |
| 69 | The source, target, and object are stored as string. No checking |
| 70 | done to verify that the strings are valid SELinux identifiers. |
| 71 | Identifiers in the form $N (where N is an integer) are reserved as |
| 72 | interface parameters and are treated as wild cards in many |
| 73 | circumstances. |
| 74 | |
| 75 | Properties: |
| 76 | .src_type - The source type allowed access. [String or None] |
| 77 | .tgt_type - The target type to which access is allowed. [String or None] |
| 78 | .obj_class - The object class to which access is allowed. [String or None] |
| 79 | .perms - The permissions allowed to the object class. [IdSet] |
| 80 | .audit_msgs - The audit messages that generated this access vector [List of strings] |
| 81 | """ |
| 82 | def __init__(self, init_list=None): |
| 83 | if init_list: |
| 84 | self.from_list(init_list) |
| 85 | else: |
| 86 | self.src_type = None |
| 87 | self.tgt_type = None |
| 88 | self.obj_class = None |
| 89 | self.perms = refpolicy.IdSet() |
| 90 | self.audit_msgs = [] |
| 91 | self.type = audit2why.TERULE |
| 92 | self.data = [] |
| 93 | # when implementing __eq__ also __hash__ is needed on py2 |
| 94 | # if object is muttable __hash__ should be None |
| 95 | self.__hash__ = None |
| 96 | |
| 97 | # The direction of the information flow represented by this |
| 98 | # access vector - used for matching |
| 99 | self.info_flow_dir = None |
| 100 | |
| 101 | def from_list(self, list): |
| 102 | """Initialize an access vector from a list. |
| 103 | |
| 104 | Initialize an access vector from a list treating the list as |
| 105 | positional arguments - i.e., 0 = src_type, 1 = tgt_type, etc. |
| 106 | All of the list elements 3 and greater are treated as perms. |
| 107 | For example, the list ['foo_t', 'bar_t', 'file', 'read', 'write'] |
| 108 | would create an access vector list with the source type 'foo_t', |
| 109 | target type 'bar_t', object class 'file', and permissions 'read' |
| 110 | and 'write'. |
| 111 | |
| 112 | This format is useful for very simple storage to strings or disc |
| 113 | (see to_list) and for initializing access vectors. |
| 114 | """ |
| 115 | if len(list) < 4: |
| 116 | raise ValueError("List must contain at least four elements %s" % str(list)) |
| 117 | self.src_type = list[0] |
| 118 | self.tgt_type = list[1] |
| 119 | self.obj_class = list[2] |
| 120 | self.perms = refpolicy.IdSet(list[3:]) |
| 121 | |
| 122 | def to_list(self): |
| 123 | """ |
| 124 | Convert an access vector to a list. |
| 125 | |
| 126 | Convert an access vector to a list treating the list as positional |
| 127 | values. See from_list for more information on how an access vector |
| 128 | is represented in a list. |
| 129 | """ |
| 130 | l = [self.src_type, self.tgt_type, self.obj_class] |
| 131 | l.extend(sorted(self.perms)) |
| 132 | return l |
| 133 | |
| 134 | def __str__(self): |
| 135 | return self.to_string() |
| 136 | |
| 137 | def to_string(self): |
| 138 | return "allow %s %s:%s %s;" % (self.src_type, self.tgt_type, |
| 139 | self.obj_class, self.perms.to_space_str()) |
| 140 | |
| 141 | def _compare(self, other, method): |
| 142 | try: |
| 143 | x = list(self.perms) |
| 144 | a = (self.src_type, self.tgt_type, self.obj_class, x) |
| 145 | y = list(other.perms) |
| 146 | x.sort() |
| 147 | y.sort() |
| 148 | b = (other.src_type, other.tgt_type, other.obj_class, y) |
| 149 | return method(a, b) |
| 150 | except (AttributeError, TypeError): |
| 151 | # trying to compare to foreign type |
| 152 | return NotImplemented |
| 153 | |
| 154 | |
| 155 | def avrule_to_access_vectors(avrule): |
| 156 | """Convert an avrule into a list of access vectors. |
| 157 | |
| 158 | AccessVectors and AVRules are similary, but differ in that |
| 159 | an AVRule can more than one source type, target type, and |
| 160 | object class. This function expands a single avrule into a |
| 161 | list of one or more AccessVectors representing the access |
| 162 | defined in the AVRule. |
| 163 | |
| 164 | |
| 165 | """ |
| 166 | if isinstance(avrule, AccessVector): |
| 167 | return [avrule] |
| 168 | a = [] |
| 169 | for src_type in avrule.src_types: |
| 170 | for tgt_type in avrule.tgt_types: |
| 171 | for obj_class in avrule.obj_classes: |
| 172 | access = AccessVector() |
| 173 | access.src_type = src_type |
| 174 | access.tgt_type = tgt_type |
| 175 | access.obj_class = obj_class |
| 176 | access.perms = avrule.perms.copy() |
| 177 | a.append(access) |
| 178 | return a |
| 179 | |
| 180 | class AccessVectorSet: |
| 181 | """A non-overlapping set of access vectors. |
| 182 | |
| 183 | An AccessVectorSet is designed to store one or more access vectors |
| 184 | that are non-overlapping. Access can be added to the set |
| 185 | incrementally and access vectors will be added or merged as |
| 186 | necessary. For example, adding the following access vectors using |
| 187 | add_av: |
| 188 | allow $1 etc_t : read; |
| 189 | allow $1 etc_t : write; |
| 190 | allow $1 var_log_t : read; |
| 191 | Would result in an access vector set with the access vectors: |
| 192 | allow $1 etc_t : { read write}; |
| 193 | allow $1 var_log_t : read; |
| 194 | """ |
| 195 | def __init__(self): |
| 196 | """Initialize an access vector set. |
| 197 | """ |
| 198 | self.src = {} |
| 199 | # The information flow direction of this access vector |
| 200 | # set - see objectmodel.py for more information. This |
| 201 | # stored here to speed up searching - see matching.py. |
| 202 | self.info_dir = None |
| 203 | |
| 204 | def __iter__(self): |
| 205 | """Iterate over all of the unique access vectors in the set.""" |
| 206 | for tgts in self.src.values(): |
| 207 | for objs in tgts.values(): |
| 208 | for av in objs.values(): |
| 209 | yield av |
| 210 | |
| 211 | def __len__(self): |
| 212 | """Return the number of unique access vectors in the set. |
| 213 | |
| 214 | Because of the inernal representation of the access vector set, |
| 215 | __len__ is not a constant time operation. Worst case is O(N) |
| 216 | where N is the number of unique access vectors, but the common |
| 217 | case is probably better. |
| 218 | """ |
| 219 | l = 0 |
| 220 | for tgts in self.src.values(): |
| 221 | for objs in tgts.values(): |
| 222 | l += len(objs) |
| 223 | return l |
| 224 | |
| 225 | def to_list(self): |
| 226 | """Return the unique access vectors in the set as a list. |
| 227 | |
| 228 | The format of the returned list is a set of nested lists, |
| 229 | each access vector represented by a list. This format is |
| 230 | designed to be simply serializable to a file. |
| 231 | |
| 232 | For example, consider an access vector set with the following |
| 233 | access vectors: |
| 234 | allow $1 user_t : file read; |
| 235 | allow $1 etc_t : file { read write}; |
| 236 | to_list would return the following: |
| 237 | [[$1, user_t, file, read] |
| 238 | [$1, etc_t, file, read, write]] |
| 239 | |
| 240 | See AccessVector.to_list for more information. |
| 241 | """ |
| 242 | l = [] |
| 243 | for av in self: |
| 244 | l.append(av.to_list()) |
| 245 | |
| 246 | return l |
| 247 | |
| 248 | def from_list(self, l): |
| 249 | """Add access vectors stored in a list. |
| 250 | |
| 251 | See to list for more information on the list format that this |
| 252 | method accepts. |
| 253 | |
| 254 | This will add all of the access from the list. Any existing |
| 255 | access vectors in the set will be retained. |
| 256 | """ |
| 257 | for av in l: |
| 258 | self.add_av(AccessVector(av)) |
| 259 | |
| 260 | def add(self, src_type, tgt_type, obj_class, perms, audit_msg=None, avc_type=audit2why.TERULE, data=[]): |
| 261 | """Add an access vector to the set. |
| 262 | """ |
| 263 | tgt = self.src.setdefault(src_type, { }) |
| 264 | cls = tgt.setdefault(tgt_type, { }) |
| 265 | |
| 266 | if (obj_class, avc_type) in cls: |
| 267 | access = cls[obj_class, avc_type] |
| 268 | else: |
| 269 | access = AccessVector() |
| 270 | access.src_type = src_type |
| 271 | access.tgt_type = tgt_type |
| 272 | access.obj_class = obj_class |
| 273 | access.data = data |
| 274 | access.type = avc_type |
| 275 | cls[obj_class, avc_type] = access |
| 276 | |
| 277 | access.perms.update(perms) |
| 278 | if audit_msg: |
| 279 | access.audit_msgs.append(audit_msg) |
| 280 | |
| 281 | def add_av(self, av, audit_msg=None): |
| 282 | """Add an access vector to the set.""" |
| 283 | self.add(av.src_type, av.tgt_type, av.obj_class, av.perms) |
| 284 | |
| 285 | |
| 286 | def avs_extract_types(avs): |
| 287 | types = refpolicy.IdSet() |
| 288 | for av in avs: |
| 289 | types.add(av.src_type) |
| 290 | types.add(av.tgt_type) |
| 291 | |
| 292 | return types |
| 293 | |
| 294 | def avs_extract_obj_perms(avs): |
| 295 | perms = { } |
| 296 | for av in avs: |
| 297 | if av.obj_class in perms: |
| 298 | s = perms[av.obj_class] |
| 299 | else: |
| 300 | s = refpolicy.IdSet() |
| 301 | perms[av.obj_class] = s |
| 302 | s.update(av.perms) |
| 303 | return perms |
| 304 | |
| 305 | class RoleTypeSet: |
| 306 | """A non-overlapping set of role type statements. |
| 307 | |
| 308 | This clas allows the incremental addition of role type statements and |
| 309 | maintains a non-overlapping list of statements. |
| 310 | """ |
| 311 | def __init__(self): |
| 312 | """Initialize an access vector set.""" |
| 313 | self.role_types = {} |
| 314 | |
| 315 | def __iter__(self): |
| 316 | """Iterate over all of the unique role allows statements in the set.""" |
| 317 | for role_type in self.role_types.values(): |
| 318 | yield role_type |
| 319 | |
| 320 | def __len__(self): |
| 321 | """Return the unique number of role allow statements.""" |
| 322 | return len(self.role_types.keys()) |
| 323 | |
| 324 | def add(self, role, type): |
| 325 | if role in self.role_types: |
| 326 | role_type = self.role_types[role] |
| 327 | else: |
| 328 | role_type = refpolicy.RoleType() |
| 329 | role_type.role = role |
| 330 | self.role_types[role] = role_type |
| 331 | |
| 332 | role_type.types.add(type) |