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e114e473 CS |
1 | /* |
2 | * Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation, version 2. | |
7 | * | |
8 | * Author: | |
9 | * Casey Schaufler <casey@schaufler-ca.com> | |
10 | * | |
11 | */ | |
12 | ||
13 | #include <linux/types.h> | |
14 | #include <linux/fs.h> | |
15 | #include <linux/sched.h> | |
16 | #include "smack.h" | |
17 | ||
e114e473 | 18 | struct smack_known smack_known_huh = { |
e114e473 CS |
19 | .smk_known = "?", |
20 | .smk_secid = 2, | |
21 | .smk_cipso = NULL, | |
22 | }; | |
23 | ||
24 | struct smack_known smack_known_hat = { | |
e114e473 CS |
25 | .smk_known = "^", |
26 | .smk_secid = 3, | |
27 | .smk_cipso = NULL, | |
28 | }; | |
29 | ||
30 | struct smack_known smack_known_star = { | |
e114e473 CS |
31 | .smk_known = "*", |
32 | .smk_secid = 4, | |
33 | .smk_cipso = NULL, | |
34 | }; | |
35 | ||
36 | struct smack_known smack_known_floor = { | |
e114e473 CS |
37 | .smk_known = "_", |
38 | .smk_secid = 5, | |
39 | .smk_cipso = NULL, | |
40 | }; | |
41 | ||
42 | struct smack_known smack_known_invalid = { | |
e114e473 CS |
43 | .smk_known = "", |
44 | .smk_secid = 6, | |
45 | .smk_cipso = NULL, | |
46 | }; | |
47 | ||
6d3dc07c | 48 | struct smack_known smack_known_web = { |
6d3dc07c CS |
49 | .smk_known = "@", |
50 | .smk_secid = 7, | |
51 | .smk_cipso = NULL, | |
52 | }; | |
53 | ||
7198e2ee | 54 | LIST_HEAD(smack_known_list); |
e114e473 CS |
55 | |
56 | /* | |
57 | * The initial value needs to be bigger than any of the | |
58 | * known values above. | |
59 | */ | |
60 | static u32 smack_next_secid = 10; | |
61 | ||
62 | /** | |
63 | * smk_access - determine if a subject has a specific access to an object | |
64 | * @subject_label: a pointer to the subject's Smack label | |
65 | * @object_label: a pointer to the object's Smack label | |
66 | * @request: the access requested, in "MAY" format | |
67 | * | |
68 | * This function looks up the subject/object pair in the | |
69 | * access rule list and returns 0 if the access is permitted, | |
70 | * non zero otherwise. | |
71 | * | |
72 | * Even though Smack labels are usually shared on smack_list | |
73 | * labels that come in off the network can't be imported | |
74 | * and added to the list for locking reasons. | |
75 | * | |
76 | * Therefore, it is necessary to check the contents of the labels, | |
77 | * not just the pointer values. Of course, in most cases the labels | |
78 | * will be on the list, so checking the pointers may be a worthwhile | |
79 | * optimization. | |
80 | */ | |
81 | int smk_access(char *subject_label, char *object_label, int request) | |
82 | { | |
83 | u32 may = MAY_NOT; | |
e114e473 CS |
84 | struct smack_rule *srp; |
85 | ||
86 | /* | |
87 | * Hardcoded comparisons. | |
88 | * | |
89 | * A star subject can't access any object. | |
90 | */ | |
91 | if (subject_label == smack_known_star.smk_known || | |
92 | strcmp(subject_label, smack_known_star.smk_known) == 0) | |
93 | return -EACCES; | |
6d3dc07c CS |
94 | /* |
95 | * An internet object can be accessed by any subject. | |
96 | * Tasks cannot be assigned the internet label. | |
97 | * An internet subject can access any object. | |
98 | */ | |
99 | if (object_label == smack_known_web.smk_known || | |
100 | subject_label == smack_known_web.smk_known || | |
101 | strcmp(object_label, smack_known_web.smk_known) == 0 || | |
102 | strcmp(subject_label, smack_known_web.smk_known) == 0) | |
103 | return 0; | |
e114e473 CS |
104 | /* |
105 | * A star object can be accessed by any subject. | |
106 | */ | |
107 | if (object_label == smack_known_star.smk_known || | |
108 | strcmp(object_label, smack_known_star.smk_known) == 0) | |
109 | return 0; | |
110 | /* | |
111 | * An object can be accessed in any way by a subject | |
112 | * with the same label. | |
113 | */ | |
114 | if (subject_label == object_label || | |
115 | strcmp(subject_label, object_label) == 0) | |
116 | return 0; | |
117 | /* | |
118 | * A hat subject can read any object. | |
119 | * A floor object can be read by any subject. | |
120 | */ | |
121 | if ((request & MAY_ANYREAD) == request) { | |
122 | if (object_label == smack_known_floor.smk_known || | |
123 | strcmp(object_label, smack_known_floor.smk_known) == 0) | |
124 | return 0; | |
125 | if (subject_label == smack_known_hat.smk_known || | |
126 | strcmp(subject_label, smack_known_hat.smk_known) == 0) | |
127 | return 0; | |
128 | } | |
129 | /* | |
130 | * Beyond here an explicit relationship is required. | |
131 | * If the requested access is contained in the available | |
132 | * access (e.g. read is included in readwrite) it's | |
133 | * good. | |
134 | */ | |
7198e2ee EB |
135 | rcu_read_lock(); |
136 | list_for_each_entry_rcu(srp, &smack_rule_list, list) { | |
e114e473 CS |
137 | if (srp->smk_subject == subject_label || |
138 | strcmp(srp->smk_subject, subject_label) == 0) { | |
139 | if (srp->smk_object == object_label || | |
140 | strcmp(srp->smk_object, object_label) == 0) { | |
141 | may = srp->smk_access; | |
142 | break; | |
143 | } | |
144 | } | |
145 | } | |
7198e2ee | 146 | rcu_read_unlock(); |
e114e473 CS |
147 | /* |
148 | * This is a bit map operation. | |
149 | */ | |
150 | if ((request & may) == request) | |
151 | return 0; | |
152 | ||
153 | return -EACCES; | |
154 | } | |
155 | ||
156 | /** | |
157 | * smk_curacc - determine if current has a specific access to an object | |
251a2a95 RD |
158 | * @obj_label: a pointer to the object's Smack label |
159 | * @mode: the access requested, in "MAY" format | |
e114e473 CS |
160 | * |
161 | * This function checks the current subject label/object label pair | |
162 | * in the access rule list and returns 0 if the access is permitted, | |
15446235 | 163 | * non zero otherwise. It allows that current may have the capability |
e114e473 CS |
164 | * to override the rules. |
165 | */ | |
166 | int smk_curacc(char *obj_label, u32 mode) | |
167 | { | |
168 | int rc; | |
169 | ||
86a264ab | 170 | rc = smk_access(current_security(), obj_label, mode); |
e114e473 CS |
171 | if (rc == 0) |
172 | return 0; | |
173 | ||
15446235 CS |
174 | /* |
175 | * Return if a specific label has been designated as the | |
176 | * only one that gets privilege and current does not | |
177 | * have that label. | |
178 | */ | |
b6dff3ec | 179 | if (smack_onlycap != NULL && smack_onlycap != current->cred->security) |
15446235 CS |
180 | return rc; |
181 | ||
e114e473 CS |
182 | if (capable(CAP_MAC_OVERRIDE)) |
183 | return 0; | |
184 | ||
185 | return rc; | |
186 | } | |
187 | ||
188 | static DEFINE_MUTEX(smack_known_lock); | |
189 | ||
190 | /** | |
191 | * smk_import_entry - import a label, return the list entry | |
192 | * @string: a text string that might be a Smack label | |
193 | * @len: the maximum size, or zero if it is NULL terminated. | |
194 | * | |
195 | * Returns a pointer to the entry in the label list that | |
196 | * matches the passed string, adding it if necessary. | |
197 | */ | |
198 | struct smack_known *smk_import_entry(const char *string, int len) | |
199 | { | |
200 | struct smack_known *skp; | |
201 | char smack[SMK_LABELLEN]; | |
202 | int found; | |
203 | int i; | |
204 | ||
205 | if (len <= 0 || len > SMK_MAXLEN) | |
206 | len = SMK_MAXLEN; | |
207 | ||
208 | for (i = 0, found = 0; i < SMK_LABELLEN; i++) { | |
209 | if (found) | |
210 | smack[i] = '\0'; | |
211 | else if (i >= len || string[i] > '~' || string[i] <= ' ' || | |
212 | string[i] == '/') { | |
213 | smack[i] = '\0'; | |
214 | found = 1; | |
215 | } else | |
216 | smack[i] = string[i]; | |
217 | } | |
218 | ||
219 | if (smack[0] == '\0') | |
220 | return NULL; | |
221 | ||
222 | mutex_lock(&smack_known_lock); | |
223 | ||
7198e2ee EB |
224 | found = 0; |
225 | list_for_each_entry_rcu(skp, &smack_known_list, list) { | |
226 | if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) { | |
227 | found = 1; | |
e114e473 | 228 | break; |
7198e2ee EB |
229 | } |
230 | } | |
e114e473 | 231 | |
7198e2ee | 232 | if (found == 0) { |
e114e473 CS |
233 | skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL); |
234 | if (skp != NULL) { | |
e114e473 CS |
235 | strncpy(skp->smk_known, smack, SMK_MAXLEN); |
236 | skp->smk_secid = smack_next_secid++; | |
237 | skp->smk_cipso = NULL; | |
238 | spin_lock_init(&skp->smk_cipsolock); | |
239 | /* | |
240 | * Make sure that the entry is actually | |
241 | * filled before putting it on the list. | |
242 | */ | |
7198e2ee | 243 | list_add_rcu(&skp->list, &smack_known_list); |
e114e473 CS |
244 | } |
245 | } | |
246 | ||
247 | mutex_unlock(&smack_known_lock); | |
248 | ||
249 | return skp; | |
250 | } | |
251 | ||
252 | /** | |
253 | * smk_import - import a smack label | |
254 | * @string: a text string that might be a Smack label | |
255 | * @len: the maximum size, or zero if it is NULL terminated. | |
256 | * | |
257 | * Returns a pointer to the label in the label list that | |
258 | * matches the passed string, adding it if necessary. | |
259 | */ | |
260 | char *smk_import(const char *string, int len) | |
261 | { | |
262 | struct smack_known *skp; | |
263 | ||
4303154e EB |
264 | /* labels cannot begin with a '-' */ |
265 | if (string[0] == '-') | |
266 | return NULL; | |
e114e473 CS |
267 | skp = smk_import_entry(string, len); |
268 | if (skp == NULL) | |
269 | return NULL; | |
270 | return skp->smk_known; | |
271 | } | |
272 | ||
273 | /** | |
274 | * smack_from_secid - find the Smack label associated with a secid | |
275 | * @secid: an integer that might be associated with a Smack label | |
276 | * | |
277 | * Returns a pointer to the appropraite Smack label if there is one, | |
278 | * otherwise a pointer to the invalid Smack label. | |
279 | */ | |
280 | char *smack_from_secid(const u32 secid) | |
281 | { | |
282 | struct smack_known *skp; | |
283 | ||
7198e2ee EB |
284 | rcu_read_lock(); |
285 | list_for_each_entry_rcu(skp, &smack_known_list, list) { | |
286 | if (skp->smk_secid == secid) { | |
287 | rcu_read_unlock(); | |
e114e473 | 288 | return skp->smk_known; |
7198e2ee EB |
289 | } |
290 | } | |
e114e473 CS |
291 | |
292 | /* | |
293 | * If we got this far someone asked for the translation | |
294 | * of a secid that is not on the list. | |
295 | */ | |
7198e2ee | 296 | rcu_read_unlock(); |
e114e473 CS |
297 | return smack_known_invalid.smk_known; |
298 | } | |
299 | ||
300 | /** | |
301 | * smack_to_secid - find the secid associated with a Smack label | |
302 | * @smack: the Smack label | |
303 | * | |
304 | * Returns the appropriate secid if there is one, | |
305 | * otherwise 0 | |
306 | */ | |
307 | u32 smack_to_secid(const char *smack) | |
308 | { | |
309 | struct smack_known *skp; | |
310 | ||
7198e2ee EB |
311 | rcu_read_lock(); |
312 | list_for_each_entry_rcu(skp, &smack_known_list, list) { | |
313 | if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) { | |
314 | rcu_read_unlock(); | |
e114e473 | 315 | return skp->smk_secid; |
7198e2ee EB |
316 | } |
317 | } | |
318 | rcu_read_unlock(); | |
e114e473 CS |
319 | return 0; |
320 | } | |
321 | ||
322 | /** | |
323 | * smack_from_cipso - find the Smack label associated with a CIPSO option | |
324 | * @level: Bell & LaPadula level from the network | |
325 | * @cp: Bell & LaPadula categories from the network | |
326 | * @result: where to put the Smack value | |
327 | * | |
328 | * This is a simple lookup in the label table. | |
329 | * | |
330 | * This is an odd duck as far as smack handling goes in that | |
331 | * it sends back a copy of the smack label rather than a pointer | |
332 | * to the master list. This is done because it is possible for | |
333 | * a foreign host to send a smack label that is new to this | |
334 | * machine and hence not on the list. That would not be an | |
335 | * issue except that adding an entry to the master list can't | |
336 | * be done at that point. | |
337 | */ | |
338 | void smack_from_cipso(u32 level, char *cp, char *result) | |
339 | { | |
340 | struct smack_known *kp; | |
341 | char *final = NULL; | |
342 | ||
7198e2ee EB |
343 | rcu_read_lock(); |
344 | list_for_each_entry(kp, &smack_known_list, list) { | |
e114e473 CS |
345 | if (kp->smk_cipso == NULL) |
346 | continue; | |
347 | ||
348 | spin_lock_bh(&kp->smk_cipsolock); | |
349 | ||
350 | if (kp->smk_cipso->smk_level == level && | |
351 | memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0) | |
352 | final = kp->smk_known; | |
353 | ||
354 | spin_unlock_bh(&kp->smk_cipsolock); | |
355 | } | |
7198e2ee | 356 | rcu_read_unlock(); |
e114e473 CS |
357 | if (final == NULL) |
358 | final = smack_known_huh.smk_known; | |
359 | strncpy(result, final, SMK_MAXLEN); | |
360 | return; | |
361 | } | |
362 | ||
363 | /** | |
364 | * smack_to_cipso - find the CIPSO option to go with a Smack label | |
365 | * @smack: a pointer to the smack label in question | |
366 | * @cp: where to put the result | |
367 | * | |
368 | * Returns zero if a value is available, non-zero otherwise. | |
369 | */ | |
370 | int smack_to_cipso(const char *smack, struct smack_cipso *cp) | |
371 | { | |
372 | struct smack_known *kp; | |
7198e2ee | 373 | int found = 0; |
e114e473 | 374 | |
7198e2ee EB |
375 | rcu_read_lock(); |
376 | list_for_each_entry_rcu(kp, &smack_known_list, list) { | |
e114e473 | 377 | if (kp->smk_known == smack || |
7198e2ee EB |
378 | strcmp(kp->smk_known, smack) == 0) { |
379 | found = 1; | |
e114e473 | 380 | break; |
7198e2ee EB |
381 | } |
382 | } | |
383 | rcu_read_unlock(); | |
e114e473 | 384 | |
7198e2ee | 385 | if (found == 0 || kp->smk_cipso == NULL) |
e114e473 CS |
386 | return -ENOENT; |
387 | ||
388 | memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso)); | |
389 | return 0; | |
390 | } |