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