Casey Schaufler | e114e47 | 2008-02-04 22:29:50 -0800 | [diff] [blame] | 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, |
Casey Schaufler | 1544623 | 2008-07-30 15:37:11 -0700 | [diff] [blame] | 160 | * non zero otherwise. It allows that current may have the capability |
Casey Schaufler | e114e47 | 2008-02-04 22:29:50 -0800 | [diff] [blame] | 161 | * to override the rules. |
| 162 | */ |
| 163 | int smk_curacc(char *obj_label, u32 mode) |
| 164 | { |
| 165 | int rc; |
| 166 | |
David Howells | 86a264a | 2008-11-14 10:39:18 +1100 | [diff] [blame] | 167 | rc = smk_access(current_security(), obj_label, mode); |
Casey Schaufler | e114e47 | 2008-02-04 22:29:50 -0800 | [diff] [blame] | 168 | if (rc == 0) |
| 169 | return 0; |
| 170 | |
Casey Schaufler | 1544623 | 2008-07-30 15:37:11 -0700 | [diff] [blame] | 171 | /* |
| 172 | * Return if a specific label has been designated as the |
| 173 | * only one that gets privilege and current does not |
| 174 | * have that label. |
| 175 | */ |
David Howells | b6dff3e | 2008-11-14 10:39:16 +1100 | [diff] [blame] | 176 | if (smack_onlycap != NULL && smack_onlycap != current->cred->security) |
Casey Schaufler | 1544623 | 2008-07-30 15:37:11 -0700 | [diff] [blame] | 177 | return rc; |
| 178 | |
Casey Schaufler | e114e47 | 2008-02-04 22:29:50 -0800 | [diff] [blame] | 179 | if (capable(CAP_MAC_OVERRIDE)) |
| 180 | return 0; |
| 181 | |
| 182 | return rc; |
| 183 | } |
| 184 | |
| 185 | static DEFINE_MUTEX(smack_known_lock); |
| 186 | |
| 187 | /** |
| 188 | * smk_import_entry - import a label, return the list entry |
| 189 | * @string: a text string that might be a Smack label |
| 190 | * @len: the maximum size, or zero if it is NULL terminated. |
| 191 | * |
| 192 | * Returns a pointer to the entry in the label list that |
| 193 | * matches the passed string, adding it if necessary. |
| 194 | */ |
| 195 | struct smack_known *smk_import_entry(const char *string, int len) |
| 196 | { |
| 197 | struct smack_known *skp; |
| 198 | char smack[SMK_LABELLEN]; |
| 199 | int found; |
| 200 | int i; |
| 201 | |
| 202 | if (len <= 0 || len > SMK_MAXLEN) |
| 203 | len = SMK_MAXLEN; |
| 204 | |
| 205 | for (i = 0, found = 0; i < SMK_LABELLEN; i++) { |
| 206 | if (found) |
| 207 | smack[i] = '\0'; |
| 208 | else if (i >= len || string[i] > '~' || string[i] <= ' ' || |
| 209 | string[i] == '/') { |
| 210 | smack[i] = '\0'; |
| 211 | found = 1; |
| 212 | } else |
| 213 | smack[i] = string[i]; |
| 214 | } |
| 215 | |
| 216 | if (smack[0] == '\0') |
| 217 | return NULL; |
| 218 | |
| 219 | mutex_lock(&smack_known_lock); |
| 220 | |
| 221 | for (skp = smack_known; skp != NULL; skp = skp->smk_next) |
| 222 | if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) |
| 223 | break; |
| 224 | |
| 225 | if (skp == NULL) { |
| 226 | skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL); |
| 227 | if (skp != NULL) { |
| 228 | skp->smk_next = smack_known; |
| 229 | strncpy(skp->smk_known, smack, SMK_MAXLEN); |
| 230 | skp->smk_secid = smack_next_secid++; |
| 231 | skp->smk_cipso = NULL; |
| 232 | spin_lock_init(&skp->smk_cipsolock); |
| 233 | /* |
| 234 | * Make sure that the entry is actually |
| 235 | * filled before putting it on the list. |
| 236 | */ |
| 237 | smp_mb(); |
| 238 | smack_known = skp; |
| 239 | } |
| 240 | } |
| 241 | |
| 242 | mutex_unlock(&smack_known_lock); |
| 243 | |
| 244 | return skp; |
| 245 | } |
| 246 | |
| 247 | /** |
| 248 | * smk_import - import a smack label |
| 249 | * @string: a text string that might be a Smack label |
| 250 | * @len: the maximum size, or zero if it is NULL terminated. |
| 251 | * |
| 252 | * Returns a pointer to the label in the label list that |
| 253 | * matches the passed string, adding it if necessary. |
| 254 | */ |
| 255 | char *smk_import(const char *string, int len) |
| 256 | { |
| 257 | struct smack_known *skp; |
| 258 | |
| 259 | skp = smk_import_entry(string, len); |
| 260 | if (skp == NULL) |
| 261 | return NULL; |
| 262 | return skp->smk_known; |
| 263 | } |
| 264 | |
| 265 | /** |
| 266 | * smack_from_secid - find the Smack label associated with a secid |
| 267 | * @secid: an integer that might be associated with a Smack label |
| 268 | * |
| 269 | * Returns a pointer to the appropraite Smack label if there is one, |
| 270 | * otherwise a pointer to the invalid Smack label. |
| 271 | */ |
| 272 | char *smack_from_secid(const u32 secid) |
| 273 | { |
| 274 | struct smack_known *skp; |
| 275 | |
| 276 | for (skp = smack_known; skp != NULL; skp = skp->smk_next) |
| 277 | if (skp->smk_secid == secid) |
| 278 | return skp->smk_known; |
| 279 | |
| 280 | /* |
| 281 | * If we got this far someone asked for the translation |
| 282 | * of a secid that is not on the list. |
| 283 | */ |
| 284 | return smack_known_invalid.smk_known; |
| 285 | } |
| 286 | |
| 287 | /** |
| 288 | * smack_to_secid - find the secid associated with a Smack label |
| 289 | * @smack: the Smack label |
| 290 | * |
| 291 | * Returns the appropriate secid if there is one, |
| 292 | * otherwise 0 |
| 293 | */ |
| 294 | u32 smack_to_secid(const char *smack) |
| 295 | { |
| 296 | struct smack_known *skp; |
| 297 | |
| 298 | for (skp = smack_known; skp != NULL; skp = skp->smk_next) |
| 299 | if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) |
| 300 | return skp->smk_secid; |
| 301 | return 0; |
| 302 | } |
| 303 | |
| 304 | /** |
| 305 | * smack_from_cipso - find the Smack label associated with a CIPSO option |
| 306 | * @level: Bell & LaPadula level from the network |
| 307 | * @cp: Bell & LaPadula categories from the network |
| 308 | * @result: where to put the Smack value |
| 309 | * |
| 310 | * This is a simple lookup in the label table. |
| 311 | * |
| 312 | * This is an odd duck as far as smack handling goes in that |
| 313 | * it sends back a copy of the smack label rather than a pointer |
| 314 | * to the master list. This is done because it is possible for |
| 315 | * a foreign host to send a smack label that is new to this |
| 316 | * machine and hence not on the list. That would not be an |
| 317 | * issue except that adding an entry to the master list can't |
| 318 | * be done at that point. |
| 319 | */ |
| 320 | void smack_from_cipso(u32 level, char *cp, char *result) |
| 321 | { |
| 322 | struct smack_known *kp; |
| 323 | char *final = NULL; |
| 324 | |
| 325 | for (kp = smack_known; final == NULL && kp != NULL; kp = kp->smk_next) { |
| 326 | if (kp->smk_cipso == NULL) |
| 327 | continue; |
| 328 | |
| 329 | spin_lock_bh(&kp->smk_cipsolock); |
| 330 | |
| 331 | if (kp->smk_cipso->smk_level == level && |
| 332 | memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0) |
| 333 | final = kp->smk_known; |
| 334 | |
| 335 | spin_unlock_bh(&kp->smk_cipsolock); |
| 336 | } |
| 337 | if (final == NULL) |
| 338 | final = smack_known_huh.smk_known; |
| 339 | strncpy(result, final, SMK_MAXLEN); |
| 340 | return; |
| 341 | } |
| 342 | |
| 343 | /** |
| 344 | * smack_to_cipso - find the CIPSO option to go with a Smack label |
| 345 | * @smack: a pointer to the smack label in question |
| 346 | * @cp: where to put the result |
| 347 | * |
| 348 | * Returns zero if a value is available, non-zero otherwise. |
| 349 | */ |
| 350 | int smack_to_cipso(const char *smack, struct smack_cipso *cp) |
| 351 | { |
| 352 | struct smack_known *kp; |
| 353 | |
| 354 | for (kp = smack_known; kp != NULL; kp = kp->smk_next) |
| 355 | if (kp->smk_known == smack || |
| 356 | strcmp(kp->smk_known, smack) == 0) |
| 357 | break; |
| 358 | |
| 359 | if (kp == NULL || kp->smk_cipso == NULL) |
| 360 | return -ENOENT; |
| 361 | |
| 362 | memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso)); |
| 363 | return 0; |
| 364 | } |