1 /* 2 * AppArmor security module 3 * 4 * This file contains AppArmor mediation of files 5 * 6 * Copyright (C) 1998-2008 Novell/SUSE 7 * Copyright 2009-2010 Canonical Ltd. 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License as 11 * published by the Free Software Foundation, version 2 of the 12 * License. 13 */ 14 15 #include "include/apparmor.h" 16 #include "include/audit.h" 17 #include "include/file.h" 18 #include "include/match.h" 19 #include "include/path.h" 20 #include "include/policy.h" 21 22 struct file_perms nullperms; 23 24 25 /** 26 * audit_file_mask - convert mask to permission string 27 * @buffer: buffer to write string to (NOT NULL) 28 * @mask: permission mask to convert 29 */ 30 static void audit_file_mask(struct audit_buffer *ab, u32 mask) 31 { 32 char str[10]; 33 34 char *m = str; 35 36 if (mask & AA_EXEC_MMAP) 37 *m++ = 'm'; 38 if (mask & (MAY_READ | AA_MAY_META_READ)) 39 *m++ = 'r'; 40 if (mask & (MAY_WRITE | AA_MAY_META_WRITE | AA_MAY_CHMOD | 41 AA_MAY_CHOWN)) 42 *m++ = 'w'; 43 else if (mask & MAY_APPEND) 44 *m++ = 'a'; 45 if (mask & AA_MAY_CREATE) 46 *m++ = 'c'; 47 if (mask & AA_MAY_DELETE) 48 *m++ = 'd'; 49 if (mask & AA_MAY_LINK) 50 *m++ = 'l'; 51 if (mask & AA_MAY_LOCK) 52 *m++ = 'k'; 53 if (mask & MAY_EXEC) 54 *m++ = 'x'; 55 *m = '\0'; 56 57 audit_log_string(ab, str); 58 } 59 60 /** 61 * file_audit_cb - call back for file specific audit fields 62 * @ab: audit_buffer (NOT NULL) 63 * @va: audit struct to audit values of (NOT NULL) 64 */ 65 static void file_audit_cb(struct audit_buffer *ab, void *va) 66 { 67 struct common_audit_data *sa = va; 68 kuid_t fsuid = current_fsuid(); 69 70 if (aad(sa)->fs.request & AA_AUDIT_FILE_MASK) { 71 audit_log_format(ab, " requested_mask="); 72 audit_file_mask(ab, aad(sa)->fs.request); 73 } 74 if (aad(sa)->fs.denied & AA_AUDIT_FILE_MASK) { 75 audit_log_format(ab, " denied_mask="); 76 audit_file_mask(ab, aad(sa)->fs.denied); 77 } 78 if (aad(sa)->fs.request & AA_AUDIT_FILE_MASK) { 79 audit_log_format(ab, " fsuid=%d", 80 from_kuid(&init_user_ns, fsuid)); 81 audit_log_format(ab, " ouid=%d", 82 from_kuid(&init_user_ns, aad(sa)->fs.ouid)); 83 } 84 85 if (aad(sa)->fs.target) { 86 audit_log_format(ab, " target="); 87 audit_log_untrustedstring(ab, aad(sa)->fs.target); 88 } 89 } 90 91 /** 92 * aa_audit_file - handle the auditing of file operations 93 * @profile: the profile being enforced (NOT NULL) 94 * @perms: the permissions computed for the request (NOT NULL) 95 * @gfp: allocation flags 96 * @op: operation being mediated 97 * @request: permissions requested 98 * @name: name of object being mediated (MAYBE NULL) 99 * @target: name of target (MAYBE NULL) 100 * @ouid: object uid 101 * @info: extra information message (MAYBE NULL) 102 * @error: 0 if operation allowed else failure error code 103 * 104 * Returns: %0 or error on failure 105 */ 106 int aa_audit_file(struct aa_profile *profile, struct file_perms *perms, 107 const char *op, u32 request, const char *name, 108 const char *target, kuid_t ouid, const char *info, int error) 109 { 110 int type = AUDIT_APPARMOR_AUTO; 111 DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, op); 112 113 sa.u.tsk = NULL; 114 aad(&sa)->fs.request = request; 115 aad(&sa)->name = name; 116 aad(&sa)->fs.target = target; 117 aad(&sa)->fs.ouid = ouid; 118 aad(&sa)->info = info; 119 aad(&sa)->error = error; 120 sa.u.tsk = NULL; 121 122 if (likely(!aad(&sa)->error)) { 123 u32 mask = perms->audit; 124 125 if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL)) 126 mask = 0xffff; 127 128 /* mask off perms that are not being force audited */ 129 aad(&sa)->fs.request &= mask; 130 131 if (likely(!aad(&sa)->fs.request)) 132 return 0; 133 type = AUDIT_APPARMOR_AUDIT; 134 } else { 135 /* only report permissions that were denied */ 136 aad(&sa)->fs.request = aad(&sa)->fs.request & ~perms->allow; 137 AA_BUG(!aad(&sa)->fs.request); 138 139 if (aad(&sa)->fs.request & perms->kill) 140 type = AUDIT_APPARMOR_KILL; 141 142 /* quiet known rejects, assumes quiet and kill do not overlap */ 143 if ((aad(&sa)->fs.request & perms->quiet) && 144 AUDIT_MODE(profile) != AUDIT_NOQUIET && 145 AUDIT_MODE(profile) != AUDIT_ALL) 146 aad(&sa)->fs.request &= ~perms->quiet; 147 148 if (!aad(&sa)->fs.request) 149 return COMPLAIN_MODE(profile) ? 0 : aad(&sa)->error; 150 } 151 152 aad(&sa)->fs.denied = aad(&sa)->fs.request & ~perms->allow; 153 return aa_audit(type, profile, &sa, file_audit_cb); 154 } 155 156 /** 157 * map_old_perms - map old file perms layout to the new layout 158 * @old: permission set in old mapping 159 * 160 * Returns: new permission mapping 161 */ 162 static u32 map_old_perms(u32 old) 163 { 164 u32 new = old & 0xf; 165 if (old & MAY_READ) 166 new |= AA_MAY_META_READ; 167 if (old & MAY_WRITE) 168 new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE | 169 AA_MAY_CHMOD | AA_MAY_CHOWN; 170 if (old & 0x10) 171 new |= AA_MAY_LINK; 172 /* the old mapping lock and link_subset flags where overlaid 173 * and use was determined by part of a pair that they were in 174 */ 175 if (old & 0x20) 176 new |= AA_MAY_LOCK | AA_LINK_SUBSET; 177 if (old & 0x40) /* AA_EXEC_MMAP */ 178 new |= AA_EXEC_MMAP; 179 180 return new; 181 } 182 183 /** 184 * compute_perms - convert dfa compressed perms to internal perms 185 * @dfa: dfa to compute perms for (NOT NULL) 186 * @state: state in dfa 187 * @cond: conditions to consider (NOT NULL) 188 * 189 * TODO: convert from dfa + state to permission entry, do computation conversion 190 * at load time. 191 * 192 * Returns: computed permission set 193 */ 194 static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state, 195 struct path_cond *cond) 196 { 197 struct file_perms perms; 198 199 /* FIXME: change over to new dfa format 200 * currently file perms are encoded in the dfa, new format 201 * splits the permissions from the dfa. This mapping can be 202 * done at profile load 203 */ 204 perms.kill = 0; 205 206 if (uid_eq(current_fsuid(), cond->uid)) { 207 perms.allow = map_old_perms(dfa_user_allow(dfa, state)); 208 perms.audit = map_old_perms(dfa_user_audit(dfa, state)); 209 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state)); 210 perms.xindex = dfa_user_xindex(dfa, state); 211 } else { 212 perms.allow = map_old_perms(dfa_other_allow(dfa, state)); 213 perms.audit = map_old_perms(dfa_other_audit(dfa, state)); 214 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state)); 215 perms.xindex = dfa_other_xindex(dfa, state); 216 } 217 perms.allow |= AA_MAY_META_READ; 218 219 /* change_profile wasn't determined by ownership in old mapping */ 220 if (ACCEPT_TABLE(dfa)[state] & 0x80000000) 221 perms.allow |= AA_MAY_CHANGE_PROFILE; 222 if (ACCEPT_TABLE(dfa)[state] & 0x40000000) 223 perms.allow |= AA_MAY_ONEXEC; 224 225 return perms; 226 } 227 228 /** 229 * aa_str_perms - find permission that match @name 230 * @dfa: to match against (MAYBE NULL) 231 * @state: state to start matching in 232 * @name: string to match against dfa (NOT NULL) 233 * @cond: conditions to consider for permission set computation (NOT NULL) 234 * @perms: Returns - the permissions found when matching @name 235 * 236 * Returns: the final state in @dfa when beginning @start and walking @name 237 */ 238 unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start, 239 const char *name, struct path_cond *cond, 240 struct file_perms *perms) 241 { 242 unsigned int state; 243 if (!dfa) { 244 *perms = nullperms; 245 return DFA_NOMATCH; 246 } 247 248 state = aa_dfa_match(dfa, start, name); 249 *perms = compute_perms(dfa, state, cond); 250 251 return state; 252 } 253 254 /** 255 * is_deleted - test if a file has been completely unlinked 256 * @dentry: dentry of file to test for deletion (NOT NULL) 257 * 258 * Returns: %1 if deleted else %0 259 */ 260 static inline bool is_deleted(struct dentry *dentry) 261 { 262 if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0) 263 return 1; 264 return 0; 265 } 266 267 /** 268 * aa_path_perm - do permissions check & audit for @path 269 * @op: operation being checked 270 * @profile: profile being enforced (NOT NULL) 271 * @path: path to check permissions of (NOT NULL) 272 * @flags: any additional path flags beyond what the profile specifies 273 * @request: requested permissions 274 * @cond: conditional info for this request (NOT NULL) 275 * 276 * Returns: %0 else error if access denied or other error 277 */ 278 int aa_path_perm(const char *op, struct aa_profile *profile, 279 const struct path *path, int flags, u32 request, 280 struct path_cond *cond) 281 { 282 char *buffer = NULL; 283 struct file_perms perms = {}; 284 const char *name, *info = NULL; 285 int error; 286 287 flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0); 288 error = aa_path_name(path, flags, &buffer, &name, &info); 289 if (error) { 290 if (error == -ENOENT && is_deleted(path->dentry)) { 291 /* Access to open files that are deleted are 292 * give a pass (implicit delegation) 293 */ 294 error = 0; 295 info = NULL; 296 perms.allow = request; 297 } 298 } else { 299 aa_str_perms(profile->file.dfa, profile->file.start, name, cond, 300 &perms); 301 if (request & ~perms.allow) 302 error = -EACCES; 303 } 304 error = aa_audit_file(profile, &perms, op, request, name, NULL, 305 cond->uid, info, error); 306 kfree(buffer); 307 308 return error; 309 } 310 311 /** 312 * xindex_is_subset - helper for aa_path_link 313 * @link: link permission set 314 * @target: target permission set 315 * 316 * test target x permissions are equal OR a subset of link x permissions 317 * this is done as part of the subset test, where a hardlink must have 318 * a subset of permissions that the target has. 319 * 320 * Returns: %1 if subset else %0 321 */ 322 static inline bool xindex_is_subset(u32 link, u32 target) 323 { 324 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) || 325 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE))) 326 return 0; 327 328 return 1; 329 } 330 331 /** 332 * aa_path_link - Handle hard link permission check 333 * @profile: the profile being enforced (NOT NULL) 334 * @old_dentry: the target dentry (NOT NULL) 335 * @new_dir: directory the new link will be created in (NOT NULL) 336 * @new_dentry: the link being created (NOT NULL) 337 * 338 * Handle the permission test for a link & target pair. Permission 339 * is encoded as a pair where the link permission is determined 340 * first, and if allowed, the target is tested. The target test 341 * is done from the point of the link match (not start of DFA) 342 * making the target permission dependent on the link permission match. 343 * 344 * The subset test if required forces that permissions granted 345 * on link are a subset of the permission granted to target. 346 * 347 * Returns: %0 if allowed else error 348 */ 349 int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry, 350 const struct path *new_dir, struct dentry *new_dentry) 351 { 352 struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry }; 353 struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry }; 354 struct path_cond cond = { 355 d_backing_inode(old_dentry)->i_uid, 356 d_backing_inode(old_dentry)->i_mode 357 }; 358 char *buffer = NULL, *buffer2 = NULL; 359 const char *lname, *tname = NULL, *info = NULL; 360 struct file_perms lperms, perms; 361 u32 request = AA_MAY_LINK; 362 unsigned int state; 363 int error; 364 365 lperms = nullperms; 366 367 /* buffer freed below, lname is pointer in buffer */ 368 error = aa_path_name(&link, profile->path_flags, &buffer, &lname, 369 &info); 370 if (error) 371 goto audit; 372 373 /* buffer2 freed below, tname is pointer in buffer2 */ 374 error = aa_path_name(&target, profile->path_flags, &buffer2, &tname, 375 &info); 376 if (error) 377 goto audit; 378 379 error = -EACCES; 380 /* aa_str_perms - handles the case of the dfa being NULL */ 381 state = aa_str_perms(profile->file.dfa, profile->file.start, lname, 382 &cond, &lperms); 383 384 if (!(lperms.allow & AA_MAY_LINK)) 385 goto audit; 386 387 /* test to see if target can be paired with link */ 388 state = aa_dfa_null_transition(profile->file.dfa, state); 389 aa_str_perms(profile->file.dfa, state, tname, &cond, &perms); 390 391 /* force audit/quiet masks for link are stored in the second entry 392 * in the link pair. 393 */ 394 lperms.audit = perms.audit; 395 lperms.quiet = perms.quiet; 396 lperms.kill = perms.kill; 397 398 if (!(perms.allow & AA_MAY_LINK)) { 399 info = "target restricted"; 400 goto audit; 401 } 402 403 /* done if link subset test is not required */ 404 if (!(perms.allow & AA_LINK_SUBSET)) 405 goto done_tests; 406 407 /* Do link perm subset test requiring allowed permission on link are a 408 * subset of the allowed permissions on target. 409 */ 410 aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond, 411 &perms); 412 413 /* AA_MAY_LINK is not considered in the subset test */ 414 request = lperms.allow & ~AA_MAY_LINK; 415 lperms.allow &= perms.allow | AA_MAY_LINK; 416 417 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow); 418 if (request & ~lperms.allow) { 419 goto audit; 420 } else if ((lperms.allow & MAY_EXEC) && 421 !xindex_is_subset(lperms.xindex, perms.xindex)) { 422 lperms.allow &= ~MAY_EXEC; 423 request |= MAY_EXEC; 424 info = "link not subset of target"; 425 goto audit; 426 } 427 428 done_tests: 429 error = 0; 430 431 audit: 432 error = aa_audit_file(profile, &lperms, OP_LINK, request, 433 lname, tname, cond.uid, info, error); 434 kfree(buffer); 435 kfree(buffer2); 436 437 return error; 438 } 439 440 /** 441 * aa_file_perm - do permission revalidation check & audit for @file 442 * @op: operation being checked 443 * @profile: profile being enforced (NOT NULL) 444 * @file: file to revalidate access permissions on (NOT NULL) 445 * @request: requested permissions 446 * 447 * Returns: %0 if access allowed else error 448 */ 449 int aa_file_perm(const char *op, struct aa_profile *profile, struct file *file, 450 u32 request) 451 { 452 struct path_cond cond = { 453 .uid = file_inode(file)->i_uid, 454 .mode = file_inode(file)->i_mode 455 }; 456 457 return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED, 458 request, &cond); 459 } 460