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