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