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 22struct 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 */ 30static 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 */ 65static 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 */ 104int 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 */ 158static 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 new |= AA_MAY_META_READ; 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 */ 192static 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 perms.kill = 0; 198 199 if (current_fsuid() == cond->uid) { 200 perms.allow = map_old_perms(dfa_user_allow(dfa, state)); 201 perms.audit = map_old_perms(dfa_user_audit(dfa, state)); 202 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state)); 203 perms.xindex = dfa_user_xindex(dfa, state); 204 } else { 205 perms.allow = map_old_perms(dfa_other_allow(dfa, state)); 206 perms.audit = map_old_perms(dfa_other_audit(dfa, state)); 207 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state)); 208 perms.xindex = dfa_other_xindex(dfa, state); 209 } 210 211 /* change_profile wasn't determined by ownership in old mapping */ 212 if (ACCEPT_TABLE(dfa)[state] & 0x80000000) 213 perms.allow |= AA_MAY_CHANGE_PROFILE; 214 215 return perms; 216} 217 218/** 219 * aa_str_perms - find permission that match @name 220 * @dfa: to match against (MAYBE NULL) 221 * @state: state to start matching in 222 * @name: string to match against dfa (NOT NULL) 223 * @cond: conditions to consider for permission set computation (NOT NULL) 224 * @perms: Returns - the permissions found when matching @name 225 * 226 * Returns: the final state in @dfa when beginning @start and walking @name 227 */ 228unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start, 229 const char *name, struct path_cond *cond, 230 struct file_perms *perms) 231{ 232 unsigned int state; 233 if (!dfa) { 234 *perms = nullperms; 235 return DFA_NOMATCH; 236 } 237 238 state = aa_dfa_match(dfa, start, name); 239 *perms = compute_perms(dfa, state, cond); 240 241 return state; 242} 243 244/** 245 * is_deleted - test if a file has been completely unlinked 246 * @dentry: dentry of file to test for deletion (NOT NULL) 247 * 248 * Returns: %1 if deleted else %0 249 */ 250static inline bool is_deleted(struct dentry *dentry) 251{ 252 if (d_unlinked(dentry) && dentry->d_inode->i_nlink == 0) 253 return 1; 254 return 0; 255} 256 257/** 258 * aa_path_perm - do permissions check & audit for @path 259 * @op: operation being checked 260 * @profile: profile being enforced (NOT NULL) 261 * @path: path to check permissions of (NOT NULL) 262 * @flags: any additional path flags beyond what the profile specifies 263 * @request: requested permissions 264 * @cond: conditional info for this request (NOT NULL) 265 * 266 * Returns: %0 else error if access denied or other error 267 */ 268int aa_path_perm(int op, struct aa_profile *profile, struct path *path, 269 int flags, u32 request, struct path_cond *cond) 270{ 271 char *buffer = NULL; 272 struct file_perms perms = {}; 273 const char *name, *info = NULL; 274 int error; 275 276 flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0); 277 error = aa_get_name(path, flags, &buffer, &name); 278 if (error) { 279 if (error == -ENOENT && is_deleted(path->dentry)) { 280 /* Access to open files that are deleted are 281 * give a pass (implicit delegation) 282 */ 283 error = 0; 284 perms.allow = request; 285 } else if (error == -ENOENT) 286 info = "Failed name lookup - deleted entry"; 287 else if (error == -ESTALE) 288 info = "Failed name lookup - disconnected path"; 289 else if (error == -ENAMETOOLONG) 290 info = "Failed name lookup - name too long"; 291 else 292 info = "Failed name lookup"; 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 */ 317static 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 */ 344int 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_get_name(&link, profile->path_flags, &buffer, &lname); 364 if (error) 365 goto audit; 366 367 /* buffer2 freed below, tname is pointer in buffer2 */ 368 error = aa_get_name(&target, profile->path_flags, &buffer2, &tname); 369 if (error) 370 goto audit; 371 372 error = -EACCES; 373 /* aa_str_perms - handles the case of the dfa being NULL */ 374 state = aa_str_perms(profile->file.dfa, profile->file.start, lname, 375 &cond, &lperms); 376 377 if (!(lperms.allow & AA_MAY_LINK)) 378 goto audit; 379 380 /* test to see if target can be paired with link */ 381 state = aa_dfa_null_transition(profile->file.dfa, state); 382 aa_str_perms(profile->file.dfa, state, tname, &cond, &perms); 383 384 /* force audit/quiet masks for link are stored in the second entry 385 * in the link pair. 386 */ 387 lperms.audit = perms.audit; 388 lperms.quiet = perms.quiet; 389 lperms.kill = perms.kill; 390 391 if (!(perms.allow & AA_MAY_LINK)) { 392 info = "target restricted"; 393 goto audit; 394 } 395 396 /* done if link subset test is not required */ 397 if (!(perms.allow & AA_LINK_SUBSET)) 398 goto done_tests; 399 400 /* Do link perm subset test requiring allowed permission on link are a 401 * subset of the allowed permissions on target. 402 */ 403 aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond, 404 &perms); 405 406 /* AA_MAY_LINK is not considered in the subset test */ 407 request = lperms.allow & ~AA_MAY_LINK; 408 lperms.allow &= perms.allow | AA_MAY_LINK; 409 410 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow); 411 if (request & ~lperms.allow) { 412 goto audit; 413 } else if ((lperms.allow & MAY_EXEC) && 414 !xindex_is_subset(lperms.xindex, perms.xindex)) { 415 lperms.allow &= ~MAY_EXEC; 416 request |= MAY_EXEC; 417 info = "link not subset of target"; 418 goto audit; 419 } 420 421done_tests: 422 error = 0; 423 424audit: 425 error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request, 426 lname, tname, cond.uid, info, error); 427 kfree(buffer); 428 kfree(buffer2); 429 430 return error; 431} 432 433/** 434 * aa_file_perm - do permission revalidation check & audit for @file 435 * @op: operation being checked 436 * @profile: profile being enforced (NOT NULL) 437 * @file: file to revalidate access permissions on (NOT NULL) 438 * @request: requested permissions 439 * 440 * Returns: %0 if access allowed else error 441 */ 442int aa_file_perm(int op, struct aa_profile *profile, struct file *file, 443 u32 request) 444{ 445 struct path_cond cond = { 446 .uid = file->f_path.dentry->d_inode->i_uid, 447 .mode = file->f_path.dentry->d_inode->i_mode 448 }; 449 450 return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED, 451 request, &cond); 452} 453