| 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
| 2 | /* Task credentials management - see Documentation/security/credentials.rst |
| 3 | * |
| 4 | * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. |
| 5 | * Written by David Howells (dhowells@redhat.com) |
| 6 | */ |
| 7 | |
| 8 | #define pr_fmt(fmt) "CRED: " fmt |
| 9 | |
| 10 | #include <linux/export.h> |
| 11 | #include <linux/cred.h> |
| 12 | #include <linux/slab.h> |
| 13 | #include <linux/sched.h> |
| 14 | #include <linux/sched/coredump.h> |
| 15 | #include <linux/key.h> |
| 16 | #include <linux/keyctl.h> |
| 17 | #include <linux/init_task.h> |
| 18 | #include <linux/security.h> |
| 19 | #include <linux/binfmts.h> |
| 20 | #include <linux/cn_proc.h> |
| 21 | #include <linux/uidgid.h> |
| 22 | |
| 23 | #if 0 |
| 24 | #define kdebug(FMT, ...) \ |
| 25 | printk("[%-5.5s%5u] " FMT "\n", \ |
| 26 | current->comm, current->pid, ##__VA_ARGS__) |
| 27 | #else |
| 28 | #define kdebug(FMT, ...) \ |
| 29 | do { \ |
| 30 | if (0) \ |
| 31 | no_printk("[%-5.5s%5u] " FMT "\n", \ |
| 32 | current->comm, current->pid, ##__VA_ARGS__); \ |
| 33 | } while (0) |
| 34 | #endif |
| 35 | |
| 36 | static struct kmem_cache *cred_jar; |
| 37 | |
| 38 | /* init to 2 - one for init_task, one to ensure it is never freed */ |
| 39 | static struct group_info init_groups = { .usage = ATOMIC_INIT(2) }; |
| 40 | |
| 41 | /* |
| 42 | * The initial credentials for the initial task |
| 43 | */ |
| 44 | struct cred init_cred = { |
| 45 | .usage = ATOMIC_INIT(4), |
| 46 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 47 | .subscribers = ATOMIC_INIT(2), |
| 48 | .magic = CRED_MAGIC, |
| 49 | #endif |
| 50 | .uid = GLOBAL_ROOT_UID, |
| 51 | .gid = GLOBAL_ROOT_GID, |
| 52 | .suid = GLOBAL_ROOT_UID, |
| 53 | .sgid = GLOBAL_ROOT_GID, |
| 54 | .euid = GLOBAL_ROOT_UID, |
| 55 | .egid = GLOBAL_ROOT_GID, |
| 56 | .fsuid = GLOBAL_ROOT_UID, |
| 57 | .fsgid = GLOBAL_ROOT_GID, |
| 58 | .securebits = SECUREBITS_DEFAULT, |
| 59 | .cap_inheritable = CAP_EMPTY_SET, |
| 60 | .cap_permitted = CAP_FULL_SET, |
| 61 | .cap_effective = CAP_FULL_SET, |
| 62 | .cap_bset = CAP_FULL_SET, |
| 63 | .user = INIT_USER, |
| 64 | .user_ns = &init_user_ns, |
| 65 | .group_info = &init_groups, |
| 66 | .ucounts = &init_ucounts, |
| 67 | }; |
| 68 | |
| 69 | static inline void set_cred_subscribers(struct cred *cred, int n) |
| 70 | { |
| 71 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 72 | atomic_set(&cred->subscribers, n); |
| 73 | #endif |
| 74 | } |
| 75 | |
| 76 | static inline int read_cred_subscribers(const struct cred *cred) |
| 77 | { |
| 78 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 79 | return atomic_read(&cred->subscribers); |
| 80 | #else |
| 81 | return 0; |
| 82 | #endif |
| 83 | } |
| 84 | |
| 85 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) |
| 86 | { |
| 87 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 88 | struct cred *cred = (struct cred *) _cred; |
| 89 | |
| 90 | atomic_add(n, &cred->subscribers); |
| 91 | #endif |
| 92 | } |
| 93 | |
| 94 | /* |
| 95 | * The RCU callback to actually dispose of a set of credentials |
| 96 | */ |
| 97 | static void put_cred_rcu(struct rcu_head *rcu) |
| 98 | { |
| 99 | struct cred *cred = container_of(rcu, struct cred, rcu); |
| 100 | |
| 101 | kdebug("put_cred_rcu(%p)", cred); |
| 102 | |
| 103 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 104 | if (cred->magic != CRED_MAGIC_DEAD || |
| 105 | atomic_read(&cred->usage) != 0 || |
| 106 | read_cred_subscribers(cred) != 0) |
| 107 | panic("CRED: put_cred_rcu() sees %p with" |
| 108 | " mag %x, put %p, usage %d, subscr %d\n", |
| 109 | cred, cred->magic, cred->put_addr, |
| 110 | atomic_read(&cred->usage), |
| 111 | read_cred_subscribers(cred)); |
| 112 | #else |
| 113 | if (atomic_read(&cred->usage) != 0) |
| 114 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", |
| 115 | cred, atomic_read(&cred->usage)); |
| 116 | #endif |
| 117 | |
| 118 | security_cred_free(cred); |
| 119 | key_put(cred->session_keyring); |
| 120 | key_put(cred->process_keyring); |
| 121 | key_put(cred->thread_keyring); |
| 122 | key_put(cred->request_key_auth); |
| 123 | if (cred->group_info) |
| 124 | put_group_info(cred->group_info); |
| 125 | free_uid(cred->user); |
| 126 | if (cred->ucounts) |
| 127 | put_ucounts(cred->ucounts); |
| 128 | put_user_ns(cred->user_ns); |
| 129 | kmem_cache_free(cred_jar, cred); |
| 130 | } |
| 131 | |
| 132 | /** |
| 133 | * __put_cred - Destroy a set of credentials |
| 134 | * @cred: The record to release |
| 135 | * |
| 136 | * Destroy a set of credentials on which no references remain. |
| 137 | */ |
| 138 | void __put_cred(struct cred *cred) |
| 139 | { |
| 140 | kdebug("__put_cred(%p{%d,%d})", cred, |
| 141 | atomic_read(&cred->usage), |
| 142 | read_cred_subscribers(cred)); |
| 143 | |
| 144 | BUG_ON(atomic_read(&cred->usage) != 0); |
| 145 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 146 | BUG_ON(read_cred_subscribers(cred) != 0); |
| 147 | cred->magic = CRED_MAGIC_DEAD; |
| 148 | cred->put_addr = __builtin_return_address(0); |
| 149 | #endif |
| 150 | BUG_ON(cred == current->cred); |
| 151 | BUG_ON(cred == current->real_cred); |
| 152 | |
| 153 | if (cred->non_rcu) |
| 154 | put_cred_rcu(&cred->rcu); |
| 155 | else |
| 156 | call_rcu(&cred->rcu, put_cred_rcu); |
| 157 | } |
| 158 | EXPORT_SYMBOL(__put_cred); |
| 159 | |
| 160 | /* |
| 161 | * Clean up a task's credentials when it exits |
| 162 | */ |
| 163 | void exit_creds(struct task_struct *tsk) |
| 164 | { |
| 165 | struct cred *cred; |
| 166 | |
| 167 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, |
| 168 | atomic_read(&tsk->cred->usage), |
| 169 | read_cred_subscribers(tsk->cred)); |
| 170 | |
| 171 | cred = (struct cred *) tsk->real_cred; |
| 172 | tsk->real_cred = NULL; |
| 173 | validate_creds(cred); |
| 174 | alter_cred_subscribers(cred, -1); |
| 175 | put_cred(cred); |
| 176 | |
| 177 | cred = (struct cred *) tsk->cred; |
| 178 | tsk->cred = NULL; |
| 179 | validate_creds(cred); |
| 180 | alter_cred_subscribers(cred, -1); |
| 181 | put_cred(cred); |
| 182 | |
| 183 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
| 184 | key_put(tsk->cached_requested_key); |
| 185 | tsk->cached_requested_key = NULL; |
| 186 | #endif |
| 187 | } |
| 188 | |
| 189 | /** |
| 190 | * get_task_cred - Get another task's objective credentials |
| 191 | * @task: The task to query |
| 192 | * |
| 193 | * Get the objective credentials of a task, pinning them so that they can't go |
| 194 | * away. Accessing a task's credentials directly is not permitted. |
| 195 | * |
| 196 | * The caller must also make sure task doesn't get deleted, either by holding a |
| 197 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. |
| 198 | */ |
| 199 | const struct cred *get_task_cred(struct task_struct *task) |
| 200 | { |
| 201 | const struct cred *cred; |
| 202 | |
| 203 | rcu_read_lock(); |
| 204 | |
| 205 | do { |
| 206 | cred = __task_cred((task)); |
| 207 | BUG_ON(!cred); |
| 208 | } while (!get_cred_rcu(cred)); |
| 209 | |
| 210 | rcu_read_unlock(); |
| 211 | return cred; |
| 212 | } |
| 213 | EXPORT_SYMBOL(get_task_cred); |
| 214 | |
| 215 | /* |
| 216 | * Allocate blank credentials, such that the credentials can be filled in at a |
| 217 | * later date without risk of ENOMEM. |
| 218 | */ |
| 219 | struct cred *cred_alloc_blank(void) |
| 220 | { |
| 221 | struct cred *new; |
| 222 | |
| 223 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); |
| 224 | if (!new) |
| 225 | return NULL; |
| 226 | |
| 227 | atomic_set(&new->usage, 1); |
| 228 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 229 | new->magic = CRED_MAGIC; |
| 230 | #endif |
| 231 | if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0) |
| 232 | goto error; |
| 233 | |
| 234 | return new; |
| 235 | |
| 236 | error: |
| 237 | abort_creds(new); |
| 238 | return NULL; |
| 239 | } |
| 240 | |
| 241 | /** |
| 242 | * prepare_creds - Prepare a new set of credentials for modification |
| 243 | * |
| 244 | * Prepare a new set of task credentials for modification. A task's creds |
| 245 | * shouldn't generally be modified directly, therefore this function is used to |
| 246 | * prepare a new copy, which the caller then modifies and then commits by |
| 247 | * calling commit_creds(). |
| 248 | * |
| 249 | * Preparation involves making a copy of the objective creds for modification. |
| 250 | * |
| 251 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
| 252 | * |
| 253 | * Call commit_creds() or abort_creds() to clean up. |
| 254 | */ |
| 255 | struct cred *prepare_creds(void) |
| 256 | { |
| 257 | struct task_struct *task = current; |
| 258 | const struct cred *old; |
| 259 | struct cred *new; |
| 260 | |
| 261 | validate_process_creds(); |
| 262 | |
| 263 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
| 264 | if (!new) |
| 265 | return NULL; |
| 266 | |
| 267 | kdebug("prepare_creds() alloc %p", new); |
| 268 | |
| 269 | old = task->cred; |
| 270 | memcpy(new, old, sizeof(struct cred)); |
| 271 | |
| 272 | new->non_rcu = 0; |
| 273 | atomic_set(&new->usage, 1); |
| 274 | set_cred_subscribers(new, 0); |
| 275 | get_group_info(new->group_info); |
| 276 | get_uid(new->user); |
| 277 | get_user_ns(new->user_ns); |
| 278 | |
| 279 | #ifdef CONFIG_KEYS |
| 280 | key_get(new->session_keyring); |
| 281 | key_get(new->process_keyring); |
| 282 | key_get(new->thread_keyring); |
| 283 | key_get(new->request_key_auth); |
| 284 | #endif |
| 285 | |
| 286 | #ifdef CONFIG_SECURITY |
| 287 | new->security = NULL; |
| 288 | #endif |
| 289 | |
| 290 | new->ucounts = get_ucounts(new->ucounts); |
| 291 | if (!new->ucounts) |
| 292 | goto error; |
| 293 | |
| 294 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
| 295 | goto error; |
| 296 | |
| 297 | validate_creds(new); |
| 298 | return new; |
| 299 | |
| 300 | error: |
| 301 | abort_creds(new); |
| 302 | return NULL; |
| 303 | } |
| 304 | EXPORT_SYMBOL(prepare_creds); |
| 305 | |
| 306 | /* |
| 307 | * Prepare credentials for current to perform an execve() |
| 308 | * - The caller must hold ->cred_guard_mutex |
| 309 | */ |
| 310 | struct cred *prepare_exec_creds(void) |
| 311 | { |
| 312 | struct cred *new; |
| 313 | |
| 314 | new = prepare_creds(); |
| 315 | if (!new) |
| 316 | return new; |
| 317 | |
| 318 | #ifdef CONFIG_KEYS |
| 319 | /* newly exec'd tasks don't get a thread keyring */ |
| 320 | key_put(new->thread_keyring); |
| 321 | new->thread_keyring = NULL; |
| 322 | |
| 323 | /* inherit the session keyring; new process keyring */ |
| 324 | key_put(new->process_keyring); |
| 325 | new->process_keyring = NULL; |
| 326 | #endif |
| 327 | |
| 328 | new->suid = new->fsuid = new->euid; |
| 329 | new->sgid = new->fsgid = new->egid; |
| 330 | |
| 331 | return new; |
| 332 | } |
| 333 | |
| 334 | /* |
| 335 | * Copy credentials for the new process created by fork() |
| 336 | * |
| 337 | * We share if we can, but under some circumstances we have to generate a new |
| 338 | * set. |
| 339 | * |
| 340 | * The new process gets the current process's subjective credentials as its |
| 341 | * objective and subjective credentials |
| 342 | */ |
| 343 | int copy_creds(struct task_struct *p, unsigned long clone_flags) |
| 344 | { |
| 345 | struct cred *new; |
| 346 | int ret; |
| 347 | |
| 348 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
| 349 | p->cached_requested_key = NULL; |
| 350 | #endif |
| 351 | |
| 352 | if ( |
| 353 | #ifdef CONFIG_KEYS |
| 354 | !p->cred->thread_keyring && |
| 355 | #endif |
| 356 | clone_flags & CLONE_THREAD |
| 357 | ) { |
| 358 | p->real_cred = get_cred(p->cred); |
| 359 | get_cred(p->cred); |
| 360 | alter_cred_subscribers(p->cred, 2); |
| 361 | kdebug("share_creds(%p{%d,%d})", |
| 362 | p->cred, atomic_read(&p->cred->usage), |
| 363 | read_cred_subscribers(p->cred)); |
| 364 | inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); |
| 365 | return 0; |
| 366 | } |
| 367 | |
| 368 | new = prepare_creds(); |
| 369 | if (!new) |
| 370 | return -ENOMEM; |
| 371 | |
| 372 | if (clone_flags & CLONE_NEWUSER) { |
| 373 | ret = create_user_ns(new); |
| 374 | if (ret < 0) |
| 375 | goto error_put; |
| 376 | ret = set_cred_ucounts(new); |
| 377 | if (ret < 0) |
| 378 | goto error_put; |
| 379 | } |
| 380 | |
| 381 | #ifdef CONFIG_KEYS |
| 382 | /* new threads get their own thread keyrings if their parent already |
| 383 | * had one */ |
| 384 | if (new->thread_keyring) { |
| 385 | key_put(new->thread_keyring); |
| 386 | new->thread_keyring = NULL; |
| 387 | if (clone_flags & CLONE_THREAD) |
| 388 | install_thread_keyring_to_cred(new); |
| 389 | } |
| 390 | |
| 391 | /* The process keyring is only shared between the threads in a process; |
| 392 | * anything outside of those threads doesn't inherit. |
| 393 | */ |
| 394 | if (!(clone_flags & CLONE_THREAD)) { |
| 395 | key_put(new->process_keyring); |
| 396 | new->process_keyring = NULL; |
| 397 | } |
| 398 | #endif |
| 399 | |
| 400 | p->cred = p->real_cred = get_cred(new); |
| 401 | inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); |
| 402 | alter_cred_subscribers(new, 2); |
| 403 | validate_creds(new); |
| 404 | return 0; |
| 405 | |
| 406 | error_put: |
| 407 | put_cred(new); |
| 408 | return ret; |
| 409 | } |
| 410 | |
| 411 | static bool cred_cap_issubset(const struct cred *set, const struct cred *subset) |
| 412 | { |
| 413 | const struct user_namespace *set_ns = set->user_ns; |
| 414 | const struct user_namespace *subset_ns = subset->user_ns; |
| 415 | |
| 416 | /* If the two credentials are in the same user namespace see if |
| 417 | * the capabilities of subset are a subset of set. |
| 418 | */ |
| 419 | if (set_ns == subset_ns) |
| 420 | return cap_issubset(subset->cap_permitted, set->cap_permitted); |
| 421 | |
| 422 | /* The credentials are in a different user namespaces |
| 423 | * therefore one is a subset of the other only if a set is an |
| 424 | * ancestor of subset and set->euid is owner of subset or one |
| 425 | * of subsets ancestors. |
| 426 | */ |
| 427 | for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) { |
| 428 | if ((set_ns == subset_ns->parent) && |
| 429 | uid_eq(subset_ns->owner, set->euid)) |
| 430 | return true; |
| 431 | } |
| 432 | |
| 433 | return false; |
| 434 | } |
| 435 | |
| 436 | /** |
| 437 | * commit_creds - Install new credentials upon the current task |
| 438 | * @new: The credentials to be assigned |
| 439 | * |
| 440 | * Install a new set of credentials to the current task, using RCU to replace |
| 441 | * the old set. Both the objective and the subjective credentials pointers are |
| 442 | * updated. This function may not be called if the subjective credentials are |
| 443 | * in an overridden state. |
| 444 | * |
| 445 | * This function eats the caller's reference to the new credentials. |
| 446 | * |
| 447 | * Always returns 0 thus allowing this function to be tail-called at the end |
| 448 | * of, say, sys_setgid(). |
| 449 | */ |
| 450 | int commit_creds(struct cred *new) |
| 451 | { |
| 452 | struct task_struct *task = current; |
| 453 | const struct cred *old = task->real_cred; |
| 454 | |
| 455 | kdebug("commit_creds(%p{%d,%d})", new, |
| 456 | atomic_read(&new->usage), |
| 457 | read_cred_subscribers(new)); |
| 458 | |
| 459 | BUG_ON(task->cred != old); |
| 460 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 461 | BUG_ON(read_cred_subscribers(old) < 2); |
| 462 | validate_creds(old); |
| 463 | validate_creds(new); |
| 464 | #endif |
| 465 | BUG_ON(atomic_read(&new->usage) < 1); |
| 466 | |
| 467 | get_cred(new); /* we will require a ref for the subj creds too */ |
| 468 | |
| 469 | /* dumpability changes */ |
| 470 | if (!uid_eq(old->euid, new->euid) || |
| 471 | !gid_eq(old->egid, new->egid) || |
| 472 | !uid_eq(old->fsuid, new->fsuid) || |
| 473 | !gid_eq(old->fsgid, new->fsgid) || |
| 474 | !cred_cap_issubset(old, new)) { |
| 475 | if (task->mm) |
| 476 | set_dumpable(task->mm, suid_dumpable); |
| 477 | task->pdeath_signal = 0; |
| 478 | /* |
| 479 | * If a task drops privileges and becomes nondumpable, |
| 480 | * the dumpability change must become visible before |
| 481 | * the credential change; otherwise, a __ptrace_may_access() |
| 482 | * racing with this change may be able to attach to a task it |
| 483 | * shouldn't be able to attach to (as if the task had dropped |
| 484 | * privileges without becoming nondumpable). |
| 485 | * Pairs with a read barrier in __ptrace_may_access(). |
| 486 | */ |
| 487 | smp_wmb(); |
| 488 | } |
| 489 | |
| 490 | /* alter the thread keyring */ |
| 491 | if (!uid_eq(new->fsuid, old->fsuid)) |
| 492 | key_fsuid_changed(new); |
| 493 | if (!gid_eq(new->fsgid, old->fsgid)) |
| 494 | key_fsgid_changed(new); |
| 495 | |
| 496 | /* do it |
| 497 | * RLIMIT_NPROC limits on user->processes have already been checked |
| 498 | * in set_user(). |
| 499 | */ |
| 500 | alter_cred_subscribers(new, 2); |
| 501 | if (new->user != old->user || new->user_ns != old->user_ns) |
| 502 | inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1); |
| 503 | rcu_assign_pointer(task->real_cred, new); |
| 504 | rcu_assign_pointer(task->cred, new); |
| 505 | if (new->user != old->user || new->user_ns != old->user_ns) |
| 506 | dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1); |
| 507 | alter_cred_subscribers(old, -2); |
| 508 | |
| 509 | /* send notifications */ |
| 510 | if (!uid_eq(new->uid, old->uid) || |
| 511 | !uid_eq(new->euid, old->euid) || |
| 512 | !uid_eq(new->suid, old->suid) || |
| 513 | !uid_eq(new->fsuid, old->fsuid)) |
| 514 | proc_id_connector(task, PROC_EVENT_UID); |
| 515 | |
| 516 | if (!gid_eq(new->gid, old->gid) || |
| 517 | !gid_eq(new->egid, old->egid) || |
| 518 | !gid_eq(new->sgid, old->sgid) || |
| 519 | !gid_eq(new->fsgid, old->fsgid)) |
| 520 | proc_id_connector(task, PROC_EVENT_GID); |
| 521 | |
| 522 | /* release the old obj and subj refs both */ |
| 523 | put_cred(old); |
| 524 | put_cred(old); |
| 525 | return 0; |
| 526 | } |
| 527 | EXPORT_SYMBOL(commit_creds); |
| 528 | |
| 529 | /** |
| 530 | * abort_creds - Discard a set of credentials and unlock the current task |
| 531 | * @new: The credentials that were going to be applied |
| 532 | * |
| 533 | * Discard a set of credentials that were under construction and unlock the |
| 534 | * current task. |
| 535 | */ |
| 536 | void abort_creds(struct cred *new) |
| 537 | { |
| 538 | kdebug("abort_creds(%p{%d,%d})", new, |
| 539 | atomic_read(&new->usage), |
| 540 | read_cred_subscribers(new)); |
| 541 | |
| 542 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 543 | BUG_ON(read_cred_subscribers(new) != 0); |
| 544 | #endif |
| 545 | BUG_ON(atomic_read(&new->usage) < 1); |
| 546 | put_cred(new); |
| 547 | } |
| 548 | EXPORT_SYMBOL(abort_creds); |
| 549 | |
| 550 | /** |
| 551 | * override_creds - Override the current process's subjective credentials |
| 552 | * @new: The credentials to be assigned |
| 553 | * |
| 554 | * Install a set of temporary override subjective credentials on the current |
| 555 | * process, returning the old set for later reversion. |
| 556 | */ |
| 557 | const struct cred *override_creds(const struct cred *new) |
| 558 | { |
| 559 | const struct cred *old = current->cred; |
| 560 | |
| 561 | kdebug("override_creds(%p{%d,%d})", new, |
| 562 | atomic_read(&new->usage), |
| 563 | read_cred_subscribers(new)); |
| 564 | |
| 565 | validate_creds(old); |
| 566 | validate_creds(new); |
| 567 | |
| 568 | /* |
| 569 | * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'. |
| 570 | * |
| 571 | * That means that we do not clear the 'non_rcu' flag, since |
| 572 | * we are only installing the cred into the thread-synchronous |
| 573 | * '->cred' pointer, not the '->real_cred' pointer that is |
| 574 | * visible to other threads under RCU. |
| 575 | * |
| 576 | * Also note that we did validate_creds() manually, not depending |
| 577 | * on the validation in 'get_cred()'. |
| 578 | */ |
| 579 | get_new_cred((struct cred *)new); |
| 580 | alter_cred_subscribers(new, 1); |
| 581 | rcu_assign_pointer(current->cred, new); |
| 582 | alter_cred_subscribers(old, -1); |
| 583 | |
| 584 | kdebug("override_creds() = %p{%d,%d}", old, |
| 585 | atomic_read(&old->usage), |
| 586 | read_cred_subscribers(old)); |
| 587 | return old; |
| 588 | } |
| 589 | EXPORT_SYMBOL(override_creds); |
| 590 | |
| 591 | /** |
| 592 | * revert_creds - Revert a temporary subjective credentials override |
| 593 | * @old: The credentials to be restored |
| 594 | * |
| 595 | * Revert a temporary set of override subjective credentials to an old set, |
| 596 | * discarding the override set. |
| 597 | */ |
| 598 | void revert_creds(const struct cred *old) |
| 599 | { |
| 600 | const struct cred *override = current->cred; |
| 601 | |
| 602 | kdebug("revert_creds(%p{%d,%d})", old, |
| 603 | atomic_read(&old->usage), |
| 604 | read_cred_subscribers(old)); |
| 605 | |
| 606 | validate_creds(old); |
| 607 | validate_creds(override); |
| 608 | alter_cred_subscribers(old, 1); |
| 609 | rcu_assign_pointer(current->cred, old); |
| 610 | alter_cred_subscribers(override, -1); |
| 611 | put_cred(override); |
| 612 | } |
| 613 | EXPORT_SYMBOL(revert_creds); |
| 614 | |
| 615 | /** |
| 616 | * cred_fscmp - Compare two credentials with respect to filesystem access. |
| 617 | * @a: The first credential |
| 618 | * @b: The second credential |
| 619 | * |
| 620 | * cred_cmp() will return zero if both credentials have the same |
| 621 | * fsuid, fsgid, and supplementary groups. That is, if they will both |
| 622 | * provide the same access to files based on mode/uid/gid. |
| 623 | * If the credentials are different, then either -1 or 1 will |
| 624 | * be returned depending on whether @a comes before or after @b |
| 625 | * respectively in an arbitrary, but stable, ordering of credentials. |
| 626 | * |
| 627 | * Return: -1, 0, or 1 depending on comparison |
| 628 | */ |
| 629 | int cred_fscmp(const struct cred *a, const struct cred *b) |
| 630 | { |
| 631 | struct group_info *ga, *gb; |
| 632 | int g; |
| 633 | |
| 634 | if (a == b) |
| 635 | return 0; |
| 636 | if (uid_lt(a->fsuid, b->fsuid)) |
| 637 | return -1; |
| 638 | if (uid_gt(a->fsuid, b->fsuid)) |
| 639 | return 1; |
| 640 | |
| 641 | if (gid_lt(a->fsgid, b->fsgid)) |
| 642 | return -1; |
| 643 | if (gid_gt(a->fsgid, b->fsgid)) |
| 644 | return 1; |
| 645 | |
| 646 | ga = a->group_info; |
| 647 | gb = b->group_info; |
| 648 | if (ga == gb) |
| 649 | return 0; |
| 650 | if (ga == NULL) |
| 651 | return -1; |
| 652 | if (gb == NULL) |
| 653 | return 1; |
| 654 | if (ga->ngroups < gb->ngroups) |
| 655 | return -1; |
| 656 | if (ga->ngroups > gb->ngroups) |
| 657 | return 1; |
| 658 | |
| 659 | for (g = 0; g < ga->ngroups; g++) { |
| 660 | if (gid_lt(ga->gid[g], gb->gid[g])) |
| 661 | return -1; |
| 662 | if (gid_gt(ga->gid[g], gb->gid[g])) |
| 663 | return 1; |
| 664 | } |
| 665 | return 0; |
| 666 | } |
| 667 | EXPORT_SYMBOL(cred_fscmp); |
| 668 | |
| 669 | int set_cred_ucounts(struct cred *new) |
| 670 | { |
| 671 | struct ucounts *new_ucounts, *old_ucounts = new->ucounts; |
| 672 | |
| 673 | /* |
| 674 | * This optimization is needed because alloc_ucounts() uses locks |
| 675 | * for table lookups. |
| 676 | */ |
| 677 | if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid)) |
| 678 | return 0; |
| 679 | |
| 680 | if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid))) |
| 681 | return -EAGAIN; |
| 682 | |
| 683 | new->ucounts = new_ucounts; |
| 684 | put_ucounts(old_ucounts); |
| 685 | |
| 686 | return 0; |
| 687 | } |
| 688 | |
| 689 | /* |
| 690 | * initialise the credentials stuff |
| 691 | */ |
| 692 | void __init cred_init(void) |
| 693 | { |
| 694 | /* allocate a slab in which we can store credentials */ |
| 695 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, |
| 696 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); |
| 697 | } |
| 698 | |
| 699 | /** |
| 700 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service |
| 701 | * @daemon: A userspace daemon to be used as a reference |
| 702 | * |
| 703 | * Prepare a set of credentials for a kernel service. This can then be used to |
| 704 | * override a task's own credentials so that work can be done on behalf of that |
| 705 | * task that requires a different subjective context. |
| 706 | * |
| 707 | * @daemon is used to provide a base cred, with the security data derived from |
| 708 | * that; if this is "&init_task", they'll be set to 0, no groups, full |
| 709 | * capabilities, and no keys. |
| 710 | * |
| 711 | * The caller may change these controls afterwards if desired. |
| 712 | * |
| 713 | * Returns the new credentials or NULL if out of memory. |
| 714 | */ |
| 715 | struct cred *prepare_kernel_cred(struct task_struct *daemon) |
| 716 | { |
| 717 | const struct cred *old; |
| 718 | struct cred *new; |
| 719 | |
| 720 | if (WARN_ON_ONCE(!daemon)) |
| 721 | return NULL; |
| 722 | |
| 723 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); |
| 724 | if (!new) |
| 725 | return NULL; |
| 726 | |
| 727 | kdebug("prepare_kernel_cred() alloc %p", new); |
| 728 | |
| 729 | old = get_task_cred(daemon); |
| 730 | validate_creds(old); |
| 731 | |
| 732 | *new = *old; |
| 733 | new->non_rcu = 0; |
| 734 | atomic_set(&new->usage, 1); |
| 735 | set_cred_subscribers(new, 0); |
| 736 | get_uid(new->user); |
| 737 | get_user_ns(new->user_ns); |
| 738 | get_group_info(new->group_info); |
| 739 | |
| 740 | #ifdef CONFIG_KEYS |
| 741 | new->session_keyring = NULL; |
| 742 | new->process_keyring = NULL; |
| 743 | new->thread_keyring = NULL; |
| 744 | new->request_key_auth = NULL; |
| 745 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
| 746 | #endif |
| 747 | |
| 748 | #ifdef CONFIG_SECURITY |
| 749 | new->security = NULL; |
| 750 | #endif |
| 751 | new->ucounts = get_ucounts(new->ucounts); |
| 752 | if (!new->ucounts) |
| 753 | goto error; |
| 754 | |
| 755 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
| 756 | goto error; |
| 757 | |
| 758 | put_cred(old); |
| 759 | validate_creds(new); |
| 760 | return new; |
| 761 | |
| 762 | error: |
| 763 | put_cred(new); |
| 764 | put_cred(old); |
| 765 | return NULL; |
| 766 | } |
| 767 | EXPORT_SYMBOL(prepare_kernel_cred); |
| 768 | |
| 769 | /** |
| 770 | * set_security_override - Set the security ID in a set of credentials |
| 771 | * @new: The credentials to alter |
| 772 | * @secid: The LSM security ID to set |
| 773 | * |
| 774 | * Set the LSM security ID in a set of credentials so that the subjective |
| 775 | * security is overridden when an alternative set of credentials is used. |
| 776 | */ |
| 777 | int set_security_override(struct cred *new, u32 secid) |
| 778 | { |
| 779 | return security_kernel_act_as(new, secid); |
| 780 | } |
| 781 | EXPORT_SYMBOL(set_security_override); |
| 782 | |
| 783 | /** |
| 784 | * set_security_override_from_ctx - Set the security ID in a set of credentials |
| 785 | * @new: The credentials to alter |
| 786 | * @secctx: The LSM security context to generate the security ID from. |
| 787 | * |
| 788 | * Set the LSM security ID in a set of credentials so that the subjective |
| 789 | * security is overridden when an alternative set of credentials is used. The |
| 790 | * security ID is specified in string form as a security context to be |
| 791 | * interpreted by the LSM. |
| 792 | */ |
| 793 | int set_security_override_from_ctx(struct cred *new, const char *secctx) |
| 794 | { |
| 795 | u32 secid; |
| 796 | int ret; |
| 797 | |
| 798 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); |
| 799 | if (ret < 0) |
| 800 | return ret; |
| 801 | |
| 802 | return set_security_override(new, secid); |
| 803 | } |
| 804 | EXPORT_SYMBOL(set_security_override_from_ctx); |
| 805 | |
| 806 | /** |
| 807 | * set_create_files_as - Set the LSM file create context in a set of credentials |
| 808 | * @new: The credentials to alter |
| 809 | * @inode: The inode to take the context from |
| 810 | * |
| 811 | * Change the LSM file creation context in a set of credentials to be the same |
| 812 | * as the object context of the specified inode, so that the new inodes have |
| 813 | * the same MAC context as that inode. |
| 814 | */ |
| 815 | int set_create_files_as(struct cred *new, struct inode *inode) |
| 816 | { |
| 817 | if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) |
| 818 | return -EINVAL; |
| 819 | new->fsuid = inode->i_uid; |
| 820 | new->fsgid = inode->i_gid; |
| 821 | return security_kernel_create_files_as(new, inode); |
| 822 | } |
| 823 | EXPORT_SYMBOL(set_create_files_as); |
| 824 | |
| 825 | #ifdef CONFIG_DEBUG_CREDENTIALS |
| 826 | |
| 827 | bool creds_are_invalid(const struct cred *cred) |
| 828 | { |
| 829 | if (cred->magic != CRED_MAGIC) |
| 830 | return true; |
| 831 | return false; |
| 832 | } |
| 833 | EXPORT_SYMBOL(creds_are_invalid); |
| 834 | |
| 835 | /* |
| 836 | * dump invalid credentials |
| 837 | */ |
| 838 | static void dump_invalid_creds(const struct cred *cred, const char *label, |
| 839 | const struct task_struct *tsk) |
| 840 | { |
| 841 | pr_err("%s credentials: %p %s%s%s\n", |
| 842 | label, cred, |
| 843 | cred == &init_cred ? "[init]" : "", |
| 844 | cred == tsk->real_cred ? "[real]" : "", |
| 845 | cred == tsk->cred ? "[eff]" : ""); |
| 846 | pr_err("->magic=%x, put_addr=%p\n", |
| 847 | cred->magic, cred->put_addr); |
| 848 | pr_err("->usage=%d, subscr=%d\n", |
| 849 | atomic_read(&cred->usage), |
| 850 | read_cred_subscribers(cred)); |
| 851 | pr_err("->*uid = { %d,%d,%d,%d }\n", |
| 852 | from_kuid_munged(&init_user_ns, cred->uid), |
| 853 | from_kuid_munged(&init_user_ns, cred->euid), |
| 854 | from_kuid_munged(&init_user_ns, cred->suid), |
| 855 | from_kuid_munged(&init_user_ns, cred->fsuid)); |
| 856 | pr_err("->*gid = { %d,%d,%d,%d }\n", |
| 857 | from_kgid_munged(&init_user_ns, cred->gid), |
| 858 | from_kgid_munged(&init_user_ns, cred->egid), |
| 859 | from_kgid_munged(&init_user_ns, cred->sgid), |
| 860 | from_kgid_munged(&init_user_ns, cred->fsgid)); |
| 861 | #ifdef CONFIG_SECURITY |
| 862 | pr_err("->security is %p\n", cred->security); |
| 863 | if ((unsigned long) cred->security >= PAGE_SIZE && |
| 864 | (((unsigned long) cred->security & 0xffffff00) != |
| 865 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) |
| 866 | pr_err("->security {%x, %x}\n", |
| 867 | ((u32*)cred->security)[0], |
| 868 | ((u32*)cred->security)[1]); |
| 869 | #endif |
| 870 | } |
| 871 | |
| 872 | /* |
| 873 | * report use of invalid credentials |
| 874 | */ |
| 875 | void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line) |
| 876 | { |
| 877 | pr_err("Invalid credentials\n"); |
| 878 | pr_err("At %s:%u\n", file, line); |
| 879 | dump_invalid_creds(cred, "Specified", current); |
| 880 | BUG(); |
| 881 | } |
| 882 | EXPORT_SYMBOL(__invalid_creds); |
| 883 | |
| 884 | /* |
| 885 | * check the credentials on a process |
| 886 | */ |
| 887 | void __validate_process_creds(struct task_struct *tsk, |
| 888 | const char *file, unsigned line) |
| 889 | { |
| 890 | if (tsk->cred == tsk->real_cred) { |
| 891 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || |
| 892 | creds_are_invalid(tsk->cred))) |
| 893 | goto invalid_creds; |
| 894 | } else { |
| 895 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || |
| 896 | read_cred_subscribers(tsk->cred) < 1 || |
| 897 | creds_are_invalid(tsk->real_cred) || |
| 898 | creds_are_invalid(tsk->cred))) |
| 899 | goto invalid_creds; |
| 900 | } |
| 901 | return; |
| 902 | |
| 903 | invalid_creds: |
| 904 | pr_err("Invalid process credentials\n"); |
| 905 | pr_err("At %s:%u\n", file, line); |
| 906 | |
| 907 | dump_invalid_creds(tsk->real_cred, "Real", tsk); |
| 908 | if (tsk->cred != tsk->real_cred) |
| 909 | dump_invalid_creds(tsk->cred, "Effective", tsk); |
| 910 | else |
| 911 | pr_err("Effective creds == Real creds\n"); |
| 912 | BUG(); |
| 913 | } |
| 914 | EXPORT_SYMBOL(__validate_process_creds); |
| 915 | |
| 916 | /* |
| 917 | * check creds for do_exit() |
| 918 | */ |
| 919 | void validate_creds_for_do_exit(struct task_struct *tsk) |
| 920 | { |
| 921 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", |
| 922 | tsk->real_cred, tsk->cred, |
| 923 | atomic_read(&tsk->cred->usage), |
| 924 | read_cred_subscribers(tsk->cred)); |
| 925 | |
| 926 | __validate_process_creds(tsk, __FILE__, __LINE__); |
| 927 | } |
| 928 | |
| 929 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |