1 /* Common capabilities, needed by capability.o. 2 * 3 * This program is free software; you can redistribute it and/or modify 4 * it under the terms of the GNU General Public License as published by 5 * the Free Software Foundation; either version 2 of the License, or 6 * (at your option) any later version. 7 * 8 */ 9 10 #include <linux/capability.h> 11 #include <linux/audit.h> 12 #include <linux/module.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/lsm_hooks.h> 16 #include <linux/file.h> 17 #include <linux/mm.h> 18 #include <linux/mman.h> 19 #include <linux/pagemap.h> 20 #include <linux/swap.h> 21 #include <linux/skbuff.h> 22 #include <linux/netlink.h> 23 #include <linux/ptrace.h> 24 #include <linux/xattr.h> 25 #include <linux/hugetlb.h> 26 #include <linux/mount.h> 27 #include <linux/sched.h> 28 #include <linux/prctl.h> 29 #include <linux/securebits.h> 30 #include <linux/user_namespace.h> 31 #include <linux/binfmts.h> 32 #include <linux/personality.h> 33 34 /* 35 * If a non-root user executes a setuid-root binary in 36 * !secure(SECURE_NOROOT) mode, then we raise capabilities. 37 * However if fE is also set, then the intent is for only 38 * the file capabilities to be applied, and the setuid-root 39 * bit is left on either to change the uid (plausible) or 40 * to get full privilege on a kernel without file capabilities 41 * support. So in that case we do not raise capabilities. 42 * 43 * Warn if that happens, once per boot. 44 */ 45 static void warn_setuid_and_fcaps_mixed(const char *fname) 46 { 47 static int warned; 48 if (!warned) { 49 printk(KERN_INFO "warning: `%s' has both setuid-root and" 50 " effective capabilities. Therefore not raising all" 51 " capabilities.\n", fname); 52 warned = 1; 53 } 54 } 55 56 /** 57 * cap_capable - Determine whether a task has a particular effective capability 58 * @cred: The credentials to use 59 * @ns: The user namespace in which we need the capability 60 * @cap: The capability to check for 61 * @audit: Whether to write an audit message or not 62 * 63 * Determine whether the nominated task has the specified capability amongst 64 * its effective set, returning 0 if it does, -ve if it does not. 65 * 66 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() 67 * and has_capability() functions. That is, it has the reverse semantics: 68 * cap_has_capability() returns 0 when a task has a capability, but the 69 * kernel's capable() and has_capability() returns 1 for this case. 70 */ 71 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, 72 int cap, int audit) 73 { 74 struct user_namespace *ns = targ_ns; 75 76 /* See if cred has the capability in the target user namespace 77 * by examining the target user namespace and all of the target 78 * user namespace's parents. 79 */ 80 for (;;) { 81 /* Do we have the necessary capabilities? */ 82 if (ns == cred->user_ns) 83 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 84 85 /* Have we tried all of the parent namespaces? */ 86 if (ns == &init_user_ns) 87 return -EPERM; 88 89 /* 90 * The owner of the user namespace in the parent of the 91 * user namespace has all caps. 92 */ 93 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) 94 return 0; 95 96 /* 97 * If you have a capability in a parent user ns, then you have 98 * it over all children user namespaces as well. 99 */ 100 ns = ns->parent; 101 } 102 103 /* We never get here */ 104 } 105 106 /** 107 * cap_settime - Determine whether the current process may set the system clock 108 * @ts: The time to set 109 * @tz: The timezone to set 110 * 111 * Determine whether the current process may set the system clock and timezone 112 * information, returning 0 if permission granted, -ve if denied. 113 */ 114 int cap_settime(const struct timespec *ts, const struct timezone *tz) 115 { 116 if (!capable(CAP_SYS_TIME)) 117 return -EPERM; 118 return 0; 119 } 120 121 /** 122 * cap_ptrace_access_check - Determine whether the current process may access 123 * another 124 * @child: The process to be accessed 125 * @mode: The mode of attachment. 126 * 127 * If we are in the same or an ancestor user_ns and have all the target 128 * task's capabilities, then ptrace access is allowed. 129 * If we have the ptrace capability to the target user_ns, then ptrace 130 * access is allowed. 131 * Else denied. 132 * 133 * Determine whether a process may access another, returning 0 if permission 134 * granted, -ve if denied. 135 */ 136 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 137 { 138 int ret = 0; 139 const struct cred *cred, *child_cred; 140 141 rcu_read_lock(); 142 cred = current_cred(); 143 child_cred = __task_cred(child); 144 if (cred->user_ns == child_cred->user_ns && 145 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 146 goto out; 147 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE)) 148 goto out; 149 ret = -EPERM; 150 out: 151 rcu_read_unlock(); 152 return ret; 153 } 154 155 /** 156 * cap_ptrace_traceme - Determine whether another process may trace the current 157 * @parent: The task proposed to be the tracer 158 * 159 * If parent is in the same or an ancestor user_ns and has all current's 160 * capabilities, then ptrace access is allowed. 161 * If parent has the ptrace capability to current's user_ns, then ptrace 162 * access is allowed. 163 * Else denied. 164 * 165 * Determine whether the nominated task is permitted to trace the current 166 * process, returning 0 if permission is granted, -ve if denied. 167 */ 168 int cap_ptrace_traceme(struct task_struct *parent) 169 { 170 int ret = 0; 171 const struct cred *cred, *child_cred; 172 173 rcu_read_lock(); 174 cred = __task_cred(parent); 175 child_cred = current_cred(); 176 if (cred->user_ns == child_cred->user_ns && 177 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 178 goto out; 179 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE)) 180 goto out; 181 ret = -EPERM; 182 out: 183 rcu_read_unlock(); 184 return ret; 185 } 186 187 /** 188 * cap_capget - Retrieve a task's capability sets 189 * @target: The task from which to retrieve the capability sets 190 * @effective: The place to record the effective set 191 * @inheritable: The place to record the inheritable set 192 * @permitted: The place to record the permitted set 193 * 194 * This function retrieves the capabilities of the nominated task and returns 195 * them to the caller. 196 */ 197 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 198 kernel_cap_t *inheritable, kernel_cap_t *permitted) 199 { 200 const struct cred *cred; 201 202 /* Derived from kernel/capability.c:sys_capget. */ 203 rcu_read_lock(); 204 cred = __task_cred(target); 205 *effective = cred->cap_effective; 206 *inheritable = cred->cap_inheritable; 207 *permitted = cred->cap_permitted; 208 rcu_read_unlock(); 209 return 0; 210 } 211 212 /* 213 * Determine whether the inheritable capabilities are limited to the old 214 * permitted set. Returns 1 if they are limited, 0 if they are not. 215 */ 216 static inline int cap_inh_is_capped(void) 217 { 218 219 /* they are so limited unless the current task has the CAP_SETPCAP 220 * capability 221 */ 222 if (cap_capable(current_cred(), current_cred()->user_ns, 223 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) 224 return 0; 225 return 1; 226 } 227 228 /** 229 * cap_capset - Validate and apply proposed changes to current's capabilities 230 * @new: The proposed new credentials; alterations should be made here 231 * @old: The current task's current credentials 232 * @effective: A pointer to the proposed new effective capabilities set 233 * @inheritable: A pointer to the proposed new inheritable capabilities set 234 * @permitted: A pointer to the proposed new permitted capabilities set 235 * 236 * This function validates and applies a proposed mass change to the current 237 * process's capability sets. The changes are made to the proposed new 238 * credentials, and assuming no error, will be committed by the caller of LSM. 239 */ 240 int cap_capset(struct cred *new, 241 const struct cred *old, 242 const kernel_cap_t *effective, 243 const kernel_cap_t *inheritable, 244 const kernel_cap_t *permitted) 245 { 246 if (cap_inh_is_capped() && 247 !cap_issubset(*inheritable, 248 cap_combine(old->cap_inheritable, 249 old->cap_permitted))) 250 /* incapable of using this inheritable set */ 251 return -EPERM; 252 253 if (!cap_issubset(*inheritable, 254 cap_combine(old->cap_inheritable, 255 old->cap_bset))) 256 /* no new pI capabilities outside bounding set */ 257 return -EPERM; 258 259 /* verify restrictions on target's new Permitted set */ 260 if (!cap_issubset(*permitted, old->cap_permitted)) 261 return -EPERM; 262 263 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 264 if (!cap_issubset(*effective, *permitted)) 265 return -EPERM; 266 267 new->cap_effective = *effective; 268 new->cap_inheritable = *inheritable; 269 new->cap_permitted = *permitted; 270 return 0; 271 } 272 273 /* 274 * Clear proposed capability sets for execve(). 275 */ 276 static inline void bprm_clear_caps(struct linux_binprm *bprm) 277 { 278 cap_clear(bprm->cred->cap_permitted); 279 bprm->cap_effective = false; 280 } 281 282 /** 283 * cap_inode_need_killpriv - Determine if inode change affects privileges 284 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 285 * 286 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 287 * affects the security markings on that inode, and if it is, should 288 * inode_killpriv() be invoked or the change rejected? 289 * 290 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 291 * -ve to deny the change. 292 */ 293 int cap_inode_need_killpriv(struct dentry *dentry) 294 { 295 struct inode *inode = d_backing_inode(dentry); 296 int error; 297 298 if (!inode->i_op->getxattr) 299 return 0; 300 301 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 302 if (error <= 0) 303 return 0; 304 return 1; 305 } 306 307 /** 308 * cap_inode_killpriv - Erase the security markings on an inode 309 * @dentry: The inode/dentry to alter 310 * 311 * Erase the privilege-enhancing security markings on an inode. 312 * 313 * Returns 0 if successful, -ve on error. 314 */ 315 int cap_inode_killpriv(struct dentry *dentry) 316 { 317 struct inode *inode = d_backing_inode(dentry); 318 319 if (!inode->i_op->removexattr) 320 return 0; 321 322 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 323 } 324 325 /* 326 * Calculate the new process capability sets from the capability sets attached 327 * to a file. 328 */ 329 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 330 struct linux_binprm *bprm, 331 bool *effective, 332 bool *has_cap) 333 { 334 struct cred *new = bprm->cred; 335 unsigned i; 336 int ret = 0; 337 338 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 339 *effective = true; 340 341 if (caps->magic_etc & VFS_CAP_REVISION_MASK) 342 *has_cap = true; 343 344 CAP_FOR_EACH_U32(i) { 345 __u32 permitted = caps->permitted.cap[i]; 346 __u32 inheritable = caps->inheritable.cap[i]; 347 348 /* 349 * pP' = (X & fP) | (pI & fI) 350 */ 351 new->cap_permitted.cap[i] = 352 (new->cap_bset.cap[i] & permitted) | 353 (new->cap_inheritable.cap[i] & inheritable); 354 355 if (permitted & ~new->cap_permitted.cap[i]) 356 /* insufficient to execute correctly */ 357 ret = -EPERM; 358 } 359 360 /* 361 * For legacy apps, with no internal support for recognizing they 362 * do not have enough capabilities, we return an error if they are 363 * missing some "forced" (aka file-permitted) capabilities. 364 */ 365 return *effective ? ret : 0; 366 } 367 368 /* 369 * Extract the on-exec-apply capability sets for an executable file. 370 */ 371 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 372 { 373 struct inode *inode = d_backing_inode(dentry); 374 __u32 magic_etc; 375 unsigned tocopy, i; 376 int size; 377 struct vfs_cap_data caps; 378 379 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 380 381 if (!inode || !inode->i_op->getxattr) 382 return -ENODATA; 383 384 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 385 XATTR_CAPS_SZ); 386 if (size == -ENODATA || size == -EOPNOTSUPP) 387 /* no data, that's ok */ 388 return -ENODATA; 389 if (size < 0) 390 return size; 391 392 if (size < sizeof(magic_etc)) 393 return -EINVAL; 394 395 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 396 397 switch (magic_etc & VFS_CAP_REVISION_MASK) { 398 case VFS_CAP_REVISION_1: 399 if (size != XATTR_CAPS_SZ_1) 400 return -EINVAL; 401 tocopy = VFS_CAP_U32_1; 402 break; 403 case VFS_CAP_REVISION_2: 404 if (size != XATTR_CAPS_SZ_2) 405 return -EINVAL; 406 tocopy = VFS_CAP_U32_2; 407 break; 408 default: 409 return -EINVAL; 410 } 411 412 CAP_FOR_EACH_U32(i) { 413 if (i >= tocopy) 414 break; 415 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 416 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 417 } 418 419 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; 420 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; 421 422 return 0; 423 } 424 425 /* 426 * Attempt to get the on-exec apply capability sets for an executable file from 427 * its xattrs and, if present, apply them to the proposed credentials being 428 * constructed by execve(). 429 */ 430 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) 431 { 432 int rc = 0; 433 struct cpu_vfs_cap_data vcaps; 434 435 bprm_clear_caps(bprm); 436 437 if (!file_caps_enabled) 438 return 0; 439 440 if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) 441 return 0; 442 443 rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps); 444 if (rc < 0) { 445 if (rc == -EINVAL) 446 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 447 __func__, rc, bprm->filename); 448 else if (rc == -ENODATA) 449 rc = 0; 450 goto out; 451 } 452 453 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); 454 if (rc == -EINVAL) 455 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 456 __func__, rc, bprm->filename); 457 458 out: 459 if (rc) 460 bprm_clear_caps(bprm); 461 462 return rc; 463 } 464 465 /** 466 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 467 * @bprm: The execution parameters, including the proposed creds 468 * 469 * Set up the proposed credentials for a new execution context being 470 * constructed by execve(). The proposed creds in @bprm->cred is altered, 471 * which won't take effect immediately. Returns 0 if successful, -ve on error. 472 */ 473 int cap_bprm_set_creds(struct linux_binprm *bprm) 474 { 475 const struct cred *old = current_cred(); 476 struct cred *new = bprm->cred; 477 bool effective, has_cap = false; 478 int ret; 479 kuid_t root_uid; 480 481 effective = false; 482 ret = get_file_caps(bprm, &effective, &has_cap); 483 if (ret < 0) 484 return ret; 485 486 root_uid = make_kuid(new->user_ns, 0); 487 488 if (!issecure(SECURE_NOROOT)) { 489 /* 490 * If the legacy file capability is set, then don't set privs 491 * for a setuid root binary run by a non-root user. Do set it 492 * for a root user just to cause least surprise to an admin. 493 */ 494 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { 495 warn_setuid_and_fcaps_mixed(bprm->filename); 496 goto skip; 497 } 498 /* 499 * To support inheritance of root-permissions and suid-root 500 * executables under compatibility mode, we override the 501 * capability sets for the file. 502 * 503 * If only the real uid is 0, we do not set the effective bit. 504 */ 505 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { 506 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 507 new->cap_permitted = cap_combine(old->cap_bset, 508 old->cap_inheritable); 509 } 510 if (uid_eq(new->euid, root_uid)) 511 effective = true; 512 } 513 skip: 514 515 /* if we have fs caps, clear dangerous personality flags */ 516 if (!cap_issubset(new->cap_permitted, old->cap_permitted)) 517 bprm->per_clear |= PER_CLEAR_ON_SETID; 518 519 520 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 521 * credentials unless they have the appropriate permit. 522 * 523 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. 524 */ 525 if ((!uid_eq(new->euid, old->uid) || 526 !gid_eq(new->egid, old->gid) || 527 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 528 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 529 /* downgrade; they get no more than they had, and maybe less */ 530 if (!capable(CAP_SETUID) || 531 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { 532 new->euid = new->uid; 533 new->egid = new->gid; 534 } 535 new->cap_permitted = cap_intersect(new->cap_permitted, 536 old->cap_permitted); 537 } 538 539 new->suid = new->fsuid = new->euid; 540 new->sgid = new->fsgid = new->egid; 541 542 if (effective) 543 new->cap_effective = new->cap_permitted; 544 else 545 cap_clear(new->cap_effective); 546 bprm->cap_effective = effective; 547 548 /* 549 * Audit candidate if current->cap_effective is set 550 * 551 * We do not bother to audit if 3 things are true: 552 * 1) cap_effective has all caps 553 * 2) we are root 554 * 3) root is supposed to have all caps (SECURE_NOROOT) 555 * Since this is just a normal root execing a process. 556 * 557 * Number 1 above might fail if you don't have a full bset, but I think 558 * that is interesting information to audit. 559 */ 560 if (!cap_isclear(new->cap_effective)) { 561 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 562 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) || 563 issecure(SECURE_NOROOT)) { 564 ret = audit_log_bprm_fcaps(bprm, new, old); 565 if (ret < 0) 566 return ret; 567 } 568 } 569 570 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 571 return 0; 572 } 573 574 /** 575 * cap_bprm_secureexec - Determine whether a secure execution is required 576 * @bprm: The execution parameters 577 * 578 * Determine whether a secure execution is required, return 1 if it is, and 0 579 * if it is not. 580 * 581 * The credentials have been committed by this point, and so are no longer 582 * available through @bprm->cred. 583 */ 584 int cap_bprm_secureexec(struct linux_binprm *bprm) 585 { 586 const struct cred *cred = current_cred(); 587 kuid_t root_uid = make_kuid(cred->user_ns, 0); 588 589 if (!uid_eq(cred->uid, root_uid)) { 590 if (bprm->cap_effective) 591 return 1; 592 if (!cap_isclear(cred->cap_permitted)) 593 return 1; 594 } 595 596 return (!uid_eq(cred->euid, cred->uid) || 597 !gid_eq(cred->egid, cred->gid)); 598 } 599 600 /** 601 * cap_inode_setxattr - Determine whether an xattr may be altered 602 * @dentry: The inode/dentry being altered 603 * @name: The name of the xattr to be changed 604 * @value: The value that the xattr will be changed to 605 * @size: The size of value 606 * @flags: The replacement flag 607 * 608 * Determine whether an xattr may be altered or set on an inode, returning 0 if 609 * permission is granted, -ve if denied. 610 * 611 * This is used to make sure security xattrs don't get updated or set by those 612 * who aren't privileged to do so. 613 */ 614 int cap_inode_setxattr(struct dentry *dentry, const char *name, 615 const void *value, size_t size, int flags) 616 { 617 if (!strcmp(name, XATTR_NAME_CAPS)) { 618 if (!capable(CAP_SETFCAP)) 619 return -EPERM; 620 return 0; 621 } 622 623 if (!strncmp(name, XATTR_SECURITY_PREFIX, 624 sizeof(XATTR_SECURITY_PREFIX) - 1) && 625 !capable(CAP_SYS_ADMIN)) 626 return -EPERM; 627 return 0; 628 } 629 630 /** 631 * cap_inode_removexattr - Determine whether an xattr may be removed 632 * @dentry: The inode/dentry being altered 633 * @name: The name of the xattr to be changed 634 * 635 * Determine whether an xattr may be removed from an inode, returning 0 if 636 * permission is granted, -ve if denied. 637 * 638 * This is used to make sure security xattrs don't get removed by those who 639 * aren't privileged to remove them. 640 */ 641 int cap_inode_removexattr(struct dentry *dentry, const char *name) 642 { 643 if (!strcmp(name, XATTR_NAME_CAPS)) { 644 if (!capable(CAP_SETFCAP)) 645 return -EPERM; 646 return 0; 647 } 648 649 if (!strncmp(name, XATTR_SECURITY_PREFIX, 650 sizeof(XATTR_SECURITY_PREFIX) - 1) && 651 !capable(CAP_SYS_ADMIN)) 652 return -EPERM; 653 return 0; 654 } 655 656 /* 657 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 658 * a process after a call to setuid, setreuid, or setresuid. 659 * 660 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 661 * {r,e,s}uid != 0, the permitted and effective capabilities are 662 * cleared. 663 * 664 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 665 * capabilities of the process are cleared. 666 * 667 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 668 * capabilities are set to the permitted capabilities. 669 * 670 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 671 * never happen. 672 * 673 * -astor 674 * 675 * cevans - New behaviour, Oct '99 676 * A process may, via prctl(), elect to keep its capabilities when it 677 * calls setuid() and switches away from uid==0. Both permitted and 678 * effective sets will be retained. 679 * Without this change, it was impossible for a daemon to drop only some 680 * of its privilege. The call to setuid(!=0) would drop all privileges! 681 * Keeping uid 0 is not an option because uid 0 owns too many vital 682 * files.. 683 * Thanks to Olaf Kirch and Peter Benie for spotting this. 684 */ 685 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 686 { 687 kuid_t root_uid = make_kuid(old->user_ns, 0); 688 689 if ((uid_eq(old->uid, root_uid) || 690 uid_eq(old->euid, root_uid) || 691 uid_eq(old->suid, root_uid)) && 692 (!uid_eq(new->uid, root_uid) && 693 !uid_eq(new->euid, root_uid) && 694 !uid_eq(new->suid, root_uid)) && 695 !issecure(SECURE_KEEP_CAPS)) { 696 cap_clear(new->cap_permitted); 697 cap_clear(new->cap_effective); 698 } 699 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) 700 cap_clear(new->cap_effective); 701 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) 702 new->cap_effective = new->cap_permitted; 703 } 704 705 /** 706 * cap_task_fix_setuid - Fix up the results of setuid() call 707 * @new: The proposed credentials 708 * @old: The current task's current credentials 709 * @flags: Indications of what has changed 710 * 711 * Fix up the results of setuid() call before the credential changes are 712 * actually applied, returning 0 to grant the changes, -ve to deny them. 713 */ 714 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 715 { 716 switch (flags) { 717 case LSM_SETID_RE: 718 case LSM_SETID_ID: 719 case LSM_SETID_RES: 720 /* juggle the capabilities to follow [RES]UID changes unless 721 * otherwise suppressed */ 722 if (!issecure(SECURE_NO_SETUID_FIXUP)) 723 cap_emulate_setxuid(new, old); 724 break; 725 726 case LSM_SETID_FS: 727 /* juggle the capabilties to follow FSUID changes, unless 728 * otherwise suppressed 729 * 730 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 731 * if not, we might be a bit too harsh here. 732 */ 733 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 734 kuid_t root_uid = make_kuid(old->user_ns, 0); 735 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) 736 new->cap_effective = 737 cap_drop_fs_set(new->cap_effective); 738 739 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) 740 new->cap_effective = 741 cap_raise_fs_set(new->cap_effective, 742 new->cap_permitted); 743 } 744 break; 745 746 default: 747 return -EINVAL; 748 } 749 750 return 0; 751 } 752 753 /* 754 * Rationale: code calling task_setscheduler, task_setioprio, and 755 * task_setnice, assumes that 756 * . if capable(cap_sys_nice), then those actions should be allowed 757 * . if not capable(cap_sys_nice), but acting on your own processes, 758 * then those actions should be allowed 759 * This is insufficient now since you can call code without suid, but 760 * yet with increased caps. 761 * So we check for increased caps on the target process. 762 */ 763 static int cap_safe_nice(struct task_struct *p) 764 { 765 int is_subset, ret = 0; 766 767 rcu_read_lock(); 768 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 769 current_cred()->cap_permitted); 770 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) 771 ret = -EPERM; 772 rcu_read_unlock(); 773 774 return ret; 775 } 776 777 /** 778 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 779 * @p: The task to affect 780 * 781 * Detemine if the requested scheduler policy change is permitted for the 782 * specified task, returning 0 if permission is granted, -ve if denied. 783 */ 784 int cap_task_setscheduler(struct task_struct *p) 785 { 786 return cap_safe_nice(p); 787 } 788 789 /** 790 * cap_task_ioprio - Detemine if I/O priority change is permitted 791 * @p: The task to affect 792 * @ioprio: The I/O priority to set 793 * 794 * Detemine if the requested I/O priority change is permitted for the specified 795 * task, returning 0 if permission is granted, -ve if denied. 796 */ 797 int cap_task_setioprio(struct task_struct *p, int ioprio) 798 { 799 return cap_safe_nice(p); 800 } 801 802 /** 803 * cap_task_ioprio - Detemine if task priority change is permitted 804 * @p: The task to affect 805 * @nice: The nice value to set 806 * 807 * Detemine if the requested task priority change is permitted for the 808 * specified task, returning 0 if permission is granted, -ve if denied. 809 */ 810 int cap_task_setnice(struct task_struct *p, int nice) 811 { 812 return cap_safe_nice(p); 813 } 814 815 /* 816 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 817 * the current task's bounding set. Returns 0 on success, -ve on error. 818 */ 819 static int cap_prctl_drop(unsigned long cap) 820 { 821 struct cred *new; 822 823 if (!ns_capable(current_user_ns(), CAP_SETPCAP)) 824 return -EPERM; 825 if (!cap_valid(cap)) 826 return -EINVAL; 827 828 new = prepare_creds(); 829 if (!new) 830 return -ENOMEM; 831 cap_lower(new->cap_bset, cap); 832 return commit_creds(new); 833 } 834 835 /** 836 * cap_task_prctl - Implement process control functions for this security module 837 * @option: The process control function requested 838 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 839 * 840 * Allow process control functions (sys_prctl()) to alter capabilities; may 841 * also deny access to other functions not otherwise implemented here. 842 * 843 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 844 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 845 * modules will consider performing the function. 846 */ 847 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 848 unsigned long arg4, unsigned long arg5) 849 { 850 const struct cred *old = current_cred(); 851 struct cred *new; 852 853 switch (option) { 854 case PR_CAPBSET_READ: 855 if (!cap_valid(arg2)) 856 return -EINVAL; 857 return !!cap_raised(old->cap_bset, arg2); 858 859 case PR_CAPBSET_DROP: 860 return cap_prctl_drop(arg2); 861 862 /* 863 * The next four prctl's remain to assist with transitioning a 864 * system from legacy UID=0 based privilege (when filesystem 865 * capabilities are not in use) to a system using filesystem 866 * capabilities only - as the POSIX.1e draft intended. 867 * 868 * Note: 869 * 870 * PR_SET_SECUREBITS = 871 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 872 * | issecure_mask(SECURE_NOROOT) 873 * | issecure_mask(SECURE_NOROOT_LOCKED) 874 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 875 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 876 * 877 * will ensure that the current process and all of its 878 * children will be locked into a pure 879 * capability-based-privilege environment. 880 */ 881 case PR_SET_SECUREBITS: 882 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1) 883 & (old->securebits ^ arg2)) /*[1]*/ 884 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 885 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 886 || (cap_capable(current_cred(), 887 current_cred()->user_ns, CAP_SETPCAP, 888 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 889 /* 890 * [1] no changing of bits that are locked 891 * [2] no unlocking of locks 892 * [3] no setting of unsupported bits 893 * [4] doing anything requires privilege (go read about 894 * the "sendmail capabilities bug") 895 */ 896 ) 897 /* cannot change a locked bit */ 898 return -EPERM; 899 900 new = prepare_creds(); 901 if (!new) 902 return -ENOMEM; 903 new->securebits = arg2; 904 return commit_creds(new); 905 906 case PR_GET_SECUREBITS: 907 return old->securebits; 908 909 case PR_GET_KEEPCAPS: 910 return !!issecure(SECURE_KEEP_CAPS); 911 912 case PR_SET_KEEPCAPS: 913 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 914 return -EINVAL; 915 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 916 return -EPERM; 917 918 new = prepare_creds(); 919 if (!new) 920 return -ENOMEM; 921 if (arg2) 922 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 923 else 924 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 925 return commit_creds(new); 926 927 default: 928 /* No functionality available - continue with default */ 929 return -ENOSYS; 930 } 931 } 932 933 /** 934 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 935 * @mm: The VM space in which the new mapping is to be made 936 * @pages: The size of the mapping 937 * 938 * Determine whether the allocation of a new virtual mapping by the current 939 * task is permitted, returning 1 if permission is granted, 0 if not. 940 */ 941 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 942 { 943 int cap_sys_admin = 0; 944 945 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, 946 SECURITY_CAP_NOAUDIT) == 0) 947 cap_sys_admin = 1; 948 return cap_sys_admin; 949 } 950 951 /* 952 * cap_mmap_addr - check if able to map given addr 953 * @addr: address attempting to be mapped 954 * 955 * If the process is attempting to map memory below dac_mmap_min_addr they need 956 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 957 * capability security module. Returns 0 if this mapping should be allowed 958 * -EPERM if not. 959 */ 960 int cap_mmap_addr(unsigned long addr) 961 { 962 int ret = 0; 963 964 if (addr < dac_mmap_min_addr) { 965 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, 966 SECURITY_CAP_AUDIT); 967 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 968 if (ret == 0) 969 current->flags |= PF_SUPERPRIV; 970 } 971 return ret; 972 } 973 974 int cap_mmap_file(struct file *file, unsigned long reqprot, 975 unsigned long prot, unsigned long flags) 976 { 977 return 0; 978 } 979 980 #ifdef CONFIG_SECURITY 981 982 struct security_hook_list capability_hooks[] = { 983 LSM_HOOK_INIT(capable, cap_capable), 984 LSM_HOOK_INIT(settime, cap_settime), 985 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check), 986 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme), 987 LSM_HOOK_INIT(capget, cap_capget), 988 LSM_HOOK_INIT(capset, cap_capset), 989 LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds), 990 LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec), 991 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv), 992 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv), 993 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr), 994 LSM_HOOK_INIT(mmap_file, cap_mmap_file), 995 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid), 996 LSM_HOOK_INIT(task_prctl, cap_task_prctl), 997 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler), 998 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio), 999 LSM_HOOK_INIT(task_setnice, cap_task_setnice), 1000 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory), 1001 }; 1002 1003 void __init capability_add_hooks(void) 1004 { 1005 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks)); 1006 } 1007 1008 #endif /* CONFIG_SECURITY */ 1009