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 timespec64 *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 const kernel_cap_t *caller_caps; 141 142 rcu_read_lock(); 143 cred = current_cred(); 144 child_cred = __task_cred(child); 145 if (mode & PTRACE_MODE_FSCREDS) 146 caller_caps = &cred->cap_effective; 147 else 148 caller_caps = &cred->cap_permitted; 149 if (cred->user_ns == child_cred->user_ns && 150 cap_issubset(child_cred->cap_permitted, *caller_caps)) 151 goto out; 152 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE)) 153 goto out; 154 ret = -EPERM; 155 out: 156 rcu_read_unlock(); 157 return ret; 158 } 159 160 /** 161 * cap_ptrace_traceme - Determine whether another process may trace the current 162 * @parent: The task proposed to be the tracer 163 * 164 * If parent is in the same or an ancestor user_ns and has all current's 165 * capabilities, then ptrace access is allowed. 166 * If parent has the ptrace capability to current's user_ns, then ptrace 167 * access is allowed. 168 * Else denied. 169 * 170 * Determine whether the nominated task is permitted to trace the current 171 * process, returning 0 if permission is granted, -ve if denied. 172 */ 173 int cap_ptrace_traceme(struct task_struct *parent) 174 { 175 int ret = 0; 176 const struct cred *cred, *child_cred; 177 178 rcu_read_lock(); 179 cred = __task_cred(parent); 180 child_cred = current_cred(); 181 if (cred->user_ns == child_cred->user_ns && 182 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 183 goto out; 184 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE)) 185 goto out; 186 ret = -EPERM; 187 out: 188 rcu_read_unlock(); 189 return ret; 190 } 191 192 /** 193 * cap_capget - Retrieve a task's capability sets 194 * @target: The task from which to retrieve the capability sets 195 * @effective: The place to record the effective set 196 * @inheritable: The place to record the inheritable set 197 * @permitted: The place to record the permitted set 198 * 199 * This function retrieves the capabilities of the nominated task and returns 200 * them to the caller. 201 */ 202 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 203 kernel_cap_t *inheritable, kernel_cap_t *permitted) 204 { 205 const struct cred *cred; 206 207 /* Derived from kernel/capability.c:sys_capget. */ 208 rcu_read_lock(); 209 cred = __task_cred(target); 210 *effective = cred->cap_effective; 211 *inheritable = cred->cap_inheritable; 212 *permitted = cred->cap_permitted; 213 rcu_read_unlock(); 214 return 0; 215 } 216 217 /* 218 * Determine whether the inheritable capabilities are limited to the old 219 * permitted set. Returns 1 if they are limited, 0 if they are not. 220 */ 221 static inline int cap_inh_is_capped(void) 222 { 223 224 /* they are so limited unless the current task has the CAP_SETPCAP 225 * capability 226 */ 227 if (cap_capable(current_cred(), current_cred()->user_ns, 228 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) 229 return 0; 230 return 1; 231 } 232 233 /** 234 * cap_capset - Validate and apply proposed changes to current's capabilities 235 * @new: The proposed new credentials; alterations should be made here 236 * @old: The current task's current credentials 237 * @effective: A pointer to the proposed new effective capabilities set 238 * @inheritable: A pointer to the proposed new inheritable capabilities set 239 * @permitted: A pointer to the proposed new permitted capabilities set 240 * 241 * This function validates and applies a proposed mass change to the current 242 * process's capability sets. The changes are made to the proposed new 243 * credentials, and assuming no error, will be committed by the caller of LSM. 244 */ 245 int cap_capset(struct cred *new, 246 const struct cred *old, 247 const kernel_cap_t *effective, 248 const kernel_cap_t *inheritable, 249 const kernel_cap_t *permitted) 250 { 251 if (cap_inh_is_capped() && 252 !cap_issubset(*inheritable, 253 cap_combine(old->cap_inheritable, 254 old->cap_permitted))) 255 /* incapable of using this inheritable set */ 256 return -EPERM; 257 258 if (!cap_issubset(*inheritable, 259 cap_combine(old->cap_inheritable, 260 old->cap_bset))) 261 /* no new pI capabilities outside bounding set */ 262 return -EPERM; 263 264 /* verify restrictions on target's new Permitted set */ 265 if (!cap_issubset(*permitted, old->cap_permitted)) 266 return -EPERM; 267 268 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 269 if (!cap_issubset(*effective, *permitted)) 270 return -EPERM; 271 272 new->cap_effective = *effective; 273 new->cap_inheritable = *inheritable; 274 new->cap_permitted = *permitted; 275 276 /* 277 * Mask off ambient bits that are no longer both permitted and 278 * inheritable. 279 */ 280 new->cap_ambient = cap_intersect(new->cap_ambient, 281 cap_intersect(*permitted, 282 *inheritable)); 283 if (WARN_ON(!cap_ambient_invariant_ok(new))) 284 return -EINVAL; 285 return 0; 286 } 287 288 /* 289 * Clear proposed capability sets for execve(). 290 */ 291 static inline void bprm_clear_caps(struct linux_binprm *bprm) 292 { 293 cap_clear(bprm->cred->cap_permitted); 294 bprm->cap_effective = false; 295 } 296 297 /** 298 * cap_inode_need_killpriv - Determine if inode change affects privileges 299 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 300 * 301 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 302 * affects the security markings on that inode, and if it is, should 303 * inode_killpriv() be invoked or the change rejected? 304 * 305 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 306 * -ve to deny the change. 307 */ 308 int cap_inode_need_killpriv(struct dentry *dentry) 309 { 310 struct inode *inode = d_backing_inode(dentry); 311 int error; 312 313 if (!inode->i_op->getxattr) 314 return 0; 315 316 error = inode->i_op->getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0); 317 if (error <= 0) 318 return 0; 319 return 1; 320 } 321 322 /** 323 * cap_inode_killpriv - Erase the security markings on an inode 324 * @dentry: The inode/dentry to alter 325 * 326 * Erase the privilege-enhancing security markings on an inode. 327 * 328 * Returns 0 if successful, -ve on error. 329 */ 330 int cap_inode_killpriv(struct dentry *dentry) 331 { 332 struct inode *inode = d_backing_inode(dentry); 333 334 if (!inode->i_op->removexattr) 335 return 0; 336 337 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 338 } 339 340 /* 341 * Calculate the new process capability sets from the capability sets attached 342 * to a file. 343 */ 344 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 345 struct linux_binprm *bprm, 346 bool *effective, 347 bool *has_cap) 348 { 349 struct cred *new = bprm->cred; 350 unsigned i; 351 int ret = 0; 352 353 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 354 *effective = true; 355 356 if (caps->magic_etc & VFS_CAP_REVISION_MASK) 357 *has_cap = true; 358 359 CAP_FOR_EACH_U32(i) { 360 __u32 permitted = caps->permitted.cap[i]; 361 __u32 inheritable = caps->inheritable.cap[i]; 362 363 /* 364 * pP' = (X & fP) | (pI & fI) 365 * The addition of pA' is handled later. 366 */ 367 new->cap_permitted.cap[i] = 368 (new->cap_bset.cap[i] & permitted) | 369 (new->cap_inheritable.cap[i] & inheritable); 370 371 if (permitted & ~new->cap_permitted.cap[i]) 372 /* insufficient to execute correctly */ 373 ret = -EPERM; 374 } 375 376 /* 377 * For legacy apps, with no internal support for recognizing they 378 * do not have enough capabilities, we return an error if they are 379 * missing some "forced" (aka file-permitted) capabilities. 380 */ 381 return *effective ? ret : 0; 382 } 383 384 /* 385 * Extract the on-exec-apply capability sets for an executable file. 386 */ 387 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 388 { 389 struct inode *inode = d_backing_inode(dentry); 390 __u32 magic_etc; 391 unsigned tocopy, i; 392 int size; 393 struct vfs_cap_data caps; 394 395 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 396 397 if (!inode || !inode->i_op->getxattr) 398 return -ENODATA; 399 400 size = inode->i_op->getxattr((struct dentry *)dentry, inode, 401 XATTR_NAME_CAPS, &caps, XATTR_CAPS_SZ); 402 if (size == -ENODATA || size == -EOPNOTSUPP) 403 /* no data, that's ok */ 404 return -ENODATA; 405 if (size < 0) 406 return size; 407 408 if (size < sizeof(magic_etc)) 409 return -EINVAL; 410 411 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 412 413 switch (magic_etc & VFS_CAP_REVISION_MASK) { 414 case VFS_CAP_REVISION_1: 415 if (size != XATTR_CAPS_SZ_1) 416 return -EINVAL; 417 tocopy = VFS_CAP_U32_1; 418 break; 419 case VFS_CAP_REVISION_2: 420 if (size != XATTR_CAPS_SZ_2) 421 return -EINVAL; 422 tocopy = VFS_CAP_U32_2; 423 break; 424 default: 425 return -EINVAL; 426 } 427 428 CAP_FOR_EACH_U32(i) { 429 if (i >= tocopy) 430 break; 431 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 432 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 433 } 434 435 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; 436 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; 437 438 return 0; 439 } 440 441 /* 442 * Attempt to get the on-exec apply capability sets for an executable file from 443 * its xattrs and, if present, apply them to the proposed credentials being 444 * constructed by execve(). 445 */ 446 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) 447 { 448 int rc = 0; 449 struct cpu_vfs_cap_data vcaps; 450 451 bprm_clear_caps(bprm); 452 453 if (!file_caps_enabled) 454 return 0; 455 456 if (!mnt_may_suid(bprm->file->f_path.mnt)) 457 return 0; 458 459 /* 460 * This check is redundant with mnt_may_suid() but is kept to make 461 * explicit that capability bits are limited to s_user_ns and its 462 * descendants. 463 */ 464 if (!current_in_userns(bprm->file->f_path.mnt->mnt_sb->s_user_ns)) 465 return 0; 466 467 rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps); 468 if (rc < 0) { 469 if (rc == -EINVAL) 470 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 471 __func__, rc, bprm->filename); 472 else if (rc == -ENODATA) 473 rc = 0; 474 goto out; 475 } 476 477 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); 478 if (rc == -EINVAL) 479 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 480 __func__, rc, bprm->filename); 481 482 out: 483 if (rc) 484 bprm_clear_caps(bprm); 485 486 return rc; 487 } 488 489 /** 490 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 491 * @bprm: The execution parameters, including the proposed creds 492 * 493 * Set up the proposed credentials for a new execution context being 494 * constructed by execve(). The proposed creds in @bprm->cred is altered, 495 * which won't take effect immediately. Returns 0 if successful, -ve on error. 496 */ 497 int cap_bprm_set_creds(struct linux_binprm *bprm) 498 { 499 const struct cred *old = current_cred(); 500 struct cred *new = bprm->cred; 501 bool effective, has_cap = false, is_setid; 502 int ret; 503 kuid_t root_uid; 504 505 if (WARN_ON(!cap_ambient_invariant_ok(old))) 506 return -EPERM; 507 508 effective = false; 509 ret = get_file_caps(bprm, &effective, &has_cap); 510 if (ret < 0) 511 return ret; 512 513 root_uid = make_kuid(new->user_ns, 0); 514 515 if (!issecure(SECURE_NOROOT)) { 516 /* 517 * If the legacy file capability is set, then don't set privs 518 * for a setuid root binary run by a non-root user. Do set it 519 * for a root user just to cause least surprise to an admin. 520 */ 521 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { 522 warn_setuid_and_fcaps_mixed(bprm->filename); 523 goto skip; 524 } 525 /* 526 * To support inheritance of root-permissions and suid-root 527 * executables under compatibility mode, we override the 528 * capability sets for the file. 529 * 530 * If only the real uid is 0, we do not set the effective bit. 531 */ 532 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { 533 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 534 new->cap_permitted = cap_combine(old->cap_bset, 535 old->cap_inheritable); 536 } 537 if (uid_eq(new->euid, root_uid)) 538 effective = true; 539 } 540 skip: 541 542 /* if we have fs caps, clear dangerous personality flags */ 543 if (!cap_issubset(new->cap_permitted, old->cap_permitted)) 544 bprm->per_clear |= PER_CLEAR_ON_SETID; 545 546 547 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 548 * credentials unless they have the appropriate permit. 549 * 550 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. 551 */ 552 is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid); 553 554 if ((is_setid || 555 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 556 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 557 /* downgrade; they get no more than they had, and maybe less */ 558 if (!capable(CAP_SETUID) || 559 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { 560 new->euid = new->uid; 561 new->egid = new->gid; 562 } 563 new->cap_permitted = cap_intersect(new->cap_permitted, 564 old->cap_permitted); 565 } 566 567 new->suid = new->fsuid = new->euid; 568 new->sgid = new->fsgid = new->egid; 569 570 /* File caps or setid cancels ambient. */ 571 if (has_cap || is_setid) 572 cap_clear(new->cap_ambient); 573 574 /* 575 * Now that we've computed pA', update pP' to give: 576 * pP' = (X & fP) | (pI & fI) | pA' 577 */ 578 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient); 579 580 /* 581 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set, 582 * this is the same as pE' = (fE ? pP' : 0) | pA'. 583 */ 584 if (effective) 585 new->cap_effective = new->cap_permitted; 586 else 587 new->cap_effective = new->cap_ambient; 588 589 if (WARN_ON(!cap_ambient_invariant_ok(new))) 590 return -EPERM; 591 592 bprm->cap_effective = effective; 593 594 /* 595 * Audit candidate if current->cap_effective is set 596 * 597 * We do not bother to audit if 3 things are true: 598 * 1) cap_effective has all caps 599 * 2) we are root 600 * 3) root is supposed to have all caps (SECURE_NOROOT) 601 * Since this is just a normal root execing a process. 602 * 603 * Number 1 above might fail if you don't have a full bset, but I think 604 * that is interesting information to audit. 605 */ 606 if (!cap_issubset(new->cap_effective, new->cap_ambient)) { 607 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 608 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) || 609 issecure(SECURE_NOROOT)) { 610 ret = audit_log_bprm_fcaps(bprm, new, old); 611 if (ret < 0) 612 return ret; 613 } 614 } 615 616 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 617 618 if (WARN_ON(!cap_ambient_invariant_ok(new))) 619 return -EPERM; 620 621 return 0; 622 } 623 624 /** 625 * cap_bprm_secureexec - Determine whether a secure execution is required 626 * @bprm: The execution parameters 627 * 628 * Determine whether a secure execution is required, return 1 if it is, and 0 629 * if it is not. 630 * 631 * The credentials have been committed by this point, and so are no longer 632 * available through @bprm->cred. 633 */ 634 int cap_bprm_secureexec(struct linux_binprm *bprm) 635 { 636 const struct cred *cred = current_cred(); 637 kuid_t root_uid = make_kuid(cred->user_ns, 0); 638 639 if (!uid_eq(cred->uid, root_uid)) { 640 if (bprm->cap_effective) 641 return 1; 642 if (!cap_issubset(cred->cap_permitted, cred->cap_ambient)) 643 return 1; 644 } 645 646 return (!uid_eq(cred->euid, cred->uid) || 647 !gid_eq(cred->egid, cred->gid)); 648 } 649 650 /** 651 * cap_inode_setxattr - Determine whether an xattr may be altered 652 * @dentry: The inode/dentry being altered 653 * @name: The name of the xattr to be changed 654 * @value: The value that the xattr will be changed to 655 * @size: The size of value 656 * @flags: The replacement flag 657 * 658 * Determine whether an xattr may be altered or set on an inode, returning 0 if 659 * permission is granted, -ve if denied. 660 * 661 * This is used to make sure security xattrs don't get updated or set by those 662 * who aren't privileged to do so. 663 */ 664 int cap_inode_setxattr(struct dentry *dentry, const char *name, 665 const void *value, size_t size, int flags) 666 { 667 if (!strcmp(name, XATTR_NAME_CAPS)) { 668 if (!capable(CAP_SETFCAP)) 669 return -EPERM; 670 return 0; 671 } 672 673 if (!strncmp(name, XATTR_SECURITY_PREFIX, 674 sizeof(XATTR_SECURITY_PREFIX) - 1) && 675 !capable(CAP_SYS_ADMIN)) 676 return -EPERM; 677 return 0; 678 } 679 680 /** 681 * cap_inode_removexattr - Determine whether an xattr may be removed 682 * @dentry: The inode/dentry being altered 683 * @name: The name of the xattr to be changed 684 * 685 * Determine whether an xattr may be removed from an inode, returning 0 if 686 * permission is granted, -ve if denied. 687 * 688 * This is used to make sure security xattrs don't get removed by those who 689 * aren't privileged to remove them. 690 */ 691 int cap_inode_removexattr(struct dentry *dentry, const char *name) 692 { 693 if (!strcmp(name, XATTR_NAME_CAPS)) { 694 if (!capable(CAP_SETFCAP)) 695 return -EPERM; 696 return 0; 697 } 698 699 if (!strncmp(name, XATTR_SECURITY_PREFIX, 700 sizeof(XATTR_SECURITY_PREFIX) - 1) && 701 !capable(CAP_SYS_ADMIN)) 702 return -EPERM; 703 return 0; 704 } 705 706 /* 707 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 708 * a process after a call to setuid, setreuid, or setresuid. 709 * 710 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 711 * {r,e,s}uid != 0, the permitted and effective capabilities are 712 * cleared. 713 * 714 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 715 * capabilities of the process are cleared. 716 * 717 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 718 * capabilities are set to the permitted capabilities. 719 * 720 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 721 * never happen. 722 * 723 * -astor 724 * 725 * cevans - New behaviour, Oct '99 726 * A process may, via prctl(), elect to keep its capabilities when it 727 * calls setuid() and switches away from uid==0. Both permitted and 728 * effective sets will be retained. 729 * Without this change, it was impossible for a daemon to drop only some 730 * of its privilege. The call to setuid(!=0) would drop all privileges! 731 * Keeping uid 0 is not an option because uid 0 owns too many vital 732 * files.. 733 * Thanks to Olaf Kirch and Peter Benie for spotting this. 734 */ 735 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 736 { 737 kuid_t root_uid = make_kuid(old->user_ns, 0); 738 739 if ((uid_eq(old->uid, root_uid) || 740 uid_eq(old->euid, root_uid) || 741 uid_eq(old->suid, root_uid)) && 742 (!uid_eq(new->uid, root_uid) && 743 !uid_eq(new->euid, root_uid) && 744 !uid_eq(new->suid, root_uid))) { 745 if (!issecure(SECURE_KEEP_CAPS)) { 746 cap_clear(new->cap_permitted); 747 cap_clear(new->cap_effective); 748 } 749 750 /* 751 * Pre-ambient programs expect setresuid to nonroot followed 752 * by exec to drop capabilities. We should make sure that 753 * this remains the case. 754 */ 755 cap_clear(new->cap_ambient); 756 } 757 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) 758 cap_clear(new->cap_effective); 759 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) 760 new->cap_effective = new->cap_permitted; 761 } 762 763 /** 764 * cap_task_fix_setuid - Fix up the results of setuid() call 765 * @new: The proposed credentials 766 * @old: The current task's current credentials 767 * @flags: Indications of what has changed 768 * 769 * Fix up the results of setuid() call before the credential changes are 770 * actually applied, returning 0 to grant the changes, -ve to deny them. 771 */ 772 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 773 { 774 switch (flags) { 775 case LSM_SETID_RE: 776 case LSM_SETID_ID: 777 case LSM_SETID_RES: 778 /* juggle the capabilities to follow [RES]UID changes unless 779 * otherwise suppressed */ 780 if (!issecure(SECURE_NO_SETUID_FIXUP)) 781 cap_emulate_setxuid(new, old); 782 break; 783 784 case LSM_SETID_FS: 785 /* juggle the capabilties to follow FSUID changes, unless 786 * otherwise suppressed 787 * 788 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 789 * if not, we might be a bit too harsh here. 790 */ 791 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 792 kuid_t root_uid = make_kuid(old->user_ns, 0); 793 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) 794 new->cap_effective = 795 cap_drop_fs_set(new->cap_effective); 796 797 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) 798 new->cap_effective = 799 cap_raise_fs_set(new->cap_effective, 800 new->cap_permitted); 801 } 802 break; 803 804 default: 805 return -EINVAL; 806 } 807 808 return 0; 809 } 810 811 /* 812 * Rationale: code calling task_setscheduler, task_setioprio, and 813 * task_setnice, assumes that 814 * . if capable(cap_sys_nice), then those actions should be allowed 815 * . if not capable(cap_sys_nice), but acting on your own processes, 816 * then those actions should be allowed 817 * This is insufficient now since you can call code without suid, but 818 * yet with increased caps. 819 * So we check for increased caps on the target process. 820 */ 821 static int cap_safe_nice(struct task_struct *p) 822 { 823 int is_subset, ret = 0; 824 825 rcu_read_lock(); 826 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 827 current_cred()->cap_permitted); 828 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) 829 ret = -EPERM; 830 rcu_read_unlock(); 831 832 return ret; 833 } 834 835 /** 836 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 837 * @p: The task to affect 838 * 839 * Detemine if the requested scheduler policy change is permitted for the 840 * specified task, returning 0 if permission is granted, -ve if denied. 841 */ 842 int cap_task_setscheduler(struct task_struct *p) 843 { 844 return cap_safe_nice(p); 845 } 846 847 /** 848 * cap_task_ioprio - Detemine if I/O priority change is permitted 849 * @p: The task to affect 850 * @ioprio: The I/O priority to set 851 * 852 * Detemine if the requested I/O priority change is permitted for the specified 853 * task, returning 0 if permission is granted, -ve if denied. 854 */ 855 int cap_task_setioprio(struct task_struct *p, int ioprio) 856 { 857 return cap_safe_nice(p); 858 } 859 860 /** 861 * cap_task_ioprio - Detemine if task priority change is permitted 862 * @p: The task to affect 863 * @nice: The nice value to set 864 * 865 * Detemine if the requested task priority change is permitted for the 866 * specified task, returning 0 if permission is granted, -ve if denied. 867 */ 868 int cap_task_setnice(struct task_struct *p, int nice) 869 { 870 return cap_safe_nice(p); 871 } 872 873 /* 874 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 875 * the current task's bounding set. Returns 0 on success, -ve on error. 876 */ 877 static int cap_prctl_drop(unsigned long cap) 878 { 879 struct cred *new; 880 881 if (!ns_capable(current_user_ns(), CAP_SETPCAP)) 882 return -EPERM; 883 if (!cap_valid(cap)) 884 return -EINVAL; 885 886 new = prepare_creds(); 887 if (!new) 888 return -ENOMEM; 889 cap_lower(new->cap_bset, cap); 890 return commit_creds(new); 891 } 892 893 /** 894 * cap_task_prctl - Implement process control functions for this security module 895 * @option: The process control function requested 896 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 897 * 898 * Allow process control functions (sys_prctl()) to alter capabilities; may 899 * also deny access to other functions not otherwise implemented here. 900 * 901 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 902 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 903 * modules will consider performing the function. 904 */ 905 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 906 unsigned long arg4, unsigned long arg5) 907 { 908 const struct cred *old = current_cred(); 909 struct cred *new; 910 911 switch (option) { 912 case PR_CAPBSET_READ: 913 if (!cap_valid(arg2)) 914 return -EINVAL; 915 return !!cap_raised(old->cap_bset, arg2); 916 917 case PR_CAPBSET_DROP: 918 return cap_prctl_drop(arg2); 919 920 /* 921 * The next four prctl's remain to assist with transitioning a 922 * system from legacy UID=0 based privilege (when filesystem 923 * capabilities are not in use) to a system using filesystem 924 * capabilities only - as the POSIX.1e draft intended. 925 * 926 * Note: 927 * 928 * PR_SET_SECUREBITS = 929 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 930 * | issecure_mask(SECURE_NOROOT) 931 * | issecure_mask(SECURE_NOROOT_LOCKED) 932 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 933 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 934 * 935 * will ensure that the current process and all of its 936 * children will be locked into a pure 937 * capability-based-privilege environment. 938 */ 939 case PR_SET_SECUREBITS: 940 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1) 941 & (old->securebits ^ arg2)) /*[1]*/ 942 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 943 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 944 || (cap_capable(current_cred(), 945 current_cred()->user_ns, CAP_SETPCAP, 946 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 947 /* 948 * [1] no changing of bits that are locked 949 * [2] no unlocking of locks 950 * [3] no setting of unsupported bits 951 * [4] doing anything requires privilege (go read about 952 * the "sendmail capabilities bug") 953 */ 954 ) 955 /* cannot change a locked bit */ 956 return -EPERM; 957 958 new = prepare_creds(); 959 if (!new) 960 return -ENOMEM; 961 new->securebits = arg2; 962 return commit_creds(new); 963 964 case PR_GET_SECUREBITS: 965 return old->securebits; 966 967 case PR_GET_KEEPCAPS: 968 return !!issecure(SECURE_KEEP_CAPS); 969 970 case PR_SET_KEEPCAPS: 971 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 972 return -EINVAL; 973 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 974 return -EPERM; 975 976 new = prepare_creds(); 977 if (!new) 978 return -ENOMEM; 979 if (arg2) 980 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 981 else 982 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 983 return commit_creds(new); 984 985 case PR_CAP_AMBIENT: 986 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) { 987 if (arg3 | arg4 | arg5) 988 return -EINVAL; 989 990 new = prepare_creds(); 991 if (!new) 992 return -ENOMEM; 993 cap_clear(new->cap_ambient); 994 return commit_creds(new); 995 } 996 997 if (((!cap_valid(arg3)) | arg4 | arg5)) 998 return -EINVAL; 999 1000 if (arg2 == PR_CAP_AMBIENT_IS_SET) { 1001 return !!cap_raised(current_cred()->cap_ambient, arg3); 1002 } else if (arg2 != PR_CAP_AMBIENT_RAISE && 1003 arg2 != PR_CAP_AMBIENT_LOWER) { 1004 return -EINVAL; 1005 } else { 1006 if (arg2 == PR_CAP_AMBIENT_RAISE && 1007 (!cap_raised(current_cred()->cap_permitted, arg3) || 1008 !cap_raised(current_cred()->cap_inheritable, 1009 arg3) || 1010 issecure(SECURE_NO_CAP_AMBIENT_RAISE))) 1011 return -EPERM; 1012 1013 new = prepare_creds(); 1014 if (!new) 1015 return -ENOMEM; 1016 if (arg2 == PR_CAP_AMBIENT_RAISE) 1017 cap_raise(new->cap_ambient, arg3); 1018 else 1019 cap_lower(new->cap_ambient, arg3); 1020 return commit_creds(new); 1021 } 1022 1023 default: 1024 /* No functionality available - continue with default */ 1025 return -ENOSYS; 1026 } 1027 } 1028 1029 /** 1030 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 1031 * @mm: The VM space in which the new mapping is to be made 1032 * @pages: The size of the mapping 1033 * 1034 * Determine whether the allocation of a new virtual mapping by the current 1035 * task is permitted, returning 1 if permission is granted, 0 if not. 1036 */ 1037 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 1038 { 1039 int cap_sys_admin = 0; 1040 1041 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, 1042 SECURITY_CAP_NOAUDIT) == 0) 1043 cap_sys_admin = 1; 1044 return cap_sys_admin; 1045 } 1046 1047 /* 1048 * cap_mmap_addr - check if able to map given addr 1049 * @addr: address attempting to be mapped 1050 * 1051 * If the process is attempting to map memory below dac_mmap_min_addr they need 1052 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 1053 * capability security module. Returns 0 if this mapping should be allowed 1054 * -EPERM if not. 1055 */ 1056 int cap_mmap_addr(unsigned long addr) 1057 { 1058 int ret = 0; 1059 1060 if (addr < dac_mmap_min_addr) { 1061 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, 1062 SECURITY_CAP_AUDIT); 1063 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 1064 if (ret == 0) 1065 current->flags |= PF_SUPERPRIV; 1066 } 1067 return ret; 1068 } 1069 1070 int cap_mmap_file(struct file *file, unsigned long reqprot, 1071 unsigned long prot, unsigned long flags) 1072 { 1073 return 0; 1074 } 1075 1076 #ifdef CONFIG_SECURITY 1077 1078 struct security_hook_list capability_hooks[] = { 1079 LSM_HOOK_INIT(capable, cap_capable), 1080 LSM_HOOK_INIT(settime, cap_settime), 1081 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check), 1082 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme), 1083 LSM_HOOK_INIT(capget, cap_capget), 1084 LSM_HOOK_INIT(capset, cap_capset), 1085 LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds), 1086 LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec), 1087 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv), 1088 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv), 1089 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr), 1090 LSM_HOOK_INIT(mmap_file, cap_mmap_file), 1091 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid), 1092 LSM_HOOK_INIT(task_prctl, cap_task_prctl), 1093 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler), 1094 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio), 1095 LSM_HOOK_INIT(task_setnice, cap_task_setnice), 1096 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory), 1097 }; 1098 1099 void __init capability_add_hooks(void) 1100 { 1101 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks)); 1102 } 1103 1104 #endif /* CONFIG_SECURITY */ 1105