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