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