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 if (effective) 533 new->cap_effective = new->cap_permitted; 534 else 535 cap_clear(new->cap_effective); 536 bprm->cap_effective = effective; 537 538 /* 539 * Audit candidate if current->cap_effective is set 540 * 541 * We do not bother to audit if 3 things are true: 542 * 1) cap_effective has all caps 543 * 2) we are root 544 * 3) root is supposed to have all caps (SECURE_NOROOT) 545 * Since this is just a normal root execing a process. 546 * 547 * Number 1 above might fail if you don't have a full bset, but I think 548 * that is interesting information to audit. 549 */ 550 if (!cap_isclear(new->cap_effective)) { 551 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 552 new->euid != 0 || new->uid != 0 || 553 issecure(SECURE_NOROOT)) { 554 ret = audit_log_bprm_fcaps(bprm, new, old); 555 if (ret < 0) 556 return ret; 557 } 558 } 559 560 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 561 return 0; 562 } 563 564 /** 565 * cap_bprm_secureexec - Determine whether a secure execution is required 566 * @bprm: The execution parameters 567 * 568 * Determine whether a secure execution is required, return 1 if it is, and 0 569 * if it is not. 570 * 571 * The credentials have been committed by this point, and so are no longer 572 * available through @bprm->cred. 573 */ 574 int cap_bprm_secureexec(struct linux_binprm *bprm) 575 { 576 const struct cred *cred = current_cred(); 577 578 if (cred->uid != 0) { 579 if (bprm->cap_effective) 580 return 1; 581 if (!cap_isclear(cred->cap_permitted)) 582 return 1; 583 } 584 585 return (cred->euid != cred->uid || 586 cred->egid != cred->gid); 587 } 588 589 /** 590 * cap_inode_setxattr - Determine whether an xattr may be altered 591 * @dentry: The inode/dentry being altered 592 * @name: The name of the xattr to be changed 593 * @value: The value that the xattr will be changed to 594 * @size: The size of value 595 * @flags: The replacement flag 596 * 597 * Determine whether an xattr may be altered or set on an inode, returning 0 if 598 * permission is granted, -ve if denied. 599 * 600 * This is used to make sure security xattrs don't get updated or set by those 601 * who aren't privileged to do so. 602 */ 603 int cap_inode_setxattr(struct dentry *dentry, const char *name, 604 const void *value, size_t size, int flags) 605 { 606 if (!strcmp(name, XATTR_NAME_CAPS)) { 607 if (!capable(CAP_SETFCAP)) 608 return -EPERM; 609 return 0; 610 } 611 612 if (!strncmp(name, XATTR_SECURITY_PREFIX, 613 sizeof(XATTR_SECURITY_PREFIX) - 1) && 614 !capable(CAP_SYS_ADMIN)) 615 return -EPERM; 616 return 0; 617 } 618 619 /** 620 * cap_inode_removexattr - Determine whether an xattr may be removed 621 * @dentry: The inode/dentry being altered 622 * @name: The name of the xattr to be changed 623 * 624 * Determine whether an xattr may be removed from an inode, returning 0 if 625 * permission is granted, -ve if denied. 626 * 627 * This is used to make sure security xattrs don't get removed by those who 628 * aren't privileged to remove them. 629 */ 630 int cap_inode_removexattr(struct dentry *dentry, const char *name) 631 { 632 if (!strcmp(name, XATTR_NAME_CAPS)) { 633 if (!capable(CAP_SETFCAP)) 634 return -EPERM; 635 return 0; 636 } 637 638 if (!strncmp(name, XATTR_SECURITY_PREFIX, 639 sizeof(XATTR_SECURITY_PREFIX) - 1) && 640 !capable(CAP_SYS_ADMIN)) 641 return -EPERM; 642 return 0; 643 } 644 645 /* 646 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 647 * a process after a call to setuid, setreuid, or setresuid. 648 * 649 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 650 * {r,e,s}uid != 0, the permitted and effective capabilities are 651 * cleared. 652 * 653 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 654 * capabilities of the process are cleared. 655 * 656 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 657 * capabilities are set to the permitted capabilities. 658 * 659 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 660 * never happen. 661 * 662 * -astor 663 * 664 * cevans - New behaviour, Oct '99 665 * A process may, via prctl(), elect to keep its capabilities when it 666 * calls setuid() and switches away from uid==0. Both permitted and 667 * effective sets will be retained. 668 * Without this change, it was impossible for a daemon to drop only some 669 * of its privilege. The call to setuid(!=0) would drop all privileges! 670 * Keeping uid 0 is not an option because uid 0 owns too many vital 671 * files.. 672 * Thanks to Olaf Kirch and Peter Benie for spotting this. 673 */ 674 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 675 { 676 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && 677 (new->uid != 0 && new->euid != 0 && new->suid != 0) && 678 !issecure(SECURE_KEEP_CAPS)) { 679 cap_clear(new->cap_permitted); 680 cap_clear(new->cap_effective); 681 } 682 if (old->euid == 0 && new->euid != 0) 683 cap_clear(new->cap_effective); 684 if (old->euid != 0 && new->euid == 0) 685 new->cap_effective = new->cap_permitted; 686 } 687 688 /** 689 * cap_task_fix_setuid - Fix up the results of setuid() call 690 * @new: The proposed credentials 691 * @old: The current task's current credentials 692 * @flags: Indications of what has changed 693 * 694 * Fix up the results of setuid() call before the credential changes are 695 * actually applied, returning 0 to grant the changes, -ve to deny them. 696 */ 697 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 698 { 699 switch (flags) { 700 case LSM_SETID_RE: 701 case LSM_SETID_ID: 702 case LSM_SETID_RES: 703 /* juggle the capabilities to follow [RES]UID changes unless 704 * otherwise suppressed */ 705 if (!issecure(SECURE_NO_SETUID_FIXUP)) 706 cap_emulate_setxuid(new, old); 707 break; 708 709 case LSM_SETID_FS: 710 /* juggle the capabilties to follow FSUID changes, unless 711 * otherwise suppressed 712 * 713 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 714 * if not, we might be a bit too harsh here. 715 */ 716 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 717 if (old->fsuid == 0 && new->fsuid != 0) 718 new->cap_effective = 719 cap_drop_fs_set(new->cap_effective); 720 721 if (old->fsuid != 0 && new->fsuid == 0) 722 new->cap_effective = 723 cap_raise_fs_set(new->cap_effective, 724 new->cap_permitted); 725 } 726 break; 727 728 default: 729 return -EINVAL; 730 } 731 732 return 0; 733 } 734 735 /* 736 * Rationale: code calling task_setscheduler, task_setioprio, and 737 * task_setnice, assumes that 738 * . if capable(cap_sys_nice), then those actions should be allowed 739 * . if not capable(cap_sys_nice), but acting on your own processes, 740 * then those actions should be allowed 741 * This is insufficient now since you can call code without suid, but 742 * yet with increased caps. 743 * So we check for increased caps on the target process. 744 */ 745 static int cap_safe_nice(struct task_struct *p) 746 { 747 int is_subset; 748 749 rcu_read_lock(); 750 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 751 current_cred()->cap_permitted); 752 rcu_read_unlock(); 753 754 if (!is_subset && !capable(CAP_SYS_NICE)) 755 return -EPERM; 756 return 0; 757 } 758 759 /** 760 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 761 * @p: The task to affect 762 * 763 * Detemine if the requested scheduler policy change is permitted for the 764 * specified task, returning 0 if permission is granted, -ve if denied. 765 */ 766 int cap_task_setscheduler(struct task_struct *p) 767 { 768 return cap_safe_nice(p); 769 } 770 771 /** 772 * cap_task_ioprio - Detemine if I/O priority change is permitted 773 * @p: The task to affect 774 * @ioprio: The I/O priority to set 775 * 776 * Detemine if the requested I/O priority change is permitted for the specified 777 * task, returning 0 if permission is granted, -ve if denied. 778 */ 779 int cap_task_setioprio(struct task_struct *p, int ioprio) 780 { 781 return cap_safe_nice(p); 782 } 783 784 /** 785 * cap_task_ioprio - Detemine if task priority change is permitted 786 * @p: The task to affect 787 * @nice: The nice value to set 788 * 789 * Detemine if the requested task priority change is permitted for the 790 * specified task, returning 0 if permission is granted, -ve if denied. 791 */ 792 int cap_task_setnice(struct task_struct *p, int nice) 793 { 794 return cap_safe_nice(p); 795 } 796 797 /* 798 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 799 * the current task's bounding set. Returns 0 on success, -ve on error. 800 */ 801 static long cap_prctl_drop(struct cred *new, unsigned long cap) 802 { 803 if (!capable(CAP_SETPCAP)) 804 return -EPERM; 805 if (!cap_valid(cap)) 806 return -EINVAL; 807 808 cap_lower(new->cap_bset, cap); 809 return 0; 810 } 811 812 /** 813 * cap_task_prctl - Implement process control functions for this security module 814 * @option: The process control function requested 815 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 816 * 817 * Allow process control functions (sys_prctl()) to alter capabilities; may 818 * also deny access to other functions not otherwise implemented here. 819 * 820 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 821 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 822 * modules will consider performing the function. 823 */ 824 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 825 unsigned long arg4, unsigned long arg5) 826 { 827 struct cred *new; 828 long error = 0; 829 830 new = prepare_creds(); 831 if (!new) 832 return -ENOMEM; 833 834 switch (option) { 835 case PR_CAPBSET_READ: 836 error = -EINVAL; 837 if (!cap_valid(arg2)) 838 goto error; 839 error = !!cap_raised(new->cap_bset, arg2); 840 goto no_change; 841 842 case PR_CAPBSET_DROP: 843 error = cap_prctl_drop(new, arg2); 844 if (error < 0) 845 goto error; 846 goto changed; 847 848 /* 849 * The next four prctl's remain to assist with transitioning a 850 * system from legacy UID=0 based privilege (when filesystem 851 * capabilities are not in use) to a system using filesystem 852 * capabilities only - as the POSIX.1e draft intended. 853 * 854 * Note: 855 * 856 * PR_SET_SECUREBITS = 857 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 858 * | issecure_mask(SECURE_NOROOT) 859 * | issecure_mask(SECURE_NOROOT_LOCKED) 860 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 861 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 862 * 863 * will ensure that the current process and all of its 864 * children will be locked into a pure 865 * capability-based-privilege environment. 866 */ 867 case PR_SET_SECUREBITS: 868 error = -EPERM; 869 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 870 & (new->securebits ^ arg2)) /*[1]*/ 871 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 872 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 873 || (cap_capable(current, current_cred(), 874 current_cred()->user->user_ns, CAP_SETPCAP, 875 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 876 /* 877 * [1] no changing of bits that are locked 878 * [2] no unlocking of locks 879 * [3] no setting of unsupported bits 880 * [4] doing anything requires privilege (go read about 881 * the "sendmail capabilities bug") 882 */ 883 ) 884 /* cannot change a locked bit */ 885 goto error; 886 new->securebits = arg2; 887 goto changed; 888 889 case PR_GET_SECUREBITS: 890 error = new->securebits; 891 goto no_change; 892 893 case PR_GET_KEEPCAPS: 894 if (issecure(SECURE_KEEP_CAPS)) 895 error = 1; 896 goto no_change; 897 898 case PR_SET_KEEPCAPS: 899 error = -EINVAL; 900 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 901 goto error; 902 error = -EPERM; 903 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 904 goto error; 905 if (arg2) 906 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 907 else 908 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 909 goto changed; 910 911 default: 912 /* No functionality available - continue with default */ 913 error = -ENOSYS; 914 goto error; 915 } 916 917 /* Functionality provided */ 918 changed: 919 return commit_creds(new); 920 921 no_change: 922 error: 923 abort_creds(new); 924 return error; 925 } 926 927 /** 928 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 929 * @mm: The VM space in which the new mapping is to be made 930 * @pages: The size of the mapping 931 * 932 * Determine whether the allocation of a new virtual mapping by the current 933 * task is permitted, returning 0 if permission is granted, -ve if not. 934 */ 935 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 936 { 937 int cap_sys_admin = 0; 938 939 if (cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_ADMIN, 940 SECURITY_CAP_NOAUDIT) == 0) 941 cap_sys_admin = 1; 942 return __vm_enough_memory(mm, pages, cap_sys_admin); 943 } 944 945 /* 946 * cap_file_mmap - check if able to map given addr 947 * @file: unused 948 * @reqprot: unused 949 * @prot: unused 950 * @flags: unused 951 * @addr: address attempting to be mapped 952 * @addr_only: unused 953 * 954 * If the process is attempting to map memory below dac_mmap_min_addr they need 955 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 956 * capability security module. Returns 0 if this mapping should be allowed 957 * -EPERM if not. 958 */ 959 int cap_file_mmap(struct file *file, unsigned long reqprot, 960 unsigned long prot, unsigned long flags, 961 unsigned long addr, unsigned long addr_only) 962 { 963 int ret = 0; 964 965 if (addr < dac_mmap_min_addr) { 966 ret = cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_RAWIO, 967 SECURITY_CAP_AUDIT); 968 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 969 if (ret == 0) 970 current->flags |= PF_SUPERPRIV; 971 } 972 return ret; 973 } 974