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 struct dentry *dentry; 438 int rc = 0; 439 struct cpu_vfs_cap_data vcaps; 440 441 bprm_clear_caps(bprm); 442 443 if (!file_caps_enabled) 444 return 0; 445 446 if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) 447 return 0; 448 449 dentry = dget(bprm->file->f_path.dentry); 450 451 rc = get_vfs_caps_from_disk(dentry, &vcaps); 452 if (rc < 0) { 453 if (rc == -EINVAL) 454 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 455 __func__, rc, bprm->filename); 456 else if (rc == -ENODATA) 457 rc = 0; 458 goto out; 459 } 460 461 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); 462 if (rc == -EINVAL) 463 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 464 __func__, rc, bprm->filename); 465 466 out: 467 dput(dentry); 468 if (rc) 469 bprm_clear_caps(bprm); 470 471 return rc; 472 } 473 474 /** 475 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 476 * @bprm: The execution parameters, including the proposed creds 477 * 478 * Set up the proposed credentials for a new execution context being 479 * constructed by execve(). The proposed creds in @bprm->cred is altered, 480 * which won't take effect immediately. Returns 0 if successful, -ve on error. 481 */ 482 int cap_bprm_set_creds(struct linux_binprm *bprm) 483 { 484 const struct cred *old = current_cred(); 485 struct cred *new = bprm->cred; 486 bool effective, has_cap = false; 487 int ret; 488 kuid_t root_uid; 489 490 effective = false; 491 ret = get_file_caps(bprm, &effective, &has_cap); 492 if (ret < 0) 493 return ret; 494 495 root_uid = make_kuid(new->user_ns, 0); 496 497 if (!issecure(SECURE_NOROOT)) { 498 /* 499 * If the legacy file capability is set, then don't set privs 500 * for a setuid root binary run by a non-root user. Do set it 501 * for a root user just to cause least surprise to an admin. 502 */ 503 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { 504 warn_setuid_and_fcaps_mixed(bprm->filename); 505 goto skip; 506 } 507 /* 508 * To support inheritance of root-permissions and suid-root 509 * executables under compatibility mode, we override the 510 * capability sets for the file. 511 * 512 * If only the real uid is 0, we do not set the effective bit. 513 */ 514 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { 515 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 516 new->cap_permitted = cap_combine(old->cap_bset, 517 old->cap_inheritable); 518 } 519 if (uid_eq(new->euid, root_uid)) 520 effective = true; 521 } 522 skip: 523 524 /* if we have fs caps, clear dangerous personality flags */ 525 if (!cap_issubset(new->cap_permitted, old->cap_permitted)) 526 bprm->per_clear |= PER_CLEAR_ON_SETID; 527 528 529 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 530 * credentials unless they have the appropriate permit. 531 * 532 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. 533 */ 534 if ((!uid_eq(new->euid, old->uid) || 535 !gid_eq(new->egid, old->gid) || 536 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 537 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 538 /* downgrade; they get no more than they had, and maybe less */ 539 if (!capable(CAP_SETUID) || 540 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { 541 new->euid = new->uid; 542 new->egid = new->gid; 543 } 544 new->cap_permitted = cap_intersect(new->cap_permitted, 545 old->cap_permitted); 546 } 547 548 new->suid = new->fsuid = new->euid; 549 new->sgid = new->fsgid = new->egid; 550 551 if (effective) 552 new->cap_effective = new->cap_permitted; 553 else 554 cap_clear(new->cap_effective); 555 bprm->cap_effective = effective; 556 557 /* 558 * Audit candidate if current->cap_effective is set 559 * 560 * We do not bother to audit if 3 things are true: 561 * 1) cap_effective has all caps 562 * 2) we are root 563 * 3) root is supposed to have all caps (SECURE_NOROOT) 564 * Since this is just a normal root execing a process. 565 * 566 * Number 1 above might fail if you don't have a full bset, but I think 567 * that is interesting information to audit. 568 */ 569 if (!cap_isclear(new->cap_effective)) { 570 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 571 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) || 572 issecure(SECURE_NOROOT)) { 573 ret = audit_log_bprm_fcaps(bprm, new, old); 574 if (ret < 0) 575 return ret; 576 } 577 } 578 579 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 580 return 0; 581 } 582 583 /** 584 * cap_bprm_secureexec - Determine whether a secure execution is required 585 * @bprm: The execution parameters 586 * 587 * Determine whether a secure execution is required, return 1 if it is, and 0 588 * if it is not. 589 * 590 * The credentials have been committed by this point, and so are no longer 591 * available through @bprm->cred. 592 */ 593 int cap_bprm_secureexec(struct linux_binprm *bprm) 594 { 595 const struct cred *cred = current_cred(); 596 kuid_t root_uid = make_kuid(cred->user_ns, 0); 597 598 if (!uid_eq(cred->uid, root_uid)) { 599 if (bprm->cap_effective) 600 return 1; 601 if (!cap_isclear(cred->cap_permitted)) 602 return 1; 603 } 604 605 return (!uid_eq(cred->euid, cred->uid) || 606 !gid_eq(cred->egid, cred->gid)); 607 } 608 609 /** 610 * cap_inode_setxattr - Determine whether an xattr may be altered 611 * @dentry: The inode/dentry being altered 612 * @name: The name of the xattr to be changed 613 * @value: The value that the xattr will be changed to 614 * @size: The size of value 615 * @flags: The replacement flag 616 * 617 * Determine whether an xattr may be altered or set on an inode, returning 0 if 618 * permission is granted, -ve if denied. 619 * 620 * This is used to make sure security xattrs don't get updated or set by those 621 * who aren't privileged to do so. 622 */ 623 int cap_inode_setxattr(struct dentry *dentry, const char *name, 624 const void *value, size_t size, int flags) 625 { 626 if (!strcmp(name, XATTR_NAME_CAPS)) { 627 if (!capable(CAP_SETFCAP)) 628 return -EPERM; 629 return 0; 630 } 631 632 if (!strncmp(name, XATTR_SECURITY_PREFIX, 633 sizeof(XATTR_SECURITY_PREFIX) - 1) && 634 !capable(CAP_SYS_ADMIN)) 635 return -EPERM; 636 return 0; 637 } 638 639 /** 640 * cap_inode_removexattr - Determine whether an xattr may be removed 641 * @dentry: The inode/dentry being altered 642 * @name: The name of the xattr to be changed 643 * 644 * Determine whether an xattr may be removed from an inode, returning 0 if 645 * permission is granted, -ve if denied. 646 * 647 * This is used to make sure security xattrs don't get removed by those who 648 * aren't privileged to remove them. 649 */ 650 int cap_inode_removexattr(struct dentry *dentry, const char *name) 651 { 652 if (!strcmp(name, XATTR_NAME_CAPS)) { 653 if (!capable(CAP_SETFCAP)) 654 return -EPERM; 655 return 0; 656 } 657 658 if (!strncmp(name, XATTR_SECURITY_PREFIX, 659 sizeof(XATTR_SECURITY_PREFIX) - 1) && 660 !capable(CAP_SYS_ADMIN)) 661 return -EPERM; 662 return 0; 663 } 664 665 /* 666 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 667 * a process after a call to setuid, setreuid, or setresuid. 668 * 669 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 670 * {r,e,s}uid != 0, the permitted and effective capabilities are 671 * cleared. 672 * 673 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 674 * capabilities of the process are cleared. 675 * 676 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 677 * capabilities are set to the permitted capabilities. 678 * 679 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 680 * never happen. 681 * 682 * -astor 683 * 684 * cevans - New behaviour, Oct '99 685 * A process may, via prctl(), elect to keep its capabilities when it 686 * calls setuid() and switches away from uid==0. Both permitted and 687 * effective sets will be retained. 688 * Without this change, it was impossible for a daemon to drop only some 689 * of its privilege. The call to setuid(!=0) would drop all privileges! 690 * Keeping uid 0 is not an option because uid 0 owns too many vital 691 * files.. 692 * Thanks to Olaf Kirch and Peter Benie for spotting this. 693 */ 694 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 695 { 696 kuid_t root_uid = make_kuid(old->user_ns, 0); 697 698 if ((uid_eq(old->uid, root_uid) || 699 uid_eq(old->euid, root_uid) || 700 uid_eq(old->suid, root_uid)) && 701 (!uid_eq(new->uid, root_uid) && 702 !uid_eq(new->euid, root_uid) && 703 !uid_eq(new->suid, root_uid)) && 704 !issecure(SECURE_KEEP_CAPS)) { 705 cap_clear(new->cap_permitted); 706 cap_clear(new->cap_effective); 707 } 708 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) 709 cap_clear(new->cap_effective); 710 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) 711 new->cap_effective = new->cap_permitted; 712 } 713 714 /** 715 * cap_task_fix_setuid - Fix up the results of setuid() call 716 * @new: The proposed credentials 717 * @old: The current task's current credentials 718 * @flags: Indications of what has changed 719 * 720 * Fix up the results of setuid() call before the credential changes are 721 * actually applied, returning 0 to grant the changes, -ve to deny them. 722 */ 723 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 724 { 725 switch (flags) { 726 case LSM_SETID_RE: 727 case LSM_SETID_ID: 728 case LSM_SETID_RES: 729 /* juggle the capabilities to follow [RES]UID changes unless 730 * otherwise suppressed */ 731 if (!issecure(SECURE_NO_SETUID_FIXUP)) 732 cap_emulate_setxuid(new, old); 733 break; 734 735 case LSM_SETID_FS: 736 /* juggle the capabilties to follow FSUID changes, unless 737 * otherwise suppressed 738 * 739 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 740 * if not, we might be a bit too harsh here. 741 */ 742 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 743 kuid_t root_uid = make_kuid(old->user_ns, 0); 744 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) 745 new->cap_effective = 746 cap_drop_fs_set(new->cap_effective); 747 748 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) 749 new->cap_effective = 750 cap_raise_fs_set(new->cap_effective, 751 new->cap_permitted); 752 } 753 break; 754 755 default: 756 return -EINVAL; 757 } 758 759 return 0; 760 } 761 762 /* 763 * Rationale: code calling task_setscheduler, task_setioprio, and 764 * task_setnice, assumes that 765 * . if capable(cap_sys_nice), then those actions should be allowed 766 * . if not capable(cap_sys_nice), but acting on your own processes, 767 * then those actions should be allowed 768 * This is insufficient now since you can call code without suid, but 769 * yet with increased caps. 770 * So we check for increased caps on the target process. 771 */ 772 static int cap_safe_nice(struct task_struct *p) 773 { 774 int is_subset, ret = 0; 775 776 rcu_read_lock(); 777 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 778 current_cred()->cap_permitted); 779 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) 780 ret = -EPERM; 781 rcu_read_unlock(); 782 783 return ret; 784 } 785 786 /** 787 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 788 * @p: The task to affect 789 * 790 * Detemine if the requested scheduler policy change is permitted for the 791 * specified task, returning 0 if permission is granted, -ve if denied. 792 */ 793 int cap_task_setscheduler(struct task_struct *p) 794 { 795 return cap_safe_nice(p); 796 } 797 798 /** 799 * cap_task_ioprio - Detemine if I/O priority change is permitted 800 * @p: The task to affect 801 * @ioprio: The I/O priority to set 802 * 803 * Detemine if the requested I/O priority change is permitted for the specified 804 * task, returning 0 if permission is granted, -ve if denied. 805 */ 806 int cap_task_setioprio(struct task_struct *p, int ioprio) 807 { 808 return cap_safe_nice(p); 809 } 810 811 /** 812 * cap_task_ioprio - Detemine if task priority change is permitted 813 * @p: The task to affect 814 * @nice: The nice value to set 815 * 816 * Detemine if the requested task priority change is permitted for the 817 * specified task, returning 0 if permission is granted, -ve if denied. 818 */ 819 int cap_task_setnice(struct task_struct *p, int nice) 820 { 821 return cap_safe_nice(p); 822 } 823 824 /* 825 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 826 * the current task's bounding set. Returns 0 on success, -ve on error. 827 */ 828 static int cap_prctl_drop(unsigned long cap) 829 { 830 struct cred *new; 831 832 if (!ns_capable(current_user_ns(), CAP_SETPCAP)) 833 return -EPERM; 834 if (!cap_valid(cap)) 835 return -EINVAL; 836 837 new = prepare_creds(); 838 if (!new) 839 return -ENOMEM; 840 cap_lower(new->cap_bset, cap); 841 return commit_creds(new); 842 } 843 844 /** 845 * cap_task_prctl - Implement process control functions for this security module 846 * @option: The process control function requested 847 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 848 * 849 * Allow process control functions (sys_prctl()) to alter capabilities; may 850 * also deny access to other functions not otherwise implemented here. 851 * 852 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 853 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 854 * modules will consider performing the function. 855 */ 856 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 857 unsigned long arg4, unsigned long arg5) 858 { 859 const struct cred *old = current_cred(); 860 struct cred *new; 861 862 switch (option) { 863 case PR_CAPBSET_READ: 864 if (!cap_valid(arg2)) 865 return -EINVAL; 866 return !!cap_raised(old->cap_bset, arg2); 867 868 case PR_CAPBSET_DROP: 869 return cap_prctl_drop(arg2); 870 871 /* 872 * The next four prctl's remain to assist with transitioning a 873 * system from legacy UID=0 based privilege (when filesystem 874 * capabilities are not in use) to a system using filesystem 875 * capabilities only - as the POSIX.1e draft intended. 876 * 877 * Note: 878 * 879 * PR_SET_SECUREBITS = 880 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 881 * | issecure_mask(SECURE_NOROOT) 882 * | issecure_mask(SECURE_NOROOT_LOCKED) 883 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 884 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 885 * 886 * will ensure that the current process and all of its 887 * children will be locked into a pure 888 * capability-based-privilege environment. 889 */ 890 case PR_SET_SECUREBITS: 891 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1) 892 & (old->securebits ^ arg2)) /*[1]*/ 893 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 894 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 895 || (cap_capable(current_cred(), 896 current_cred()->user_ns, CAP_SETPCAP, 897 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 898 /* 899 * [1] no changing of bits that are locked 900 * [2] no unlocking of locks 901 * [3] no setting of unsupported bits 902 * [4] doing anything requires privilege (go read about 903 * the "sendmail capabilities bug") 904 */ 905 ) 906 /* cannot change a locked bit */ 907 return -EPERM; 908 909 new = prepare_creds(); 910 if (!new) 911 return -ENOMEM; 912 new->securebits = arg2; 913 return commit_creds(new); 914 915 case PR_GET_SECUREBITS: 916 return old->securebits; 917 918 case PR_GET_KEEPCAPS: 919 return !!issecure(SECURE_KEEP_CAPS); 920 921 case PR_SET_KEEPCAPS: 922 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 923 return -EINVAL; 924 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 925 return -EPERM; 926 927 new = prepare_creds(); 928 if (!new) 929 return -ENOMEM; 930 if (arg2) 931 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 932 else 933 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 934 return commit_creds(new); 935 936 default: 937 /* No functionality available - continue with default */ 938 return -ENOSYS; 939 } 940 } 941 942 /** 943 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 944 * @mm: The VM space in which the new mapping is to be made 945 * @pages: The size of the mapping 946 * 947 * Determine whether the allocation of a new virtual mapping by the current 948 * task is permitted, returning 0 if permission is granted, -ve if not. 949 */ 950 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 951 { 952 int cap_sys_admin = 0; 953 954 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, 955 SECURITY_CAP_NOAUDIT) == 0) 956 cap_sys_admin = 1; 957 return __vm_enough_memory(mm, pages, cap_sys_admin); 958 } 959 960 /* 961 * cap_mmap_addr - check if able to map given addr 962 * @addr: address attempting to be mapped 963 * 964 * If the process is attempting to map memory below dac_mmap_min_addr they need 965 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 966 * capability security module. Returns 0 if this mapping should be allowed 967 * -EPERM if not. 968 */ 969 int cap_mmap_addr(unsigned long addr) 970 { 971 int ret = 0; 972 973 if (addr < dac_mmap_min_addr) { 974 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, 975 SECURITY_CAP_AUDIT); 976 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 977 if (ret == 0) 978 current->flags |= PF_SUPERPRIV; 979 } 980 return ret; 981 } 982 983 int cap_mmap_file(struct file *file, unsigned long reqprot, 984 unsigned long prot, unsigned long flags) 985 { 986 return 0; 987 } 988