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 return 0; 425 } 426 427 /* 428 * Attempt to get the on-exec apply capability sets for an executable file from 429 * its xattrs and, if present, apply them to the proposed credentials being 430 * constructed by execve(). 431 */ 432 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) 433 { 434 struct dentry *dentry; 435 int rc = 0; 436 struct cpu_vfs_cap_data vcaps; 437 438 bprm_clear_caps(bprm); 439 440 if (!file_caps_enabled) 441 return 0; 442 443 if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) 444 return 0; 445 446 dentry = dget(bprm->file->f_dentry); 447 448 rc = get_vfs_caps_from_disk(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 dput(dentry); 465 if (rc) 466 bprm_clear_caps(bprm); 467 468 return rc; 469 } 470 471 /** 472 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 473 * @bprm: The execution parameters, including the proposed creds 474 * 475 * Set up the proposed credentials for a new execution context being 476 * constructed by execve(). The proposed creds in @bprm->cred is altered, 477 * which won't take effect immediately. Returns 0 if successful, -ve on error. 478 */ 479 int cap_bprm_set_creds(struct linux_binprm *bprm) 480 { 481 const struct cred *old = current_cred(); 482 struct cred *new = bprm->cred; 483 bool effective, has_cap = false; 484 int ret; 485 kuid_t root_uid; 486 487 effective = false; 488 ret = get_file_caps(bprm, &effective, &has_cap); 489 if (ret < 0) 490 return ret; 491 492 root_uid = make_kuid(new->user_ns, 0); 493 494 if (!issecure(SECURE_NOROOT)) { 495 /* 496 * If the legacy file capability is set, then don't set privs 497 * for a setuid root binary run by a non-root user. Do set it 498 * for a root user just to cause least surprise to an admin. 499 */ 500 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { 501 warn_setuid_and_fcaps_mixed(bprm->filename); 502 goto skip; 503 } 504 /* 505 * To support inheritance of root-permissions and suid-root 506 * executables under compatibility mode, we override the 507 * capability sets for the file. 508 * 509 * If only the real uid is 0, we do not set the effective bit. 510 */ 511 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { 512 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 513 new->cap_permitted = cap_combine(old->cap_bset, 514 old->cap_inheritable); 515 } 516 if (uid_eq(new->euid, root_uid)) 517 effective = true; 518 } 519 skip: 520 521 /* if we have fs caps, clear dangerous personality flags */ 522 if (!cap_issubset(new->cap_permitted, old->cap_permitted)) 523 bprm->per_clear |= PER_CLEAR_ON_SETID; 524 525 526 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 527 * credentials unless they have the appropriate permit. 528 * 529 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. 530 */ 531 if ((!uid_eq(new->euid, old->uid) || 532 !gid_eq(new->egid, old->gid) || 533 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 534 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 535 /* downgrade; they get no more than they had, and maybe less */ 536 if (!capable(CAP_SETUID) || 537 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { 538 new->euid = new->uid; 539 new->egid = new->gid; 540 } 541 new->cap_permitted = cap_intersect(new->cap_permitted, 542 old->cap_permitted); 543 } 544 545 new->suid = new->fsuid = new->euid; 546 new->sgid = new->fsgid = new->egid; 547 548 if (effective) 549 new->cap_effective = new->cap_permitted; 550 else 551 cap_clear(new->cap_effective); 552 bprm->cap_effective = effective; 553 554 /* 555 * Audit candidate if current->cap_effective is set 556 * 557 * We do not bother to audit if 3 things are true: 558 * 1) cap_effective has all caps 559 * 2) we are root 560 * 3) root is supposed to have all caps (SECURE_NOROOT) 561 * Since this is just a normal root execing a process. 562 * 563 * Number 1 above might fail if you don't have a full bset, but I think 564 * that is interesting information to audit. 565 */ 566 if (!cap_isclear(new->cap_effective)) { 567 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 568 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) || 569 issecure(SECURE_NOROOT)) { 570 ret = audit_log_bprm_fcaps(bprm, new, old); 571 if (ret < 0) 572 return ret; 573 } 574 } 575 576 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 577 return 0; 578 } 579 580 /** 581 * cap_bprm_secureexec - Determine whether a secure execution is required 582 * @bprm: The execution parameters 583 * 584 * Determine whether a secure execution is required, return 1 if it is, and 0 585 * if it is not. 586 * 587 * The credentials have been committed by this point, and so are no longer 588 * available through @bprm->cred. 589 */ 590 int cap_bprm_secureexec(struct linux_binprm *bprm) 591 { 592 const struct cred *cred = current_cred(); 593 kuid_t root_uid = make_kuid(cred->user_ns, 0); 594 595 if (!uid_eq(cred->uid, root_uid)) { 596 if (bprm->cap_effective) 597 return 1; 598 if (!cap_isclear(cred->cap_permitted)) 599 return 1; 600 } 601 602 return (!uid_eq(cred->euid, cred->uid) || 603 !gid_eq(cred->egid, cred->gid)); 604 } 605 606 /** 607 * cap_inode_setxattr - Determine whether an xattr may be altered 608 * @dentry: The inode/dentry being altered 609 * @name: The name of the xattr to be changed 610 * @value: The value that the xattr will be changed to 611 * @size: The size of value 612 * @flags: The replacement flag 613 * 614 * Determine whether an xattr may be altered or set on an inode, returning 0 if 615 * permission is granted, -ve if denied. 616 * 617 * This is used to make sure security xattrs don't get updated or set by those 618 * who aren't privileged to do so. 619 */ 620 int cap_inode_setxattr(struct dentry *dentry, const char *name, 621 const void *value, size_t size, int flags) 622 { 623 if (!strcmp(name, XATTR_NAME_CAPS)) { 624 if (!capable(CAP_SETFCAP)) 625 return -EPERM; 626 return 0; 627 } 628 629 if (!strncmp(name, XATTR_SECURITY_PREFIX, 630 sizeof(XATTR_SECURITY_PREFIX) - 1) && 631 !capable(CAP_SYS_ADMIN)) 632 return -EPERM; 633 return 0; 634 } 635 636 /** 637 * cap_inode_removexattr - Determine whether an xattr may be removed 638 * @dentry: The inode/dentry being altered 639 * @name: The name of the xattr to be changed 640 * 641 * Determine whether an xattr may be removed from an inode, returning 0 if 642 * permission is granted, -ve if denied. 643 * 644 * This is used to make sure security xattrs don't get removed by those who 645 * aren't privileged to remove them. 646 */ 647 int cap_inode_removexattr(struct dentry *dentry, const char *name) 648 { 649 if (!strcmp(name, XATTR_NAME_CAPS)) { 650 if (!capable(CAP_SETFCAP)) 651 return -EPERM; 652 return 0; 653 } 654 655 if (!strncmp(name, XATTR_SECURITY_PREFIX, 656 sizeof(XATTR_SECURITY_PREFIX) - 1) && 657 !capable(CAP_SYS_ADMIN)) 658 return -EPERM; 659 return 0; 660 } 661 662 /* 663 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 664 * a process after a call to setuid, setreuid, or setresuid. 665 * 666 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 667 * {r,e,s}uid != 0, the permitted and effective capabilities are 668 * cleared. 669 * 670 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 671 * capabilities of the process are cleared. 672 * 673 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 674 * capabilities are set to the permitted capabilities. 675 * 676 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 677 * never happen. 678 * 679 * -astor 680 * 681 * cevans - New behaviour, Oct '99 682 * A process may, via prctl(), elect to keep its capabilities when it 683 * calls setuid() and switches away from uid==0. Both permitted and 684 * effective sets will be retained. 685 * Without this change, it was impossible for a daemon to drop only some 686 * of its privilege. The call to setuid(!=0) would drop all privileges! 687 * Keeping uid 0 is not an option because uid 0 owns too many vital 688 * files.. 689 * Thanks to Olaf Kirch and Peter Benie for spotting this. 690 */ 691 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 692 { 693 kuid_t root_uid = make_kuid(old->user_ns, 0); 694 695 if ((uid_eq(old->uid, root_uid) || 696 uid_eq(old->euid, root_uid) || 697 uid_eq(old->suid, root_uid)) && 698 (!uid_eq(new->uid, root_uid) && 699 !uid_eq(new->euid, root_uid) && 700 !uid_eq(new->suid, root_uid)) && 701 !issecure(SECURE_KEEP_CAPS)) { 702 cap_clear(new->cap_permitted); 703 cap_clear(new->cap_effective); 704 } 705 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) 706 cap_clear(new->cap_effective); 707 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) 708 new->cap_effective = new->cap_permitted; 709 } 710 711 /** 712 * cap_task_fix_setuid - Fix up the results of setuid() call 713 * @new: The proposed credentials 714 * @old: The current task's current credentials 715 * @flags: Indications of what has changed 716 * 717 * Fix up the results of setuid() call before the credential changes are 718 * actually applied, returning 0 to grant the changes, -ve to deny them. 719 */ 720 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 721 { 722 switch (flags) { 723 case LSM_SETID_RE: 724 case LSM_SETID_ID: 725 case LSM_SETID_RES: 726 /* juggle the capabilities to follow [RES]UID changes unless 727 * otherwise suppressed */ 728 if (!issecure(SECURE_NO_SETUID_FIXUP)) 729 cap_emulate_setxuid(new, old); 730 break; 731 732 case LSM_SETID_FS: 733 /* juggle the capabilties to follow FSUID changes, unless 734 * otherwise suppressed 735 * 736 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 737 * if not, we might be a bit too harsh here. 738 */ 739 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 740 kuid_t root_uid = make_kuid(old->user_ns, 0); 741 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) 742 new->cap_effective = 743 cap_drop_fs_set(new->cap_effective); 744 745 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) 746 new->cap_effective = 747 cap_raise_fs_set(new->cap_effective, 748 new->cap_permitted); 749 } 750 break; 751 752 default: 753 return -EINVAL; 754 } 755 756 return 0; 757 } 758 759 /* 760 * Rationale: code calling task_setscheduler, task_setioprio, and 761 * task_setnice, assumes that 762 * . if capable(cap_sys_nice), then those actions should be allowed 763 * . if not capable(cap_sys_nice), but acting on your own processes, 764 * then those actions should be allowed 765 * This is insufficient now since you can call code without suid, but 766 * yet with increased caps. 767 * So we check for increased caps on the target process. 768 */ 769 static int cap_safe_nice(struct task_struct *p) 770 { 771 int is_subset; 772 773 rcu_read_lock(); 774 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 775 current_cred()->cap_permitted); 776 rcu_read_unlock(); 777 778 if (!is_subset && !capable(CAP_SYS_NICE)) 779 return -EPERM; 780 return 0; 781 } 782 783 /** 784 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 785 * @p: The task to affect 786 * 787 * Detemine if the requested scheduler policy change is permitted for the 788 * specified task, returning 0 if permission is granted, -ve if denied. 789 */ 790 int cap_task_setscheduler(struct task_struct *p) 791 { 792 return cap_safe_nice(p); 793 } 794 795 /** 796 * cap_task_ioprio - Detemine if I/O priority change is permitted 797 * @p: The task to affect 798 * @ioprio: The I/O priority to set 799 * 800 * Detemine if the requested I/O priority change is permitted for the specified 801 * task, returning 0 if permission is granted, -ve if denied. 802 */ 803 int cap_task_setioprio(struct task_struct *p, int ioprio) 804 { 805 return cap_safe_nice(p); 806 } 807 808 /** 809 * cap_task_ioprio - Detemine if task priority change is permitted 810 * @p: The task to affect 811 * @nice: The nice value to set 812 * 813 * Detemine if the requested task priority change is permitted for the 814 * specified task, returning 0 if permission is granted, -ve if denied. 815 */ 816 int cap_task_setnice(struct task_struct *p, int nice) 817 { 818 return cap_safe_nice(p); 819 } 820 821 /* 822 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 823 * the current task's bounding set. Returns 0 on success, -ve on error. 824 */ 825 static long cap_prctl_drop(struct cred *new, unsigned long cap) 826 { 827 if (!capable(CAP_SETPCAP)) 828 return -EPERM; 829 if (!cap_valid(cap)) 830 return -EINVAL; 831 832 cap_lower(new->cap_bset, cap); 833 return 0; 834 } 835 836 /** 837 * cap_task_prctl - Implement process control functions for this security module 838 * @option: The process control function requested 839 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 840 * 841 * Allow process control functions (sys_prctl()) to alter capabilities; may 842 * also deny access to other functions not otherwise implemented here. 843 * 844 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 845 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 846 * modules will consider performing the function. 847 */ 848 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 849 unsigned long arg4, unsigned long arg5) 850 { 851 struct cred *new; 852 long error = 0; 853 854 new = prepare_creds(); 855 if (!new) 856 return -ENOMEM; 857 858 switch (option) { 859 case PR_CAPBSET_READ: 860 error = -EINVAL; 861 if (!cap_valid(arg2)) 862 goto error; 863 error = !!cap_raised(new->cap_bset, arg2); 864 goto no_change; 865 866 case PR_CAPBSET_DROP: 867 error = cap_prctl_drop(new, arg2); 868 if (error < 0) 869 goto error; 870 goto changed; 871 872 /* 873 * The next four prctl's remain to assist with transitioning a 874 * system from legacy UID=0 based privilege (when filesystem 875 * capabilities are not in use) to a system using filesystem 876 * capabilities only - as the POSIX.1e draft intended. 877 * 878 * Note: 879 * 880 * PR_SET_SECUREBITS = 881 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 882 * | issecure_mask(SECURE_NOROOT) 883 * | issecure_mask(SECURE_NOROOT_LOCKED) 884 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 885 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 886 * 887 * will ensure that the current process and all of its 888 * children will be locked into a pure 889 * capability-based-privilege environment. 890 */ 891 case PR_SET_SECUREBITS: 892 error = -EPERM; 893 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 894 & (new->securebits ^ arg2)) /*[1]*/ 895 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 896 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 897 || (cap_capable(current_cred(), 898 current_cred()->user_ns, CAP_SETPCAP, 899 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 900 /* 901 * [1] no changing of bits that are locked 902 * [2] no unlocking of locks 903 * [3] no setting of unsupported bits 904 * [4] doing anything requires privilege (go read about 905 * the "sendmail capabilities bug") 906 */ 907 ) 908 /* cannot change a locked bit */ 909 goto error; 910 new->securebits = arg2; 911 goto changed; 912 913 case PR_GET_SECUREBITS: 914 error = new->securebits; 915 goto no_change; 916 917 case PR_GET_KEEPCAPS: 918 if (issecure(SECURE_KEEP_CAPS)) 919 error = 1; 920 goto no_change; 921 922 case PR_SET_KEEPCAPS: 923 error = -EINVAL; 924 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 925 goto error; 926 error = -EPERM; 927 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 928 goto error; 929 if (arg2) 930 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 931 else 932 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 933 goto changed; 934 935 default: 936 /* No functionality available - continue with default */ 937 error = -ENOSYS; 938 goto error; 939 } 940 941 /* Functionality provided */ 942 changed: 943 return commit_creds(new); 944 945 no_change: 946 error: 947 abort_creds(new); 948 return error; 949 } 950 951 /** 952 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 953 * @mm: The VM space in which the new mapping is to be made 954 * @pages: The size of the mapping 955 * 956 * Determine whether the allocation of a new virtual mapping by the current 957 * task is permitted, returning 0 if permission is granted, -ve if not. 958 */ 959 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 960 { 961 int cap_sys_admin = 0; 962 963 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, 964 SECURITY_CAP_NOAUDIT) == 0) 965 cap_sys_admin = 1; 966 return __vm_enough_memory(mm, pages, cap_sys_admin); 967 } 968 969 /* 970 * cap_mmap_addr - check if able to map given addr 971 * @addr: address attempting to be mapped 972 * 973 * If the process is attempting to map memory below dac_mmap_min_addr they need 974 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 975 * capability security module. Returns 0 if this mapping should be allowed 976 * -EPERM if not. 977 */ 978 int cap_mmap_addr(unsigned long addr) 979 { 980 int ret = 0; 981 982 if (addr < dac_mmap_min_addr) { 983 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, 984 SECURITY_CAP_AUDIT); 985 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 986 if (ret == 0) 987 current->flags |= PF_SUPERPRIV; 988 } 989 return ret; 990 } 991 992 int cap_mmap_file(struct file *file, unsigned long reqprot, 993 unsigned long prot, unsigned long flags) 994 { 995 return 0; 996 } 997