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 for (;;) { 80 /* The owner of the user namespace has all caps. */ 81 if (targ_ns != &init_user_ns && uid_eq(targ_ns->owner, cred->euid)) 82 return 0; 83 84 /* Do we have the necessary capabilities? */ 85 if (targ_ns == cred->user_ns) 86 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 87 88 /* Have we tried all of the parent namespaces? */ 89 if (targ_ns == &init_user_ns) 90 return -EPERM; 91 92 /* 93 *If you have a capability in a parent user ns, then you have 94 * it over all children user namespaces as well. 95 */ 96 targ_ns = targ_ns->parent; 97 } 98 99 /* We never get here */ 100 } 101 102 /** 103 * cap_settime - Determine whether the current process may set the system clock 104 * @ts: The time to set 105 * @tz: The timezone to set 106 * 107 * Determine whether the current process may set the system clock and timezone 108 * information, returning 0 if permission granted, -ve if denied. 109 */ 110 int cap_settime(const struct timespec *ts, const struct timezone *tz) 111 { 112 if (!capable(CAP_SYS_TIME)) 113 return -EPERM; 114 return 0; 115 } 116 117 /** 118 * cap_ptrace_access_check - Determine whether the current process may access 119 * another 120 * @child: The process to be accessed 121 * @mode: The mode of attachment. 122 * 123 * If we are in the same or an ancestor user_ns and have all the target 124 * task's capabilities, then ptrace access is allowed. 125 * If we have the ptrace capability to the target user_ns, then ptrace 126 * access is allowed. 127 * Else denied. 128 * 129 * Determine whether a process may access another, returning 0 if permission 130 * granted, -ve if denied. 131 */ 132 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 133 { 134 int ret = 0; 135 const struct cred *cred, *child_cred; 136 137 rcu_read_lock(); 138 cred = current_cred(); 139 child_cred = __task_cred(child); 140 if (cred->user_ns == child_cred->user_ns && 141 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 142 goto out; 143 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE)) 144 goto out; 145 ret = -EPERM; 146 out: 147 rcu_read_unlock(); 148 return ret; 149 } 150 151 /** 152 * cap_ptrace_traceme - Determine whether another process may trace the current 153 * @parent: The task proposed to be the tracer 154 * 155 * If parent is in the same or an ancestor user_ns and has all current's 156 * capabilities, then ptrace access is allowed. 157 * If parent has the ptrace capability to current's user_ns, then ptrace 158 * access is allowed. 159 * Else denied. 160 * 161 * Determine whether the nominated task is permitted to trace the current 162 * process, returning 0 if permission is granted, -ve if denied. 163 */ 164 int cap_ptrace_traceme(struct task_struct *parent) 165 { 166 int ret = 0; 167 const struct cred *cred, *child_cred; 168 169 rcu_read_lock(); 170 cred = __task_cred(parent); 171 child_cred = current_cred(); 172 if (cred->user_ns == child_cred->user_ns && 173 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 174 goto out; 175 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE)) 176 goto out; 177 ret = -EPERM; 178 out: 179 rcu_read_unlock(); 180 return ret; 181 } 182 183 /** 184 * cap_capget - Retrieve a task's capability sets 185 * @target: The task from which to retrieve the capability sets 186 * @effective: The place to record the effective set 187 * @inheritable: The place to record the inheritable set 188 * @permitted: The place to record the permitted set 189 * 190 * This function retrieves the capabilities of the nominated task and returns 191 * them to the caller. 192 */ 193 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 194 kernel_cap_t *inheritable, kernel_cap_t *permitted) 195 { 196 const struct cred *cred; 197 198 /* Derived from kernel/capability.c:sys_capget. */ 199 rcu_read_lock(); 200 cred = __task_cred(target); 201 *effective = cred->cap_effective; 202 *inheritable = cred->cap_inheritable; 203 *permitted = cred->cap_permitted; 204 rcu_read_unlock(); 205 return 0; 206 } 207 208 /* 209 * Determine whether the inheritable capabilities are limited to the old 210 * permitted set. Returns 1 if they are limited, 0 if they are not. 211 */ 212 static inline int cap_inh_is_capped(void) 213 { 214 215 /* they are so limited unless the current task has the CAP_SETPCAP 216 * capability 217 */ 218 if (cap_capable(current_cred(), current_cred()->user_ns, 219 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) 220 return 0; 221 return 1; 222 } 223 224 /** 225 * cap_capset - Validate and apply proposed changes to current's capabilities 226 * @new: The proposed new credentials; alterations should be made here 227 * @old: The current task's current credentials 228 * @effective: A pointer to the proposed new effective capabilities set 229 * @inheritable: A pointer to the proposed new inheritable capabilities set 230 * @permitted: A pointer to the proposed new permitted capabilities set 231 * 232 * This function validates and applies a proposed mass change to the current 233 * process's capability sets. The changes are made to the proposed new 234 * credentials, and assuming no error, will be committed by the caller of LSM. 235 */ 236 int cap_capset(struct cred *new, 237 const struct cred *old, 238 const kernel_cap_t *effective, 239 const kernel_cap_t *inheritable, 240 const kernel_cap_t *permitted) 241 { 242 if (cap_inh_is_capped() && 243 !cap_issubset(*inheritable, 244 cap_combine(old->cap_inheritable, 245 old->cap_permitted))) 246 /* incapable of using this inheritable set */ 247 return -EPERM; 248 249 if (!cap_issubset(*inheritable, 250 cap_combine(old->cap_inheritable, 251 old->cap_bset))) 252 /* no new pI capabilities outside bounding set */ 253 return -EPERM; 254 255 /* verify restrictions on target's new Permitted set */ 256 if (!cap_issubset(*permitted, old->cap_permitted)) 257 return -EPERM; 258 259 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 260 if (!cap_issubset(*effective, *permitted)) 261 return -EPERM; 262 263 new->cap_effective = *effective; 264 new->cap_inheritable = *inheritable; 265 new->cap_permitted = *permitted; 266 return 0; 267 } 268 269 /* 270 * Clear proposed capability sets for execve(). 271 */ 272 static inline void bprm_clear_caps(struct linux_binprm *bprm) 273 { 274 cap_clear(bprm->cred->cap_permitted); 275 bprm->cap_effective = false; 276 } 277 278 /** 279 * cap_inode_need_killpriv - Determine if inode change affects privileges 280 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 281 * 282 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 283 * affects the security markings on that inode, and if it is, should 284 * inode_killpriv() be invoked or the change rejected? 285 * 286 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 287 * -ve to deny the change. 288 */ 289 int cap_inode_need_killpriv(struct dentry *dentry) 290 { 291 struct inode *inode = dentry->d_inode; 292 int error; 293 294 if (!inode->i_op->getxattr) 295 return 0; 296 297 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 298 if (error <= 0) 299 return 0; 300 return 1; 301 } 302 303 /** 304 * cap_inode_killpriv - Erase the security markings on an inode 305 * @dentry: The inode/dentry to alter 306 * 307 * Erase the privilege-enhancing security markings on an inode. 308 * 309 * Returns 0 if successful, -ve on error. 310 */ 311 int cap_inode_killpriv(struct dentry *dentry) 312 { 313 struct inode *inode = dentry->d_inode; 314 315 if (!inode->i_op->removexattr) 316 return 0; 317 318 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 319 } 320 321 /* 322 * Calculate the new process capability sets from the capability sets attached 323 * to a file. 324 */ 325 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 326 struct linux_binprm *bprm, 327 bool *effective, 328 bool *has_cap) 329 { 330 struct cred *new = bprm->cred; 331 unsigned i; 332 int ret = 0; 333 334 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 335 *effective = true; 336 337 if (caps->magic_etc & VFS_CAP_REVISION_MASK) 338 *has_cap = true; 339 340 CAP_FOR_EACH_U32(i) { 341 __u32 permitted = caps->permitted.cap[i]; 342 __u32 inheritable = caps->inheritable.cap[i]; 343 344 /* 345 * pP' = (X & fP) | (pI & fI) 346 */ 347 new->cap_permitted.cap[i] = 348 (new->cap_bset.cap[i] & permitted) | 349 (new->cap_inheritable.cap[i] & inheritable); 350 351 if (permitted & ~new->cap_permitted.cap[i]) 352 /* insufficient to execute correctly */ 353 ret = -EPERM; 354 } 355 356 /* 357 * For legacy apps, with no internal support for recognizing they 358 * do not have enough capabilities, we return an error if they are 359 * missing some "forced" (aka file-permitted) capabilities. 360 */ 361 return *effective ? ret : 0; 362 } 363 364 /* 365 * Extract the on-exec-apply capability sets for an executable file. 366 */ 367 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 368 { 369 struct inode *inode = dentry->d_inode; 370 __u32 magic_etc; 371 unsigned tocopy, i; 372 int size; 373 struct vfs_cap_data caps; 374 375 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 376 377 if (!inode || !inode->i_op->getxattr) 378 return -ENODATA; 379 380 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 381 XATTR_CAPS_SZ); 382 if (size == -ENODATA || size == -EOPNOTSUPP) 383 /* no data, that's ok */ 384 return -ENODATA; 385 if (size < 0) 386 return size; 387 388 if (size < sizeof(magic_etc)) 389 return -EINVAL; 390 391 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 392 393 switch (magic_etc & VFS_CAP_REVISION_MASK) { 394 case VFS_CAP_REVISION_1: 395 if (size != XATTR_CAPS_SZ_1) 396 return -EINVAL; 397 tocopy = VFS_CAP_U32_1; 398 break; 399 case VFS_CAP_REVISION_2: 400 if (size != XATTR_CAPS_SZ_2) 401 return -EINVAL; 402 tocopy = VFS_CAP_U32_2; 403 break; 404 default: 405 return -EINVAL; 406 } 407 408 CAP_FOR_EACH_U32(i) { 409 if (i >= tocopy) 410 break; 411 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 412 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 413 } 414 415 return 0; 416 } 417 418 /* 419 * Attempt to get the on-exec apply capability sets for an executable file from 420 * its xattrs and, if present, apply them to the proposed credentials being 421 * constructed by execve(). 422 */ 423 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) 424 { 425 struct dentry *dentry; 426 int rc = 0; 427 struct cpu_vfs_cap_data vcaps; 428 429 bprm_clear_caps(bprm); 430 431 if (!file_caps_enabled) 432 return 0; 433 434 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) 435 return 0; 436 437 dentry = dget(bprm->file->f_dentry); 438 439 rc = get_vfs_caps_from_disk(dentry, &vcaps); 440 if (rc < 0) { 441 if (rc == -EINVAL) 442 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 443 __func__, rc, bprm->filename); 444 else if (rc == -ENODATA) 445 rc = 0; 446 goto out; 447 } 448 449 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); 450 if (rc == -EINVAL) 451 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 452 __func__, rc, bprm->filename); 453 454 out: 455 dput(dentry); 456 if (rc) 457 bprm_clear_caps(bprm); 458 459 return rc; 460 } 461 462 /** 463 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 464 * @bprm: The execution parameters, including the proposed creds 465 * 466 * Set up the proposed credentials for a new execution context being 467 * constructed by execve(). The proposed creds in @bprm->cred is altered, 468 * which won't take effect immediately. Returns 0 if successful, -ve on error. 469 */ 470 int cap_bprm_set_creds(struct linux_binprm *bprm) 471 { 472 const struct cred *old = current_cred(); 473 struct cred *new = bprm->cred; 474 bool effective, has_cap = false; 475 int ret; 476 kuid_t root_uid; 477 478 effective = false; 479 ret = get_file_caps(bprm, &effective, &has_cap); 480 if (ret < 0) 481 return ret; 482 483 root_uid = make_kuid(new->user_ns, 0); 484 485 if (!issecure(SECURE_NOROOT)) { 486 /* 487 * If the legacy file capability is set, then don't set privs 488 * for a setuid root binary run by a non-root user. Do set it 489 * for a root user just to cause least surprise to an admin. 490 */ 491 if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) { 492 warn_setuid_and_fcaps_mixed(bprm->filename); 493 goto skip; 494 } 495 /* 496 * To support inheritance of root-permissions and suid-root 497 * executables under compatibility mode, we override the 498 * capability sets for the file. 499 * 500 * If only the real uid is 0, we do not set the effective bit. 501 */ 502 if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) { 503 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 504 new->cap_permitted = cap_combine(old->cap_bset, 505 old->cap_inheritable); 506 } 507 if (uid_eq(new->euid, root_uid)) 508 effective = true; 509 } 510 skip: 511 512 /* if we have fs caps, clear dangerous personality flags */ 513 if (!cap_issubset(new->cap_permitted, old->cap_permitted)) 514 bprm->per_clear |= PER_CLEAR_ON_SETID; 515 516 517 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 518 * credentials unless they have the appropriate permit. 519 * 520 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. 521 */ 522 if ((!uid_eq(new->euid, old->uid) || 523 !gid_eq(new->egid, old->gid) || 524 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 525 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 526 /* downgrade; they get no more than they had, and maybe less */ 527 if (!capable(CAP_SETUID) || 528 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { 529 new->euid = new->uid; 530 new->egid = new->gid; 531 } 532 new->cap_permitted = cap_intersect(new->cap_permitted, 533 old->cap_permitted); 534 } 535 536 new->suid = new->fsuid = new->euid; 537 new->sgid = new->fsgid = new->egid; 538 539 if (effective) 540 new->cap_effective = new->cap_permitted; 541 else 542 cap_clear(new->cap_effective); 543 bprm->cap_effective = effective; 544 545 /* 546 * Audit candidate if current->cap_effective is set 547 * 548 * We do not bother to audit if 3 things are true: 549 * 1) cap_effective has all caps 550 * 2) we are root 551 * 3) root is supposed to have all caps (SECURE_NOROOT) 552 * Since this is just a normal root execing a process. 553 * 554 * Number 1 above might fail if you don't have a full bset, but I think 555 * that is interesting information to audit. 556 */ 557 if (!cap_isclear(new->cap_effective)) { 558 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 559 !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) || 560 issecure(SECURE_NOROOT)) { 561 ret = audit_log_bprm_fcaps(bprm, new, old); 562 if (ret < 0) 563 return ret; 564 } 565 } 566 567 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 568 return 0; 569 } 570 571 /** 572 * cap_bprm_secureexec - Determine whether a secure execution is required 573 * @bprm: The execution parameters 574 * 575 * Determine whether a secure execution is required, return 1 if it is, and 0 576 * if it is not. 577 * 578 * The credentials have been committed by this point, and so are no longer 579 * available through @bprm->cred. 580 */ 581 int cap_bprm_secureexec(struct linux_binprm *bprm) 582 { 583 const struct cred *cred = current_cred(); 584 kuid_t root_uid = make_kuid(cred->user_ns, 0); 585 586 if (!uid_eq(cred->uid, root_uid)) { 587 if (bprm->cap_effective) 588 return 1; 589 if (!cap_isclear(cred->cap_permitted)) 590 return 1; 591 } 592 593 return (!uid_eq(cred->euid, cred->uid) || 594 !gid_eq(cred->egid, cred->gid)); 595 } 596 597 /** 598 * cap_inode_setxattr - Determine whether an xattr may be altered 599 * @dentry: The inode/dentry being altered 600 * @name: The name of the xattr to be changed 601 * @value: The value that the xattr will be changed to 602 * @size: The size of value 603 * @flags: The replacement flag 604 * 605 * Determine whether an xattr may be altered or set on an inode, returning 0 if 606 * permission is granted, -ve if denied. 607 * 608 * This is used to make sure security xattrs don't get updated or set by those 609 * who aren't privileged to do so. 610 */ 611 int cap_inode_setxattr(struct dentry *dentry, const char *name, 612 const void *value, size_t size, int flags) 613 { 614 if (!strcmp(name, XATTR_NAME_CAPS)) { 615 if (!capable(CAP_SETFCAP)) 616 return -EPERM; 617 return 0; 618 } 619 620 if (!strncmp(name, XATTR_SECURITY_PREFIX, 621 sizeof(XATTR_SECURITY_PREFIX) - 1) && 622 !capable(CAP_SYS_ADMIN)) 623 return -EPERM; 624 return 0; 625 } 626 627 /** 628 * cap_inode_removexattr - Determine whether an xattr may be removed 629 * @dentry: The inode/dentry being altered 630 * @name: The name of the xattr to be changed 631 * 632 * Determine whether an xattr may be removed from an inode, returning 0 if 633 * permission is granted, -ve if denied. 634 * 635 * This is used to make sure security xattrs don't get removed by those who 636 * aren't privileged to remove them. 637 */ 638 int cap_inode_removexattr(struct dentry *dentry, const char *name) 639 { 640 if (!strcmp(name, XATTR_NAME_CAPS)) { 641 if (!capable(CAP_SETFCAP)) 642 return -EPERM; 643 return 0; 644 } 645 646 if (!strncmp(name, XATTR_SECURITY_PREFIX, 647 sizeof(XATTR_SECURITY_PREFIX) - 1) && 648 !capable(CAP_SYS_ADMIN)) 649 return -EPERM; 650 return 0; 651 } 652 653 /* 654 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 655 * a process after a call to setuid, setreuid, or setresuid. 656 * 657 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 658 * {r,e,s}uid != 0, the permitted and effective capabilities are 659 * cleared. 660 * 661 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 662 * capabilities of the process are cleared. 663 * 664 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 665 * capabilities are set to the permitted capabilities. 666 * 667 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 668 * never happen. 669 * 670 * -astor 671 * 672 * cevans - New behaviour, Oct '99 673 * A process may, via prctl(), elect to keep its capabilities when it 674 * calls setuid() and switches away from uid==0. Both permitted and 675 * effective sets will be retained. 676 * Without this change, it was impossible for a daemon to drop only some 677 * of its privilege. The call to setuid(!=0) would drop all privileges! 678 * Keeping uid 0 is not an option because uid 0 owns too many vital 679 * files.. 680 * Thanks to Olaf Kirch and Peter Benie for spotting this. 681 */ 682 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 683 { 684 kuid_t root_uid = make_kuid(old->user_ns, 0); 685 686 if ((uid_eq(old->uid, root_uid) || 687 uid_eq(old->euid, root_uid) || 688 uid_eq(old->suid, root_uid)) && 689 (!uid_eq(new->uid, root_uid) && 690 !uid_eq(new->euid, root_uid) && 691 !uid_eq(new->suid, root_uid)) && 692 !issecure(SECURE_KEEP_CAPS)) { 693 cap_clear(new->cap_permitted); 694 cap_clear(new->cap_effective); 695 } 696 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) 697 cap_clear(new->cap_effective); 698 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) 699 new->cap_effective = new->cap_permitted; 700 } 701 702 /** 703 * cap_task_fix_setuid - Fix up the results of setuid() call 704 * @new: The proposed credentials 705 * @old: The current task's current credentials 706 * @flags: Indications of what has changed 707 * 708 * Fix up the results of setuid() call before the credential changes are 709 * actually applied, returning 0 to grant the changes, -ve to deny them. 710 */ 711 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 712 { 713 switch (flags) { 714 case LSM_SETID_RE: 715 case LSM_SETID_ID: 716 case LSM_SETID_RES: 717 /* juggle the capabilities to follow [RES]UID changes unless 718 * otherwise suppressed */ 719 if (!issecure(SECURE_NO_SETUID_FIXUP)) 720 cap_emulate_setxuid(new, old); 721 break; 722 723 case LSM_SETID_FS: 724 /* juggle the capabilties to follow FSUID changes, unless 725 * otherwise suppressed 726 * 727 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 728 * if not, we might be a bit too harsh here. 729 */ 730 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 731 kuid_t root_uid = make_kuid(old->user_ns, 0); 732 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) 733 new->cap_effective = 734 cap_drop_fs_set(new->cap_effective); 735 736 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) 737 new->cap_effective = 738 cap_raise_fs_set(new->cap_effective, 739 new->cap_permitted); 740 } 741 break; 742 743 default: 744 return -EINVAL; 745 } 746 747 return 0; 748 } 749 750 /* 751 * Rationale: code calling task_setscheduler, task_setioprio, and 752 * task_setnice, assumes that 753 * . if capable(cap_sys_nice), then those actions should be allowed 754 * . if not capable(cap_sys_nice), but acting on your own processes, 755 * then those actions should be allowed 756 * This is insufficient now since you can call code without suid, but 757 * yet with increased caps. 758 * So we check for increased caps on the target process. 759 */ 760 static int cap_safe_nice(struct task_struct *p) 761 { 762 int is_subset; 763 764 rcu_read_lock(); 765 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 766 current_cred()->cap_permitted); 767 rcu_read_unlock(); 768 769 if (!is_subset && !capable(CAP_SYS_NICE)) 770 return -EPERM; 771 return 0; 772 } 773 774 /** 775 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 776 * @p: The task to affect 777 * 778 * Detemine if the requested scheduler policy change is permitted for the 779 * specified task, returning 0 if permission is granted, -ve if denied. 780 */ 781 int cap_task_setscheduler(struct task_struct *p) 782 { 783 return cap_safe_nice(p); 784 } 785 786 /** 787 * cap_task_ioprio - Detemine if I/O priority change is permitted 788 * @p: The task to affect 789 * @ioprio: The I/O priority to set 790 * 791 * Detemine if the requested I/O priority change is permitted for the specified 792 * task, returning 0 if permission is granted, -ve if denied. 793 */ 794 int cap_task_setioprio(struct task_struct *p, int ioprio) 795 { 796 return cap_safe_nice(p); 797 } 798 799 /** 800 * cap_task_ioprio - Detemine if task priority change is permitted 801 * @p: The task to affect 802 * @nice: The nice value to set 803 * 804 * Detemine if the requested task priority change is permitted for the 805 * specified task, returning 0 if permission is granted, -ve if denied. 806 */ 807 int cap_task_setnice(struct task_struct *p, int nice) 808 { 809 return cap_safe_nice(p); 810 } 811 812 /* 813 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 814 * the current task's bounding set. Returns 0 on success, -ve on error. 815 */ 816 static long cap_prctl_drop(struct cred *new, unsigned long cap) 817 { 818 if (!capable(CAP_SETPCAP)) 819 return -EPERM; 820 if (!cap_valid(cap)) 821 return -EINVAL; 822 823 cap_lower(new->cap_bset, cap); 824 return 0; 825 } 826 827 /** 828 * cap_task_prctl - Implement process control functions for this security module 829 * @option: The process control function requested 830 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 831 * 832 * Allow process control functions (sys_prctl()) to alter capabilities; may 833 * also deny access to other functions not otherwise implemented here. 834 * 835 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 836 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 837 * modules will consider performing the function. 838 */ 839 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 840 unsigned long arg4, unsigned long arg5) 841 { 842 struct cred *new; 843 long error = 0; 844 845 new = prepare_creds(); 846 if (!new) 847 return -ENOMEM; 848 849 switch (option) { 850 case PR_CAPBSET_READ: 851 error = -EINVAL; 852 if (!cap_valid(arg2)) 853 goto error; 854 error = !!cap_raised(new->cap_bset, arg2); 855 goto no_change; 856 857 case PR_CAPBSET_DROP: 858 error = cap_prctl_drop(new, arg2); 859 if (error < 0) 860 goto error; 861 goto changed; 862 863 /* 864 * The next four prctl's remain to assist with transitioning a 865 * system from legacy UID=0 based privilege (when filesystem 866 * capabilities are not in use) to a system using filesystem 867 * capabilities only - as the POSIX.1e draft intended. 868 * 869 * Note: 870 * 871 * PR_SET_SECUREBITS = 872 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 873 * | issecure_mask(SECURE_NOROOT) 874 * | issecure_mask(SECURE_NOROOT_LOCKED) 875 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 876 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 877 * 878 * will ensure that the current process and all of its 879 * children will be locked into a pure 880 * capability-based-privilege environment. 881 */ 882 case PR_SET_SECUREBITS: 883 error = -EPERM; 884 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 885 & (new->securebits ^ arg2)) /*[1]*/ 886 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 887 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 888 || (cap_capable(current_cred(), 889 current_cred()->user_ns, CAP_SETPCAP, 890 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 891 /* 892 * [1] no changing of bits that are locked 893 * [2] no unlocking of locks 894 * [3] no setting of unsupported bits 895 * [4] doing anything requires privilege (go read about 896 * the "sendmail capabilities bug") 897 */ 898 ) 899 /* cannot change a locked bit */ 900 goto error; 901 new->securebits = arg2; 902 goto changed; 903 904 case PR_GET_SECUREBITS: 905 error = new->securebits; 906 goto no_change; 907 908 case PR_GET_KEEPCAPS: 909 if (issecure(SECURE_KEEP_CAPS)) 910 error = 1; 911 goto no_change; 912 913 case PR_SET_KEEPCAPS: 914 error = -EINVAL; 915 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 916 goto error; 917 error = -EPERM; 918 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 919 goto error; 920 if (arg2) 921 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 922 else 923 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 924 goto changed; 925 926 default: 927 /* No functionality available - continue with default */ 928 error = -ENOSYS; 929 goto error; 930 } 931 932 /* Functionality provided */ 933 changed: 934 return commit_creds(new); 935 936 no_change: 937 error: 938 abort_creds(new); 939 return error; 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