1 /* Common capabilities, needed by capability.o and root_plug.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 31 /* 32 * If a non-root user executes a setuid-root binary in 33 * !secure(SECURE_NOROOT) mode, then we raise capabilities. 34 * However if fE is also set, then the intent is for only 35 * the file capabilities to be applied, and the setuid-root 36 * bit is left on either to change the uid (plausible) or 37 * to get full privilege on a kernel without file capabilities 38 * support. So in that case we do not raise capabilities. 39 * 40 * Warn if that happens, once per boot. 41 */ 42 static void warn_setuid_and_fcaps_mixed(char *fname) 43 { 44 static int warned; 45 if (!warned) { 46 printk(KERN_INFO "warning: `%s' has both setuid-root and" 47 " effective capabilities. Therefore not raising all" 48 " capabilities.\n", fname); 49 warned = 1; 50 } 51 } 52 53 int cap_netlink_send(struct sock *sk, struct sk_buff *skb) 54 { 55 NETLINK_CB(skb).eff_cap = current_cap(); 56 return 0; 57 } 58 59 int cap_netlink_recv(struct sk_buff *skb, int cap) 60 { 61 if (!cap_raised(NETLINK_CB(skb).eff_cap, cap)) 62 return -EPERM; 63 return 0; 64 } 65 EXPORT_SYMBOL(cap_netlink_recv); 66 67 /** 68 * cap_capable - Determine whether a task has a particular effective capability 69 * @tsk: The task to query 70 * @cred: The credentials to use 71 * @cap: The capability to check for 72 * @audit: Whether to write an audit message or not 73 * 74 * Determine whether the nominated task has the specified capability amongst 75 * its effective set, returning 0 if it does, -ve if it does not. 76 * 77 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() 78 * and has_capability() functions. That is, it has the reverse semantics: 79 * cap_has_capability() returns 0 when a task has a capability, but the 80 * kernel's capable() and has_capability() returns 1 for this case. 81 */ 82 int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap, 83 int audit) 84 { 85 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 86 } 87 88 /** 89 * cap_settime - Determine whether the current process may set the system clock 90 * @ts: The time to set 91 * @tz: The timezone to set 92 * 93 * Determine whether the current process may set the system clock and timezone 94 * information, returning 0 if permission granted, -ve if denied. 95 */ 96 int cap_settime(struct timespec *ts, struct timezone *tz) 97 { 98 if (!capable(CAP_SYS_TIME)) 99 return -EPERM; 100 return 0; 101 } 102 103 /** 104 * cap_ptrace_access_check - Determine whether the current process may access 105 * another 106 * @child: The process to be accessed 107 * @mode: The mode of attachment. 108 * 109 * Determine whether a process may access another, returning 0 if permission 110 * granted, -ve if denied. 111 */ 112 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 113 { 114 int ret = 0; 115 116 rcu_read_lock(); 117 if (!cap_issubset(__task_cred(child)->cap_permitted, 118 current_cred()->cap_permitted) && 119 !capable(CAP_SYS_PTRACE)) 120 ret = -EPERM; 121 rcu_read_unlock(); 122 return ret; 123 } 124 125 /** 126 * cap_ptrace_traceme - Determine whether another process may trace the current 127 * @parent: The task proposed to be the tracer 128 * 129 * Determine whether the nominated task is permitted to trace the current 130 * process, returning 0 if permission is granted, -ve if denied. 131 */ 132 int cap_ptrace_traceme(struct task_struct *parent) 133 { 134 int ret = 0; 135 136 rcu_read_lock(); 137 if (!cap_issubset(current_cred()->cap_permitted, 138 __task_cred(parent)->cap_permitted) && 139 !has_capability(parent, CAP_SYS_PTRACE)) 140 ret = -EPERM; 141 rcu_read_unlock(); 142 return ret; 143 } 144 145 /** 146 * cap_capget - Retrieve a task's capability sets 147 * @target: The task from which to retrieve the capability sets 148 * @effective: The place to record the effective set 149 * @inheritable: The place to record the inheritable set 150 * @permitted: The place to record the permitted set 151 * 152 * This function retrieves the capabilities of the nominated task and returns 153 * them to the caller. 154 */ 155 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 156 kernel_cap_t *inheritable, kernel_cap_t *permitted) 157 { 158 const struct cred *cred; 159 160 /* Derived from kernel/capability.c:sys_capget. */ 161 rcu_read_lock(); 162 cred = __task_cred(target); 163 *effective = cred->cap_effective; 164 *inheritable = cred->cap_inheritable; 165 *permitted = cred->cap_permitted; 166 rcu_read_unlock(); 167 return 0; 168 } 169 170 /* 171 * Determine whether the inheritable capabilities are limited to the old 172 * permitted set. Returns 1 if they are limited, 0 if they are not. 173 */ 174 static inline int cap_inh_is_capped(void) 175 { 176 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 177 178 /* they are so limited unless the current task has the CAP_SETPCAP 179 * capability 180 */ 181 if (cap_capable(current, current_cred(), CAP_SETPCAP, 182 SECURITY_CAP_AUDIT) == 0) 183 return 0; 184 #endif 185 return 1; 186 } 187 188 /** 189 * cap_capset - Validate and apply proposed changes to current's capabilities 190 * @new: The proposed new credentials; alterations should be made here 191 * @old: The current task's current credentials 192 * @effective: A pointer to the proposed new effective capabilities set 193 * @inheritable: A pointer to the proposed new inheritable capabilities set 194 * @permitted: A pointer to the proposed new permitted capabilities set 195 * 196 * This function validates and applies a proposed mass change to the current 197 * process's capability sets. The changes are made to the proposed new 198 * credentials, and assuming no error, will be committed by the caller of LSM. 199 */ 200 int cap_capset(struct cred *new, 201 const struct cred *old, 202 const kernel_cap_t *effective, 203 const kernel_cap_t *inheritable, 204 const kernel_cap_t *permitted) 205 { 206 if (cap_inh_is_capped() && 207 !cap_issubset(*inheritable, 208 cap_combine(old->cap_inheritable, 209 old->cap_permitted))) 210 /* incapable of using this inheritable set */ 211 return -EPERM; 212 213 if (!cap_issubset(*inheritable, 214 cap_combine(old->cap_inheritable, 215 old->cap_bset))) 216 /* no new pI capabilities outside bounding set */ 217 return -EPERM; 218 219 /* verify restrictions on target's new Permitted set */ 220 if (!cap_issubset(*permitted, old->cap_permitted)) 221 return -EPERM; 222 223 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 224 if (!cap_issubset(*effective, *permitted)) 225 return -EPERM; 226 227 new->cap_effective = *effective; 228 new->cap_inheritable = *inheritable; 229 new->cap_permitted = *permitted; 230 return 0; 231 } 232 233 /* 234 * Clear proposed capability sets for execve(). 235 */ 236 static inline void bprm_clear_caps(struct linux_binprm *bprm) 237 { 238 cap_clear(bprm->cred->cap_permitted); 239 bprm->cap_effective = false; 240 } 241 242 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 243 244 /** 245 * cap_inode_need_killpriv - Determine if inode change affects privileges 246 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 247 * 248 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 249 * affects the security markings on that inode, and if it is, should 250 * inode_killpriv() be invoked or the change rejected? 251 * 252 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 253 * -ve to deny the change. 254 */ 255 int cap_inode_need_killpriv(struct dentry *dentry) 256 { 257 struct inode *inode = dentry->d_inode; 258 int error; 259 260 if (!inode->i_op->getxattr) 261 return 0; 262 263 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 264 if (error <= 0) 265 return 0; 266 return 1; 267 } 268 269 /** 270 * cap_inode_killpriv - Erase the security markings on an inode 271 * @dentry: The inode/dentry to alter 272 * 273 * Erase the privilege-enhancing security markings on an inode. 274 * 275 * Returns 0 if successful, -ve on error. 276 */ 277 int cap_inode_killpriv(struct dentry *dentry) 278 { 279 struct inode *inode = dentry->d_inode; 280 281 if (!inode->i_op->removexattr) 282 return 0; 283 284 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 285 } 286 287 /* 288 * Calculate the new process capability sets from the capability sets attached 289 * to a file. 290 */ 291 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 292 struct linux_binprm *bprm, 293 bool *effective) 294 { 295 struct cred *new = bprm->cred; 296 unsigned i; 297 int ret = 0; 298 299 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 300 *effective = true; 301 302 CAP_FOR_EACH_U32(i) { 303 __u32 permitted = caps->permitted.cap[i]; 304 __u32 inheritable = caps->inheritable.cap[i]; 305 306 /* 307 * pP' = (X & fP) | (pI & fI) 308 */ 309 new->cap_permitted.cap[i] = 310 (new->cap_bset.cap[i] & permitted) | 311 (new->cap_inheritable.cap[i] & inheritable); 312 313 if (permitted & ~new->cap_permitted.cap[i]) 314 /* insufficient to execute correctly */ 315 ret = -EPERM; 316 } 317 318 /* 319 * For legacy apps, with no internal support for recognizing they 320 * do not have enough capabilities, we return an error if they are 321 * missing some "forced" (aka file-permitted) capabilities. 322 */ 323 return *effective ? ret : 0; 324 } 325 326 /* 327 * Extract the on-exec-apply capability sets for an executable file. 328 */ 329 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 330 { 331 struct inode *inode = dentry->d_inode; 332 __u32 magic_etc; 333 unsigned tocopy, i; 334 int size; 335 struct vfs_cap_data caps; 336 337 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 338 339 if (!inode || !inode->i_op->getxattr) 340 return -ENODATA; 341 342 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 343 XATTR_CAPS_SZ); 344 if (size == -ENODATA || size == -EOPNOTSUPP) 345 /* no data, that's ok */ 346 return -ENODATA; 347 if (size < 0) 348 return size; 349 350 if (size < sizeof(magic_etc)) 351 return -EINVAL; 352 353 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 354 355 switch (magic_etc & VFS_CAP_REVISION_MASK) { 356 case VFS_CAP_REVISION_1: 357 if (size != XATTR_CAPS_SZ_1) 358 return -EINVAL; 359 tocopy = VFS_CAP_U32_1; 360 break; 361 case VFS_CAP_REVISION_2: 362 if (size != XATTR_CAPS_SZ_2) 363 return -EINVAL; 364 tocopy = VFS_CAP_U32_2; 365 break; 366 default: 367 return -EINVAL; 368 } 369 370 CAP_FOR_EACH_U32(i) { 371 if (i >= tocopy) 372 break; 373 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 374 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 375 } 376 377 return 0; 378 } 379 380 /* 381 * Attempt to get the on-exec apply capability sets for an executable file from 382 * its xattrs and, if present, apply them to the proposed credentials being 383 * constructed by execve(). 384 */ 385 static int get_file_caps(struct linux_binprm *bprm, bool *effective) 386 { 387 struct dentry *dentry; 388 int rc = 0; 389 struct cpu_vfs_cap_data vcaps; 390 391 bprm_clear_caps(bprm); 392 393 if (!file_caps_enabled) 394 return 0; 395 396 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) 397 return 0; 398 399 dentry = dget(bprm->file->f_dentry); 400 401 rc = get_vfs_caps_from_disk(dentry, &vcaps); 402 if (rc < 0) { 403 if (rc == -EINVAL) 404 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 405 __func__, rc, bprm->filename); 406 else if (rc == -ENODATA) 407 rc = 0; 408 goto out; 409 } 410 411 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective); 412 if (rc == -EINVAL) 413 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 414 __func__, rc, bprm->filename); 415 416 out: 417 dput(dentry); 418 if (rc) 419 bprm_clear_caps(bprm); 420 421 return rc; 422 } 423 424 #else 425 int cap_inode_need_killpriv(struct dentry *dentry) 426 { 427 return 0; 428 } 429 430 int cap_inode_killpriv(struct dentry *dentry) 431 { 432 return 0; 433 } 434 435 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 436 { 437 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 438 return -ENODATA; 439 } 440 441 static inline int get_file_caps(struct linux_binprm *bprm, bool *effective) 442 { 443 bprm_clear_caps(bprm); 444 return 0; 445 } 446 #endif 447 448 /* 449 * Determine whether a exec'ing process's new permitted capabilities should be 450 * limited to just what it already has. 451 * 452 * This prevents processes that are being ptraced from gaining access to 453 * CAP_SETPCAP, unless the process they're tracing already has it, and the 454 * binary they're executing has filecaps that elevate it. 455 * 456 * Returns 1 if they should be limited, 0 if they are not. 457 */ 458 static inline int cap_limit_ptraced_target(void) 459 { 460 #ifndef CONFIG_SECURITY_FILE_CAPABILITIES 461 if (capable(CAP_SETPCAP)) 462 return 0; 463 #endif 464 return 1; 465 } 466 467 /** 468 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 469 * @bprm: The execution parameters, including the proposed creds 470 * 471 * Set up the proposed credentials for a new execution context being 472 * constructed by execve(). The proposed creds in @bprm->cred is altered, 473 * which won't take effect immediately. Returns 0 if successful, -ve on error. 474 */ 475 int cap_bprm_set_creds(struct linux_binprm *bprm) 476 { 477 const struct cred *old = current_cred(); 478 struct cred *new = bprm->cred; 479 bool effective; 480 int ret; 481 482 effective = false; 483 ret = get_file_caps(bprm, &effective); 484 if (ret < 0) 485 return ret; 486 487 if (!issecure(SECURE_NOROOT)) { 488 /* 489 * If the legacy file capability is set, then don't set privs 490 * for a setuid root binary run by a non-root user. Do set it 491 * for a root user just to cause least surprise to an admin. 492 */ 493 if (effective && new->uid != 0 && new->euid == 0) { 494 warn_setuid_and_fcaps_mixed(bprm->filename); 495 goto skip; 496 } 497 /* 498 * To support inheritance of root-permissions and suid-root 499 * executables under compatibility mode, we override the 500 * capability sets for the file. 501 * 502 * If only the real uid is 0, we do not set the effective bit. 503 */ 504 if (new->euid == 0 || new->uid == 0) { 505 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 506 new->cap_permitted = cap_combine(old->cap_bset, 507 old->cap_inheritable); 508 } 509 if (new->euid == 0) 510 effective = true; 511 } 512 skip: 513 514 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 515 * credentials unless they have the appropriate permit 516 */ 517 if ((new->euid != old->uid || 518 new->egid != old->gid || 519 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 520 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 521 /* downgrade; they get no more than they had, and maybe less */ 522 if (!capable(CAP_SETUID)) { 523 new->euid = new->uid; 524 new->egid = new->gid; 525 } 526 if (cap_limit_ptraced_target()) 527 new->cap_permitted = cap_intersect(new->cap_permitted, 528 old->cap_permitted); 529 } 530 531 new->suid = new->fsuid = new->euid; 532 new->sgid = new->fsgid = new->egid; 533 534 /* For init, we want to retain the capabilities set in the initial 535 * task. Thus we skip the usual capability rules 536 */ 537 if (!is_global_init(current)) { 538 if (effective) 539 new->cap_effective = new->cap_permitted; 540 else 541 cap_clear(new->cap_effective); 542 } 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 new->euid != 0 || new->uid != 0 || 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(); 584 585 if (cred->uid != 0) { 586 if (bprm->cap_effective) 587 return 1; 588 if (!cap_isclear(cred->cap_permitted)) 589 return 1; 590 } 591 592 return (cred->euid != cred->uid || 593 cred->egid != cred->gid); 594 } 595 596 /** 597 * cap_inode_setxattr - Determine whether an xattr may be altered 598 * @dentry: The inode/dentry being altered 599 * @name: The name of the xattr to be changed 600 * @value: The value that the xattr will be changed to 601 * @size: The size of value 602 * @flags: The replacement flag 603 * 604 * Determine whether an xattr may be altered or set on an inode, returning 0 if 605 * permission is granted, -ve if denied. 606 * 607 * This is used to make sure security xattrs don't get updated or set by those 608 * who aren't privileged to do so. 609 */ 610 int cap_inode_setxattr(struct dentry *dentry, const char *name, 611 const void *value, size_t size, int flags) 612 { 613 if (!strcmp(name, XATTR_NAME_CAPS)) { 614 if (!capable(CAP_SETFCAP)) 615 return -EPERM; 616 return 0; 617 } 618 619 if (!strncmp(name, XATTR_SECURITY_PREFIX, 620 sizeof(XATTR_SECURITY_PREFIX) - 1) && 621 !capable(CAP_SYS_ADMIN)) 622 return -EPERM; 623 return 0; 624 } 625 626 /** 627 * cap_inode_removexattr - Determine whether an xattr may be removed 628 * @dentry: The inode/dentry being altered 629 * @name: The name of the xattr to be changed 630 * 631 * Determine whether an xattr may be removed from an inode, returning 0 if 632 * permission is granted, -ve if denied. 633 * 634 * This is used to make sure security xattrs don't get removed by those who 635 * aren't privileged to remove them. 636 */ 637 int cap_inode_removexattr(struct dentry *dentry, const char *name) 638 { 639 if (!strcmp(name, XATTR_NAME_CAPS)) { 640 if (!capable(CAP_SETFCAP)) 641 return -EPERM; 642 return 0; 643 } 644 645 if (!strncmp(name, XATTR_SECURITY_PREFIX, 646 sizeof(XATTR_SECURITY_PREFIX) - 1) && 647 !capable(CAP_SYS_ADMIN)) 648 return -EPERM; 649 return 0; 650 } 651 652 /* 653 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 654 * a process after a call to setuid, setreuid, or setresuid. 655 * 656 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 657 * {r,e,s}uid != 0, the permitted and effective capabilities are 658 * cleared. 659 * 660 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 661 * capabilities of the process are cleared. 662 * 663 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 664 * capabilities are set to the permitted capabilities. 665 * 666 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 667 * never happen. 668 * 669 * -astor 670 * 671 * cevans - New behaviour, Oct '99 672 * A process may, via prctl(), elect to keep its capabilities when it 673 * calls setuid() and switches away from uid==0. Both permitted and 674 * effective sets will be retained. 675 * Without this change, it was impossible for a daemon to drop only some 676 * of its privilege. The call to setuid(!=0) would drop all privileges! 677 * Keeping uid 0 is not an option because uid 0 owns too many vital 678 * files.. 679 * Thanks to Olaf Kirch and Peter Benie for spotting this. 680 */ 681 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 682 { 683 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && 684 (new->uid != 0 && new->euid != 0 && new->suid != 0) && 685 !issecure(SECURE_KEEP_CAPS)) { 686 cap_clear(new->cap_permitted); 687 cap_clear(new->cap_effective); 688 } 689 if (old->euid == 0 && new->euid != 0) 690 cap_clear(new->cap_effective); 691 if (old->euid != 0 && new->euid == 0) 692 new->cap_effective = new->cap_permitted; 693 } 694 695 /** 696 * cap_task_fix_setuid - Fix up the results of setuid() call 697 * @new: The proposed credentials 698 * @old: The current task's current credentials 699 * @flags: Indications of what has changed 700 * 701 * Fix up the results of setuid() call before the credential changes are 702 * actually applied, returning 0 to grant the changes, -ve to deny them. 703 */ 704 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 705 { 706 switch (flags) { 707 case LSM_SETID_RE: 708 case LSM_SETID_ID: 709 case LSM_SETID_RES: 710 /* juggle the capabilities to follow [RES]UID changes unless 711 * otherwise suppressed */ 712 if (!issecure(SECURE_NO_SETUID_FIXUP)) 713 cap_emulate_setxuid(new, old); 714 break; 715 716 case LSM_SETID_FS: 717 /* juggle the capabilties to follow FSUID changes, unless 718 * otherwise suppressed 719 * 720 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 721 * if not, we might be a bit too harsh here. 722 */ 723 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 724 if (old->fsuid == 0 && new->fsuid != 0) 725 new->cap_effective = 726 cap_drop_fs_set(new->cap_effective); 727 728 if (old->fsuid != 0 && new->fsuid == 0) 729 new->cap_effective = 730 cap_raise_fs_set(new->cap_effective, 731 new->cap_permitted); 732 } 733 break; 734 735 default: 736 return -EINVAL; 737 } 738 739 return 0; 740 } 741 742 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 743 /* 744 * Rationale: code calling task_setscheduler, task_setioprio, and 745 * task_setnice, assumes that 746 * . if capable(cap_sys_nice), then those actions should be allowed 747 * . if not capable(cap_sys_nice), but acting on your own processes, 748 * then those actions should be allowed 749 * This is insufficient now since you can call code without suid, but 750 * yet with increased caps. 751 * So we check for increased caps on the target process. 752 */ 753 static int cap_safe_nice(struct task_struct *p) 754 { 755 int is_subset; 756 757 rcu_read_lock(); 758 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 759 current_cred()->cap_permitted); 760 rcu_read_unlock(); 761 762 if (!is_subset && !capable(CAP_SYS_NICE)) 763 return -EPERM; 764 return 0; 765 } 766 767 /** 768 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 769 * @p: The task to affect 770 * @policy: The policy to effect 771 * @lp: The parameters to the scheduling policy 772 * 773 * Detemine if the requested scheduler policy change is permitted for the 774 * specified task, returning 0 if permission is granted, -ve if denied. 775 */ 776 int cap_task_setscheduler(struct task_struct *p, int policy, 777 struct sched_param *lp) 778 { 779 return cap_safe_nice(p); 780 } 781 782 /** 783 * cap_task_ioprio - Detemine if I/O priority change is permitted 784 * @p: The task to affect 785 * @ioprio: The I/O priority to set 786 * 787 * Detemine if the requested I/O priority change is permitted for the specified 788 * task, returning 0 if permission is granted, -ve if denied. 789 */ 790 int cap_task_setioprio(struct task_struct *p, int ioprio) 791 { 792 return cap_safe_nice(p); 793 } 794 795 /** 796 * cap_task_ioprio - Detemine if task priority change is permitted 797 * @p: The task to affect 798 * @nice: The nice value to set 799 * 800 * Detemine if the requested task priority change is permitted for the 801 * specified task, returning 0 if permission is granted, -ve if denied. 802 */ 803 int cap_task_setnice(struct task_struct *p, int nice) 804 { 805 return cap_safe_nice(p); 806 } 807 808 /* 809 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 810 * the current task's bounding set. Returns 0 on success, -ve on error. 811 */ 812 static long cap_prctl_drop(struct cred *new, unsigned long cap) 813 { 814 if (!capable(CAP_SETPCAP)) 815 return -EPERM; 816 if (!cap_valid(cap)) 817 return -EINVAL; 818 819 cap_lower(new->cap_bset, cap); 820 return 0; 821 } 822 823 #else 824 int cap_task_setscheduler (struct task_struct *p, int policy, 825 struct sched_param *lp) 826 { 827 return 0; 828 } 829 int cap_task_setioprio (struct task_struct *p, int ioprio) 830 { 831 return 0; 832 } 833 int cap_task_setnice (struct task_struct *p, int nice) 834 { 835 return 0; 836 } 837 #endif 838 839 /** 840 * cap_task_prctl - Implement process control functions for this security module 841 * @option: The process control function requested 842 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 843 * 844 * Allow process control functions (sys_prctl()) to alter capabilities; may 845 * also deny access to other functions not otherwise implemented here. 846 * 847 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 848 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 849 * modules will consider performing the function. 850 */ 851 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 852 unsigned long arg4, unsigned long arg5) 853 { 854 struct cred *new; 855 long error = 0; 856 857 new = prepare_creds(); 858 if (!new) 859 return -ENOMEM; 860 861 switch (option) { 862 case PR_CAPBSET_READ: 863 error = -EINVAL; 864 if (!cap_valid(arg2)) 865 goto error; 866 error = !!cap_raised(new->cap_bset, arg2); 867 goto no_change; 868 869 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 870 case PR_CAPBSET_DROP: 871 error = cap_prctl_drop(new, arg2); 872 if (error < 0) 873 goto error; 874 goto changed; 875 876 /* 877 * The next four prctl's remain to assist with transitioning a 878 * system from legacy UID=0 based privilege (when filesystem 879 * capabilities are not in use) to a system using filesystem 880 * capabilities only - as the POSIX.1e draft intended. 881 * 882 * Note: 883 * 884 * PR_SET_SECUREBITS = 885 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 886 * | issecure_mask(SECURE_NOROOT) 887 * | issecure_mask(SECURE_NOROOT_LOCKED) 888 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 889 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 890 * 891 * will ensure that the current process and all of its 892 * children will be locked into a pure 893 * capability-based-privilege environment. 894 */ 895 case PR_SET_SECUREBITS: 896 error = -EPERM; 897 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 898 & (new->securebits ^ arg2)) /*[1]*/ 899 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 900 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 901 || (cap_capable(current, current_cred(), CAP_SETPCAP, 902 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 903 /* 904 * [1] no changing of bits that are locked 905 * [2] no unlocking of locks 906 * [3] no setting of unsupported bits 907 * [4] doing anything requires privilege (go read about 908 * the "sendmail capabilities bug") 909 */ 910 ) 911 /* cannot change a locked bit */ 912 goto error; 913 new->securebits = arg2; 914 goto changed; 915 916 case PR_GET_SECUREBITS: 917 error = new->securebits; 918 goto no_change; 919 920 #endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ 921 922 case PR_GET_KEEPCAPS: 923 if (issecure(SECURE_KEEP_CAPS)) 924 error = 1; 925 goto no_change; 926 927 case PR_SET_KEEPCAPS: 928 error = -EINVAL; 929 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 930 goto error; 931 error = -EPERM; 932 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 933 goto error; 934 if (arg2) 935 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 936 else 937 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 938 goto changed; 939 940 default: 941 /* No functionality available - continue with default */ 942 error = -ENOSYS; 943 goto error; 944 } 945 946 /* Functionality provided */ 947 changed: 948 return commit_creds(new); 949 950 no_change: 951 error: 952 abort_creds(new); 953 return error; 954 } 955 956 /** 957 * cap_syslog - Determine whether syslog function is permitted 958 * @type: Function requested 959 * 960 * Determine whether the current process is permitted to use a particular 961 * syslog function, returning 0 if permission is granted, -ve if not. 962 */ 963 int cap_syslog(int type) 964 { 965 if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN)) 966 return -EPERM; 967 return 0; 968 } 969 970 /** 971 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 972 * @mm: The VM space in which the new mapping is to be made 973 * @pages: The size of the mapping 974 * 975 * Determine whether the allocation of a new virtual mapping by the current 976 * task is permitted, returning 0 if permission is granted, -ve if not. 977 */ 978 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 979 { 980 int cap_sys_admin = 0; 981 982 if (cap_capable(current, current_cred(), CAP_SYS_ADMIN, 983 SECURITY_CAP_NOAUDIT) == 0) 984 cap_sys_admin = 1; 985 return __vm_enough_memory(mm, pages, cap_sys_admin); 986 } 987 988 /* 989 * cap_file_mmap - check if able to map given addr 990 * @file: unused 991 * @reqprot: unused 992 * @prot: unused 993 * @flags: unused 994 * @addr: address attempting to be mapped 995 * @addr_only: unused 996 * 997 * If the process is attempting to map memory below mmap_min_addr they need 998 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 999 * capability security module. Returns 0 if this mapping should be allowed 1000 * -EPERM if not. 1001 */ 1002 int cap_file_mmap(struct file *file, unsigned long reqprot, 1003 unsigned long prot, unsigned long flags, 1004 unsigned long addr, unsigned long addr_only) 1005 { 1006 int ret = 0; 1007 1008 if (addr < dac_mmap_min_addr) { 1009 ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO, 1010 SECURITY_CAP_AUDIT); 1011 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 1012 if (ret == 0) 1013 current->flags |= PF_SUPERPRIV; 1014 } 1015 return ret; 1016 } 1017