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/lsm_hooks.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 */
  45static 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/**
  57 * cap_capable - Determine whether a task has a particular effective capability
  58 * @cred: The credentials to use
  59 * @ns:  The user namespace in which we need the capability
  60 * @cap: The capability to check for
  61 * @audit: Whether to write an audit message or not
  62 *
  63 * Determine whether the nominated task has the specified capability amongst
  64 * its effective set, returning 0 if it does, -ve if it does not.
  65 *
  66 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
  67 * and has_capability() functions.  That is, it has the reverse semantics:
  68 * cap_has_capability() returns 0 when a task has a capability, but the
  69 * kernel's capable() and has_capability() returns 1 for this case.
  70 */
  71int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
  72		int cap, int audit)
  73{
  74	struct user_namespace *ns = targ_ns;
  75
  76	/* See if cred has the capability in the target user namespace
  77	 * by examining the target user namespace and all of the target
  78	 * user namespace's parents.
  79	 */
  80	for (;;) {
  81		/* Do we have the necessary capabilities? */
  82		if (ns == cred->user_ns)
  83			return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
  84
  85		/* Have we tried all of the parent namespaces? */
  86		if (ns == &init_user_ns)
  87			return -EPERM;
  88
  89		/* 
  90		 * The owner of the user namespace in the parent of the
  91		 * user namespace has all caps.
  92		 */
  93		if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
  94			return 0;
  95
  96		/*
  97		 * If you have a capability in a parent user ns, then you have
  98		 * it over all children user namespaces as well.
  99		 */
 100		ns = ns->parent;
 101	}
 102
 103	/* We never get here */
 104}
 105
 106/**
 107 * cap_settime - Determine whether the current process may set the system clock
 108 * @ts: The time to set
 109 * @tz: The timezone to set
 110 *
 111 * Determine whether the current process may set the system clock and timezone
 112 * information, returning 0 if permission granted, -ve if denied.
 113 */
 114int cap_settime(const struct timespec *ts, const struct timezone *tz)
 115{
 116	if (!capable(CAP_SYS_TIME))
 117		return -EPERM;
 118	return 0;
 119}
 120
 121/**
 122 * cap_ptrace_access_check - Determine whether the current process may access
 123 *			   another
 124 * @child: The process to be accessed
 125 * @mode: The mode of attachment.
 126 *
 127 * If we are in the same or an ancestor user_ns and have all the target
 128 * task's capabilities, then ptrace access is allowed.
 129 * If we have the ptrace capability to the target user_ns, then ptrace
 130 * access is allowed.
 131 * Else denied.
 132 *
 133 * Determine whether a process may access another, returning 0 if permission
 134 * granted, -ve if denied.
 135 */
 136int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
 137{
 138	int ret = 0;
 139	const struct cred *cred, *child_cred;
 140	const kernel_cap_t *caller_caps;
 141
 142	rcu_read_lock();
 143	cred = current_cred();
 144	child_cred = __task_cred(child);
 145	if (mode & PTRACE_MODE_FSCREDS)
 146		caller_caps = &cred->cap_effective;
 147	else
 148		caller_caps = &cred->cap_permitted;
 149	if (cred->user_ns == child_cred->user_ns &&
 150	    cap_issubset(child_cred->cap_permitted, *caller_caps))
 151		goto out;
 152	if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
 153		goto out;
 154	ret = -EPERM;
 155out:
 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 */
 173int 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;
 187out:
 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 */
 202int 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 */
 221static 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 */
 245int 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
 276	/*
 277	 * Mask off ambient bits that are no longer both permitted and
 278	 * inheritable.
 279	 */
 280	new->cap_ambient = cap_intersect(new->cap_ambient,
 281					 cap_intersect(*permitted,
 282						       *inheritable));
 283	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 284		return -EINVAL;
 285	return 0;
 286}
 287
 288/*
 289 * Clear proposed capability sets for execve().
 290 */
 291static inline void bprm_clear_caps(struct linux_binprm *bprm)
 292{
 293	cap_clear(bprm->cred->cap_permitted);
 294	bprm->cap_effective = false;
 295}
 296
 297/**
 298 * cap_inode_need_killpriv - Determine if inode change affects privileges
 299 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
 300 *
 301 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
 302 * affects the security markings on that inode, and if it is, should
 303 * inode_killpriv() be invoked or the change rejected?
 304 *
 305 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
 306 * -ve to deny the change.
 307 */
 308int cap_inode_need_killpriv(struct dentry *dentry)
 309{
 310	struct inode *inode = d_backing_inode(dentry);
 311	int error;
 312
 313	if (!inode->i_op->getxattr)
 314	       return 0;
 315
 316	error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
 317	if (error <= 0)
 318		return 0;
 319	return 1;
 320}
 321
 322/**
 323 * cap_inode_killpriv - Erase the security markings on an inode
 324 * @dentry: The inode/dentry to alter
 325 *
 326 * Erase the privilege-enhancing security markings on an inode.
 327 *
 328 * Returns 0 if successful, -ve on error.
 329 */
 330int cap_inode_killpriv(struct dentry *dentry)
 331{
 332	struct inode *inode = d_backing_inode(dentry);
 333
 334	if (!inode->i_op->removexattr)
 335	       return 0;
 336
 337	return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
 
 
 
 338}
 339
 340/*
 341 * Calculate the new process capability sets from the capability sets attached
 342 * to a file.
 343 */
 344static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 345					  struct linux_binprm *bprm,
 346					  bool *effective,
 347					  bool *has_cap)
 348{
 349	struct cred *new = bprm->cred;
 350	unsigned i;
 351	int ret = 0;
 352
 353	if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
 354		*effective = true;
 355
 356	if (caps->magic_etc & VFS_CAP_REVISION_MASK)
 357		*has_cap = true;
 358
 359	CAP_FOR_EACH_U32(i) {
 360		__u32 permitted = caps->permitted.cap[i];
 361		__u32 inheritable = caps->inheritable.cap[i];
 362
 363		/*
 364		 * pP' = (X & fP) | (pI & fI)
 365		 * The addition of pA' is handled later.
 366		 */
 367		new->cap_permitted.cap[i] =
 368			(new->cap_bset.cap[i] & permitted) |
 369			(new->cap_inheritable.cap[i] & inheritable);
 370
 371		if (permitted & ~new->cap_permitted.cap[i])
 372			/* insufficient to execute correctly */
 373			ret = -EPERM;
 374	}
 375
 376	/*
 377	 * For legacy apps, with no internal support for recognizing they
 378	 * do not have enough capabilities, we return an error if they are
 379	 * missing some "forced" (aka file-permitted) capabilities.
 380	 */
 381	return *effective ? ret : 0;
 382}
 383
 384/*
 385 * Extract the on-exec-apply capability sets for an executable file.
 386 */
 387int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
 388{
 389	struct inode *inode = d_backing_inode(dentry);
 390	__u32 magic_etc;
 391	unsigned tocopy, i;
 392	int size;
 393	struct vfs_cap_data caps;
 394
 395	memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
 396
 397	if (!inode || !inode->i_op->getxattr)
 398		return -ENODATA;
 399
 400	size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
 401				   XATTR_CAPS_SZ);
 402	if (size == -ENODATA || size == -EOPNOTSUPP)
 403		/* no data, that's ok */
 404		return -ENODATA;
 405	if (size < 0)
 406		return size;
 407
 408	if (size < sizeof(magic_etc))
 409		return -EINVAL;
 410
 411	cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
 412
 413	switch (magic_etc & VFS_CAP_REVISION_MASK) {
 414	case VFS_CAP_REVISION_1:
 415		if (size != XATTR_CAPS_SZ_1)
 416			return -EINVAL;
 417		tocopy = VFS_CAP_U32_1;
 418		break;
 419	case VFS_CAP_REVISION_2:
 420		if (size != XATTR_CAPS_SZ_2)
 421			return -EINVAL;
 422		tocopy = VFS_CAP_U32_2;
 423		break;
 424	default:
 425		return -EINVAL;
 426	}
 427
 428	CAP_FOR_EACH_U32(i) {
 429		if (i >= tocopy)
 430			break;
 431		cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
 432		cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
 433	}
 434
 435	cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 436	cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 437
 438	return 0;
 439}
 440
 441/*
 442 * Attempt to get the on-exec apply capability sets for an executable file from
 443 * its xattrs and, if present, apply them to the proposed credentials being
 444 * constructed by execve().
 445 */
 446static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
 447{
 448	int rc = 0;
 449	struct cpu_vfs_cap_data vcaps;
 450
 451	bprm_clear_caps(bprm);
 452
 453	if (!file_caps_enabled)
 454		return 0;
 455
 456	if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
 
 
 
 
 
 
 
 
 457		return 0;
 458
 459	rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);
 460	if (rc < 0) {
 461		if (rc == -EINVAL)
 462			printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
 463				__func__, rc, bprm->filename);
 464		else if (rc == -ENODATA)
 465			rc = 0;
 466		goto out;
 467	}
 468
 469	rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
 470	if (rc == -EINVAL)
 471		printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
 472		       __func__, rc, bprm->filename);
 473
 474out:
 475	if (rc)
 476		bprm_clear_caps(bprm);
 477
 478	return rc;
 479}
 480
 481/**
 482 * cap_bprm_set_creds - Set up the proposed credentials for execve().
 483 * @bprm: The execution parameters, including the proposed creds
 484 *
 485 * Set up the proposed credentials for a new execution context being
 486 * constructed by execve().  The proposed creds in @bprm->cred is altered,
 487 * which won't take effect immediately.  Returns 0 if successful, -ve on error.
 488 */
 489int cap_bprm_set_creds(struct linux_binprm *bprm)
 490{
 491	const struct cred *old = current_cred();
 492	struct cred *new = bprm->cred;
 493	bool effective, has_cap = false, is_setid;
 494	int ret;
 495	kuid_t root_uid;
 496
 497	if (WARN_ON(!cap_ambient_invariant_ok(old)))
 498		return -EPERM;
 499
 500	effective = false;
 501	ret = get_file_caps(bprm, &effective, &has_cap);
 502	if (ret < 0)
 503		return ret;
 504
 505	root_uid = make_kuid(new->user_ns, 0);
 506
 507	if (!issecure(SECURE_NOROOT)) {
 508		/*
 509		 * If the legacy file capability is set, then don't set privs
 510		 * for a setuid root binary run by a non-root user.  Do set it
 511		 * for a root user just to cause least surprise to an admin.
 512		 */
 513		if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
 514			warn_setuid_and_fcaps_mixed(bprm->filename);
 515			goto skip;
 516		}
 517		/*
 518		 * To support inheritance of root-permissions and suid-root
 519		 * executables under compatibility mode, we override the
 520		 * capability sets for the file.
 521		 *
 522		 * If only the real uid is 0, we do not set the effective bit.
 523		 */
 524		if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
 525			/* pP' = (cap_bset & ~0) | (pI & ~0) */
 526			new->cap_permitted = cap_combine(old->cap_bset,
 527							 old->cap_inheritable);
 528		}
 529		if (uid_eq(new->euid, root_uid))
 530			effective = true;
 531	}
 532skip:
 533
 534	/* if we have fs caps, clear dangerous personality flags */
 535	if (!cap_issubset(new->cap_permitted, old->cap_permitted))
 536		bprm->per_clear |= PER_CLEAR_ON_SETID;
 537
 538
 539	/* Don't let someone trace a set[ug]id/setpcap binary with the revised
 540	 * credentials unless they have the appropriate permit.
 541	 *
 542	 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
 543	 */
 544	is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
 545
 546	if ((is_setid ||
 547	     !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
 548	    bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
 549		/* downgrade; they get no more than they had, and maybe less */
 550		if (!capable(CAP_SETUID) ||
 551		    (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
 552			new->euid = new->uid;
 553			new->egid = new->gid;
 554		}
 555		new->cap_permitted = cap_intersect(new->cap_permitted,
 556						   old->cap_permitted);
 557	}
 558
 559	new->suid = new->fsuid = new->euid;
 560	new->sgid = new->fsgid = new->egid;
 561
 562	/* File caps or setid cancels ambient. */
 563	if (has_cap || is_setid)
 564		cap_clear(new->cap_ambient);
 565
 566	/*
 567	 * Now that we've computed pA', update pP' to give:
 568	 *   pP' = (X & fP) | (pI & fI) | pA'
 569	 */
 570	new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
 571
 572	/*
 573	 * Set pE' = (fE ? pP' : pA').  Because pA' is zero if fE is set,
 574	 * this is the same as pE' = (fE ? pP' : 0) | pA'.
 575	 */
 576	if (effective)
 577		new->cap_effective = new->cap_permitted;
 578	else
 579		new->cap_effective = new->cap_ambient;
 580
 581	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 582		return -EPERM;
 583
 584	bprm->cap_effective = effective;
 585
 586	/*
 587	 * Audit candidate if current->cap_effective is set
 588	 *
 589	 * We do not bother to audit if 3 things are true:
 590	 *   1) cap_effective has all caps
 591	 *   2) we are root
 592	 *   3) root is supposed to have all caps (SECURE_NOROOT)
 593	 * Since this is just a normal root execing a process.
 594	 *
 595	 * Number 1 above might fail if you don't have a full bset, but I think
 596	 * that is interesting information to audit.
 597	 */
 598	if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
 599		if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
 600		    !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
 601		    issecure(SECURE_NOROOT)) {
 602			ret = audit_log_bprm_fcaps(bprm, new, old);
 603			if (ret < 0)
 604				return ret;
 605		}
 606	}
 607
 608	new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 609
 610	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 611		return -EPERM;
 612
 613	return 0;
 614}
 615
 616/**
 617 * cap_bprm_secureexec - Determine whether a secure execution is required
 618 * @bprm: The execution parameters
 619 *
 620 * Determine whether a secure execution is required, return 1 if it is, and 0
 621 * if it is not.
 622 *
 623 * The credentials have been committed by this point, and so are no longer
 624 * available through @bprm->cred.
 625 */
 626int cap_bprm_secureexec(struct linux_binprm *bprm)
 627{
 628	const struct cred *cred = current_cred();
 629	kuid_t root_uid = make_kuid(cred->user_ns, 0);
 630
 631	if (!uid_eq(cred->uid, root_uid)) {
 632		if (bprm->cap_effective)
 633			return 1;
 634		if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))
 635			return 1;
 636	}
 637
 638	return (!uid_eq(cred->euid, cred->uid) ||
 639		!gid_eq(cred->egid, cred->gid));
 640}
 641
 642/**
 643 * cap_inode_setxattr - Determine whether an xattr may be altered
 644 * @dentry: The inode/dentry being altered
 645 * @name: The name of the xattr to be changed
 646 * @value: The value that the xattr will be changed to
 647 * @size: The size of value
 648 * @flags: The replacement flag
 649 *
 650 * Determine whether an xattr may be altered or set on an inode, returning 0 if
 651 * permission is granted, -ve if denied.
 652 *
 653 * This is used to make sure security xattrs don't get updated or set by those
 654 * who aren't privileged to do so.
 655 */
 656int cap_inode_setxattr(struct dentry *dentry, const char *name,
 657		       const void *value, size_t size, int flags)
 658{
 659	if (!strcmp(name, XATTR_NAME_CAPS)) {
 660		if (!capable(CAP_SETFCAP))
 661			return -EPERM;
 662		return 0;
 663	}
 664
 665	if (!strncmp(name, XATTR_SECURITY_PREFIX,
 666		     sizeof(XATTR_SECURITY_PREFIX) - 1) &&
 667	    !capable(CAP_SYS_ADMIN))
 668		return -EPERM;
 669	return 0;
 670}
 671
 672/**
 673 * cap_inode_removexattr - Determine whether an xattr may be removed
 674 * @dentry: The inode/dentry being altered
 675 * @name: The name of the xattr to be changed
 676 *
 677 * Determine whether an xattr may be removed from an inode, returning 0 if
 678 * permission is granted, -ve if denied.
 679 *
 680 * This is used to make sure security xattrs don't get removed by those who
 681 * aren't privileged to remove them.
 682 */
 683int cap_inode_removexattr(struct dentry *dentry, const char *name)
 684{
 685	if (!strcmp(name, XATTR_NAME_CAPS)) {
 686		if (!capable(CAP_SETFCAP))
 687			return -EPERM;
 688		return 0;
 689	}
 690
 691	if (!strncmp(name, XATTR_SECURITY_PREFIX,
 692		     sizeof(XATTR_SECURITY_PREFIX) - 1) &&
 693	    !capable(CAP_SYS_ADMIN))
 694		return -EPERM;
 695	return 0;
 696}
 697
 698/*
 699 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
 700 * a process after a call to setuid, setreuid, or setresuid.
 701 *
 702 *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
 703 *  {r,e,s}uid != 0, the permitted and effective capabilities are
 704 *  cleared.
 705 *
 706 *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
 707 *  capabilities of the process are cleared.
 708 *
 709 *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
 710 *  capabilities are set to the permitted capabilities.
 711 *
 712 *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
 713 *  never happen.
 714 *
 715 *  -astor
 716 *
 717 * cevans - New behaviour, Oct '99
 718 * A process may, via prctl(), elect to keep its capabilities when it
 719 * calls setuid() and switches away from uid==0. Both permitted and
 720 * effective sets will be retained.
 721 * Without this change, it was impossible for a daemon to drop only some
 722 * of its privilege. The call to setuid(!=0) would drop all privileges!
 723 * Keeping uid 0 is not an option because uid 0 owns too many vital
 724 * files..
 725 * Thanks to Olaf Kirch and Peter Benie for spotting this.
 726 */
 727static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
 728{
 729	kuid_t root_uid = make_kuid(old->user_ns, 0);
 730
 731	if ((uid_eq(old->uid, root_uid) ||
 732	     uid_eq(old->euid, root_uid) ||
 733	     uid_eq(old->suid, root_uid)) &&
 734	    (!uid_eq(new->uid, root_uid) &&
 735	     !uid_eq(new->euid, root_uid) &&
 736	     !uid_eq(new->suid, root_uid))) {
 737		if (!issecure(SECURE_KEEP_CAPS)) {
 738			cap_clear(new->cap_permitted);
 739			cap_clear(new->cap_effective);
 740		}
 741
 742		/*
 743		 * Pre-ambient programs expect setresuid to nonroot followed
 744		 * by exec to drop capabilities.  We should make sure that
 745		 * this remains the case.
 746		 */
 747		cap_clear(new->cap_ambient);
 748	}
 749	if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
 750		cap_clear(new->cap_effective);
 751	if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
 752		new->cap_effective = new->cap_permitted;
 753}
 754
 755/**
 756 * cap_task_fix_setuid - Fix up the results of setuid() call
 757 * @new: The proposed credentials
 758 * @old: The current task's current credentials
 759 * @flags: Indications of what has changed
 760 *
 761 * Fix up the results of setuid() call before the credential changes are
 762 * actually applied, returning 0 to grant the changes, -ve to deny them.
 763 */
 764int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
 765{
 766	switch (flags) {
 767	case LSM_SETID_RE:
 768	case LSM_SETID_ID:
 769	case LSM_SETID_RES:
 770		/* juggle the capabilities to follow [RES]UID changes unless
 771		 * otherwise suppressed */
 772		if (!issecure(SECURE_NO_SETUID_FIXUP))
 773			cap_emulate_setxuid(new, old);
 774		break;
 775
 776	case LSM_SETID_FS:
 777		/* juggle the capabilties to follow FSUID changes, unless
 778		 * otherwise suppressed
 779		 *
 780		 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
 781		 *          if not, we might be a bit too harsh here.
 782		 */
 783		if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 784			kuid_t root_uid = make_kuid(old->user_ns, 0);
 785			if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
 786				new->cap_effective =
 787					cap_drop_fs_set(new->cap_effective);
 788
 789			if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
 790				new->cap_effective =
 791					cap_raise_fs_set(new->cap_effective,
 792							 new->cap_permitted);
 793		}
 794		break;
 795
 796	default:
 797		return -EINVAL;
 798	}
 799
 800	return 0;
 801}
 802
 803/*
 804 * Rationale: code calling task_setscheduler, task_setioprio, and
 805 * task_setnice, assumes that
 806 *   . if capable(cap_sys_nice), then those actions should be allowed
 807 *   . if not capable(cap_sys_nice), but acting on your own processes,
 808 *   	then those actions should be allowed
 809 * This is insufficient now since you can call code without suid, but
 810 * yet with increased caps.
 811 * So we check for increased caps on the target process.
 812 */
 813static int cap_safe_nice(struct task_struct *p)
 814{
 815	int is_subset, ret = 0;
 816
 817	rcu_read_lock();
 818	is_subset = cap_issubset(__task_cred(p)->cap_permitted,
 819				 current_cred()->cap_permitted);
 820	if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
 821		ret = -EPERM;
 822	rcu_read_unlock();
 823
 824	return ret;
 825}
 826
 827/**
 828 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
 829 * @p: The task to affect
 830 *
 831 * Detemine if the requested scheduler policy change is permitted for the
 832 * specified task, returning 0 if permission is granted, -ve if denied.
 833 */
 834int cap_task_setscheduler(struct task_struct *p)
 835{
 836	return cap_safe_nice(p);
 837}
 838
 839/**
 840 * cap_task_ioprio - Detemine if I/O priority change is permitted
 841 * @p: The task to affect
 842 * @ioprio: The I/O priority to set
 843 *
 844 * Detemine if the requested I/O priority change is permitted for the specified
 845 * task, returning 0 if permission is granted, -ve if denied.
 846 */
 847int cap_task_setioprio(struct task_struct *p, int ioprio)
 848{
 849	return cap_safe_nice(p);
 850}
 851
 852/**
 853 * cap_task_ioprio - Detemine if task priority change is permitted
 854 * @p: The task to affect
 855 * @nice: The nice value to set
 856 *
 857 * Detemine if the requested task priority change is permitted for the
 858 * specified task, returning 0 if permission is granted, -ve if denied.
 859 */
 860int cap_task_setnice(struct task_struct *p, int nice)
 861{
 862	return cap_safe_nice(p);
 863}
 864
 865/*
 866 * Implement PR_CAPBSET_DROP.  Attempt to remove the specified capability from
 867 * the current task's bounding set.  Returns 0 on success, -ve on error.
 868 */
 869static int cap_prctl_drop(unsigned long cap)
 870{
 871	struct cred *new;
 872
 873	if (!ns_capable(current_user_ns(), CAP_SETPCAP))
 874		return -EPERM;
 875	if (!cap_valid(cap))
 876		return -EINVAL;
 877
 878	new = prepare_creds();
 879	if (!new)
 880		return -ENOMEM;
 881	cap_lower(new->cap_bset, cap);
 882	return commit_creds(new);
 883}
 884
 885/**
 886 * cap_task_prctl - Implement process control functions for this security module
 887 * @option: The process control function requested
 888 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
 889 *
 890 * Allow process control functions (sys_prctl()) to alter capabilities; may
 891 * also deny access to other functions not otherwise implemented here.
 892 *
 893 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
 894 * here, other -ve on error.  If -ENOSYS is returned, sys_prctl() and other LSM
 895 * modules will consider performing the function.
 896 */
 897int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 898		   unsigned long arg4, unsigned long arg5)
 899{
 900	const struct cred *old = current_cred();
 901	struct cred *new;
 902
 903	switch (option) {
 904	case PR_CAPBSET_READ:
 905		if (!cap_valid(arg2))
 906			return -EINVAL;
 907		return !!cap_raised(old->cap_bset, arg2);
 908
 909	case PR_CAPBSET_DROP:
 910		return cap_prctl_drop(arg2);
 911
 912	/*
 913	 * The next four prctl's remain to assist with transitioning a
 914	 * system from legacy UID=0 based privilege (when filesystem
 915	 * capabilities are not in use) to a system using filesystem
 916	 * capabilities only - as the POSIX.1e draft intended.
 917	 *
 918	 * Note:
 919	 *
 920	 *  PR_SET_SECUREBITS =
 921	 *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
 922	 *    | issecure_mask(SECURE_NOROOT)
 923	 *    | issecure_mask(SECURE_NOROOT_LOCKED)
 924	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
 925	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
 926	 *
 927	 * will ensure that the current process and all of its
 928	 * children will be locked into a pure
 929	 * capability-based-privilege environment.
 930	 */
 931	case PR_SET_SECUREBITS:
 932		if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
 933		     & (old->securebits ^ arg2))			/*[1]*/
 934		    || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))	/*[2]*/
 935		    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))	/*[3]*/
 936		    || (cap_capable(current_cred(),
 937				    current_cred()->user_ns, CAP_SETPCAP,
 938				    SECURITY_CAP_AUDIT) != 0)		/*[4]*/
 939			/*
 940			 * [1] no changing of bits that are locked
 941			 * [2] no unlocking of locks
 942			 * [3] no setting of unsupported bits
 943			 * [4] doing anything requires privilege (go read about
 944			 *     the "sendmail capabilities bug")
 945			 */
 946		    )
 947			/* cannot change a locked bit */
 948			return -EPERM;
 949
 950		new = prepare_creds();
 951		if (!new)
 952			return -ENOMEM;
 953		new->securebits = arg2;
 954		return commit_creds(new);
 955
 956	case PR_GET_SECUREBITS:
 957		return old->securebits;
 958
 959	case PR_GET_KEEPCAPS:
 960		return !!issecure(SECURE_KEEP_CAPS);
 961
 962	case PR_SET_KEEPCAPS:
 963		if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
 964			return -EINVAL;
 965		if (issecure(SECURE_KEEP_CAPS_LOCKED))
 966			return -EPERM;
 967
 968		new = prepare_creds();
 969		if (!new)
 970			return -ENOMEM;
 971		if (arg2)
 972			new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
 973		else
 974			new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 975		return commit_creds(new);
 976
 977	case PR_CAP_AMBIENT:
 978		if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
 979			if (arg3 | arg4 | arg5)
 980				return -EINVAL;
 981
 982			new = prepare_creds();
 983			if (!new)
 984				return -ENOMEM;
 985			cap_clear(new->cap_ambient);
 986			return commit_creds(new);
 987		}
 988
 989		if (((!cap_valid(arg3)) | arg4 | arg5))
 990			return -EINVAL;
 991
 992		if (arg2 == PR_CAP_AMBIENT_IS_SET) {
 993			return !!cap_raised(current_cred()->cap_ambient, arg3);
 994		} else if (arg2 != PR_CAP_AMBIENT_RAISE &&
 995			   arg2 != PR_CAP_AMBIENT_LOWER) {
 996			return -EINVAL;
 997		} else {
 998			if (arg2 == PR_CAP_AMBIENT_RAISE &&
 999			    (!cap_raised(current_cred()->cap_permitted, arg3) ||
1000			     !cap_raised(current_cred()->cap_inheritable,
1001					 arg3) ||
1002			     issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1003				return -EPERM;
1004
1005			new = prepare_creds();
1006			if (!new)
1007				return -ENOMEM;
1008			if (arg2 == PR_CAP_AMBIENT_RAISE)
1009				cap_raise(new->cap_ambient, arg3);
1010			else
1011				cap_lower(new->cap_ambient, arg3);
1012			return commit_creds(new);
1013		}
1014
1015	default:
1016		/* No functionality available - continue with default */
1017		return -ENOSYS;
1018	}
1019}
1020
1021/**
1022 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1023 * @mm: The VM space in which the new mapping is to be made
1024 * @pages: The size of the mapping
1025 *
1026 * Determine whether the allocation of a new virtual mapping by the current
1027 * task is permitted, returning 1 if permission is granted, 0 if not.
1028 */
1029int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1030{
1031	int cap_sys_admin = 0;
1032
1033	if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
1034			SECURITY_CAP_NOAUDIT) == 0)
1035		cap_sys_admin = 1;
1036	return cap_sys_admin;
1037}
1038
1039/*
1040 * cap_mmap_addr - check if able to map given addr
1041 * @addr: address attempting to be mapped
1042 *
1043 * If the process is attempting to map memory below dac_mmap_min_addr they need
1044 * CAP_SYS_RAWIO.  The other parameters to this function are unused by the
1045 * capability security module.  Returns 0 if this mapping should be allowed
1046 * -EPERM if not.
1047 */
1048int cap_mmap_addr(unsigned long addr)
1049{
1050	int ret = 0;
1051
1052	if (addr < dac_mmap_min_addr) {
1053		ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1054				  SECURITY_CAP_AUDIT);
1055		/* set PF_SUPERPRIV if it turns out we allow the low mmap */
1056		if (ret == 0)
1057			current->flags |= PF_SUPERPRIV;
1058	}
1059	return ret;
1060}
1061
1062int cap_mmap_file(struct file *file, unsigned long reqprot,
1063		  unsigned long prot, unsigned long flags)
1064{
1065	return 0;
1066}
1067
1068#ifdef CONFIG_SECURITY
1069
1070struct security_hook_list capability_hooks[] = {
1071	LSM_HOOK_INIT(capable, cap_capable),
1072	LSM_HOOK_INIT(settime, cap_settime),
1073	LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1074	LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1075	LSM_HOOK_INIT(capget, cap_capget),
1076	LSM_HOOK_INIT(capset, cap_capset),
1077	LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
1078	LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec),
1079	LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1080	LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1081	LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1082	LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1083	LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1084	LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1085	LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1086	LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1087	LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1088	LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1089};
1090
1091void __init capability_add_hooks(void)
1092{
1093	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
1094}
1095
1096#endif /* CONFIG_SECURITY */