/* Common capabilities, needed by capability.o.

   *
   *	This program is free software; you can redistribute it and/or modify
   *	it under the terms of the GNU General Public License as published by
   *	the Free Software Foundation; either version 2 of the License, or
   *	(at your option) any later version.
   *
   */

  #include <linux/capability.h>

  #include <linux/audit.h>

  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/kernel.h>

  #include <linux/lsm_hooks.h>

  #include <linux/file.h>
  #include <linux/mm.h>
  #include <linux/mman.h>
  #include <linux/pagemap.h>
  #include <linux/swap.h>

  #include <linux/skbuff.h>
  #include <linux/netlink.h>
  #include <linux/ptrace.h>
  #include <linux/xattr.h>
  #include <linux/hugetlb.h>

  #include <linux/mount.h>

  #include <linux/sched.h>

  #include <linux/prctl.h>
  #include <linux/securebits.h>

  #include <linux/user_namespace.h>

  #include <linux/binfmts.h>

  #include <linux/personality.h>

  /*
   * If a non-root user executes a setuid-root binary in
   * !secure(SECURE_NOROOT) mode, then we raise capabilities.
   * However if fE is also set, then the intent is for only
   * the file capabilities to be applied, and the setuid-root
   * bit is left on either to change the uid (plausible) or
   * to get full privilege on a kernel without file capabilities
   * support.  So in that case we do not raise capabilities.
   *
   * Warn if that happens, once per boot.
   */

  static void warn_setuid_and_fcaps_mixed(const char *fname)

  {
  	static int warned;
  	if (!warned) {
  		printk(KERN_INFO "warning: `%s' has both setuid-root and"
  			" effective capabilities. Therefore not raising all"
  			" capabilities.
  ", fname);
  		warned = 1;
  	}
  }

  /**
   * cap_capable - Determine whether a task has a particular effective capability

   * @cred: The credentials to use

   * @ns:  The user namespace in which we need the capability

   * @cap: The capability to check for
   * @audit: Whether to write an audit message or not
   *
   * Determine whether the nominated task has the specified capability amongst
   * its effective set, returning 0 if it does, -ve if it does not.
   *

   * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
   * and has_capability() functions.  That is, it has the reverse semantics:
   * cap_has_capability() returns 0 when a task has a capability, but the
   * kernel's capable() and has_capability() returns 1 for this case.

   */

  int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
  		int cap, int audit)

  {

  	struct user_namespace *ns = targ_ns;

  	/* See if cred has the capability in the target user namespace
  	 * by examining the target user namespace and all of the target
  	 * user namespace's parents.
  	 */
  	for (;;) {

  		/* Do we have the necessary capabilities? */

  		if (ns == cred->user_ns)

  			return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
  
  		/* Have we tried all of the parent namespaces? */

  		if (ns == &init_user_ns)

  			return -EPERM;

  		/* 
  		 * The owner of the user namespace in the parent of the
  		 * user namespace has all caps.
  		 */
  		if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
  			return 0;

  		/*

  		 * If you have a capability in a parent user ns, then you have

  		 * it over all children user namespaces as well.
  		 */

  		ns = ns->parent;

  	}
  
  	/* We never get here */

  }

  /**
   * cap_settime - Determine whether the current process may set the system clock
   * @ts: The time to set
   * @tz: The timezone to set
   *
   * Determine whether the current process may set the system clock and timezone
   * information, returning 0 if permission granted, -ve if denied.
   */

  int cap_settime(const struct timespec64 *ts, const struct timezone *tz)

  {
  	if (!capable(CAP_SYS_TIME))
  		return -EPERM;
  	return 0;
  }

  /**

   * cap_ptrace_access_check - Determine whether the current process may access

   *			   another
   * @child: The process to be accessed
   * @mode: The mode of attachment.
   *

   * If we are in the same or an ancestor user_ns and have all the target
   * task's capabilities, then ptrace access is allowed.
   * If we have the ptrace capability to the target user_ns, then ptrace
   * access is allowed.
   * Else denied.
   *

   * Determine whether a process may access another, returning 0 if permission
   * granted, -ve if denied.
   */

  int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)

  {

  	int ret = 0;

  	const struct cred *cred, *child_cred;

  	const kernel_cap_t *caller_caps;

  
  	rcu_read_lock();

  	cred = current_cred();
  	child_cred = __task_cred(child);

  	if (mode & PTRACE_MODE_FSCREDS)
  		caller_caps = &cred->cap_effective;
  	else
  		caller_caps = &cred->cap_permitted;

  	if (cred->user_ns == child_cred->user_ns &&

  	    cap_issubset(child_cred->cap_permitted, *caller_caps))

  		goto out;

  	if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))

  		goto out;
  	ret = -EPERM;
  out:

  	rcu_read_unlock();
  	return ret;

  }

  /**
   * cap_ptrace_traceme - Determine whether another process may trace the current
   * @parent: The task proposed to be the tracer
   *

   * If parent is in the same or an ancestor user_ns and has all current's
   * capabilities, then ptrace access is allowed.
   * If parent has the ptrace capability to current's user_ns, then ptrace
   * access is allowed.
   * Else denied.
   *

   * Determine whether the nominated task is permitted to trace the current
   * process, returning 0 if permission is granted, -ve if denied.
   */

  int cap_ptrace_traceme(struct task_struct *parent)
  {

  	int ret = 0;

  	const struct cred *cred, *child_cred;

  
  	rcu_read_lock();

  	cred = __task_cred(parent);
  	child_cred = current_cred();

  	if (cred->user_ns == child_cred->user_ns &&

  	    cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
  		goto out;

  	if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))

  		goto out;
  	ret = -EPERM;
  out:

  	rcu_read_unlock();
  	return ret;

  }

  /**
   * cap_capget - Retrieve a task's capability sets
   * @target: The task from which to retrieve the capability sets
   * @effective: The place to record the effective set
   * @inheritable: The place to record the inheritable set
   * @permitted: The place to record the permitted set
   *
   * This function retrieves the capabilities of the nominated task and returns
   * them to the caller.
   */
  int cap_capget(struct task_struct *target, kernel_cap_t *effective,
  	       kernel_cap_t *inheritable, kernel_cap_t *permitted)

  {

  	const struct cred *cred;

  	/* Derived from kernel/capability.c:sys_capget. */

  	rcu_read_lock();
  	cred = __task_cred(target);

  	*effective   = cred->cap_effective;
  	*inheritable = cred->cap_inheritable;
  	*permitted   = cred->cap_permitted;

  	rcu_read_unlock();

  	return 0;
  }

  /*
   * Determine whether the inheritable capabilities are limited to the old
   * permitted set.  Returns 1 if they are limited, 0 if they are not.
   */

  static inline int cap_inh_is_capped(void)
  {

  	/* they are so limited unless the current task has the CAP_SETPCAP
  	 * capability
  	 */

  	if (cap_capable(current_cred(), current_cred()->user_ns,

  			CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)

  		return 0;

  	return 1;

  }

  /**
   * cap_capset - Validate and apply proposed changes to current's capabilities
   * @new: The proposed new credentials; alterations should be made here
   * @old: The current task's current credentials
   * @effective: A pointer to the proposed new effective capabilities set
   * @inheritable: A pointer to the proposed new inheritable capabilities set
   * @permitted: A pointer to the proposed new permitted capabilities set
   *
   * This function validates and applies a proposed mass change to the current
   * process's capability sets.  The changes are made to the proposed new
   * credentials, and assuming no error, will be committed by the caller of LSM.
   */

  int cap_capset(struct cred *new,
  	       const struct cred *old,
  	       const kernel_cap_t *effective,
  	       const kernel_cap_t *inheritable,
  	       const kernel_cap_t *permitted)

  {

  	if (cap_inh_is_capped() &&
  	    !cap_issubset(*inheritable,
  			  cap_combine(old->cap_inheritable,
  				      old->cap_permitted)))

  		/* incapable of using this inheritable set */

  		return -EPERM;

  	if (!cap_issubset(*inheritable,

  			  cap_combine(old->cap_inheritable,
  				      old->cap_bset)))

  		/* no new pI capabilities outside bounding set */
  		return -EPERM;

  
  	/* verify restrictions on target's new Permitted set */

  	if (!cap_issubset(*permitted, old->cap_permitted))

  		return -EPERM;

  
  	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */

  	if (!cap_issubset(*effective, *permitted))

  		return -EPERM;

  	new->cap_effective   = *effective;
  	new->cap_inheritable = *inheritable;
  	new->cap_permitted   = *permitted;

  
  	/*
  	 * Mask off ambient bits that are no longer both permitted and
  	 * inheritable.
  	 */
  	new->cap_ambient = cap_intersect(new->cap_ambient,
  					 cap_intersect(*permitted,
  						       *inheritable));
  	if (WARN_ON(!cap_ambient_invariant_ok(new)))
  		return -EINVAL;

  	return 0;
  }

  /*
   * Clear proposed capability sets for execve().
   */

  static inline void bprm_clear_caps(struct linux_binprm *bprm)
  {

  	cap_clear(bprm->cred->cap_permitted);

  	bprm->cap_effective = false;
  }

  /**
   * cap_inode_need_killpriv - Determine if inode change affects privileges
   * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
   *
   * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
   * affects the security markings on that inode, and if it is, should
   * inode_killpriv() be invoked or the change rejected?
   *
   * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
   * -ve to deny the change.
   */

  int cap_inode_need_killpriv(struct dentry *dentry)
  {

  	struct inode *inode = d_backing_inode(dentry);

  	int error;

  	error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
  	return error > 0;

  }

  /**
   * cap_inode_killpriv - Erase the security markings on an inode
   * @dentry: The inode/dentry to alter
   *
   * Erase the privilege-enhancing security markings on an inode.
   *
   * Returns 0 if successful, -ve on error.
   */

  int cap_inode_killpriv(struct dentry *dentry)
  {

  	int error;

  	error = __vfs_removexattr(dentry, XATTR_NAME_CAPS);
  	if (error == -EOPNOTSUPP)
  		error = 0;
  	return error;

  }

  /*
   * Calculate the new process capability sets from the capability sets attached
   * to a file.
   */

  static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,

  					  struct linux_binprm *bprm,

  					  bool *effective,
  					  bool *has_cap)

  {

  	struct cred *new = bprm->cred;

  	unsigned i;
  	int ret = 0;
  
  	if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)

  		*effective = true;

  	if (caps->magic_etc & VFS_CAP_REVISION_MASK)
  		*has_cap = true;

  	CAP_FOR_EACH_U32(i) {
  		__u32 permitted = caps->permitted.cap[i];
  		__u32 inheritable = caps->inheritable.cap[i];
  
  		/*
  		 * pP' = (X & fP) | (pI & fI)

  		 * The addition of pA' is handled later.

  		 */

  		new->cap_permitted.cap[i] =
  			(new->cap_bset.cap[i] & permitted) |
  			(new->cap_inheritable.cap[i] & inheritable);

  		if (permitted & ~new->cap_permitted.cap[i])
  			/* insufficient to execute correctly */

  			ret = -EPERM;

  	}
  
  	/*
  	 * For legacy apps, with no internal support for recognizing they
  	 * do not have enough capabilities, we return an error if they are
  	 * missing some "forced" (aka file-permitted) capabilities.
  	 */

  	return *effective ? ret : 0;

  }

  /*
   * Extract the on-exec-apply capability sets for an executable file.
   */

  int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
  {

  	struct inode *inode = d_backing_inode(dentry);

  	__u32 magic_etc;

  	unsigned tocopy, i;

  	int size;
  	struct vfs_cap_data caps;
  
  	memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));

  	if (!inode)

  		return -ENODATA;

  	size = __vfs_getxattr((struct dentry *)dentry, inode,
  			      XATTR_NAME_CAPS, &caps, XATTR_CAPS_SZ);

  	if (size == -ENODATA || size == -EOPNOTSUPP)

  		/* no data, that's ok */
  		return -ENODATA;

  	if (size < 0)
  		return size;

  	if (size < sizeof(magic_etc))

  		return -EINVAL;

  	cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);

  	switch (magic_etc & VFS_CAP_REVISION_MASK) {

  	case VFS_CAP_REVISION_1:
  		if (size != XATTR_CAPS_SZ_1)
  			return -EINVAL;
  		tocopy = VFS_CAP_U32_1;
  		break;
  	case VFS_CAP_REVISION_2:
  		if (size != XATTR_CAPS_SZ_2)
  			return -EINVAL;
  		tocopy = VFS_CAP_U32_2;
  		break;

  	default:
  		return -EINVAL;
  	}

  	CAP_FOR_EACH_U32(i) {

  		if (i >= tocopy)
  			break;
  		cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
  		cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);

  	}

  	cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
  	cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;

  	return 0;

  }

  /*
   * Attempt to get the on-exec apply capability sets for an executable file from
   * its xattrs and, if present, apply them to the proposed credentials being
   * constructed by execve().
   */

  static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)

  {

  	int rc = 0;

  	struct cpu_vfs_cap_data vcaps;

  	bprm_clear_caps(bprm);

  	if (!file_caps_enabled)
  		return 0;

  	if (!mnt_may_suid(bprm->file->f_path.mnt))

  		return 0;

  
  	/*
  	 * This check is redundant with mnt_may_suid() but is kept to make
  	 * explicit that capability bits are limited to s_user_ns and its
  	 * descendants.
  	 */

  	if (!current_in_userns(bprm->file->f_path.mnt->mnt_sb->s_user_ns))
  		return 0;

  	rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);

  	if (rc < 0) {
  		if (rc == -EINVAL)
  			printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s
  ",
  				__func__, rc, bprm->filename);
  		else if (rc == -ENODATA)
  			rc = 0;

  		goto out;
  	}

  	rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);

  	if (rc == -EINVAL)
  		printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s
  ",
  		       __func__, rc, bprm->filename);

  
  out:

  	if (rc)
  		bprm_clear_caps(bprm);
  
  	return rc;
  }

  /**
   * cap_bprm_set_creds - Set up the proposed credentials for execve().
   * @bprm: The execution parameters, including the proposed creds
   *
   * Set up the proposed credentials for a new execution context being
   * constructed by execve().  The proposed creds in @bprm->cred is altered,
   * which won't take effect immediately.  Returns 0 if successful, -ve on error.

   */
  int cap_bprm_set_creds(struct linux_binprm *bprm)

  {

  	const struct cred *old = current_cred();
  	struct cred *new = bprm->cred;

  	bool effective, has_cap = false, is_setid;

  	int ret;

  	kuid_t root_uid;

  	if (WARN_ON(!cap_ambient_invariant_ok(old)))
  		return -EPERM;

  	effective = false;

  	ret = get_file_caps(bprm, &effective, &has_cap);

  	if (ret < 0)
  		return ret;

  	root_uid = make_kuid(new->user_ns, 0);

  	if (!issecure(SECURE_NOROOT)) {
  		/*

  		 * If the legacy file capability is set, then don't set privs
  		 * for a setuid root binary run by a non-root user.  Do set it
  		 * for a root user just to cause least surprise to an admin.
  		 */

  		if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {

  			warn_setuid_and_fcaps_mixed(bprm->filename);
  			goto skip;
  		}
  		/*

  		 * To support inheritance of root-permissions and suid-root
  		 * executables under compatibility mode, we override the
  		 * capability sets for the file.
  		 *

  		 * If only the real uid is 0, we do not set the effective bit.

  		 */

  		if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {

  			/* pP' = (cap_bset & ~0) | (pI & ~0) */

  			new->cap_permitted = cap_combine(old->cap_bset,
  							 old->cap_inheritable);

  		}

  		if (uid_eq(new->euid, root_uid))

  			effective = true;

  	}

  skip:

  	/* if we have fs caps, clear dangerous personality flags */
  	if (!cap_issubset(new->cap_permitted, old->cap_permitted))
  		bprm->per_clear |= PER_CLEAR_ON_SETID;

  	/* Don't let someone trace a set[ug]id/setpcap binary with the revised

  	 * credentials unless they have the appropriate permit.
  	 *
  	 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.

  	 */

  	is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
  
  	if ((is_setid ||

  	     !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
  	    bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
  		/* downgrade; they get no more than they had, and maybe less */

  		if (!capable(CAP_SETUID) ||
  		    (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {

  			new->euid = new->uid;
  			new->egid = new->gid;

  		}

  		new->cap_permitted = cap_intersect(new->cap_permitted,
  						   old->cap_permitted);

  	}

  	new->suid = new->fsuid = new->euid;
  	new->sgid = new->fsgid = new->egid;

  	/* File caps or setid cancels ambient. */
  	if (has_cap || is_setid)
  		cap_clear(new->cap_ambient);
  
  	/*
  	 * Now that we've computed pA', update pP' to give:
  	 *   pP' = (X & fP) | (pI & fI) | pA'
  	 */
  	new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
  
  	/*
  	 * Set pE' = (fE ? pP' : pA').  Because pA' is zero if fE is set,
  	 * this is the same as pE' = (fE ? pP' : 0) | pA'.
  	 */

  	if (effective)
  		new->cap_effective = new->cap_permitted;
  	else

  		new->cap_effective = new->cap_ambient;
  
  	if (WARN_ON(!cap_ambient_invariant_ok(new)))
  		return -EPERM;

  	bprm->cap_effective = effective;

  	/*
  	 * Audit candidate if current->cap_effective is set
  	 *
  	 * We do not bother to audit if 3 things are true:
  	 *   1) cap_effective has all caps
  	 *   2) we are root
  	 *   3) root is supposed to have all caps (SECURE_NOROOT)
  	 * Since this is just a normal root execing a process.
  	 *
  	 * Number 1 above might fail if you don't have a full bset, but I think
  	 * that is interesting information to audit.
  	 */

  	if (!cap_issubset(new->cap_effective, new->cap_ambient)) {

  		if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||

  		    !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||

  		    issecure(SECURE_NOROOT)) {
  			ret = audit_log_bprm_fcaps(bprm, new, old);
  			if (ret < 0)
  				return ret;
  		}

  	}

  	new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);

  
  	if (WARN_ON(!cap_ambient_invariant_ok(new)))
  		return -EPERM;

  	return 0;

  }

  /**
   * cap_bprm_secureexec - Determine whether a secure execution is required
   * @bprm: The execution parameters
   *
   * Determine whether a secure execution is required, return 1 if it is, and 0
   * if it is not.
   *
   * The credentials have been committed by this point, and so are no longer
   * available through @bprm->cred.

   */
  int cap_bprm_secureexec(struct linux_binprm *bprm)

  {

  	const struct cred *cred = current_cred();

  	kuid_t root_uid = make_kuid(cred->user_ns, 0);

  	if (!uid_eq(cred->uid, root_uid)) {

  		if (bprm->cap_effective)
  			return 1;

  		if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))

  			return 1;
  	}

  	return (!uid_eq(cred->euid, cred->uid) ||
  		!gid_eq(cred->egid, cred->gid));

  }

  /**
   * cap_inode_setxattr - Determine whether an xattr may be altered
   * @dentry: The inode/dentry being altered
   * @name: The name of the xattr to be changed
   * @value: The value that the xattr will be changed to
   * @size: The size of value
   * @flags: The replacement flag
   *
   * Determine whether an xattr may be altered or set on an inode, returning 0 if
   * permission is granted, -ve if denied.
   *
   * This is used to make sure security xattrs don't get updated or set by those
   * who aren't privileged to do so.
   */

  int cap_inode_setxattr(struct dentry *dentry, const char *name,
  		       const void *value, size_t size, int flags)

  {

  	if (!strcmp(name, XATTR_NAME_CAPS)) {
  		if (!capable(CAP_SETFCAP))
  			return -EPERM;
  		return 0;

  	}
  
  	if (!strncmp(name, XATTR_SECURITY_PREFIX,

  		     sizeof(XATTR_SECURITY_PREFIX) - 1) &&

  	    !capable(CAP_SYS_ADMIN))
  		return -EPERM;
  	return 0;
  }

  /**
   * cap_inode_removexattr - Determine whether an xattr may be removed
   * @dentry: The inode/dentry being altered
   * @name: The name of the xattr to be changed
   *
   * Determine whether an xattr may be removed from an inode, returning 0 if
   * permission is granted, -ve if denied.
   *
   * This is used to make sure security xattrs don't get removed by those who
   * aren't privileged to remove them.
   */

  int cap_inode_removexattr(struct dentry *dentry, const char *name)

  {

  	if (!strcmp(name, XATTR_NAME_CAPS)) {
  		if (!capable(CAP_SETFCAP))
  			return -EPERM;
  		return 0;

  	}
  
  	if (!strncmp(name, XATTR_SECURITY_PREFIX,

  		     sizeof(XATTR_SECURITY_PREFIX) - 1) &&

  	    !capable(CAP_SYS_ADMIN))
  		return -EPERM;
  	return 0;
  }

  /*

   * cap_emulate_setxuid() fixes the effective / permitted capabilities of
   * a process after a call to setuid, setreuid, or setresuid.
   *
   *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
   *  {r,e,s}uid != 0, the permitted and effective capabilities are
   *  cleared.
   *
   *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
   *  capabilities of the process are cleared.
   *
   *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
   *  capabilities are set to the permitted capabilities.
   *

   *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should

   *  never happen.
   *

   *  -astor

   *
   * cevans - New behaviour, Oct '99
   * A process may, via prctl(), elect to keep its capabilities when it
   * calls setuid() and switches away from uid==0. Both permitted and
   * effective sets will be retained.
   * Without this change, it was impossible for a daemon to drop only some
   * of its privilege. The call to setuid(!=0) would drop all privileges!
   * Keeping uid 0 is not an option because uid 0 owns too many vital
   * files..
   * Thanks to Olaf Kirch and Peter Benie for spotting this.
   */

  static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)

  {

  	kuid_t root_uid = make_kuid(old->user_ns, 0);
  
  	if ((uid_eq(old->uid, root_uid) ||
  	     uid_eq(old->euid, root_uid) ||
  	     uid_eq(old->suid, root_uid)) &&
  	    (!uid_eq(new->uid, root_uid) &&
  	     !uid_eq(new->euid, root_uid) &&

  	     !uid_eq(new->suid, root_uid))) {
  		if (!issecure(SECURE_KEEP_CAPS)) {
  			cap_clear(new->cap_permitted);
  			cap_clear(new->cap_effective);
  		}
  
  		/*
  		 * Pre-ambient programs expect setresuid to nonroot followed
  		 * by exec to drop capabilities.  We should make sure that
  		 * this remains the case.
  		 */
  		cap_clear(new->cap_ambient);

  	}

  	if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))

  		cap_clear(new->cap_effective);

  	if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))

  		new->cap_effective = new->cap_permitted;

  }

  /**
   * cap_task_fix_setuid - Fix up the results of setuid() call
   * @new: The proposed credentials
   * @old: The current task's current credentials
   * @flags: Indications of what has changed
   *
   * Fix up the results of setuid() call before the credential changes are
   * actually applied, returning 0 to grant the changes, -ve to deny them.
   */

  int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)

  {
  	switch (flags) {
  	case LSM_SETID_RE:
  	case LSM_SETID_ID:
  	case LSM_SETID_RES:

  		/* juggle the capabilities to follow [RES]UID changes unless
  		 * otherwise suppressed */

  		if (!issecure(SECURE_NO_SETUID_FIXUP))
  			cap_emulate_setxuid(new, old);

  		break;

  	case LSM_SETID_FS:
  		/* juggle the capabilties to follow FSUID changes, unless
  		 * otherwise suppressed
  		 *

  		 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
  		 *          if not, we might be a bit too harsh here.
  		 */
  		if (!issecure(SECURE_NO_SETUID_FIXUP)) {

  			kuid_t root_uid = make_kuid(old->user_ns, 0);
  			if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))

  				new->cap_effective =
  					cap_drop_fs_set(new->cap_effective);

  			if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))

  				new->cap_effective =
  					cap_raise_fs_set(new->cap_effective,
  							 new->cap_permitted);

  		}

  		break;

  	default:
  		return -EINVAL;
  	}
  
  	return 0;
  }

  /*
   * Rationale: code calling task_setscheduler, task_setioprio, and
   * task_setnice, assumes that
   *   . if capable(cap_sys_nice), then those actions should be allowed
   *   . if not capable(cap_sys_nice), but acting on your own processes,
   *   	then those actions should be allowed
   * This is insufficient now since you can call code without suid, but
   * yet with increased caps.
   * So we check for increased caps on the target process.
   */

  static int cap_safe_nice(struct task_struct *p)

  {

  	int is_subset, ret = 0;

  
  	rcu_read_lock();
  	is_subset = cap_issubset(__task_cred(p)->cap_permitted,
  				 current_cred()->cap_permitted);

  	if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
  		ret = -EPERM;

  	rcu_read_unlock();

  	return ret;

  }

  /**
   * cap_task_setscheduler - Detemine if scheduler policy change is permitted
   * @p: The task to affect

   *
   * Detemine if the requested scheduler policy change is permitted for the
   * specified task, returning 0 if permission is granted, -ve if denied.
   */

  int cap_task_setscheduler(struct task_struct *p)

  {
  	return cap_safe_nice(p);
  }

  /**
   * cap_task_ioprio - Detemine if I/O priority change is permitted
   * @p: The task to affect
   * @ioprio: The I/O priority to set
   *
   * Detemine if the requested I/O priority change is permitted for the specified
   * task, returning 0 if permission is granted, -ve if denied.
   */
  int cap_task_setioprio(struct task_struct *p, int ioprio)

  {
  	return cap_safe_nice(p);
  }

  /**
   * cap_task_ioprio - Detemine if task priority change is permitted
   * @p: The task to affect
   * @nice: The nice value to set
   *
   * Detemine if the requested task priority change is permitted for the
   * specified task, returning 0 if permission is granted, -ve if denied.
   */
  int cap_task_setnice(struct task_struct *p, int nice)

  {
  	return cap_safe_nice(p);
  }

  /*

   * Implement PR_CAPBSET_DROP.  Attempt to remove the specified capability from
   * the current task's bounding set.  Returns 0 on success, -ve on error.

   */

  static int cap_prctl_drop(unsigned long cap)

  {

  	struct cred *new;

  	if (!ns_capable(current_user_ns(), CAP_SETPCAP))

  		return -EPERM;
  	if (!cap_valid(cap))
  		return -EINVAL;

  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;

  	cap_lower(new->cap_bset, cap);

  	return commit_creds(new);

  }

  /**
   * cap_task_prctl - Implement process control functions for this security module
   * @option: The process control function requested
   * @arg2, @arg3, @arg4, @arg5: The argument data for this function
   *
   * Allow process control functions (sys_prctl()) to alter capabilities; may
   * also deny access to other functions not otherwise implemented here.
   *
   * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
   * here, other -ve on error.  If -ENOSYS is returned, sys_prctl() and other LSM
   * modules will consider performing the function.
   */

  int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,

  		   unsigned long arg4, unsigned long arg5)

  {

  	const struct cred *old = current_cred();

  	struct cred *new;

  	switch (option) {
  	case PR_CAPBSET_READ:
  		if (!cap_valid(arg2))

  			return -EINVAL;
  		return !!cap_raised(old->cap_bset, arg2);

  	case PR_CAPBSET_DROP:

  		return cap_prctl_drop(arg2);

  
  	/*
  	 * The next four prctl's remain to assist with transitioning a
  	 * system from legacy UID=0 based privilege (when filesystem
  	 * capabilities are not in use) to a system using filesystem
  	 * capabilities only - as the POSIX.1e draft intended.
  	 *
  	 * Note:
  	 *
  	 *  PR_SET_SECUREBITS =
  	 *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
  	 *    | issecure_mask(SECURE_NOROOT)
  	 *    | issecure_mask(SECURE_NOROOT_LOCKED)
  	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
  	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
  	 *
  	 * will ensure that the current process and all of its
  	 * children will be locked into a pure
  	 * capability-based-privilege environment.
  	 */
  	case PR_SET_SECUREBITS:

  		if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
  		     & (old->securebits ^ arg2))			/*[1]*/
  		    || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))	/*[2]*/

  		    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))	/*[3]*/

  		    || (cap_capable(current_cred(),

  				    current_cred()->user_ns, CAP_SETPCAP,

  				    SECURITY_CAP_AUDIT) != 0)		/*[4]*/

  			/*
  			 * [1] no changing of bits that are locked
  			 * [2] no unlocking of locks
  			 * [3] no setting of unsupported bits
  			 * [4] doing anything requires privilege (go read about
  			 *     the "sendmail capabilities bug")
  			 */

  		    )
  			/* cannot change a locked bit */

  			return -EPERM;
  
  		new = prepare_creds();
  		if (!new)
  			return -ENOMEM;

  		new->securebits = arg2;

  		return commit_creds(new);

  	case PR_GET_SECUREBITS:

  		return old->securebits;

  	case PR_GET_KEEPCAPS:

  		return !!issecure(SECURE_KEEP_CAPS);

  	case PR_SET_KEEPCAPS:
  		if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */

  			return -EINVAL;

  		if (issecure(SECURE_KEEP_CAPS_LOCKED))

  			return -EPERM;
  
  		new = prepare_creds();
  		if (!new)
  			return -ENOMEM;

  		if (arg2)
  			new->securebits |= issecure_mask(SECURE_KEEP_CAPS);

  		else

  			new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);

  		return commit_creds(new);

  	case PR_CAP_AMBIENT:
  		if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
  			if (arg3 | arg4 | arg5)
  				return -EINVAL;
  
  			new = prepare_creds();
  			if (!new)
  				return -ENOMEM;
  			cap_clear(new->cap_ambient);
  			return commit_creds(new);
  		}
  
  		if (((!cap_valid(arg3)) | arg4 | arg5))
  			return -EINVAL;
  
  		if (arg2 == PR_CAP_AMBIENT_IS_SET) {
  			return !!cap_raised(current_cred()->cap_ambient, arg3);
  		} else if (arg2 != PR_CAP_AMBIENT_RAISE &&
  			   arg2 != PR_CAP_AMBIENT_LOWER) {
  			return -EINVAL;
  		} else {
  			if (arg2 == PR_CAP_AMBIENT_RAISE &&
  			    (!cap_raised(current_cred()->cap_permitted, arg3) ||
  			     !cap_raised(current_cred()->cap_inheritable,

  					 arg3) ||
  			     issecure(SECURE_NO_CAP_AMBIENT_RAISE)))

  				return -EPERM;
  
  			new = prepare_creds();
  			if (!new)
  				return -ENOMEM;
  			if (arg2 == PR_CAP_AMBIENT_RAISE)
  				cap_raise(new->cap_ambient, arg3);
  			else
  				cap_lower(new->cap_ambient, arg3);
  			return commit_creds(new);
  		}

  	default:
  		/* No functionality available - continue with default */

  		return -ENOSYS;

  	}

  }

  /**

   * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
   * @mm: The VM space in which the new mapping is to be made
   * @pages: The size of the mapping
   *
   * Determine whether the allocation of a new virtual mapping by the current

   * task is permitted, returning 1 if permission is granted, 0 if not.

   */

  int cap_vm_enough_memory(struct mm_struct *mm, long pages)

  {
  	int cap_sys_admin = 0;

  	if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,

  			SECURITY_CAP_NOAUDIT) == 0)

  		cap_sys_admin = 1;

  	return cap_sys_admin;

  }

  
  /*

   * cap_mmap_addr - check if able to map given addr

   * @addr: address attempting to be mapped

   *

   * If the process is attempting to map memory below dac_mmap_min_addr they need

   * CAP_SYS_RAWIO.  The other parameters to this function are unused by the
   * capability security module.  Returns 0 if this mapping should be allowed
   * -EPERM if not.
   */

  int cap_mmap_addr(unsigned long addr)

  {
  	int ret = 0;

  	if (addr < dac_mmap_min_addr) {

  		ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,

  				  SECURITY_CAP_AUDIT);
  		/* set PF_SUPERPRIV if it turns out we allow the low mmap */
  		if (ret == 0)
  			current->flags |= PF_SUPERPRIV;
  	}
  	return ret;
  }

  int cap_mmap_file(struct file *file, unsigned long reqprot,
  		  unsigned long prot, unsigned long flags)

  {

  	return 0;

  }

  
  #ifdef CONFIG_SECURITY
  
  struct security_hook_list capability_hooks[] = {
  	LSM_HOOK_INIT(capable, cap_capable),
  	LSM_HOOK_INIT(settime, cap_settime),
  	LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
  	LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
  	LSM_HOOK_INIT(capget, cap_capget),
  	LSM_HOOK_INIT(capset, cap_capset),
  	LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
  	LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec),
  	LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
  	LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
  	LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
  	LSM_HOOK_INIT(mmap_file, cap_mmap_file),
  	LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
  	LSM_HOOK_INIT(task_prctl, cap_task_prctl),
  	LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
  	LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
  	LSM_HOOK_INIT(task_setnice, cap_task_setnice),
  	LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
  };
  
  void __init capability_add_hooks(void)
  {
  	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
  }
  
  #endif /* CONFIG_SECURITY */