/*
   * AppArmor security module
   *
   * This file contains AppArmor mediation of files
   *
   * Copyright (C) 1998-2008 Novell/SUSE
   * Copyright 2009-2010 Canonical Ltd.
   *
   * 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, version 2 of the
   * License.
   */
  
  #include "include/apparmor.h"
  #include "include/audit.h"
  #include "include/file.h"
  #include "include/match.h"
  #include "include/path.h"
  #include "include/policy.h"
  
  struct file_perms nullperms;
  
  
  /**
   * audit_file_mask - convert mask to permission string
   * @buffer: buffer to write string to (NOT NULL)
   * @mask: permission mask to convert
   */
  static void audit_file_mask(struct audit_buffer *ab, u32 mask)
  {
  	char str[10];
  
  	char *m = str;
  
  	if (mask & AA_EXEC_MMAP)
  		*m++ = 'm';
  	if (mask & (MAY_READ | AA_MAY_META_READ))
  		*m++ = 'r';
  	if (mask & (MAY_WRITE | AA_MAY_META_WRITE | AA_MAY_CHMOD |
  		    AA_MAY_CHOWN))
  		*m++ = 'w';
  	else if (mask & MAY_APPEND)
  		*m++ = 'a';
  	if (mask & AA_MAY_CREATE)
  		*m++ = 'c';
  	if (mask & AA_MAY_DELETE)
  		*m++ = 'd';
  	if (mask & AA_MAY_LINK)
  		*m++ = 'l';
  	if (mask & AA_MAY_LOCK)
  		*m++ = 'k';
  	if (mask & MAY_EXEC)
  		*m++ = 'x';
  	*m = '\0';
  
  	audit_log_string(ab, str);
  }
  
  /**
   * file_audit_cb - call back for file specific audit fields
   * @ab: audit_buffer  (NOT NULL)
   * @va: audit struct to audit values of  (NOT NULL)
   */
  static void file_audit_cb(struct audit_buffer *ab, void *va)
  {
  	struct common_audit_data *sa = va;
  	kuid_t fsuid = current_fsuid();
  
  	if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
  		audit_log_format(ab, " requested_mask=");
  		audit_file_mask(ab, sa->aad->fs.request);
  	}
  	if (sa->aad->fs.denied & AA_AUDIT_FILE_MASK) {
  		audit_log_format(ab, " denied_mask=");
  		audit_file_mask(ab, sa->aad->fs.denied);
  	}
  	if (sa->aad->fs.request & AA_AUDIT_FILE_MASK) {
  		audit_log_format(ab, " fsuid=%d",
  				 from_kuid(&init_user_ns, fsuid));
  		audit_log_format(ab, " ouid=%d",
  				 from_kuid(&init_user_ns, sa->aad->fs.ouid));
  	}
  
  	if (sa->aad->fs.target) {
  		audit_log_format(ab, " target=");
  		audit_log_untrustedstring(ab, sa->aad->fs.target);
  	}
  }
  
  /**
   * aa_audit_file - handle the auditing of file operations
   * @profile: the profile being enforced  (NOT NULL)
   * @perms: the permissions computed for the request (NOT NULL)
   * @gfp: allocation flags
   * @op: operation being mediated
   * @request: permissions requested
   * @name: name of object being mediated (MAYBE NULL)
   * @target: name of target (MAYBE NULL)
   * @ouid: object uid
   * @info: extra information message (MAYBE NULL)
   * @error: 0 if operation allowed else failure error code
   *
   * Returns: %0 or error on failure
   */
  int aa_audit_file(struct aa_profile *profile, struct file_perms *perms,
  		  gfp_t gfp, int op, u32 request, const char *name,
  		  const char *target, kuid_t ouid, const char *info, int error)
  {
  	int type = AUDIT_APPARMOR_AUTO;
  	struct common_audit_data sa;
  	struct apparmor_audit_data aad = {0,};
  	sa.type = LSM_AUDIT_DATA_NONE;
  	sa.aad = &aad;
  	aad.op = op,
  	aad.fs.request = request;
  	aad.name = name;
  	aad.fs.target = target;
  	aad.fs.ouid = ouid;
  	aad.info = info;
  	aad.error = error;
  
  	if (likely(!sa.aad->error)) {
  		u32 mask = perms->audit;
  
  		if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
  			mask = 0xffff;
  
  		/* mask off perms that are not being force audited */
  		sa.aad->fs.request &= mask;
  
  		if (likely(!sa.aad->fs.request))
  			return 0;
  		type = AUDIT_APPARMOR_AUDIT;
  	} else {
  		/* only report permissions that were denied */
  		sa.aad->fs.request = sa.aad->fs.request & ~perms->allow;
  
  		if (sa.aad->fs.request & perms->kill)
  			type = AUDIT_APPARMOR_KILL;
  
  		/* quiet known rejects, assumes quiet and kill do not overlap */
  		if ((sa.aad->fs.request & perms->quiet) &&
  		    AUDIT_MODE(profile) != AUDIT_NOQUIET &&
  		    AUDIT_MODE(profile) != AUDIT_ALL)
  			sa.aad->fs.request &= ~perms->quiet;
  
  		if (!sa.aad->fs.request)
  			return COMPLAIN_MODE(profile) ? 0 : sa.aad->error;
  	}
  
  	sa.aad->fs.denied = sa.aad->fs.request & ~perms->allow;
  	return aa_audit(type, profile, gfp, &sa, file_audit_cb);
  }
  
  /**
   * map_old_perms - map old file perms layout to the new layout
   * @old: permission set in old mapping
   *
   * Returns: new permission mapping
   */
  static u32 map_old_perms(u32 old)
  {
  	u32 new = old & 0xf;
  	if (old & MAY_READ)
  		new |= AA_MAY_META_READ;
  	if (old & MAY_WRITE)
  		new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
  			AA_MAY_CHMOD | AA_MAY_CHOWN;
  	if (old & 0x10)
  		new |= AA_MAY_LINK;
  	/* the old mapping lock and link_subset flags where overlaid
  	 * and use was determined by part of a pair that they were in
  	 */
  	if (old & 0x20)
  		new |= AA_MAY_LOCK | AA_LINK_SUBSET;
  	if (old & 0x40)	/* AA_EXEC_MMAP */
  		new |= AA_EXEC_MMAP;
  
  	return new;
  }
  
  /**
   * compute_perms - convert dfa compressed perms to internal perms
   * @dfa: dfa to compute perms for   (NOT NULL)
   * @state: state in dfa
   * @cond:  conditions to consider  (NOT NULL)
   *
   * TODO: convert from dfa + state to permission entry, do computation conversion
   *       at load time.
   *
   * Returns: computed permission set
   */
  static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
  				       struct path_cond *cond)
  {
  	struct file_perms perms;
  
  	/* FIXME: change over to new dfa format
  	 * currently file perms are encoded in the dfa, new format
  	 * splits the permissions from the dfa.  This mapping can be
  	 * done at profile load
  	 */
  	perms.kill = 0;
  
  	if (uid_eq(current_fsuid(), cond->uid)) {
  		perms.allow = map_old_perms(dfa_user_allow(dfa, state));
  		perms.audit = map_old_perms(dfa_user_audit(dfa, state));
  		perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
  		perms.xindex = dfa_user_xindex(dfa, state);
  	} else {
  		perms.allow = map_old_perms(dfa_other_allow(dfa, state));
  		perms.audit = map_old_perms(dfa_other_audit(dfa, state));
  		perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
  		perms.xindex = dfa_other_xindex(dfa, state);
  	}
  	perms.allow |= AA_MAY_META_READ;
  
  	/* change_profile wasn't determined by ownership in old mapping */
  	if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
  		perms.allow |= AA_MAY_CHANGE_PROFILE;
  	if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
  		perms.allow |= AA_MAY_ONEXEC;
  
  	return perms;
  }
  
  /**
   * aa_str_perms - find permission that match @name
   * @dfa: to match against  (MAYBE NULL)
   * @state: state to start matching in
   * @name: string to match against dfa  (NOT NULL)
   * @cond: conditions to consider for permission set computation  (NOT NULL)
   * @perms: Returns - the permissions found when matching @name
   *
   * Returns: the final state in @dfa when beginning @start and walking @name
   */
  unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
  			  const char *name, struct path_cond *cond,
  			  struct file_perms *perms)
  {
  	unsigned int state;
  	if (!dfa) {
  		*perms = nullperms;
  		return DFA_NOMATCH;
  	}
  
  	state = aa_dfa_match(dfa, start, name);
  	*perms = compute_perms(dfa, state, cond);
  
  	return state;
  }
  
  /**
   * is_deleted - test if a file has been completely unlinked
   * @dentry: dentry of file to test for deletion  (NOT NULL)
   *
   * Returns: %1 if deleted else %0
   */
  static inline bool is_deleted(struct dentry *dentry)
  {
  	if (d_unlinked(dentry) && dentry->d_inode->i_nlink == 0)
  		return 1;
  	return 0;
  }
  
  /**
   * aa_path_perm - do permissions check & audit for @path
   * @op: operation being checked
   * @profile: profile being enforced  (NOT NULL)
   * @path: path to check permissions of  (NOT NULL)
   * @flags: any additional path flags beyond what the profile specifies
   * @request: requested permissions
   * @cond: conditional info for this request  (NOT NULL)
   *
   * Returns: %0 else error if access denied or other error
   */
  int aa_path_perm(int op, struct aa_profile *profile, struct path *path,
  		 int flags, u32 request, struct path_cond *cond)
  {
  	char *buffer = NULL;
  	struct file_perms perms = {};
  	const char *name, *info = NULL;
  	int error;
  
  	flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
  	error = aa_path_name(path, flags, &buffer, &name, &info);
  	if (error) {
  		if (error == -ENOENT && is_deleted(path->dentry)) {
  			/* Access to open files that are deleted are
  			 * give a pass (implicit delegation)
  			 */
  			error = 0;
  			info = NULL;
  			perms.allow = request;
  		}
  	} else {
  		aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
  			     &perms);
  		if (request & ~perms.allow)
  			error = -EACCES;
  	}
  	error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
  			      NULL, cond->uid, info, error);
  	kfree(buffer);
  
  	return error;
  }
  
  /**
   * xindex_is_subset - helper for aa_path_link
   * @link: link permission set
   * @target: target permission set
   *
   * test target x permissions are equal OR a subset of link x permissions
   * this is done as part of the subset test, where a hardlink must have
   * a subset of permissions that the target has.
   *
   * Returns: %1 if subset else %0
   */
  static inline bool xindex_is_subset(u32 link, u32 target)
  {
  	if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
  	    ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
  		return 0;
  
  	return 1;
  }
  
  /**
   * aa_path_link - Handle hard link permission check
   * @profile: the profile being enforced  (NOT NULL)
   * @old_dentry: the target dentry  (NOT NULL)
   * @new_dir: directory the new link will be created in  (NOT NULL)
   * @new_dentry: the link being created  (NOT NULL)
   *
   * Handle the permission test for a link & target pair.  Permission
   * is encoded as a pair where the link permission is determined
   * first, and if allowed, the target is tested.  The target test
   * is done from the point of the link match (not start of DFA)
   * making the target permission dependent on the link permission match.
   *
   * The subset test if required forces that permissions granted
   * on link are a subset of the permission granted to target.
   *
   * Returns: %0 if allowed else error
   */
  int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
  		 struct path *new_dir, struct dentry *new_dentry)
  {
  	struct path link = { new_dir->mnt, new_dentry };
  	struct path target = { new_dir->mnt, old_dentry };
  	struct path_cond cond = {
  		old_dentry->d_inode->i_uid,
  		old_dentry->d_inode->i_mode
  	};
  	char *buffer = NULL, *buffer2 = NULL;
  	const char *lname, *tname = NULL, *info = NULL;
  	struct file_perms lperms, perms;
  	u32 request = AA_MAY_LINK;
  	unsigned int state;
  	int error;
  
  	lperms = nullperms;
  
  	/* buffer freed below, lname is pointer in buffer */
  	error = aa_path_name(&link, profile->path_flags, &buffer, &lname,
  			     &info);
  	if (error)
  		goto audit;
  
  	/* buffer2 freed below, tname is pointer in buffer2 */
  	error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
  			     &info);
  	if (error)
  		goto audit;
  
  	error = -EACCES;
  	/* aa_str_perms - handles the case of the dfa being NULL */
  	state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
  			     &cond, &lperms);
  
  	if (!(lperms.allow & AA_MAY_LINK))
  		goto audit;
  
  	/* test to see if target can be paired with link */
  	state = aa_dfa_null_transition(profile->file.dfa, state);
  	aa_str_perms(profile->file.dfa, state, tname, &cond, &perms);
  
  	/* force audit/quiet masks for link are stored in the second entry
  	 * in the link pair.
  	 */
  	lperms.audit = perms.audit;
  	lperms.quiet = perms.quiet;
  	lperms.kill = perms.kill;
  
  	if (!(perms.allow & AA_MAY_LINK)) {
  		info = "target restricted";
  		goto audit;
  	}
  
  	/* done if link subset test is not required */
  	if (!(perms.allow & AA_LINK_SUBSET))
  		goto done_tests;
  
  	/* Do link perm subset test requiring allowed permission on link are a
  	 * subset of the allowed permissions on target.
  	 */
  	aa_str_perms(profile->file.dfa, profile->file.start, tname, &cond,
  		     &perms);
  
  	/* AA_MAY_LINK is not considered in the subset test */
  	request = lperms.allow & ~AA_MAY_LINK;
  	lperms.allow &= perms.allow | AA_MAY_LINK;
  
  	request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
  	if (request & ~lperms.allow) {
  		goto audit;
  	} else if ((lperms.allow & MAY_EXEC) &&
  		   !xindex_is_subset(lperms.xindex, perms.xindex)) {
  		lperms.allow &= ~MAY_EXEC;
  		request |= MAY_EXEC;
  		info = "link not subset of target";
  		goto audit;
  	}
  
  done_tests:
  	error = 0;
  
  audit:
  	error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
  			      lname, tname, cond.uid, info, error);
  	kfree(buffer);
  	kfree(buffer2);
  
  	return error;
  }
  
  /**
   * aa_file_perm - do permission revalidation check & audit for @file
   * @op: operation being checked
   * @profile: profile being enforced   (NOT NULL)
   * @file: file to revalidate access permissions on  (NOT NULL)
   * @request: requested permissions
   *
   * Returns: %0 if access allowed else error
   */
  int aa_file_perm(int op, struct aa_profile *profile, struct file *file,
  		 u32 request)
  {
  	struct path_cond cond = {
  		.uid = file_inode(file)->i_uid,
  		.mode = file_inode(file)->i_mode
  	};
  
  	return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
  			    request, &cond);
  }