AppArmor: file enforcement routines

/*

 * 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;

	uid_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", fsuid);

		audit_log_format(ab, " ouid=%d", 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, uid_t ouid, const char *info, int error)

{

	int type = AUDIT_APPARMOR_AUTO;

	struct common_audit_data sa;

	COMMON_AUDIT_DATA_INIT(&sa, NONE);

	sa.aad.op = op,

	sa.aad.fs.request = request;

	sa.aad.name = name;

	sa.aad.fs.target = target;

	sa.aad.fs.ouid = ouid;

	sa.aad.info = info;

	sa.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;

	new |= AA_MAY_META_READ;

	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 (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);

	}

	/* change_profile wasn't determined by ownership in old mapping */

	if (ACCEPT_TABLE(dfa)[state] & 0x80000000)

		perms.allow |= AA_MAY_CHANGE_PROFILE;

	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_get_name(path, flags, &buffer, &name);

	if (error) {

		if (error == -ENOENT && is_deleted(path->dentry)) {

			/* Access to open files that are deleted are

			 * give a pass (implicit delegation)

			 */

			error = 0;

			perms.allow = request;

		} else if (error == -ENOENT)

			info = "Failed name lookup - deleted entry";

		else if (error == -ESTALE)

			info = "Failed name lookup - disconnected path";

		else if (error == -ENAMETOOLONG)

			info = "Failed name lookup - name too long";

		else

			info = "Failed name lookup";

	} 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_get_name(&link, profile->path_flags, &buffer, &lname);

	if (error)

		goto audit;

	/* buffer2 freed below, tname is pointer in buffer2 */

	error = aa_get_name(&target, profile->path_flags, &buffer2, &tname);

	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->f_path.dentry->d_inode->i_uid,

		.mode = file->f_path.dentry->d_inode->i_mode

	};

	return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,

			    request, &cond);

}

/*

 * AppArmor security module

 *

 * This file contains AppArmor file mediation function definitions.

 *

 * 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.

 */

#ifndef __AA_FILE_H

#define __AA_FILE_H

#include <linux/path.h>

#include "domain.h"

#include "match.h"

struct aa_profile;

/*

 * We use MAY_EXEC, MAY_WRITE, MAY_READ, MAY_APPEND and the following flags

 * for profile permissions

 */

#define AA_MAY_CREATE                  0x0010

#define AA_MAY_DELETE                  0x0020

#define AA_MAY_META_WRITE              0x0040

#define AA_MAY_META_READ               0x0080

#define AA_MAY_CHMOD                   0x0100

#define AA_MAY_CHOWN                   0x0200

#define AA_MAY_LOCK                    0x0400

#define AA_EXEC_MMAP                   0x0800

#define AA_MAY_LINK			0x1000

#define AA_LINK_SUBSET			AA_MAY_LOCK	/* overlaid */

#define AA_MAY_ONEXEC			0x40000000	/* exec allows onexec */

#define AA_MAY_CHANGE_PROFILE		0x80000000

#define AA_MAY_CHANGEHAT		0x80000000	/* ctrl auditing only */

#define AA_AUDIT_FILE_MASK	(MAY_READ | MAY_WRITE | MAY_EXEC | MAY_APPEND |\

				 AA_MAY_CREATE | AA_MAY_DELETE |	\

				 AA_MAY_META_READ | AA_MAY_META_WRITE | \

				 AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_LOCK | \

				 AA_EXEC_MMAP | AA_MAY_LINK)

/*

 * The xindex is broken into 3 parts

 * - index - an index into either the exec name table or the variable table

 * - exec type - which determines how the executable name and index are used

 * - flags - which modify how the destination name is applied

 */

#define AA_X_INDEX_MASK		0x03ff

#define AA_X_TYPE_MASK		0x0c00

#define AA_X_TYPE_SHIFT		10

#define AA_X_NONE		0x0000

#define AA_X_NAME		0x0400	/* use executable name px */

#define AA_X_TABLE		0x0800	/* use a specified name ->n# */

#define AA_X_UNSAFE		0x1000

#define AA_X_CHILD		0x2000	/* make >AA_X_NONE apply to children */

#define AA_X_INHERIT		0x4000

#define AA_X_UNCONFINED		0x8000

/* AA_SECURE_X_NEEDED - is passed in the bprm->unsafe field */

#define AA_SECURE_X_NEEDED	0x8000

/* need to make conditional which ones are being set */

struct path_cond {

	uid_t uid;

	umode_t mode;

};

/* struct file_perms - file permission

 * @allow: mask of permissions that are allowed

 * @audit: mask of permissions to force an audit message for

 * @quiet: mask of permissions to quiet audit messages for

 * @kill: mask of permissions that when matched will kill the task

 * @xindex: exec transition index if @allow contains MAY_EXEC

 *

 * The @audit and @queit mask should be mutually exclusive.

 */

struct file_perms {

	u32 allow;

	u32 audit;

	u32 quiet;

	u32 kill;

	u16 xindex;

};

extern struct file_perms nullperms;

#define COMBINED_PERM_MASK(X) ((X).allow | (X).audit | (X).quiet | (X).kill)

/* FIXME: split perms from dfa and match this to description

 *        also add delegation info.

 */

static inline u16 dfa_map_xindex(u16 mask)

{

	u16 old_index = (mask >> 10) & 0xf;

	u16 index = 0;

	if (mask & 0x100)

		index |= AA_X_UNSAFE;

	if (mask & 0x200)

		index |= AA_X_INHERIT;

	if (mask & 0x80)

		index |= AA_X_UNCONFINED;

	if (old_index == 1) {

		index |= AA_X_UNCONFINED;

	} else if (old_index == 2) {

		index |= AA_X_NAME;

	} else if (old_index == 3) {

		index |= AA_X_NAME | AA_X_CHILD;

	} else {

		index |= AA_X_TABLE;

		index |= old_index - 4;

	}

	return index;

}

/*

 * map old dfa inline permissions to new format

 */

#define dfa_user_allow(dfa, state) (((ACCEPT_TABLE(dfa)[state]) & 0x7f) | \

				    ((ACCEPT_TABLE(dfa)[state]) & 0x80000000))

#define dfa_user_audit(dfa, state) ((ACCEPT_TABLE2(dfa)[state]) & 0x7f)

#define dfa_user_quiet(dfa, state) (((ACCEPT_TABLE2(dfa)[state]) >> 7) & 0x7f)

#define dfa_user_xindex(dfa, state) \

	(dfa_map_xindex(ACCEPT_TABLE(dfa)[state] & 0x3fff))

#define dfa_other_allow(dfa, state) ((((ACCEPT_TABLE(dfa)[state]) >> 14) & \

				      0x7f) |				\

				     ((ACCEPT_TABLE(dfa)[state]) & 0x80000000))

#define dfa_other_audit(dfa, state) (((ACCEPT_TABLE2(dfa)[state]) >> 14) & 0x7f)

#define dfa_other_quiet(dfa, state) \

	((((ACCEPT_TABLE2(dfa)[state]) >> 7) >> 14) & 0x7f)

#define dfa_other_xindex(dfa, state) \

	dfa_map_xindex((ACCEPT_TABLE(dfa)[state] >> 14) & 0x3fff)

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, uid_t ouid, const char *info, int error);

/**

 * struct aa_file_rules - components used for file rule permissions

 * @dfa: dfa to match path names and conditionals against

 * @perms: permission table indexed by the matched state accept entry of @dfa

 * @trans: transition table for indexed by named x transitions

 *

 * File permission are determined by matching a path against @dfa and then

 * then using the value of the accept entry for the matching state as

 * an index into @perms.  If a named exec transition is required it is

 * looked up in the transition table.

 */

struct aa_file_rules {

	unsigned int start;

	struct aa_dfa *dfa;

	/* struct perms perms; */

	struct aa_domain trans;

	/* TODO: add delegate table */

};

unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,

			  const char *name, struct path_cond *cond,

			  struct file_perms *perms);

int aa_path_perm(int op, struct aa_profile *profile, struct path *path,

		 int flags, u32 request, struct path_cond *cond);

int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,

		 struct path *new_dir, struct dentry *new_dentry);

int aa_file_perm(int op, struct aa_profile *profile, struct file *file,

		 u32 request);

static inline void aa_free_file_rules(struct aa_file_rules *rules)

{

	aa_put_dfa(rules->dfa);

	aa_free_domain_entries(&rules->trans);

}

#define ACC_FMODE(x) (("\000\004\002\006"[(x)&O_ACCMODE]) | (((x) << 1) & 0x40))

/* from namei.c */

#define MAP_OPEN_FLAGS(x) ((((x) + 1) & O_ACCMODE) ? (x) + 1 : (x))

/**

 * aa_map_file_perms - map file flags to AppArmor permissions

 * @file: open file to map flags to AppArmor permissions

 *

 * Returns: apparmor permission set for the file

 */

static inline u32 aa_map_file_to_perms(struct file *file)

{

	int flags = MAP_OPEN_FLAGS(file->f_flags);

	u32 perms = ACC_FMODE(file->f_mode);

	if ((flags & O_APPEND) && (perms & MAY_WRITE))

		perms = (perms & ~MAY_WRITE) | MAY_APPEND;

	/* trunc implies write permission */

	if (flags & O_TRUNC)

		perms |= MAY_WRITE;

	if (flags & O_CREAT)

		perms |= AA_MAY_CREATE;

	return perms;

}

#endif /* __AA_FILE_H */