AppArmor: policy routines for loading and unpacking policy

/*

 * AppArmor security module

 *

 * This file contains AppArmor policy loading interface 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 __POLICY_INTERFACE_H

#define __POLICY_INTERFACE_H

struct aa_profile *aa_unpack(void *udata, size_t size, const char **ns);

#endif /* __POLICY_INTERFACE_H */

/*

 * AppArmor security module

 *

 * This file contains AppArmor functions for unpacking policy loaded from

 * userspace.

 *

 * 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.

 *

 * AppArmor uses a serialized binary format for loading policy.

 * To find policy format documentation look in Documentation/apparmor.txt

 * All policy is validated before it is used.

 */

#include <asm/unaligned.h>

#include <linux/ctype.h>

#include <linux/errno.h>

#include "include/apparmor.h"

#include "include/audit.h"

#include "include/context.h"

#include "include/match.h"

#include "include/policy.h"

#include "include/policy_unpack.h"

#include "include/sid.h"

/*

 * The AppArmor interface treats data as a type byte followed by the

 * actual data.  The interface has the notion of a a named entry

 * which has a name (AA_NAME typecode followed by name string) followed by

 * the entries typecode and data.  Named types allow for optional

 * elements and extensions to be added and tested for without breaking

 * backwards compatibility.

 */

enum aa_code {

	AA_U8,

	AA_U16,

	AA_U32,

	AA_U64,

	AA_NAME,		/* same as string except it is items name */

	AA_STRING,

	AA_BLOB,

	AA_STRUCT,

	AA_STRUCTEND,

	AA_LIST,

	AA_LISTEND,

	AA_ARRAY,

	AA_ARRAYEND,

};

/*

 * aa_ext is the read of the buffer containing the serialized profile.  The

 * data is copied into a kernel buffer in apparmorfs and then handed off to

 * the unpack routines.

 */

struct aa_ext {

	void *start;

	void *end;

	void *pos;		/* pointer to current position in the buffer */

	u32 version;

};

/* audit callback for unpack fields */

static void audit_cb(struct audit_buffer *ab, void *va)

{

	struct common_audit_data *sa = va;

	if (sa->aad.iface.target) {

		struct aa_profile *name = sa->aad.iface.target;

		audit_log_format(ab, " name=");

		audit_log_untrustedstring(ab, name->base.hname);

	}

	if (sa->aad.iface.pos)

		audit_log_format(ab, " offset=%ld", sa->aad.iface.pos);

}

/**

 * audit_iface - do audit message for policy unpacking/load/replace/remove

 * @new: profile if it has been allocated (MAYBE NULL)

 * @name: name of the profile being manipulated (MAYBE NULL)

 * @info: any extra info about the failure (MAYBE NULL)

 * @e: buffer position info (NOT NULL)

 * @error: error code

 *

 * Returns: %0 or error

 */

static int audit_iface(struct aa_profile *new, const char *name,

		       const char *info, struct aa_ext *e, int error)

{

	struct aa_profile *profile = __aa_current_profile();

	struct common_audit_data sa;

	COMMON_AUDIT_DATA_INIT(&sa, NONE);

	sa.aad.iface.pos = e->pos - e->start;

	sa.aad.iface.target = new;

	sa.aad.name = name;

	sa.aad.info = info;

	sa.aad.error = error;

	return aa_audit(AUDIT_APPARMOR_STATUS, profile, GFP_KERNEL, &sa,

			audit_cb);

}

/* test if read will be in packed data bounds */

static bool inbounds(struct aa_ext *e, size_t size)

{

	return (size <= e->end - e->pos);

}

/**

 * aa_u16_chunck - test and do bounds checking for a u16 size based chunk

 * @e: serialized data read head (NOT NULL)

 * @chunk: start address for chunk of data (NOT NULL)

 *

 * Returns: the size of chunk found with the read head at the end of the chunk.

 */

static size_t unpack_u16_chunk(struct aa_ext *e, char **chunk)

{

	size_t size = 0;

	if (!inbounds(e, sizeof(u16)))

		return 0;

	size = le16_to_cpu(get_unaligned((u16 *) e->pos));

	e->pos += sizeof(u16);

	if (!inbounds(e, size))

		return 0;

	*chunk = e->pos;

	e->pos += size;

	return size;

}

/* unpack control byte */

static bool unpack_X(struct aa_ext *e, enum aa_code code)

{

	if (!inbounds(e, 1))

		return 0;

	if (*(u8 *) e->pos != code)

		return 0;

	e->pos++;

	return 1;

}

/**

 * unpack_nameX - check is the next element is of type X with a name of @name

 * @e: serialized data extent information  (NOT NULL)

 * @code: type code

 * @name: name to match to the serialized element.  (MAYBE NULL)

 *

 * check that the next serialized data element is of type X and has a tag

 * name @name.  If @name is specified then there must be a matching

 * name element in the stream.  If @name is NULL any name element will be

 * skipped and only the typecode will be tested.

 *

 * Returns 1 on success (both type code and name tests match) and the read

 * head is advanced past the headers

 *

 * Returns: 0 if either match fails, the read head does not move

 */

static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name)

{

	/*

	 * May need to reset pos if name or type doesn't match

	 */

	void *pos = e->pos;

	/*

	 * Check for presence of a tagname, and if present name size

	 * AA_NAME tag value is a u16.

	 */

	if (unpack_X(e, AA_NAME)) {

		char *tag = NULL;

		size_t size = unpack_u16_chunk(e, &tag);

		/* if a name is specified it must match. otherwise skip tag */

		if (name && (!size || strcmp(name, tag)))

			goto fail;

	} else if (name) {

		/* if a name is specified and there is no name tag fail */

		goto fail;

	}

	/* now check if type code matches */

	if (unpack_X(e, code))

		return 1;

fail:

	e->pos = pos;

	return 0;

}

static bool unpack_u32(struct aa_ext *e, u32 *data, const char *name)

{

	if (unpack_nameX(e, AA_U32, name)) {

		if (!inbounds(e, sizeof(u32)))

			return 0;

		if (data)

			*data = le32_to_cpu(get_unaligned((u32 *) e->pos));

		e->pos += sizeof(u32);

		return 1;

	}

	return 0;

}

static bool unpack_u64(struct aa_ext *e, u64 *data, const char *name)

{

	if (unpack_nameX(e, AA_U64, name)) {

		if (!inbounds(e, sizeof(u64)))

			return 0;

		if (data)

			*data = le64_to_cpu(get_unaligned((u64 *) e->pos));

		e->pos += sizeof(u64);

		return 1;

	}

	return 0;

}

static size_t unpack_array(struct aa_ext *e, const char *name)

{

	if (unpack_nameX(e, AA_ARRAY, name)) {

		int size;

		if (!inbounds(e, sizeof(u16)))

			return 0;

		size = (int)le16_to_cpu(get_unaligned((u16 *) e->pos));

		e->pos += sizeof(u16);

		return size;

	}

	return 0;

}

static size_t unpack_blob(struct aa_ext *e, char **blob, const char *name)

{

	if (unpack_nameX(e, AA_BLOB, name)) {

		u32 size;

		if (!inbounds(e, sizeof(u32)))

			return 0;

		size = le32_to_cpu(get_unaligned((u32 *) e->pos));

		e->pos += sizeof(u32);

		if (inbounds(e, (size_t) size)) {

			*blob = e->pos;

			e->pos += size;

			return size;

		}

	}

	return 0;

}

static int unpack_str(struct aa_ext *e, const char **string, const char *name)

{

	char *src_str;

	size_t size = 0;

	void *pos = e->pos;

	*string = NULL;

	if (unpack_nameX(e, AA_STRING, name)) {

		size = unpack_u16_chunk(e, &src_str);

		if (size) {

			/* strings are null terminated, length is size - 1 */

			if (src_str[size - 1] != 0)

				goto fail;

			*string = src_str;

		}

	}

	return size;

fail:

	e->pos = pos;

	return 0;

}

static int unpack_strdup(struct aa_ext *e, char **string, const char *name)

{

	const char *tmp;

	void *pos = e->pos;

	int res = unpack_str(e, &tmp, name);

	*string = NULL;

	if (!res)

		return 0;

	*string = kmemdup(tmp, res, GFP_KERNEL);

	if (!*string) {

		e->pos = pos;

		return 0;

	}

	return res;

}

/**

 * verify_accept - verify the accept tables of a dfa

 * @dfa: dfa to verify accept tables of (NOT NULL)

 * @flags: flags governing dfa

 *

 * Returns: 1 if valid accept tables else 0 if error

 */

static bool verify_accept(struct aa_dfa *dfa, int flags)

{

	int i;

	/* verify accept permissions */

	for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {

		int mode = ACCEPT_TABLE(dfa)[i];

		if (mode & ~DFA_VALID_PERM_MASK)

			return 0;

		if (ACCEPT_TABLE2(dfa)[i] & ~DFA_VALID_PERM2_MASK)

			return 0;

	}

	return 1;

}

/**

 * unpack_dfa - unpack a file rule dfa

 * @e: serialized data extent information (NOT NULL)

 *

 * returns dfa or ERR_PTR or NULL if no dfa

 */

static struct aa_dfa *unpack_dfa(struct aa_ext *e)

{

	char *blob = NULL;

	size_t size;

	struct aa_dfa *dfa = NULL;

	size = unpack_blob(e, &blob, "aadfa");

	if (size) {

		/*

		 * The dfa is aligned with in the blob to 8 bytes

		 * from the beginning of the stream.

		 */

		size_t sz = blob - (char *)e->start;

		size_t pad = ALIGN(sz, 8) - sz;

		int flags = TO_ACCEPT1_FLAG(YYTD_DATA32) |

			TO_ACCEPT2_FLAG(YYTD_DATA32);

		if (aa_g_paranoid_load)

			flags |= DFA_FLAG_VERIFY_STATES;

		dfa = aa_dfa_unpack(blob + pad, size - pad, flags);

		if (IS_ERR(dfa))

			return dfa;

		if (!verify_accept(dfa, flags))

			goto fail;

	}

	return dfa;

fail:

	aa_put_dfa(dfa);

	return ERR_PTR(-EPROTO);

}

/**

 * unpack_trans_table - unpack a profile transition table

 * @e: serialized data extent information  (NOT NULL)

 * @profile: profile to add the accept table to (NOT NULL)

 *

 * Returns: 1 if table succesfully unpacked

 */

static bool unpack_trans_table(struct aa_ext *e, struct aa_profile *profile)

{

	void *pos = e->pos;

	/* exec table is optional */

	if (unpack_nameX(e, AA_STRUCT, "xtable")) {

		int i, size;

		size = unpack_array(e, NULL);

		/* currently 4 exec bits and entries 0-3 are reserved iupcx */

		if (size > 16 - 4)

			goto fail;

		profile->file.trans.table = kzalloc(sizeof(char *) * size,

						    GFP_KERNEL);

		if (!profile->file.trans.table)

			goto fail;

		profile->file.trans.size = size;

		for (i = 0; i < size; i++) {

			char *str;

			int c, j, size = unpack_strdup(e, &str, NULL);

			/* unpack_strdup verifies that the last character is

			 * null termination byte.

			 */

			if (!size)

				goto fail;

			profile->file.trans.table[i] = str;

			/* verify that name doesn't start with space */

			if (isspace(*str))

				goto fail;

			/* count internal #  of internal \0 */

			for (c = j = 0; j < size - 2; j++) {

				if (!str[j])

					c++;

			}

			if (*str == ':') {

				/* beginning with : requires an embedded \0,

				 * verify that exactly 1 internal \0 exists

				 * trailing \0 already verified by unpack_strdup

				 */

				if (c != 1)

					goto fail;

				/* first character after : must be valid */

				if (!str[1])

					goto fail;

			} else if (c)

				/* fail - all other cases with embedded \0 */

				goto fail;

		}

		if (!unpack_nameX(e, AA_ARRAYEND, NULL))

			goto fail;

		if (!unpack_nameX(e, AA_STRUCTEND, NULL))

			goto fail;

	}

	return 1;

fail:

	aa_free_domain_entries(&profile->file.trans);

	e->pos = pos;

	return 0;

}

static bool unpack_rlimits(struct aa_ext *e, struct aa_profile *profile)

{

	void *pos = e->pos;

	/* rlimits are optional */

	if (unpack_nameX(e, AA_STRUCT, "rlimits")) {

		int i, size;

		u32 tmp = 0;

		if (!unpack_u32(e, &tmp, NULL))

			goto fail;

		profile->rlimits.mask = tmp;

		size = unpack_array(e, NULL);

		if (size > RLIM_NLIMITS)

			goto fail;

		for (i = 0; i < size; i++) {

			u64 tmp = 0;

			int a = aa_map_resource(i);

			if (!unpack_u64(e, &tmp, NULL))

				goto fail;

			profile->rlimits.limits[a].rlim_max = tmp;

		}

		if (!unpack_nameX(e, AA_ARRAYEND, NULL))

			goto fail;

		if (!unpack_nameX(e, AA_STRUCTEND, NULL))

			goto fail;

	}

	return 1;

fail:

	e->pos = pos;

	return 0;

}

/**

 * unpack_profile - unpack a serialized profile

 * @e: serialized data extent information (NOT NULL)

 *

 * NOTE: unpack profile sets audit struct if there is a failure

 */

static struct aa_profile *unpack_profile(struct aa_ext *e)

{

	struct aa_profile *profile = NULL;

	const char *name = NULL;

	int error = -EPROTO;

	kernel_cap_t tmpcap;

	u32 tmp;

	/* check that we have the right struct being passed */

	if (!unpack_nameX(e, AA_STRUCT, "profile"))

		goto fail;

	if (!unpack_str(e, &name, NULL))

		goto fail;

	profile = aa_alloc_profile(name);

	if (!profile)

		return ERR_PTR(-ENOMEM);

	/* profile renaming is optional */

	(void) unpack_str(e, &profile->rename, "rename");

	/* xmatch is optional and may be NULL */

	profile->xmatch = unpack_dfa(e);

	if (IS_ERR(profile->xmatch)) {

		error = PTR_ERR(profile->xmatch);

		profile->xmatch = NULL;

		goto fail;

	}

	/* xmatch_len is not optional if xmatch is set */

	if (profile->xmatch) {

		if (!unpack_u32(e, &tmp, NULL))

			goto fail;

		profile->xmatch_len = tmp;

	}

	/* per profile debug flags (complain, audit) */

	if (!unpack_nameX(e, AA_STRUCT, "flags"))

		goto fail;

	if (!unpack_u32(e, &tmp, NULL))

		goto fail;

	if (tmp)

		profile->flags |= PFLAG_HAT;

	if (!unpack_u32(e, &tmp, NULL))

		goto fail;

	if (tmp)

		profile->mode = APPARMOR_COMPLAIN;

	if (!unpack_u32(e, &tmp, NULL))

		goto fail;

	if (tmp)

		profile->audit = AUDIT_ALL;

	if (!unpack_nameX(e, AA_STRUCTEND, NULL))

		goto fail;

	/* path_flags is optional */

	if (unpack_u32(e, &profile->path_flags, "path_flags"))

		profile->path_flags |= profile->flags & PFLAG_MEDIATE_DELETED;

	else

		/* set a default value if path_flags field is not present */

		profile->path_flags = PFLAG_MEDIATE_DELETED;

	if (!unpack_u32(e, &(profile->caps.allow.cap[0]), NULL))

		goto fail;

	if (!unpack_u32(e, &(profile->caps.audit.cap[0]), NULL))

		goto fail;

	if (!unpack_u32(e, &(profile->caps.quiet.cap[0]), NULL))

		goto fail;

	if (!unpack_u32(e, &tmpcap.cap[0], NULL))

		goto fail;

	if (unpack_nameX(e, AA_STRUCT, "caps64")) {

		/* optional upper half of 64 bit caps */

		if (!unpack_u32(e, &(profile->caps.allow.cap[1]), NULL))

			goto fail;

		if (!unpack_u32(e, &(profile->caps.audit.cap[1]), NULL))

			goto fail;

		if (!unpack_u32(e, &(profile->caps.quiet.cap[1]), NULL))

			goto fail;

		if (!unpack_u32(e, &(tmpcap.cap[1]), NULL))

			goto fail;

		if (!unpack_nameX(e, AA_STRUCTEND, NULL))

			goto fail;

	}

	if (unpack_nameX(e, AA_STRUCT, "capsx")) {

		/* optional extended caps mediation mask */

		if (!unpack_u32(e, &(profile->caps.extended.cap[0]), NULL))

			goto fail;

		if (!unpack_u32(e, &(profile->caps.extended.cap[1]), NULL))

			goto fail;

	}

	if (!unpack_rlimits(e, profile))

		goto fail;

	/* get file rules */

	profile->file.dfa = unpack_dfa(e);

	if (IS_ERR(profile->file.dfa)) {

		error = PTR_ERR(profile->file.dfa);

		profile->file.dfa = NULL;

		goto fail;

	}

	if (!unpack_u32(e, &profile->file.start, "dfa_start"))

		/* default start state */

		profile->file.start = DFA_START;

	if (!unpack_trans_table(e, profile))

		goto fail;

	if (!unpack_nameX(e, AA_STRUCTEND, NULL))

		goto fail;

	return profile;

fail:

	if (profile)

		name = NULL;

	else if (!name)

		name = "unknown";

	audit_iface(profile, name, "failed to unpack profile", e, error);

	aa_put_profile(profile);

	return ERR_PTR(error);

}

/**

 * verify_head - unpack serialized stream header

 * @e: serialized data read head (NOT NULL)

 * @ns: Returns - namespace if one is specified else NULL (NOT NULL)

 *

 * Returns: error or 0 if header is good

 */

static int verify_header(struct aa_ext *e, const char **ns)

{

	int error = -EPROTONOSUPPORT;

	/* get the interface version */

	if (!unpack_u32(e, &e->version, "version")) {

		audit_iface(NULL, NULL, "invalid profile format", e, error);

		return error;

	}

	/* check that the interface version is currently supported */

	if (e->version != 5) {

		audit_iface(NULL, NULL, "unsupported interface version", e,

			    error);

		return error;

	}

	/* read the namespace if present */

	if (!unpack_str(e, ns, "namespace"))

		*ns = NULL;

	return 0;

}

static bool verify_xindex(int xindex, int table_size)

{

	int index, xtype;

	xtype = xindex & AA_X_TYPE_MASK;

	index = xindex & AA_X_INDEX_MASK;

	if (xtype == AA_X_TABLE && index > table_size)

		return 0;

	return 1;

}

/* verify dfa xindexes are in range of transition tables */

static bool verify_dfa_xindex(struct aa_dfa *dfa, int table_size)

{

	int i;

	for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {

		if (!verify_xindex(dfa_user_xindex(dfa, i), table_size))

			return 0;

		if (!verify_xindex(dfa_other_xindex(dfa, i), table_size))

			return 0;

	}

	return 1;

}

/**

 * verify_profile - Do post unpack analysis to verify profile consistency

 * @profile: profile to verify (NOT NULL)

 *

 * Returns: 0 if passes verification else error

 */

static int verify_profile(struct aa_profile *profile)

{

	if (aa_g_paranoid_load) {

		if (profile->file.dfa &&

		    !verify_dfa_xindex(profile->file.dfa,

				       profile->file.trans.size)) {

			audit_iface(profile, NULL, "Invalid named transition",

				    NULL, -EPROTO);

			return -EPROTO;

		}

	}

	return 0;

}

/**

 * aa_unpack - unpack packed binary profile data loaded from user space

 * @udata: user data copied to kmem  (NOT NULL)

 * @size: the size of the user data

 * @ns: Returns namespace profile is in if specified else NULL (NOT NULL)

 *

 * Unpack user data and return refcounted allocated profile or ERR_PTR

 *

 * Returns: profile else error pointer if fails to unpack

 */

struct aa_profile *aa_unpack(void *udata, size_t size, const char **ns)

{