security/apparmor/policy_unpack.c

/*
 * 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/security/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
 * @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;
	struct apparmor_audit_data aad = {0,};
	sa.type = LSM_AUDIT_DATA_NONE;
	sa.aad = &aad;
	if (e)
		aad.iface.pos = e->pos - e->start;
	aad.iface.target = new;
	aad.name = name;
	aad.info = info;
	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;
}

#define DFA_VALID_PERM_MASK		0xffffffff
#define DFA_VALID_PERM2_MASK		0xffffffff

/**
 * 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 successfully 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, size2 = unpack_strdup(e, &str, NULL);
			/* unpack_strdup verifies that the last character is
			 * null termination byte.
			 */
			if (!size2)
				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 < size2 - 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 tmp2 = 0;
			int a = aa_map_resource(i);
			if (!unpack_u64(e, &tmp2, NULL))
				goto fail;
			profile->rlimits.limits[a].rlim_max = tmp2;
		}
		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 i, 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_nameX(e, AA_STRUCTEND, NULL))
			goto fail;
	}

	if (!unpack_rlimits(e, profile))
		goto fail;

	if (unpack_nameX(e, AA_STRUCT, "policydb")) {
		/* generic policy dfa - optional and may be NULL */
		profile->policy.dfa = unpack_dfa(e);
		if (IS_ERR(profile->policy.dfa)) {
			error = PTR_ERR(profile->policy.dfa);
			profile->policy.dfa = NULL;
			goto fail;
		}
		if (!unpack_u32(e, &profile->policy.start[0], "start"))
			/* default start state */
			profile->policy.start[0] = DFA_START;
		/* setup class index */
		for (i = AA_CLASS_FILE; i <= AA_CLASS_LAST; i++) {
			profile->policy.start[i] =
				aa_dfa_next(profile->policy.dfa,
					    profile->policy.start[0],
					    i);
		}
		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
			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)
{
	struct aa_profile *profile = NULL;
	int error;
	struct aa_ext e = {
		.start = udata,
		.end = udata + size,
		.pos = udata,
	};

	error = verify_header(&e, ns);
	if (error)
		return ERR_PTR(error);

	profile = unpack_profile(&e);
	if (IS_ERR(profile))
		return profile;

	error = verify_profile(profile);
	if (error) {
		aa_put_profile(profile);
		profile = ERR_PTR(error);
	}

	/* return refcount */
	return profile;
}