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linux/security/apparmor/policy_unpack.c

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/*
* 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,};
COMMON_AUDIT_DATA_INIT(&sa, 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;
}
/**
* 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;
}
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