linux/security/apparmor/lib.c
Tyler Hicks 7f3ebcf2b1 apparmor: Check buffer bounds when mapping permissions mask
Don't read past the end of the buffer containing permissions
characters or write past the end of the destination string.

Detected by CoverityScan CID#1415361, 1415376 ("Out-of-bounds access")

Fixes: e53cfe6c7c ("apparmor: rework perm mapping to a slightly broader set")
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
2018-07-19 16:24:43 -07:00

528 lines
13 KiB
C

/*
* AppArmor security module
*
* This file contains basic common functions used in AppArmor
*
* 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 <linux/ctype.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include "include/audit.h"
#include "include/apparmor.h"
#include "include/lib.h"
#include "include/perms.h"
#include "include/policy.h"
struct aa_perms nullperms;
struct aa_perms allperms = { .allow = ALL_PERMS_MASK,
.quiet = ALL_PERMS_MASK,
.hide = ALL_PERMS_MASK };
/**
* aa_split_fqname - split a fqname into a profile and namespace name
* @fqname: a full qualified name in namespace profile format (NOT NULL)
* @ns_name: pointer to portion of the string containing the ns name (NOT NULL)
*
* Returns: profile name or NULL if one is not specified
*
* Split a namespace name from a profile name (see policy.c for naming
* description). If a portion of the name is missing it returns NULL for
* that portion.
*
* NOTE: may modify the @fqname string. The pointers returned point
* into the @fqname string.
*/
char *aa_split_fqname(char *fqname, char **ns_name)
{
char *name = strim(fqname);
*ns_name = NULL;
if (name[0] == ':') {
char *split = strchr(&name[1], ':');
*ns_name = skip_spaces(&name[1]);
if (split) {
/* overwrite ':' with \0 */
*split++ = 0;
if (strncmp(split, "//", 2) == 0)
split += 2;
name = skip_spaces(split);
} else
/* a ns name without a following profile is allowed */
name = NULL;
}
if (name && *name == 0)
name = NULL;
return name;
}
/**
* skipn_spaces - Removes leading whitespace from @str.
* @str: The string to be stripped.
*
* Returns a pointer to the first non-whitespace character in @str.
* if all whitespace will return NULL
*/
const char *skipn_spaces(const char *str, size_t n)
{
for (; n && isspace(*str); --n)
++str;
if (n)
return (char *)str;
return NULL;
}
const char *aa_splitn_fqname(const char *fqname, size_t n, const char **ns_name,
size_t *ns_len)
{
const char *end = fqname + n;
const char *name = skipn_spaces(fqname, n);
if (!name)
return NULL;
*ns_name = NULL;
*ns_len = 0;
if (name[0] == ':') {
char *split = strnchr(&name[1], end - &name[1], ':');
*ns_name = skipn_spaces(&name[1], end - &name[1]);
if (!*ns_name)
return NULL;
if (split) {
*ns_len = split - *ns_name;
if (*ns_len == 0)
*ns_name = NULL;
split++;
if (end - split > 1 && strncmp(split, "//", 2) == 0)
split += 2;
name = skipn_spaces(split, end - split);
} else {
/* a ns name without a following profile is allowed */
name = NULL;
*ns_len = end - *ns_name;
}
}
if (name && *name == 0)
name = NULL;
return name;
}
/**
* aa_info_message - log a none profile related status message
* @str: message to log
*/
void aa_info_message(const char *str)
{
if (audit_enabled) {
DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, NULL);
aad(&sa)->info = str;
aa_audit_msg(AUDIT_APPARMOR_STATUS, &sa, NULL);
}
printk(KERN_INFO "AppArmor: %s\n", str);
}
__counted char *aa_str_alloc(int size, gfp_t gfp)
{
struct counted_str *str;
str = kmalloc(sizeof(struct counted_str) + size, gfp);
if (!str)
return NULL;
kref_init(&str->count);
return str->name;
}
void aa_str_kref(struct kref *kref)
{
kfree(container_of(kref, struct counted_str, count));
}
const char aa_file_perm_chrs[] = "xwracd km l ";
const char *aa_file_perm_names[] = {
"exec",
"write",
"read",
"append",
"create",
"delete",
"open",
"rename",
"setattr",
"getattr",
"setcred",
"getcred",
"chmod",
"chown",
"chgrp",
"lock",
"mmap",
"mprot",
"link",
"snapshot",
"unknown",
"unknown",
"unknown",
"unknown",
"unknown",
"unknown",
"unknown",
"unknown",
"stack",
"change_onexec",
"change_profile",
"change_hat",
};
/**
* aa_perm_mask_to_str - convert a perm mask to its short string
* @str: character buffer to store string in (at least 10 characters)
* @str_size: size of the @str buffer
* @chrs: NUL-terminated character buffer of permission characters
* @mask: permission mask to convert
*/
void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs, u32 mask)
{
unsigned int i, perm = 1;
size_t num_chrs = strlen(chrs);
for (i = 0; i < num_chrs; perm <<= 1, i++) {
if (mask & perm) {
/* Ensure that one byte is left for NUL-termination */
if (WARN_ON_ONCE(str_size <= 1))
break;
*str++ = chrs[i];
str_size--;
}
}
*str = '\0';
}
void aa_audit_perm_names(struct audit_buffer *ab, const char * const *names,
u32 mask)
{
const char *fmt = "%s";
unsigned int i, perm = 1;
bool prev = false;
for (i = 0; i < 32; perm <<= 1, i++) {
if (mask & perm) {
audit_log_format(ab, fmt, names[i]);
if (!prev) {
prev = true;
fmt = " %s";
}
}
}
}
void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
u32 chrsmask, const char * const *names, u32 namesmask)
{
char str[33];
audit_log_format(ab, "\"");
if ((mask & chrsmask) && chrs) {
aa_perm_mask_to_str(str, sizeof(str), chrs, mask & chrsmask);
mask &= ~chrsmask;
audit_log_format(ab, "%s", str);
if (mask & namesmask)
audit_log_format(ab, " ");
}
if ((mask & namesmask) && names)
aa_audit_perm_names(ab, names, mask & namesmask);
audit_log_format(ab, "\"");
}
/**
* aa_audit_perms_cb - generic callback fn for auditing perms
* @ab: audit buffer (NOT NULL)
* @va: audit struct to audit values of (NOT NULL)
*/
static void aa_audit_perms_cb(struct audit_buffer *ab, void *va)
{
struct common_audit_data *sa = va;
if (aad(sa)->request) {
audit_log_format(ab, " requested_mask=");
aa_audit_perm_mask(ab, aad(sa)->request, aa_file_perm_chrs,
PERMS_CHRS_MASK, aa_file_perm_names,
PERMS_NAMES_MASK);
}
if (aad(sa)->denied) {
audit_log_format(ab, "denied_mask=");
aa_audit_perm_mask(ab, aad(sa)->denied, aa_file_perm_chrs,
PERMS_CHRS_MASK, aa_file_perm_names,
PERMS_NAMES_MASK);
}
audit_log_format(ab, " peer=");
aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
FLAGS_NONE, GFP_ATOMIC);
}
/**
* aa_apply_modes_to_perms - apply namespace and profile flags to perms
* @profile: that perms where computed from
* @perms: perms to apply mode modifiers to
*
* TODO: split into profile and ns based flags for when accumulating perms
*/
void aa_apply_modes_to_perms(struct aa_profile *profile, struct aa_perms *perms)
{
switch (AUDIT_MODE(profile)) {
case AUDIT_ALL:
perms->audit = ALL_PERMS_MASK;
/* fall through */
case AUDIT_NOQUIET:
perms->quiet = 0;
break;
case AUDIT_QUIET:
perms->audit = 0;
/* fall through */
case AUDIT_QUIET_DENIED:
perms->quiet = ALL_PERMS_MASK;
break;
}
if (KILL_MODE(profile))
perms->kill = ALL_PERMS_MASK;
else if (COMPLAIN_MODE(profile))
perms->complain = ALL_PERMS_MASK;
/*
* TODO:
* else if (PROMPT_MODE(profile))
* perms->prompt = ALL_PERMS_MASK;
*/
}
static u32 map_other(u32 x)
{
return ((x & 0x3) << 8) | /* SETATTR/GETATTR */
((x & 0x1c) << 18) | /* ACCEPT/BIND/LISTEN */
((x & 0x60) << 19); /* SETOPT/GETOPT */
}
void aa_compute_perms(struct aa_dfa *dfa, unsigned int state,
struct aa_perms *perms)
{
*perms = (struct aa_perms) {
.allow = dfa_user_allow(dfa, state),
.audit = dfa_user_audit(dfa, state),
.quiet = dfa_user_quiet(dfa, state),
};
/* for v5 perm mapping in the policydb, the other set is used
* to extend the general perm set
*/
perms->allow |= map_other(dfa_other_allow(dfa, state));
perms->audit |= map_other(dfa_other_audit(dfa, state));
perms->quiet |= map_other(dfa_other_quiet(dfa, state));
// perms->xindex = dfa_user_xindex(dfa, state);
}
/**
* aa_perms_accum_raw - accumulate perms with out masking off overlapping perms
* @accum - perms struct to accumulate into
* @addend - perms struct to add to @accum
*/
void aa_perms_accum_raw(struct aa_perms *accum, struct aa_perms *addend)
{
accum->deny |= addend->deny;
accum->allow &= addend->allow & ~addend->deny;
accum->audit |= addend->audit & addend->allow;
accum->quiet &= addend->quiet & ~addend->allow;
accum->kill |= addend->kill & ~addend->allow;
accum->stop |= addend->stop & ~addend->allow;
accum->complain |= addend->complain & ~addend->allow & ~addend->deny;
accum->cond |= addend->cond & ~addend->allow & ~addend->deny;
accum->hide &= addend->hide & ~addend->allow;
accum->prompt |= addend->prompt & ~addend->allow & ~addend->deny;
}
/**
* aa_perms_accum - accumulate perms, masking off overlapping perms
* @accum - perms struct to accumulate into
* @addend - perms struct to add to @accum
*/
void aa_perms_accum(struct aa_perms *accum, struct aa_perms *addend)
{
accum->deny |= addend->deny;
accum->allow &= addend->allow & ~accum->deny;
accum->audit |= addend->audit & accum->allow;
accum->quiet &= addend->quiet & ~accum->allow;
accum->kill |= addend->kill & ~accum->allow;
accum->stop |= addend->stop & ~accum->allow;
accum->complain |= addend->complain & ~accum->allow & ~accum->deny;
accum->cond |= addend->cond & ~accum->allow & ~accum->deny;
accum->hide &= addend->hide & ~accum->allow;
accum->prompt |= addend->prompt & ~accum->allow & ~accum->deny;
}
void aa_profile_match_label(struct aa_profile *profile, struct aa_label *label,
int type, u32 request, struct aa_perms *perms)
{
/* TODO: doesn't yet handle extended types */
unsigned int state;
state = aa_dfa_next(profile->policy.dfa,
profile->policy.start[AA_CLASS_LABEL],
type);
aa_label_match(profile, label, state, false, request, perms);
}
/* currently unused */
int aa_profile_label_perm(struct aa_profile *profile, struct aa_profile *target,
u32 request, int type, u32 *deny,
struct common_audit_data *sa)
{
struct aa_perms perms;
aad(sa)->label = &profile->label;
aad(sa)->peer = &target->label;
aad(sa)->request = request;
aa_profile_match_label(profile, &target->label, type, request, &perms);
aa_apply_modes_to_perms(profile, &perms);
*deny |= request & perms.deny;
return aa_check_perms(profile, &perms, request, sa, aa_audit_perms_cb);
}
/**
* aa_check_perms - do audit mode selection based on perms set
* @profile: profile being checked
* @perms: perms computed for the request
* @request: requested perms
* @deny: Returns: explicit deny set
* @sa: initialized audit structure (MAY BE NULL if not auditing)
* @cb: callback fn for type specific fields (MAY BE NULL)
*
* Returns: 0 if permission else error code
*
* Note: profile audit modes need to be set before calling by setting the
* perm masks appropriately.
*
* If not auditing then complain mode is not enabled and the
* error code will indicate whether there was an explicit deny
* with a positive value.
*/
int aa_check_perms(struct aa_profile *profile, struct aa_perms *perms,
u32 request, struct common_audit_data *sa,
void (*cb)(struct audit_buffer *, void *))
{
int type, error;
u32 denied = request & (~perms->allow | perms->deny);
if (likely(!denied)) {
/* mask off perms that are not being force audited */
request &= perms->audit;
if (!request || !sa)
return 0;
type = AUDIT_APPARMOR_AUDIT;
error = 0;
} else {
error = -EACCES;
if (denied & perms->kill)
type = AUDIT_APPARMOR_KILL;
else if (denied == (denied & perms->complain))
type = AUDIT_APPARMOR_ALLOWED;
else
type = AUDIT_APPARMOR_DENIED;
if (denied == (denied & perms->hide))
error = -ENOENT;
denied &= ~perms->quiet;
if (!sa || !denied)
return error;
}
if (sa) {
aad(sa)->label = &profile->label;
aad(sa)->request = request;
aad(sa)->denied = denied;
aad(sa)->error = error;
aa_audit_msg(type, sa, cb);
}
if (type == AUDIT_APPARMOR_ALLOWED)
error = 0;
return error;
}
/**
* aa_policy_init - initialize a policy structure
* @policy: policy to initialize (NOT NULL)
* @prefix: prefix name if any is required. (MAYBE NULL)
* @name: name of the policy, init will make a copy of it (NOT NULL)
* @gfp: allocation mode
*
* Note: this fn creates a copy of strings passed in
*
* Returns: true if policy init successful
*/
bool aa_policy_init(struct aa_policy *policy, const char *prefix,
const char *name, gfp_t gfp)
{
char *hname;
/* freed by policy_free */
if (prefix) {
hname = aa_str_alloc(strlen(prefix) + strlen(name) + 3, gfp);
if (hname)
sprintf(hname, "%s//%s", prefix, name);
} else {
hname = aa_str_alloc(strlen(name) + 1, gfp);
if (hname)
strcpy(hname, name);
}
if (!hname)
return false;
policy->hname = hname;
/* base.name is a substring of fqname */
policy->name = basename(policy->hname);
INIT_LIST_HEAD(&policy->list);
INIT_LIST_HEAD(&policy->profiles);
return true;
}
/**
* aa_policy_destroy - free the elements referenced by @policy
* @policy: policy that is to have its elements freed (NOT NULL)
*/
void aa_policy_destroy(struct aa_policy *policy)
{
AA_BUG(on_list_rcu(&policy->profiles));
AA_BUG(on_list_rcu(&policy->list));
/* don't free name as its a subset of hname */
aa_put_str(policy->hname);
}