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linux/kernel/auditfilter.c

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/* auditfilter.c -- filtering of audit events
*
* Copyright 2003-2004 Red Hat, Inc.
* Copyright 2005 Hewlett-Packard Development Company, L.P.
* Copyright 2005 IBM Corporation
*
* 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; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/kernel.h>
#include <linux/audit.h>
#include <linux/kthread.h>
#include <linux/netlink.h>
#include "audit.h"
/* There are three lists of rules -- one to search at task creation
* time, one to search at syscall entry time, and another to search at
* syscall exit time. */
struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
LIST_HEAD_INIT(audit_filter_list[0]),
LIST_HEAD_INIT(audit_filter_list[1]),
LIST_HEAD_INIT(audit_filter_list[2]),
LIST_HEAD_INIT(audit_filter_list[3]),
LIST_HEAD_INIT(audit_filter_list[4]),
LIST_HEAD_INIT(audit_filter_list[5]),
#if AUDIT_NR_FILTERS != 6
#error Fix audit_filter_list initialiser
#endif
};
static inline void audit_free_rule(struct audit_entry *e)
{
kfree(e->rule.fields);
kfree(e);
}
static inline void audit_free_rule_rcu(struct rcu_head *head)
{
struct audit_entry *e = container_of(head, struct audit_entry, rcu);
audit_free_rule(e);
}
/* Unpack a filter field's string representation from user-space
* buffer. */
static __attribute__((unused)) char *audit_unpack_string(void **bufp, size_t *remain, size_t len)
{
char *str;
if (!*bufp || (len == 0) || (len > *remain))
return ERR_PTR(-EINVAL);
/* Of the currently implemented string fields, PATH_MAX
* defines the longest valid length.
*/
if (len > PATH_MAX)
return ERR_PTR(-ENAMETOOLONG);
str = kmalloc(len + 1, GFP_KERNEL);
if (unlikely(!str))
return ERR_PTR(-ENOMEM);
memcpy(str, *bufp, len);
str[len] = 0;
*bufp += len;
*remain -= len;
return str;
}
/* Common user-space to kernel rule translation. */
static inline struct audit_entry *audit_to_entry_common(struct audit_rule *rule)
{
unsigned listnr;
struct audit_entry *entry;
struct audit_field *fields;
int i, err;
err = -EINVAL;
listnr = rule->flags & ~AUDIT_FILTER_PREPEND;
switch(listnr) {
default:
goto exit_err;
case AUDIT_FILTER_USER:
case AUDIT_FILTER_TYPE:
#ifdef CONFIG_AUDITSYSCALL
case AUDIT_FILTER_ENTRY:
case AUDIT_FILTER_EXIT:
case AUDIT_FILTER_TASK:
#endif
;
}
if (rule->action != AUDIT_NEVER && rule->action != AUDIT_POSSIBLE &&
rule->action != AUDIT_ALWAYS)
goto exit_err;
if (rule->field_count > AUDIT_MAX_FIELDS)
goto exit_err;
err = -ENOMEM;
entry = kmalloc(sizeof(*entry), GFP_KERNEL);
if (unlikely(!entry))
goto exit_err;
fields = kmalloc(sizeof(*fields) * rule->field_count, GFP_KERNEL);
if (unlikely(!fields)) {
kfree(entry);
goto exit_err;
}
memset(&entry->rule, 0, sizeof(struct audit_krule));
memset(fields, 0, sizeof(struct audit_field));
entry->rule.flags = rule->flags & AUDIT_FILTER_PREPEND;
entry->rule.listnr = listnr;
entry->rule.action = rule->action;
entry->rule.field_count = rule->field_count;
entry->rule.fields = fields;
for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
entry->rule.mask[i] = rule->mask[i];
return entry;
exit_err:
return ERR_PTR(err);
}
/* Translate struct audit_rule to kernel's rule respresentation.
* Exists for backward compatibility with userspace. */
static struct audit_entry *audit_rule_to_entry(struct audit_rule *rule)
{
struct audit_entry *entry;
int err = 0;
int i;
entry = audit_to_entry_common(rule);
if (IS_ERR(entry))
goto exit_nofree;
for (i = 0; i < rule->field_count; i++) {
struct audit_field *f = &entry->rule.fields[i];
if (rule->fields[i] & AUDIT_UNUSED_BITS) {
err = -EINVAL;
goto exit_free;
}
f->op = rule->fields[i] & (AUDIT_NEGATE|AUDIT_OPERATORS);
f->type = rule->fields[i] & ~(AUDIT_NEGATE|AUDIT_OPERATORS);
f->val = rule->values[i];
entry->rule.vers_ops = (f->op & AUDIT_OPERATORS) ? 2 : 1;
/* Support for legacy operators where
* AUDIT_NEGATE bit signifies != and otherwise assumes == */
if (f->op & AUDIT_NEGATE)
f->op = AUDIT_NOT_EQUAL;
else if (!f->op)
f->op = AUDIT_EQUAL;
else if (f->op == AUDIT_OPERATORS) {
err = -EINVAL;
goto exit_free;
}
}
exit_nofree:
return entry;
exit_free:
audit_free_rule(entry);
return ERR_PTR(err);
}
/* Translate struct audit_rule_data to kernel's rule respresentation. */
static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
size_t datasz)
{
int err = 0;
struct audit_entry *entry;
void *bufp;
/* size_t remain = datasz - sizeof(struct audit_rule_data); */
int i;
entry = audit_to_entry_common((struct audit_rule *)data);
if (IS_ERR(entry))
goto exit_nofree;
bufp = data->buf;
entry->rule.vers_ops = 2;
for (i = 0; i < data->field_count; i++) {
struct audit_field *f = &entry->rule.fields[i];
err = -EINVAL;
if (!(data->fieldflags[i] & AUDIT_OPERATORS) ||
data->fieldflags[i] & ~AUDIT_OPERATORS)
goto exit_free;
f->op = data->fieldflags[i] & AUDIT_OPERATORS;
f->type = data->fields[i];
switch(f->type) {
/* call type-specific conversion routines here */
default:
f->val = data->values[i];
}
}
exit_nofree:
return entry;
exit_free:
audit_free_rule(entry);
return ERR_PTR(err);
}
/* Pack a filter field's string representation into data block. */
static inline size_t audit_pack_string(void **bufp, char *str)
{
size_t len = strlen(str);
memcpy(*bufp, str, len);
*bufp += len;
return len;
}
/* Translate kernel rule respresentation to struct audit_rule.
* Exists for backward compatibility with userspace. */
static struct audit_rule *audit_krule_to_rule(struct audit_krule *krule)
{
struct audit_rule *rule;
int i;
rule = kmalloc(sizeof(*rule), GFP_KERNEL);
if (unlikely(!rule))
return ERR_PTR(-ENOMEM);
memset(rule, 0, sizeof(*rule));
rule->flags = krule->flags | krule->listnr;
rule->action = krule->action;
rule->field_count = krule->field_count;
for (i = 0; i < rule->field_count; i++) {
rule->values[i] = krule->fields[i].val;
rule->fields[i] = krule->fields[i].type;
if (krule->vers_ops == 1) {
if (krule->fields[i].op & AUDIT_NOT_EQUAL)
rule->fields[i] |= AUDIT_NEGATE;
} else {
rule->fields[i] |= krule->fields[i].op;
}
}
for (i = 0; i < AUDIT_BITMASK_SIZE; i++) rule->mask[i] = krule->mask[i];
return rule;
}
/* Translate kernel rule respresentation to struct audit_rule_data. */
static struct audit_rule_data *audit_krule_to_data(struct audit_krule *krule)
{
struct audit_rule_data *data;
void *bufp;
int i;
data = kmalloc(sizeof(*data) + krule->buflen, GFP_KERNEL);
if (unlikely(!data))
return ERR_PTR(-ENOMEM);
memset(data, 0, sizeof(*data));
data->flags = krule->flags | krule->listnr;
data->action = krule->action;
data->field_count = krule->field_count;
bufp = data->buf;
for (i = 0; i < data->field_count; i++) {
struct audit_field *f = &krule->fields[i];
data->fields[i] = f->type;
data->fieldflags[i] = f->op;
switch(f->type) {
/* call type-specific conversion routines here */
default:
data->values[i] = f->val;
}
}
for (i = 0; i < AUDIT_BITMASK_SIZE; i++) data->mask[i] = krule->mask[i];
return data;
}
/* Compare two rules in kernel format. Considered success if rules
* don't match. */
static int audit_compare_rule(struct audit_krule *a, struct audit_krule *b)
{
int i;
if (a->flags != b->flags ||
a->listnr != b->listnr ||
a->action != b->action ||
a->field_count != b->field_count)
return 1;
for (i = 0; i < a->field_count; i++) {
if (a->fields[i].type != b->fields[i].type ||
a->fields[i].op != b->fields[i].op)
return 1;
switch(a->fields[i].type) {
/* call type-specific comparison routines here */
default:
if (a->fields[i].val != b->fields[i].val)
return 1;
}
}
for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
if (a->mask[i] != b->mask[i])
return 1;
return 0;
}
/* Add rule to given filterlist if not a duplicate. Protected by
* audit_netlink_mutex. */
static inline int audit_add_rule(struct audit_entry *entry,
struct list_head *list)
{
struct audit_entry *e;
/* Do not use the _rcu iterator here, since this is the only
* addition routine. */
list_for_each_entry(e, list, list) {
if (!audit_compare_rule(&entry->rule, &e->rule))
return -EEXIST;
}
if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
list_add_rcu(&entry->list, list);
} else {
list_add_tail_rcu(&entry->list, list);
}
return 0;
}
/* Remove an existing rule from filterlist. Protected by
* audit_netlink_mutex. */
static inline int audit_del_rule(struct audit_entry *entry,
struct list_head *list)
{
struct audit_entry *e;
/* Do not use the _rcu iterator here, since this is the only
* deletion routine. */
list_for_each_entry(e, list, list) {
if (!audit_compare_rule(&entry->rule, &e->rule)) {
list_del_rcu(&e->list);
call_rcu(&e->rcu, audit_free_rule_rcu);
return 0;
}
}
return -ENOENT; /* No matching rule */
}
/* List rules using struct audit_rule. Exists for backward
* compatibility with userspace. */
static int audit_list(void *_dest)
{
int pid, seq;
int *dest = _dest;
struct audit_entry *entry;
int i;
pid = dest[0];
seq = dest[1];
kfree(dest);
mutex_lock(&audit_netlink_mutex);
/* The *_rcu iterators not needed here because we are
always called with audit_netlink_mutex held. */
for (i=0; i<AUDIT_NR_FILTERS; i++) {
list_for_each_entry(entry, &audit_filter_list[i], list) {
struct audit_rule *rule;
rule = audit_krule_to_rule(&entry->rule);
if (unlikely(!rule))
break;
audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
rule, sizeof(*rule));
kfree(rule);
}
}
audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0);
mutex_unlock(&audit_netlink_mutex);
return 0;
}
/* List rules using struct audit_rule_data. */
static int audit_list_rules(void *_dest)
{
int pid, seq;
int *dest = _dest;
struct audit_entry *e;
int i;
pid = dest[0];
seq = dest[1];
kfree(dest);
mutex_lock(&audit_netlink_mutex);
/* The *_rcu iterators not needed here because we are
always called with audit_netlink_mutex held. */
for (i=0; i<AUDIT_NR_FILTERS; i++) {
list_for_each_entry(e, &audit_filter_list[i], list) {
struct audit_rule_data *data;
data = audit_krule_to_data(&e->rule);
if (unlikely(!data))
break;
audit_send_reply(pid, seq, AUDIT_LIST_RULES, 0, 1,
data, sizeof(*data));
kfree(data);
}
}
audit_send_reply(pid, seq, AUDIT_LIST_RULES, 1, 1, NULL, 0);
mutex_unlock(&audit_netlink_mutex);
return 0;
}
/**
* audit_receive_filter - apply all rules to the specified message type
* @type: audit message type
* @pid: target pid for netlink audit messages
* @uid: target uid for netlink audit messages
* @seq: netlink audit message sequence (serial) number
* @data: payload data
* @datasz: size of payload data
* @loginuid: loginuid of sender
*/
int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
size_t datasz, uid_t loginuid)
{
struct task_struct *tsk;
int *dest;
int err = 0;
struct audit_entry *entry;
switch (type) {
case AUDIT_LIST:
case AUDIT_LIST_RULES:
/* We can't just spew out the rules here because we might fill
* the available socket buffer space and deadlock waiting for
* auditctl to read from it... which isn't ever going to
* happen if we're actually running in the context of auditctl
* trying to _send_ the stuff */
dest = kmalloc(2 * sizeof(int), GFP_KERNEL);
if (!dest)
return -ENOMEM;
dest[0] = pid;
dest[1] = seq;
if (type == AUDIT_LIST)
tsk = kthread_run(audit_list, dest, "audit_list");
else
tsk = kthread_run(audit_list_rules, dest,
"audit_list_rules");
if (IS_ERR(tsk)) {
kfree(dest);
err = PTR_ERR(tsk);
}
break;
case AUDIT_ADD:
case AUDIT_ADD_RULE:
if (type == AUDIT_ADD)
entry = audit_rule_to_entry(data);
else
entry = audit_data_to_entry(data, datasz);
if (IS_ERR(entry))
return PTR_ERR(entry);
err = audit_add_rule(entry,
&audit_filter_list[entry->rule.listnr]);
audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
"auid=%u add rule to list=%d res=%d\n",
loginuid, entry->rule.listnr, !err);
if (err)
audit_free_rule(entry);
break;
case AUDIT_DEL:
case AUDIT_DEL_RULE:
if (type == AUDIT_DEL)
entry = audit_rule_to_entry(data);
else
entry = audit_data_to_entry(data, datasz);
if (IS_ERR(entry))
return PTR_ERR(entry);
err = audit_del_rule(entry,
&audit_filter_list[entry->rule.listnr]);
audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
"auid=%u remove rule from list=%d res=%d\n",
loginuid, entry->rule.listnr, !err);
audit_free_rule(entry);
break;
default:
return -EINVAL;
}
return err;
}
int audit_comparator(const u32 left, const u32 op, const u32 right)
{
switch (op) {
case AUDIT_EQUAL:
return (left == right);
case AUDIT_NOT_EQUAL:
return (left != right);
case AUDIT_LESS_THAN:
return (left < right);
case AUDIT_LESS_THAN_OR_EQUAL:
return (left <= right);
case AUDIT_GREATER_THAN:
return (left > right);
case AUDIT_GREATER_THAN_OR_EQUAL:
return (left >= right);
}
BUG();
return 0;
}
static int audit_filter_user_rules(struct netlink_skb_parms *cb,
struct audit_krule *rule,
enum audit_state *state)
{
int i;
for (i = 0; i < rule->field_count; i++) {
struct audit_field *f = &rule->fields[i];
int result = 0;
switch (f->type) {
case AUDIT_PID:
result = audit_comparator(cb->creds.pid, f->op, f->val);
break;
case AUDIT_UID:
result = audit_comparator(cb->creds.uid, f->op, f->val);
break;
case AUDIT_GID:
result = audit_comparator(cb->creds.gid, f->op, f->val);
break;
case AUDIT_LOGINUID:
result = audit_comparator(cb->loginuid, f->op, f->val);
break;
}
if (!result)
return 0;
}
switch (rule->action) {
case AUDIT_NEVER: *state = AUDIT_DISABLED; break;
case AUDIT_POSSIBLE: *state = AUDIT_BUILD_CONTEXT; break;
case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break;
}
return 1;
}
int audit_filter_user(struct netlink_skb_parms *cb, int type)
{
struct audit_entry *e;
enum audit_state state;
int ret = 1;
rcu_read_lock();
list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
if (audit_filter_user_rules(cb, &e->rule, &state)) {
if (state == AUDIT_DISABLED)
ret = 0;
break;
}
}
rcu_read_unlock();
return ret; /* Audit by default */
}
int audit_filter_type(int type)
{
struct audit_entry *e;
int result = 0;
rcu_read_lock();
if (list_empty(&audit_filter_list[AUDIT_FILTER_TYPE]))
goto unlock_and_return;
list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TYPE],
list) {
int i;
for (i = 0; i < e->rule.field_count; i++) {
struct audit_field *f = &e->rule.fields[i];
if (f->type == AUDIT_MSGTYPE) {
result = audit_comparator(type, f->op, f->val);
if (!result)
break;
}
}
if (result)
goto unlock_and_return;
}
unlock_and_return:
rcu_read_unlock();
return result;
}
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