auditfilter.c

来自「Kernel code of linux kernel」· C语言 代码 · 共 1,851 行 · 第 1/4 页

				 * list.  Grab a reference before releasing
				 * audit_filter_mutex, to be released in
				 * audit_inotify_unregister(). */
				list_add(&parent->ilist, &inotify_list);
				get_inotify_watch(&parent->wdata);
			}
		}
	}

	if (e->rule.tree)
		audit_remove_tree_rule(&e->rule);

	list_del_rcu(&e->list);
	call_rcu(&e->rcu, audit_free_rule_rcu);

#ifdef CONFIG_AUDITSYSCALL
	if (!dont_count)
		audit_n_rules--;

	if (!audit_match_signal(entry))
		audit_signals--;
#endif
	mutex_unlock(&audit_filter_mutex);

	if (!list_empty(&inotify_list))
		audit_inotify_unregister(&inotify_list);

out:
	if (tmp_watch)
		audit_put_watch(tmp_watch); /* match initial get */
	if (tree)
		audit_put_tree(tree);	/* that's the temporary one */

	return ret;
}

/* List rules using struct audit_rule.  Exists for backward
 * compatibility with userspace. */
static void audit_list(int pid, int seq, struct sk_buff_head *q)
{
	struct sk_buff *skb;
	struct audit_entry *entry;
	int i;

	/* This is a blocking read, so use audit_filter_mutex instead of rcu
	 * iterator to sync with list writers. */
	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;
			skb = audit_make_reply(pid, seq, AUDIT_LIST, 0, 1,
					 rule, sizeof(*rule));
			if (skb)
				skb_queue_tail(q, skb);
			kfree(rule);
		}
	}
	for (i = 0; i < AUDIT_INODE_BUCKETS; i++) {
		list_for_each_entry(entry, &audit_inode_hash[i], list) {
			struct audit_rule *rule;

			rule = audit_krule_to_rule(&entry->rule);
			if (unlikely(!rule))
				break;
			skb = audit_make_reply(pid, seq, AUDIT_LIST, 0, 1,
					 rule, sizeof(*rule));
			if (skb)
				skb_queue_tail(q, skb);
			kfree(rule);
		}
	}
	skb = audit_make_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0);
	if (skb)
		skb_queue_tail(q, skb);
}

/* List rules using struct audit_rule_data. */
static void audit_list_rules(int pid, int seq, struct sk_buff_head *q)
{
	struct sk_buff *skb;
	struct audit_entry *e;
	int i;

	/* This is a blocking read, so use audit_filter_mutex instead of rcu
	 * iterator to sync with list writers. */
	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;
			skb = audit_make_reply(pid, seq, AUDIT_LIST_RULES, 0, 1,
					 data, sizeof(*data) + data->buflen);
			if (skb)
				skb_queue_tail(q, skb);
			kfree(data);
		}
	}
	for (i=0; i< AUDIT_INODE_BUCKETS; i++) {
		list_for_each_entry(e, &audit_inode_hash[i], list) {
			struct audit_rule_data *data;

			data = audit_krule_to_data(&e->rule);
			if (unlikely(!data))
				break;
			skb = audit_make_reply(pid, seq, AUDIT_LIST_RULES, 0, 1,
					 data, sizeof(*data) + data->buflen);
			if (skb)
				skb_queue_tail(q, skb);
			kfree(data);
		}
	}
	skb = audit_make_reply(pid, seq, AUDIT_LIST_RULES, 1, 1, NULL, 0);
	if (skb)
		skb_queue_tail(q, skb);
}

/* Log rule additions and removals */
static void audit_log_rule_change(uid_t loginuid, u32 sessionid, u32 sid,
				  char *action, struct audit_krule *rule,
				  int res)
{
	struct audit_buffer *ab;

	if (!audit_enabled)
		return;

	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
	if (!ab)
		return;
	audit_log_format(ab, "auid=%u ses=%u", loginuid, sessionid);
	if (sid) {
		char *ctx = NULL;
		u32 len;
		if (security_secid_to_secctx(sid, &ctx, &len))
			audit_log_format(ab, " ssid=%u", sid);
		else {
			audit_log_format(ab, " subj=%s", ctx);
			security_release_secctx(ctx, len);
		}
	}
	audit_log_format(ab, " op=%s rule key=", action);
	if (rule->filterkey)
		audit_log_untrustedstring(ab, rule->filterkey);
	else
		audit_log_format(ab, "(null)");
	audit_log_format(ab, " list=%d res=%d", rule->listnr, res);
	audit_log_end(ab);
}

/**
 * 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
 * @sessionid: sessionid for netlink audit message
 * @sid: SE Linux Security ID of sender
 */
int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
			 size_t datasz, uid_t loginuid, u32 sessionid, u32 sid)
{
	struct task_struct *tsk;
	struct audit_netlink_list *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(sizeof(struct audit_netlink_list), GFP_KERNEL);
		if (!dest)
			return -ENOMEM;
		dest->pid = pid;
		skb_queue_head_init(&dest->q);

		mutex_lock(&audit_filter_mutex);
		if (type == AUDIT_LIST)
			audit_list(pid, seq, &dest->q);
		else
			audit_list_rules(pid, seq, &dest->q);
		mutex_unlock(&audit_filter_mutex);

		tsk = kthread_run(audit_send_list, dest, "audit_send_list");
		if (IS_ERR(tsk)) {
			skb_queue_purge(&dest->q);
			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_rule_change(loginuid, sessionid, sid, "add",
				      &entry->rule, !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_rule_change(loginuid, sessionid, sid, "remove",
				      &entry->rule, !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);
	case AUDIT_BIT_MASK:
		return (left & right);
	case AUDIT_BIT_TEST:
		return ((left & right) == right);
	}
	BUG();
	return 0;
}

/* Compare given dentry name with last component in given path,
 * return of 0 indicates a match. */
int audit_compare_dname_path(const char *dname, const char *path,
			     int *dirlen)
{
	int dlen, plen;
	const char *p;

	if (!dname || !path)
		return 1;

	dlen = strlen(dname);
	plen = strlen(path);
	if (plen < dlen)
		return 1;

	/* disregard trailing slashes */
	p = path + plen - 1;
	while ((*p == '/') && (p > path))
		p--;

	/* find last path component */
	p = p - dlen + 1;
	if (p < path)
		return 1;
	else if (p > path) {
		if (*--p != '/')
			return 1;
		else
			p++;
	}

	/* return length of path's directory component */
	if (dirlen)
		*dirlen = p - path;
	return strncmp(p, dname, dlen);
}

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_ALWAYS:   *state = AUDIT_RECORD_CONTEXT; break;
	}
	return 1;
}

int audit_filter_user(struct netlink_skb_parms *cb)
{
	enum audit_state state = AUDIT_DISABLED;
	struct audit_entry *e;
	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;
}

/* This function will re-initialize the lsm_rule field of all applicable rules.
 * It will traverse the filter lists serarching for rules that contain LSM
 * specific filter fields.  When such a rule is found, it is copied, the
 * LSM field is re-initialized, and the old rule is replaced with the
 * updated rule. */
int audit_update_lsm_rules(void)
{
	struct audit_entry *entry, *n, *nentry;
	struct audit_watch *watch;
	struct audit_tree *tree;
	int i, err = 0;

	/* audit_filter_mutex synchronizes the writers */
	mutex_lock(&audit_filter_mutex);

	for (i = 0; i < AUDIT_NR_FILTERS; i++) {
		list_for_each_entry_safe(entry, n, &audit_filter_list[i], list) {
			if (!security_audit_rule_known(&entry->rule))
				continue;

			watch = entry->rule.watch;
			tree = entry->rule.tree;
			nentry = audit_dupe_rule(&entry->rule, watch);
			if (IS_ERR(nentry)) {
				/* save the first error encountered for the
				 * return value */
				if (!err)
					err = PTR_ERR(nentry);
				audit_panic("error updating LSM filters");
				if (watch)
					list_del(&entry->rule.rlist);
				list_del_rcu(&entry->list);
			} else {
				if (watch) {
					list_add(&nentry->rule.rlist,
						 &watch->rules);
					list_del(&entry->rule.rlist);
				} else if (tree)
					list_replace_init(&entry->rule.rlist,
						     &nentry->rule.rlist);
				list_replace_rcu(&entry->list, &nentry->list);
			}
			call_rcu(&entry->rcu, audit_free_rule_rcu);
		}
	}

	mutex_unlock(&audit_filter_mutex);

	return err;
}

/* Update watch data in audit rules based on inotify events. */
void audit_handle_ievent(struct inotify_watch *i_watch, u32 wd, u32 mask,
			 u32 cookie, const char *dname, struct inode *inode)
{
	struct audit_parent *parent;

	parent = container_of(i_watch, struct audit_parent, wdata);

	if (mask & (IN_CREATE|IN_MOVED_TO) && inode)
		audit_update_watch(parent, dname, inode->i_sb->s_dev,
				   inode->i_ino, 0);
	else if (mask & (IN_DELETE|IN_MOVED_FROM))
		audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
	/* inotify automatically removes the watch and sends IN_IGNORED */
	else if (mask & (IN_DELETE_SELF|IN_UNMOUNT))
		audit_remove_parent_watches(parent);
	/* inotify does not remove the watch, so remove it manually */
	else if(mask & IN_MOVE_SELF) {
		audit_remove_parent_watches(parent);
		inotify_remove_watch_locked(audit_ih, i_watch);
	} else if (mask & IN_IGNORED)
		put_inotify_watch(i_watch);
}