[PATCH] Fix audit record filtering with !CONFIG_AUDITSYSCALL

This fixes the per-user and per-message-type filtering when syscall
auditing isn't enabled.

[AV: folded followup fix from the same author]

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 378 insertions, 0 deletions

diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
new file mode 100644
index 00000000000..7f347c36087
--- /dev/null
+++ b/kernel/auditfilter.c
@@ -0,0 +1,378 @@
+/* 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
+};
+
+/* Copy rule from user-space to kernel-space.  Called from 
+ * audit_add_rule during AUDIT_ADD. */
+static inline int audit_copy_rule(struct audit_rule *d, struct audit_rule *s)
+{
+	int i;
+
+	if (s->action != AUDIT_NEVER
+	    && s->action != AUDIT_POSSIBLE
+	    && s->action != AUDIT_ALWAYS)
+		return -1;
+	if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS)
+		return -1;
+	if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS)
+		return -1;
+
+	d->flags	= s->flags;
+	d->action	= s->action;
+	d->field_count	= s->field_count;
+	for (i = 0; i < d->field_count; i++) {
+		d->fields[i] = s->fields[i];
+		d->values[i] = s->values[i];
+	}
+	for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i];
+	return 0;
+}
+
+/* Check to see if two rules are identical.  It is called from
+ * audit_add_rule during AUDIT_ADD and 
+ * audit_del_rule during AUDIT_DEL. */
+static inline int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
+{
+	int i;
+
+	if (a->flags != b->flags)
+		return 1;
+
+	if (a->action != b->action)
+		return 1;
+
+	if (a->field_count != b->field_count)
+		return 1;
+
+	for (i = 0; i < a->field_count; i++) {
+		if (a->fields[i] != b->fields[i]
+		    || a->values[i] != b->values[i])
+			return 1;
+	}
+
+	for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
+		if (a->mask[i] != b->mask[i])
+			return 1;
+
+	return 0;
+}
+
+/* Note that audit_add_rule and audit_del_rule are called via
+ * audit_receive() in audit.c, and are protected by
+ * audit_netlink_sem. */
+static inline int audit_add_rule(struct audit_rule *rule,
+				  struct list_head *list)
+{
+	struct audit_entry  *entry;
+	int i;
+
+	/* Do not use the _rcu iterator here, since this is the only
+	 * addition routine. */
+	list_for_each_entry(entry, list, list) {
+		if (!audit_compare_rule(rule, &entry->rule)) {
+			return -EEXIST;
+		}
+	}
+
+	for (i = 0; i < rule->field_count; i++) {
+		if (rule->fields[i] & AUDIT_UNUSED_BITS)
+			return -EINVAL;
+		if ( rule->fields[i] & AUDIT_NEGATE )
+			rule->fields[i] |= AUDIT_NOT_EQUAL;
+		else if ( (rule->fields[i] & AUDIT_OPERATORS) == 0 )
+			rule->fields[i] |= AUDIT_EQUAL;
+		rule->fields[i] &= (~AUDIT_NEGATE);
+	}
+
+	if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL)))
+		return -ENOMEM;
+	if (audit_copy_rule(&entry->rule, rule)) {
+		kfree(entry);
+		return -EINVAL;
+	}
+
+	if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
+		entry->rule.flags &= ~AUDIT_FILTER_PREPEND;
+		list_add_rcu(&entry->list, list);
+	} else {
+		list_add_tail_rcu(&entry->list, list);
+	}
+
+	return 0;
+}
+
+static inline void audit_free_rule(struct rcu_head *head)
+{
+	struct audit_entry *e = container_of(head, struct audit_entry, rcu);
+	kfree(e);
+}
+
+/* Note that audit_add_rule and audit_del_rule are called via
+ * audit_receive() in audit.c, and are protected by
+ * audit_netlink_sem. */
+static inline int audit_del_rule(struct audit_rule *rule,
+				 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(rule, &e->rule)) {
+			list_del_rcu(&e->list);
+			call_rcu(&e->rcu, audit_free_rule);
+			return 0;
+		}
+	}
+	return -ENOENT;		/* No matching rule */
+}
+
+static int audit_list_rules(void *_dest)
+{
+	int pid, seq;
+	int *dest = _dest;
+	struct audit_entry *entry;
+	int i;
+
+	pid = dest[0];
+	seq = dest[1];
+	kfree(dest);
+
+	down(&audit_netlink_sem);
+
+	/* The *_rcu iterators not needed here because we are
+	   always called with audit_netlink_sem held. */
+	for (i=0; i<AUDIT_NR_FILTERS; i++) {
+		list_for_each_entry(entry, &audit_filter_list[i], list)
+			audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
+					 &entry->rule, sizeof(entry->rule));
+	}
+	audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0);
+	
+	up(&audit_netlink_sem);
+	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
+ * @loginuid: loginuid of sender
+ */
+int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
+							uid_t loginuid)
+{
+	struct task_struct *tsk;
+	int *dest;
+	int		   err = 0;
+	unsigned listnr;
+
+	switch (type) {
+	case AUDIT_LIST:
+		/* 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;
+
+		tsk = kthread_run(audit_list_rules, dest, "audit_list_rules");
+		if (IS_ERR(tsk)) {
+			kfree(dest);
+			err = PTR_ERR(tsk);
+		}
+		break;
+	case AUDIT_ADD:
+		listnr = ((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
+		switch(listnr) {
+		default:
+			return -EINVAL;
+
+		case AUDIT_FILTER_USER:
+		case AUDIT_FILTER_TYPE:
+#ifdef CONFIG_AUDITSYSCALL
+		case AUDIT_FILTER_ENTRY:
+		case AUDIT_FILTER_EXIT:
+		case AUDIT_FILTER_TASK:
+#endif
+			;
+		}
+		err = audit_add_rule(data, &audit_filter_list[listnr]);
+		if (!err)
+			audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
+				  "auid=%u added an audit rule\n", loginuid);
+		break;
+	case AUDIT_DEL:
+		listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
+		if (listnr >= AUDIT_NR_FILTERS)
+			return -EINVAL;
+
+		err = audit_del_rule(data, &audit_filter_list[listnr]);
+		if (!err)
+			audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
+				  "auid=%u removed an audit rule\n", loginuid);
+		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);
+	default:
+		return -EINVAL;
+	}
+}
+
+
+
+static int audit_filter_user_rules(struct netlink_skb_parms *cb,
+				   struct audit_rule *rule,
+				   enum audit_state *state)
+{
+	int i;
+
+	for (i = 0; i < rule->field_count; i++) {
+		u32 field  = rule->fields[i] & ~AUDIT_OPERATORS;
+		u32 op  = rule->fields[i] & AUDIT_OPERATORS;
+		u32 value  = rule->values[i];
+		int result = 0;
+
+		switch (field) {
+		case AUDIT_PID:
+			result = audit_comparator(cb->creds.pid, op, value);
+			break;
+		case AUDIT_UID:
+			result = audit_comparator(cb->creds.uid, op, value);
+			break;
+		case AUDIT_GID:
+			result = audit_comparator(cb->creds.gid, op, value);
+			break;
+		case AUDIT_LOGINUID:
+			result = audit_comparator(cb->loginuid, op, value);
+			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) {
+		struct audit_rule *rule = &e->rule;
+		int i;
+		for (i = 0; i < rule->field_count; i++) {
+			u32 field  = rule->fields[i] & ~AUDIT_OPERATORS;
+			u32 op  = rule->fields[i] & AUDIT_OPERATORS;
+			u32 value  = rule->values[i];
+			if ( field == AUDIT_MSGTYPE ) {
+				result = audit_comparator(type, op, value); 
+				if (!result)
+					break;
+			}
+		}
+		if (result)
+			goto unlock_and_return;
+	}
+unlock_and_return:
+	rcu_read_unlock();
+	return result;
+}
+
+