[PATCH] Split audit filtering into auditfilter.c
David Woodhouse
dwmw2 at infradead.org
Thu Dec 15 23:51:06 UTC 2005
On Thu, 2005-12-15 at 14:43 -0600, Dustin Kirkland wrote:
> David-
>
> Best as I can tell, this patch includes all of the lines that are
> being removed out of auditsc.c, but I don't see the lines that are
> adding the code to the new file auditfilter.c. Perhaps the diff --git
> didn't include the -N option?
Hm, I didn't actually manage to commit them to git at all the second
time (having reverted my first version). I've added them to the git tree
now; thanks.
diff --git a/kernel/audit.h b/kernel/audit.h
new file mode 100644
index 0000000..7643e46
--- /dev/null
+++ b/kernel/audit.h
@@ -0,0 +1,70 @@
+/* audit -- definition of audit_context structure and supporting types
+ *
+ * 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/fs.h>
+#include <linux/audit.h>
+
+/* 0 = no checking
+ 1 = put_count checking
+ 2 = verbose put_count checking
+*/
+#define AUDIT_DEBUG 0
+
+/* At task start time, the audit_state is set in the audit_context using
+ a per-task filter. At syscall entry, the audit_state is augmented by
+ the syscall filter. */
+enum audit_state {
+ AUDIT_DISABLED, /* Do not create per-task audit_context.
+ * No syscall-specific audit records can
+ * be generated. */
+ AUDIT_SETUP_CONTEXT, /* Create the per-task audit_context,
+ * but don't necessarily fill it in at
+ * syscall entry time (i.e., filter
+ * instead). */
+ AUDIT_BUILD_CONTEXT, /* Create the per-task audit_context,
+ * and always fill it in at syscall
+ * entry time. This makes a full
+ * syscall record available if some
+ * other part of the kernel decides it
+ * should be recorded. */
+ AUDIT_RECORD_CONTEXT /* Create the per-task audit_context,
+ * always fill it in at syscall entry
+ * time, and always write out the audit
+ * record at syscall exit time. */
+};
+
+/* Rule lists */
+struct audit_entry {
+ struct list_head list;
+ struct rcu_head rcu;
+ struct audit_rule rule;
+};
+
+
+extern int audit_pid;
+extern int audit_comparator(const u32 left, const u32 op, const u32 right);
+
+extern void audit_send_reply(int pid, int seq, int type,
+ int done, int multi,
+ void *payload, int size);
+extern void audit_log_lost(const char *message);
+extern void audit_panic(const char *message);
+extern struct semaphore audit_netlink_sem;
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
new file mode 100644
index 0000000..355b812
--- /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_EXCLUDE:
+#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_exclude(int type)
+{
+ struct audit_entry *e;
+ int result = 0;
+
+ rcu_read_lock();
+ if (list_empty(&audit_filter_list[AUDIT_FILTER_EXCLUDE]))
+ goto unlock_and_return;
+
+ list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_EXCLUDE],
+ 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;
+}
+
+
--
dwmw2
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