5:45 p.m.
Add support for a rule key, which can be used to tie audit records to audit
rules. This is useful when a watched file is accessed through a link or
symlink, as well as for general audit log analysis.
Because this patch uses a string key instead of an integer key, there is a bit
of extra overhead to do the kstrdup() when a rule fires. However, we're also
allocating memory for the audit record buffer, so it's probably not that
significant. I went ahead with a string key because it seems more
user-friendly.
Note that the user must ensure that filterkeys are unique. The kernel only
checks for duplicate rules.
Signed-off-by: Amy Griffis <amy.griffis(a)hpd.com>
---
include/linux/audit.h | 3 ++
kernel/audit.h | 1 +
kernel/auditfilter.c | 95 ++++++++++++++++++++++++++++++-------------------
kernel/auditsc.c | 15 ++++++++
4 files changed, 78 insertions(+), 36 deletions(-)
diff --git a/include/linux/audit.h b/include/linux/audit.h
index e1c1dbd..f7883ec 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -123,6 +123,7 @@ #define AUDIT_ALWAYS 2 /* Generate aud
/* Rule structure sizes -- if these change, different AUDIT_ADD and
* AUDIT_LIST commands must be implemented. */
#define AUDIT_MAX_FIELDS 64
+#define AUDIT_MAX_KEY_LEN 32
#define AUDIT_BITMASK_SIZE 64
#define AUDIT_WORD(nr) ((__u32)((nr)/32))
#define AUDIT_BIT(nr) (1 << ((nr) - AUDIT_WORD(nr)*32))
@@ -172,6 +173,8 @@ #define AUDIT_ARG1 (AUDIT_ARG0+1)
#define AUDIT_ARG2 (AUDIT_ARG0+2)
#define AUDIT_ARG3 (AUDIT_ARG0+3)
+#define AUDIT_FILTERKEY 210
+
#define AUDIT_NEGATE 0x80000000
/* These are the supported operators.
diff --git a/kernel/audit.h b/kernel/audit.h
index 38e62b7..0381640 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -81,6 +81,7 @@ struct audit_krule {
u32 mask[AUDIT_BITMASK_SIZE];
u32 buflen; /* for data alloc on list rules */
u32 field_count;
+ char *filterkey; /* ties events to rules */
struct audit_field *fields;
struct audit_field *inode_f; /* quick access to an inode field */
struct audit_watch *watch; /* associated watch */
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 4c99d2c..e98db08 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -141,6 +141,7 @@ static inline void audit_free_rule(struc
selinux_audit_rule_free(f->se_rule);
}
kfree(e->rule.fields);
+ kfree(e->rule.filterkey);
kfree(e);
}
@@ -511,6 +512,16 @@ static struct audit_entry *audit_data_to
if (err)
goto exit_free;
break;
+ case AUDIT_FILTERKEY:
+ err = -EINVAL;
+ if (entry->rule.filterkey || f->val > AUDIT_MAX_KEY_LEN)
+ goto exit_free;
+ str = audit_unpack_string(&bufp, &remain, f->val);
+ if (IS_ERR(str))
+ goto exit_free;
+ entry->rule.buflen += f->val;
+ entry->rule.filterkey = str;
+ break;
default:
goto exit_free;
}
@@ -612,6 +623,10 @@ static struct audit_rule_data *audit_kru
data->buflen += data->values[i] =
audit_pack_string(&bufp, krule->watch->path);
break;
+ case AUDIT_FILTERKEY:
+ data->buflen += data->values[i] =
+ audit_pack_string(&bufp, krule->filterkey);
+ break;
default:
data->values[i] = f->val;
}
@@ -651,6 +666,11 @@ static int audit_compare_rule(struct aud
if (strcmp(a->watch->path, b->watch->path))
return 1;
break;
+ case AUDIT_FILTERKEY:
+ /* both filterkeys exist based on above type compare */
+ if (strcmp(a->filterkey, b->filterkey))
+ return 1;
+ break;
default:
if (a->fields[i].val != b->fields[i].val)
return 1;
@@ -730,6 +750,7 @@ static struct audit_entry *audit_dupe_ru
u32 fcount = old->field_count;
struct audit_entry *entry;
struct audit_krule *new;
+ char *fk;
int i, err = 0;
entry = audit_init_entry(fcount);
@@ -760,6 +781,13 @@ static struct audit_entry *audit_dupe_ru
case AUDIT_SE_CLR:
err = audit_dupe_selinux_field(&new->fields[i],
&old->fields[i]);
+ break;
+ case AUDIT_FILTERKEY:
+ fk = kstrdup(old->filterkey, GFP_KERNEL);
+ if (unlikely(!fk))
+ err = -ENOMEM;
+ else
+ new->filterkey = fk;
}
if (err) {
audit_free_rule(entry);
@@ -1245,6 +1273,34 @@ static void audit_list_rules(int pid, in
skb_queue_tail(q, skb);
}
+/* Log rule additions and removals */
+static void audit_log_rule_change(uid_t loginuid, u32 sid, char *action,
+ struct audit_krule *rule, int res)
+{
+ struct audit_buffer *ab;
+
+ ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
+ if (!ab)
+ return;
+ audit_log_format(ab, "auid=%u", loginuid);
+ if (sid) {
+ char *ctx = NULL;
+ u32 len;
+ if (selinux_ctxid_to_string(sid, &ctx, &len))
+ audit_log_format(ab, " ssid=%u", sid);
+ else
+ audit_log_format(ab, " subj=%s", ctx);
+ kfree(ctx);
+ }
+ audit_log_format(ab, " %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
@@ -1304,24 +1360,7 @@ int audit_receive_filter(int type, int p
err = audit_add_rule(entry,
&audit_filter_list[entry->rule.listnr]);
-
- if (sid) {
- char *ctx = NULL;
- u32 len;
- if (selinux_ctxid_to_string(sid, &ctx, &len)) {
- /* Maybe call audit_panic? */
- audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
- "auid=%u ssid=%u add rule to list=%d res=%d",
- loginuid, sid, entry->rule.listnr, !err);
- } else
- audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
- "auid=%u subj=%s add rule to list=%d res=%d",
- loginuid, ctx, entry->rule.listnr, !err);
- kfree(ctx);
- } else
- audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
- "auid=%u add rule to list=%d res=%d",
- loginuid, entry->rule.listnr, !err);
+ audit_log_rule_change(loginuid, sid, "add", &entry->rule, !err);
if (err)
audit_free_rule(entry);
@@ -1337,24 +1376,8 @@ int audit_receive_filter(int type, int p
err = audit_del_rule(entry,
&audit_filter_list[entry->rule.listnr]);
-
- if (sid) {
- char *ctx = NULL;
- u32 len;
- if (selinux_ctxid_to_string(sid, &ctx, &len)) {
- /* Maybe call audit_panic? */
- audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
- "auid=%u ssid=%u remove rule from list=%d res=%d",
- loginuid, sid, entry->rule.listnr, !err);
- } else
- audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
- "auid=%u subj=%s remove rule from list=%d res=%d",
- loginuid, ctx, entry->rule.listnr, !err);
- kfree(ctx);
- } else
- audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
- "auid=%u remove rule from list=%d res=%d",
- loginuid, entry->rule.listnr, !err);
+ audit_log_rule_change(loginuid, sid, "remove", &entry->rule,
+ !err);
audit_free_rule(entry);
break;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 1c43dba..b32ccfa 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -186,6 +186,7 @@ struct audit_context {
int auditable; /* 1 if record should be written */
int name_count;
struct audit_names names[AUDIT_NAMES];
+ char * filterkey; /* key for rule that triggered record */
struct dentry * pwd;
struct vfsmount * pwdmnt;
struct audit_context *previous; /* For nested syscalls */
@@ -348,11 +349,17 @@ static int audit_filter_rules(struct tas
if (ctx)
result = audit_comparator(ctx->argv[f->type-AUDIT_ARG0], f->op, f->val);
break;
+ case AUDIT_FILTERKEY:
+ /* ignore this field for filtering */
+ result = 1;
+ break;
}
if (!result)
return 0;
}
+ if (rule->filterkey)
+ ctx->filterkey = kstrdup(rule->filterkey, GFP_ATOMIC);
switch (rule->action) {
case AUDIT_NEVER: *state = AUDIT_DISABLED; break;
case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break;
@@ -627,6 +634,7 @@ static inline void audit_free_context(st
}
audit_free_names(context);
audit_free_aux(context);
+ kfree(context->filterkey);
kfree(context);
context = previous;
} while (context);
@@ -736,6 +744,11 @@ static void audit_log_exit(struct audit_
context->euid, context->suid, context->fsuid,
context->egid, context->sgid, context->fsgid, tty);
audit_log_task_info(ab, tsk);
+ if (context->filterkey) {
+ audit_log_format(ab, " key=");
+ audit_log_untrustedstring(ab, context->filterkey);
+ } else
+ audit_log_format(ab, " key=(null)");
audit_log_end(ab);
for (aux = context->aux; aux; aux = aux->next) {
@@ -1061,6 +1074,8 @@ void audit_syscall_exit(int valid, long
} else {
audit_free_names(context);
audit_free_aux(context);
+ kfree(context->filterkey);
+ context->filterkey = NULL;
tsk->audit_context = context;
}
}
--
1.4.0