[PATCH] add rule filterkey

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@hpd.com>

diff --git a/include/linux/audit.h b/include/linux/audit.h
index e051ff9..a489104 100644 (file)
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -122,6 +122,7 @@
 /* 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))
@@ -171,6 +172,8 @@
 #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 8323e41..6aa33b8 100644 (file)
--- 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 (file)
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -141,6 +141,7 @@ static inline void audit_free_rule(struct audit_entry *e)
                        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_entry(struct audit_rule_data *data,
                        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_krule_to_data(struct audit_krule *krule)
                        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 audit_krule *a, struct audit_krule *b)
                        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_rule(struct audit_krule *old,
        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_rule(struct audit_krule *old,
                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, int seq, struct sk_buff_head *q)
                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 pid, int uid, int seq, void *data,
 
                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 pid, int uid, int seq, void *data,
 
                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 dc5e3f0..3166578 100644 (file)
--- 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 task_struct *tsk,
                        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(struct audit_context *context)
                }
                audit_free_names(context);
                audit_free_aux(context);
+               kfree(context->filterkey);
                kfree(context);
                context  = previous;
        } while (context);
@@ -735,6 +743,11 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
                  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) {
@@ -1060,6 +1073,8 @@ void audit_syscall_exit(int valid, long return_code)
        } else {
                audit_free_names(context);
                audit_free_aux(context);
+               kfree(context->filterkey);
+               context->filterkey = NULL;
                tsk->audit_context = context;
        }
 }