audit: implement audit by executable

This adds the ability audit the actions of a not-yet-running process.

This patch implements the ability to filter on the executable path.  Instead of
just hard coding the ino and dev of the executable we care about at the moment
the rule is inserted into the kernel, use the new audit_fsnotify
infrastructure to manage this dynamically.  This means that if the filename
does not yet exist but the containing directory does, or if the inode in
question is unlinked and creat'd (aka updated) the rule will just continue to
work.  If the containing directory is moved or deleted or the filesystem is
unmounted, the rule is deleted automatically.  A future enhancement would be to
have the rule survive across directory disruptions.

This is a heavily modified version of a patch originally submitted by Eric
Paris with some ideas from Peter Moody.

Cc: Peter Moody <peter@hda3.com>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
[PM: minor whitespace clean to satisfy ./scripts/checkpatch]
Signed-off-by: Paul Moore <pmoore@redhat.com>

include/linux/audit.h

@@ -62,6 +62,7 @@ struct audit_krule {
 	struct audit_field	*inode_f; /* quick access to an inode field */
 	struct audit_watch	*watch;	/* associated watch */
 	struct audit_tree	*tree;	/* associated watched tree */
+	struct audit_fsnotify_mark	*exe;
 	struct list_head	rlist;	/* entry in audit_{watch,tree}.rules list */
 	struct list_head	list;	/* for AUDIT_LIST* purposes only */
 	u64			prio;

include/uapi/linux/audit.h

@@ -266,6 +266,7 @@
 #define AUDIT_OBJ_UID	109
 #define AUDIT_OBJ_GID	110
 #define AUDIT_FIELD_COMPARE	111
+#define AUDIT_EXE	112
 
 #define AUDIT_ARG0      200
 #define AUDIT_ARG1      (AUDIT_ARG0+1)
@@ -324,8 +325,10 @@ enum {
 
 #define AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT	0x00000001
 #define AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME	0x00000002
+#define AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH	0x00000004
 #define AUDIT_FEATURE_BITMAP_ALL (AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
-				  AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME)
+				  AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME | \
+				  AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH)
 
 /* deprecated: AUDIT_VERSION_* */
 #define AUDIT_VERSION_LATEST 		AUDIT_FEATURE_BITMAP_ALL

kernel/audit.h

@@ -274,6 +274,8 @@ extern char *audit_mark_path(struct audit_fsnotify_mark *mark);
 extern void audit_remove_mark(struct audit_fsnotify_mark *audit_mark);
 extern void audit_remove_mark_rule(struct audit_krule *krule);
 extern int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long ino, dev_t dev);
+extern int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old);
+extern int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark);
 
 #else
 #define audit_put_watch(w) {}
@@ -289,6 +291,8 @@ extern int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long in
 #define audit_remove_mark(m)
 #define audit_remove_mark_rule(k)
 #define audit_mark_compare(m, i, d) 0
+#define audit_exe_compare(t, m) (-EINVAL)
+#define audit_dupe_exe(n, o) (-EINVAL)
 #endif /* CONFIG_AUDIT_WATCH */
 
 #ifdef CONFIG_AUDIT_TREE

kernel/audit_tree.c

@@ -478,6 +478,8 @@ static void kill_rules(struct audit_tree *tree)
 		if (rule->tree) {
 			/* not a half-baked one */
 			audit_tree_log_remove_rule(rule);
+			if (entry->rule.exe)
+				audit_remove_mark(entry->rule.exe);
 			rule->tree = NULL;
 			list_del_rcu(&entry->list);
 			list_del(&entry->rule.list);

kernel/audit_watch.c

@@ -312,6 +312,8 @@ static void audit_update_watch(struct audit_parent *parent,
 				list_replace(&oentry->rule.list,
 					     &nentry->rule.list);
 			}
+			if (oentry->rule.exe)
+				audit_remove_mark(oentry->rule.exe);
 
 			audit_watch_log_rule_change(r, owatch, "updated_rules");
 
@@ -342,6 +344,8 @@ static void audit_remove_parent_watches(struct audit_parent *parent)
 		list_for_each_entry_safe(r, nextr, &w->rules, rlist) {
 			e = container_of(r, struct audit_entry, rule);
 			audit_watch_log_rule_change(r, w, "remove_rule");
+			if (e->rule.exe)
+				audit_remove_mark(e->rule.exe);
 			list_del(&r->rlist);
 			list_del(&r->list);
 			list_del_rcu(&e->list);
@@ -514,3 +518,30 @@ static int __init audit_watch_init(void)
 	return 0;
 }
 device_initcall(audit_watch_init);
+
+int audit_dupe_exe(struct audit_krule *new, struct audit_krule *old)
+{
+	struct audit_fsnotify_mark *audit_mark;
+	char *pathname;
+
+	pathname = kstrdup(audit_mark_path(old->exe), GFP_KERNEL);
+	if (!pathname)
+		return -ENOMEM;
+
+	audit_mark = audit_alloc_mark(new, pathname, strlen(pathname));
+	if (IS_ERR(audit_mark)) {
+		kfree(pathname);
+		return PTR_ERR(audit_mark);
+	}
+	new->exe = audit_mark;
+
+	return 0;
+}
+
+int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
+{
+	unsigned long ino = tsk->mm->exe_file->f_inode->i_ino;
+	dev_t dev = tsk->mm->exe_file->f_inode->i_sb->s_dev;
+
+	return audit_mark_compare(mark, ino, dev);
+}

kernel/auditfilter.c

@@ -405,6 +405,12 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
 		if (f->val > AUDIT_MAX_FIELD_COMPARE)
 			return -EINVAL;
 		break;
+	case AUDIT_EXE:
+		if (f->op != Audit_equal)
+			return -EINVAL;
+		if (entry->rule.listnr != AUDIT_FILTER_EXIT)
+			return -EINVAL;
+		break;
 	};
 	return 0;
 }
@@ -419,6 +425,7 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 	size_t remain = datasz - sizeof(struct audit_rule_data);
 	int i;
 	char *str;
+	struct audit_fsnotify_mark *audit_mark;
 
 	entry = audit_to_entry_common(data);
 	if (IS_ERR(entry))
@@ -539,6 +546,24 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 			entry->rule.buflen += f->val;
 			entry->rule.filterkey = str;
 			break;
+		case AUDIT_EXE:
+			if (entry->rule.exe || f->val > PATH_MAX)
+				goto exit_free;
+			str = audit_unpack_string(&bufp, &remain, f->val);
+			if (IS_ERR(str)) {
+				err = PTR_ERR(str);
+				goto exit_free;
+			}
+			entry->rule.buflen += f->val;
+
+			audit_mark = audit_alloc_mark(&entry->rule, str, f->val);
+			if (IS_ERR(audit_mark)) {
+				kfree(str);
+				err = PTR_ERR(audit_mark);
+				goto exit_free;
+			}
+			entry->rule.exe = audit_mark;
+			break;
 		}
 	}
 
@@ -551,6 +576,8 @@ exit_nofree:
 exit_free:
 	if (entry->rule.tree)
 		audit_put_tree(entry->rule.tree); /* that's the temporary one */
+	if (entry->rule.exe)
+		audit_remove_mark(entry->rule.exe); /* that's the template one */
 	audit_free_rule(entry);
 	return ERR_PTR(err);
 }
@@ -615,6 +642,10 @@ static struct audit_rule_data *audit_krule_to_data(struct audit_krule *krule)
 			data->buflen += data->values[i] =
 				audit_pack_string(&bufp, krule->filterkey);
 			break;
+		case AUDIT_EXE:
+			data->buflen += data->values[i] =
+				audit_pack_string(&bufp, audit_mark_path(krule->exe));
+			break;
 		case AUDIT_LOGINUID_SET:
 			if (krule->pflags & AUDIT_LOGINUID_LEGACY && !f->val) {
 				data->fields[i] = AUDIT_LOGINUID;
@@ -678,6 +709,12 @@ static int audit_compare_rule(struct audit_krule *a, struct audit_krule *b)
 			if (strcmp(a->filterkey, b->filterkey))
 				return 1;
 			break;
+		case AUDIT_EXE:
+			/* both paths exist based on above type compare */
+			if (strcmp(audit_mark_path(a->exe),
+				   audit_mark_path(b->exe)))
+				return 1;
+			break;
 		case AUDIT_UID:
 		case AUDIT_EUID:
 		case AUDIT_SUID:
@@ -799,8 +836,14 @@ struct audit_entry *audit_dupe_rule(struct audit_krule *old)
 				err = -ENOMEM;
 			else
 				new->filterkey = fk;
+			break;
+		case AUDIT_EXE:
+			err = audit_dupe_exe(new, old);
+			break;
 		}
 		if (err) {
+			if (new->exe)
+				audit_remove_mark(new->exe);
 			audit_free_rule(entry);
 			return ERR_PTR(err);
 		}
@@ -963,6 +1006,9 @@ int audit_del_rule(struct audit_entry *entry)
 	if (e->rule.tree)
 		audit_remove_tree_rule(&e->rule);
 
+	if (e->rule.exe)
+		audit_remove_mark_rule(&e->rule);
+
 #ifdef CONFIG_AUDITSYSCALL
 	if (!dont_count)
 		audit_n_rules--;
@@ -1067,8 +1113,11 @@ int audit_rule_change(int type, __u32 portid, int seq, void *data,
 		WARN_ON(1);
 	}
 
-	if (err || type == AUDIT_DEL_RULE)
+	if (err || type == AUDIT_DEL_RULE) {
+		if (entry->rule.exe)
+			audit_remove_mark(entry->rule.exe);
 		audit_free_rule(entry);
+	}
 
 	return err;
 }
@@ -1360,6 +1409,8 @@ static int update_lsm_rule(struct audit_krule *r)
 		return 0;
 
 	nentry = audit_dupe_rule(r);
+	if (entry->rule.exe)
+		audit_remove_mark(entry->rule.exe);
 	if (IS_ERR(nentry)) {
 		/* save the first error encountered for the
 		 * return value */

kernel/auditsc.c

@@ -466,6 +466,9 @@ static int audit_filter_rules(struct task_struct *tsk,
 				result = audit_comparator(ctx->ppid, f->op, f->val);
 			}
 			break;
+		case AUDIT_EXE:
+			result = audit_exe_compare(tsk, rule->exe);
+			break;
 		case AUDIT_UID:
 			result = audit_uid_comparator(cred->uid, f->op, f->uid);
 			break;