Proof of concept patch, add dropping privileges to a non root user

["corentin.labbe" <corentin.labbe@geomatys.fr>]

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Hello

This is a patch that add a -u parameter to auditd.
This parameter permit to auditd to drop to an unprivilegied UID after initialization.

Any comment will be appreciated.

Cordially




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--- src/auditd.c.orig	2009-10-05 14:18:52.000000000 +0200
+++ src/auditd.c	2009-10-05 14:55:36.000000000 +0200
@@ -471,9 +471,10 @@
 	struct ev_signal sigusr2_watcher;
 	struct ev_signal sigchld_watcher;
 	int rc;
+	int auditd_uid=0;
 
 	/* Get params && set mode */
-	while ((c = getopt(argc, argv, "flns:")) != -1) {
+	while ((c = getopt(argc, argv, "flns:u:")) != -1) {
 		switch (c) {
 		case 'f':
 			opt_foreground = 1;
@@ -481,6 +482,17 @@
 		case 'l':
 			opt_allow_links=1;
 			break;
+		case 'u':
+			auditd_uid = atoi(optarg);
+			if (auditd_uid > 65535) {
+				fprintf(stderr, "Invalid UID '%s' > 65535\n", optarg);
+				usage();
+			}
+			if (auditd_uid < 0) {
+				fprintf(stderr, "Invalid UID '%s' < 0\n", optarg);
+				usage();
+			}
+			break;
 		case 'n':
 			do_fork = 0;
 			break;
@@ -522,7 +534,7 @@
 
 #ifndef DEBUG
 	/* Make sure we are root */
-	if (getuid() != 0) {
+	if (getuid() != 0 && auditd_uid == 0) {
 		fprintf(stderr, "You must be root to run this program.\n");
 		return 4;
 	}
@@ -690,6 +702,14 @@
 		shutdown_dispatcher();
 		return 1;
 	}
+	
+	if (auditd_uid > 0)
+		if (setuid(auditd_uid) == -1) {
+			fprintf(stderr, "setuid error() %d.\n", errno);
+			shutdown_dispatcher();
+			return 1;
+		}
+	
 	audit_msg(LOG_NOTICE,
 	    "Init complete, auditd %s listening for events (startup state %s)",
 		VERSION,

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