Add support for non-root users to use initctl, e.g. group wheel

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

configure.ac

@@ -114,6 +114,10 @@ AC_ARG_WITH(sysconfig,
         AS_HELP_STRING([--with-sysconfig=DIR], [System environment directory, sourced by .conf files, default /etc/default & /etc/conf.d]),
 	[sysconfig=$withval], [sysconfig=default])
 
+AC_ARG_WITH(group,
+	AS_HELP_STRING([--with-group=NAME], [Group for /run/finit/socket (initctl), default: root]),
+	[group=$withval], [group=root])
+
 AC_ARG_WITH(hostname,
         AS_HELP_STRING([--with-hostname=NAME], [If /etc/hostname is missing, default: noname]),
 	[hostname=$withval], [hostname=yes])
@@ -188,6 +192,11 @@ AS_IF([test "x$with_heading" != "xno"], [
 	AS_IF([test "x$heading" = "xyes"], [heading=""])
 	AC_DEFINE_UNQUOTED(INIT_OSHEADING, "$heading", [Displayed by Finit at boot, defaults to /etc/os-release PRETTY_NAME])])
 
+AS_IF([test "x$with_group" != "xno"], [
+	AS_IF([test "x$group" = "xyes"], [
+		group=root])])
+AC_DEFINE_UNQUOTED(DEFGROUP, "$group", [For /run/finit/socket])
+
 AS_IF([test "x$with_hostname" != "xno"], [
 	AS_IF([test "x$hostname" = "xyes"], [
 		hostname=noname])])
@@ -273,6 +282,7 @@ Optional features:
   Run fsck fix mode.....: $enable_fsckfix
   Redirect output.......: $enable_redirect
   Default hostname......: $hostname
+  Default group.........: $group
   Default runlevel......: $runlevel
 
 ------------- Compiler version --------------

src/api.c

@@ -466,12 +466,13 @@ error:
 
 int api_init(uev_ctx_t *ctx)
 {
-	int sd;
-	mode_t oldmask;
 	struct sockaddr_un sun = {
 		.sun_family = AF_UNIX,
 		.sun_path   = INIT_SOCKET,
 	};
+	mode_t oldmask;
+	int uid, gid;
+	int sd;
 
 	_d("Setting up external API socket ...");
 	sd = socket(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0);
@@ -480,14 +481,20 @@ int api_init(uev_ctx_t *ctx)
 		return 1;
 	}
 
+	uid = geteuid();
+	gid = getgroup(DEFGROUP);
+
 	erase(INIT_SOCKET);
-	oldmask = umask(0077);
+	oldmask = umask(0117);
 	if (-1 == bind(sd, (struct sockaddr*)&sun, sizeof(sun)))
 		goto error;
 
 	if (-1 == listen(sd, 10))
 		goto error;
 
+	if (chown(INIT_SOCKET, uid, gid))
+		_pe("Failed setting group %s on %s", DEFGROUP, INIT_SOCKET);
+
 	umask(oldmask);
 	if (!uev_io_init(ctx, &api_watcher, api_cb, NULL, sd, UEV_READ))
 		return 0;