--- a/svr-runopts.c	Wed Feb 21 21:59:52 2018 +0800
+++ b/svr-runopts.c	Mon Feb 26 22:44:48 2018 +0800
@@ -30,6 +30,8 @@
 #include "algo.h"
 #include "ecdsa.h"
 
+#include <grp.h>
+
 svr_runopts svr_opts; /* GLOBAL */
 
 static void printhelp(const char * progname);
@@ -68,6 +70,7 @@
 					"-m		Don't display the motd on login\n"
 #endif
 					"-w		Disallow root logins\n"
+					"-G		Restrict logins to members of specified group\n"
 #if DROPBEAR_SVR_PASSWORD_AUTH || DROPBEAR_SVR_PAM_AUTH
 					"-s		Disable password logins\n"
 					"-g		Disable password logins for root\n"
@@ -132,6 +135,8 @@
 	svr_opts.forced_command = NULL;
 	svr_opts.forkbg = 1;
 	svr_opts.norootlogin = 0;
+	svr_opts.restrict_group = NULL;
+	svr_opts.restrict_group_gid = 0;
 	svr_opts.noauthpass = 0;
 	svr_opts.norootpass = 0;
 	svr_opts.allowblankpass = 0;
@@ -230,6 +235,9 @@
 				case 'w':
 					svr_opts.norootlogin = 1;
 					break;
+				case 'G':
+					next = &svr_opts.restrict_group;
+					break;
 				case 'W':
 					next = &recv_window_arg;
 					break;
@@ -331,6 +339,17 @@
 		}
 		buf_setpos(svr_opts.banner, 0);
 	}
+
+	if (svr_opts.restrict_group) {
+		struct group *restrictedgroup = getgrnam(svr_opts.restrict_group);
+
+		if (restrictedgroup){
+			svr_opts.restrict_group_gid = restrictedgroup->gr_gid;
+		} else {
+			dropbear_exit("Cannot restrict logins to group '%s' as the group does not exist", svr_opts.restrict_group);
+		}
+
+	}
 	
 	if (recv_window_arg) {
 		opts.recv_window = atol(recv_window_arg);
@@ -511,17 +530,20 @@
 		m_free(hostkey_file);
 	}
 
+	/* Only load default host keys if a host key is not specified by the user */
+	if (svr_opts.num_hostkey_files == 0) {
 #if DROPBEAR_RSA
-	loadhostkey(RSA_PRIV_FILENAME, 0);
+		loadhostkey(RSA_PRIV_FILENAME, 0);
 #endif
 
 #if DROPBEAR_DSS
-	loadhostkey(DSS_PRIV_FILENAME, 0);
+		loadhostkey(DSS_PRIV_FILENAME, 0);
 #endif
 
 #if DROPBEAR_ECDSA
-	loadhostkey(ECDSA_PRIV_FILENAME, 0);
+		loadhostkey(ECDSA_PRIV_FILENAME, 0);
 #endif
+	}
 
 #if DROPBEAR_DELAY_HOSTKEY
 	if (svr_opts.delay_hostkey) {