add -f background option to dbclient

--HG--
extra : convert_revision : 5ef61c30c0a634ac0da22a8c694ce235690e8170

cli-runopts.c

@@ -51,6 +51,7 @@ static void printhelp() {
 					"-t    Allocate a pty\n"
 					"-T    Don't allocate a pty\n"
 					"-N    Don't run a remote command\n"
+					"-f    Run in background after auth\n"
 #ifdef ENABLE_CLI_PUBKEY_AUTH
 					"-i <identityfile>   (multiple allowed)\n"
 #endif
@@ -90,6 +91,7 @@ void cli_getopts(int argc, char ** argv) {
 	cli_opts.username = NULL;
 	cli_opts.cmd = NULL;
 	cli_opts.no_cmd = 0;
+	cli_opts.backgrounded = 0;
 	cli_opts.wantpty = 9; /* 9 means "it hasn't been touched", gets set later */
 #ifdef ENABLE_CLI_PUBKEY_AUTH
 	cli_opts.privkeys = NULL;
@@ -168,6 +170,9 @@ void cli_getopts(int argc, char ** argv) {
 				case 'N':
 					cli_opts.no_cmd = 1;
 					break;
+				case 'f':
+					cli_opts.backgrounded = 1;
+					break;
 #ifdef ENABLE_CLI_LOCALTCPFWD
 				case 'L':
 					nextislocal = 1;
@@ -274,6 +279,11 @@ void cli_getopts(int argc, char ** argv) {
 			cli_opts.wantpty = 0;
 		}
 	}
+
+	if (cli_opts.backgrounded && cli_opts.cmd == NULL
+			&& cli_opts.no_cmd == 0) {
+		dropbear_exit("command required for -f");
+	}
 }
 
 #ifdef ENABLE_CLI_PUBKEY_AUTH

cli-session.c

@@ -212,6 +212,23 @@ static void cli_sessionloop() {
 			*/
 
 		case USERAUTH_SUCCESS_RCVD:
+
+			if (cli_opts.backgrounded) {
+				int devnull;
+				// keeping stdin open steals input from the terminal and
+				// is confusing, though stdout/stderr could be useful.
+				devnull = open(_PATH_DEVNULL, O_RDONLY);
+				if (devnull < 0) {
+					dropbear_exit("opening /dev/null: %d %s",
+							errno, strerror(errno));
+				}
+				dup2(devnull, STDIN_FILENO);
+				if (daemon(0, 1) < 0) {
+					dropbear_exit("Backgrounding failed: %d %s", 
+							errno, strerror(errno));
+				}
+			}
+			
 #ifdef ENABLE_CLI_LOCALTCPFWD
 			setup_localtcp();
 #endif

dbclient.1

@@ -63,6 +63,10 @@ Don't allocate a pty.
 .B \-N
 Don't request a remote shell or run any commands. Any command arguments are ignored.
 .TP
+.B \-f
+Fork into the background after authentication. A command argument (or -N) is required.
+This is useful when using password authentication.
+.TP
 .B \-g
 Allow non-local hosts to connect to forwarded ports. Applies to -L and -R
 forwarded ports, though remote connections to -R forwarded ports may be limited

runopts.h

@@ -103,6 +103,7 @@ typedef struct cli_runopts {
 	char *cmd;
 	int wantpty;
 	int no_cmd;
+	int backgrounded;
 #ifdef ENABLE_CLI_PUBKEY_AUTH
 	struct SignKeyList *privkeys; /* Keys to use for public-key auth */
 #endif