Make keepalive handling more robust, this should now match what OpenSSH does

LICENSE

@@ -8,7 +8,7 @@ The majority of code is written by Matt Johnston, under the license below.
 Portions of the client-mode work are (c) 2004 Mihnea Stoenescu, under the
 same license:
 
-Copyright (c) 2002-2013 Matt Johnston
+Copyright (c) 2002-2014 Matt Johnston
 Portions copyright (c) 2004 Mihnea Stoenescu
 All rights reserved.
 

auth.h

@@ -106,7 +106,7 @@ struct AuthState {
 								valid */
 	unsigned int failcount; /* Number of (failed) authentication attempts.*/
 	unsigned authdone : 1; /* 0 if we haven't authed, 1 if we have. Applies for
-							  client and server (though has differing [obvious]
+							  client and server (though has differing 
 							  meanings). */
 	unsigned perm_warn : 1; /* Server only, set if bad permissions on 
 							   ~/.ssh/authorized_keys have already been

channel.h

@@ -105,6 +105,9 @@ void chancleanup();
 void setchannelfds(fd_set *readfd, fd_set *writefd);
 void channelio(fd_set *readfd, fd_set *writefd);
 struct Channel* getchannel();
+/* Returns an arbitrary channel that is in a ready state - not
+being initialised and no EOF in either direction. NULL if none. */
+struct Channel* get_any_ready_channel();
 
 void recv_msg_channel_open();
 void recv_msg_channel_request();
@@ -128,8 +131,10 @@ int send_msg_channel_open_init(int fd, const struct ChanType *type);
 void recv_msg_channel_open_confirmation();
 void recv_msg_channel_open_failure();
 #endif
+void start_send_channel_request(struct Channel *channel, unsigned char *type);
 
 void send_msg_request_success();
 void send_msg_request_failure();
 
+
 #endif /* _CHANNEL_H_ */

chansession.h

@@ -89,7 +89,6 @@ void cli_chansess_winchange();
 #ifdef ENABLE_CLI_NETCAT
 void cli_send_netcat_request();
 #endif
-void cli_start_send_channel_request(struct Channel *channel, unsigned char *type);
 
 void svr_chansessinitialise();
 extern const struct ChanType svrchansess;

cli-agentfwd.c

@@ -234,7 +234,7 @@ void cli_setup_agent(struct Channel *channel) {
 		return;
 	}
 	
-	cli_start_send_channel_request(channel, "[email protected]");
+	start_send_channel_request(channel, "[email protected]");
 	/* Don't want replies */
 	buf_putbyte(ses.writepayload, 0);
 	encrypt_packet();

cli-chansession.c

@@ -92,17 +92,6 @@ static void cli_closechansess(struct Channel *UNUSED(channel)) {
 	}
 }
 
-void cli_start_send_channel_request(struct Channel *channel, 
-		unsigned char *type) {
-
-	CHECKCLEARTOWRITE();
-	buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_REQUEST);
-	buf_putint(ses.writepayload, channel->remotechan);
-
-	buf_putstring(ses.writepayload, type, strlen(type));
-
-}
-
 /* Taken from OpenSSH's sshtty.c:
  * RCSID("OpenBSD: sshtty.c,v 1.5 2003/09/19 17:43:35 markus Exp "); */
 static void cli_tty_setup() {
@@ -287,7 +276,7 @@ static void send_chansess_pty_req(struct Channel *channel) {
 
 	TRACE(("enter send_chansess_pty_req"))
 
-	cli_start_send_channel_request(channel, "pty-req");
+	start_send_channel_request(channel, "pty-req");
 
 	/* Don't want replies */
 	buf_putbyte(ses.writepayload, 0);
@@ -330,7 +319,7 @@ static void send_chansess_shell_req(struct Channel *channel) {
 		reqtype = "shell";
 	}
 
-	cli_start_send_channel_request(channel, reqtype);
+	start_send_channel_request(channel, reqtype);
 
 	/* XXX TODO */
 	buf_putbyte(ses.writepayload, 0); /* Don't want replies */

cli-session.c

@@ -70,11 +70,15 @@ static const packettype cli_packettypes[] = {
 	{SSH_MSG_USERAUTH_BANNER, recv_msg_userauth_banner}, /* client */
 	{SSH_MSG_USERAUTH_SPECIFIC_60, recv_msg_userauth_specific_60}, /* client */
 	{SSH_MSG_GLOBAL_REQUEST, recv_msg_global_request_cli},
+	{SSH_MSG_CHANNEL_SUCCESS, ignore_recv_response},
+	{SSH_MSG_CHANNEL_FAILURE, ignore_recv_response},
 #ifdef  ENABLE_CLI_REMOTETCPFWD
 	{SSH_MSG_REQUEST_SUCCESS, cli_recv_msg_request_success}, /* client */
 	{SSH_MSG_REQUEST_FAILURE, cli_recv_msg_request_failure}, /* client */
 #else
-	{SSH_MSG_REQUEST_FAILURE, ignore_recv_msg_request_failure}, /* for keepalive */
+	/* For keepalive */
+	{SSH_MSG_REQUEST_SUCCESS, ignore_recv_response},
+	{SSH_MSG_REQUEST_FAILURE, ignore_recv_response},
 #endif
 	{0, 0} /* End */
 };

common-channel.c

@@ -627,7 +627,12 @@ void recv_msg_channel_request() {
 			&& !channel->close_handler_done) {
 		channel->type->reqhandler(channel);
 	} else {
-		send_msg_channel_failure(channel);
+		int wantreply;
+		buf_eatstring(ses.payload);
+		wantreply = buf_getbool(ses.payload);
+		if (wantreply) {
+			send_msg_channel_failure(channel);
+		}
 	}
 
 	TRACE(("leave recv_msg_channel_request"))
@@ -1134,3 +1139,30 @@ void send_msg_request_failure() {
 	buf_putbyte(ses.writepayload, SSH_MSG_REQUEST_FAILURE);
 	encrypt_packet();
 }
+
+struct Channel* get_any_ready_channel() {
+	if (ses.chancount == 0) {
+		return NULL;
+	}
+	size_t i;
+	for (i = 0; i < ses.chansize; i++) {
+		struct Channel *chan = ses.channels[i];
+		if (chan
+				&& !(chan->sent_eof || chan->recv_eof)
+				&& !(chan->await_open || chan->initconn)) {
+			return chan;
+		}
+	}
+	return NULL;
+}
+
+void start_send_channel_request(struct Channel *channel, 
+		unsigned char *type) {
+
+	CHECKCLEARTOWRITE();
+	buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_REQUEST);
+	buf_putint(ses.writepayload, channel->remotechan);
+
+	buf_putstring(ses.writepayload, type, strlen(type));
+
+}

common-session.c

@@ -394,19 +394,30 @@ static int ident_readln(int fd, char* buf, int count) {
 	return pos+1;
 }
 
-void ignore_recv_msg_request_failure() {
+void ignore_recv_response() {
 	// Do nothing
-	TRACE(("Ignored msg_request_failure"))
+	TRACE(("Ignored msg_request_response"))
 }
 
 static void send_msg_keepalive() {
 	CHECKCLEARTOWRITE();
 	time_t old_time_idle = ses.last_packet_time_idle;
-	/* Try to force a response from the other end. Some peers will
-	reply with SSH_MSG_REQUEST_FAILURE, some will reply with SSH_MSG_UNIMPLEMENTED */
-	buf_putbyte(ses.writepayload, SSH_MSG_GLOBAL_REQUEST);
-	/* A short string */
-	buf_putstring(ses.writepayload, "[email protected]", 0);
+
+	struct Channel *chan = get_any_ready_channel();
+
+	if (chan) {
+		/* Channel requests are preferable, more implementations
+		handle them than SSH_MSG_GLOBAL_REQUEST */
+		TRACE(("keepalive channel request %d", chan->index))
+		start_send_channel_request(chan, DROPBEAR_KEEPALIVE_STRING);
+	} else {
+		TRACE(("keepalive global request"))
+		/* Some peers will reply with SSH_MSG_REQUEST_FAILURE, 
+		some will reply with SSH_MSG_UNIMPLEMENTED, some will exit. */
+		buf_putbyte(ses.writepayload, SSH_MSG_GLOBAL_REQUEST); 
+		buf_putstring(ses.writepayload, DROPBEAR_KEEPALIVE_STRING,
+			strlen(DROPBEAR_KEEPALIVE_STRING));
+	}
 	buf_putbyte(ses.writepayload, 1); /* want_reply */
 	encrypt_packet();
 
@@ -435,7 +446,10 @@ static void checktimeouts() {
 		send_msg_kexinit();
 	}
 	
-	if (opts.keepalive_secs > 0) {
+	if (opts.keepalive_secs > 0 && ses.authstate.authdone) {
+		/* Avoid sending keepalives prior to auth - those are
+		not valid pre-auth packet types */
+
 		/* Send keepalives if we've been idle */
 		if (now - ses.last_packet_time_any_sent >= opts.keepalive_secs) {
 			send_msg_keepalive();

session.h

@@ -47,7 +47,7 @@ void session_loop(void(*loophandler)());
 void session_cleanup();
 void send_session_identification();
 void send_msg_ignore();
-void ignore_recv_msg_request_failure();
+void ignore_recv_response();
 
 void update_channel_prio();
 

svr-chansession.c

@@ -53,6 +53,7 @@ static void sesssigchild_handler(int val);
 static void closechansess(struct Channel *channel);
 static int newchansess(struct Channel *channel);
 static void chansessionrequest(struct Channel *channel);
+static int sesscheckclose(struct Channel *channel);
 
 static void send_exitsignalstatus(struct Channel *channel);
 static void send_msg_chansess_exitstatus(struct Channel * channel,
@@ -61,6 +62,14 @@ static void send_msg_chansess_exitsignal(struct Channel * channel,
 		struct ChanSess * chansess);
 static void get_termmodes(struct ChanSess *chansess);
 
+const struct ChanType svrchansess = {
+	0, /* sepfds */
+	"session", /* name */
+	newchansess, /* inithandler */
+	sesscheckclose, /* checkclosehandler */
+	chansessionrequest, /* reqhandler */
+	closechansess, /* closehandler */
+};
 
 /* required to clear environment */
 extern char** environ;
@@ -968,16 +977,6 @@ static void execchild(void *user_data) {
 	dropbear_exit("Child failed");
 }
 
-const struct ChanType svrchansess = {
-	0, /* sepfds */
-	"session", /* name */
-	newchansess, /* inithandler */
-	sesscheckclose, /* checkclosehandler */
-	chansessionrequest, /* reqhandler */
-	closechansess, /* closehandler */
-};
-
-
 /* Set up the general chansession environment, in particular child-exit
  * handling */
 void svr_chansessinitialise() {

svr-main.c

@@ -409,7 +409,7 @@ static size_t listensockets(int *sock, size_t sockcount, int *maxfd) {
 	size_t sockpos = 0;
 	int nsock;
 
-	TRACE(("listensockets: %d to try\n", svr_opts.portcount))
+	TRACE(("listensockets: %d to try", svr_opts.portcount))
 
 	for (i = 0; i < svr_opts.portcount; i++) {
 

svr-session.c

@@ -58,7 +58,10 @@ static const packettype svr_packettypes[] = {
 	{SSH_MSG_CHANNEL_OPEN, recv_msg_channel_open},
 	{SSH_MSG_CHANNEL_EOF, recv_msg_channel_eof},
 	{SSH_MSG_CHANNEL_CLOSE, recv_msg_channel_close},
-	{SSH_MSG_REQUEST_FAILURE, ignore_recv_msg_request_failure}, /* for keepalive */
+	{SSH_MSG_CHANNEL_SUCCESS, ignore_recv_response},
+	{SSH_MSG_CHANNEL_FAILURE, ignore_recv_response},
+	{SSH_MSG_REQUEST_FAILURE, ignore_recv_response}, /* for keepalive */
+	{SSH_MSG_REQUEST_SUCCESS, ignore_recv_response}, /* client */
 #ifdef USING_LISTENERS
 	{SSH_MSG_CHANNEL_OPEN_CONFIRMATION, recv_msg_channel_open_confirmation},
 	{SSH_MSG_CHANNEL_OPEN_FAILURE, recv_msg_channel_open_failure},

sysoptions.h

@@ -257,4 +257,7 @@
 #define DROPBEAR_LISTEN_BACKLOG MAX_CHANNELS
 #endif
 
+/* Use this string since some implementations might special-case it */
+#define DROPBEAR_KEEPALIVE_STRING "[email protected]"
+
 /* no include guard for this file */