upstream commit

Return true reason for port forwarding failures where
feasible rather than always "administratively prohibited".  bz#2674, ok djm@

Upstream-ID: d901d9887951774e604ca970e1827afaaef9e419

3 files changed, 39 insertions, 16 deletions

diff --git a/channels.c b/channels.c
index bef8ad6aa..398da9a89 100644
--- a/channels.c
+++ b/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.356 2016/10/18 17:32:54 dtucker Exp $ */
+/* $OpenBSD: channels.c,v 1.357 2017/02/01 02:59:09 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -3065,7 +3065,7 @@ channel_input_port_open(int type, u_int32_t seq, void *ctxt)
 	}
 	packet_check_eom();
 	c = channel_connect_to_port(host, host_port,
-	    "connected socket", originator_string);
+	    "connected socket", originator_string, NULL, NULL);
 	free(originator_string);
 	free(host);
 	if (c == NULL) {
@@ -4026,9 +4026,13 @@ channel_connect_ctx_free(struct channel_connect *cctx)
 	memset(cctx, 0, sizeof(*cctx));
 }
 
-/* Return CONNECTING channel to remote host:port or local socket path */
+/*
+ * Return CONNECTING channel to remote host:port or local socket path,
+ * passing back the failure reason if appropriate.
+ */
 static Channel *
-connect_to(const char *name, int port, char *ctype, char *rname)
+connect_to_reason(const char *name, int port, char *ctype, char *rname,
+     int *reason, const char **errmsg)
 {
 	struct addrinfo hints;
 	int gaierr;
@@ -4069,7 +4073,12 @@ connect_to(const char *name, int port, char *ctype, char *rname)
 		hints.ai_family = IPv4or6;
 		hints.ai_socktype = SOCK_STREAM;
 		snprintf(strport, sizeof strport, "%d", port);
-		if ((gaierr = getaddrinfo(name, strport, &hints, &cctx.aitop)) != 0) {
+		if ((gaierr = getaddrinfo(name, strport, &hints, &cctx.aitop))
+		    != 0) {
+			if (errmsg != NULL)
+				*errmsg = ssh_gai_strerror(gaierr);
+			if (reason != NULL)
+				*reason = SSH2_OPEN_CONNECT_FAILED;
 			error("connect_to %.100s: unknown host (%s)", name,
 			    ssh_gai_strerror(gaierr));
 			return NULL;
@@ -4092,6 +4101,13 @@ connect_to(const char *name, int port, char *ctype, char *rname)
 	return c;
 }
 
+/* Return CONNECTING channel to remote host:port or local socket path */
+static Channel *
+connect_to(const char *name, int port, char *ctype, char *rname)
+{
+	return connect_to_reason(name, port, ctype, rname, NULL, NULL);
+}
+
 /*
  * returns either the newly connected channel or the downstream channel
  * that needs to deal with this connection.
@@ -4136,7 +4152,8 @@ channel_connect_by_listen_path(const char *path, char *ctype, char *rname)
 
 /* Check if connecting to that port is permitted and connect. */
 Channel *
-channel_connect_to_port(const char *host, u_short port, char *ctype, char *rname)
+channel_connect_to_port(const char *host, u_short port, char *ctype,
+    char *rname, int *reason, const char **errmsg)
 {
 	int i, permit, permit_adm = 1;
 
@@ -4161,9 +4178,11 @@ channel_connect_to_port(const char *host, u_short port, char *ctype, char *rname
 	if (!permit || !permit_adm) {
 		logit("Received request to connect to host %.100s port %d, "
 		    "but the request was denied.", host, port);
+		if (reason != NULL)
+			*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
 		return NULL;
 	}
-	return connect_to(host, port, ctype, rname);
+	return connect_to_reason(host, port, ctype, rname, reason, errmsg);
 }
 
 /* Check if connecting to that path is permitted and connect. */
diff --git a/channels.h b/channels.h
index 09c3c3655..ce43236d5 100644
--- a/channels.h
+++ b/channels.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.h,v 1.120 2016/10/18 17:32:54 dtucker Exp $ */
+/* $OpenBSD: channels.h,v 1.121 2017/02/01 02:59:09 dtucker Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -275,7 +275,8 @@ void	 channel_update_permitted_opens(int, int);
 void	 channel_clear_permitted_opens(void);
 void	 channel_clear_adm_permitted_opens(void);
 void 	 channel_print_adm_permitted_opens(void);
-Channel	*channel_connect_to_port(const char *, u_short, char *, char *);
+Channel	*channel_connect_to_port(const char *, u_short, char *, char *, int *,
+	     const char **);
 Channel *channel_connect_to_path(const char *, char *, char *);
 Channel	*channel_connect_stdio_fwd(const char*, u_short, int, int);
 Channel	*channel_connect_by_listen_address(const char *, u_short,
diff --git a/serverloop.c b/serverloop.c
index bdb944fa3..2976f5594 100644
--- a/serverloop.c
+++ b/serverloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: serverloop.c,v 1.190 2017/01/04 05:37:40 djm Exp $ */
+/* $OpenBSD: serverloop.c,v 1.191 2017/02/01 02:59:09 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -430,7 +430,7 @@ server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 }
 
 static Channel *
-server_request_direct_tcpip(void)
+server_request_direct_tcpip(int *reason, const char **errmsg)
 {
 	Channel *c = NULL;
 	char *target, *originator;
@@ -449,11 +449,13 @@ server_request_direct_tcpip(void)
 	if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
 	    !no_port_forwarding_flag && !options.disable_forwarding) {
 		c = channel_connect_to_port(target, target_port,
-		    "direct-tcpip", "direct-tcpip");
+		    "direct-tcpip", "direct-tcpip", reason, errmsg);
 	} else {
 		logit("refused local port forward: "
 		    "originator %s port %d, target %s port %d",
 		    originator, originator_port, target, target_port);
+		if (reason != NULL)
+			*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
 	}
 
 	free(originator);
@@ -581,7 +583,8 @@ server_input_channel_open(int type, u_int32_t seq, void *ctxt)
 {
 	Channel *c = NULL;
 	char *ctype;
-	int rchan;
+	const char *errmsg = NULL;
+	int rchan, reason = SSH2_OPEN_CONNECT_FAILED;
 	u_int rmaxpack, rwindow, len;
 
 	ctype = packet_get_string(&len);
@@ -595,7 +598,7 @@ server_input_channel_open(int type, u_int32_t seq, void *ctxt)
 	if (strcmp(ctype, "session") == 0) {
 		c = server_request_session();
 	} else if (strcmp(ctype, "direct-tcpip") == 0) {
-		c = server_request_direct_tcpip();
+		c = server_request_direct_tcpip(&reason, &errmsg);
 	} else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
 		c = server_request_direct_streamlocal();
 	} else if (strcmp(ctype, "tun@openssh.com") == 0) {
@@ -618,9 +621,9 @@ server_input_channel_open(int type, u_int32_t seq, void *ctxt)
 		debug("server_input_channel_open: failure %s", ctype);
 		packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 		packet_put_int(rchan);
-		packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
+		packet_put_int(reason);
 		if (!(datafellows & SSH_BUG_OPENFAILURE)) {
-			packet_put_cstring("open failed");
+			packet_put_cstring(errmsg ? errmsg : "open failed");
 			packet_put_cstring("");
 		}
 		packet_send();