- djm@cvs.openbsd.org 2011/09/09 22:46:44

     [channels.c channels.h clientloop.h mux.c ssh.c]
     support for cancelling local and remote port forwards via the multiplex
     socket. Use ssh -O cancel -L xx:xx:xx -R yy:yy:yy user@host" to request
     the cancellation of the specified forwardings; ok markus@

1 files changed, 109 insertions, 55 deletions

diff --git a/channels.c b/channels.c
index 24d4a9f42..0f7e1a872 100644
--- a/channels.c
+++ b/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.311 2011/06/22 22:08:42 djm Exp $ */
+/* $OpenBSD: channels.c,v 1.312 2011/09/09 22:46:44 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -302,6 +302,8 @@ channel_new(char *ctype, int type, int rfd, int wfd, int efd,
         buffer_init(&c->output);
         buffer_init(&c->extended);
         c->path = NULL;
+        c->listening_addr = NULL;
+        c->listening_port = 0;
         c->ostate = CHAN_OUTPUT_OPEN;
         c->istate = CHAN_INPUT_OPEN;
         c->flags = 0;
@@ -411,6 +413,10 @@ channel_free(Channel *c)
                 xfree(c->path);
                 c->path = NULL;
         }
+        if (c->listening_addr) {
+                xfree(c->listening_addr);
+                c->listening_addr = NULL;
+        }
         while ((cc = TAILQ_FIRST(&c->status_confirms)) != NULL) {
                 if (cc->abandon_cb != NULL)
                         cc->abandon_cb(c, cc->ctx);
@@ -2634,6 +2640,46 @@ channel_set_af(int af)
         IPv4or6 = af;
 }
 
+
+/*
+ * Determine whether or not a port forward listens to loopback, the
+ * specified address or wildcard. On the client, a specified bind
+ * address will always override gateway_ports. On the server, a
+ * gateway_ports of 1 (``yes'') will override the client's specification
+ * and force a wildcard bind, whereas a value of 2 (``clientspecified'')
+ * will bind to whatever address the client asked for.
+ *
+ * Special-case listen_addrs are:
+ *
+ * "0.0.0.0"               -> wildcard v4/v6 if SSH_OLD_FORWARD_ADDR
+ * "" (empty string), "*"  -> wildcard v4/v6
+ * "localhost"             -> loopback v4/v6
+ */
+static const char *
+channel_fwd_bind_addr(const char *listen_addr, int *wildcardp,
+    int is_client, int gateway_ports)
+{
+        const char *addr = NULL;
+        int wildcard = 0;
+
+        if (listen_addr == NULL) {
+                /* No address specified: default to gateway_ports setting */
+                if (gateway_ports)
+                        wildcard = 1;
+        } else if (gateway_ports || is_client) {
+                if (((datafellows & SSH_OLD_FORWARD_ADDR) &&
+                    strcmp(listen_addr, "0.0.0.0") == 0 && is_client == 0) ||
+                    *listen_addr == '\0' || strcmp(listen_addr, "*") == 0 ||
+                    (!is_client && gateway_ports == 1))
+                        wildcard = 1;
+                else if (strcmp(listen_addr, "localhost") != 0)
+                        addr = listen_addr;
+        }
+        if (wildcardp != NULL)
+                *wildcardp = wildcard;
+        return addr;
+}
+
 static int
 channel_setup_fwd_listener(int type, const char *listen_addr,
     u_short listen_port, int *allocated_listen_port,
@@ -2659,36 +2705,9 @@ channel_setup_fwd_listener(int type, const char *listen_addr,
                 return 0;
         }
 
-        /*
-         * Determine whether or not a port forward listens to loopback,
-         * specified address or wildcard. On the client, a specified bind
-         * address will always override gateway_ports. On the server, a
-         * gateway_ports of 1 (``yes'') will override the client's
-         * specification and force a wildcard bind, whereas a value of 2
-         * (``clientspecified'') will bind to whatever address the client
-         * asked for.
-         *
-         * Special-case listen_addrs are:
-         *
-         * "0.0.0.0"               -> wildcard v4/v6 if SSH_OLD_FORWARD_ADDR
-         * "" (empty string), "*"  -> wildcard v4/v6
-         * "localhost"             -> loopback v4/v6
-         */
-        addr = NULL;
-        if (listen_addr == NULL) {
-                /* No address specified: default to gateway_ports setting */
-                if (gateway_ports)
-                        wildcard = 1;
-        } else if (gateway_ports || is_client) {
-                if (((datafellows & SSH_OLD_FORWARD_ADDR) &&
-                    strcmp(listen_addr, "0.0.0.0") == 0 && is_client == 0) ||
-                    *listen_addr == '\0' || strcmp(listen_addr, "*") == 0 ||
-                    (!is_client && gateway_ports == 1))
-                        wildcard = 1;
-                else if (strcmp(listen_addr, "localhost") != 0)
-                        addr = listen_addr;
-        }
-
+        /* Determine the bind address, cf. channel_fwd_bind_addr() comment */
+        addr = channel_fwd_bind_addr(listen_addr, &wildcard,
+            is_client, gateway_ports);
         debug3("channel_setup_fwd_listener: type %d wildcard %d addr %s",
             type, wildcard, (addr == NULL) ? "NULL" : addr);
 
@@ -2793,6 +2812,7 @@ channel_setup_fwd_listener(int type, const char *listen_addr,
                 c->path = xstrdup(host);
                 c->host_port = port_to_connect;
                 c->listening_port = listen_port;
+                c->listening_addr = addr == NULL ? NULL : xstrdup(addr);
                 success = 1;
         }
         if (success == 0)
@@ -2810,9 +2830,36 @@ channel_cancel_rport_listener(const char *host, u_short port)
 
         for (i = 0; i < channels_alloc; i++) {
                 Channel *c = channels[i];
+                if (c == NULL || c->type != SSH_CHANNEL_RPORT_LISTENER)
+                        continue;
+                if (strcmp(c->path, host) == 0 && c->listening_port == port) {
+                        debug2("%s: close channel %d", __func__, i);
+                        channel_free(c);
+                        found = 1;
+                }
+        }
+
+        return (found);
+}
+
+int
+channel_cancel_lport_listener(const char *lhost, u_short lport,
+    u_short cport, int gateway_ports)
+{
+        u_int i;
+        int found = 0;
+        const char *addr = channel_fwd_bind_addr(lhost, NULL, 1, gateway_ports);
 
-                if (c != NULL && c->type == SSH_CHANNEL_RPORT_LISTENER &&
-                    strcmp(c->path, host) == 0 && c->listening_port == port) {
+        for (i = 0; i < channels_alloc; i++) {
+                Channel *c = channels[i];
+                if (c == NULL || c->type != SSH_CHANNEL_PORT_LISTENER)
+                        continue;
+                if (c->listening_port != lport || c->host_port != cport)
+                        continue;
+                if ((c->listening_addr == NULL && addr != NULL) ||
+                    (c->listening_addr != NULL && addr == NULL))
+                        continue;
+                if (addr == NULL || strcmp(c->listening_addr, addr) == 0) {
                         debug2("%s: close channel %d", __func__, i);
                         channel_free(c);
                         found = 1;
@@ -2843,10 +2890,30 @@ channel_setup_remote_fwd_listener(const char *listen_address,
 }
 
 /*
+ * Translate the requested rfwd listen host to something usable for
+ * this server.
+ */
+static const char *
+channel_rfwd_bind_host(const char *listen_host)
+{
+        if (listen_host == NULL) {
+                if (datafellows & SSH_BUG_RFWD_ADDR)
+                        return "127.0.0.1";
+                else
+                        return "localhost";
+        } else if (*listen_host == '\0' || strcmp(listen_host, "*") == 0) {
+                if (datafellows & SSH_BUG_RFWD_ADDR)
+                        return "0.0.0.0";
+                else
+                        return "";
+        } else
+                return listen_host;
+}
+
+/*
  * Initiate forwarding of connections to port "port" on remote host through
  * the secure channel to host:port from local side.
  */
-
 int
 channel_request_remote_forwarding(const char *listen_host, u_short listen_port,
     const char *host_to_connect, u_short port_to_connect)
@@ -2855,25 +2922,10 @@ channel_request_remote_forwarding(const char *listen_host, u_short listen_port,
 
         /* Send the forward request to the remote side. */
         if (compat20) {
-                const char *address_to_bind;
-                if (listen_host == NULL) {
-                        if (datafellows & SSH_BUG_RFWD_ADDR)
-                                address_to_bind = "127.0.0.1";
-                        else
-                                address_to_bind = "localhost";
-                } else if (*listen_host == '\0' ||
-                           strcmp(listen_host, "*") == 0) {
-                        if (datafellows & SSH_BUG_RFWD_ADDR)
-                                address_to_bind = "0.0.0.0";
-                        else
-                                address_to_bind = "";
-                } else
-                        address_to_bind = listen_host;
-
                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
                 packet_put_cstring("tcpip-forward");
-                packet_put_char(1);                     /* boolean: want reply */
-                packet_put_cstring(address_to_bind);
+                packet_put_char(1);             /* boolean: want reply */
+                packet_put_cstring(channel_rfwd_bind_host(listen_host));
                 packet_put_int(listen_port);
                 packet_send();
                 packet_write_wait();
@@ -2917,13 +2969,13 @@ channel_request_remote_forwarding(const char *listen_host, u_short listen_port,
  * Request cancellation of remote forwarding of connection host:port from
  * local side.
  */
-void
+int
 channel_request_rforward_cancel(const char *host, u_short port)
 {
         int i;
 
         if (!compat20)
-                return;
+                return -1;
 
         for (i = 0; i < num_permitted_opens; i++) {
                 if (permitted_opens[i].host_to_connect != NULL &&
@@ -2932,12 +2984,12 @@ channel_request_rforward_cancel(const char *host, u_short port)
         }
         if (i >= num_permitted_opens) {
                 debug("%s: requested forward not found", __func__);
-                return;
+                return -1;
         }
         packet_start(SSH2_MSG_GLOBAL_REQUEST);
         packet_put_cstring("cancel-tcpip-forward");
         packet_put_char(0);
-        packet_put_cstring(host == NULL ? "" : host);
+        packet_put_cstring(channel_rfwd_bind_host(host));
         packet_put_int(port);
         packet_send();
 
@@ -2945,6 +2997,8 @@ channel_request_rforward_cancel(const char *host, u_short port)
         permitted_opens[i].port_to_connect = 0;
         xfree(permitted_opens[i].host_to_connect);
         permitted_opens[i].host_to_connect = NULL;
+
+        return 0;
 }
 
 /*