Implement `portfwd-loopback-choice'. Works on local side in Unix as

well, though it's a lot less useful since you still can't bind to
low-numbered ports of odd loopback IPs. Should work in principle for
SSH2 remote forwardings as well as local ones, but OpenSSH seems
unwilling to cooperate.

[originally from svn r2344]

cmdline.c

@@ -160,7 +160,7 @@ int cmdline_process_param(char *p, char *value, int need_save)
 	cfg.username[sizeof(cfg.username) - 1] = '\0';
     }
     if ((!strcmp(p, "-L") || !strcmp(p, "-R"))) {
-	char *fwd, *ptr, *q;
+	char *fwd, *ptr, *q, *qq;
 	int i=0;
 	RETURN(2);
 	UNAVAILABLE_IN(TOOLTYPE_FILETRANSFER);
@@ -180,8 +180,23 @@ int cmdline_process_param(char *p, char *value, int need_save)
 	    return ret;
 	}
 	strncpy(ptr+1, fwd, sizeof(cfg.portfwd) - i);
-	q = strchr(ptr, ':');
+	/*
-	if (q) *q = '\t';      /* replace first : with \t */
+	 * We expect _at least_ two colons in this string. The
+	 * possible formats are `sourceport:desthost:destport', or
+	 * `sourceip:sourceport:desthost:destport' if you're
+	 * specifying a particular loopback address. We need to
+	 * replace the one between source and dest with a \t; this
+	 * means we must find the second-to-last colon in the
+	 * string.
+	 */
+	q = qq = strchr(ptr, ':');
+	while (qq) {
+	    char *qqq = strchr(qq+1, ':');
+	    if (qqq)
+		q = qq;
+	    qq = qqq;
+	}
+	if (q) *q = '\t';	       /* replace second-last colon with \t */
 	cfg.portfwd[sizeof(cfg.portfwd) - 1] = '\0';
 	cfg.portfwd[sizeof(cfg.portfwd) - 2] = '\0';
 	ptr[strlen(ptr)+1] = '\000';    /* append two '\000' */

doc/config.but

@@ -1,4 +1,4 @@
-\versionid $Id: config.but,v 1.44 2002/10/22 09:40:38 simon Exp $
+\versionid $Id: config.but,v 1.45 2002/12/18 11:39:25 simon Exp $
 
 \C{config} Configuring PuTTY
 
@@ -1881,6 +1881,19 @@ in the list box.
 To remove a port forwarding, simply select its details in the list
 box, and click the \q{Remove} button.
 
+In the \q{Source port} box, you can also optionally enter an IP
+address to listen on. Typically a Windows machine can be asked to
+listen on any single IP address in the \cw{127.*.*.*} range, and all
+of these are loopback addresses available only to the local machine.
+So if you forward (for example) \c{127.0.0.5:79} to a remote
+machine's \cw{finger} port, then you should be able to run commands
+such as \c{finger fred@127.0.0.5}. This can be useful if the program
+connecting to the forwarded port doesn't allow you to change the
+port number it uses. This feature is available for local-to-remote
+forwarded ports; SSH1 is unable to support it for remote-to-local
+ports, while SSH2 can support it in theory but servers will not
+necessarily cooperate.
+
 \S{config-ssh-portfwd-localhost} Controlling the visibility of
 forwarded ports
 

doc/using.but

@@ -1,4 +1,4 @@
-\versionid $Id: using.but,v 1.8 2002/09/11 17:30:36 jacob Exp $
+\versionid $Id: using.but,v 1.9 2002/12/18 11:39:25 simon Exp $
 
 \C{using} Using PuTTY
 
@@ -254,7 +254,8 @@ to a port on a remote server, you need to:
 
 \b Choose a port number on your local machine where PuTTY should
 listen for incoming connections. There are likely to be plenty of
-unused port numbers above 3000.
+unused port numbers above 3000. (You can also use a local loopback
+address here; see \k{config-ssh-portfwd} for more details.)
 
 \b Now, before you start your SSH connection, go to the Tunnels
 panel (see \k{config-ssh-portfwd}). Make sure the \q{Local} radio

network.h

@@ -67,7 +67,7 @@ struct plug_function_table {
 Socket new_connection(SockAddr addr, char *hostname,
 		      int port, int privport,
 		      int oobinline, int nodelay, Plug plug);
-Socket new_listener(int port, Plug plug, int local_host_only);
+Socket new_listener(char *srcaddr, int port, Plug plug, int local_host_only);
 
 /* socket functions */
 
@@ -84,7 +84,7 @@ void sk_addr_free(SockAddr addr);
 Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
 	      int nodelay, Plug p);
 
-Socket sk_newlistener(int port, Plug plug, int local_host_only);
+Socket sk_newlistener(char *srcaddr, int port, Plug plug, int local_host_only);
 
 Socket sk_register(void *sock, Plug plug);
 

portfwd.c

@@ -203,9 +203,10 @@ static int pfd_accepting(Plug p, void *sock)
 
 
 /* Add a new forwarding from port -> desthost:destport
- sets up a listener on the local machine on port
+ sets up a listener on the local machine on (srcaddr:)port
  */
-char *pfd_addforward(char *desthost, int destport, int port, void *backhandle)
+char *pfd_addforward(char *desthost, int destport, char *srcaddr, int port,
+		     void *backhandle)
 {
     static struct plug_function_table fn_table = {
 	pfd_closing,
@@ -231,7 +232,7 @@ char *pfd_addforward(char *desthost, int destport, int port, void *backhandle)
     pr->waiting = NULL;
     pr->backhandle = backhandle;
 
-    pr->s = s = new_listener(port, (Plug) pr, !cfg.lport_acceptall);
+    pr->s = s = new_listener(srcaddr, port, (Plug) pr, !cfg.lport_acceptall);
     if ((err = sk_socket_error(s))) {
 	sfree(pr);
 	return err;

proxy.c

@@ -404,13 +404,13 @@ Socket new_connection(SockAddr addr, char *hostname,
     return sk_new(addr, port, privport, oobinline, nodelay, plug);
 }
 
-Socket new_listener(int port, Plug plug, int local_host_only)
+Socket new_listener(char *srcaddr, int port, Plug plug, int local_host_only)
 {
     /* TODO: SOCKS (and potentially others) support inbound
      * TODO: connections via the proxy. support them.
      */
 
-    return sk_newlistener(port, plug, local_host_only);
+    return sk_newlistener(srcaddr, port, plug, local_host_only);
 }
 
 /* ----------------------------------------------------------------------

ssh.c

@@ -299,8 +299,8 @@ extern void x11_unthrottle(Socket s);
 extern void x11_override_throttle(Socket s, int enable);
 
 extern char *pfd_newconnect(Socket * s, char *hostname, int port, void *c);
-extern char *pfd_addforward(char *desthost, int destport, int port,
+extern char *pfd_addforward(char *desthost, int destport, char *srcaddr,
-			    void *backhandle);
+			    int port, void *backhandle);
 extern void pfd_close(Socket s);
 extern int pfd_send(Socket s, char *data, int len);
 extern void pfd_confirm(Socket s);
@@ -3071,28 +3071,46 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 	char type;
 	int n;
 	int sport,dport,sserv,dserv;
-	char sports[256], dports[256], host[256];
+	char sports[256], dports[256], saddr[256], host[256];
 
 	ssh->rportfwds = newtree234(ssh_rportcmp_ssh1);
         /* Add port forwardings. */
 	ssh->portfwd_strptr = cfg.portfwd;
 	while (*ssh->portfwd_strptr) {
 	    type = *ssh->portfwd_strptr++;
+	    saddr[0] = '\0';
 	    n = 0;
-	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t')
+	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t') {
-		sports[n++] = *ssh->portfwd_strptr++;
+		if (*ssh->portfwd_strptr == ':') {
+		    /*
+		     * We've seen a colon in the middle of the
+		     * source port number. This means that
+		     * everything we've seen until now is the
+		     * source _address_, so we'll move it into
+		     * saddr and start sports from the beginning
+		     * again.
+		     */
+		    ssh->portfwd_strptr++;
+		    sports[n] = '\0';
+		    strcpy(saddr, sports);
+		    n = 0;
+		}
+		if (n < 255) sports[n++] = *ssh->portfwd_strptr++;
+	    }
 	    sports[n] = 0;
 	    if (*ssh->portfwd_strptr == '\t')
 		ssh->portfwd_strptr++;
 	    n = 0;
-	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':')
+	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':') {
-		host[n++] = *ssh->portfwd_strptr++;
+		if (n < 255) host[n++] = *ssh->portfwd_strptr++;
+	    }
 	    host[n] = 0;
 	    if (*ssh->portfwd_strptr == ':')
 		ssh->portfwd_strptr++;
 	    n = 0;
-	    while (*ssh->portfwd_strptr)
+	    while (*ssh->portfwd_strptr) {
-		dports[n++] = *ssh->portfwd_strptr++;
+		if (n < 255) dports[n++] = *ssh->portfwd_strptr++;
+	    }
 	    dports[n] = 0;
 	    ssh->portfwd_strptr++;
 	    dport = atoi(dports);
@@ -3117,9 +3135,12 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 	    }
 	    if (sport && dport) {
 		if (type == 'L') {
-		    pfd_addforward(host, dport, sport, ssh);
+		    pfd_addforward(host, dport, *saddr ? saddr : NULL,
-		    logeventf(ssh, "Local port %.*s%.*s%d%.*s forwarding to"
+				   sport, ssh);
-			      " %s:%.*s%.*s%d%.*s",
+		    logeventf(ssh, "Local port %.*s%.*s%.*s%.*s%d%.*s"
+			      " forwarding to %s:%.*s%.*s%d%.*s",
+			      (int)(*saddr?strlen(saddr):0), *saddr?saddr:NULL,
+			      (int)(*saddr?1:0), ":",
 			      (int)(sserv ? strlen(sports) : 0), sports,
 			      sserv, "(", sport, sserv, ")",
 			      host,
@@ -3130,6 +3151,11 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 		    pf = smalloc(sizeof(*pf));
 		    strcpy(pf->dhost, host);
 		    pf->dport = dport;
+		    if (saddr) {
+			logeventf(ssh,
+				  "SSH1 cannot handle source address spec \"%s:%d\"; ignoring",
+				  saddr, sport);
+		    }
 		    if (add234(ssh->rportfwds, pf) != pf) {
 			logeventf(ssh, 
 				  "Duplicate remote port forwarding to %s:%d",
@@ -5102,28 +5128,46 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 	char type;
 	int n;
 	int sport,dport,sserv,dserv;
-	char sports[256], dports[256], host[256];
+	char sports[256], dports[256], saddr[256], host[256];
 
 	ssh->rportfwds = newtree234(ssh_rportcmp_ssh2);
         /* Add port forwardings. */
 	ssh->portfwd_strptr = cfg.portfwd;
 	while (*ssh->portfwd_strptr) {
 	    type = *ssh->portfwd_strptr++;
+	    saddr[0] = '\0';
 	    n = 0;
-	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t')
+	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t') {
-		sports[n++] = *ssh->portfwd_strptr++;
+		if (*ssh->portfwd_strptr == ':') {
+		    /*
+		     * We've seen a colon in the middle of the
+		     * source port number. This means that
+		     * everything we've seen until now is the
+		     * source _address_, so we'll move it into
+		     * saddr and start sports from the beginning
+		     * again.
+		     */
+		    ssh->portfwd_strptr++;
+		    sports[n] = '\0';
+		    strcpy(saddr, sports);
+		    n = 0;
+		}
+		if (n < 255) sports[n++] = *ssh->portfwd_strptr++;
+	    }
 	    sports[n] = 0;
 	    if (*ssh->portfwd_strptr == '\t')
 		ssh->portfwd_strptr++;
 	    n = 0;
-	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':')
+	    while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':') {
-		host[n++] = *ssh->portfwd_strptr++;
+		if (n < 255) host[n++] = *ssh->portfwd_strptr++;
+	    }
 	    host[n] = 0;
 	    if (*ssh->portfwd_strptr == ':')
 		ssh->portfwd_strptr++;
 	    n = 0;
-	    while (*ssh->portfwd_strptr)
+	    while (*ssh->portfwd_strptr) {
-		dports[n++] = *ssh->portfwd_strptr++;
+		if (n < 255) dports[n++] = *ssh->portfwd_strptr++;
+	    }
 	    dports[n] = 0;
 	    ssh->portfwd_strptr++;
 	    dport = atoi(dports);
@@ -5148,9 +5192,12 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 	    }
 	    if (sport && dport) {
 		if (type == 'L') {
-		    pfd_addforward(host, dport, sport, ssh);
+		    pfd_addforward(host, dport, *saddr ? saddr : NULL,
-		    logeventf(ssh, "Local port %.*s%.*s%d%.*s forwarding to"
+				   sport, ssh);
-			      " %s:%.*s%.*s%d%.*s",
+		    logeventf(ssh, "Local port %.*s%.*s%.*s%.*s%d%.*s"
+			      " forwarding to %s:%.*s%.*s%d%.*s",
+			      (int)(*saddr?strlen(saddr):0), *saddr?saddr:NULL,
+			      (int)(*saddr?1:0), ":",
 			      (int)(sserv ? strlen(sports) : 0), sports,
 			      sserv, "(", sport, sserv, ")",
 			      host,
@@ -5167,8 +5214,12 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 				  " to %s:%d", host, dport);
 			sfree(pf);
 		    } else {
-			logeventf(ssh, "Requesting remote port %.*s%.*s%d%.*s"
+			logeventf(ssh, "Requesting remote port "
+				  "%.*s%.*s%.*s%.*s%d%.*s"
 				  " forward to %s:%.*s%.*s%d%.*s",
+				  (int)(*saddr?strlen(saddr):0),
+				  *saddr?saddr:NULL,
+				  (int)(*saddr?1:0), ":",
 				  (int)(sserv ? strlen(sports) : 0), sports,
 				  sserv, "(", sport, sserv, ")",
 				  host,
@@ -5177,6 +5228,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 			ssh2_pkt_init(ssh, SSH2_MSG_GLOBAL_REQUEST);
 			ssh2_pkt_addstring(ssh, "tcpip-forward");
 			ssh2_pkt_addbool(ssh, 1);/* want reply */
+			if (*saddr)
+			    ssh2_pkt_addstring(ssh, saddr);
 			if (cfg.rport_acceptall)
 			    ssh2_pkt_addstring(ssh, "0.0.0.0");
 			else

unix/uxnet.c

@@ -21,6 +21,8 @@
 #include "network.h"
 #include "tree234.h"
 
+#define ipv4_is_loopback(addr) (inet_netof(addr) == IN_LOOPBACKNET)
+
 struct Socket_tag {
     struct socket_function_table *fn;
     /* the above variable absolutely *must* be the first in this structure */
@@ -474,7 +476,7 @@ Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
     return (Socket) ret;
 }
 
-Socket sk_newlistener(int port, Plug plug, int local_host_only)
+Socket sk_newlistener(char *srcaddr, int port, Plug plug, int local_host_only)
 {
     static struct socket_function_table fn_table = {
 	sk_tcp_plug,
@@ -534,6 +536,8 @@ Socket sk_newlistener(int port, Plug plug, int local_host_only)
     if (addr->family == AF_INET6) {
 	memset(&a6, 0, sizeof(a6));
 	a6.sin6_family = AF_INET6;
+	/* FIXME: srcaddr is ignored for IPv6, because I (SGT) don't
+	 * know how to do it. :-) */
 	if (local_host_only)
 	    a6.sin6_addr = in6addr_loopback;
 	else
@@ -542,11 +546,32 @@ Socket sk_newlistener(int port, Plug plug, int local_host_only)
     } else
 #endif
     {
+	int got_addr = 0;
 	a.sin_family = AF_INET;
+
+	/*
+	 * Bind to source address. First try an explicitly
+	 * specified one...
+	 */
+	if (srcaddr) {
+	    a.sin_addr.s_addr = inet_addr(srcaddr);
+	    if (a.sin_addr.s_addr != INADDR_NONE) {
+		/* Override localhost_only with specified listen addr. */
+		ret->localhost_only = ipv4_is_loopback(a.sin_addr);
+		got_addr = 1;
+	    }
+	}
+
+	/*
+	 * ... and failing that, go with one of the standard ones.
+	 */
+	if (!got_addr) {
 	    if (local_host_only)
 		a.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 	    else
 		a.sin_addr.s_addr = htonl(INADDR_ANY);
+	}
+
 	a.sin_port = htons((short)port);
     }
 #ifdef IPV6
@@ -763,8 +788,7 @@ int select_result(int fd, int event)
 		break;
 	    }
 
-	    if (s->localhost_only &&
+	    if (s->localhost_only && !ipv4_is_loopback(isa.sin_addr)) {
-		ntohl(isa.sin_addr.s_addr) != INADDR_LOOPBACK) {
 		close(t);	       /* someone let nonlocal through?! */
 	    } else if (plug_accepting(s->plug, (void*)t)) {
 		close(t);	       /* denied or error */

winnet.c

@@ -55,6 +55,9 @@
 #include "network.h"
 #include "tree234.h"
 
+#define ipv4_is_loopback(addr) \
+	((ntohl(addr.s_addr) & 0xFF000000L) == 0x7F000000L)
+
 struct Socket_tag {
     struct socket_function_table *fn;
     /* the above variable absolutely *must* be the first in this structure */
@@ -654,7 +657,7 @@ Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
     return (Socket) ret;
 }
 
-Socket sk_newlistener(int port, Plug plug, int local_host_only)
+Socket sk_newlistener(char *srcaddr, int port, Plug plug, int local_host_only)
 {
     static struct socket_function_table fn_table = {
 	sk_tcp_plug,
@@ -716,6 +719,8 @@ Socket sk_newlistener(int port, Plug plug, int local_host_only)
 	if (addr->family == AF_INET6) {
 	    memset(&a6, 0, sizeof(a6));
 	    a6.sin6_family = AF_INET6;
+	    /* FIXME: srcaddr is ignored for IPv6, because I (SGT) don't
+	     * know how to do it. :-) */
 	    if (local_host_only)
 		a6.sin6_addr = in6addr_loopback;
 	    else
@@ -724,11 +729,32 @@ Socket sk_newlistener(int port, Plug plug, int local_host_only)
 	} else
 #endif
 	{
+	    int got_addr = 0;
 	    a.sin_family = AF_INET;
+
+	    /*
+	     * Bind to source address. First try an explicitly
+	     * specified one...
+	     */
+	    if (srcaddr) {
+		a.sin_addr.s_addr = inet_addr(srcaddr);
+		if (a.sin_addr.s_addr != INADDR_NONE) {
+		    /* Override localhost_only with specified listen addr. */
+		    ret->localhost_only = ipv4_is_loopback(a.sin_addr);
+		    got_addr = 1;
+		}
+	    }
+
+	    /*
+	     * ... and failing that, go with one of the standard ones.
+	     */
+	    if (!got_addr) {
 		if (local_host_only)
 		    a.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 		else
 		    a.sin_addr.s_addr = htonl(INADDR_ANY);
+	    }
+
 	    a.sin_port = htons((short)port);
 	}
 #ifdef IPV6
@@ -1047,8 +1073,7 @@ int select_result(WPARAM wParam, LPARAM lParam)
 		    break;
 	    }
 
-	    if (s->localhost_only &&
+	    if (s->localhost_only && !ipv4_is_loopback(isa.sin_addr)) {
-		ntohl(isa.sin_addr.s_addr) != INADDR_LOOPBACK) {
 		closesocket(t);	       /* dodgy WinSock let nonlocal through */
 	    } else if (plug_accepting(s->plug, (void*)t)) {
 		closesocket(t);	       /* denied or error */