socks5 support for -D

[Markus Friedl]

here's an up-to-date patch, should apply to both
openbsd and non-openbsd versions of openssh.

i did only test ipv4 addresses.

Index: channels.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/channels.c,v
retrieving revision 1.191
diff -u -r1.191 channels.c
--- channels.c	24 Jun 2003 08:23:46 -0000	1.191
+++ channels.c	25 Jun 2003 12:14:19 -0000
@@ -54,7 +54,7 @@
 #include "key.h"
 #include "authfd.h"
 #include "pathnames.h"
-
+#include "bufaux.h"
 
 /* -- channel core */
 
@@ -940,6 +940,115 @@
 	return 1;
 }
 
+/* try to decode a socks5 header */
+#define SSH_SOCKS5_AUTHDONE	0x1000
+#define SSH_SOCKS5_NOAUTH	0x00
+#define SSH_SOCKS5_IPV4		0x01
+#define SSH_SOCKS5_DOMAIN	0x03
+#define SSH_SOCKS5_IPV6		0x04
+#define SSH_SOCKS5_CONNECT	0x01
+#define SSH_SOCKS5_SUCCESS	0x00
+
+static int
+channel_decode_socks5(Channel *c, fd_set * readset, fd_set * writeset)
+{
+	struct {
+		u_int8_t version;
+		u_int8_t command;
+		u_int8_t reserved;
+		u_int8_t atyp;
+	} s5_req, s5_rsp;
+	u_int16_t dest_port;
+	u_char *p, dest_addr[255+1];
+	int i, have, found, nmethods, addrlen, af;
+
+	debug2("channel %d: decode socks5", c->self);
+	p = buffer_ptr(&c->input);
+	if (p[0] != 0x05)
+		return -1;
+	have = buffer_len(&c->input);
+	if (!(c->flags & SSH_SOCKS5_AUTHDONE)) {
+		/* format: ver | nmethods | methods */
+		if (have < 2) 
+			return 0;
+		nmethods = p[1];
+		if (have < nmethods + 2)
+			return 0;
+		/* look for method: "NO AUTHENTICATION REQUIRED" */
+		for (found = 0, i = 2 ; i < nmethods + 2; i++) {
+			if (p[i] == SSH_SOCKS5_NOAUTH ) {
+				found = 1;
+				break;
+			}
+		}
+		if (!found) {
+			debug("channel %d: method SSH_SOCKS5_NOAUTH not found",
+			    c->self);
+			return -1;
+		}
+		buffer_consume(&c->input, nmethods + 2);
+		buffer_put_char(&c->output, 0x05);		/* version */
+		buffer_put_char(&c->output, SSH_SOCKS5_NOAUTH);	/* method */
+		FD_SET(c->sock, writeset);
+		c->flags |= SSH_SOCKS5_AUTHDONE;
+		debug2("channel %d: socks5 auth done", c->self);
+		return 0;				/* need more */
+	}
+	debug2("channel %d: socks5 post auth", c->self);
+	if (have < sizeof(s5_req)+1)
+		return 0;			/* need more */
+	memcpy((char *)&s5_req, p, sizeof(s5_req));
+	if (s5_req.version != 0x05 ||
+	    s5_req.command != SSH_SOCKS5_CONNECT ||
+	    s5_req.reserved != 0x00) {
+		debug("channel %d: only socks5 connect supported", c->self);
+		return -1;
+	}
+	switch(s5_req.atyp){
+	case SSH_SOCKS5_IPV4:
+		addrlen = 4;
+		af = AF_INET;
+		break;
+	case SSH_SOCKS5_DOMAIN:
+		addrlen = p[sizeof(s5_req)];
+		af = -1;
+		break;
+	case SSH_SOCKS5_IPV6:
+		addrlen = 16;
+		af = AF_INET6;
+		break;
+	default:
+		debug("channel %d: bad socks5 atyp %d", c->self, s5_req.atyp);
+		return -1;
+	}
+	if (have < 4 + addrlen + 2)
+		return 0;
+	buffer_consume(&c->input, sizeof(s5_req));
+	buffer_get(&c->input, (char *)&dest_addr, addrlen);
+	buffer_get(&c->input, (char *)&dest_port, 2);
+	dest_addr[addrlen] = '\0';
+	if (s5_req.atyp == SSH_SOCKS5_DOMAIN)
+		strlcpy(c->path, dest_addr, sizeof(c->path));
+	else if (inet_ntop(af, dest_addr, c->path, sizeof(c->path)) == NULL)
+		return -1;
+	c->host_port = ntohs(dest_port);
+	
+	debug("channel %d: dynamic request: socks5 host %s port %u command %u",
+	    c->self, c->path, c->host_port, s5_req.command);
+
+	s5_rsp.version = 0x05;
+	s5_rsp.command = SSH_SOCKS5_SUCCESS;
+	s5_rsp.reserved = 0;			/* ignored */
+	s5_rsp.atyp = SSH_SOCKS5_IPV4;
+	((struct in_addr *)&dest_addr)->s_addr = INADDR_ANY;
+	dest_port = 0;				/* ignored */
+
+	buffer_append(&c->output, (char *)&s5_rsp, sizeof(s5_rsp));
+	buffer_append(&c->output, (char *)&dest_addr, sizeof(struct in_addr));
+	buffer_append(&c->output, (char *)&dest_port, sizeof(dest_port));
+	return 1;
+}
+
 /* dynamic port forwarding */
 static void
 channel_pre_dynamic(Channel *c, fd_set * readset, fd_set * writeset)
@@ -952,7 +1061,7 @@
 	debug2("channel %d: pre_dynamic: have %d", c->self, have);
 	/* buffer_dump(&c->input); */
 	/* check if the fixed size part of the packet is in buffer. */
-	if (have < 4) {
+	if (have < 3) {
 		/* need more */
 		FD_SET(c->sock, readset);
 		return;
@@ -962,6 +1071,9 @@
 	switch (p[0]) {
 	case 0x04:
 		ret = channel_decode_socks4(c, readset, writeset);
+		break;
+	case 0x05:
+		ret = channel_decode_socks5(c, readset, writeset);
 		break;
 	default:
 		ret = -1;