plink: updated to revision 10170 of putty

1 files changed, 1509 insertions, 1507 deletions

diff --git a/tools/plink/proxy.c b/tools/plink/proxy.c
index fcc81475b..e2201c643 100644
--- a/tools/plink/proxy.c
+++ b/tools/plink/proxy.c
@@ -1,1507 +1,1509 @@
-/*

- * Network proxy abstraction in PuTTY

- *

- * A proxy layer, if necessary, wedges itself between the network

- * code and the higher level backend.

- */

-

-#include <assert.h>

-#include <ctype.h>

-#include <string.h>

-

-#define DEFINE_PLUG_METHOD_MACROS

-#include "putty.h"

-#include "network.h"

-#include "proxy.h"

-

-#define do_proxy_dns(conf) \

-    (conf_get_int(conf, CONF_proxy_dns) == FORCE_ON || \

-	 (conf_get_int(conf, CONF_proxy_dns) == AUTO && \

-	      conf_get_int(conf, CONF_proxy_type) != PROXY_SOCKS4))

-

-/*

- * Call this when proxy negotiation is complete, so that this

- * socket can begin working normally.

- */

-void proxy_activate (Proxy_Socket p)

-{

-    void *data;

-    int len;

-    long output_before, output_after;

-    

-    p->state = PROXY_STATE_ACTIVE;

-

-    /* we want to ignore new receive events until we have sent

-     * all of our buffered receive data.

-     */

-    sk_set_frozen(p->sub_socket, 1);

-

-    /* how many bytes of output have we buffered? */

-    output_before = bufchain_size(&p->pending_oob_output_data) +

-	bufchain_size(&p->pending_output_data);

-    /* and keep track of how many bytes do not get sent. */

-    output_after = 0;

-    

-    /* send buffered OOB writes */

-    while (bufchain_size(&p->pending_oob_output_data) > 0) {

-	bufchain_prefix(&p->pending_oob_output_data, &data, &len);

-	output_after += sk_write_oob(p->sub_socket, data, len);

-	bufchain_consume(&p->pending_oob_output_data, len);

-    }

-

-    /* send buffered normal writes */

-    while (bufchain_size(&p->pending_output_data) > 0) {

-	bufchain_prefix(&p->pending_output_data, &data, &len);

-	output_after += sk_write(p->sub_socket, data, len);

-	bufchain_consume(&p->pending_output_data, len);

-    }

-

-    /* if we managed to send any data, let the higher levels know. */

-    if (output_after < output_before)

-	plug_sent(p->plug, output_after);

-

-    /* if we were asked to flush the output during

-     * the proxy negotiation process, do so now.

-     */

-    if (p->pending_flush) sk_flush(p->sub_socket);

-

-    /* if we have a pending EOF to send, send it */

-    if (p->pending_eof) sk_write_eof(p->sub_socket);

-

-    /* if the backend wanted the socket unfrozen, try to unfreeze.

-     * our set_frozen handler will flush buffered receive data before

-     * unfreezing the actual underlying socket.

-     */

-    if (!p->freeze)

-	sk_set_frozen((Socket)p, 0);

-}

-

-/* basic proxy socket functions */

-

-static Plug sk_proxy_plug (Socket s, Plug p)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-    Plug ret = ps->plug;

-    if (p)

-	ps->plug = p;

-    return ret;

-}

-

-static void sk_proxy_close (Socket s)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-

-    sk_close(ps->sub_socket);

-    sk_addr_free(ps->remote_addr);

-    sfree(ps);

-}

-

-static int sk_proxy_write (Socket s, const char *data, int len)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	bufchain_add(&ps->pending_output_data, data, len);

-	return bufchain_size(&ps->pending_output_data);

-    }

-    return sk_write(ps->sub_socket, data, len);

-}

-

-static int sk_proxy_write_oob (Socket s, const char *data, int len)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	bufchain_clear(&ps->pending_output_data);

-	bufchain_clear(&ps->pending_oob_output_data);

-	bufchain_add(&ps->pending_oob_output_data, data, len);

-	return len;

-    }

-    return sk_write_oob(ps->sub_socket, data, len);

-}

-

-static void sk_proxy_write_eof (Socket s)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-        ps->pending_eof = 1;

-	return;

-    }

-    sk_write_eof(ps->sub_socket);

-}

-

-static void sk_proxy_flush (Socket s)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	ps->pending_flush = 1;

-	return;

-    }

-    sk_flush(ps->sub_socket);

-}

-

-static void sk_proxy_set_private_ptr (Socket s, void *ptr)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-    sk_set_private_ptr(ps->sub_socket, ptr);

-}

-

-static void * sk_proxy_get_private_ptr (Socket s)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-    return sk_get_private_ptr(ps->sub_socket);

-}

-

-static void sk_proxy_set_frozen (Socket s, int is_frozen)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	ps->freeze = is_frozen;

-	return;

-    }

-    

-    /* handle any remaining buffered recv data first */

-    if (bufchain_size(&ps->pending_input_data) > 0) {

-	ps->freeze = is_frozen;

-

-	/* loop while we still have buffered data, and while we are

-	 * unfrozen. the plug_receive call in the loop could result 

-	 * in a call back into this function refreezing the socket, 

-	 * so we have to check each time.

-	 */

-        while (!ps->freeze && bufchain_size(&ps->pending_input_data) > 0) {

-	    void *data;

-	    char databuf[512];

-	    int len;

-	    bufchain_prefix(&ps->pending_input_data, &data, &len);

-	    if (len > lenof(databuf))

-		len = lenof(databuf);

-	    memcpy(databuf, data, len);

-	    bufchain_consume(&ps->pending_input_data, len);

-	    plug_receive(ps->plug, 0, databuf, len);

-	}

-

-	/* if we're still frozen, we'll have to wait for another

-	 * call from the backend to finish unbuffering the data.

-	 */

-	if (ps->freeze) return;

-    }

-    

-    sk_set_frozen(ps->sub_socket, is_frozen);

-}

-

-static const char * sk_proxy_socket_error (Socket s)

-{

-    Proxy_Socket ps = (Proxy_Socket) s;

-    if (ps->error != NULL || ps->sub_socket == NULL) {

-	return ps->error;

-    }

-    return sk_socket_error(ps->sub_socket);

-}

-

-/* basic proxy plug functions */

-

-static void plug_proxy_log(Plug plug, int type, SockAddr addr, int port,

-			   const char *error_msg, int error_code)

-{

-    Proxy_Plug pp = (Proxy_Plug) plug;

-    Proxy_Socket ps = pp->proxy_socket;

-

-    plug_log(ps->plug, type, addr, port, error_msg, error_code);

-}

-

-static int plug_proxy_closing (Plug p, const char *error_msg,

-			       int error_code, int calling_back)

-{

-    Proxy_Plug pp = (Proxy_Plug) p;

-    Proxy_Socket ps = pp->proxy_socket;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	ps->closing_error_msg = error_msg;

-	ps->closing_error_code = error_code;

-	ps->closing_calling_back = calling_back;

-	return ps->negotiate(ps, PROXY_CHANGE_CLOSING);

-    }

-    return plug_closing(ps->plug, error_msg,

-			error_code, calling_back);

-}

-

-static int plug_proxy_receive (Plug p, int urgent, char *data, int len)

-{

-    Proxy_Plug pp = (Proxy_Plug) p;

-    Proxy_Socket ps = pp->proxy_socket;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	/* we will lose the urgentness of this data, but since most,

-	 * if not all, of this data will be consumed by the negotiation

-	 * process, hopefully it won't affect the protocol above us

-	 */

-	bufchain_add(&ps->pending_input_data, data, len);

-	ps->receive_urgent = urgent;

-	ps->receive_data = data;

-	ps->receive_len = len;

-	return ps->negotiate(ps, PROXY_CHANGE_RECEIVE);

-    }

-    return plug_receive(ps->plug, urgent, data, len);

-}

-

-static void plug_proxy_sent (Plug p, int bufsize)

-{

-    Proxy_Plug pp = (Proxy_Plug) p;

-    Proxy_Socket ps = pp->proxy_socket;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	ps->sent_bufsize = bufsize;

-	ps->negotiate(ps, PROXY_CHANGE_SENT);

-	return;

-    }

-    plug_sent(ps->plug, bufsize);

-}

-

-static int plug_proxy_accepting (Plug p, OSSocket sock)

-{

-    Proxy_Plug pp = (Proxy_Plug) p;

-    Proxy_Socket ps = pp->proxy_socket;

-

-    if (ps->state != PROXY_STATE_ACTIVE) {

-	ps->accepting_sock = sock;

-	return ps->negotiate(ps, PROXY_CHANGE_ACCEPTING);

-    }

-    return plug_accepting(ps->plug, sock);

-}

-

-/*

- * This function can accept a NULL pointer as `addr', in which case

- * it will only check the host name.

- */

-static int proxy_for_destination (SockAddr addr, char *hostname, int port,

-				  Conf *conf)

-{

-    int s = 0, e = 0;

-    char hostip[64];

-    int hostip_len, hostname_len;

-    const char *exclude_list;

-

-    /*

-     * Check the host name and IP against the hard-coded

-     * representations of `localhost'.

-     */

-    if (!conf_get_int(conf, CONF_even_proxy_localhost) &&

-	(sk_hostname_is_local(hostname) ||

-	 (addr && sk_address_is_local(addr))))

-	return 0;		       /* do not proxy */

-

-    /* we want a string representation of the IP address for comparisons */

-    if (addr) {

-	sk_getaddr(addr, hostip, 64);

-	hostip_len = strlen(hostip);

-    } else

-	hostip_len = 0;		       /* placate gcc; shouldn't be required */

-

-    hostname_len = strlen(hostname);

-

-    exclude_list = conf_get_str(conf, CONF_proxy_exclude_list);

-

-    /* now parse the exclude list, and see if either our IP

-     * or hostname matches anything in it.

-     */

-

-    while (exclude_list[s]) {

-	while (exclude_list[s] &&

-	       (isspace((unsigned char)exclude_list[s]) ||

-		exclude_list[s] == ',')) s++;

-

-	if (!exclude_list[s]) break;

-

-	e = s;

-

-	while (exclude_list[e] &&

-	       (isalnum((unsigned char)exclude_list[e]) ||

-		exclude_list[e] == '-' ||

-		exclude_list[e] == '.' ||

-		exclude_list[e] == '*')) e++;

-

-	if (exclude_list[s] == '*') {

-	    /* wildcard at beginning of entry */

-

-	    if ((addr && strnicmp(hostip + hostip_len - (e - s - 1),

-				  exclude_list + s + 1, e - s - 1) == 0) ||

-		strnicmp(hostname + hostname_len - (e - s - 1),

-			 exclude_list + s + 1, e - s - 1) == 0)

-		return 0; /* IP/hostname range excluded. do not use proxy. */

-

-	} else if (exclude_list[e-1] == '*') {

-	    /* wildcard at end of entry */

-

-	    if ((addr && strnicmp(hostip, exclude_list + s, e - s - 1) == 0) ||

-		strnicmp(hostname, exclude_list + s, e - s - 1) == 0)

-		return 0; /* IP/hostname range excluded. do not use proxy. */

-

-	} else {

-	    /* no wildcard at either end, so let's try an absolute

-	     * match (ie. a specific IP)

-	     */

-

-	    if (addr && strnicmp(hostip, exclude_list + s, e - s) == 0)

-		return 0; /* IP/hostname excluded. do not use proxy. */

-	    if (strnicmp(hostname, exclude_list + s, e - s) == 0)

-		return 0; /* IP/hostname excluded. do not use proxy. */

-	}

-

-	s = e;

-

-	/* Make sure we really have reached the next comma or end-of-string */

-	while (exclude_list[s] &&

-	       !isspace((unsigned char)exclude_list[s]) &&

-	       exclude_list[s] != ',') s++;

-    }

-

-    /* no matches in the exclude list, so use the proxy */

-    return 1;

-}

-

-SockAddr name_lookup(char *host, int port, char **canonicalname,

-		     Conf *conf, int addressfamily)

-{

-    if (conf_get_int(conf, CONF_proxy_type) != PROXY_NONE &&

-	do_proxy_dns(conf) &&

-	proxy_for_destination(NULL, host, port, conf)) {

-	*canonicalname = dupstr(host);

-	return sk_nonamelookup(host);

-    }

-

-    return sk_namelookup(host, canonicalname, addressfamily);

-}

-

-Socket new_connection(SockAddr addr, char *hostname,

-		      int port, int privport,

-		      int oobinline, int nodelay, int keepalive,

-		      Plug plug, Conf *conf)

-{

-    static const struct socket_function_table socket_fn_table = {

-	sk_proxy_plug,

-	sk_proxy_close,

-	sk_proxy_write,

-	sk_proxy_write_oob,

-	sk_proxy_write_eof,

-	sk_proxy_flush,

-	sk_proxy_set_private_ptr,

-	sk_proxy_get_private_ptr,

-	sk_proxy_set_frozen,

-	sk_proxy_socket_error

-    };

-

-    static const struct plug_function_table plug_fn_table = {

-	plug_proxy_log,

-	plug_proxy_closing,

-	plug_proxy_receive,

-	plug_proxy_sent,

-	plug_proxy_accepting

-    };

-

-    if (conf_get_int(conf, CONF_proxy_type) != PROXY_NONE &&

-	proxy_for_destination(addr, hostname, port, conf))

-    {

-	Proxy_Socket ret;

-	Proxy_Plug pplug;

-	SockAddr proxy_addr;

-	char *proxy_canonical_name;

-	Socket sret;

-	int type;

-

-	if ((sret = platform_new_connection(addr, hostname, port, privport,

-					    oobinline, nodelay, keepalive,

-					    plug, conf)) !=

-	    NULL)

-	    return sret;

-

-	ret = snew(struct Socket_proxy_tag);

-	ret->fn = &socket_fn_table;

-	ret->conf = conf_copy(conf);

-	ret->plug = plug;

-	ret->remote_addr = addr;       /* will need to be freed on close */

-	ret->remote_port = port;

-

-	ret->error = NULL;

-	ret->pending_flush = 0;

-	ret->pending_eof = 0;

-	ret->freeze = 0;

-

-	bufchain_init(&ret->pending_input_data);

-	bufchain_init(&ret->pending_output_data);

-	bufchain_init(&ret->pending_oob_output_data);

-

-	ret->sub_socket = NULL;

-	ret->state = PROXY_STATE_NEW;

-	ret->negotiate = NULL;

-

-	type = conf_get_int(conf, CONF_proxy_type);

-	if (type == PROXY_HTTP) {

-	    ret->negotiate = proxy_http_negotiate;

-	} else if (type == PROXY_SOCKS4) {

-            ret->negotiate = proxy_socks4_negotiate;

-	} else if (type == PROXY_SOCKS5) {

-            ret->negotiate = proxy_socks5_negotiate;

-	} else if (type == PROXY_TELNET) {

-	    ret->negotiate = proxy_telnet_negotiate;

-	} else {

-	    ret->error = "Proxy error: Unknown proxy method";

-	    return (Socket) ret;

-	}

-

-	/* create the proxy plug to map calls from the actual

-	 * socket into our proxy socket layer */

-	pplug = snew(struct Plug_proxy_tag);

-	pplug->fn = &plug_fn_table;

-	pplug->proxy_socket = ret;

-

-	/* look-up proxy */

-	proxy_addr = sk_namelookup(conf_get_str(conf, CONF_proxy_host),

-				   &proxy_canonical_name,

-				   conf_get_int(conf, CONF_addressfamily));

-	if (sk_addr_error(proxy_addr) != NULL) {

-	    ret->error = "Proxy error: Unable to resolve proxy host name";

-	    return (Socket)ret;

-	}

-	sfree(proxy_canonical_name);

-

-	/* create the actual socket we will be using,

-	 * connected to our proxy server and port.

-	 */

-	ret->sub_socket = sk_new(proxy_addr,

-				 conf_get_int(conf, CONF_proxy_port),

-				 privport, oobinline,

-				 nodelay, keepalive, (Plug) pplug);

-	if (sk_socket_error(ret->sub_socket) != NULL)

-	    return (Socket) ret;

-

-	/* start the proxy negotiation process... */

-	sk_set_frozen(ret->sub_socket, 0);

-	ret->negotiate(ret, PROXY_CHANGE_NEW);

-

-	return (Socket) ret;

-    }

-

-    /* no proxy, so just return the direct socket */

-    return sk_new(addr, port, privport, oobinline, nodelay, keepalive, plug);

-}

-

-Socket new_listener(char *srcaddr, int port, Plug plug, int local_host_only,

-		    Conf *conf, int addressfamily)

-{

-    /* TODO: SOCKS (and potentially others) support inbound

-     * TODO: connections via the proxy. support them.

-     */

-

-    return sk_newlistener(srcaddr, port, plug, local_host_only, addressfamily);

-}

-

-/* ----------------------------------------------------------------------

- * HTTP CONNECT proxy type.

- */

-

-static int get_line_end (char * data, int len)

-{

-    int off = 0;

-

-    while (off < len)

-    {

-	if (data[off] == '\n') {

-	    /* we have a newline */

-	    off++;

-

-	    /* is that the only thing on this line? */

-	    if (off <= 2) return off;

-

-	    /* if not, then there is the possibility that this header

-	     * continues onto the next line, if it starts with a space

-	     * or a tab.

-	     */

-

-	    if (off + 1 < len &&

-		data[off+1] != ' ' &&

-		data[off+1] != '\t') return off;

-

-	    /* the line does continue, so we have to keep going

-	     * until we see an the header's "real" end of line.

-	     */

-	    off++;

-	}

-

-	off++;

-    }

-

-    return -1;

-}

-

-int proxy_http_negotiate (Proxy_Socket p, int change)

-{

-    if (p->state == PROXY_STATE_NEW) {

-	/* we are just beginning the proxy negotiate process,

-	 * so we'll send off the initial bits of the request.

-	 * for this proxy method, it's just a simple HTTP

-	 * request

-	 */

-	char *buf, dest[512];

-	char *username, *password;

-

-	sk_getaddr(p->remote_addr, dest, lenof(dest));

-

-	buf = dupprintf("CONNECT %s:%i HTTP/1.1\r\nHost: %s:%i\r\n",

-			dest, p->remote_port, dest, p->remote_port);

-	sk_write(p->sub_socket, buf, strlen(buf));

-	sfree(buf);

-

-	username = conf_get_str(p->conf, CONF_proxy_username);

-	password = conf_get_str(p->conf, CONF_proxy_password);

-	if (username[0] || password[0]) {

-	    char *buf, *buf2;

-	    int i, j, len;

-	    buf = dupprintf("%s:%s", username, password);

-	    len = strlen(buf);

-	    buf2 = snewn(len * 4 / 3 + 100, char);

-	    sprintf(buf2, "Proxy-Authorization: Basic ");

-	    for (i = 0, j = strlen(buf2); i < len; i += 3, j += 4)

-		base64_encode_atom((unsigned char *)(buf+i),

-				   (len-i > 3 ? 3 : len-i), buf2+j);

-	    strcpy(buf2+j, "\r\n");

-	    sk_write(p->sub_socket, buf2, strlen(buf2));

-	    sfree(buf);

-	    sfree(buf2);

-	}

-

-	sk_write(p->sub_socket, "\r\n", 2);

-

-	p->state = 1;

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_CLOSING) {

-	/* if our proxy negotiation process involves closing and opening

-	 * new sockets, then we would want to intercept this closing

-	 * callback when we were expecting it. if we aren't anticipating

-	 * a socket close, then some error must have occurred. we'll

-	 * just pass those errors up to the backend.

-	 */

-	return plug_closing(p->plug, p->closing_error_msg,

-			    p->closing_error_code,

-			    p->closing_calling_back);

-    }

-

-    if (change == PROXY_CHANGE_SENT) {

-	/* some (or all) of what we wrote to the proxy was sent.

-	 * we don't do anything new, however, until we receive the

-	 * proxy's response. we might want to set a timer so we can

-	 * timeout the proxy negotiation after a while...

-	 */

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_ACCEPTING) {

-	/* we should _never_ see this, as we are using our socket to

-	 * connect to a proxy, not accepting inbound connections.

-	 * what should we do? close the socket with an appropriate

-	 * error message?

-	 */

-	return plug_accepting(p->plug, p->accepting_sock);

-    }

-

-    if (change == PROXY_CHANGE_RECEIVE) {

-	/* we have received data from the underlying socket, which

-	 * we'll need to parse, process, and respond to appropriately.

-	 */

-

-	char *data, *datap;

-	int len;

-	int eol;

-

-	if (p->state == 1) {

-

-	    int min_ver, maj_ver, status;

-

-	    /* get the status line */

-	    len = bufchain_size(&p->pending_input_data);

-	    assert(len > 0);	       /* or we wouldn't be here */

-	    data = snewn(len+1, char);

-	    bufchain_fetch(&p->pending_input_data, data, len);

-	    /*

-	     * We must NUL-terminate this data, because Windows

-	     * sscanf appears to require a NUL at the end of the

-	     * string because it strlens it _first_. Sigh.

-	     */

-	    data[len] = '\0';

-

-	    eol = get_line_end(data, len);

-	    if (eol < 0) {

-		sfree(data);

-		return 1;

-	    }

-

-	    status = -1;

-	    /* We can't rely on whether the %n incremented the sscanf return */

-	    if (sscanf((char *)data, "HTTP/%i.%i %n",

-		       &maj_ver, &min_ver, &status) < 2 || status == -1) {

-		plug_closing(p->plug, "Proxy error: HTTP response was absent",

-			     PROXY_ERROR_GENERAL, 0);

-		sfree(data);

-		return 1;

-	    }

-

-	    /* remove the status line from the input buffer. */

-	    bufchain_consume(&p->pending_input_data, eol);

-	    if (data[status] != '2') {

-		/* error */

-		char *buf;

-		data[eol] = '\0';

-		while (eol > status &&

-		       (data[eol-1] == '\r' || data[eol-1] == '\n'))

-		    data[--eol] = '\0';

-		buf = dupprintf("Proxy error: %s", data+status);

-		plug_closing(p->plug, buf, PROXY_ERROR_GENERAL, 0);

-		sfree(buf);

-		sfree(data);

-		return 1;

-	    }

-

-	    sfree(data);

-

-	    p->state = 2;

-	}

-

-	if (p->state == 2) {

-

-	    /* get headers. we're done when we get a

-	     * header of length 2, (ie. just "\r\n")

-	     */

-

-	    len = bufchain_size(&p->pending_input_data);

-	    assert(len > 0);	       /* or we wouldn't be here */

-	    data = snewn(len, char);

-	    datap = data;

-	    bufchain_fetch(&p->pending_input_data, data, len);

-

-	    eol = get_line_end(datap, len);

-	    if (eol < 0) {

-		sfree(data);

-		return 1;

-	    }

-	    while (eol > 2)

-	    {

-		bufchain_consume(&p->pending_input_data, eol);

-		datap += eol;

-		len   -= eol;

-		eol = get_line_end(datap, len);

-	    }

-

-	    if (eol == 2) {

-		/* we're done */

-		bufchain_consume(&p->pending_input_data, 2);

-		proxy_activate(p);

-		/* proxy activate will have dealt with

-		 * whatever is left of the buffer */

-		sfree(data);

-		return 1;

-	    }

-

-	    sfree(data);

-	    return 1;

-	}

-    }

-

-    plug_closing(p->plug, "Proxy error: unexpected proxy error",

-		 PROXY_ERROR_UNEXPECTED, 0);

-    return 1;

-}

-

-/* ----------------------------------------------------------------------

- * SOCKS proxy type.

- */

-

-/* SOCKS version 4 */

-int proxy_socks4_negotiate (Proxy_Socket p, int change)

-{

-    if (p->state == PROXY_CHANGE_NEW) {

-

-	/* request format:

-	 *  version number (1 byte) = 4

-	 *  command code (1 byte)

-	 *    1 = CONNECT

-	 *    2 = BIND

-	 *  dest. port (2 bytes) [network order]

-	 *  dest. address (4 bytes)

-	 *  user ID (variable length, null terminated string)

-	 */

-

-	int length, type, namelen;

-	char *command, addr[4], hostname[512];

-	char *username;

-

-	type = sk_addrtype(p->remote_addr);

-	if (type == ADDRTYPE_IPV6) {

-	    plug_closing(p->plug, "Proxy error: SOCKS version 4 does"

-			 " not support IPv6", PROXY_ERROR_GENERAL, 0);

-	    return 1;

-	} else if (type == ADDRTYPE_IPV4) {

-	    namelen = 0;

-	    sk_addrcopy(p->remote_addr, addr);

-	} else {		       /* type == ADDRTYPE_NAME */

-	    assert(type == ADDRTYPE_NAME);

-	    sk_getaddr(p->remote_addr, hostname, lenof(hostname));

-	    namelen = strlen(hostname) + 1;   /* include the NUL */

-	    addr[0] = addr[1] = addr[2] = 0;

-	    addr[3] = 1;

-	}

-

-	username = conf_get_str(p->conf, CONF_proxy_username);

-	length = strlen(username) + namelen + 9;

-	command = snewn(length, char);

-	strcpy(command + 8, username);

-

-	command[0] = 4; /* version 4 */

-	command[1] = 1; /* CONNECT command */

-

-	/* port */

-	command[2] = (char) (p->remote_port >> 8) & 0xff;

-	command[3] = (char) p->remote_port & 0xff;

-

-	/* address */

-	memcpy(command + 4, addr, 4);

-

-	/* hostname */

-	memcpy(command + 8 + strlen(username) + 1,

-	       hostname, namelen);

-

-	sk_write(p->sub_socket, command, length);

-	sfree(username);

-	sfree(command);

-

-	p->state = 1;

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_CLOSING) {

-	/* if our proxy negotiation process involves closing and opening

-	 * new sockets, then we would want to intercept this closing

-	 * callback when we were expecting it. if we aren't anticipating

-	 * a socket close, then some error must have occurred. we'll

-	 * just pass those errors up to the backend.

-	 */

-	return plug_closing(p->plug, p->closing_error_msg,

-			    p->closing_error_code,

-			    p->closing_calling_back);

-    }

-

-    if (change == PROXY_CHANGE_SENT) {

-	/* some (or all) of what we wrote to the proxy was sent.

-	 * we don't do anything new, however, until we receive the

-	 * proxy's response. we might want to set a timer so we can

-	 * timeout the proxy negotiation after a while...

-	 */

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_ACCEPTING) {

-	/* we should _never_ see this, as we are using our socket to

-	 * connect to a proxy, not accepting inbound connections.

-	 * what should we do? close the socket with an appropriate

-	 * error message?

-	 */

-	return plug_accepting(p->plug, p->accepting_sock);

-    }

-

-    if (change == PROXY_CHANGE_RECEIVE) {

-	/* we have received data from the underlying socket, which

-	 * we'll need to parse, process, and respond to appropriately.

-	 */

-

-	if (p->state == 1) {

-	    /* response format:

-	     *  version number (1 byte) = 4

-	     *  reply code (1 byte)

-	     *    90 = request granted

-	     *    91 = request rejected or failed

-	     *    92 = request rejected due to lack of IDENTD on client

-	     *    93 = request rejected due to difference in user ID 

-	     *         (what we sent vs. what IDENTD said)

-	     *  dest. port (2 bytes)

-	     *  dest. address (4 bytes)

-	     */

-

-	    char data[8];

-

-	    if (bufchain_size(&p->pending_input_data) < 8)

-		return 1;	       /* not got anything yet */

-	    

-	    /* get the response */

-	    bufchain_fetch(&p->pending_input_data, data, 8);

-

-	    if (data[0] != 0) {

-		plug_closing(p->plug, "Proxy error: SOCKS proxy responded with "

-				      "unexpected reply code version",

-			     PROXY_ERROR_GENERAL, 0);

-		return 1;

-	    }

-

-	    if (data[1] != 90) {

-

-		switch (data[1]) {

-		  case 92:

-		    plug_closing(p->plug, "Proxy error: SOCKS server wanted IDENTD on client",

-				 PROXY_ERROR_GENERAL, 0);

-		    break;

-		  case 93:

-		    plug_closing(p->plug, "Proxy error: Username and IDENTD on client don't agree",

-				 PROXY_ERROR_GENERAL, 0);

-		    break;

-		  case 91:

-		  default:

-		    plug_closing(p->plug, "Proxy error: Error while communicating with proxy",

-				 PROXY_ERROR_GENERAL, 0);

-		    break;

-		}

-

-		return 1;

-	    }

-	    bufchain_consume(&p->pending_input_data, 8);

-

-	    /* we're done */

-	    proxy_activate(p);

-	    /* proxy activate will have dealt with

-	     * whatever is left of the buffer */

-	    return 1;

-	}

-    }

-

-    plug_closing(p->plug, "Proxy error: unexpected proxy error",

-		 PROXY_ERROR_UNEXPECTED, 0);

-    return 1;

-}

-

-/* SOCKS version 5 */

-int proxy_socks5_negotiate (Proxy_Socket p, int change)

-{

-    if (p->state == PROXY_CHANGE_NEW) {

-

-	/* initial command:

-	 *  version number (1 byte) = 5

-	 *  number of available authentication methods (1 byte)

-	 *  available authentication methods (1 byte * previous value)

-	 *    authentication methods:

-	 *     0x00 = no authentication

-	 *     0x01 = GSSAPI

-	 *     0x02 = username/password

-	 *     0x03 = CHAP

-	 */

-

-	char command[5];

-	char *username, *password;

-	int len;

-

-	command[0] = 5; /* version 5 */

-	username = conf_get_str(p->conf, CONF_proxy_username);

-	password = conf_get_str(p->conf, CONF_proxy_password);

-	if (username[0] || password[0]) {

-	    command[2] = 0x00;	       /* no authentication */

-	    len = 3;

-	    proxy_socks5_offerencryptedauth (command, &len);

-	    command[len++] = 0x02;	       /* username/password */

-	    command[1] = len - 2;	/* Number of methods supported */

-	} else {

-	    command[1] = 1;	       /* one methods supported: */

-	    command[2] = 0x00;	       /* no authentication */

-	    len = 3;

-	}

-

-	sk_write(p->sub_socket, command, len);

-

-	p->state = 1;

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_CLOSING) {

-	/* if our proxy negotiation process involves closing and opening

-	 * new sockets, then we would want to intercept this closing

-	 * callback when we were expecting it. if we aren't anticipating

-	 * a socket close, then some error must have occurred. we'll

-	 * just pass those errors up to the backend.

-	 */

-	return plug_closing(p->plug, p->closing_error_msg,

-			    p->closing_error_code,

-			    p->closing_calling_back);

-    }

-

-    if (change == PROXY_CHANGE_SENT) {

-	/* some (or all) of what we wrote to the proxy was sent.

-	 * we don't do anything new, however, until we receive the

-	 * proxy's response. we might want to set a timer so we can

-	 * timeout the proxy negotiation after a while...

-	 */

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_ACCEPTING) {

-	/* we should _never_ see this, as we are using our socket to

-	 * connect to a proxy, not accepting inbound connections.

-	 * what should we do? close the socket with an appropriate

-	 * error message?

-	 */

-	return plug_accepting(p->plug, p->accepting_sock);

-    }

-

-    if (change == PROXY_CHANGE_RECEIVE) {

-	/* we have received data from the underlying socket, which

-	 * we'll need to parse, process, and respond to appropriately.

-	 */

-

-	if (p->state == 1) {

-

-	    /* initial response:

-	     *  version number (1 byte) = 5

-	     *  authentication method (1 byte)

-	     *    authentication methods:

-	     *     0x00 = no authentication

-	     *     0x01 = GSSAPI

-	     *     0x02 = username/password

-	     *     0x03 = CHAP

-	     *     0xff = no acceptable methods

-	     */

-	    char data[2];

-

-	    if (bufchain_size(&p->pending_input_data) < 2)

-		return 1;	       /* not got anything yet */

-

-	    /* get the response */

-	    bufchain_fetch(&p->pending_input_data, data, 2);

-

-	    if (data[0] != 5) {

-		plug_closing(p->plug, "Proxy error: SOCKS proxy returned unexpected version",

-			     PROXY_ERROR_GENERAL, 0);

-		return 1;

-	    }

-

-	    if (data[1] == 0x00) p->state = 2; /* no authentication needed */

-	    else if (data[1] == 0x01) p->state = 4; /* GSSAPI authentication */

-	    else if (data[1] == 0x02) p->state = 5; /* username/password authentication */

-	    else if (data[1] == 0x03) p->state = 6; /* CHAP authentication */

-	    else {

-		plug_closing(p->plug, "Proxy error: SOCKS proxy did not accept our authentication",

-			     PROXY_ERROR_GENERAL, 0);

-		return 1;

-	    }

-	    bufchain_consume(&p->pending_input_data, 2);

-	}

-

-	if (p->state == 7) {

-

-	    /* password authentication reply format:

-	     *  version number (1 bytes) = 1

-	     *  reply code (1 byte)

-	     *    0 = succeeded

-	     *    >0 = failed

-	     */

-	    char data[2];

-

-	    if (bufchain_size(&p->pending_input_data) < 2)

-		return 1;	       /* not got anything yet */

-

-	    /* get the response */

-	    bufchain_fetch(&p->pending_input_data, data, 2);

-

-	    if (data[0] != 1) {

-		plug_closing(p->plug, "Proxy error: SOCKS password "

-			     "subnegotiation contained wrong version number",

-			     PROXY_ERROR_GENERAL, 0);

-		return 1;

-	    }

-

-	    if (data[1] != 0) {

-

-		plug_closing(p->plug, "Proxy error: SOCKS proxy refused"

-			     " password authentication",

-			     PROXY_ERROR_GENERAL, 0);

-		return 1;

-	    }

-

-	    bufchain_consume(&p->pending_input_data, 2);

-	    p->state = 2;	       /* now proceed as authenticated */

-	}

-

-	if (p->state == 8) {

-	    int ret;

-	    ret = proxy_socks5_handlechap(p);

-	    if (ret) return ret;

-	}

-

-	if (p->state == 2) {

-

-	    /* request format:

-	     *  version number (1 byte) = 5

-	     *  command code (1 byte)

-	     *    1 = CONNECT

-	     *    2 = BIND

-	     *    3 = UDP ASSOCIATE

-	     *  reserved (1 byte) = 0x00

-	     *  address type (1 byte)

-	     *    1 = IPv4

-	     *    3 = domainname (first byte has length, no terminating null)

-	     *    4 = IPv6

-	     *  dest. address (variable)

-	     *  dest. port (2 bytes) [network order]

-	     */

-

-	    char command[512];

-	    int len;

-	    int type;

-

-	    type = sk_addrtype(p->remote_addr);

-	    if (type == ADDRTYPE_IPV4) {

-		len = 10;	       /* 4 hdr + 4 addr + 2 trailer */

-		command[3] = 1; /* IPv4 */

-		sk_addrcopy(p->remote_addr, command+4);

-	    } else if (type == ADDRTYPE_IPV6) {

-		len = 22;	       /* 4 hdr + 16 addr + 2 trailer */

-		command[3] = 4; /* IPv6 */

-		sk_addrcopy(p->remote_addr, command+4);

-	    } else {

-		assert(type == ADDRTYPE_NAME);

-		command[3] = 3;

-		sk_getaddr(p->remote_addr, command+5, 256);

-		command[4] = strlen(command+5);

-		len = 7 + command[4];  /* 4 hdr, 1 len, N addr, 2 trailer */

-	    }

-

-	    command[0] = 5; /* version 5 */

-	    command[1] = 1; /* CONNECT command */

-	    command[2] = 0x00;

-

-	    /* port */

-	    command[len-2] = (char) (p->remote_port >> 8) & 0xff;

-	    command[len-1] = (char) p->remote_port & 0xff;

-

-	    sk_write(p->sub_socket, command, len);

-

-	    p->state = 3;

-	    return 1;

-	}

-

-	if (p->state == 3) {

-

-	    /* reply format:

-	     *  version number (1 bytes) = 5

-	     *  reply code (1 byte)

-	     *    0 = succeeded

-	     *    1 = general SOCKS server failure

-	     *    2 = connection not allowed by ruleset

-	     *    3 = network unreachable

-	     *    4 = host unreachable

-	     *    5 = connection refused

-	     *    6 = TTL expired

-	     *    7 = command not supported

-	     *    8 = address type not supported

-	     * reserved (1 byte) = x00

-	     * address type (1 byte)

-	     *    1 = IPv4

-	     *    3 = domainname (first byte has length, no terminating null)

-	     *    4 = IPv6

-	     * server bound address (variable)

-	     * server bound port (2 bytes) [network order]

-	     */

-	    char data[5];

-	    int len;

-

-	    /* First 5 bytes of packet are enough to tell its length. */ 

-	    if (bufchain_size(&p->pending_input_data) < 5)

-		return 1;	       /* not got anything yet */

-

-	    /* get the response */

-	    bufchain_fetch(&p->pending_input_data, data, 5);

-

-	    if (data[0] != 5) {

-		plug_closing(p->plug, "Proxy error: SOCKS proxy returned wrong version number",

-			     PROXY_ERROR_GENERAL, 0);

-		return 1;

-	    }

-

-	    if (data[1] != 0) {

-		char buf[256];

-

-		strcpy(buf, "Proxy error: ");

-

-		switch (data[1]) {

-		  case 1: strcat(buf, "General SOCKS server failure"); break;

-		  case 2: strcat(buf, "Connection not allowed by ruleset"); break;

-		  case 3: strcat(buf, "Network unreachable"); break;

-		  case 4: strcat(buf, "Host unreachable"); break;

-		  case 5: strcat(buf, "Connection refused"); break;

-		  case 6: strcat(buf, "TTL expired"); break;

-		  case 7: strcat(buf, "Command not supported"); break;

-		  case 8: strcat(buf, "Address type not supported"); break;

-		  default: sprintf(buf+strlen(buf),

-				   "Unrecognised SOCKS error code %d",

-				   data[1]);

-		    break;

-		}

-		plug_closing(p->plug, buf, PROXY_ERROR_GENERAL, 0);

-

-		return 1;

-	    }

-

-	    /*

-	     * Eat the rest of the reply packet.

-	     */

-	    len = 6;		       /* first 4 bytes, last 2 */

-	    switch (data[3]) {

-	      case 1: len += 4; break; /* IPv4 address */

-	      case 4: len += 16; break;/* IPv6 address */

-	      case 3: len += (unsigned char)data[4]; break; /* domain name */

-	      default:

-		plug_closing(p->plug, "Proxy error: SOCKS proxy returned "

-			     "unrecognised address format",

-			     PROXY_ERROR_GENERAL, 0);

-		return 1;

-	    }

-	    if (bufchain_size(&p->pending_input_data) < len)

-		return 1;	       /* not got whole reply yet */

-	    bufchain_consume(&p->pending_input_data, len);

-

-	    /* we're done */

-	    proxy_activate(p);

-	    return 1;

-	}

-

-	if (p->state == 4) {

-	    /* TODO: Handle GSSAPI authentication */

-	    plug_closing(p->plug, "Proxy error: We don't support GSSAPI authentication",

-			 PROXY_ERROR_GENERAL, 0);

-	    return 1;

-	}

-

-	if (p->state == 5) {

-	    char *username = conf_get_str(p->conf, CONF_proxy_username);

-	    char *password = conf_get_str(p->conf, CONF_proxy_password);

-	    if (username[0] || password[0]) {

-		char userpwbuf[255 + 255 + 3];

-		int ulen, plen;

-		ulen = strlen(username);

-		if (ulen > 255) ulen = 255; if (ulen < 1) ulen = 1;

-		plen = strlen(password);

-		if (plen > 255) plen = 255; if (plen < 1) plen = 1;

-		userpwbuf[0] = 1;      /* version number of subnegotiation */

-		userpwbuf[1] = ulen;

-		memcpy(userpwbuf+2, username, ulen);

-		userpwbuf[ulen+2] = plen;

-		memcpy(userpwbuf+ulen+3, password, plen);

-		sk_write(p->sub_socket, userpwbuf, ulen + plen + 3);

-		p->state = 7;

-	    } else 

-		plug_closing(p->plug, "Proxy error: Server chose "

-			     "username/password authentication but we "

-			     "didn't offer it!",

-			 PROXY_ERROR_GENERAL, 0);

-	    return 1;

-	}

-

-	if (p->state == 6) {

-	    int ret;

-	    ret = proxy_socks5_selectchap(p);

-	    if (ret) return ret;

-	}

-

-    }

-

-    plug_closing(p->plug, "Proxy error: Unexpected proxy error",

-		 PROXY_ERROR_UNEXPECTED, 0);

-    return 1;

-}

-

-/* ----------------------------------------------------------------------

- * `Telnet' proxy type.

- *

- * (This is for ad-hoc proxies where you connect to the proxy's

- * telnet port and send a command such as `connect host port'. The

- * command is configurable, since this proxy type is typically not

- * standardised or at all well-defined.)

- */

-

-char *format_telnet_command(SockAddr addr, int port, Conf *conf)

-{

-    char *fmt = conf_get_str(conf, CONF_proxy_telnet_command);

-    char *ret = NULL;

-    int retlen = 0, retsize = 0;

-    int so = 0, eo = 0;

-#define ENSURE(n) do { \

-    if (retsize < retlen + n) { \

-	retsize = retlen + n + 512; \

-	ret = sresize(ret, retsize, char); \

-    } \

-} while (0)

-

-    /* we need to escape \\, \%, \r, \n, \t, \x??, \0???, 

-     * %%, %host, %port, %user, and %pass

-     */

-

-    while (fmt[eo] != 0) {

-

-	/* scan forward until we hit end-of-line,

-	 * or an escape character (\ or %) */

-	while (fmt[eo] != 0 && fmt[eo] != '%' && fmt[eo] != '\\')

-	    eo++;

-

-	/* if we hit eol, break out of our escaping loop */

-	if (fmt[eo] == 0) break;

-

-	/* if there was any unescaped text before the escape

-	 * character, send that now */

-	if (eo != so) {

-	    ENSURE(eo - so);

-	    memcpy(ret + retlen, fmt + so, eo - so);

-	    retlen += eo - so;

-	}

-

-	so = eo++;

-

-	/* if the escape character was the last character of

-	 * the line, we'll just stop and send it. */

-	if (fmt[eo] == 0) break;

-

-	if (fmt[so] == '\\') {

-

-	    /* we recognize \\, \%, \r, \n, \t, \x??.

-	     * anything else, we just send unescaped (including the \).

-	     */

-

-	    switch (fmt[eo]) {

-

-	      case '\\':

-		ENSURE(1);

-		ret[retlen++] = '\\';

-		eo++;

-		break;

-

-	      case '%':

-		ENSURE(1);

-		ret[retlen++] = '%';

-		eo++;

-		break;

-

-	      case 'r':

-		ENSURE(1);

-		ret[retlen++] = '\r';

-		eo++;

-		break;

-

-	      case 'n':

-		ENSURE(1);

-		ret[retlen++] = '\n';

-		eo++;

-		break;

-

-	      case 't':

-		ENSURE(1);

-		ret[retlen++] = '\t';

-		eo++;

-		break;

-

-	      case 'x':

-	      case 'X':

-		{

-		    /* escaped hexadecimal value (ie. \xff) */

-		    unsigned char v = 0;

-		    int i = 0;

-

-		    for (;;) {

-			eo++;

-			if (fmt[eo] >= '0' && fmt[eo] <= '9')

-			    v += fmt[eo] - '0';

-			else if (fmt[eo] >= 'a' && fmt[eo] <= 'f')

-			    v += fmt[eo] - 'a' + 10;

-			else if (fmt[eo] >= 'A' && fmt[eo] <= 'F')

-			    v += fmt[eo] - 'A' + 10;

-			else {

-			    /* non hex character, so we abort and just

-			     * send the whole thing unescaped (including \x)

-			     */

-			    ENSURE(1);

-			    ret[retlen++] = '\\';

-			    eo = so + 1;

-			    break;

-			}

-

-			/* we only extract two hex characters */

-			if (i == 1) {

-			    ENSURE(1);

-			    ret[retlen++] = v;

-			    eo++;

-			    break;

-			}

-

-			i++;

-			v <<= 4;

-		    }

-		}

-		break;

-

-	      default:

-		ENSURE(2);

-		memcpy(ret+retlen, fmt + so, 2);

-		retlen += 2;

-		eo++;

-		break;

-	    }

-	} else {

-

-	    /* % escape. we recognize %%, %host, %port, %user, %pass.

-	     * %proxyhost, %proxyport. Anything else we just send

-	     * unescaped (including the %).

-	     */

-

-	    if (fmt[eo] == '%') {

-		ENSURE(1);

-		ret[retlen++] = '%';

-		eo++;

-	    }

-	    else if (strnicmp(fmt + eo, "host", 4) == 0) {

-		char dest[512];

-		int destlen;

-		sk_getaddr(addr, dest, lenof(dest));

-		destlen = strlen(dest);

-		ENSURE(destlen);

-		memcpy(ret+retlen, dest, destlen);

-		retlen += destlen;

-		eo += 4;

-	    }

-	    else if (strnicmp(fmt + eo, "port", 4) == 0) {

-		char portstr[8], portlen;

-		portlen = sprintf(portstr, "%i", port);

-		ENSURE(portlen);

-		memcpy(ret + retlen, portstr, portlen);

-		retlen += portlen;

-		eo += 4;

-	    }

-	    else if (strnicmp(fmt + eo, "user", 4) == 0) {

-		char *username = conf_get_str(conf, CONF_proxy_username);

-		int userlen = strlen(username);

-		ENSURE(userlen);

-		memcpy(ret+retlen, username, userlen);

-		retlen += userlen;

-		eo += 4;

-	    }

-	    else if (strnicmp(fmt + eo, "pass", 4) == 0) {

-		char *password = conf_get_str(conf, CONF_proxy_password);

-		int passlen = strlen(password);

-		ENSURE(passlen);

-		memcpy(ret+retlen, password, passlen);

-		retlen += passlen;

-		eo += 4;

-	    }

-	    else if (strnicmp(fmt + eo, "proxyhost", 9) == 0) {

-		char *host = conf_get_str(conf, CONF_proxy_host);

-		int phlen = strlen(host);

-		ENSURE(phlen);

-		memcpy(ret+retlen, host, phlen);

-		retlen += phlen;

-		eo += 9;

-	    }

-	    else if (strnicmp(fmt + eo, "proxyport", 9) == 0) {

-		int port = conf_get_int(conf, CONF_proxy_port);

-                char pport[50];

-		int pplen;

-                sprintf(pport, "%d", port);

-                pplen = strlen(pport);

-		ENSURE(pplen);

-		memcpy(ret+retlen, pport, pplen);

-		retlen += pplen;

-		eo += 9;

-	    }

-	    else {

-		/* we don't escape this, so send the % now, and

-		 * don't advance eo, so that we'll consider the

-		 * text immediately following the % as unescaped.

-		 */

-		ENSURE(1);

-		ret[retlen++] = '%';

-	    }

-	}

-

-	/* resume scanning for additional escapes after this one. */

-	so = eo;

-    }

-

-    /* if there is any unescaped text at the end of the line, send it */

-    if (eo != so) {

-	ENSURE(eo - so);

-	memcpy(ret + retlen, fmt + so, eo - so);

-	retlen += eo - so;

-    }

-

-    ENSURE(1);

-    ret[retlen] = '\0';

-    return ret;

-

-#undef ENSURE

-}

-

-int proxy_telnet_negotiate (Proxy_Socket p, int change)

-{

-    if (p->state == PROXY_CHANGE_NEW) {

-	char *formatted_cmd;

-

-	formatted_cmd = format_telnet_command(p->remote_addr, p->remote_port,

-					      p->conf);

-

-	sk_write(p->sub_socket, formatted_cmd, strlen(formatted_cmd));

-	sfree(formatted_cmd);

-

-	p->state = 1;

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_CLOSING) {

-	/* if our proxy negotiation process involves closing and opening

-	 * new sockets, then we would want to intercept this closing

-	 * callback when we were expecting it. if we aren't anticipating

-	 * a socket close, then some error must have occurred. we'll

-	 * just pass those errors up to the backend.

-	 */

-	return plug_closing(p->plug, p->closing_error_msg,

-			    p->closing_error_code,

-			    p->closing_calling_back);

-    }

-

-    if (change == PROXY_CHANGE_SENT) {

-	/* some (or all) of what we wrote to the proxy was sent.

-	 * we don't do anything new, however, until we receive the

-	 * proxy's response. we might want to set a timer so we can

-	 * timeout the proxy negotiation after a while...

-	 */

-	return 0;

-    }

-

-    if (change == PROXY_CHANGE_ACCEPTING) {

-	/* we should _never_ see this, as we are using our socket to

-	 * connect to a proxy, not accepting inbound connections.

-	 * what should we do? close the socket with an appropriate

-	 * error message?

-	 */

-	return plug_accepting(p->plug, p->accepting_sock);

-    }

-

-    if (change == PROXY_CHANGE_RECEIVE) {

-	/* we have received data from the underlying socket, which

-	 * we'll need to parse, process, and respond to appropriately.

-	 */

-

-	/* we're done */

-	proxy_activate(p);

-	/* proxy activate will have dealt with

-	 * whatever is left of the buffer */

-	return 1;

-    }

-

-    plug_closing(p->plug, "Proxy error: Unexpected proxy error",

-		 PROXY_ERROR_UNEXPECTED, 0);

-    return 1;

-}

+/*
+ * Network proxy abstraction in PuTTY
+ *
+ * A proxy layer, if necessary, wedges itself between the network
+ * code and the higher level backend.
+ */
+
+#include <assert.h>
+#include <ctype.h>
+#include <string.h>
+
+#define DEFINE_PLUG_METHOD_MACROS
+#include "putty.h"
+#include "network.h"
+#include "proxy.h"
+
+#define do_proxy_dns(conf) \
+    (conf_get_int(conf, CONF_proxy_dns) == FORCE_ON || \
+	 (conf_get_int(conf, CONF_proxy_dns) == AUTO && \
+	      conf_get_int(conf, CONF_proxy_type) != PROXY_SOCKS4))
+
+/*
+ * Call this when proxy negotiation is complete, so that this
+ * socket can begin working normally.
+ */
+void proxy_activate (Proxy_Socket p)
+{
+    void *data;
+    int len;
+    long output_before, output_after;
+    
+    p->state = PROXY_STATE_ACTIVE;
+
+    /* we want to ignore new receive events until we have sent
+     * all of our buffered receive data.
+     */
+    sk_set_frozen(p->sub_socket, 1);
+
+    /* how many bytes of output have we buffered? */
+    output_before = bufchain_size(&p->pending_oob_output_data) +
+	bufchain_size(&p->pending_output_data);
+    /* and keep track of how many bytes do not get sent. */
+    output_after = 0;
+    
+    /* send buffered OOB writes */
+    while (bufchain_size(&p->pending_oob_output_data) > 0) {
+	bufchain_prefix(&p->pending_oob_output_data, &data, &len);
+	output_after += sk_write_oob(p->sub_socket, data, len);
+	bufchain_consume(&p->pending_oob_output_data, len);
+    }
+
+    /* send buffered normal writes */
+    while (bufchain_size(&p->pending_output_data) > 0) {
+	bufchain_prefix(&p->pending_output_data, &data, &len);
+	output_after += sk_write(p->sub_socket, data, len);
+	bufchain_consume(&p->pending_output_data, len);
+    }
+
+    /* if we managed to send any data, let the higher levels know. */
+    if (output_after < output_before)
+	plug_sent(p->plug, output_after);
+
+    /* if we were asked to flush the output during
+     * the proxy negotiation process, do so now.
+     */
+    if (p->pending_flush) sk_flush(p->sub_socket);
+
+    /* if we have a pending EOF to send, send it */
+    if (p->pending_eof) sk_write_eof(p->sub_socket);
+
+    /* if the backend wanted the socket unfrozen, try to unfreeze.
+     * our set_frozen handler will flush buffered receive data before
+     * unfreezing the actual underlying socket.
+     */
+    if (!p->freeze)
+	sk_set_frozen((Socket)p, 0);
+}
+
+/* basic proxy socket functions */
+
+static Plug sk_proxy_plug (Socket s, Plug p)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+    Plug ret = ps->plug;
+    if (p)
+	ps->plug = p;
+    return ret;
+}
+
+static void sk_proxy_close (Socket s)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+
+    sk_close(ps->sub_socket);
+    sk_addr_free(ps->remote_addr);
+    sfree(ps);
+}
+
+static int sk_proxy_write (Socket s, const char *data, int len)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	bufchain_add(&ps->pending_output_data, data, len);
+	return bufchain_size(&ps->pending_output_data);
+    }
+    return sk_write(ps->sub_socket, data, len);
+}
+
+static int sk_proxy_write_oob (Socket s, const char *data, int len)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	bufchain_clear(&ps->pending_output_data);
+	bufchain_clear(&ps->pending_oob_output_data);
+	bufchain_add(&ps->pending_oob_output_data, data, len);
+	return len;
+    }
+    return sk_write_oob(ps->sub_socket, data, len);
+}
+
+static void sk_proxy_write_eof (Socket s)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+        ps->pending_eof = 1;
+	return;
+    }
+    sk_write_eof(ps->sub_socket);
+}
+
+static void sk_proxy_flush (Socket s)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	ps->pending_flush = 1;
+	return;
+    }
+    sk_flush(ps->sub_socket);
+}
+
+static void sk_proxy_set_frozen (Socket s, int is_frozen)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	ps->freeze = is_frozen;
+	return;
+    }
+    
+    /* handle any remaining buffered recv data first */
+    if (bufchain_size(&ps->pending_input_data) > 0) {
+	ps->freeze = is_frozen;
+
+	/* loop while we still have buffered data, and while we are
+	 * unfrozen. the plug_receive call in the loop could result 
+	 * in a call back into this function refreezing the socket, 
+	 * so we have to check each time.
+	 */
+        while (!ps->freeze && bufchain_size(&ps->pending_input_data) > 0) {
+	    void *data;
+	    char databuf[512];
+	    int len;
+	    bufchain_prefix(&ps->pending_input_data, &data, &len);
+	    if (len > lenof(databuf))
+		len = lenof(databuf);
+	    memcpy(databuf, data, len);
+	    bufchain_consume(&ps->pending_input_data, len);
+	    plug_receive(ps->plug, 0, databuf, len);
+	}
+
+	/* if we're still frozen, we'll have to wait for another
+	 * call from the backend to finish unbuffering the data.
+	 */
+	if (ps->freeze) return;
+    }
+    
+    sk_set_frozen(ps->sub_socket, is_frozen);
+}
+
+static const char * sk_proxy_socket_error (Socket s)
+{
+    Proxy_Socket ps = (Proxy_Socket) s;
+    if (ps->error != NULL || ps->sub_socket == NULL) {
+	return ps->error;
+    }
+    return sk_socket_error(ps->sub_socket);
+}
+
+/* basic proxy plug functions */
+
+static void plug_proxy_log(Plug plug, int type, SockAddr addr, int port,
+			   const char *error_msg, int error_code)
+{
+    Proxy_Plug pp = (Proxy_Plug) plug;
+    Proxy_Socket ps = pp->proxy_socket;
+
+    plug_log(ps->plug, type, addr, port, error_msg, error_code);
+}
+
+static int plug_proxy_closing (Plug p, const char *error_msg,
+			       int error_code, int calling_back)
+{
+    Proxy_Plug pp = (Proxy_Plug) p;
+    Proxy_Socket ps = pp->proxy_socket;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	ps->closing_error_msg = error_msg;
+	ps->closing_error_code = error_code;
+	ps->closing_calling_back = calling_back;
+	return ps->negotiate(ps, PROXY_CHANGE_CLOSING);
+    }
+    return plug_closing(ps->plug, error_msg,
+			error_code, calling_back);
+}
+
+static int plug_proxy_receive (Plug p, int urgent, char *data, int len)
+{
+    Proxy_Plug pp = (Proxy_Plug) p;
+    Proxy_Socket ps = pp->proxy_socket;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	/* we will lose the urgentness of this data, but since most,
+	 * if not all, of this data will be consumed by the negotiation
+	 * process, hopefully it won't affect the protocol above us
+	 */
+	bufchain_add(&ps->pending_input_data, data, len);
+	ps->receive_urgent = urgent;
+	ps->receive_data = data;
+	ps->receive_len = len;
+	return ps->negotiate(ps, PROXY_CHANGE_RECEIVE);
+    }
+    return plug_receive(ps->plug, urgent, data, len);
+}
+
+static void plug_proxy_sent (Plug p, int bufsize)
+{
+    Proxy_Plug pp = (Proxy_Plug) p;
+    Proxy_Socket ps = pp->proxy_socket;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	ps->sent_bufsize = bufsize;
+	ps->negotiate(ps, PROXY_CHANGE_SENT);
+	return;
+    }
+    plug_sent(ps->plug, bufsize);
+}
+
+static int plug_proxy_accepting(Plug p,
+                                accept_fn_t constructor, accept_ctx_t ctx)
+{
+    Proxy_Plug pp = (Proxy_Plug) p;
+    Proxy_Socket ps = pp->proxy_socket;
+
+    if (ps->state != PROXY_STATE_ACTIVE) {
+	ps->accepting_constructor = constructor;
+	ps->accepting_ctx = ctx;
+	return ps->negotiate(ps, PROXY_CHANGE_ACCEPTING);
+    }
+    return plug_accepting(ps->plug, constructor, ctx);
+}
+
+/*
+ * This function can accept a NULL pointer as `addr', in which case
+ * it will only check the host name.
+ */
+int proxy_for_destination (SockAddr addr, const char *hostname,
+                           int port, Conf *conf)
+{
+    int s = 0, e = 0;
+    char hostip[64];
+    int hostip_len, hostname_len;
+    const char *exclude_list;
+
+    /*
+     * Special local connections such as Unix-domain sockets
+     * unconditionally cannot be proxied, even in proxy-localhost
+     * mode. There just isn't any way to ask any known proxy type for
+     * them.
+     */
+    if (addr && sk_address_is_special_local(addr))
+        return 0;                      /* do not proxy */
+
+    /*
+     * Check the host name and IP against the hard-coded
+     * representations of `localhost'.
+     */
+    if (!conf_get_int(conf, CONF_even_proxy_localhost) &&
+	(sk_hostname_is_local(hostname) ||
+	 (addr && sk_address_is_local(addr))))
+	return 0;		       /* do not proxy */
+
+    /* we want a string representation of the IP address for comparisons */
+    if (addr) {
+	sk_getaddr(addr, hostip, 64);
+	hostip_len = strlen(hostip);
+    } else
+	hostip_len = 0;		       /* placate gcc; shouldn't be required */
+
+    hostname_len = strlen(hostname);
+
+    exclude_list = conf_get_str(conf, CONF_proxy_exclude_list);
+
+    /* now parse the exclude list, and see if either our IP
+     * or hostname matches anything in it.
+     */
+
+    while (exclude_list[s]) {
+	while (exclude_list[s] &&
+	       (isspace((unsigned char)exclude_list[s]) ||
+		exclude_list[s] == ',')) s++;
+
+	if (!exclude_list[s]) break;
+
+	e = s;
+
+	while (exclude_list[e] &&
+	       (isalnum((unsigned char)exclude_list[e]) ||
+		exclude_list[e] == '-' ||
+		exclude_list[e] == '.' ||
+		exclude_list[e] == '*')) e++;
+
+	if (exclude_list[s] == '*') {
+	    /* wildcard at beginning of entry */
+
+	    if ((addr && strnicmp(hostip + hostip_len - (e - s - 1),
+				  exclude_list + s + 1, e - s - 1) == 0) ||
+		strnicmp(hostname + hostname_len - (e - s - 1),
+			 exclude_list + s + 1, e - s - 1) == 0)
+		return 0; /* IP/hostname range excluded. do not use proxy. */
+
+	} else if (exclude_list[e-1] == '*') {
+	    /* wildcard at end of entry */
+
+	    if ((addr && strnicmp(hostip, exclude_list + s, e - s - 1) == 0) ||
+		strnicmp(hostname, exclude_list + s, e - s - 1) == 0)
+		return 0; /* IP/hostname range excluded. do not use proxy. */
+
+	} else {
+	    /* no wildcard at either end, so let's try an absolute
+	     * match (ie. a specific IP)
+	     */
+
+	    if (addr && strnicmp(hostip, exclude_list + s, e - s) == 0)
+		return 0; /* IP/hostname excluded. do not use proxy. */
+	    if (strnicmp(hostname, exclude_list + s, e - s) == 0)
+		return 0; /* IP/hostname excluded. do not use proxy. */
+	}
+
+	s = e;
+
+	/* Make sure we really have reached the next comma or end-of-string */
+	while (exclude_list[s] &&
+	       !isspace((unsigned char)exclude_list[s]) &&
+	       exclude_list[s] != ',') s++;
+    }
+
+    /* no matches in the exclude list, so use the proxy */
+    return 1;
+}
+
+SockAddr name_lookup(char *host, int port, char **canonicalname,
+		     Conf *conf, int addressfamily)
+{
+    if (conf_get_int(conf, CONF_proxy_type) != PROXY_NONE &&
+	do_proxy_dns(conf) &&
+	proxy_for_destination(NULL, host, port, conf)) {
+	*canonicalname = dupstr(host);
+	return sk_nonamelookup(host);
+    }
+
+    return sk_namelookup(host, canonicalname, addressfamily);
+}
+
+Socket new_connection(SockAddr addr, char *hostname,
+		      int port, int privport,
+		      int oobinline, int nodelay, int keepalive,
+		      Plug plug, Conf *conf)
+{
+    static const struct socket_function_table socket_fn_table = {
+	sk_proxy_plug,
+	sk_proxy_close,
+	sk_proxy_write,
+	sk_proxy_write_oob,
+	sk_proxy_write_eof,
+	sk_proxy_flush,
+	sk_proxy_set_frozen,
+	sk_proxy_socket_error
+    };
+
+    static const struct plug_function_table plug_fn_table = {
+	plug_proxy_log,
+	plug_proxy_closing,
+	plug_proxy_receive,
+	plug_proxy_sent,
+	plug_proxy_accepting
+    };
+
+    if (conf_get_int(conf, CONF_proxy_type) != PROXY_NONE &&
+	proxy_for_destination(addr, hostname, port, conf))
+    {
+	Proxy_Socket ret;
+	Proxy_Plug pplug;
+	SockAddr proxy_addr;
+	char *proxy_canonical_name;
+	Socket sret;
+	int type;
+
+	if ((sret = platform_new_connection(addr, hostname, port, privport,
+					    oobinline, nodelay, keepalive,
+					    plug, conf)) !=
+	    NULL)
+	    return sret;
+
+	ret = snew(struct Socket_proxy_tag);
+	ret->fn = &socket_fn_table;
+	ret->conf = conf_copy(conf);
+	ret->plug = plug;
+	ret->remote_addr = addr;       /* will need to be freed on close */
+	ret->remote_port = port;
+
+	ret->error = NULL;
+	ret->pending_flush = 0;
+	ret->pending_eof = 0;
+	ret->freeze = 0;
+
+	bufchain_init(&ret->pending_input_data);
+	bufchain_init(&ret->pending_output_data);
+	bufchain_init(&ret->pending_oob_output_data);
+
+	ret->sub_socket = NULL;
+	ret->state = PROXY_STATE_NEW;
+	ret->negotiate = NULL;
+
+	type = conf_get_int(conf, CONF_proxy_type);
+	if (type == PROXY_HTTP) {
+	    ret->negotiate = proxy_http_negotiate;
+	} else if (type == PROXY_SOCKS4) {
+            ret->negotiate = proxy_socks4_negotiate;
+	} else if (type == PROXY_SOCKS5) {
+            ret->negotiate = proxy_socks5_negotiate;
+	} else if (type == PROXY_TELNET) {
+	    ret->negotiate = proxy_telnet_negotiate;
+	} else {
+	    ret->error = "Proxy error: Unknown proxy method";
+	    return (Socket) ret;
+	}
+
+	/* create the proxy plug to map calls from the actual
+	 * socket into our proxy socket layer */
+	pplug = snew(struct Plug_proxy_tag);
+	pplug->fn = &plug_fn_table;
+	pplug->proxy_socket = ret;
+
+	/* look-up proxy */
+	proxy_addr = sk_namelookup(conf_get_str(conf, CONF_proxy_host),
+				   &proxy_canonical_name,
+				   conf_get_int(conf, CONF_addressfamily));
+	if (sk_addr_error(proxy_addr) != NULL) {
+	    ret->error = "Proxy error: Unable to resolve proxy host name";
+            sfree(pplug);
+            sk_addr_free(proxy_addr);
+	    return (Socket)ret;
+	}
+	sfree(proxy_canonical_name);
+
+	/* create the actual socket we will be using,
+	 * connected to our proxy server and port.
+	 */
+	ret->sub_socket = sk_new(proxy_addr,
+				 conf_get_int(conf, CONF_proxy_port),
+				 privport, oobinline,
+				 nodelay, keepalive, (Plug) pplug);
+	if (sk_socket_error(ret->sub_socket) != NULL)
+	    return (Socket) ret;
+
+	/* start the proxy negotiation process... */
+	sk_set_frozen(ret->sub_socket, 0);
+	ret->negotiate(ret, PROXY_CHANGE_NEW);
+
+	return (Socket) ret;
+    }
+
+    /* no proxy, so just return the direct socket */
+    return sk_new(addr, port, privport, oobinline, nodelay, keepalive, plug);
+}
+
+Socket new_listener(char *srcaddr, int port, Plug plug, int local_host_only,
+		    Conf *conf, int addressfamily)
+{
+    /* TODO: SOCKS (and potentially others) support inbound
+     * TODO: connections via the proxy. support them.
+     */
+
+    return sk_newlistener(srcaddr, port, plug, local_host_only, addressfamily);
+}
+
+/* ----------------------------------------------------------------------
+ * HTTP CONNECT proxy type.
+ */
+
+static int get_line_end (char * data, int len)
+{
+    int off = 0;
+
+    while (off < len)
+    {
+	if (data[off] == '\n') {
+	    /* we have a newline */
+	    off++;
+
+	    /* is that the only thing on this line? */
+	    if (off <= 2) return off;
+
+	    /* if not, then there is the possibility that this header
+	     * continues onto the next line, if it starts with a space
+	     * or a tab.
+	     */
+
+	    if (off + 1 < len &&
+		data[off+1] != ' ' &&
+		data[off+1] != '\t') return off;
+
+	    /* the line does continue, so we have to keep going
+	     * until we see an the header's "real" end of line.
+	     */
+	    off++;
+	}
+
+	off++;
+    }
+
+    return -1;
+}
+
+int proxy_http_negotiate (Proxy_Socket p, int change)
+{
+    if (p->state == PROXY_STATE_NEW) {
+	/* we are just beginning the proxy negotiate process,
+	 * so we'll send off the initial bits of the request.
+	 * for this proxy method, it's just a simple HTTP
+	 * request
+	 */
+	char *buf, dest[512];
+	char *username, *password;
+
+	sk_getaddr(p->remote_addr, dest, lenof(dest));
+
+	buf = dupprintf("CONNECT %s:%i HTTP/1.1\r\nHost: %s:%i\r\n",
+			dest, p->remote_port, dest, p->remote_port);
+	sk_write(p->sub_socket, buf, strlen(buf));
+	sfree(buf);
+
+	username = conf_get_str(p->conf, CONF_proxy_username);
+	password = conf_get_str(p->conf, CONF_proxy_password);
+	if (username[0] || password[0]) {
+	    char *buf, *buf2;
+	    int i, j, len;
+	    buf = dupprintf("%s:%s", username, password);
+	    len = strlen(buf);
+	    buf2 = snewn(len * 4 / 3 + 100, char);
+	    sprintf(buf2, "Proxy-Authorization: Basic ");
+	    for (i = 0, j = strlen(buf2); i < len; i += 3, j += 4)
+		base64_encode_atom((unsigned char *)(buf+i),
+				   (len-i > 3 ? 3 : len-i), buf2+j);
+	    strcpy(buf2+j, "\r\n");
+	    sk_write(p->sub_socket, buf2, strlen(buf2));
+	    sfree(buf);
+	    sfree(buf2);
+	}
+
+	sk_write(p->sub_socket, "\r\n", 2);
+
+	p->state = 1;
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_CLOSING) {
+	/* if our proxy negotiation process involves closing and opening
+	 * new sockets, then we would want to intercept this closing
+	 * callback when we were expecting it. if we aren't anticipating
+	 * a socket close, then some error must have occurred. we'll
+	 * just pass those errors up to the backend.
+	 */
+	return plug_closing(p->plug, p->closing_error_msg,
+			    p->closing_error_code,
+			    p->closing_calling_back);
+    }
+
+    if (change == PROXY_CHANGE_SENT) {
+	/* some (or all) of what we wrote to the proxy was sent.
+	 * we don't do anything new, however, until we receive the
+	 * proxy's response. we might want to set a timer so we can
+	 * timeout the proxy negotiation after a while...
+	 */
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_ACCEPTING) {
+	/* we should _never_ see this, as we are using our socket to
+	 * connect to a proxy, not accepting inbound connections.
+	 * what should we do? close the socket with an appropriate
+	 * error message?
+	 */
+	return plug_accepting(p->plug,
+                              p->accepting_constructor, p->accepting_ctx);
+    }
+
+    if (change == PROXY_CHANGE_RECEIVE) {
+	/* we have received data from the underlying socket, which
+	 * we'll need to parse, process, and respond to appropriately.
+	 */
+
+	char *data, *datap;
+	int len;
+	int eol;
+
+	if (p->state == 1) {
+
+	    int min_ver, maj_ver, status;
+
+	    /* get the status line */
+	    len = bufchain_size(&p->pending_input_data);
+	    assert(len > 0);	       /* or we wouldn't be here */
+	    data = snewn(len+1, char);
+	    bufchain_fetch(&p->pending_input_data, data, len);
+	    /*
+	     * We must NUL-terminate this data, because Windows
+	     * sscanf appears to require a NUL at the end of the
+	     * string because it strlens it _first_. Sigh.
+	     */
+	    data[len] = '\0';
+
+	    eol = get_line_end(data, len);
+	    if (eol < 0) {
+		sfree(data);
+		return 1;
+	    }
+
+	    status = -1;
+	    /* We can't rely on whether the %n incremented the sscanf return */
+	    if (sscanf((char *)data, "HTTP/%i.%i %n",
+		       &maj_ver, &min_ver, &status) < 2 || status == -1) {
+		plug_closing(p->plug, "Proxy error: HTTP response was absent",
+			     PROXY_ERROR_GENERAL, 0);
+		sfree(data);
+		return 1;
+	    }
+
+	    /* remove the status line from the input buffer. */
+	    bufchain_consume(&p->pending_input_data, eol);
+	    if (data[status] != '2') {
+		/* error */
+		char *buf;
+		data[eol] = '\0';
+		while (eol > status &&
+		       (data[eol-1] == '\r' || data[eol-1] == '\n'))
+		    data[--eol] = '\0';
+		buf = dupprintf("Proxy error: %s", data+status);
+		plug_closing(p->plug, buf, PROXY_ERROR_GENERAL, 0);
+		sfree(buf);
+		sfree(data);
+		return 1;
+	    }
+
+	    sfree(data);
+
+	    p->state = 2;
+	}
+
+	if (p->state == 2) {
+
+	    /* get headers. we're done when we get a
+	     * header of length 2, (ie. just "\r\n")
+	     */
+
+	    len = bufchain_size(&p->pending_input_data);
+	    assert(len > 0);	       /* or we wouldn't be here */
+	    data = snewn(len, char);
+	    datap = data;
+	    bufchain_fetch(&p->pending_input_data, data, len);
+
+	    eol = get_line_end(datap, len);
+	    if (eol < 0) {
+		sfree(data);
+		return 1;
+	    }
+	    while (eol > 2)
+	    {
+		bufchain_consume(&p->pending_input_data, eol);
+		datap += eol;
+		len   -= eol;
+		eol = get_line_end(datap, len);
+	    }
+
+	    if (eol == 2) {
+		/* we're done */
+		bufchain_consume(&p->pending_input_data, 2);
+		proxy_activate(p);
+		/* proxy activate will have dealt with
+		 * whatever is left of the buffer */
+		sfree(data);
+		return 1;
+	    }
+
+	    sfree(data);
+	    return 1;
+	}
+    }
+
+    plug_closing(p->plug, "Proxy error: unexpected proxy error",
+		 PROXY_ERROR_UNEXPECTED, 0);
+    return 1;
+}
+
+/* ----------------------------------------------------------------------
+ * SOCKS proxy type.
+ */
+
+/* SOCKS version 4 */
+int proxy_socks4_negotiate (Proxy_Socket p, int change)
+{
+    if (p->state == PROXY_CHANGE_NEW) {
+
+	/* request format:
+	 *  version number (1 byte) = 4
+	 *  command code (1 byte)
+	 *    1 = CONNECT
+	 *    2 = BIND
+	 *  dest. port (2 bytes) [network order]
+	 *  dest. address (4 bytes)
+	 *  user ID (variable length, null terminated string)
+	 */
+
+	int length, type, namelen;
+	char *command, addr[4], hostname[512];
+	char *username;
+
+	type = sk_addrtype(p->remote_addr);
+	if (type == ADDRTYPE_IPV6) {
+            p->error = "Proxy error: SOCKS version 4 does not support IPv6";
+	    return 1;
+	} else if (type == ADDRTYPE_IPV4) {
+	    namelen = 0;
+	    sk_addrcopy(p->remote_addr, addr);
+	} else {		       /* type == ADDRTYPE_NAME */
+	    assert(type == ADDRTYPE_NAME);
+	    sk_getaddr(p->remote_addr, hostname, lenof(hostname));
+	    namelen = strlen(hostname) + 1;   /* include the NUL */
+	    addr[0] = addr[1] = addr[2] = 0;
+	    addr[3] = 1;
+	}
+
+	username = conf_get_str(p->conf, CONF_proxy_username);
+	length = strlen(username) + namelen + 9;
+	command = snewn(length, char);
+	strcpy(command + 8, username);
+
+	command[0] = 4; /* version 4 */
+	command[1] = 1; /* CONNECT command */
+
+	/* port */
+	command[2] = (char) (p->remote_port >> 8) & 0xff;
+	command[3] = (char) p->remote_port & 0xff;
+
+	/* address */
+	memcpy(command + 4, addr, 4);
+
+	/* hostname */
+	memcpy(command + 8 + strlen(username) + 1,
+	       hostname, namelen);
+
+	sk_write(p->sub_socket, command, length);
+	sfree(username);
+	sfree(command);
+
+	p->state = 1;
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_CLOSING) {
+	/* if our proxy negotiation process involves closing and opening
+	 * new sockets, then we would want to intercept this closing
+	 * callback when we were expecting it. if we aren't anticipating
+	 * a socket close, then some error must have occurred. we'll
+	 * just pass those errors up to the backend.
+	 */
+	return plug_closing(p->plug, p->closing_error_msg,
+			    p->closing_error_code,
+			    p->closing_calling_back);
+    }
+
+    if (change == PROXY_CHANGE_SENT) {
+	/* some (or all) of what we wrote to the proxy was sent.
+	 * we don't do anything new, however, until we receive the
+	 * proxy's response. we might want to set a timer so we can
+	 * timeout the proxy negotiation after a while...
+	 */
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_ACCEPTING) {
+	/* we should _never_ see this, as we are using our socket to
+	 * connect to a proxy, not accepting inbound connections.
+	 * what should we do? close the socket with an appropriate
+	 * error message?
+	 */
+	return plug_accepting(p->plug,
+                              p->accepting_constructor, p->accepting_ctx);
+    }
+
+    if (change == PROXY_CHANGE_RECEIVE) {
+	/* we have received data from the underlying socket, which
+	 * we'll need to parse, process, and respond to appropriately.
+	 */
+
+	if (p->state == 1) {
+	    /* response format:
+	     *  version number (1 byte) = 4
+	     *  reply code (1 byte)
+	     *    90 = request granted
+	     *    91 = request rejected or failed
+	     *    92 = request rejected due to lack of IDENTD on client
+	     *    93 = request rejected due to difference in user ID 
+	     *         (what we sent vs. what IDENTD said)
+	     *  dest. port (2 bytes)
+	     *  dest. address (4 bytes)
+	     */
+
+	    char data[8];
+
+	    if (bufchain_size(&p->pending_input_data) < 8)
+		return 1;	       /* not got anything yet */
+	    
+	    /* get the response */
+	    bufchain_fetch(&p->pending_input_data, data, 8);
+
+	    if (data[0] != 0) {
+		plug_closing(p->plug, "Proxy error: SOCKS proxy responded with "
+				      "unexpected reply code version",
+			     PROXY_ERROR_GENERAL, 0);
+		return 1;
+	    }
+
+	    if (data[1] != 90) {
+
+		switch (data[1]) {
+		  case 92:
+		    plug_closing(p->plug, "Proxy error: SOCKS server wanted IDENTD on client",
+				 PROXY_ERROR_GENERAL, 0);
+		    break;
+		  case 93:
+		    plug_closing(p->plug, "Proxy error: Username and IDENTD on client don't agree",
+				 PROXY_ERROR_GENERAL, 0);
+		    break;
+		  case 91:
+		  default:
+		    plug_closing(p->plug, "Proxy error: Error while communicating with proxy",
+				 PROXY_ERROR_GENERAL, 0);
+		    break;
+		}
+
+		return 1;
+	    }
+	    bufchain_consume(&p->pending_input_data, 8);
+
+	    /* we're done */
+	    proxy_activate(p);
+	    /* proxy activate will have dealt with
+	     * whatever is left of the buffer */
+	    return 1;
+	}
+    }
+
+    plug_closing(p->plug, "Proxy error: unexpected proxy error",
+		 PROXY_ERROR_UNEXPECTED, 0);
+    return 1;
+}
+
+/* SOCKS version 5 */
+int proxy_socks5_negotiate (Proxy_Socket p, int change)
+{
+    if (p->state == PROXY_CHANGE_NEW) {
+
+	/* initial command:
+	 *  version number (1 byte) = 5
+	 *  number of available authentication methods (1 byte)
+	 *  available authentication methods (1 byte * previous value)
+	 *    authentication methods:
+	 *     0x00 = no authentication
+	 *     0x01 = GSSAPI
+	 *     0x02 = username/password
+	 *     0x03 = CHAP
+	 */
+
+	char command[5];
+	char *username, *password;
+	int len;
+
+	command[0] = 5; /* version 5 */
+	username = conf_get_str(p->conf, CONF_proxy_username);
+	password = conf_get_str(p->conf, CONF_proxy_password);
+	if (username[0] || password[0]) {
+	    command[2] = 0x00;	       /* no authentication */
+	    len = 3;
+	    proxy_socks5_offerencryptedauth (command, &len);
+	    command[len++] = 0x02;	       /* username/password */
+	    command[1] = len - 2;	/* Number of methods supported */
+	} else {
+	    command[1] = 1;	       /* one methods supported: */
+	    command[2] = 0x00;	       /* no authentication */
+	    len = 3;
+	}
+
+	sk_write(p->sub_socket, command, len);
+
+	p->state = 1;
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_CLOSING) {
+	/* if our proxy negotiation process involves closing and opening
+	 * new sockets, then we would want to intercept this closing
+	 * callback when we were expecting it. if we aren't anticipating
+	 * a socket close, then some error must have occurred. we'll
+	 * just pass those errors up to the backend.
+	 */
+	return plug_closing(p->plug, p->closing_error_msg,
+			    p->closing_error_code,
+			    p->closing_calling_back);
+    }
+
+    if (change == PROXY_CHANGE_SENT) {
+	/* some (or all) of what we wrote to the proxy was sent.
+	 * we don't do anything new, however, until we receive the
+	 * proxy's response. we might want to set a timer so we can
+	 * timeout the proxy negotiation after a while...
+	 */
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_ACCEPTING) {
+	/* we should _never_ see this, as we are using our socket to
+	 * connect to a proxy, not accepting inbound connections.
+	 * what should we do? close the socket with an appropriate
+	 * error message?
+	 */
+	return plug_accepting(p->plug,
+                              p->accepting_constructor, p->accepting_ctx);
+    }
+
+    if (change == PROXY_CHANGE_RECEIVE) {
+	/* we have received data from the underlying socket, which
+	 * we'll need to parse, process, and respond to appropriately.
+	 */
+
+	if (p->state == 1) {
+
+	    /* initial response:
+	     *  version number (1 byte) = 5
+	     *  authentication method (1 byte)
+	     *    authentication methods:
+	     *     0x00 = no authentication
+	     *     0x01 = GSSAPI
+	     *     0x02 = username/password
+	     *     0x03 = CHAP
+	     *     0xff = no acceptable methods
+	     */
+	    char data[2];
+
+	    if (bufchain_size(&p->pending_input_data) < 2)
+		return 1;	       /* not got anything yet */
+
+	    /* get the response */
+	    bufchain_fetch(&p->pending_input_data, data, 2);
+
+	    if (data[0] != 5) {
+		plug_closing(p->plug, "Proxy error: SOCKS proxy returned unexpected version",
+			     PROXY_ERROR_GENERAL, 0);
+		return 1;
+	    }
+
+	    if (data[1] == 0x00) p->state = 2; /* no authentication needed */
+	    else if (data[1] == 0x01) p->state = 4; /* GSSAPI authentication */
+	    else if (data[1] == 0x02) p->state = 5; /* username/password authentication */
+	    else if (data[1] == 0x03) p->state = 6; /* CHAP authentication */
+	    else {
+		plug_closing(p->plug, "Proxy error: SOCKS proxy did not accept our authentication",
+			     PROXY_ERROR_GENERAL, 0);
+		return 1;
+	    }
+	    bufchain_consume(&p->pending_input_data, 2);
+	}
+
+	if (p->state == 7) {
+
+	    /* password authentication reply format:
+	     *  version number (1 bytes) = 1
+	     *  reply code (1 byte)
+	     *    0 = succeeded
+	     *    >0 = failed
+	     */
+	    char data[2];
+
+	    if (bufchain_size(&p->pending_input_data) < 2)
+		return 1;	       /* not got anything yet */
+
+	    /* get the response */
+	    bufchain_fetch(&p->pending_input_data, data, 2);
+
+	    if (data[0] != 1) {
+		plug_closing(p->plug, "Proxy error: SOCKS password "
+			     "subnegotiation contained wrong version number",
+			     PROXY_ERROR_GENERAL, 0);
+		return 1;
+	    }
+
+	    if (data[1] != 0) {
+
+		plug_closing(p->plug, "Proxy error: SOCKS proxy refused"
+			     " password authentication",
+			     PROXY_ERROR_GENERAL, 0);
+		return 1;
+	    }
+
+	    bufchain_consume(&p->pending_input_data, 2);
+	    p->state = 2;	       /* now proceed as authenticated */
+	}
+
+	if (p->state == 8) {
+	    int ret;
+	    ret = proxy_socks5_handlechap(p);
+	    if (ret) return ret;
+	}
+
+	if (p->state == 2) {
+
+	    /* request format:
+	     *  version number (1 byte) = 5
+	     *  command code (1 byte)
+	     *    1 = CONNECT
+	     *    2 = BIND
+	     *    3 = UDP ASSOCIATE
+	     *  reserved (1 byte) = 0x00
+	     *  address type (1 byte)
+	     *    1 = IPv4
+	     *    3 = domainname (first byte has length, no terminating null)
+	     *    4 = IPv6
+	     *  dest. address (variable)
+	     *  dest. port (2 bytes) [network order]
+	     */
+
+	    char command[512];
+	    int len;
+	    int type;
+
+	    type = sk_addrtype(p->remote_addr);
+	    if (type == ADDRTYPE_IPV4) {
+		len = 10;	       /* 4 hdr + 4 addr + 2 trailer */
+		command[3] = 1; /* IPv4 */
+		sk_addrcopy(p->remote_addr, command+4);
+	    } else if (type == ADDRTYPE_IPV6) {
+		len = 22;	       /* 4 hdr + 16 addr + 2 trailer */
+		command[3] = 4; /* IPv6 */
+		sk_addrcopy(p->remote_addr, command+4);
+	    } else {
+		assert(type == ADDRTYPE_NAME);
+		command[3] = 3;
+		sk_getaddr(p->remote_addr, command+5, 256);
+		command[4] = strlen(command+5);
+		len = 7 + command[4];  /* 4 hdr, 1 len, N addr, 2 trailer */
+	    }
+
+	    command[0] = 5; /* version 5 */
+	    command[1] = 1; /* CONNECT command */
+	    command[2] = 0x00;
+
+	    /* port */
+	    command[len-2] = (char) (p->remote_port >> 8) & 0xff;
+	    command[len-1] = (char) p->remote_port & 0xff;
+
+	    sk_write(p->sub_socket, command, len);
+
+	    p->state = 3;
+	    return 1;
+	}
+
+	if (p->state == 3) {
+
+	    /* reply format:
+	     *  version number (1 bytes) = 5
+	     *  reply code (1 byte)
+	     *    0 = succeeded
+	     *    1 = general SOCKS server failure
+	     *    2 = connection not allowed by ruleset
+	     *    3 = network unreachable
+	     *    4 = host unreachable
+	     *    5 = connection refused
+	     *    6 = TTL expired
+	     *    7 = command not supported
+	     *    8 = address type not supported
+	     * reserved (1 byte) = x00
+	     * address type (1 byte)
+	     *    1 = IPv4
+	     *    3 = domainname (first byte has length, no terminating null)
+	     *    4 = IPv6
+	     * server bound address (variable)
+	     * server bound port (2 bytes) [network order]
+	     */
+	    char data[5];
+	    int len;
+
+	    /* First 5 bytes of packet are enough to tell its length. */ 
+	    if (bufchain_size(&p->pending_input_data) < 5)
+		return 1;	       /* not got anything yet */
+
+	    /* get the response */
+	    bufchain_fetch(&p->pending_input_data, data, 5);
+
+	    if (data[0] != 5) {
+		plug_closing(p->plug, "Proxy error: SOCKS proxy returned wrong version number",
+			     PROXY_ERROR_GENERAL, 0);
+		return 1;
+	    }
+
+	    if (data[1] != 0) {
+		char buf[256];
+
+		strcpy(buf, "Proxy error: ");
+
+		switch (data[1]) {
+		  case 1: strcat(buf, "General SOCKS server failure"); break;
+		  case 2: strcat(buf, "Connection not allowed by ruleset"); break;
+		  case 3: strcat(buf, "Network unreachable"); break;
+		  case 4: strcat(buf, "Host unreachable"); break;
+		  case 5: strcat(buf, "Connection refused"); break;
+		  case 6: strcat(buf, "TTL expired"); break;
+		  case 7: strcat(buf, "Command not supported"); break;
+		  case 8: strcat(buf, "Address type not supported"); break;
+		  default: sprintf(buf+strlen(buf),
+				   "Unrecognised SOCKS error code %d",
+				   data[1]);
+		    break;
+		}
+		plug_closing(p->plug, buf, PROXY_ERROR_GENERAL, 0);
+
+		return 1;
+	    }
+
+	    /*
+	     * Eat the rest of the reply packet.
+	     */
+	    len = 6;		       /* first 4 bytes, last 2 */
+	    switch (data[3]) {
+	      case 1: len += 4; break; /* IPv4 address */
+	      case 4: len += 16; break;/* IPv6 address */
+	      case 3: len += (unsigned char)data[4]; break; /* domain name */
+	      default:
+		plug_closing(p->plug, "Proxy error: SOCKS proxy returned "
+			     "unrecognised address format",
+			     PROXY_ERROR_GENERAL, 0);
+		return 1;
+	    }
+	    if (bufchain_size(&p->pending_input_data) < len)
+		return 1;	       /* not got whole reply yet */
+	    bufchain_consume(&p->pending_input_data, len);
+
+	    /* we're done */
+	    proxy_activate(p);
+	    return 1;
+	}
+
+	if (p->state == 4) {
+	    /* TODO: Handle GSSAPI authentication */
+	    plug_closing(p->plug, "Proxy error: We don't support GSSAPI authentication",
+			 PROXY_ERROR_GENERAL, 0);
+	    return 1;
+	}
+
+	if (p->state == 5) {
+	    char *username = conf_get_str(p->conf, CONF_proxy_username);
+	    char *password = conf_get_str(p->conf, CONF_proxy_password);
+	    if (username[0] || password[0]) {
+		char userpwbuf[255 + 255 + 3];
+		int ulen, plen;
+		ulen = strlen(username);
+		if (ulen > 255) ulen = 255; if (ulen < 1) ulen = 1;
+		plen = strlen(password);
+		if (plen > 255) plen = 255; if (plen < 1) plen = 1;
+		userpwbuf[0] = 1;      /* version number of subnegotiation */
+		userpwbuf[1] = ulen;
+		memcpy(userpwbuf+2, username, ulen);
+		userpwbuf[ulen+2] = plen;
+		memcpy(userpwbuf+ulen+3, password, plen);
+		sk_write(p->sub_socket, userpwbuf, ulen + plen + 3);
+		p->state = 7;
+	    } else 
+		plug_closing(p->plug, "Proxy error: Server chose "
+			     "username/password authentication but we "
+			     "didn't offer it!",
+			 PROXY_ERROR_GENERAL, 0);
+	    return 1;
+	}
+
+	if (p->state == 6) {
+	    int ret;
+	    ret = proxy_socks5_selectchap(p);
+	    if (ret) return ret;
+	}
+
+    }
+
+    plug_closing(p->plug, "Proxy error: Unexpected proxy error",
+		 PROXY_ERROR_UNEXPECTED, 0);
+    return 1;
+}
+
+/* ----------------------------------------------------------------------
+ * `Telnet' proxy type.
+ *
+ * (This is for ad-hoc proxies where you connect to the proxy's
+ * telnet port and send a command such as `connect host port'. The
+ * command is configurable, since this proxy type is typically not
+ * standardised or at all well-defined.)
+ */
+
+char *format_telnet_command(SockAddr addr, int port, Conf *conf)
+{
+    char *fmt = conf_get_str(conf, CONF_proxy_telnet_command);
+    char *ret = NULL;
+    int retlen = 0, retsize = 0;
+    int so = 0, eo = 0;
+#define ENSURE(n) do { \
+    if (retsize < retlen + n) { \
+	retsize = retlen + n + 512; \
+	ret = sresize(ret, retsize, char); \
+    } \
+} while (0)
+
+    /* we need to escape \\, \%, \r, \n, \t, \x??, \0???, 
+     * %%, %host, %port, %user, and %pass
+     */
+
+    while (fmt[eo] != 0) {
+
+	/* scan forward until we hit end-of-line,
+	 * or an escape character (\ or %) */
+	while (fmt[eo] != 0 && fmt[eo] != '%' && fmt[eo] != '\\')
+	    eo++;
+
+	/* if we hit eol, break out of our escaping loop */
+	if (fmt[eo] == 0) break;
+
+	/* if there was any unescaped text before the escape
+	 * character, send that now */
+	if (eo != so) {
+	    ENSURE(eo - so);
+	    memcpy(ret + retlen, fmt + so, eo - so);
+	    retlen += eo - so;
+	}
+
+	so = eo++;
+
+	/* if the escape character was the last character of
+	 * the line, we'll just stop and send it. */
+	if (fmt[eo] == 0) break;
+
+	if (fmt[so] == '\\') {
+
+	    /* we recognize \\, \%, \r, \n, \t, \x??.
+	     * anything else, we just send unescaped (including the \).
+	     */
+
+	    switch (fmt[eo]) {
+
+	      case '\\':
+		ENSURE(1);
+		ret[retlen++] = '\\';
+		eo++;
+		break;
+
+	      case '%':
+		ENSURE(1);
+		ret[retlen++] = '%';
+		eo++;
+		break;
+
+	      case 'r':
+		ENSURE(1);
+		ret[retlen++] = '\r';
+		eo++;
+		break;
+
+	      case 'n':
+		ENSURE(1);
+		ret[retlen++] = '\n';
+		eo++;
+		break;
+
+	      case 't':
+		ENSURE(1);
+		ret[retlen++] = '\t';
+		eo++;
+		break;
+
+	      case 'x':
+	      case 'X':
+		{
+		    /* escaped hexadecimal value (ie. \xff) */
+		    unsigned char v = 0;
+		    int i = 0;
+
+		    for (;;) {
+			eo++;
+			if (fmt[eo] >= '0' && fmt[eo] <= '9')
+			    v += fmt[eo] - '0';
+			else if (fmt[eo] >= 'a' && fmt[eo] <= 'f')
+			    v += fmt[eo] - 'a' + 10;
+			else if (fmt[eo] >= 'A' && fmt[eo] <= 'F')
+			    v += fmt[eo] - 'A' + 10;
+			else {
+			    /* non hex character, so we abort and just
+			     * send the whole thing unescaped (including \x)
+			     */
+			    ENSURE(1);
+			    ret[retlen++] = '\\';
+			    eo = so + 1;
+			    break;
+			}
+
+			/* we only extract two hex characters */
+			if (i == 1) {
+			    ENSURE(1);
+			    ret[retlen++] = v;
+			    eo++;
+			    break;
+			}
+
+			i++;
+			v <<= 4;
+		    }
+		}
+		break;
+
+	      default:
+		ENSURE(2);
+		memcpy(ret+retlen, fmt + so, 2);
+		retlen += 2;
+		eo++;
+		break;
+	    }
+	} else {
+
+	    /* % escape. we recognize %%, %host, %port, %user, %pass.
+	     * %proxyhost, %proxyport. Anything else we just send
+	     * unescaped (including the %).
+	     */
+
+	    if (fmt[eo] == '%') {
+		ENSURE(1);
+		ret[retlen++] = '%';
+		eo++;
+	    }
+	    else if (strnicmp(fmt + eo, "host", 4) == 0) {
+		char dest[512];
+		int destlen;
+		sk_getaddr(addr, dest, lenof(dest));
+		destlen = strlen(dest);
+		ENSURE(destlen);
+		memcpy(ret+retlen, dest, destlen);
+		retlen += destlen;
+		eo += 4;
+	    }
+	    else if (strnicmp(fmt + eo, "port", 4) == 0) {
+		char portstr[8], portlen;
+		portlen = sprintf(portstr, "%i", port);
+		ENSURE(portlen);
+		memcpy(ret + retlen, portstr, portlen);
+		retlen += portlen;
+		eo += 4;
+	    }
+	    else if (strnicmp(fmt + eo, "user", 4) == 0) {
+		char *username = conf_get_str(conf, CONF_proxy_username);
+		int userlen = strlen(username);
+		ENSURE(userlen);
+		memcpy(ret+retlen, username, userlen);
+		retlen += userlen;
+		eo += 4;
+	    }
+	    else if (strnicmp(fmt + eo, "pass", 4) == 0) {
+		char *password = conf_get_str(conf, CONF_proxy_password);
+		int passlen = strlen(password);
+		ENSURE(passlen);
+		memcpy(ret+retlen, password, passlen);
+		retlen += passlen;
+		eo += 4;
+	    }
+	    else if (strnicmp(fmt + eo, "proxyhost", 9) == 0) {
+		char *host = conf_get_str(conf, CONF_proxy_host);
+		int phlen = strlen(host);
+		ENSURE(phlen);
+		memcpy(ret+retlen, host, phlen);
+		retlen += phlen;
+		eo += 9;
+	    }
+	    else if (strnicmp(fmt + eo, "proxyport", 9) == 0) {
+		int port = conf_get_int(conf, CONF_proxy_port);
+                char pport[50];
+		int pplen;
+                sprintf(pport, "%d", port);
+                pplen = strlen(pport);
+		ENSURE(pplen);
+		memcpy(ret+retlen, pport, pplen);
+		retlen += pplen;
+		eo += 9;
+	    }
+	    else {
+		/* we don't escape this, so send the % now, and
+		 * don't advance eo, so that we'll consider the
+		 * text immediately following the % as unescaped.
+		 */
+		ENSURE(1);
+		ret[retlen++] = '%';
+	    }
+	}
+
+	/* resume scanning for additional escapes after this one. */
+	so = eo;
+    }
+
+    /* if there is any unescaped text at the end of the line, send it */
+    if (eo != so) {
+	ENSURE(eo - so);
+	memcpy(ret + retlen, fmt + so, eo - so);
+	retlen += eo - so;
+    }
+
+    ENSURE(1);
+    ret[retlen] = '\0';
+    return ret;
+
+#undef ENSURE
+}
+
+int proxy_telnet_negotiate (Proxy_Socket p, int change)
+{
+    if (p->state == PROXY_CHANGE_NEW) {
+	char *formatted_cmd;
+
+	formatted_cmd = format_telnet_command(p->remote_addr, p->remote_port,
+					      p->conf);
+
+	sk_write(p->sub_socket, formatted_cmd, strlen(formatted_cmd));
+	sfree(formatted_cmd);
+
+	p->state = 1;
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_CLOSING) {
+	/* if our proxy negotiation process involves closing and opening
+	 * new sockets, then we would want to intercept this closing
+	 * callback when we were expecting it. if we aren't anticipating
+	 * a socket close, then some error must have occurred. we'll
+	 * just pass those errors up to the backend.
+	 */
+	return plug_closing(p->plug, p->closing_error_msg,
+			    p->closing_error_code,
+			    p->closing_calling_back);
+    }
+
+    if (change == PROXY_CHANGE_SENT) {
+	/* some (or all) of what we wrote to the proxy was sent.
+	 * we don't do anything new, however, until we receive the
+	 * proxy's response. we might want to set a timer so we can
+	 * timeout the proxy negotiation after a while...
+	 */
+	return 0;
+    }
+
+    if (change == PROXY_CHANGE_ACCEPTING) {
+	/* we should _never_ see this, as we are using our socket to
+	 * connect to a proxy, not accepting inbound connections.
+	 * what should we do? close the socket with an appropriate
+	 * error message?
+	 */
+	return plug_accepting(p->plug,
+                              p->accepting_constructor, p->accepting_ctx);
+    }
+
+    if (change == PROXY_CHANGE_RECEIVE) {
+	/* we have received data from the underlying socket, which
+	 * we'll need to parse, process, and respond to appropriately.
+	 */
+
+	/* we're done */
+	proxy_activate(p);
+	/* proxy activate will have dealt with
+	 * whatever is left of the buffer */
+	return 1;
+    }
+
+    plug_closing(p->plug, "Proxy error: Unexpected proxy error",
+		 PROXY_ERROR_UNEXPECTED, 0);
+    return 1;
+}