putty/proxy.c

/*
 * Network proxy abstraction in PuTTY
 *
 * A proxy layer, if necessary, wedges itself between the network
 * code and the higher level backend.
 */

#include <windows.h>

#define DEFINE_PLUG_METHOD_MACROS
#include "putty.h"
#include "network.h"
#include "proxy.h"

/*
 * 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;

    p->state = PROXY_STATE_ACTIVE;

    /* let's try to keep extra receive events from coming through */
    sk_set_frozen(p->sub_socket, 1);

    /* send buffered OOB writes */
    while (bufchain_size(&p->pending_oob_output_data) > 0) {
	bufchain_prefix(&p->pending_oob_output_data, &data, &len);
	sk_write_oob(p->sub_socket, data, len);
	bufchain_consume(&p->pending_oob_output_data, len);
    }
    bufchain_clear(&p->pending_oob_output_data);

    /* send buffered normal writes */
    while (bufchain_size(&p->pending_output_data) > 0) {
	bufchain_prefix(&p->pending_output_data, &data, &len);
	sk_write(p->sub_socket, data, len);
	bufchain_consume(&p->pending_output_data, len);
    }
    bufchain_clear(&p->pending_output_data);

    /* 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);

    /* forward buffered recv data to the backend */
    while (bufchain_size(&p->pending_input_data) > 0) {
	bufchain_prefix(&p->pending_input_data, &data, &len);
	plug_receive(p->plug, 0, data, len);
	bufchain_consume(&p->pending_input_data, len);
    }
    bufchain_clear(&p->pending_input_data);

    /* now set the underlying socket to whatever freeze state they wanted */
    sk_set_frozen(p->sub_socket, p->freeze);
}

/* 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);
    sfree(ps);
}

static int sk_proxy_write (Socket s, 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, 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_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;
    }
    sk_set_frozen(ps->sub_socket, is_frozen);
}

static 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 int plug_proxy_closing (Plug p, 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, void *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);
}

static int proxy_for_destination (SockAddr addr, char * hostname, int port)
{
    int s = 0, e = 0;
    char hostip[64];
    int hostip_len, hostname_len;
    char * exclude_list;

    /* we want a string representation of the IP address for comparisons */
    sk_getaddr(addr, hostip, 64);

    hostip_len = strlen(hostip);
    hostname_len = strlen(hostname);

    exclude_list = cfg.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(exclude_list[s]) ||
		exclude_list[s] == ',')) s++;

	if (!exclude_list[s]) break;

	e = s;

	while (exclude_list[e] &&
	       (isalnum(exclude_list[e]) ||
		exclude_list[e] == '-' ||
		exclude_list[e] == '.' ||
		exclude_list[e] == '*')) e++;

	if (exclude_list[s] == '*') {
	    /* wildcard at beginning of entry */

	    if (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 (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 (stricmp(hostip, exclude_list + s) == 0)
		return 0; /* IP/hostname excluded. do not use proxy. */
	    if (stricmp(hostname, exclude_list + s) == 0)
		return 0; /* IP/hostname excluded. do not use proxy. */
	}

	s = e;
    }

    /* no matches in the exclude list, so use the proxy */
    return 1;
}

Socket new_connection(SockAddr addr, char *hostname,
		      int port, int privport,
		      int oobinline, int nodelay, Plug plug)
{
    static struct socket_function_table socket_fn_table = {
	sk_proxy_plug,
	sk_proxy_close,
	sk_proxy_write,
	sk_proxy_write_oob,
	sk_proxy_flush,
	sk_proxy_set_private_ptr,
	sk_proxy_get_private_ptr,
	sk_proxy_set_frozen,
	sk_proxy_socket_error
    };

    static struct plug_function_table plug_fn_table = {
	plug_proxy_closing,
	plug_proxy_receive,
	plug_proxy_sent,
	plug_proxy_accepting
    };

    if (cfg.proxy_type != PROXY_NONE &&
	proxy_for_destination(addr, hostname, port))
    {
	Proxy_Socket ret;
	Proxy_Plug pplug;
	SockAddr proxy_addr;
	char * proxy_canonical_name;

	ret = smalloc(sizeof(struct Socket_proxy_tag));
	ret->fn = &socket_fn_table;
	ret->plug = plug;
	ret->remote_addr = addr;
	ret->remote_port = port;

	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;

	if (cfg.proxy_type == PROXY_HTTP) {
	    ret->negotiate = proxy_http_negotiate;
	} else if (cfg.proxy_type == PROXY_SOCKS) {
	    ret->negotiate = proxy_socks_negotiate;
	} else if (cfg.proxy_type == PROXY_TELNET) {
	    ret->negotiate = proxy_telnet_negotiate;
	} else {
	    ret->error = "Network error: Unknown proxy method";
	    return (Socket) ret;
	}

	/* create the proxy plug to map calls from the actual
	 * socket into our proxy socket layer */
	pplug = smalloc(sizeof(struct Plug_proxy_tag));
	pplug->fn = &plug_fn_table;
	pplug->proxy_socket = ret;

	/* look-up proxy */
	proxy_addr = sk_namelookup(cfg.proxy_host,
				   &proxy_canonical_name);
	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, cfg.proxy_port,
				 privport, oobinline,
				 nodelay, (Plug) pplug);
	if (sk_socket_error(ret->sub_socket) != NULL)
	    return (Socket) ret;

	sk_addr_free(proxy_addr);

	/* 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, plug);
}

Socket new_listener(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);
}

/* ----------------------------------------------------------------------
 * 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[256], dest[64];

	sk_getaddr(p->remote_addr, dest, 64);

	sprintf(buf, "CONNECT %s:%i HTTP/1.1\r\nHost: %s:%i\r\n\r\n",
		dest, p->remote_port, dest, p->remote_port);
	sk_write(p->sub_socket, buf, strlen(buf));

	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.
	 */

	void *data;
	int len;
	int eol;

	if (p->state == 1) {

	    int min_ver, maj_ver, status;

	    /* get the status line */
	    bufchain_prefix(&p->pending_input_data, &data, &len);
	    eol = get_line_end(data, len);
	    if (eol < 0) return 1;

	    sscanf((char *)data, "HTTP/%i.%i %i", &maj_ver, &min_ver, &status);

	    /* remove the status line from the input buffer. */
	    bufchain_consume(&p->pending_input_data, eol);

	    /* TODO: we need to support Proxy-Auth headers */

	    if (status < 200 || status > 299) {
		/* error */
		/* TODO: return a more specific error message,
		 * TODO: based on the status code.
		 */
		plug_closing(p->plug, "Network error: Error while communicating with proxy",
			    PROXY_ERROR_GENERAL, 0);
		return 1;
	    }

	    p->state = 2;
	}

	if (p->state == 2) {

	    /* get headers. we're done when we get a
	     * header of length 2, (ie. just "\r\n")
	     */

	    bufchain_prefix(&p->pending_input_data, &data, &len);
	    eol = get_line_end(data, len);
	    while (eol > 2)
	    {
		/* TODO: Proxy-Auth stuff. in some cases, we will
		 * TODO: need to extract information from headers.
		 */
		bufchain_consume(&p->pending_input_data, eol);
		bufchain_prefix(&p->pending_input_data, &data, &len);
		eol = get_line_end(data, 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 */
		return 1;
	    }

	    return 1;
	}
    }

    plug_closing(p->plug, "Network error: Unexpected proxy error",
		 PROXY_ERROR_UNEXPECTED, 0);
    return 0;
}

/* ----------------------------------------------------------------------
 * SOCKS proxy type (as yet unimplemented).
 */

int proxy_socks_negotiate (Proxy_Socket p, int change)
{
    p->error = "Network error: SOCKS proxy implementation is incomplete";
    return 0;
}

/* ----------------------------------------------------------------------
 * `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.)
 */

int proxy_telnet_negotiate (Proxy_Socket p, int change)
{
    if (p->state == PROXY_CHANGE_NEW) {

	int so = 0, eo = 0;

	/* we need to escape \\, \%, \r, \n, \t, \x??, \0???, 
	 * %%, %host, and %port 
	 */

	while (cfg.proxy_telnet_command[eo] != 0) {

	    /* scan forward until we hit end-of-line, 
	     * or an escape character (\ or %) */
	    while (cfg.proxy_telnet_command[eo] != 0 &&
		   cfg.proxy_telnet_command[eo] != '%' &&
		   cfg.proxy_telnet_command[eo] != '\\') eo++;

	    /* if we hit eol, break out of our escaping loop */
	    if (cfg.proxy_telnet_command[eo] == 0) break;

	    /* if there was any unescaped text before the escape
	     * character, send that now */
	    if (eo != so) {
		sk_write(p->sub_socket, 
			 cfg.proxy_telnet_command + so, eo - so);
	    }

	    so = eo++;

	    /* if the escape character was the last character of
	     * the line, we'll just stop and send it. */
	    if (cfg.proxy_telnet_command[eo] == 0) break;

	    if (cfg.proxy_telnet_command[so] == '\\') {

		/* we recognize \\, \%, \r, \n, \t, \x??. 
		 * anything else, we just send unescaped (including the \). 
		 */

		switch (cfg.proxy_telnet_command[eo]) {

		  case '\\':
		    sk_write(p->sub_socket, "\\", 1);
		    eo++;
		    break;

		  case '%':
		    sk_write(p->sub_socket, "%%", 1);
		    eo++;
		    break;

		  case 'r':
		    sk_write(p->sub_socket, "\r", 1);
		    eo++;
		    break;

		  case 'n':
		    sk_write(p->sub_socket, "\n", 1);
		    eo++;
		    break;

		  case 't':
		    sk_write(p->sub_socket, "\t", 1);
		    eo++;
		    break;

		  case 'x':
		  case 'X':
		    {
		    /* escaped hexadecimal value (ie. \xff) */
		    unsigned char v = 0;
		    int i = 0;

		    for (;;) {
			eo++;
			if (cfg.proxy_telnet_command[eo] >= '0' &&
			    cfg.proxy_telnet_command[eo] <= '9')
			    v += cfg.proxy_telnet_command[eo] - '0';
			else if (cfg.proxy_telnet_command[eo] >= 'a' &&
				 cfg.proxy_telnet_command[eo] <= 'f')
			    v += cfg.proxy_telnet_command[eo] - 'a' + 10;
			else if (cfg.proxy_telnet_command[eo] >= 'A' &&
				 cfg.proxy_telnet_command[eo] <= 'F')
			    v += cfg.proxy_telnet_command[eo] - 'A' + 10;
			else {
			    /* non hex character, so we abort and just
			     * send the whole thing unescaped (including \x)
			     */
			    sk_write(p->sub_socket, "\\", 1);
			    eo = so + 1;
			    break;
			}

			/* we only extract two hex characters */
			if (i == 1) {
			    sk_write(p->sub_socket, &v, 1);
			    eo++;
			    break;
			}

			i++;
			v <<= 4;
		    }
		    }
		    break;

		  default:
		    sk_write(p->sub_socket, 
			     cfg.proxy_telnet_command + so, 2);
		    eo++;
		    break;
		}
	    } else {

		/* % escape. we recognize %%, %host, %port. anything else,
		 * we just send unescaped (including the %). */

		if (cfg.proxy_telnet_command[eo] == '%') {
		    sk_write(p->sub_socket, "%", 1);
		    eo++;
		} 
		else if (strnicmp(cfg.proxy_telnet_command + eo,
				  "host", 4) == 0) {
		    char dest[64];
		    sk_getaddr(p->remote_addr, dest, 64);
		    sk_write(p->sub_socket, dest, strlen(dest));
		    eo += 4;
		} 
		else if (strnicmp(cfg.proxy_telnet_command + eo,
				  "port", 4) == 0) {
		    char port[8];
		    sprintf(port, "%i", p->remote_port);
		    sk_write(p->sub_socket, port, strlen(port));
		    eo += 4;
		} 
		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.
		     */
		    sk_write(p->sub_socket, "%", 1);
		}
	    }

	    /* 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) {
	    sk_write(p->sub_socket, cfg.proxy_telnet_command + so, eo - so);
	}

	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, "Network error: Unexpected proxy error",
		 PROXY_ERROR_UNEXPECTED, 0);
    return 0;
}