/*
 * 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(cfg) \
    (cfg->proxy_dns == FORCE_ON || \
	 (cfg->proxy_dns == AUTO && \
              cfg->proxy_type != PROXY_SOCKS4 && \
              cfg->proxy_type != PROXY_SOCKS5))

/*
 * 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 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_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 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,
				  const Config *cfg)
{
    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 (!cfg->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 = 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((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,
		     const Config *cfg)
{
    if (cfg->proxy_type != PROXY_NONE &&
	do_proxy_dns(cfg) &&
	proxy_for_destination(NULL, host, port, cfg)) {
	*canonicalname = dupstr(host);
	return sk_nonamelookup(host);
    }

    return sk_namelookup(host, canonicalname);
}

Socket new_connection(SockAddr addr, char *hostname,
		      int port, int privport,
		      int oobinline, int nodelay, int keepalive,
		      Plug plug, const Config *cfg)
{
    static const 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 const 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, cfg))
    {
	Proxy_Socket ret;
	Proxy_Plug pplug;
	SockAddr proxy_addr;
	char *proxy_canonical_name;
	Socket sret;

	if ((sret = platform_new_connection(addr, hostname, port, privport,
					    oobinline, nodelay, keepalive,
					    plug, cfg)) !=
	    NULL)
	    return sret;

	ret = snew(struct Socket_proxy_tag);
	ret->fn = &socket_fn_table;
	ret->cfg = *cfg;	       /* STRUCTURE COPY */
	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->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;
	
	if (cfg->proxy_type == PROXY_HTTP) {
	    ret->negotiate = proxy_http_negotiate;
	} else if (cfg->proxy_type == PROXY_SOCKS4) {
            ret->negotiate = proxy_socks4_negotiate;
	} else if (cfg->proxy_type == PROXY_SOCKS5) {
            ret->negotiate = proxy_socks5_negotiate;
	} else if (cfg->proxy_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(cfg->proxy_host,
				   &proxy_canonical_name);
	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, cfg->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,
		    const Config *cfg)
{
    /* TODO: SOCKS (and potentially others) support inbound
     * TODO: connections via the proxy. support them.
     */

    return sk_newlistener(srcaddr, port, plug, local_host_only);
}

/* ----------------------------------------------------------------------
 * HTTP CONNECT proxy type.
 */

static int get_line_end (char * data, int len)
{
    int off = 0;

    while (off < len)
    {