/************************************************************************
 *   IRC - Internet Relay Chat, iauth/mod_socks.c
 *   Copyright (C) 1998 Christophe Kalt
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 1, or (at your option)
 *   any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#ifndef lint
static  char rcsid[] = "@(#)$Id: mod_socks.c,v 1.25 1999/08/13 21:06:30 chopin Exp $";
#endif

#include "os.h"
#include "a_defines.h"
#define MOD_SOCKS_C
#include "a_externs.h"
#undef MOD_SOCKS_C

/****************************** PRIVATE *************************************/

#define CACHETIME 30

#define SOCKSPORT 1080

struct proxylog
{
	struct proxylog *next;
	char ip[HOSTLEN+1];
	u_char state; /* 0 = no proxy, 1 = open proxy, 2 = closed proxy */
	time_t expire;
};

#define OPT_LOG     	0x001
#define OPT_DENY    	0x002
#define OPT_PARANOID	0x004
#define OPT_CAREFUL 	0x008
#define OPT_V4ONLY  	0x010
#define OPT_V5ONLY  	0x020
#define OPT_PROTOCOL	0x100

#define PROXY_NONE		0
#define PROXY_OPEN		1
#define PROXY_CLOSE		2
#define PROXY_UNEXPECTED	3
#define PROXY_BADPROTO		4

#define ST_V4	0x01
#define ST_V5	0x02
#define ST_V5b	0x04

struct socks_private
{
	struct proxylog *cache;
	u_int lifetime;
	u_char options;
	/* stats */
	u_int chitc, chito, chitn, cmiss, cnow, cmax;
	u_int closed4, closed5, open4, open5, noprox;
	u_int closed5b, open5b;
};

/*
 * socks_open_proxy
 *
 *	Found an open proxy for cl: deal with it!
 */
static void
socks_open_proxy(cl, strver)
int cl;
char *strver;
{
    struct socks_private *mydata = cldata[cl].instance->data;

    /* open proxy */
    if (mydata->options & OPT_DENY)
	{
	    cldata[cl].state |= A_DENY;
	    sendto_ircd("k %d %s %u ", cl, cldata[cl].itsip,
			cldata[cl].itsport);
	}
    if (mydata->options & OPT_LOG)
	    sendto_log(ALOG_FLOG, LOG_INFO, "socks%s: open proxy: %s[%s]",
		       strver, cldata[cl].host, cldata[cl].itsip);
}

/*
 * socks_add_cache
 *
 *	Add an entry to the cache.
 */
static void
socks_add_cache(cl, state)
int cl, state;
{
    struct socks_private *mydata = cldata[cl].instance->data;
    struct proxylog *next;

    if (state == PROXY_OPEN)
	    if (cldata[cl].mod_status == ST_V4)
		    mydata->open4 += 1;
	    else if (cldata[cl].mod_status == ST_V5)
		    mydata->open5 += 1;
	    else
		    mydata->open5b += 1;
    else if (state == PROXY_NONE)
	    mydata->noprox += 1;
    else /* state == PROXY_CLOSE|PROXY_UNEXPECTED|PROXY_BADPROTO */
	    if (cldata[cl].mod_status == ST_V4)
		    mydata->closed4 += 1;
	    else if (cldata[cl].mod_status == ST_V5)
		    mydata->closed5 += 1;
	    else
		    mydata->closed5b += 1;
    
    if (mydata->lifetime == 0)
	    return;

    mydata->cnow += 1;
    if (mydata->cnow > mydata->cmax)
	    mydata->cmax = mydata->cnow;

    next = mydata->cache;
    mydata->cache = (struct proxylog *)malloc(sizeof(struct proxylog));
    mydata->cache->expire = time(NULL) + mydata->lifetime;
    strcpy(mydata->cache->ip, cldata[cl].itsip);
    mydata->cache->state = state;
    mydata->cache->next = next;
    DebugLog((ALOG_DSOCKSC, 0, "socks_add_cache(%d): new cache %s, open=%d",
	      cl, mydata->cache->ip, state));
}

/*
 * socks_check_cache
 *
 *	Check cache for an entry.
 */
static int
socks_check_cache(cl)
{
    struct socks_private *mydata = cldata[cl].instance->data;
    struct proxylog **last, *pl;
    time_t now = time(NULL);

    if (mydata->lifetime == 0)
	    return 0;

    DebugLog((ALOG_DSOCKSC, 0, "socks_check_cache(%d): Checking cache for %s",
	      cl, cldata[cl].itsip));

    last = &(mydata->cache);
    while (pl = *last)
	{
	    DebugLog((ALOG_DSOCKSC, 0, "socks_check_cache(%d): cache %s",
		      cl, pl->ip));
	    if (pl->expire < now)
		{
		    DebugLog((ALOG_DSOCKSC, 0,
			      "socks_check_cache(%d): free %s (%d < %d)",
			      cl, pl->ip, pl->expire, now));
		    *last = pl->next;
		    free(pl);
		    mydata->cnow -= 1;
		    continue;
		}
	    if (!strcasecmp(pl->ip, cldata[cl].itsip))
		{
		    DebugLog((ALOG_DSOCKSC, 0,
			      "socks_check_cache(%d): match (%u)",
			      cl, pl->state));
		    pl->expire = now + mydata->lifetime; /* dubious */
		    if (pl->state == 1)
			{
			    socks_open_proxy(cl, "C");
			    mydata->chito += 1;
			}
		    else if (pl->state == 0)
			    mydata->chitn += 1;
		    else
			    mydata->chitc += 1;
		    return -1;
		}
	    last = &(pl->next);
	}
    mydata->cmiss += 1;
    return 0;
}

static int
socks_write(cl, strver)
u_int cl;
char *strver;
{
    u_char query[13];    /* big enough to hold all queries */
    int query_len = 13;  /* lenght of socks4 query */
    u_int a, b, c, d;
    
    if (sscanf(cldata[cl].ourip, "%u.%u.%u.%u", &a,&b,&c,&d) != 4)
	{
	    sendto_log(ALOG_DSOCKS|ALOG_IRCD, LOG_ERR,
		       "socks_write%s(%d): sscanf(\"%s\") failed", 
		       strver, cl, cldata[cl].ourip);
	    close(cldata[cl].wfd);
	    cldata[cl].wfd = 0;
	    return -1;
	}
    if (cldata[cl].mod_status == ST_V4)
	{
	    query[0] = 4; query[1] = 1;
	    query[2] = ((cldata[cl].ourport & 0xff00) >> 8);
	    query[3] = (cldata[cl].ourport & 0x00ff);
	    query[4] = a; query[5] = b; query[6] = c; query[7] = d;
	    query[8] = 'u'; query[9] = 's'; query[10] = 'e'; query[11] = 'r';
	    query[12] = 0;
	}
    else 
	{
	    query[0] = 5; query[1] = 1; query[2] = 0;
	    query_len = 3;
	    if (cldata[cl].mod_status == ST_V5b)
		{
		    query_len = 10;
		    query[3] = 1;
		    query[4] = a; query[5] = b; query[6] = c; query[7] = d;
		    query[8] = ((cldata[cl].ourport & 0xff00) >>8);
		    query[9] = (cldata[cl].ourport & 0x00ff);
		}
	}
    
    DebugLog((ALOG_DSOCKS, 0, "socks%s_write(%d): Checking %s %u",
	      strver, cl, cldata[cl].ourip, SOCKSPORT));
    if (write(cldata[cl].wfd, query, query_len) != query_len)
	{
	    /* most likely the connection failed */
	    DebugLog((ALOG_DSOCKS, 0, "socks%s_write(%d): write() failed: %s",
		      strver, cl, strerror(errno)));
	    socks_add_cache(cl, PROXY_NONE, 0);
	    close(cldata[cl].wfd);
	    cldata[cl].rfd = cldata[cl].wfd = 0;
	    return 1;
	}
    cldata[cl].rfd = cldata[cl].wfd;
    cldata[cl].wfd = 0;
    return 0;
}

static int
socks_read(cl, strver)
u_int cl;
char *strver;
{
    struct socks_private *mydata = cldata[cl].instance->data;
    int again = 0;
    u_char state = PROXY_CLOSE;
    
    /* data's in from the other end */
    if (cldata[cl].buflen < 2)
	    return 0;
    
    /* got all we need */
    DebugLog((ALOG_DSOCKS, 0, "socks%s_read(%d): Got [%d %d]", strver, cl,
	      cldata[cl].inbuffer[0], cldata[cl].inbuffer[1]));
    
    if (cldata[cl].mod_status == ST_V4)
	{
	    if (cldata[cl].inbuffer[0] == 0)
		{
		    if (cldata[cl].inbuffer[1] < 90 ||
			cldata[cl].inbuffer[1] > 93)
			    state = PROXY_UNEXPECTED;
		    else
			{
			    if (cldata[cl].inbuffer[1] == 90)
				    state = PROXY_OPEN;
			    else if ((mydata->options & OPT_PARANOID) &&
				     cldata[cl].inbuffer[1] != 91)
				    state = PROXY_OPEN;
			}
		}
	    else
		    state = PROXY_BADPROTO;
	}
    else /* ST_V5 or ST_V5b */
	{
	    if (cldata[cl].inbuffer[0] == 5)
		    if (cldata[cl].inbuffer[1] == 0)
			    state = PROXY_OPEN;
		    else
			{
			    if (cldata[cl].mod_status == ST_V5)
				{
				    if ((u_char)cldata[cl].inbuffer[1] == 4 ||
					((u_char)cldata[cl].inbuffer[1] > 9 &&
					(u_char)cldata[cl].inbuffer[1] != 255))
					    state = PROXY_UNEXPECTED;
				}
			    else /* ST_V5b */
				    if ((u_char) cldata[cl].inbuffer[1] > 8)
					    state = PROXY_UNEXPECTED;
				    else if ((mydata->options&OPT_PARANOID) &&
					     cldata[cl].inbuffer[1] != 2)
					    state = PROXY_OPEN;
			}
	    else
		    state = PROXY_BADPROTO;
	}
    
    if (cldata[cl].mod_status == ST_V4 && state != PROXY_OPEN &&
	!(mydata->options & OPT_V4ONLY))
	{
	    cldata[cl].mod_status = ST_V5;
	    cldata[cl].buflen=0;
	    close(cldata[cl].rfd);
	    cldata[cl].rfd = 0;
	    again = 1;
	}
    
    if (cldata[cl].mod_status == ST_V5 && state == PROXY_OPEN &&
	(mydata->options & OPT_CAREFUL))
	{
	    cldata[cl].mod_status = ST_V5b;
	    cldata[cl].buflen=0;
	    close(cldata[cl].rfd);
	    cldata[cl].rfd = 0;
	    again = 1;
	}
    
    if (state == PROXY_OPEN && again == 0)
	    socks_open_proxy(cl, strver);
    
    if (state == PROXY_UNEXPECTED)
	{
	    sendto_log(ALOG_FLOG, LOG_WARNING,
		       "socks%s: unexpected reply: %u,%u %s[%s]", strver,
		       cldata[cl].inbuffer[0], cldata[cl].inbuffer[1],
		       cldata[cl].host, cldata[cl].itsip);
	    sendto_log(ALOG_IRCD, 0, "socks%s: unexpected reply: %u,%u",
		       strver, cldata[cl].inbuffer[0],
		       cldata[cl].inbuffer[1]);
	    state = PROXY_CLOSE;
	}
    
    if (state == PROXY_BADPROTO && (mydata->options & OPT_PROTOCOL))
	{
	    sendto_log(ALOG_FLOG, LOG_WARNING,
		       "socks%s: protocol error: %u,%u %s[%s]", strver,
		       cldata[cl].inbuffer[0], cldata[cl].inbuffer[1],
		       cldata[cl].host, cldata[cl].itsip);
	    sendto_log(ALOG_IRCD, 0, "socks%s: protocol error: %u,%u",
		       strver, cldata[cl].inbuffer[0],
		       cldata[cl].inbuffer[1]);
	    state = PROXY_CLOSE;
	}
    
    if (again == 1)
	    return socks_start(cl);
    else
	{
	    socks_add_cache(cl, state);
	    close(cldata[cl].rfd);
	    cldata[cl].rfd = 0;
	    return -1;
	}
    return 0;
}

/******************************** PUBLIC ************************************/

/*
 * socks_init
 *
 *	This procedure is called when a particular module is loaded.
 *	Returns NULL if everything went fine,
 *	an error message otherwise.
 */
char *
socks_init(self)
AnInstance *self;
{
    struct socks_private *mydata;
    char tmpbuf[80], cbuf[32];
    static char txtbuf[80];
    
#if defined(INET6)
    return "IPv6 unsupported.";
#endif
    if (self->opt == NULL)
	    return "Aie! no option(s): nothing to be done!";
    
    mydata = (struct socks_private *) malloc(sizeof(struct socks_private));
    bzero((char *) mydata, sizeof(struct socks_private));
    mydata->cache = NULL;
    mydata->lifetime = CACHETIME;
    
    tmpbuf[0] = txtbuf[0] = '\0';
    if (strstr(self->opt, "log"))
	{
	    mydata->options |= OPT_LOG;
	    strcat(tmpbuf, ",log");
	    strcat(txtbuf, ", Log");
	}
    if (strstr(self->opt, "reject"))
	{
	    mydata->options |= OPT_DENY;
	    strcat(tmpbuf, ",reject");
	    strcat(txtbuf, ", Reject");
	}
    if (strstr(self->opt, "paranoid"))
	{
	    mydata->options |= OPT_PARANOID;
	    strcat(tmpbuf, ",paranoid");
	    strcat(txtbuf, ", Paranoid");
	}
    if (strstr(self->opt, "careful"))
	{
	    mydata->options |= OPT_CAREFUL;
	    strcat(tmpbuf, ",careful");
	    strcat(txtbuf, ", Careful");
	}
    if (strstr(self->opt, "v4only"))
	{
	    mydata->options |= OPT_V4ONLY;
	    strcat(tmpbuf, ",v4only");
	    strcat(txtbuf, ", V4only");
	}
    if (strstr(self->opt, "v5only"))
	{
	    mydata->options |= OPT_V5ONLY;
	    strcat(tmpbuf, ",v5only");
	    strcat(txtbuf, ", V5only");
	}
    if (strstr(self->opt, "protocol"))
	{
	    mydata->options |= OPT_PROTOCOL;
	    strcat(tmpbuf, ",protocol");
	    strcat(txtbuf, ", Protocol");
	}
    
    if (mydata->options == 0)
	    return "Aie! unknown option(s): nothing to be done!";
    
    if (strstr(self->opt, "cache"))
	{
	    char *ch = index(self->opt, '=');
	    
	    if (ch)
		    mydata->lifetime = atoi(ch+1);
	}
    sprintf(cbuf, ",cache=%d", mydata->lifetime);
    strcat(tmpbuf, cbuf);
    sprintf(cbuf, ", Cache %d (min)", mydata->lifetime);
    strcat(txtbuf, cbuf);
    mydata->lifetime *= 60;
    
    self->popt = mystrdup(tmpbuf+1);
    self->data = mydata;
    return txtbuf+2;
}

/*
 * socks_release
 *
 *	This procedure is called when a particular module is unloaded.
 */
void
socks_release(self)
AnInstance *self;
{
    struct sock_private *mydata = self->data;
    free(mydata);
    free(self->popt);
}

/*
 * socks_stats
 *
 *	This procedure is called regularly to update statistics sent to ircd.
 */
void
socks_stats(self)
AnInstance *self;
{
    struct socks_private *mydata = self->data;

    sendto_ircd("S socks open %u/%u/%u closed %u/%u/%u noproxy %u",
		mydata->open4, mydata->open5, mydata->open5b,
		mydata->closed4, mydata->closed5, mydata->closed5b,
		mydata->noprox);
    sendto_ircd("S socks cache open %u closed %u noproxy %u miss %u (%u <= %u)",
		mydata->chito, mydata->chitc, mydata->chitn,
		mydata->cmiss, mydata->cnow, mydata->cmax);
}

/*
 * socks_start
 *
 *	This procedure is called to start the socks check procedure.
 *	Returns 0 if everything went fine,
 *	-1 otherwise (nothing to be done, or failure)
 *
 *	It is responsible for sending error messages where appropriate.
 *	In case of failure, it's responsible for cleaning up (e.g. socks_clean
 *	will NOT be called)
 */
int
socks_start(cl)
u_int cl;
{
    struct socks_private *mydata = cldata[cl].instance->data;
    char *error;
    int fd;
    
    if (cldata[cl].state & A_DENY)
	{
	    /* no point of doing anything */
	    DebugLog((ALOG_DSOCKS, 0,
		      "socks_start(%d): A_DENY alredy set ", cl));
	    return -1;
	}
    
    if (socks_check_cache(cl))
	    return -1;
    
    DebugLog((ALOG_DSOCKS, 0, "socks_start(%d): Connecting to %s", cl,
	      cldata[cl].itsip));
    fd= tcp_connect(cldata[cl].ourip, cldata[cl].itsip, SOCKSPORT, &error);
    if (fd < 0)
	{
	    DebugLog((ALOG_DSOCKS, 0,
		      "socks_start(%d): tcp_connect() reported %s", cl,error));
	    socks_add_cache(cl, PROXY_NONE, 0);
	    return -1;
	}

    cldata[cl].wfd = fd; /*so that socks_work() is called when connected*/

    return 0;
}

/*
 * socks_work
 *
 *	This procedure is called whenever there's new data in the buffer.
 *	Returns 0 if everything went fine, and there is more work to be done,
 *	Returns -1 if the module has finished its work (and cleaned up).
 *
 *	It is responsible for sending error messages where appropriate.
 */
int
socks_work(cl)
u_int cl;
{
    char *strver = "4";
    struct socks_private *mydata = cldata[cl].instance->data;
    
    if (cldata[cl].mod_status == 0)
	    if (mydata->options & OPT_V5ONLY)
		    cldata[cl].mod_status = ST_V5;
	    else
		    cldata[cl].mod_status = ST_V4;
    
    if (cldata[cl].mod_status & ST_V5)
	    strver = "5";
    else if (cldata[cl].mod_status & ST_V5b)
	    strver = "5b";
    
    DebugLog((ALOG_DSOCKS, 0, "socks%s_work(%d): %d %d buflen=%d", strver,
	      cl, cldata[cl].rfd, cldata[cl].wfd, cldata[cl].buflen));
    
    if (cldata[cl].wfd > 0)
	    /*
	    ** We haven't sent the query yet, the connection was just
	    ** established.
	    */
	    return socks_write(cl, strver);
    else
	    return socks_read(cl, strver);
}

/*
 * socks_clean
 *
 *	This procedure is called whenever the module should interrupt its work.
 *	It is responsible for cleaning up any allocated data, and in particular
 *	closing file descriptors.
 */
void
socks_clean(cl)
u_int cl;
{
    DebugLog((ALOG_DSOCKS, 0, "socks_clean(%d): cleaning up", cl));
    /*
    ** only one of rfd and wfd may be set at the same time,
    ** in any case, they would be the same fd, so only close() once
    */
    if (cldata[cl].rfd)
	    close(cldata[cl].rfd);
    else if (cldata[cl].wfd)
	    close(cldata[cl].wfd);
    cldata[cl].rfd = cldata[cl].wfd = 0;
}

/*
 * socks_timeout
 *
 *	This procedure is called whenever the timeout set by the module is
 *	reached.
 *
 *	Returns 0 if things are okay, -1 if check was aborted.
 */
int
socks_timeout(cl)
u_int cl;
{
    DebugLog((ALOG_DSOCKS, 0, "socks_timeout(%d): calling socks_clean ", cl));
    socks_clean(cl);
    return -1;
}

aModule Module_socks =
	{ "socks", socks_init, socks_release, socks_stats,
	  socks_start, socks_work, socks_timeout, socks_clean };