mailsrvr.c

/* mailsrvr.c */

/* Synchronet Mail (SMTP/POP3) server and sendmail threads */

/* $Id$ */

/****************************************************************************
 * @format.tab-size 4		(Plain Text/Source Code File Header)			*
 * @format.use-tabs true	(see http://www.synchro.net/ptsc_hdr.html)		*
 *																			*
 * Copyright 2009 Rob Swindell - http://www.synchro.net/copyright.html		*
 *																			*
 * 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 2			*
 * of the License, or (at your option) any later version.					*
 * See the GNU General Public License for more details: gpl.txt or			*
 * http://www.fsf.org/copyleft/gpl.html										*
 *																			*
 * Anonymous FTP access to the most recent released source is available at	*
 * ftp://vert.synchro.net, ftp://cvs.synchro.net and ftp://ftp.synchro.net	*
 *																			*
 * Anonymous CVS access to the development source and modification history	*
 * is available at cvs.synchro.net:/cvsroot/sbbs, example:					*
 * cvs -d :pserver:anonymous@cvs.synchro.net:/cvsroot/sbbs login			*
 *     (just hit return, no password is necessary)							*
 * cvs -d :pserver:anonymous@cvs.synchro.net:/cvsroot/sbbs checkout src		*
 *																			*
 * For Synchronet coding style and modification guidelines, see				*
 * http://www.synchro.net/source.html										*
 *																			*
 * You are encouraged to submit any modifications (preferably in Unix diff	*
 * format) via e-mail to mods@synchro.net									*
 *																			*
 * Note: If this box doesn't appear square, then you need to fix your tabs.	*
 ****************************************************************************/

/* ANSI C Library headers */
#include <limits.h>			/* UINT_MAX */
#include <stdio.h>
#include <stdlib.h>			/* ltoa in GNU C lib */
#include <stdarg.h>			/* va_list */
#include <string.h>			/* strrchr */
#include <ctype.h>			/* isdigit */
#include <fcntl.h>			/* Open flags */
#include <errno.h>			/* errno */

/* Synchronet-specific headers */
#undef SBBS	/* this shouldn't be defined unless building sbbs.dll/libsbbs.so */
#include "sbbs.h"
#include "mailsrvr.h"
#include "mime.h"
#include "md5.h"
#include "crc32.h"
#include "base64.h"
#include "ini_file.h"
#include "netwrap.h"	/* getNameServerList() */
#include "xpendian.h"
#include "js_rtpool.h"
#include "js_request.h"

/* Constants */
static const char*	server_name="Synchronet Mail Server";
#define FORWARD			"forward:"
#define NO_FORWARD		"local:"

int dns_getmx(char* name, char* mx, char* mx2
			  ,DWORD intf, DWORD ip_addr, BOOL use_tcp, int timeout);

static char* pop_err	=	"-ERR";
static char* ok_rsp		=	"250 OK";
static char* auth_ok	=	"235 User Authenticated";
static char* sys_error	=	"421 System error";
static char* sys_unavail=	"421 System unavailable, try again later";
static char* insuf_stor =	"452 Insufficient system storage";
static char* badarg_rsp =	"501 Bad argument";
static char* badseq_rsp	=	"503 Bad sequence of commands";
static char* badauth_rsp=	"535 Authentication failure";
static char* badrsp_err	=	"%s replied with:\r\n\"%s\"\r\n"
							"instead of the expected reply:\r\n\"%s ...\"";

#define TIMEOUT_THREAD_WAIT		60		/* Seconds */
#define DNSBL_THROTTLE_VALUE	5000	/* Milliseconds */
#define SPAM_HASH_SUBJECT_MIN_LEN	10	/* characters */

#define STATUS_WFC	"Listening"

static mail_startup_t* startup=NULL;
static scfg_t	scfg;
static SOCKET	server_socket=INVALID_SOCKET;
static SOCKET	submission_socket=INVALID_SOCKET;
static SOCKET	pop3_socket=INVALID_SOCKET;
static ulong	active_clients=0;
static int		active_sendmail=0;
static ulong	thread_count=0;
static BOOL		sendmail_running=FALSE;
static BOOL		terminate_server=FALSE;
static BOOL		terminate_sendmail=FALSE;
static sem_t	sendmail_wakeup_sem;
static char		revision[16];
static time_t	uptime;
static str_list_t recycle_semfiles;
static str_list_t shutdown_semfiles;
static int		mailproc_count;
static js_server_props_t js_server_props;

struct {
	ulong	sockets;
	ulong	errors;
	ulong	crit_errors;
	ulong	connections_ignored;
	ulong	connections_refused;
	ulong	connections_served;
	ulong	pop3_served;
	ulong	smtp_served;
	/* SMTP: */
	ulong	sessions_refused;
	ulong	msgs_ignored;
	ulong	msgs_refused;
	ulong	msgs_received;
} stats;

struct mailproc {
	char		name[INI_MAX_VALUE_LEN];
	char		cmdline[INI_MAX_VALUE_LEN];
	char		eval[INI_MAX_VALUE_LEN];
	str_list_t	to;
	str_list_t	from;
	BOOL		passthru;
	BOOL		native;
	BOOL		ignore_on_error;	/* Ignore mail message if cmdline fails */
	BOOL		disabled;
	BOOL		process_spam;
	BOOL		process_dnsbl;
	uint8_t*	ar;
	ulong		handled;			/* counter (for stats display) */
} *mailproc_list;

typedef struct {
	SOCKET			socket;
	SOCKADDR_IN		client_addr;
} smtp_t,pop3_t;

static int lprintf(int level, const char *fmt, ...)
{
	va_list argptr;
	char sbuf[1024];

	va_start(argptr,fmt);
    vsnprintf(sbuf,sizeof(sbuf),fmt,argptr);
	sbuf[sizeof(sbuf)-1]=0;
    va_end(argptr);

	if(level <= LOG_ERR)
		errorlog(&scfg,startup==NULL ? NULL:startup->host_name,sbuf), stats.errors++;

	if(level <= LOG_CRIT)
		stats.crit_errors++;

    if(startup==NULL || startup->lputs==NULL || level > startup->log_level)
		return(0);

#if defined(_WIN32)
	if(IsBadCodePtr((FARPROC)startup->lputs))
		return(0);
#endif

    return(startup->lputs(startup->cbdata,level,sbuf));
}

#ifdef _WINSOCKAPI_

static WSADATA WSAData;
#define SOCKLIB_DESC WSAData.szDescription
static BOOL WSAInitialized=FALSE;

static BOOL winsock_startup(void)
{
	int		status;             /* Status Code */

    if((status = WSAStartup(MAKEWORD(1,1), &WSAData))==0) {
		lprintf(LOG_DEBUG,"%s %s",WSAData.szDescription, WSAData.szSystemStatus);
		WSAInitialized=TRUE;
		return (TRUE);
	}

    lprintf(LOG_CRIT,"!WinSock startup ERROR %d", status);
	return (FALSE);
}

#else /* No WINSOCK */

#define winsock_startup()	(TRUE)
#define SOCKLIB_DESC NULL

#endif

static void update_clients(void)
{
	if(startup!=NULL && startup->clients!=NULL)
		startup->clients(startup->cbdata,active_clients+active_sendmail);
}

static void client_on(SOCKET sock, client_t* client, BOOL update)
{
	if(startup!=NULL && startup->client_on!=NULL)
		startup->client_on(startup->cbdata,TRUE,sock,client,update);
}

static void client_off(SOCKET sock)
{
	if(startup!=NULL && startup->client_on!=NULL)
		startup->client_on(startup->cbdata,FALSE,sock,NULL,FALSE);
}

static void thread_up(BOOL setuid)
{
	thread_count++;
	if(startup!=NULL && startup->thread_up!=NULL)
		startup->thread_up(startup->cbdata,TRUE,setuid);
}

static void thread_down(void)
{
	if(thread_count>0)
		thread_count--;
	if(startup!=NULL && startup->thread_up!=NULL)
		startup->thread_up(startup->cbdata,FALSE,FALSE);
}

SOCKET mail_open_socket(int type, const char* protocol)
{
	char	error[256];
	char	section[128];
	SOCKET	sock;

	sock=socket(AF_INET, type, IPPROTO_IP);
	if(sock!=INVALID_SOCKET && startup!=NULL && startup->socket_open!=NULL) 
		startup->socket_open(startup->cbdata,TRUE);
	if(sock!=INVALID_SOCKET) {
		SAFEPRINTF(section,"mail|%s",protocol);
		if(set_socket_options(&scfg, sock, section, error, sizeof(error)))
			lprintf(LOG_ERR,"%04d !ERROR %s",sock,error);

		stats.sockets++;
#if 0 /*def _DEBUG */
		lprintf(LOG_DEBUG,"%04d Socket opened (%d sockets in use)",sock,stats.sockets);
#endif
	}
	return(sock);
}

int mail_close_socket(SOCKET sock)
{
	int		result;

	if(sock==INVALID_SOCKET)
		return(-1);

	shutdown(sock,SHUT_RDWR);	/* required on Unix */
	result=closesocket(sock);
	if(startup!=NULL && startup->socket_open!=NULL)
		startup->socket_open(startup->cbdata,FALSE);
	stats.sockets--;
	if(result!=0) {
		if(ERROR_VALUE!=ENOTSOCK)
			lprintf(LOG_WARNING,"%04d !ERROR %d closing socket",sock, ERROR_VALUE);
	}
#if 0 /*def _DEBUG */
	else 
		lprintf(LOG_DEBUG,"%04d Socket closed (%d sockets in use)",sock,stats.sockets);
#endif

	return(result);
}

static void status(char* str)
{
	if(startup!=NULL && startup->status!=NULL)
	    startup->status(startup->cbdata,str);
}

int sockprintf(SOCKET sock, char *fmt, ...)
{
	int		len;
	int		maxlen;
	int		result;
	va_list argptr;
	char	sbuf[1024];
	fd_set	socket_set;
	struct timeval tv;

    va_start(argptr,fmt);
    len=vsnprintf(sbuf,maxlen=sizeof(sbuf)-2,fmt,argptr);
    va_end(argptr);

	if(len<0 || len > maxlen) /* format error or output truncated */
		len=maxlen;
	if(startup->options&MAIL_OPT_DEBUG_TX)
		lprintf(LOG_DEBUG,"%04d TX: %.*s", sock, len, sbuf);
	memcpy(sbuf+len,"\r\n",2);
	len+=2;

	if(sock==INVALID_SOCKET) {
		lprintf(LOG_WARNING,"!INVALID SOCKET in call to sockprintf");
		return(0);
	}

	/* Check socket for writability (using select) */
	tv.tv_sec=300;
	tv.tv_usec=0;

	FD_ZERO(&socket_set);
	FD_SET(sock,&socket_set);

	if((result=select(sock+1,NULL,&socket_set,NULL,&tv))<1) {
		if(result==0)
			lprintf(LOG_NOTICE,"%04d !TIMEOUT selecting socket for send"
				,sock);
		else
			lprintf(LOG_NOTICE,"%04d !ERROR %d selecting socket for send"
				,sock, ERROR_VALUE);
		return(0);
	}

	while((result=sendsocket(sock,sbuf,len))!=len) {
		if(result==SOCKET_ERROR) {
			if(ERROR_VALUE==EWOULDBLOCK) {
				YIELD();
				continue;
			}
			if(ERROR_VALUE==ECONNRESET) 
				lprintf(LOG_NOTICE,"%04d Connection reset by peer on send",sock);
			else if(ERROR_VALUE==ECONNABORTED) 
				lprintf(LOG_NOTICE,"%04d Connection aborted by peer on send",sock);
			else
				lprintf(LOG_NOTICE,"%04d !ERROR %d sending on socket",sock,ERROR_VALUE);
			return(0);
		}
		lprintf(LOG_WARNING,"%04d !ERROR: short send on socket: %d instead of %d",sock,result,len);
	}
	return(len);
}

static void sockerror(SOCKET socket, int rd, const char* action)
{
	if(rd==0) 
		lprintf(LOG_NOTICE,"%04d Socket closed by peer on %s"
			,socket, action);
	else if(rd==SOCKET_ERROR) {
		if(ERROR_VALUE==ECONNRESET) 
			lprintf(LOG_NOTICE,"%04d Connection reset by peer on %s"
				,socket, action);
		else if(ERROR_VALUE==ECONNABORTED) 
			lprintf(LOG_NOTICE,"%04d Connection aborted by peer on %s"
				,socket, action);
		else
			lprintf(LOG_NOTICE,"%04d !SOCKET ERROR %d on %s"
				,socket, ERROR_VALUE, action);
	} else
		lprintf(LOG_WARNING,"%04d !SOCKET ERROR: unexpected return value %d from %s"
			,socket, rd, action);
}


static int sockreadline(SOCKET socket, char* buf, int len)
{
	char	ch;
	int		i,rd=0;
	fd_set	socket_set;
	struct	timeval	tv;
	time_t	start;

	buf[0]=0;

	start=time(NULL);

	if(socket==INVALID_SOCKET) {
		lprintf(LOG_WARNING,"!INVALID SOCKET in call to sockreadline");
		return(-1);
	}
	
	while(rd<len-1) {

		if(server_socket==INVALID_SOCKET || terminate_server) {
			lprintf(LOG_WARNING,"%04d !ABORTING sockreadline",socket);
			return(-1);
		}

		tv.tv_sec=startup->max_inactivity;
		tv.tv_usec=0;

		FD_ZERO(&socket_set);
		FD_SET(socket,&socket_set);

		i=select(socket+1,&socket_set,NULL,NULL,&tv);

		if(i<1) {
			if(i==0) {
				if((time(NULL)-start)>startup->max_inactivity) {
					lprintf(LOG_WARNING,"%04d !SOCKET INACTIVE",socket);
					return(-1);
				}
				continue;
			}
			sockerror(socket,i,"select");
			return(-1);
		}
		i=recv(socket, &ch, 1, 0);
		if(i<1) {
			sockerror(socket,i,"receive");
			return(-1);
		}
		if(ch=='\n' /* && rd>=1 */ ) { /* Mar-9-2003: terminate on sole LF */
			break;
		}	
		buf[rd++]=ch;
	}
	if(rd>0 && buf[rd-1]=='\r')
		rd--;
	buf[rd]=0;
	
	return(rd);
}

static BOOL sockgetrsp(SOCKET socket, char* rsp, char *buf, int len)
{
	int rd;

	while(1) {
		rd = sockreadline(socket, buf, len);
		if(rd<1) 
			return(FALSE);
		if(buf[3]=='-')	{ /* Multi-line response */
			if(startup->options&MAIL_OPT_DEBUG_RX_RSP) 
				lprintf(LOG_DEBUG,"%04d RX: %s",socket,buf);
			continue;
		}
		if(rsp!=NULL && strnicmp(buf,rsp,strlen(rsp))) {
			lprintf(LOG_WARNING,"%04d !INVALID RESPONSE: '%s' Expected: '%s'", socket, buf, rsp);
			return(FALSE);
		}
		break;
	}
	if(startup->options&MAIL_OPT_DEBUG_RX_RSP) 
		lprintf(LOG_DEBUG,"%04d RX: %s",socket,buf);
	return(TRUE);
}

/* RFC822: The maximum total length of a text line including the
   <CRLF> is 1000 characters (but not counting the leading
   dot duplicated for transparency). 

   POP3 (RFC1939) actually calls for a 512 byte line length limit!
*/
#define MAX_LINE_LEN	998		

static ulong sockmimetext(SOCKET socket, smbmsg_t* msg, char* msgtxt, ulong maxlines
						  ,str_list_t file_list, char* mime_boundary)
{
	char		toaddr[256]="";
	char		fromaddr[256]="";
	char		fromhost[256];
	char		msgid[256];
	char		date[64];
	uchar*		p;
	uchar*		np;
	char*		content_type=NULL;
	int			i;
	int			s;
	ulong		lines;
	int			len,tlen;

	/* HEADERS (in recommended order per RFC822 4.1) */

	if(msg->reverse_path!=NULL)
		if(!sockprintf(socket,"Return-Path: %s", msg->reverse_path))
			return(0);

	for(i=0;i<msg->total_hfields;i++)
		if(msg->hfield[i].type == SMTPRECEIVED && msg->hfield_dat[i]!=NULL) 
			if(!sockprintf(socket,"Received: %s", msg->hfield_dat[i]))
				return(0);

	if(!sockprintf(socket,"Date: %s",msgdate(msg->hdr.when_written,date)))
		return(0);

	if((p=smb_get_hfield(msg,RFC822FROM,NULL))!=NULL)
		s=sockprintf(socket,"From: %s",p);	/* use original RFC822 header field */
	else {
		if(msg->from_net.type==NET_QWK && msg->from_net.addr!=NULL)
			SAFEPRINTF2(fromaddr,"%s!%s"
				,(char*)msg->from_net.addr
				,usermailaddr(&scfg,fromhost,msg->from));
		else if(msg->from_net.type==NET_FIDO && msg->from_net.addr!=NULL)
			SAFECOPY(fromaddr,smb_faddrtoa((faddr_t *)msg->from_net.addr,NULL));
		else if(msg->from_net.type!=NET_NONE && msg->from_net.addr!=NULL)
			SAFECOPY(fromaddr,(char*)msg->from_net.addr);
		else 
			usermailaddr(&scfg,fromaddr,msg->from);
		if(fromaddr[0]=='<')
			s=sockprintf(socket,"From: \"%s\" %s",msg->from,fromaddr);
		else
			s=sockprintf(socket,"From: \"%s\" <%s>",msg->from,fromaddr);
	}
	if(!s)
		return(0);

	if(msg->from_org!=NULL || msg->from_net.type==NET_NONE)
		if(!sockprintf(socket,"Organization: %s"
			,msg->from_org==NULL ? scfg.sys_name : msg->from_org))
			return(0);

	if(!sockprintf(socket,"Subject: %s",msg->subj))
		return(0);

	if((p=smb_get_hfield(msg,RFC822TO,NULL))!=NULL)
		s=sockprintf(socket,"To: %s",p);	/* use original RFC822 header field */
	else {
		if(strchr(msg->to,'@')!=NULL || msg->to_net.addr==NULL)
			s=sockprintf(socket,"To: %s",msg->to);	/* Avoid double-@ */
		else if(msg->to_net.type==NET_INTERNET || msg->to_net.type==NET_QWK) {
			if(strchr((char*)msg->to_net.addr,'<')!=NULL)
				s=sockprintf(socket,"To: %s",(char*)msg->to_net.addr);
			else
				s=sockprintf(socket,"To: \"%s\" <%s>",msg->to,(char*)msg->to_net.addr);
		} else {
			usermailaddr(&scfg,toaddr,msg->to);
			s=sockprintf(socket,"To: \"%s\" <%s>",msg->to,toaddr);
		}
	}
	if(!s)
		return(0);
	if((p=smb_get_hfield(msg,SMB_CARBONCOPY,NULL))!=NULL)
		if(!sockprintf(socket,"CC: %s",p))
			return(0);
	np=NULL;
	if((p=smb_get_hfield(msg,RFC822REPLYTO,NULL))==NULL) {
		np=msg->replyto;
		if(msg->replyto_net.type==NET_INTERNET)
			p=msg->replyto_net.addr;
	}
	if(p!=NULL) {
		if(np!=NULL)
			s=sockprintf(socket,"Reply-To: \"%s\" <%s>",np,p);
		else 
			s=sockprintf(socket,"Reply-To: %s",p);
	}
	if(!s)
		return(0);
	if(!sockprintf(socket,"Message-ID: %s",get_msgid(&scfg,INVALID_SUB,msg,msgid,sizeof(msgid))))
		return(0);
	if(msg->reply_id!=NULL)
		if(!sockprintf(socket,"In-Reply-To: %s",msg->reply_id))
			return(0);

    for(i=0;i<msg->total_hfields;i++) { 
		if(msg->hfield[i].type==RFC822HEADER) { 
			if(strnicmp((char*)msg->hfield_dat[i],"Content-Type:",13)==0)
				content_type=msg->hfield_dat[i];
			if(!sockprintf(socket,"%s",(char*)msg->hfield_dat[i]))
				return(0);
        }
    }
	/* Default MIME Content-Type for non-Internet messages */
	if(msg->from_net.type!=NET_INTERNET && content_type==NULL && startup->default_charset[0]) {
		/* No content-type specified, so assume IBM code-page 437 (full ex-ASCII) */
		sockprintf(socket,"Content-Type: text/plain; charset=%s", startup->default_charset);
		sockprintf(socket,"Content-Transfer-Encoding: 8bit");
	}

	if(strListCount(file_list)) {	/* File attachments */
        mimeheaders(socket,mime_boundary);
        sockprintf(socket,"");
        mimeblurb(socket,mime_boundary);
        sockprintf(socket,"");
        mimetextpartheader(socket,mime_boundary);
	}
	if(!sockprintf(socket,""))	/* Header Terminator */
		return(0);

	/* MESSAGE BODY */
	lines=0;
	p=msgtxt;
	while(*p && lines<maxlines) {
		len=0;
		while(len<MAX_LINE_LEN && *(p+len)!=0 && *(p+len)!='\n')
			len++;

		tlen=len;
		while(tlen && *(p+(tlen-1))<=' ') /* Takes care of '\r' or spaces */
			tlen--;

		if(!sockprintf(socket, "%s%.*s", *p=='.' ? ".":"", tlen, p))
			break;
		lines++;
		if(*(p+len)=='\r')
			len++;
		if(*(p+len)=='\n')
			len++;
		p+=len;
		/* release time-slices every x lines */
		if(startup->lines_per_yield
			&& !(lines%startup->lines_per_yield))	
			YIELD();
	}
	if(file_list!=NULL) {
		for(i=0;file_list[i];i++) { 
			sockprintf(socket,"");
			lprintf(LOG_INFO,"%04u MIME Encoding and sending %s",socket,file_list[i]);
			if(!mimeattach(socket,mime_boundary,file_list[i]))
				lprintf(LOG_ERR,"%04u !ERROR opening/encoding/sending %s",socket,file_list[i]);
			else {
				endmime(socket,mime_boundary);
				if(msg->hdr.auxattr&MSG_KILLFILE)
					if(remove(file_list[i])!=0)
						lprintf(LOG_WARNING,"%04u !ERROR %d removing %s",socket,errno,file_list[i]);
			}
		}
	}
    sockprintf(socket,".");	/* End of text */
	return(lines);
}

static ulong sockmsgtxt(SOCKET socket, smbmsg_t* msg, char* msgtxt, ulong maxlines)
{
	char		filepath[MAX_PATH+1];
	ulong		retval;
	char*		boundary=NULL;
	unsigned	i;
	str_list_t	file_list=NULL;
	str_list_t	split;

	if(msg->hdr.auxattr&MSG_FILEATTACH) {

		boundary = mimegetboundary();
		file_list = strListInit();

		/* Parse header fields */
		for(i=0;i<msg->total_hfields;i++)
	        if(msg->hfield[i].type==FILEATTACH) 
				strListPush(&file_list,(char*)msg->hfield_dat[i]);

		/* Parse subject (if necessary) */
		if(!strListCount(file_list)) {	/* filename(s) stored in subject */
			split=strListSplitCopy(NULL,msg->subj," ");
			if(split!=NULL) {
				for(i=0;split[i];i++) {
					if(msg->idx.to!=0)
						SAFEPRINTF3(filepath,"%sfile/%04u.in/%s"
							,scfg.data_dir,msg->idx.to,getfname(truncsp(split[i])));
					else
						SAFEPRINTF3(filepath,"%sfile/%04u.out/%s"
							,scfg.data_dir,msg->idx.from,getfname(truncsp(split[i])));
					strListPush(&file_list,filepath);
				}
				strListFree(&split);
			}
		}
    }

	retval = sockmimetext(socket,msg,msgtxt,maxlines,file_list,boundary);

	strListFree(&file_list);

	if(boundary!=NULL)
		free(boundary);

	return(retval);
}

static u_long resolve_ip(char *inaddr)
{
	char*		p;
	char*		addr;
	char		buf[128];
	HOSTENT*	host;

	SAFECOPY(buf,inaddr);
	addr=buf;
	if(*addr=='[' && *(p=lastchar(addr))==']') { /* Support [ip_address] notation */
		addr++;
		*p=0;
	}

	if(*addr==0)
		return((u_long)INADDR_NONE);

	for(p=addr;*p;p++)
		if(*p!='.' && !isdigit(*p))
			break;
	if(!(*p))
		return(inet_addr(addr));

	if((host=gethostbyname(inaddr))==NULL)
		return((u_long)INADDR_NONE);

	return(*((ulong*)host->h_addr_list[0]));
}


static void pop3_thread(void* arg)
{
	char*		p;
	char		str[128];
	char		buf[512];
	char		host_name[128];
	char		host_ip[64];
	char		username[LEN_ALIAS+1];
	char		password[LEN_PASS+1];
	char		challenge[256];
	char		digest[MD5_DIGEST_SIZE];
	char*		response="";
	char*		msgtxt;
	int			i;
	int			rd;
	BOOL		activity=FALSE;
	BOOL		apop=FALSE;
	long		l;
	ulong		lines;
	ulong		lines_sent;
	int32_t		msgs;
	long		msgnum;
	ulong		bytes;
	SOCKET		socket;
	HOSTENT*	host;
	smb_t		smb;
	smbmsg_t	msg;
	user_t		user;
	client_t	client;
	mail_t*		mail;
	pop3_t		pop3=*(pop3_t*)arg;

	SetThreadName("POP3");
	thread_up(TRUE /* setuid */);

	free(arg);

	socket=pop3.socket;

	if(startup->options&MAIL_OPT_DEBUG_POP3)
		lprintf(LOG_DEBUG,"%04d POP3 session thread started", socket);

#ifdef _WIN32
	if(startup->pop3_sound[0] && !(startup->options&MAIL_OPT_MUTE)) 
		PlaySound(startup->pop3_sound, NULL, SND_ASYNC|SND_FILENAME);
#endif

	SAFECOPY(host_ip,inet_ntoa(pop3.client_addr.sin_addr));

	if(startup->options&MAIL_OPT_DEBUG_POP3)
		lprintf(LOG_INFO,"%04d POP3 connection accepted from: %s port %u"
			,socket, host_ip, ntohs(pop3.client_addr.sin_port));

	if(startup->options&MAIL_OPT_NO_HOST_LOOKUP)
		host=NULL;
	else
		host=gethostbyaddr((char *)&pop3.client_addr.sin_addr
			,sizeof(pop3.client_addr.sin_addr),AF_INET);

	if(host!=NULL && host->h_name!=NULL)
		SAFECOPY(host_name,host->h_name);
	else
		strcpy(host_name,"<no name>");

	if(trashcan(&scfg,host_ip,"ip")) {
		lprintf(LOG_NOTICE,"%04d !POP3 CLIENT IP ADDRESS BLOCKED: %s"
			,socket, host_ip);
		sockprintf(socket,"-ERR Access denied.");
		mail_close_socket(socket);
		thread_down();
		return;
	}

	if(trashcan(&scfg,host_name,"host")) {
		lprintf(LOG_NOTICE,"%04d !POP3 CLIENT HOSTNAME BLOCKED: %s"
			,socket, host_name);
		sockprintf(socket,"-ERR Access denied.");
		mail_close_socket(socket);
		thread_down();
		return;
	}

	active_clients++, update_clients();

	/* Initialize client display */
	client.size=sizeof(client);
	client.time=time(NULL);
	SAFECOPY(client.addr,host_ip);
	SAFECOPY(client.host,host_name);
	client.port=ntohs(pop3.client_addr.sin_port);
	client.protocol="POP3";
	client.user="<unknown>";
	client_on(socket,&client,FALSE /* update */);

	SAFEPRINTF(str,"POP3: %s", host_ip);
	status(str);

	mail=NULL;

	do {
		memset(&smb,0,sizeof(smb));
		memset(&msg,0,sizeof(msg));
		memset(&user,0,sizeof(user));
		password[0]=0;

		srand(time(NULL) ^ (DWORD)GetCurrentThreadId());	/* seed random number generator */
		rand();	/* throw-away first result */
		safe_snprintf(challenge,sizeof(challenge),"<%x%x%lx%lx@%.128s>"
			,rand(),socket,(ulong)time(NULL),clock(),startup->host_name);

		sockprintf(socket,"+OK Synchronet POP3 Server %s-%s Ready %s"
			,revision,PLATFORM_DESC,challenge);

		/* Requires USER command first */
		for(i=3;i;i--) {
			if(!sockgetrsp(socket,NULL,buf,sizeof(buf)))
				break;
			if(!strnicmp(buf,"USER ",5))
				break;
			if(!strnicmp(buf,"APOP ",5)) {
				apop=TRUE;
				break;
			}
			sockprintf(socket,"-ERR USER or APOP command expected");
		}
		if(!i || buf[0]==0)	/* no USER or APOP command received */
			break;

		p=buf+5;
		SKIP_WHITESPACE(p);
		if(apop) {
			if((response=strrchr(p,' '))!=NULL)
				*(response++)=0;
			else
				response=p;
		}
		SAFECOPY(username,p);
		if(!apop) {
			sockprintf(socket,"+OK");
			if(!sockgetrsp(socket,"PASS ",buf,sizeof(buf))) {
				sockprintf(socket,"-ERR PASS command expected");
				break;
			}
			p=buf+5;
			SKIP_WHITESPACE(p);
			SAFECOPY(password,p);
		}
		user.number=matchuser(&scfg,username,FALSE /*sysop_alias*/);
		if(!user.number) {
			if(scfg.sys_misc&SM_ECHO_PW)
				lprintf(LOG_NOTICE,"%04d !POP3 UNKNOWN USER: %s (password: %s)"
					,socket, username, password);
			else
				lprintf(LOG_NOTICE,"%04d !POP3 UNKNOWN USER: %s"
					,socket, username);
			sockprintf(socket,pop_err);
			break;
		}
		if((i=getuserdat(&scfg, &user))!=0) {
			lprintf(LOG_ERR,"%04d !POP3 ERROR %d getting data on user (%s)"
				,socket, i, username);
			sockprintf(socket, pop_err);
			break;
		}
		if(user.misc&(DELETED|INACTIVE)) {
			lprintf(LOG_NOTICE,"%04d !POP3 DELETED or INACTIVE user #%u (%s)"
				,socket, user.number, username);
			sockprintf(socket, pop_err);
			break;
		}
		if(apop) {
			strlwr(user.pass);	/* this is case-sensitive, so convert to lowercase */
			strcat(challenge,user.pass);
			MD5_calc(digest,challenge,strlen(challenge));
			MD5_hex(str,digest);
			if(strcmp(str,response)) {
				lprintf(LOG_NOTICE,"%04d !POP3 %s FAILED APOP authentication"
					,socket,username);
#if 0
				lprintf(LOG_DEBUG,"%04d !POP3 digest data: %s",socket,challenge);
				lprintf(LOG_DEBUG,"%04d !POP3 calc digest: %s",socket,str);
				lprintf(LOG_DEBUG,"%04d !POP3 resp digest: %s",socket,response);
#endif
				sockprintf(socket,pop_err);
				break;
			}
		} else if(stricmp(password,user.pass)) {
			if(scfg.sys_misc&SM_ECHO_PW)
				lprintf(LOG_NOTICE,"%04d !POP3 FAILED Password attempt for user %s: '%s' expected '%s'"
					,socket, username, password, user.pass);
			else
				lprintf(LOG_NOTICE,"%04d !POP3 FAILED Password attempt for user %s"
					,socket, username);
			sockprintf(socket, pop_err);
			break;
		}
		putuserrec(&scfg,user.number,U_COMP,LEN_COMP,host_name);
		putuserrec(&scfg,user.number,U_NOTE,LEN_NOTE,host_ip);

		/* Update client display */
		client.user=user.alias;
		client_on(socket,&client,TRUE /* update */);

		if(startup->options&MAIL_OPT_DEBUG_POP3)		
			lprintf(LOG_INFO,"%04d POP3 %s logged in %s", socket, user.alias, apop ? "via APOP":"");
		SAFEPRINTF(str,"POP3: %s",user.alias);
		status(str);

		SAFEPRINTF(smb.file,"%smail",scfg.data_dir);
		if(smb_islocked(&smb)) {
			lprintf(LOG_WARNING,"%04d !POP3 MAIL BASE LOCKED: %s",socket,smb.last_error);
			sockprintf(socket,"-ERR database locked, try again later");
			break;
		}
		smb.retry_time=scfg.smb_retry_time;
		smb.subnum=INVALID_SUB;
		if((i=smb_open(&smb))!=SMB_SUCCESS) {
			lprintf(LOG_ERR,"%04d !POP3 ERROR %d (%s) opening %s",socket,i,smb.last_error,smb.file);
			sockprintf(socket,"-ERR %d opening %s",i,smb.file);
			break;
		}

		mail=loadmail(&smb,&msgs,user.number,MAIL_YOUR,0);

		for(l=bytes=0;l<msgs;l++) {
			msg.hdr.number=mail[l].number;
			if((i=smb_getmsgidx(&smb,&msg))!=SMB_SUCCESS) {
				lprintf(LOG_ERR,"%04d !POP3 ERROR %d (%s) getting message index"
					,socket, i, smb.last_error);
				break;
			}
			if((i=smb_lockmsghdr(&smb,&msg))!=SMB_SUCCESS) {
				lprintf(LOG_WARNING,"%04d !POP3 ERROR %d (%s) locking message header #%lu"
					,socket, i, smb.last_error, msg.hdr.number);
				break; 
			}
			i=smb_getmsghdr(&smb,&msg);
			smb_unlockmsghdr(&smb,&msg);
			if(i!=0) {
				lprintf(LOG_ERR,"%04d !POP3 ERROR %d (%s) getting message header #%lu"
					,socket, i, smb.last_error, msg.hdr.number);
				break;
			}
			bytes+=smb_getmsgtxtlen(&msg);
			smb_freemsgmem(&msg);
		}

		if(l<msgs) {
			sockprintf(socket,"-ERR message #%d: %d (%s)"
				,mail[l].number,i,smb.last_error);
			break;
		}

		sockprintf(socket,"+OK %lu messages (%lu bytes)",msgs,bytes);

		while(1) {	/* TRANSACTION STATE */
			rd = sockreadline(socket, buf, sizeof(buf));
			if(rd<0) 
				break;
			truncsp(buf);
			if(startup->options&MAIL_OPT_DEBUG_POP3)
				lprintf(LOG_DEBUG,"%04d POP3 RX: %s", socket, buf);
			if(!stricmp(buf, "NOOP")) {
				sockprintf(socket,"+OK");
				continue;
			}
			if(!stricmp(buf, "QUIT")) {
				sockprintf(socket,"+OK");
				break;
			}
			if(!stricmp(buf, "STAT")) {
				sockprintf(socket,"+OK %lu %lu",msgs,bytes);
				continue;
			}
			if(!stricmp(buf, "RSET")) {
				if((i=smb_locksmbhdr(&smb))!=SMB_SUCCESS) {
					lprintf(LOG_ERR,"%04d !POP3 ERROR %d (%s) locking message base"
						,socket, i, smb.last_error);
					sockprintf(socket,"-ERR %d locking message base",i);
					continue;
				}
				for(l=0;l<msgs;l++) {
					msg.hdr.number=mail[l].number;
					if((i=smb_getmsgidx(&smb,&msg))!=SMB_SUCCESS) {
						lprintf(LOG_ERR,"%04d !POP3 ERROR %d (%s) getting message index"
							,socket, i, smb.last_error);
						break;
					}
					if((i=smb_lockmsghdr(&smb,&msg))!=SMB_SUCCESS) {
						lprintf(LOG_WARNING,"%04d !POP3 ERROR %d (%s) locking message header #%lu"
							,socket, i, smb.last_error, msg.hdr.number);
						break; 
					}
					if((i=smb_getmsghdr(&smb,&msg))!=SMB_SUCCESS) {
						smb_unlockmsghdr(&smb,&msg);
						lprintf(LOG_ERR,"%04d !POP3 ERROR %d (%s) getting message header #%lu"
							,socket, i, smb.last_error, msg.hdr.number);
						break;
					}