/* SMTP Server state machine - see RFC 821
 * Very simple implementation; no forwarding allowed
 * (who wants to re-create "sendmail" ??)
 *  enhanced 12/87 Dave Trulli nn2z
 */
#include <stdio.h>
#include <ctype.h>
#include <time.h>
#include "global.h"
#include "mbuf.h"
#include "netuser.h"
#include "timer.h"
#include "tcp.h"
#include "smtp.h"

#ifndef DFLT_MODE
#define DFLT_MODE 0660			/* use this instead of user's umask */
#endif

char *ptime(), *getname();
void mail_delete(), del_rcpt();
static int queuejob(),checkaddress();
int32 get_msgid();

/* Command table */
static char *commands[] = {
	"helo",
#define HELO_CMD	0
	"noop",
#define NOOP_CMD	1
	"mail from:",
#define MAIL_CMD	2
	"quit",
#define QUIT_CMD	3
	"rcpt to:",
#define RCPT_CMD	4
	"help",
#define HELP_CMD	5
	"data",
#define DATA_CMD	6
	"rset",
#define RSET_CMD	7
	NULLCHAR
};

/* Reply messages */
static char help[] = "214-Commands:\r\n214-HELO NOOP MAIL QUIT RCPT HELP DATA RSET\r\n214 End\r\n";
static char banner[] = "220 %s SMTP ready\r\n";
static char closing[] = "221 Closing\r\n";
static char ok[] = "250 Ok\r\n";
static char reset[] = "250 Reset state\r\n";
static char sent[] = "250 Sent\r\n";
static char ourname[] = "250 %s, \"Gateway to the universe!\"\r\n"; /*Share and Enjoy!\r\n";*/
static char enter[] = "354 Enter mail, end with .\r\n";
static char ioerr[] = "452 Temp file write error\r\n";
static char mboxerr[] = "452 Mailbox %s write error\r\n";
static char badcmd[] = "500 Command unrecognized\r\n";
static char syntax[] = "501 Syntax error\r\n";
static char needrcpt[] = "503 Need RCPT (recipient)\r\n";
static char badname[] = "550 Can't open mailbox for %s\r\n";

static struct tcb *smtp_tcb;
/* Start up SMTP receiver service */
smtp_start(argc,argv)
int argc;
char *argv[];
{
	struct socket lsocket;
	void r_mail(),s_mail();

	lsocket.address = ip_addr;
	if(argc < 2)
		lsocket.port = SMTP_PORT;
	else
		lsocket.port = atoi(argv[1]);

	smtp_tcb = open_tcp(&lsocket,NULLSOCK,
		TCP_SERVER,0,r_mail,NULLVFP,s_mail,0,(char *)NULL);
}

/* Shutdown SMTP service (existing connections are allowed to finish) */
smtp_stop()
{
	if(smtp_tcb != NULLTCB)
		close_tcp(smtp_tcb);
}

/* SMTP connection state change upcall handler */
static void
s_mail(tcb,old,new)
struct tcb *tcb;
char old,new;
{
	struct mail *mp,*mail_create();

	switch(new){
#ifdef	QUICKSTART
	case SYN_RECEIVED:
#else
	case ESTABLISHED:
#endif
		if((mp = mail_create(tcb)) == NULLMAIL){
			close_tcp(tcb);
			break;
		}
		(void) tprintf(mp->tcb,banner,hostname);
		log(tcb,"open SMTP");
		break;		
	case CLOSE_WAIT:
		close_tcp(tcb);
		break;
	case CLOSED:
		log(tcb,"close SMTP");
		mp = (struct mail *)tcb->user;
		mail_delete(mp);				
		del_tcp(tcb);
		/* Check if server is being shut down */
		if(tcb == smtp_tcb)
			smtp_tcb = NULLTCB;
		break;
	}
}

/* SMTP receiver upcall handler */
static void
r_mail(tcb,cnt)
struct tcb *tcb;
int16 cnt;
{
	register struct mail *mp;
	char *inet_ntoa(),c;
	struct mbuf *bp;
	void docommand(),deliver(),doline();

	if((mp = (struct mail *)tcb->user) == NULLMAIL){
		/* Unknown session */
		close_tcp(tcb);
		return;
	}
	recv_tcp(tcb,&bp,cnt);
	/* Assemble an input line in the session buffer.
	 * Return if incomplete
	 */
	while(pullup(&bp,&c,1) == 1){
		switch(c){
		case '\r':	/* Strip cr's */
#ifdef MSDOS
		case '\032':	/* Strip ctrl/Z's */
#endif
			continue;
		case '\n':	/* Complete line; process it */
			mp->buf[mp->cnt] = '\0';
			doline(mp);
			break;
		default:	/* Assemble line */
			if(mp->cnt != LINELEN-1)
				mp->buf[mp->cnt++] = c;
			break;
		}
	}
}
/* Process a line read on an SMTP connection (any state) */
static void
doline(mp)
register struct mail *mp;
{
	void docommand(),deliver();

	switch(mp->state){
	case COMMAND_STATE:
		docommand(mp);
		break;
	case DATA_STATE:
		tcp_output(mp->tcb);	/* Send ACK; disk I/O is slow */
		if(mp->buf[0] == '.' && mp->buf[1] == '\0'){
			mp->state = COMMAND_STATE;
			deliver(mp);	/* Also sends appropriate response */
			break;
		}
		/* Append to data file */
		if(fprintf(mp->data,"%s\n",mp->buf) < 0){
			mp->state = COMMAND_STATE;
			(void) tprintf(mp->tcb,ioerr);
		}
		break;
	}
	mp->cnt = 0;
}
/* Create control block, initialize */
static struct mail *
mail_create(tcb)
register struct tcb *tcb;
{
	register struct mail *mp;

	if((mp = (struct mail *)calloc(1,sizeof (struct mail))) == NULLMAIL)
		return NULLMAIL;
	mp->tcb = tcb;		/* Downward pointer */
	tcb->user = (char *)mp; /* Upward pointer */
	return mp;
}

/* Free resources, delete control block */
static void
mail_delete(mp)
register struct mail *mp;
{

	if (mp == NULLMAIL)
		return;
	if(mp->system != NULLCHAR)
		free(mp->system);
	if(mp->from != NULLCHAR)
		free(mp->from);
	if(mp->data != NULLFILE)
		fclose(mp->data);
	del_rcpt(mp->to);
	free((char *)mp);
}

static void
del_rcpt(p)
struct addr *p;
{
	register struct addr *ap,*ap1;
	for(ap = p;ap != NULLADDR;ap = ap1){
		if(ap->val != NULLCHAR)
			free(ap->val);
		ap1 = ap->next;
		free((char *)ap);
	}
}

/* Parse and execute mail commands */
static void
docommand(mp)
register struct mail *mp;
{
	char *cmd,*arg,*cp,**cmdp;
	struct addr *ap;
	FILE *tmpfile();
	long t;

	cmd = mp->buf;
	if(mp->cnt < 4){
		/* Can't be a legal SMTP command */
		(void) tprintf(mp->tcb,badcmd);
		return;
	}	
	cmd = mp->buf;

	/* Translate entire buffer to lower case */
	for(cp = cmd;*cp != '\0';cp++)
		*cp = tolower(*cp);

	/* Find command in table; if not present, return syntax error */
	for(cmdp = commands;*cmdp != NULLCHAR;cmdp++)
		if(strncmp(*cmdp,cmd,strlen(*cmdp)) == 0)
			break;
	if(*cmdp == NULLCHAR){
		(void) tprintf(mp->tcb,badcmd);
		return;
	}
	arg = &cmd[strlen(*cmdp)];
	/* Skip spaces after command */
	while(*arg == ' ')
		arg++;
	/* Execute specific command */
	switch(cmdp-commands){
	case HELO_CMD:
		if(mp->system != NULLCHAR)
			free(mp->system);
		if((mp->system = malloc((unsigned)strlen(arg)+1)) == NULLCHAR){
			/* If the system is out of memory, just close */
			close_tcp(mp->tcb);
			break;			
		} else {
			strcpy(mp->system,arg);
			(void) tprintf(mp->tcb,ourname,hostname);
		}
		break;
	case NOOP_CMD:
		(void) tprintf(mp->tcb,ok);
		break;
	case MAIL_CMD:
		if(mp->from != NULLCHAR)
			free(mp->from);
		if((mp->from = malloc((unsigned)strlen(arg)+1)) == NULLCHAR){
			/* If the system is out of memory, just close */
			close_tcp(mp->tcb);
			break;			
		} else {
			if((cp = getname(arg)) == NULLCHAR){
				(void) tprintf(mp->tcb,syntax);
				break;
			}
			strcpy(mp->from,cp);
			(void) tprintf(mp->tcb,ok);
		}
		break;
	case QUIT_CMD:
		(void) tprintf(mp->tcb,closing);
		close_tcp(mp->tcb);
		break;
	case RCPT_CMD:	/* Specify recipient */
		if((cp = getname(arg)) == NULLCHAR){
			(void) tprintf(mp->tcb,syntax);
			break;
		}
		if (checkaddress(cp)) {
			(void) tprintf(mp->tcb,badname,cp);
			break;
		}
		/* Allocate an entry on the recipient list. This
		 * assembles the list backwards, but what the heck.
		 */
		if((ap = (struct addr *)malloc(sizeof(struct addr))) == NULLADDR){
			close_tcp(mp->tcb);
			break;
		}
		if((ap->val = malloc((unsigned)strlen(cp)+1)) == NULLCHAR){
			free((char *)ap);
			close_tcp(mp->tcb);
			break;
		}
		strcpy(ap->val,cp);
		ap->next = mp->to;
		mp->to = ap;
		(void) tprintf(mp->tcb,ok);
		break;
	case HELP_CMD:
		(void) tprintf(mp->tcb,help);
		break;
	case DATA_CMD:
		if(mp->to == NULLADDR){
			(void) tprintf(mp->tcb,needrcpt);
			break;
		}
		tcp_output(mp->tcb);	/* Send ACK; disk I/O is slow */
		if((mp->data = tmpfile()) == NULLFILE){
			(void) tprintf(mp->tcb,ioerr);
			break;
		}
		/* Add timestamp; ptime adds newline */
		mp->seqn = get_msgid();
		time(&t);
		fprintf(mp->data,"Received: ");
		if(mp->system != NULLCHAR)
			fprintf(mp->data,"from %s ",mp->system);
		fprintf(mp->data,"by %s with SMTP (871225.4/ST)\n\tid %ld; %s",
				hostname,
				mp->seqn,
				ptime(&t));
		if(ferror(mp->data)){
			(void) tprintf(mp->tcb,ioerr);
		} else {
			mp->state = DATA_STATE;
			(void) tprintf(mp->tcb,enter);
		}
		break;
	case RSET_CMD:
		del_rcpt(mp->to);
		mp->to = NULLADDR;
		mp->state = COMMAND_STATE;
		(void) tprintf(mp->tcb,reset);
		break;
	}
}
/* Given a string of the form <user@host>, extract the part inside the
 * brackets and return a pointer to it.
 */
static
char *
getname(cp)
register char *cp;
{
	register char *cp1;

	if((cp = index(cp,'<')) == NULLCHAR){
		return NULLCHAR;
	}
	cp++;	/* cp -> first char of name */
	if((cp1 = index(cp,'>')) == NULLCHAR){
		return NULLCHAR;
	}
	*cp1 = '\0';
	return cp;
}
/* Deliver mail to the appropriate mail boxes and delete temp file */
static
void
deliver(mp)
register struct mail *mp;
{
	int c;
	register struct addr *ap;
	register FILE *fp;
	char	mailbox[50];
	char	*cp;
	int	fail = 0;

	for(ap = mp->to;ap != NULLADDR;ap = ap->next) {

		/*
		 * For now just look at the user name of the address
		 * more in next release. nn2z
		 */
		if ((cp = index(ap->val,'@')) != NULLCHAR)
			*cp = '\0';

		cp = ap->val;
		while( *cp && isalnum(*cp))
			cp++;
		*cp = '\0';
		
		fseek(mp->data,0L,0);	/* rewind */

		/* if mail file is busy save it in out smtp queue
		 * and let the smtp daemon try later.
		 */
		if (mlock(mailspool,ap->val))
			fail = queuejob(mp->data,hostname,ap->val,mp->from,mp->seqn);
		else {
			sprintf(mailbox,"%s%s.txt",mailspool,ap->val);
			if((fp = fopen(mailbox,"a+")) != NULLFILE) {
				while((c = getc(mp->data)) != EOF)
					if(putc(c,fp) == EOF)
						break;
				if(ferror(fp))
					fail = 1;
				/* Leave a blank line between msgs */
				fprintf(mp->data,"\n");
				fclose(fp);
#ifdef UNIX
				chmod(mailbox, DFLT_MODE);
#endif
			} else 
				fail = 1;
			(void) rmlock(mailspool,ap->val);
			if (fail)
				break;
		}
	}
	if (fail)
		(void) tprintf(mp->tcb,mboxerr,ap->val);
	else
		(void) tprintf(mp->tcb,sent);
	fclose(mp->data);
	mp->data = NULLFILE;
	del_rcpt(mp->to);
	mp->to = NULLADDR;
}

/* Return Date/Time in Arpanet format in passed string */
char *
ptime(t)
long *t;
{
	register struct tm *ltm;
	struct tm *gmtime();
	static char timezone[4];
	static char str[40];
	extern char *getenv();
	/* Print out the time and date field as
	 *		"DAY day MONTH year hh:mm:ss ZONE"
	 */
	char *p;
	static char *days[7] = {
		"Sun","Mon","Tue","Wed","Thu","Fri","Sat" };

	static char *months[12] = {
		"Jan","Feb","Mar","Apr","May","Jun",
		"Jul","Aug","Sep","Oct","Nov","Dec" };

	/* Read the system time */
	ltm = gmtime(t);

	if (*timezone == '\0')
		if ((p = getenv("TZ")) == NULL)
			strcpy(timezone,"GMT");
		else
			strncpy(timezone,p,3);

	/* rfc 822 format */
	sprintf(str,"%s, %.2d %s %02d %02d:%02d:%02d %.3s\n",
		days[ltm->tm_wday],
		ltm->tm_mday,
		months[ltm->tm_mon],
		ltm->tm_year,
		ltm->tm_hour,
		ltm->tm_min,
		ltm->tm_sec,
		timezone);
	return(str);
}

int32 
get_msgid()
{
	char sfilename[LINELEN];
	char s[20];
	long sequence = 0;
	FILE *sfile;
	long atol();

	strcpy(sfilename,mailqdir);
	strcat(sfilename,"sequence.seq");
	sfile = fopen(sfilename,"r");

	/* if sequence file exists, get the value, otherwise set it */
	if (sfile != NULL) {
		(void) fgets(s,sizeof(s),sfile);
		sequence = atol(s);
	/* Keep it in range of and 8 digit number to use for dos name prefix. */
		if (sequence < 0L || sequence > 99999999L )
			sequence = 0;
		fclose(sfile);
	}

	/* increment sequence number, and write to sequence file */
	sfile = fopen(sfilename,"w");
	fprintf(sfile,"%ld",++sequence);
	fclose(sfile);
#ifdef UNIX
	chmod(sfile, DFLT_MODE);
#endif
	return sequence;
}

/* test if mail address is valid - to be improved in next release */
static int
checkaddress(s)
char *s;
{
	FILE *fp;
	char mailbox[50];
	char *cp;

	strcpy(mailbox,mailspool);
	cp = mailbox;
	while (*cp)	/* find end of string */
		cp++;

	while ( *s && isalnum(*s))	/*GRI MOD append the user name */
		*cp++ = *s++;

	*cp = '\0';
	strcat(mailbox,".txt"); 	/* and file type */
	/* Check to see if we can open the mailbox */
	if ((fp = fopen(mailbox,"a+")) == NULLFILE)
		return 1;
	fclose(fp);
	return 0;
}

/* place a mail job in the outbound queue */
static int
queuejob(dfile,host,to,from,id)
FILE *dfile;
char *host,*to,*from;
int32 id;
{
	FILE *fp;
	char tmpstring[50];
	char prefix[9];
	int c;

	sprintf(prefix,"%.8d",id);
	mlock(mailqdir,prefix);
	sprintf(tmpstring,"%s%s.txt",mailqdir,prefix);
	if((fp = fopen(tmpstring,"w")) == NULLFILE) {
		(void) rmlock(mailqdir,prefix);
		return 1;
	}
	while((c = getc(dfile)) != EOF)
		if(putc(c,fp) == EOF)
			break;
	if(ferror(fp)){
		fclose(fp);
		(void) rmlock(mailqdir,prefix);
		return 1;
	}
	fclose(fp);
	sprintf(tmpstring,"%s%s.wrk",mailqdir,prefix);
	if((fp = fopen(tmpstring,"w")) == NULLFILE) {
		(void) rmlock(mailqdir,prefix);
		return 1;
	}
	fprintf(fp,"%s\n%s\n%s\n",host,from,to);
	fclose(fp);
	(void) rmlock(mailqdir,prefix);
	return 0;
}