src/cmd/upas/smtp/spam.c - plan9 - Git at Google

 #include "common.h"
 #include "smtpd.h"
 #include <ip.h>

 enum {
 	NORELAY = 0,
 	DNSVERIFY,
 	SAVEBLOCK,
 	DOMNAME,
 	OURNETS,
 	OURDOMS,

 	IP = 0,
 	STRING
 };


 typedef struct Keyword Keyword;

 struct Keyword {
 	char	*name;
 	int	code;
 };

 static Keyword options[] = {
 	"norelay",		NORELAY,
 	"verifysenderdom",	DNSVERIFY,
 	"saveblockedmsg",	SAVEBLOCK,
 	"defaultdomain",	DOMNAME,
 	"ournets",		OURNETS,
 	"ourdomains",		OURDOMS,
 	0,			NONE
 };

 static Keyword actions[] = {
 	"allow",		ACCEPT,
 	"block",		BLOCKED,
 	"deny",			DENIED,
 	"dial",			DIALUP,
 	"delay",		DELAY,
 	0,			NONE
 };

 static	int	hisaction;
 static	List	ourdoms;
 static	List 	badguys;
 static	ulong	v4peerip;

 static	char*	getline(Biobuf*);
 static	int	cidrcheck(char*);

 static int
 findkey(char *val, Keyword *p)
 {

 	for(; p->name; p++)
 		if(strcmp(val, p->name) == 0)
 				break;
 	return p->code;
 }

 char*
 actstr(int a)
 {
 	static char buf[32];
 	Keyword *p;

 	for(p=actions; p->name; p++)
 		if(p->code == a)
 			return p->name;
 	if(a==NONE)
 		return "none";
 	sprint(buf, "%d", a);
 	return buf;
 }

 int
 getaction(char *s, char *type)
 {
 	char buf[1024];
 	Keyword *k;

 	if(s == nil || *s == 0)
 		return ACCEPT;

 	for(k = actions; k->name != 0; k++){
 		snprint(buf, sizeof buf, "%s/mail/ratify/%s/%s/%s",
 			get9root(), k->name, type, s);
 		if(access(buf,0) >= 0)
 			return k->code;
 	}
 	return ACCEPT;
 }

 int
 istrusted(char *s)
 {
 	char buf[1024];

 	if(s == nil || *s == 0)
 		return 0;

 	snprint(buf, sizeof buf, "%s/mail/ratify/trusted/%s", get9root(), s);
 	return access(buf,0) >= 0;
 }

 void
 getconf(void)
 {
 	Biobuf *bp;
 	char *cp, *p;
 	String *s;
 	char buf[512];
 	uchar addr[4];

 	v4parseip(addr, nci->rsys);
 	v4peerip = nhgetl(addr);

 	trusted = istrusted(nci->rsys);
 	hisaction = getaction(nci->rsys, "ip");
 	if(debug){
 		fprint(2, "istrusted(%s)=%d\n", nci->rsys, trusted);
 		fprint(2, "getaction(%s, ip)=%s\n", nci->rsys, actstr(hisaction));
 	}
 	snprint(buf, sizeof(buf), "%s/smtpd.conf", UPASLIB);
 	bp = sysopen(buf, "r", 0);
 	if(bp == 0)
 		return;

 	for(;;){
 		cp = getline(bp);
 		if(cp == 0)
 			break;
 		p = cp+strlen(cp)+1;
 		switch(findkey(cp, options)){
 		case NORELAY:
 			if(fflag == 0 && strcmp(p, "on") == 0)
 				fflag++;
 			break;
 		case DNSVERIFY:
 			if(rflag == 0 && strcmp(p, "on") == 0)
 				rflag++;
 			break;
 		case SAVEBLOCK:
 			if(sflag == 0 && strcmp(p, "on") == 0)
 				sflag++;
 			break;
 		case DOMNAME:
 			if(dom == 0)
 				dom = strdup(p);
 			break;
 		case OURNETS:
 			if (trusted == 0)
 				trusted = cidrcheck(p);
 			break;
 		case OURDOMS:
 			while(*p){
 				s = s_new();
 				s_append(s, p);
 				listadd(&ourdoms, s);
 				p += strlen(p)+1;
 			}
 			break;
 		default:
 			break;
 		}
 	}
 	sysclose(bp);
 }

 #if 0
 /*
  *	match a user name.  the only meta-char is '*' which matches all
  *	characters.  we only allow it as "*", which matches anything or
  *	an * at the end of the name (e.g., "username*") which matches
  *	trailing characters.
  */
 static int
 usermatch(char *pathuser, char *specuser)
 {
 	int n;

 	n = strlen(specuser)-1;
 	if(specuser[n] == '*'){
 		if(n == 0)		/* match everything */
 			return 0;
 		return strncmp(pathuser, specuser, n);
 	}
 	return strcmp(pathuser, specuser);
 }
 #endif

 static int
 dommatch(char *pathdom, char *specdom)
 {
 	int n;

 	if (*specdom == '*'){
 		if (specdom[1] == '.' && specdom[2]){
 			specdom += 2;
 			n = strlen(pathdom)-strlen(specdom);
 			if(n == 0 || (n > 0 && pathdom[n-1] == '.'))
 				return strcmp(pathdom+n, specdom);
 			return n;
 		}
 	}
 	return strcmp(pathdom, specdom);
 }

 /*
  *  figure out action for this sender
  */
 int
 blocked(String *path)
 {
 	String *lpath;
 	int action;

 	if(debug)
 		fprint(2, "blocked(%s)\n", s_to_c(path));

 	/* if the sender's IP address is blessed, ignore sender email address */
 	if(trusted){
 		if(debug)
 			fprint(2, "\ttrusted => trusted\n");
 		return TRUSTED;
 	}

 	/* if sender's IP address is blocked, ignore sender email address */
 	if(hisaction != ACCEPT){
 		if(debug)
 			fprint(2, "\thisaction=%s => %s\n", actstr(hisaction), actstr(hisaction));
 		return hisaction;
 	}

 	/* convert to lower case */
 	lpath = s_copy(s_to_c(path));
 	s_tolower(lpath);

 	/* classify */
 	action = getaction(s_to_c(lpath), "account");
 	if(debug)
 		fprint(2, "\tgetaction account %s => %s\n", s_to_c(lpath), actstr(action));
 	s_free(lpath);
 	return action;
 }

 /*
  * get a canonicalized line: a string of null-terminated lower-case
  * tokens with a two null bytes at the end.
  */
 static char*
 getline(Biobuf *bp)
 {
 	char c, *cp, *p, *q;
 	int n;

 	static char *buf;
 	static int bufsize;

 	for(;;){
 		cp = Brdline(bp, '\n');
 		if(cp == 0)
 			return 0;
 		n = Blinelen(bp);
 		cp[n-1] = 0;
 		if(buf == 0 || bufsize < n+1){
 			bufsize += 512;
 			if(bufsize < n+1)
 				bufsize = n+1;
 			buf = realloc(buf, bufsize);
 			if(buf == 0)
 				break;
 		}
 		q = buf;
 		for (p = cp; *p; p++){
 			c = *p;
 			if(c == '\\' && p[1])	/* we don't allow \<newline> */
 				c = *++p;
 			else
 			if(c == '#')
 				break;
 			else
 			if(c == ' ' || c == '\t' || c == ',')
 				if(q == buf || q[-1] == 0)
 					continue;
 				else
 					c = 0;
 			*q++ = tolower(c);
 		}
 		if(q != buf){
 			if(q[-1])
 				*q++ = 0;
 			*q = 0;
 			break;
 		}
 	}
 	return buf;
 }

 static int
 isourdom(char *s)
 {
 	Link *l;

 	if(strchr(s, '.') == nil)
 		return 1;

 	for(l = ourdoms.first; l; l = l->next){
 		if(dommatch(s, s_to_c(l->p)) == 0)
 			return 1;
 	}
 	return 0;
 }

 int
 forwarding(String *path)
 {
 	char *cp, *s;
 	String *lpath;

 	if(debug)
 		fprint(2, "forwarding(%s)\n", s_to_c(path));

 	/* first check if they want loopback */
 	lpath = s_copy(s_to_c(s_restart(path)));
 	if(nci->rsys && *nci->rsys){
 		cp = s_to_c(lpath);
 		if(strncmp(cp, "[]!", 3) == 0){
 found:
 			s_append(path, "[");
 			s_append(path, nci->rsys);
 			s_append(path, "]!");
 			s_append(path, cp+3);
 			s_terminate(path);
 			s_free(lpath);
 			return 0;
 		}
 		cp = strchr(cp,'!');			/* skip our domain and check next */
 		if(cp++ && strncmp(cp, "[]!", 3) == 0)
 			goto found;
 	}

 	/* if mail is from a trusted IP addr, allow it to forward */
 	if(trusted) {
 		s_free(lpath);
 		return 0;
 	}

 	/* sender is untrusted; ensure receiver is in one of our domains */
 	for(cp = s_to_c(lpath); *cp; cp++)		/* convert receiver lc */
 		*cp = tolower(*cp);

 	for(s = s_to_c(lpath); cp = strchr(s, '!'); s = cp+1){
 		*cp = 0;
 		if(!isourdom(s)){
 			s_free(lpath);
 			return 1;
 		}
 	}
 	s_free(lpath);
 	return 0;
 }

 int
 masquerade(String *path, char *him)
 {
 	char *cp, *s;
 	String *lpath;
 	int rv = 0;

 	if(debug)
 		fprint(2, "masquerade(%s)\n", s_to_c(path));

 	if(trusted)
 		return 0;
 	if(path == nil)
 		return 0;

 	lpath = s_copy(s_to_c(path));

 	/* sender is untrusted; ensure receiver is in one of our domains */
 	for(cp = s_to_c(lpath); *cp; cp++)		/* convert receiver lc */
 		*cp = tolower(*cp);
 	s = s_to_c(lpath);

 	/* scan first element of ! or last element of @ paths */
 	if((cp = strchr(s, '!')) != nil){
 		*cp = 0;
 		if(isourdom(s))
 			rv = 1;
 	} else if((cp = strrchr(s, '@')) != nil){
 		if(isourdom(cp+1))
 			rv = 1;
 	} else {
 		if(isourdom(him))
 			rv = 1;
 	}

 	s_free(lpath);
 	return rv;
 }

 /* this is a v4 only check */
 static int
 cidrcheck(char *cp)
 {
 	char *p;
 	ulong a, m;
 	uchar addr[IPv4addrlen];
 	uchar mask[IPv4addrlen];

 	if(v4peerip == 0)
 		return 0;

 	/* parse a list of CIDR addresses comparing each to the peer IP addr */
 	while(cp && *cp){
 		v4parsecidr(addr, mask, cp);
 		a = nhgetl(addr);
 		m = nhgetl(mask);
 		/*
 		 * if a mask isn't specified, we build a minimal mask
 		 * instead of using the default mask for that net.  in this
 		 * case we never allow a class A mask (0xff000000).
 		 */
 		if(strchr(cp, '/') == 0){
 			m = 0xff000000;
 			p = cp;
 			for(p = strchr(p, '.'); p && p[1]; p = strchr(p+1, '.'))
 					m = (m>>8)|0xff000000;

 			/* force at least a class B */
 			m |= 0xffff0000;
 		}
 		if((v4peerip&m) == a)
 			return 1;
 		cp += strlen(cp)+1;
 	}
 	return 0;
 }

 int
 isbadguy(void)
 {
 	Link *l;

 	/* check if this IP address is banned */
 	for(l = badguys.first; l; l = l->next)
 		if(cidrcheck(s_to_c(l->p)))
 			return 1;

 	return 0;
 }

 void
 addbadguy(char *p)
 {
 	listadd(&badguys, s_copy(p));
 };

 char*
 dumpfile(char *sender)
 {
 	int i, fd;
 	ulong h;
 	static char buf[512];
 	char *cp;

 	if (sflag == 1){
 		cp = ctime(time(0));
 		cp[7] = 0;
 		if(cp[8] == ' ')
 			sprint(buf, "%s/queue.dump/%s%c", SPOOL, cp+4, cp[9]);
 		else
 			sprint(buf, "%s/queue.dump/%s%c%c", SPOOL, cp+4, cp[8], cp[9]);
 		cp = buf+strlen(buf);
 		if(access(buf, 0) < 0 && sysmkdir(buf, 0777) < 0)
 			return "/dev/null";
 		h = 0;
 		while(*sender)
 			h = h*257 + *sender++;
 		for(i = 0; i < 50; i++){
 			h += lrand();
 			sprint(cp, "/%lud", h);
 			if(access(buf, 0) >= 0)
 				continue;
 			fd = syscreate(buf, ORDWR, 0666);
 			if(fd >= 0){
 				if(debug)
 					fprint(2, "saving in %s\n", buf);
 				close(fd);
 				return buf;
 			}
 		}
 	}
 	return "/dev/null";
 }

 char *validator = "#9/mail/lib/validateaddress";

 int
 recipok(char *user)
 {
 	char *cp, *p, c;
 	char buf[512];
 	int n;
 	Biobuf *bp;
 	int pid;
 	Waitmsg *w;
 	static int beenhere;

 	if(!beenhere){
 		beenhere++;
 		validator = unsharp(validator);
 	}
 	if(shellchars(user)){
 		syslog(0, "smtpd", "shellchars in user name");
 		return 0;
 	}

 	if(access(validator, AEXEC) == 0)
 	switch(pid = fork()) {
 	case -1:
 		break;
 	case 0:
 		execl(validator, "validateaddress", user, nil);
 		exits(0);
 	default:
 		while(w = wait()) {
 			if(w->pid != pid)
 				continue;
 			if(w->msg[0] != 0){
 				syslog(0, "smtpd", "validateaddress %s: %s", user, w->msg);
 				return 0;
 			}
 			break;
 		}
 	}

 	snprint(buf, sizeof(buf), "%s/names.blocked", UPASLIB);
 	bp = sysopen(buf, "r", 0);
 	if(bp == 0)
 		return 1;
 	for(;;){
 		cp = Brdline(bp, '\n');
 		if(cp == 0)
 			break;
 		n = Blinelen(bp);
 		cp[n-1] = 0;

 		while(*cp == ' ' || *cp == '\t')
 			cp++;
 		for(p = cp; c = *p; p++){
 			if(c == '#')
 				break;
 			if(c == ' ' || c == '\t')
 				break;
 		}
 		if(p > cp){
 			*p = 0;
 			if(cistrcmp(user, cp) == 0){
 				syslog(0, "smtpd", "names.blocked blocks %s", user);
 				Bterm(bp);
 				return 0;
 			}
 		}
 	}
 	Bterm(bp);
 	return 1;
 }

 /*
  *  a user can opt out of spam filtering by creating
  *  a file in his mail directory named 'nospamfiltering'.
  */
 int
 optoutofspamfilter(char *addr)
 {
 	char *p, *f;
 	int rv;

 	p = strchr(addr, '!');
 	if(p)
 		p++;
 	else
 		p = addr;


 	rv = 0;
 	f = smprint("%s/mail/box/%s/nospamfiltering", get9root(), p);
 	if(f != nil){
 		rv = access(f, 0)==0;
 		free(f);
 	}

 	return rv;
 }
	#include "common.h"
	#include "smtpd.h"
	#include <ip.h>

	enum {
	NORELAY = 0,
	DNSVERIFY,
	SAVEBLOCK,
	DOMNAME,
	OURNETS,
	OURDOMS,

	IP = 0,
	STRING
	};


	typedef struct Keyword Keyword;

	struct Keyword {
	char *name;
	int code;
	};

	static Keyword options[] = {
	"norelay", NORELAY,
	"verifysenderdom", DNSVERIFY,
	"saveblockedmsg", SAVEBLOCK,
	"defaultdomain", DOMNAME,
	"ournets", OURNETS,
	"ourdomains", OURDOMS,
	0, NONE
	};

	static Keyword actions[] = {
	"allow", ACCEPT,
	"block", BLOCKED,
	"deny", DENIED,
	"dial", DIALUP,
	"delay", DELAY,
	0, NONE
	};

	static int hisaction;
	static List ourdoms;
	static List badguys;
	static ulong v4peerip;

	static char* getline(Biobuf*);
	static int cidrcheck(char*);

	static int
	findkey(char val, Keyword p)
	{

	for(; p->name; p++)
	if(strcmp(val, p->name) == 0)
	break;
	return p->code;
	}

	char*
	actstr(int a)
	{
	static char buf[32];
	Keyword *p;

	for(p=actions; p->name; p++)
	if(p->code == a)
	return p->name;
	if(a==NONE)
	return "none";
	sprint(buf, "%d", a);
	return buf;
	}

	int
	getaction(char s, char type)
	{
	char buf[1024];
	Keyword *k;

	if(s == nil \|\| *s == 0)
	return ACCEPT;

	for(k = actions; k->name != 0; k++){
	snprint(buf, sizeof buf, "%s/mail/ratify/%s/%s/%s",
	get9root(), k->name, type, s);
	if(access(buf,0) >= 0)
	return k->code;
	}
	return ACCEPT;
	}

	int
	istrusted(char *s)
	{
	char buf[1024];

	if(s == nil \|\| *s == 0)
	return 0;

	snprint(buf, sizeof buf, "%s/mail/ratify/trusted/%s", get9root(), s);
	return access(buf,0) >= 0;
	}

	void
	getconf(void)
	{
	Biobuf *bp;
	char cp, p;
	String *s;
	char buf[512];
	uchar addr[4];

	v4parseip(addr, nci->rsys);
	v4peerip = nhgetl(addr);

	trusted = istrusted(nci->rsys);
	hisaction = getaction(nci->rsys, "ip");
	if(debug){
	fprint(2, "istrusted(%s)=%d\n", nci->rsys, trusted);
	fprint(2, "getaction(%s, ip)=%s\n", nci->rsys, actstr(hisaction));
	}
	snprint(buf, sizeof(buf), "%s/smtpd.conf", UPASLIB);
	bp = sysopen(buf, "r", 0);
	if(bp == 0)
	return;

	for(;;){
	cp = getline(bp);
	if(cp == 0)
	break;
	p = cp+strlen(cp)+1;
	switch(findkey(cp, options)){
	case NORELAY:
	if(fflag == 0 && strcmp(p, "on") == 0)
	fflag++;
	break;
	case DNSVERIFY:
	if(rflag == 0 && strcmp(p, "on") == 0)
	rflag++;
	break;
	case SAVEBLOCK:
	if(sflag == 0 && strcmp(p, "on") == 0)
	sflag++;
	break;
	case DOMNAME:
	if(dom == 0)
	dom = strdup(p);
	break;
	case OURNETS:
	if (trusted == 0)
	trusted = cidrcheck(p);
	break;
	case OURDOMS:
	while(*p){
	s = s_new();
	s_append(s, p);
	listadd(&ourdoms, s);
	p += strlen(p)+1;
	}
	break;
	default:
	break;
	}
	}
	sysclose(bp);
	}

	#if 0
	/*
	* match a user name. the only meta-char is '*' which matches all
	* characters. we only allow it as "*", which matches anything or
	* an * at the end of the name (e.g., "username*") which matches
	* trailing characters.
	*/
	static int
	usermatch(char pathuser, char specuser)
	{
	int n;

	n = strlen(specuser)-1;
	if(specuser[n] == '*'){
	if(n == 0) /* match everything */
	return 0;
	return strncmp(pathuser, specuser, n);
	}
	return strcmp(pathuser, specuser);
	}
	#endif

	static int
	dommatch(char pathdom, char specdom)
	{
	int n;

	if (specdom == ''){
	if (specdom[1] == '.' && specdom[2]){
	specdom += 2;
	n = strlen(pathdom)-strlen(specdom);
	if(n == 0 \|\| (n > 0 && pathdom[n-1] == '.'))
	return strcmp(pathdom+n, specdom);
	return n;
	}
	}
	return strcmp(pathdom, specdom);
	}

	/*
	* figure out action for this sender
	*/
	int
	blocked(String *path)
	{
	String *lpath;
	int action;

	if(debug)
	fprint(2, "blocked(%s)\n", s_to_c(path));

	/* if the sender's IP address is blessed, ignore sender email address */
	if(trusted){
	if(debug)
	fprint(2, "\ttrusted => trusted\n");
	return TRUSTED;
	}

	/* if sender's IP address is blocked, ignore sender email address */
	if(hisaction != ACCEPT){
	if(debug)
	fprint(2, "\thisaction=%s => %s\n", actstr(hisaction), actstr(hisaction));
	return hisaction;
	}

	/* convert to lower case */
	lpath = s_copy(s_to_c(path));
	s_tolower(lpath);

	/* classify */
	action = getaction(s_to_c(lpath), "account");
	if(debug)
	fprint(2, "\tgetaction account %s => %s\n", s_to_c(lpath), actstr(action));
	s_free(lpath);
	return action;
	}

	/*
	* get a canonicalized line: a string of null-terminated lower-case
	* tokens with a two null bytes at the end.
	*/
	static char*
	getline(Biobuf *bp)
	{
	char c, cp, p, *q;
	int n;

	static char *buf;
	static int bufsize;

	for(;;){
	cp = Brdline(bp, '\n');
	if(cp == 0)
	return 0;
	n = Blinelen(bp);
	cp[n-1] = 0;
	if(buf == 0 \|\| bufsize < n+1){
	bufsize += 512;
	if(bufsize < n+1)
	bufsize = n+1;
	buf = realloc(buf, bufsize);
	if(buf == 0)
	break;
	}
	q = buf;
	for (p = cp; *p; p++){
	c = *p;
	if(c == '\\' && p[1]) /* we don't allow \<newline> */
	c = *++p;
	else
	if(c == '#')
	break;
	else
	if(c == ' ' \|\| c == '\t' \|\| c == ',')
	if(q == buf \|\| q[-1] == 0)
	continue;
	else
	c = 0;
	*q++ = tolower(c);
	}
	if(q != buf){
	if(q[-1])
	*q++ = 0;
	*q = 0;
	break;
	}
	}
	return buf;
	}

	static int
	isourdom(char *s)
	{
	Link *l;

	if(strchr(s, '.') == nil)
	return 1;

	for(l = ourdoms.first; l; l = l->next){
	if(dommatch(s, s_to_c(l->p)) == 0)
	return 1;
	}
	return 0;
	}

	int
	forwarding(String *path)
	{
	char cp, s;
	String *lpath;

	if(debug)
	fprint(2, "forwarding(%s)\n", s_to_c(path));

	/* first check if they want loopback */
	lpath = s_copy(s_to_c(s_restart(path)));
	if(nci->rsys && *nci->rsys){
	cp = s_to_c(lpath);
	if(strncmp(cp, "[]!", 3) == 0){
	found:
	s_append(path, "[");
	s_append(path, nci->rsys);
	s_append(path, "]!");
	s_append(path, cp+3);
	s_terminate(path);
	s_free(lpath);
	return 0;
	}
	cp = strchr(cp,'!'); /* skip our domain and check next */
	if(cp++ && strncmp(cp, "[]!", 3) == 0)
	goto found;
	}

	/* if mail is from a trusted IP addr, allow it to forward */
	if(trusted) {
	s_free(lpath);
	return 0;
	}

	/* sender is untrusted; ensure receiver is in one of our domains */
	for(cp = s_to_c(lpath); cp; cp++) / convert receiver lc */
	cp = tolower(cp);

	for(s = s_to_c(lpath); cp = strchr(s, '!'); s = cp+1){
	*cp = 0;
	if(!isourdom(s)){
	s_free(lpath);
	return 1;
	}
	}
	s_free(lpath);
	return 0;
	}

	int
	masquerade(String path, char him)
	{
	char cp, s;
	String *lpath;
	int rv = 0;

	if(debug)
	fprint(2, "masquerade(%s)\n", s_to_c(path));

	if(trusted)
	return 0;
	if(path == nil)
	return 0;

	lpath = s_copy(s_to_c(path));

	/* sender is untrusted; ensure receiver is in one of our domains */
	for(cp = s_to_c(lpath); cp; cp++) / convert receiver lc */
	cp = tolower(cp);
	s = s_to_c(lpath);

	/* scan first element of ! or last element of @ paths */
	if((cp = strchr(s, '!')) != nil){
	*cp = 0;
	if(isourdom(s))
	rv = 1;
	} else if((cp = strrchr(s, '@')) != nil){
	if(isourdom(cp+1))
	rv = 1;
	} else {
	if(isourdom(him))
	rv = 1;
	}

	s_free(lpath);
	return rv;
	}

	/* this is a v4 only check */
	static int
	cidrcheck(char *cp)
	{
	char *p;
	ulong a, m;
	uchar addr[IPv4addrlen];
	uchar mask[IPv4addrlen];

	if(v4peerip == 0)
	return 0;

	/* parse a list of CIDR addresses comparing each to the peer IP addr */
	while(cp && *cp){
	v4parsecidr(addr, mask, cp);
	a = nhgetl(addr);
	m = nhgetl(mask);
	/*
	* if a mask isn't specified, we build a minimal mask
	* instead of using the default mask for that net. in this
	* case we never allow a class A mask (0xff000000).
	*/
	if(strchr(cp, '/') == 0){
	m = 0xff000000;
	p = cp;
	for(p = strchr(p, '.'); p && p[1]; p = strchr(p+1, '.'))
	m = (m>>8)\|0xff000000;

	/* force at least a class B */
	m \|= 0xffff0000;
	}
	if((v4peerip&m) == a)
	return 1;
	cp += strlen(cp)+1;
	}
	return 0;
	}

	int
	isbadguy(void)
	{
	Link *l;

	/* check if this IP address is banned */
	for(l = badguys.first; l; l = l->next)
	if(cidrcheck(s_to_c(l->p)))
	return 1;

	return 0;
	}

	void
	addbadguy(char *p)
	{
	listadd(&badguys, s_copy(p));
	};

	char*
	dumpfile(char *sender)
	{
	int i, fd;
	ulong h;
	static char buf[512];
	char *cp;

	if (sflag == 1){
	cp = ctime(time(0));
	cp[7] = 0;
	if(cp[8] == ' ')
	sprint(buf, "%s/queue.dump/%s%c", SPOOL, cp+4, cp[9]);
	else
	sprint(buf, "%s/queue.dump/%s%c%c", SPOOL, cp+4, cp[8], cp[9]);
	cp = buf+strlen(buf);
	if(access(buf, 0) < 0 && sysmkdir(buf, 0777) < 0)
	return "/dev/null";
	h = 0;
	while(*sender)
	h = h257 + sender++;
	for(i = 0; i < 50; i++){
	h += lrand();
	sprint(cp, "/%lud", h);
	if(access(buf, 0) >= 0)
	continue;
	fd = syscreate(buf, ORDWR, 0666);
	if(fd >= 0){
	if(debug)
	fprint(2, "saving in %s\n", buf);
	close(fd);
	return buf;
	}
	}
	}
	return "/dev/null";
	}

	char *validator = "#9/mail/lib/validateaddress";

	int
	recipok(char *user)
	{
	char cp, p, c;
	char buf[512];
	int n;
	Biobuf *bp;
	int pid;
	Waitmsg *w;
	static int beenhere;

	if(!beenhere){
	beenhere++;
	validator = unsharp(validator);
	}
	if(shellchars(user)){
	syslog(0, "smtpd", "shellchars in user name");
	return 0;
	}

	if(access(validator, AEXEC) == 0)
	switch(pid = fork()) {
	case -1:
	break;
	case 0:
	execl(validator, "validateaddress", user, nil);
	exits(0);
	default:
	while(w = wait()) {
	if(w->pid != pid)
	continue;
	if(w->msg[0] != 0){
	syslog(0, "smtpd", "validateaddress %s: %s", user, w->msg);
	return 0;
	}
	break;
	}
	}

	snprint(buf, sizeof(buf), "%s/names.blocked", UPASLIB);
	bp = sysopen(buf, "r", 0);
	if(bp == 0)
	return 1;
	for(;;){
	cp = Brdline(bp, '\n');
	if(cp == 0)
	break;
	n = Blinelen(bp);
	cp[n-1] = 0;

	while(cp == ' ' \|\| cp == '\t')
	cp++;
	for(p = cp; c = *p; p++){
	if(c == '#')
	break;
	if(c == ' ' \|\| c == '\t')
	break;
	}
	if(p > cp){
	*p = 0;
	if(cistrcmp(user, cp) == 0){
	syslog(0, "smtpd", "names.blocked blocks %s", user);
	Bterm(bp);
	return 0;
	}
	}
	}
	Bterm(bp);
	return 1;
	}

	/*
	* a user can opt out of spam filtering by creating
	* a file in his mail directory named 'nospamfiltering'.
	*/
	int
	optoutofspamfilter(char *addr)
	{
	char p, f;
	int rv;

	p = strchr(addr, '!');
	if(p)
	p++;
	else
	p = addr;


	rv = 0;
	f = smprint("%s/mail/box/%s/nospamfiltering", get9root(), p);
	if(f != nil){
	rv = access(f, 0)==0;
	free(f);
	}

	return rv;
	}