/*
 *  devssl - secure sockets layer emulation
 */
#include	"lib9.h"
#include	"dat.h"
#include	"fns.h"
#include	"error.h"

#include	"libcrypt.h"

typedef struct OneWay OneWay;
struct OneWay
{
	QLock	q;
	QLock	ctlq;

	void	*state;		/* encryption state */
	int	slen;		/* hash data length */
	uchar	*secret;	/* secret */
	ulong	mid;		/* message id */
};

enum
{
	/* connection states */
	Sincomplete=	0,
	Sclear,
	Sencrypting,
	Sdigesting,

	/* encryption algorithms */
	Noencryption=	0,
	RC4=		3
};

typedef struct Dstate Dstate;
struct Dstate
{
	Chan	*c;		/* io channel */
	uchar	state;		/* state of connection */
	int	ref;		/* serialized by dslock for atomic destroy */

	uchar	encryptalg;	/* encryption algorithm */
	ushort	blocklen;	/* blocking length */

	ushort	diglen;		/* length of digest */
	DigestState *(*hf)(uchar*, ulong, uchar*, DigestState*);	/* hash func */

	/* for SSL format */
	int	max;		/* maximum unpadded data per msg */
	int	maxpad;		/* maximum padded data per msg */

	/* input side */
	OneWay	in;
	Block	*processed;
	Block	*unprocessed;

	/* output side */
	OneWay	out;

	/* protections */
	char	user[NAMELEN];
	int	perm;
};

Lock	dslock;
int	dshiwat;
int	maxdstate = 20;
Dstate** dstate;

enum
{
	Maxdmsg=	1<<16,
	Maxdstate=	1<<12
};

enum{
	Qtopdir		= 1,	/* top level directory */
	Qclonus,
	Qconvdir,		/* directory for a conversation */
	Qdata,
	Qctl,
	Qsecretin,
	Qsecretout
};

#define TYPE(x) 	((x).path & 0xf)
#define CONV(x) 	(((x).path >> 4)&(Maxdstate-1))
#define QID(c, y) 	(((c)<<4) | (y))

/* for generating random fill */
ulong badlong;
uchar *badarray = (uchar*)&badlong;

void producerand(void);

static void	ensure(Dstate*, Block**, int);
static void	consume(Block**, uchar*, int);
static void	setsecret(OneWay*, uchar*, int);
static Block*	encryptb(Dstate*, Block*, int);
static Block*	decryptb(Dstate*, Block*);
static Block*	digestb(Dstate*, Block*, int);
static void	checkdigestb(Dstate*, Block*);
static Chan*	buftochan(char*);
static void	sslhangup(Dstate*);
static Dstate*	dsclone(Chan *c);
static void	dsnew(Chan *c, Dstate **);

int
sslgen(Chan *c, Dirtab *d, int nd, int s, Dir *dp)
{
	Qid q;
	Dstate *ds;
	char name[16], *p, *nm;

	USED(nd);
	USED(d);
	q.vers = 0;
	switch(TYPE(c->qid)) {
	case Qtopdir:
		if(s < dshiwat) {
			sprint(name, "%d", s);
			q.path = QID(s, Qconvdir)|CHDIR;
			ds = dstate[s];
			if(ds != 0)
				nm = ds->user;
			else
				nm = eve;
			devdir(c, q, name, 0, nm, CHDIR|0555, dp);
			return 1;
		}
		if(s > dshiwat)
			return -1;
		q.path = QID(0, Qclonus);
		devdir(c, q, "clone", 0, eve, 0555, dp);
		return 1;
	case Qconvdir:
		ds = dstate[CONV(c->qid)];
		if(ds != 0)
			nm = ds->user;
		else
			nm = eve;
		switch(s) {
		default:
			return -1;
		case 0:
			q.path = QID(CONV(c->qid), Qctl);
			p = "ctl";
			break;
		case 1:
			q.path = QID(CONV(c->qid), Qdata);
			p = "data";
			break;
		case 2:
			q.path = QID(CONV(c->qid), Qsecretin);
			p = "secretin";
			break;
		case 3:
			q.path = QID(CONV(c->qid), Qsecretout);
			p = "secretout";
			break;
		}
		devdir(c, q, p, 0, nm, 0660, dp);
		return 1;
	}
	return -1;
}

void
sslinit(void)
{
	if((dstate = malloc(sizeof(Dstate*) * maxdstate)) == 0)
		panic("sslinit");
}

Chan *
sslattach(void *spec)
{
	Chan *c;

	c = devattach('D', spec);
	c->qid.path = QID(0, Qtopdir)|CHDIR;
	c->qid.vers = 0;
	return c;
}

Chan *
sslclone(Chan *c, Chan *nc)
{
	Dstate *s;

	return devclone(c, nc);
}

int
sslwalk(Chan *c, char *name)
{
	return devwalk(c, name, 0, 0, sslgen);
}

void
sslstat(Chan *c, char *db)
{
	devstat(c, db, 0, 0, sslgen);
}

Chan *
sslopen(Chan *c, int omode)
{
	Dstate *s, **pp;
	int perm;

	perm = 0;
	omode &= 3;
	switch(omode) {
	case OREAD:
		perm = 4;
		break;
	case OWRITE:
		perm = 2;
		break;
	case ORDWR:
		perm = 6;
		break;
	}

	switch(TYPE(c->qid)) {
	default:
		panic("sslopen");
	case Qtopdir:
	case Qconvdir:
		if(omode != OREAD)
			error(Eperm);
		break;
	case Qclonus:
		s = dsclone(c);
		if(s == 0)
			error(Enodev);
		break;
	case Qctl:
	case Qdata:
	case Qsecretin:
	case Qsecretout:
		if(waserror()) {
			unlock(&dslock);
			nexterror();
		}
		lock(&dslock);
		pp = &dstate[CONV(c->qid)];
		s = *pp;
		if(s == 0)
			dsnew(c, pp);
		else {
			if((perm & (s->perm>>6)) != perm
			   && (strcmp(up->env->user, s->user) != 0
			     || (perm & s->perm) != perm))
				error(Eperm);

			s->ref++;
		}
		unlock(&dslock);
		poperror();
		break;
	}
	c->mode = openmode(omode);
	c->flag |= COPEN;
	c->offset = 0;
	return c;
}

void
sslcreate(Chan *c, char *name, int omode, ulong perm)
{
	USED(c);
	USED(name);
	USED(omode);
	USED(perm);
	error(Eperm);
}

void
sslremove(Chan *c)
{
	USED(c);
	error(Eperm);
}

void
sslwstat(Chan *c, char *dp)
{
	Dir d;
	Dstate *s;

	convM2D(dp, &d);

	s = dstate[CONV(c->qid)];
	if(s == 0)
		error(Ebadusefd);
	if(strcmp(s->user, up->env->user) != 0)
		error(Eperm);

	memmove(s->user, d.uid, NAMELEN);
	s->perm = d.mode;
}

void
sslclose(Chan *c)
{
	Dstate *s;

	switch(TYPE(c->qid)) {
	case Qctl:
	case Qdata:
	case Qsecretin:
	case Qsecretout:
		if((c->flag & COPEN) == 0)
			break;

		s = dstate[CONV(c->qid)];
		if(s == 0)
			break;

		lock(&dslock);
		if(--s->ref > 0) {
			unlock(&dslock);
			break;
		}
		dstate[CONV(c->qid)] = 0;
		unlock(&dslock);

		sslhangup(s);
		if(s->c)
			cclose(s->c);
		if(s->in.secret)
			free(s->in.secret);
		if(s->out.secret)
			free(s->out.secret);
		if(s->in.state)
			free(s->in.state);
		if(s->out.state)
			free(s->out.state);
		free(s);

	}
}

static int
blen(Block *bp)
{
	int i = 0;

	for(; bp; bp = bp->next)
		i += BLEN(bp);
	return i;
}

/*
 *  make sure we have at least 'n' bytes in list 'l'
 */
static void
ensure(Dstate *s, Block **l, int n)
{
	int sofar, i;
	Block *b, *bl;

	sofar = 0;
	for(b = *l; b; b = b->next){
		sofar += BLEN(b);
		if(sofar >= n)
			return;
		l = &b->next;
	}

	while(sofar < n){
		bl = (*devtab[s->c->type].bread)(s->c, Maxdmsg, 0);
		if(bl == 0)
			error(Ehungup);
		*l = bl;
		i = 0;
		for(b = bl; b; b = b->next){
			i += BLEN(b);
			l = &b->next;
		}
		if(i == 0)
			error(Ehungup);
		sofar += i;
	}
}

/*
 *  copy 'n' bytes from 'l' into 'p' and free
 *  the bytes in 'l'
 */
static void
consume(Block **l, uchar *p, int n)
{
	Block *b;
	int i;

	for(; *l && n > 0; n -= i){
		b = *l;
		i = BLEN(b);
		if(i > n)
			i = n;
		memmove(p, b->rp, i);
		b->rp += i;
		p += i;
		if(BLEN(b) < 0)
			panic("consume");
		if(BLEN(b))
			break;
		*l = b->next;
		freeb(b);
	}
}

/*
 *  remove at most n bytes from the queue, if discard is set
 *  dump the remainder
 */
static Block*
qremove(Block **l, int n, int discard)
{
	Block *nb, *b, *first;
	int i;

	first = *l;
	for(b = first; b; b = b->next){
		i = BLEN(b);
		if(i == n){
			if(discard){
				freeblist(b->next);
				*l = 0;
			} else
				*l = b->next;
			b->next = 0;
			break;
		} else if(i > n){
			i -= n;
			if(discard){
				freeblist(b->next);
				b->wp -= i;
				*l = 0;
			} else {
				nb = allocb(i);
				memmove(nb->wp, b->rp+n, i);
				nb->wp += i;
				b->wp -= i;
				nb->next = b->next;
				*l = nb;
			}
			b->next = 0;
			if(BLEN(b) < 0)
				panic("qremove");
			return first;
		} else
			n -= i;
		if(BLEN(b) < 0)
			panic("qremove");
	}
	*l = 0;
	return first;
}

Block*
sslbread(Chan *c, long n, ulong offset)
{
	volatile struct { Dstate *s; } s;
	Block *b;
	uchar count[2];
	int len, pad;

	USED(offset);

	s.s = dstate[CONV(c->qid)];
	if(s.s == 0)
		panic("sslbread");
	if(s.s->state == Sincomplete)
		error(Ebadusefd);

	if(waserror()){
		qunlock(&s.s->in.q);
		sslhangup(s.s);
		nexterror();
	}
	qlock(&s.s->in.q);

	if(s.s->processed == 0){
		/* read in the whole message */
		ensure(s.s, &s.s->unprocessed, 2);
		consume(&s.s->unprocessed, count, 2);
		if(count[0] & 0x80){
			len = ((count[0] & 0x7f)<<8) | count[1];
			ensure(s.s, &s.s->unprocessed, len);
			pad = 0;
		} else {
			len = ((count[0] & 0x3f)<<8) | count[1];
			ensure(s.s, &s.s->unprocessed, len+1);
			consume(&s.s->unprocessed, count, 1);
			pad = count[0];
			if(pad > len){
				print("pad %d buf len %d\n", pad, len);
				error("bad pad in ssl message");
			}
		}

		/* put extra on unprocessed queue */
		s.s->processed = qremove(&s.s->unprocessed, len, 0);

		if(waserror()){
			qunlock(&s.s->in.ctlq);
			nexterror();
		}
		qlock(&s.s->in.ctlq);
		switch(s.s->state){
		case Sencrypting:
			s.s->processed = decryptb(s.s, s.s->processed);
			break;
		case Sdigesting:
			s.s->processed = pullupblock(s.s->processed, s.s->diglen);
			if(s.s->processed == 0)
				error("ssl message too short");
			checkdigestb(s.s, s.s->processed);
			s.s->processed->rp += s.s->diglen;
			break;
		}
		qunlock(&s.s->in.ctlq);
		poperror();

		/* remove pad */
		if(pad)
			s.s->processed = qremove(&s.s->processed, len - pad, 1);
	}

	/* return at most what was asked for */
	b = qremove(&s.s->processed, n, 0);

	qunlock(&s.s->in.q);
	poperror();

	return b;
}

long
sslread(Chan *c, void *a, long n, ulong offset)
{
	volatile struct { Block *b; } b;
	Block *nb;
	uchar *va;
	int i;
	char buf[128];

	if(c->qid.path & CHDIR)
		return devdirread(c, a, n, 0, 0, sslgen);

	switch(TYPE(c->qid)) {
	default:
		error(Ebadusefd);
	case Qctl:
		sprint(buf, "%d", CONV(c->qid));
		return readstr(offset, a, n, buf);
	case Qdata:
		b.b = sslbread(c, n, offset);
		break;
	}

	if(waserror()){
		freeblist(b.b);
		nexterror();
	}

	n = 0;
	va = a;
	for(nb = b.b; nb; nb = nb->next){
		i = BLEN(nb);
		memmove(va+n, nb->rp, i);
		n += i;
	}

	freeblist(b.b);
	poperror();

	return n;
}

/*
 *  this algorithm doesn't have to be great since we're just
 *  trying to obscure the block fill
 */
static void
initbadrand(void)
{
	badlong = fastrand();
}

static void
randfill(uchar *buf, int len)
{
	int j;

	while(len-- > 0){
		j = (((ulong)buf) & 3);
		if(j == 3)
			badlong = (badlong*48271)%(2^31 - 1);
		*buf++ = badarray[j];
	}
}

/*
 *  use SSL record format, add in count and digest or encrypt
 */
long
sslbwrite(Chan *c, Block *b, ulong offset)
{
	volatile struct { Dstate *s; } s;
	volatile struct { Block *b; } bb;
	Block *nb;
	int h, n, m, pad, rv;
	uchar *p;

	bb.b = b;
	s.s = dstate[CONV(c->qid)];
	if(s.s == 0)
		panic("sslbwrite");
	if(s.s->state == Sincomplete){
		freeb(b);
		error(Ebadusefd);
	}

	if(waserror()){
		qunlock(&s.s->out.q);
		if(bb.b)
			freeb(bb.b);
		sslhangup(s.s);
		nexterror();
	}
	qlock(&s.s->out.q);

	rv = 0;
	while(bb.b){
		m = n = BLEN(bb.b);
		h = s.s->diglen + 2;

		/* trim to maximum block size */
		pad = 0;
		if(m > s.s->max){
			m = s.s->max;
		} else if(s.s->blocklen != 1){
			pad = m%s.s->blocklen;
			if(pad){
				if(m > s.s->maxpad){
					pad = 0;
					m = s.s->maxpad;
				} else {
					pad = s.s->blocklen - pad;
					h++;
				}
			}
		}

		rv += m;
		if(m != n){
			nb = allocb(m + h + pad);
			memmove(nb->wp + h, bb.b->rp, m);
			nb->wp += m + h;
			bb.b->rp += m;
		} else {
			/* add header space */
			nb = padblock(bb.b, h);
			bb.b = 0;
		}
		m += s.s->diglen;

		/* SSL style count */
		if(pad){
			nb = padblock(nb, -pad);
			randfill(nb->wp, pad);
			nb->wp += pad;
			m += pad;

			p = nb->rp;
			p[0] = (m>>8);
			p[1] = m;
			p[2] = pad;
			offset = 3;
		} else {
			p = nb->rp;
			p[0] = (m>>8) | 0x80;
			p[1] = m;
			offset = 2;
		}

		switch(s.s->state){
		case Sencrypting:
			nb = encryptb(s.s, nb, offset);
			break;
		case Sdigesting:
			nb = digestb(s.s, nb, offset);
			break;
		}

		m = BLEN(nb);
		(*devtab[s.s->c->type].bwrite)(s.s->c, nb, s.s->c->offset);
		s.s->c->offset += m;
	}
	qunlock(&s.s->out.q);
	poperror();

	return rv;
}

static void
setsecret(OneWay *w, uchar *secret, int n)
{
	if(w->secret)
		free(w->secret);

	w->secret = malloc(n);
	memmove(w->secret, secret, n);
	w->slen = n;
	w->mid = 0;

}


static void
initRC4key(OneWay *w)
{
	if(w->state){
		free(w->state);
		w->state = 0;
	}

	if(w->slen > 5)
		w->slen = 5;

	w->state = malloc(sizeof(RC4state));
	setupRC4state(w->state, w->secret, w->slen);
}

long
sslwrite(Chan *c, void *a, long n, ulong offset)
{
	volatile struct { Dstate *s; } s;
	volatile struct { Block *b; } b;
	int m, t;
	char *p, *e, buf[32];

	s.s = dstate[CONV(c->qid)];
	if(s.s == 0)
		panic("sslwrite");

	t = TYPE(c->qid);
	if(t == Qdata){
		if(s.s->state == Sincomplete)
			error(Ebadusefd);

		p = a;
		e = p + n;
		do {
			m = e - p;
			if(m > s.s->max)
				m = s.s->max;
	
			b.b = allocb(m);
			if(waserror()){
				freeb(b.b);
				nexterror();
			}
			memmove(b.b->wp, p, m);
			poperror();
			b.b->wp += m;
	
			sslbwrite(c, b.b, offset);

			p += m;
		} while(p < e);
		return n;
	}

	/* mutex with operations using what we're about to change */
	if(waserror()){
		qunlock(&s.s->in.ctlq);
		qunlock(&s.s->out.q);
		nexterror();
	}
	qlock(&s.s->in.ctlq);
	qlock(&s.s->out.q);

	switch(t){
	default:
		panic("sslwrite");
	case Qsecretin:
		setsecret(&s.s->in, a, n);
		goto out;
		return n;
	case Qsecretout:
		setsecret(&s.s->out, a, n);
		goto out;
		return n;
	case Qctl:
		break;
	}

	if(n >= sizeof(buf))
		error(Ebadarg);
	strncpy(buf, a, n);
	buf[n] = 0;
	p = strchr(buf, '\n');
	if(p)
		*p = 0;
	p = strchr(buf, ' ');
	if(p)
		*p++ = 0;

	if(strcmp(buf, "fd") == 0){
		s.s->c = buftochan(p);

		/* default is clear (msg delimiters only) */
		s.s->state = Sclear;
		s.s->blocklen = 1;
		s.s->diglen = 0;
		s.s->maxpad = s.s->max = (1<<15) - s.s->diglen - 1;
	} else if(strcmp(buf, "alg") == 0 && p != 0){
		s.s->blocklen = 1;
		s.s->diglen = 0;

		if(s.s->c == 0)
			error("must set fd before algorithm");

		if(strcmp(p, "clear") == 0){
			s.s->state = Sclear;
			s.s->maxpad = s.s->max = (1<<15) - s.s->diglen - 1;
			goto out;
		}

		if(s.s->in.secret && s.s->out.secret == 0)
			setsecret(&s.s->out, s.s->in.secret, s.s->in.slen);
		if(s.s->out.secret && s.s->in.secret == 0)
			setsecret(&s.s->in, s.s->out.secret, s.s->out.slen);
		if(strcmp(p, "md5") == 0){
			s.s->hf = md5;
			s.s->diglen = MD5dlen;
			s.s->state = Sdigesting;
		} else if(strcmp(p, "sha") == 0){
			s.s->hf = sha;
			s.s->diglen = SHAdlen;
			s.s->state = Sdigesting;
		} else if(strcmp(p, "rc4") == 0){
			if(s.s->in.secret == 0 || s.s->out.secret == 0)
				error(Ebadarg);
			s.s->encryptalg = RC4;
			s.s->blocklen = 1;
			initRC4key(&s.s->in);
			initRC4key(&s.s->out);
			s.s->state = Sencrypting;
		} else
			error(Ebadarg);

		if(s.s->blocklen != 1){
			s.s->max = (1<<15) - s.s->diglen - 1;
			s.s->max -= s.s->max % s.s->blocklen;
			s.s->maxpad = (1<<14) - s.s->diglen - 1;
			s.s->maxpad -= s.s->maxpad % s.s->blocklen;
		} else
			s.s->maxpad = s.s->max = (1<<15) - s.s->diglen - 1;
	} else
		error(Ebadarg);

out:
	qunlock(&s.s->in.ctlq);
	qunlock(&s.s->out.q);
	poperror();
	return n;
}


static Block*
encryptb(Dstate *s, Block *b, int offset)
{

	switch(s->encryptalg){
	case RC4:
		rc4(s->out.state, b->rp + offset, BLEN(b) - offset);
		break;
	}
	return b;
}

static Block*
decryptb(Dstate *s, Block *inb)
{
	Block *b, **l;
	int i;

	l = &inb;
	for(b = inb; b; b = b->next){
		/* make sure we have a multiple of s->blocklen */
		if(s->blocklen > 1){
			i = BLEN(b);
			if(i % s->blocklen){
				*l = b = pullupblock(b, i + s->blocklen - (i%s->blocklen));
				if(b == 0)
					error("ssl encrypted message too short");
			}
		}
		l = &b->next;

		/* decrypt */
		switch(s->encryptalg){
		case RC4:
			rc4(s->in.state, b->rp, BLEN(b));
			break;
		}
	}
	return inb;
}

static Block*
digestb(Dstate *s, Block *b, int offset)
{
	uchar *p;
	DigestState ss;
	uchar msgid[4];
	ulong n, h;
	OneWay *w;

	w = &s->out;

	memset(&ss, 0, sizeof(ss));
	h = s->diglen + offset;
	n = BLEN(b) - h;

	/* hash secret + message */
	(*s->hf)(w->secret, w->slen, 0, &ss);
	(*s->hf)(b->rp + h, n, 0, &ss);

	/* hash message id */
	p = msgid;
	n = w->mid++;
	*p++ = n>>24;
	*p++ = n>>16;
	*p++ = n>>8;
	*p = n;
	(*s->hf)(msgid, 4, b->rp + offset, &ss);

	return b;
}

static void
checkdigestb(Dstate *s, Block *inb)
{
	uchar *p;
	DigestState ss;
	uchar msgid[4];
	int n, h;
	OneWay *w;
	uchar digest[128];
	Block *b;

	w = &s->in;

	memset(&ss, 0, sizeof(ss));

	/* hash secret */
	(*s->hf)(w->secret, w->slen, 0, &ss);

	/* hash message */
	h = s->diglen;
	for(b = inb; b; b = b->next){
		n = BLEN(b) - h;
		if(n < 0)
			panic("checkdigestb");
		(*s->hf)(b->rp + h, n, 0, &ss);
		h = 0;
	}

	/* hash message id */
	p = msgid;
	n = w->mid++;
	*p++ = n>>24;
	*p++ = n>>16;
	*p++ = n>>8;
	*p = n;
	(*s->hf)(msgid, 4, digest, &ss);

	if(memcmp(digest, inb->rp, s->diglen) != 0)
		error("bad digest");
}

/* get channel associated with an fd */
static Chan*
buftochan(char *p)
{
	Chan *c;
	int fd;

	if(p == 0)
		error(Ebadarg);
	fd = strtoul(p, 0, 0);
	if(fd < 0)
		error(Ebadarg);
	c = fdtochan(up->env->fgrp, fd, -1, 0, 1);	/* error check and inc ref */
	return c;
}

/* hand up a digest connection */
static void
sslhangup(Dstate *s)
{
	Block *b;

	qlock(&s->in.q);
	for(b = s->processed; b; b = s->processed){
		s->processed = b->next;
		freeb(b);
	}
	if(s->unprocessed){
		freeb(s->unprocessed);
		s->unprocessed = 0;
	}
	s->state = Sincomplete;
	qunlock(&s->in.q);
}

/*
 *  crypt's interface to system, included here to override the
 *  library version
 */
void
handle_exception(int type, char *exception)
{
	if(type == CRITICAL)
		panic("crypt library: %s: %r", exception);
	else
		print("crypt library: %s: %r\n", exception);
}

extern void rbcheck(char*);

void*
crypt_malloc(int size)
{
	void *x;

	x = malloc(size);
	if(x == 0)
		handle_exception(CRITICAL, "out of memory");
	return x;
}

void
crypt_free(void *x)
{
	if(x == 0)
		handle_exception(CRITICAL, "freeing null pointer");
	free(x);
}


static Dstate*
dsclone(Chan *ch)
{
	Dstate **pp, **ep, **np;
	int newmax;

	if(waserror()) {
		unlock(&dslock);
		nexterror();
	}
	lock(&dslock);
	ep = &dstate[maxdstate];
	for(pp = dstate; pp < ep; pp++) {
		if(*pp == 0) {
			dsnew(ch, pp);
			break;
		}
	}
	if(pp >= ep) {
		if(maxdstate >= Maxdstate) {
			unlock(&dslock);
			poperror();
			return 0;
		}
		newmax = 2 * maxdstate;
		if(newmax > Maxdstate)
			newmax = Maxdstate;
		np = realloc(dstate, sizeof(Dstate*) * newmax);
		if(np == 0)
			error(Enomem);
		dstate = np;
		pp = &dstate[maxdstate];
		memset(pp, 0, sizeof(Dstate*)*(newmax - maxdstate));
		maxdstate = newmax;
		dsnew(ch, pp);
	}
	unlock(&dslock);
	poperror();
	return *pp;
}

static void
dsnew(Chan *ch, Dstate **pp)
{
	Dstate *s;
	int t;

	*pp = s = malloc(sizeof(*s));
	if(!s)
		error(Enomem);
	if(pp - dstate >= dshiwat)
		dshiwat++;
	memset(s, 0, sizeof(*s));
	s->state = Sincomplete;
	s->ref = 1;
	strncpy(s->user, up->env->user, sizeof(s->user));
	s->perm = 0660;
	t = TYPE(ch->qid);
	if(t == Qclonus)
		t = Qctl;
	ch->qid.path = QID(pp - dstate, t);
	ch->qid.vers = 0;
}