#include	"u.h"#include	"../port/lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"../port/error.h" #include	<libsec.h> enum{	Hashlen=	SHA1dlen,	Maxhash=	256,}; /* *  if a process knows cap->cap, it can change user *  to capabilty->user. */typedef struct Caphash	Caphash;struct Caphash{	Caphash	*next;	char		hash[Hashlen];	ulong		ticks;}; struct{	QLock;	Caphash	*first;	int	nhash;} capalloc; enum{	Qdir,	Qhash,	Quse,}; /* caphash must be last */Dirtab capdir[] ={	".",		{Qdir,0,QTDIR},	0,		DMDIR|0500,	"capuse",	{Quse},		0,		0222,	"caphash",	{Qhash},	0,		0200,};int ncapdir = nelem(capdir); static Chan*capattach(char *spec){	return devattach(L'¤', spec);} static Walkqid*capwalk(Chan *c, Chan *nc, char **name, int nname){	return devwalk(c, nc, name, nname, capdir, ncapdir, devgen);} static voidcapremove(Chan *c){	if(iseve() && c->qid.path == Qhash)		ncapdir = nelem(capdir)-1;	else		error(Eperm);}  static longcapstat(Chan *c, uchar *db, long n){	return devstat(c, db, n, capdir, ncapdir, devgen);} /* *  if the stream doesn't exist, create it */static Chan*capopen(Chan *c, int omode){	if(c->qid.type & QTDIR){		if(omode != OREAD)			error(Ebadarg);		c->mode = omode;		c->flag |= COPEN;		c->offset = 0;		return c;	} 	switch((ulong)c->qid.path){	case Qhash:		if(!iseve())			error(Eperm);		break;	} 	c->mode = openmode(omode);	c->flag |= COPEN;	c->offset = 0;	return c;} /*static char*hashstr(uchar *hash){	static char buf[2*Hashlen+1];	int i; 	for(i = 0; i < Hashlen; i++)		sprint(buf+2*i, "%2.2ux", hash[i]);	buf[2*Hashlen] = 0;	return buf;} */ static Caphash*remcap(uchar *hash){	Caphash *t, **l; 	qlock(&capalloc); 	/* find the matching capability */	for(l = &capalloc.first; *l != nil;){		t = *l;		if(memcmp(hash, t->hash, Hashlen) == 0)			break;		l = &t->next;	}	t = *l;	if(t != nil){		capalloc.nhash--;		*l = t->next;	}	qunlock(&capalloc); 	return t;} /* add a capability, throwing out any old ones */static voidaddcap(uchar *hash){	Caphash *p, *t, **l; 	p = smalloc(sizeof *p);	memmove(p->hash, hash, Hashlen);	p->next = nil;	p->ticks = m->ticks; 	qlock(&capalloc); 	/* trim extras */	while(capalloc.nhash >= Maxhash){		t = capalloc.first;		if(t == nil)			panic("addcap");		capalloc.first = t->next;		free(t);		capalloc.nhash--;	} 	/* add new one */	for(l = &capalloc.first; *l != nil; l = &(*l)->next)		;	*l = p;	capalloc.nhash++; 	qunlock(&capalloc);} static voidcapclose(Chan*){} static longcapread(Chan *c, void *va, long n, vlong){	switch((ulong)c->qid.path){	case Qdir:		return devdirread(c, va, n, capdir, ncapdir, devgen); 	default:		error(Eperm);		break;	}	return n;} static longcapwrite(Chan *c, void *va, long n, vlong){	Caphash *p;	char *cp;	uchar hash[Hashlen];	char *key, *from, *to;	char err[256]; 	switch((ulong)c->qid.path){	case Qhash:		if(!iseve())			error(Eperm);		if(n < Hashlen)			error(Eshort);		memmove(hash, va, Hashlen);		addcap(hash);		break; 	case Quse:		/* copy key to avoid a fault in hmac_xx */		cp = nil;		if(waserror()){			free(cp);			nexterror();		}		cp = smalloc(n+1);		memmove(cp, va, n);		cp[n] = 0; 		from = cp;		key = strrchr(cp, '@');		if(key == nil)			error(Eshort);		*key++ = 0; 		hmac_sha1((uchar*)from, strlen(from), (uchar*)key, strlen(key), hash, nil); 		p = remcap(hash);		if(p == nil){			snprint(err, sizeof err, "invalid capability %s@%s", from, key);			error(err);		} 		/* if a from user is supplied, make sure it matches */		to = strchr(from, '@');		if(to == nil){			to = from;		} else {			*to++ = 0;			if(strcmp(from, up->user) != 0)				error("capability must match user");		} 		/* set user id */		kstrdup(&up->user, to);		up->basepri = PriNormal; 		free(p);		free(cp);		poperror();		break; 	default:		error(Eperm);		break;	} 	return n;} Dev capdevtab = {	L'¤',	"cap", 	devreset,	devinit,	devshutdown,	capattach,	capwalk,	capstat,	capopen,	devcreate,	capclose,	capread,	devbread,	capwrite,	devbwrite,	capremove,	devwstat};