/* * Network listening authentication. * This and all the other network-related  * code is due to Richard Miller. */#include	"all.h"#include	"9p1.h"int allownone;Nvrsafe nvr;int didread;/* *  create a challenge for a fid space */voidmkchallenge(Chan *cp){	int i;	if(!didread && readnvram(&nvr, 0) >= 0)		didread = 1;	srand(truerand());	for(i = 0; i < CHALLEN; i++)		cp->chal[i] = nrand(256);	cp->idoffset = 0;	cp->idvec = 0;}/* *  match a challenge from an attach */Nvrsafe nvr;intauthorize(Chan *cp, Oldfcall *in, Oldfcall *ou){	Ticket t;	Authenticator a;	int x;	ulong bit;	if (cp == cons.srvchan)               /* local channel already safe */		return 1;	if(wstatallow)		/* set to allow entry during boot */		return 1;	if(strcmp(in->uname, "none") == 0)		return allownone || cp->authed;	if(in->type == Toattach9p1)		return 0;	if(!didread)		return 0;	/* decrypt and unpack ticket */	convM2T(in->ticket, &t, nvr.machkey);	if(t.num != AuthTs){print("bad AuthTs num\n");		return 0;	}	/* decrypt and unpack authenticator */	convM2A(in->auth, &a, t.key);	if(a.num != AuthAc){print("bad AuthAc num\n");		return 0;	}	/* challenges must match */	if(memcmp(a.chal, cp->chal, sizeof(a.chal)) != 0){print("bad challenge\n");		return 0;	}	/*	 *  the id must be in a valid range.  the range is specified by a	 *  lower bount (idoffset) and a bit vector (idvec) where a	 *  bit set to 1 means unusable	 */	lock(&cp->idlock);	x = a.id - cp->idoffset;	bit = 1<<x;	if(x < 0 || x > 31 || (bit&cp->idvec)){		unlock(&cp->idlock);		return 0;	}	cp->idvec |= bit;	/* normalize the vector */	while(cp->idvec&0xffff0001){		cp->idvec >>= 1;		cp->idoffset++;	}	unlock(&cp->idlock);	/* ticket name and attach name must match */	if(memcmp(in->uname, t.cuid, sizeof(in->uname)) != 0){print("names don't match\n");		return 0;	}	/* copy translated name into input record */	memmove(in->uname, t.suid, sizeof(in->uname));	/* craft a reply */	a.num = AuthAs;	memmove(a.chal, cp->rchal, CHALLEN);	convA2M(&a, ou->rauth, t.key);	cp->authed = 1;	return 1;}