keyfs.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

			if(strcmp(data, status[i]) == 0){
				f->user->status = i;
				break;
			}
		if(i == Smax)
			return "unknown status";
		f->user->bad = 0;
		thdr.count = n;
		break;
	case Qexpire:
		data[n] = '\0';
		if(p = strchr(data, '\n'))
			*p = '\0';
		else
			p = &data[n];
		if(strcmp(data, "never") == 0)
			expire = 0;
		else{
			expire = strtoul(data, &data, 10);
			if(data != p)
				return "bad expiration date";
		}
		f->user->expire = expire;
		f->user->warnings = 0;
		thdr.count = n;
		break;
	case Qlog:
		data[n] = '\0';
		if(strcmp(data, "good") == 0)
			f->user->bad = 0;
		else
			f->user->bad++;
		if(f->user->bad && ((f->user->bad)%MAXBAD) == 0)
			f->user->purgatory = time(0) + f->user->bad;
		return 0;
	case Qwarnings:
		data[n] = '\0';
		f->user->warnings = strtoul(data, 0, 10);
		thdr.count = n;
		break;
	case Qroot:
	case Quser:
	default:
		return "permission denied";
	}
	writeusers();
	return 0;
}

char *
Remove(Fid *f)
{
	if(!f->busy)
		return "permission denied";
	if(f->qtype == Qwarnings)
		f->user->warnings = 0;
	else if(f->qtype == Quser)
		removeuser(f->user);
	else {
		Clunk(f);
		return "permission denied";
	}
	Clunk(f);
	writeusers();
	return 0;
}

char *
Stat(Fid *f)
{
	static uchar statbuf[1024];

	if(!f->busy)
		return "stat on unattached fid";
	thdr.nstat = dostat(f->user, f->qtype, statbuf, sizeof statbuf);
	if(thdr.nstat <= BIT16SZ)
		return "stat buffer too small";
	thdr.stat = statbuf;
	return 0;
}

char *
Wstat(Fid *f)
{
	Dir d;
	int n;
	char buf[1024];

	if(!f->busy || f->qtype != Quser)
		return "permission denied";
	if(rhdr.nstat > sizeof buf)
		return "wstat buffer too big";
	if(convM2D(rhdr.stat, rhdr.nstat, &d, buf) == 0)
		return "bad stat buffer";
	n = strlen(d.name);
	if(n == 0 || n >= Namelen)
		return "bad user name";
	if(finduser(d.name))
		return "user already exists";
	if(!removeuser(f->user))
		return "user previously removed";
	free(f->user->name);
	f->user->name = strdup(d.name);
	if(f->user->name == nil)
		error("wstat: malloc failed: %r");
	insertuser(f->user);
	writeusers();
	return 0;
}

Qid
mkqid(User *u, ulong qtype)
{
	Qid q;

	q.vers = 0;
	q.path = qtype;
	if(u)
		q.path |= u->uniq * 0x100;
	if(qtype == Quser || qtype == Qroot)
		q.type = QTDIR;
	else
		q.type = QTFILE;
	return q;
}

int
dostat(User *user, ulong qtype, void *p, int n)
{
	Dir d;

	if(qtype == Quser)
		d.name = user->name;
	else
		d.name = qinfo[qtype];
	d.uid = d.gid = d.muid = "auth";
	d.qid = mkqid(user, qtype);
	if(d.qid.type & QTDIR)
		d.mode = 0777|DMDIR;
	else
		d.mode = 0666;
	d.atime = d.mtime = time(0);
	d.length = 0;
	return convD2M(&d, p, n);
}

int
passline(Biobuf *b, void *vbuf)
{
	char *buf = vbuf;

	if(Bread(b, buf, KEYDBLEN) != KEYDBLEN)
		return 0;
	decrypt(authkey, buf, KEYDBLEN);
	buf[Namelen-1] = '\0';
	return 1;
}

void
randombytes(uchar *p, int len)
{
	int i, fd;

	fd = open("/dev/random", OREAD);
	if(fd < 0){
		fprint(2, "keyfs: can't open /dev/random, using rand()\n");
		srand(time(0));
		for(i = 0; i < len; i++)
			p[i] = rand();
		return;
	}
	read(fd, p, len);
	close(fd);
}

void
oldCBCencrypt(char *key7, uchar *p, int len)
{
	uchar ivec[8];
	uchar key[8];
	DESstate s;

	memset(ivec, 0, 8);
	des56to64((uchar*)key7, key);
	setupDESstate(&s, key, ivec);
	desCBCencrypt((uchar*)p, len, &s);
}

void
oldCBCdecrypt(char *key7, uchar *p, int len)
{
	uchar ivec[8];
	uchar key[8];
	DESstate s;

	memset(ivec, 0, 8);
	des56to64((uchar*)key7, key);
	setupDESstate(&s, key, ivec);
	desCBCdecrypt((uchar*)p, len, &s);

}

void
writeusers(void)
{
	int fd, i, nu;
	User *u;
	uchar *p, *buf;
	ulong expire;

	/* count users */
	nu = 0;
	for(i = 0; i < Nuser; i++)
		for(u = users[i]; u; u = u->link)
			nu++;

	/* pack into buffer */
	buf = malloc(KEYDBOFF + nu*KEYDBLEN);
	if(buf == 0){
		fprint(2, "keyfs: can't write keys file, out of memory\n");
		return;
	}
	p = buf;
	randombytes(p, KEYDBOFF);
	p += KEYDBOFF;
	for(i = 0; i < Nuser; i++)
		for(u = users[i]; u; u = u->link){
			strncpy((char*)p, u->name, Namelen);
			p += Namelen;
			memmove(p, u->key, DESKEYLEN);
			p += DESKEYLEN;
			*p++ = u->status;
			*p++ = u->warnings;
			expire = u->expire;
			*p++ = expire;
			*p++ = expire >> 8;
			*p++ = expire >> 16;
			*p++ = expire >> 24;
			memmove(p, u->secret, SECRETLEN);
			p += SECRETLEN;
		}

	/* encrypt */
	oldCBCencrypt(authkey, buf, p - buf);

	/* write file */
	fd = create(userkeys, OWRITE, 0660);
	if(fd < 0){
		free(buf);
		fprint(2, "keyfs: can't write keys file\n");
		return;
	}
	if(write(fd, buf, p - buf) != (p - buf))
		fprint(2, "keyfs: can't write keys file\n");

	free(buf);
	close(fd);
}

int
readusers(void)
{
	int fd, i, n, nu;
	uchar *p, *buf, *ep;
	User *u;
	Dir *d;

	/* read file into an array */
	fd = open(userkeys, OREAD);
	if(fd < 0)
		return 0;
	d = dirfstat(fd);
	if(d == nil){
		close(fd);
		return 0;
	}
	buf = malloc(d->length);
	if(buf == 0){
		close(fd);
		free(d);
		return 0;
	}
	n = readn(fd, buf, d->length);
	close(fd);
	free(d);
	if(n != d->length){
		free(buf);
		return 0;
	}

	/* decrypt */
	n -= n % KEYDBLEN;
	oldCBCdecrypt(authkey, buf, n);

	/* unpack */
	nu = 0;
	for(i = KEYDBOFF; i < n; i += KEYDBLEN){
		ep = buf + i;
		u = finduser((char*)ep);
		if(u == 0)
			u = installuser((char*)ep);
		memmove(u->key, ep + Namelen, DESKEYLEN);
		p = ep + Namelen + DESKEYLEN;
		u->status = *p++;
		u->warnings = *p++;
		if(u->status >= Smax)
			fprint(2, "keyfs: warning: bad status in key file\n");
		u->expire = p[0] + (p[1]<<8) + (p[2]<<16) + (p[3]<<24);
		p += 4;
		memmove(u->secret, p, SECRETLEN);
		u->secret[SECRETLEN-1] = 0;
		nu++;
	}
	free(buf);

	print("%d keys read\n", nu);
	return 1;
}

User *
installuser(char *name)
{
	User *u;
	int h;

	h = hash(name);
	u = emalloc(sizeof *u);
	u->name = strdup(name);
	if(u->name == nil)
		error("malloc failed: %r");
	u->removed = 0;
	u->ref = 0;
	u->purgatory = 0;
	u->expire = 0;
	u->status = Sok;
	u->bad = 0;
	u->warnings = 0;
	u->uniq = uniq++;
	u->link = users[h];
	users[h] = u;
	return u;
}

User *
finduser(char *name)
{
	User *u;

	for(u = users[hash(name)]; u; u = u->link)
		if(strcmp(name, u->name) == 0)
			return u;
	return 0;
}

int
removeuser(User *user)
{
	User *u, **last;
	char *name;

	user->removed = 1;
	name = user->name;
	last = &users[hash(name)];
	for(u = *last; u; u = *last){
		if(strcmp(name, u->name) == 0){
			*last = u->link;
			return 1;
		}
		last = &u->link;
	}
	return 0;
}

void
insertuser(User *user)
{
	int h;

	user->removed = 0;
	h = hash(user->name);
	user->link = users[h];
	users[h] = user;
}

ulong
hash(char *s)
{
	ulong h;

	h = 0;
	while(*s)
		h = (h << 1) ^ *s++;
	return h % Nuser;
}

Fid *
findfid(int fid)
{
	Fid *f, *ff;

	ff = 0;
	for(f = fids; f; f = f->next)
		if(f->fid == fid)
			return f;
		else if(!ff && !f->busy)
			ff = f;
	if(ff){
		ff->fid = fid;
		return ff;
	}
	f = emalloc(sizeof *f);
	f->fid = fid;
	f->busy = 0;
	f->user = 0;
	f->next = fids;
	fids = f;
	return f;
}

void
io(int in, int out)
{
	char *err;
	int n;
	long now, lastwarning;

	/* after restart, let the system settle for 5 mins before warning */
	lastwarning = time(0) - 24*60*60 + 5*60;

	for(;;){
		n = read9pmsg(in, mdata, messagesize);
		if(n == 0)
			continue;
		if(n < 0)
			error("mount read %d", n);
		if(convM2S(mdata, n, &rhdr) == 0)
			continue;

		if(newkeys())
			readusers();

		thdr.data = (char*)mdata + IOHDRSZ;
		thdr.fid = rhdr.fid;
		if(!fcalls[rhdr.type])
			err = "fcall request";
		else		
			err = (*fcalls[rhdr.type])(findfid(rhdr.fid));
		thdr.tag = rhdr.tag;
		thdr.type = rhdr.type+1;
		if(err){
			thdr.type = Rerror;
			thdr.ename = err;
		}
		n = convS2M(&thdr, mdata, messagesize);
		if(write(out, mdata, n) != n)
			error("mount write");

		now = time(0);
		if(warnarg && (now - lastwarning > 24*60*60)){
			syslog(0, "auth", "keyfs starting warnings: %lux %lux", now, lastwarning);
			warning();
			lastwarning = now;
		}
	}
}

int
newkeys(void)
{
	Dir *d;
	static long ftime;

	d = dirstat(userkeys);
	if(d == nil)
		return 0;
	if(d->mtime > ftime){
		ftime = d->mtime;
		free(d);
		return 1;
	}
	free(d);
	return 0;
}

void *
emalloc(ulong n)
{
	void *p;

	if(p = malloc(n))
		return p;
	error("out of memory");
	return 0;		/* not reached */
}

void
warning(void)
{
	int i;
	char buf[64];

	snprint(buf, sizeof buf, "-%s", warnarg);
	switch(rfork(RFPROC|RFNAMEG|RFNOTEG|RFNOWAIT|RFENVG|RFFDG)){
	case 0:
		i = open("/sys/log/auth", OWRITE);
		if(i >= 0){
			dup(i, 2);
			seek(2, 0, 2);
			close(i);
		}
		execl("/bin/auth/warning", "warning", warnarg, nil);
		error("can't exec warning");
	}
}