authsrv.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

			continue;
		}
		break;
	}

	succeed(tr->uid);

	/*
	 *  reply with ticket & authenticator
	 */
	if(tickauthreply(tr, hkey) < 0)
		exits(0);

	if(debug){
		if(type == AuthCram)
			syslog(0, AUTHLOG, "cram-ok %s %s", tr->uid, raddr);
		else
			syslog(0, AUTHLOG, "apop-ok %s %s", tr->uid, raddr);
	}
}

enum {
	VNCchallen=	16,
};

/* VNC reverses the bits of each byte before using as a des key */
uchar swizzletab[256] = {
 0x0, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
 0x8, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
 0x4, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
 0xc, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
 0x2, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
 0xa, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
 0x6, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
 0xe, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
 0x1, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
 0x9, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
 0x5, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
 0xd, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
 0x3, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
 0xb, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
 0x7, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
 0xf, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
};

void
vnc(Ticketreq *tr)
{
	uchar chal[VNCchallen+6];
	uchar reply[VNCchallen];
	char *secret, *hkey;
	char sbuf[SECRETLEN], hbuf[DESKEYLEN];
	DESstate s;
	int i;

	/*
	 *  Create a challenge and send it.  
	 */
	randombytes(chal+6, VNCchallen);
	chal[0] = AuthOKvar;
	sprint((char*)chal+1, "%-5d", VNCchallen);
	if(write(1, chal, sizeof(chal)) != sizeof(chal))
		return;

	/*
	 *  lookup keys (and swizzle bits)
	 */
	memset(sbuf, 0, sizeof(sbuf));
	secret = findsecret(KEYDB, tr->uid, sbuf);
	if(secret == 0){
		randombytes((uchar*)sbuf, sizeof(sbuf));
		secret = sbuf;
	}
	for(i = 0; i < 8; i++)
		secret[i] = swizzletab[(uchar)secret[i]];

	hkey = findkey(KEYDB, tr->hostid, hbuf);
	if(hkey == 0){
		randombytes((uchar*)hbuf, sizeof(hbuf));
		hkey = hbuf;
	}

	/*
	 *  get response
	 */
	if(readn(0, reply, sizeof(reply)) != sizeof(reply))
		return;

	/*
	 *  decrypt response and compare
	 */
	setupDESstate(&s, (uchar*)secret, nil);
	desECBdecrypt(reply, sizeof(reply), &s);
	if(memcmp(reply, chal+6, VNCchallen) != 0){
		replyerror("vnc-fail bad response %s", raddr);
		logfail(tr->uid);
		return;
	}
	succeed(tr->uid);

	/*
	 *  reply with ticket & authenticator
	 */
	if(tickauthreply(tr, hkey) < 0)
		exits(0);

	if(debug)
		syslog(0, AUTHLOG, "vnc-ok %s %s", tr->uid, raddr);
}

void
chap(Ticketreq *tr)
{
	char *secret, *hkey;
	DigestState *s;
	char sbuf[SECRETLEN], hbuf[DESKEYLEN];
	uchar digest[MD5dlen];
	char chal[CHALLEN];
	OChapreply reply;

	/*
	 *  Create a challenge and send it.  
	 */
	randombytes((uchar*)chal, sizeof(chal));
	write(1, chal, sizeof(chal));

	/*
	 *  get chap reply
	 */
	if(readn(0, &reply, sizeof(reply)) < 0)
		exits(0);
	safecpy(tr->uid, reply.uid, sizeof(tr->uid));

	/*
	 * lookup
	 */
	secret = findsecret(KEYDB, tr->uid, sbuf);
	hkey = findkey(KEYDB, tr->hostid, hbuf);
	if(hkey == 0 || secret == 0){
		replyerror("chap-fail bad response %s", raddr);
		logfail(tr->uid);
		exits(0);
	}

	/*
	 *  check for match
	 */
	s = md5(&reply.id, 1, 0, 0);
	md5((uchar*)secret, strlen(secret), 0, s);
	md5((uchar*)chal, sizeof(chal), digest, s);

	if(memcmp(digest, reply.resp, MD5dlen) != 0){
		replyerror("chap-fail bad response %s", raddr);
		logfail(tr->uid);
		exits(0);
	}

	succeed(tr->uid);

	/*
	 *  reply with ticket & authenticator
	 */
	if(tickauthreply(tr, hkey) < 0)
		exits(0);

	if(debug)
		syslog(0, AUTHLOG, "chap-ok %s %s", tr->uid, raddr);
}

void
printresp(uchar resp[MSresplen])
{
	char buf[200], *p;
	int i;

	p = buf;
	for(i=0; i<MSresplen; i++)
		p += sprint(p, "%.2ux ", resp[i]);
	syslog(0, AUTHLOG, "resp = %s", buf);
}


void
mschap(Ticketreq *tr)
{

	char *secret, *hkey;
	char sbuf[SECRETLEN], hbuf[DESKEYLEN];
	uchar chal[CHALLEN];
	uchar hash[MShashlen];
	uchar hash2[MShashlen];
	uchar resp[MSresplen];
	OMSchapreply reply;
	int lmok, ntok;
	DigestState *s;
	uchar digest[SHA1dlen];

	/*
	 *  Create a challenge and send it.  
	 */
	randombytes((uchar*)chal, sizeof(chal));
	write(1, chal, sizeof(chal));

	/*
	 *  get chap reply
	 */
	if(readn(0, &reply, sizeof(reply)) < 0)
		exits(0);
	
	safecpy(tr->uid, reply.uid, sizeof(tr->uid));
	/*
	 * lookup
	 */
	secret = findsecret(KEYDB, tr->uid, sbuf);
	hkey = findkey(KEYDB, tr->hostid, hbuf);
	if(hkey == 0 || secret == 0){
		replyerror("mschap-fail bad response %s", raddr);
		logfail(tr->uid);
		exits(0);
	}

	/*
	 *  check for match on LM algorithm
	 */
	lmhash(hash, secret);
	mschalresp(resp, hash, chal);
	lmok = memcmp(resp, reply.LMresp, MSresplen) == 0;

	nthash(hash, secret);
	mschalresp(resp, hash, chal);
	ntok = memcmp(resp, reply.NTresp, MSresplen) == 0;

	if(!ntok){
		replyerror("mschap-fail bad response %s %ux", raddr, (lmok<<1)|ntok);
		logfail(tr->uid);
		exits(0);
	}

	succeed(tr->uid);

	/*
	 *  reply with ticket & authenticator
	 */
	if(tickauthreply(tr, hkey) < 0)
		exits(0);

	if(debug)
		syslog(0, AUTHLOG, "mschap-ok %s %s %ux", tr->uid, raddr, (lmok<<1)|ntok);

	nthash(hash, secret);
	md4(hash, 16, hash2, 0);
	s = sha1(hash2, 16, 0, 0);
	sha1(hash2, 16, 0, s);
	sha1(chal, 8, digest, s);

	if(write(1, digest, 16) < 0)
		exits(0);
}

void
nthash(uchar hash[MShashlen], char *passwd)
{
	uchar buf[512];
	int i;
	
	for (i = 0; *passwd && i + 1 < sizeof(buf);) {
		Rune r;
		passwd += chartorune(&r, passwd);
		buf[i++] = r;
		buf[i++] = r >> 8;
	}

	memset(hash, 0, 16);

	md4(buf, i, hash, 0);
}

void
lmhash(uchar hash[MShashlen], char *passwd)
{
	uchar buf[14];
	char *stdtext = "KGS!@#$%";
	int i;

	strncpy((char*)buf, passwd, sizeof(buf));
	for(i=0; i<sizeof(buf); i++)
		if(buf[i] >= 'a' && buf[i] <= 'z')
			buf[i] += 'A' - 'a';

	memset(hash, 0, 16);
	memcpy(hash, stdtext, 8);
	memcpy(hash+8, stdtext, 8);

	desencrypt(hash, buf);
	desencrypt(hash+8, buf+7);
}

void
mschalresp(uchar resp[MSresplen], uchar hash[MShashlen], uchar chal[MSchallen])
{
	int i;
	uchar buf[21];
	
	memset(buf, 0, sizeof(buf));
	memcpy(buf, hash, MShashlen);

	for(i=0; i<3; i++) {
		memmove(resp+i*MSchallen, chal, MSchallen);
		desencrypt(resp+i*MSchallen, buf+i*7);
	}
}

void
desencrypt(uchar data[8], uchar key[7])
{
	ulong ekey[32];

	key_setup(key, ekey);
	block_cipher(ekey, data, 0);
}

/*
 *  return true of the speaker may speak for the user
 *
 *  a speaker may always speak for himself/herself
 */
int
speaksfor(char *speaker, char *user)
{
	Ndbtuple *tp, *ntp;
	Ndbs s;
	int ok;
	char notuser[Maxpath];
	
	if(strcmp(speaker, user) == 0)
		return 1;

	if(db == 0)
		return 0;
	
	tp = ndbsearch(db, &s, "hostid", speaker);
	if(tp == 0)
		return 0;

	ok = 0;
	snprint(notuser, sizeof notuser, "!%s", user);
	for(ntp = tp; ntp; ntp = ntp->entry)
		if(strcmp(ntp->attr, "uid") == 0){
			if(strcmp(ntp->val, notuser) == 0)
				break;
			if(*ntp->val == '*' || strcmp(ntp->val, user) == 0)
				ok = 1;
		}
	ndbfree(tp);
	return ok;
}

/*
 *  return an error reply
 */
void
replyerror(char *fmt, ...)
{
	char buf[AERRLEN+1];
	va_list arg;

	memset(buf, 0, sizeof(buf));
	va_start(arg, fmt);
	vseprint(buf + 1, buf + sizeof(buf), fmt, arg);
	va_end(arg);
	buf[AERRLEN] = 0;
	buf[0] = AuthErr;
	write(1, buf, AERRLEN+1);
	syslog(0, AUTHLOG, buf+1);
}

void
getraddr(char *dir)
{
	int n;
	char *cp;
	char file[Maxpath];

	raddr[0] = 0;
	snprint(file, sizeof(file), "%s/remote", dir);
	n = readfile(file, raddr, sizeof(raddr)-1);
	if(n < 0)
		return;
	raddr[n] = 0;

	cp = strchr(raddr, '\n');
	if(cp)
		*cp = 0;
	cp = strchr(raddr, '!');
	if(cp)
		*cp = 0;
}

void
mkkey(char *k)
{
	randombytes((uchar*)k, DESKEYLEN);
}

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

	if(readfile("/dev/random", (char*)buf, len) >= 0)
		return;

	for(i = 0; i < len; i++)
		buf[i] = rand();
}

/*
 *  reply with ticket and authenticator
 */
int
tickauthreply(Ticketreq *tr, char *hkey)
{
	Ticket t;
	Authenticator a;
	char buf[TICKETLEN+AUTHENTLEN+1];

	memset(&t, 0, sizeof(t));
	memmove(t.chal, tr->chal, CHALLEN);
	safecpy(t.cuid, tr->uid, sizeof t.cuid);
	safecpy(t.suid, tr->uid, sizeof t.suid);
	mkkey(t.key);
	buf[0] = AuthOK;
	t.num = AuthTs;
	convT2M(&t, buf+1, hkey);
	memmove(a.chal, t.chal, CHALLEN);
	a.num = AuthAc;
	a.id = 0;
	convA2M(&a, buf+TICKETLEN+1, t.key);
	if(write(1, buf, TICKETLEN+AUTHENTLEN+1) < 0)
		return -1;
	return 0;
}

void
safecpy(char *to, char *from, int len)
{
	strncpy(to, from, len);
	to[len-1] = 0;
}