esp.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

		ecb->header = 1;
	else if(strcmp(f[0], "noheader") == 0)
		ecb->header = 0;
	else
		e = "unknown control request";
	return e;
}

void
espadvise(Proto *esp, Block *bp, char *msg)
{
	Esphdr *h;
	Conv *c;
	ulong spi;

	h = (Esphdr*)(bp->rp);

	spi = nhgets(h->espspi);
	qlock(esp);
	c = convlookup(esp, spi);
	if(c != nil) {
		qhangup(c->rq, msg);
		qhangup(c->wq, msg);
	}
	qunlock(esp);
	freeblist(bp);
}

int
espstats(Proto *esp, char *buf, int len)
{
	Esppriv *upriv;

	upriv = esp->priv;
	return snprint(buf, len, "%lud %lud\n",
		upriv->in,
		upriv->inerrors);
}

static int
esplocal(Conv *c, char *buf, int len)
{
	Espcb *ecb = c->ptcl;
	int n;

	qlock(c);
	if(ecb->incoming)
		n = snprint(buf, len, "%I!%uld\n", c->laddr, ecb->spi);
	else
		n = snprint(buf, len, "%I\n", c->laddr);
	qunlock(c);
	return n;
}

static int
espremote(Conv *c, char *buf, int len)
{
	Espcb *ecb = c->ptcl;
	int n;

	qlock(c);
	if(ecb->incoming)
		n = snprint(buf, len, "%I\n", c->raddr);
	else
		n = snprint(buf, len, "%I!%uld\n", c->raddr, ecb->spi);
	qunlock(c);
	return n;
}

static	Conv*
convlookup(Proto *esp, ulong spi)
{
	Conv *c, **p;
	Espcb *ecb;

	for(p=esp->conv; *p; p++){
		c = *p;
		ecb = c->ptcl;
		if(ecb->incoming && ecb->spi == spi)
			return c;
	}
	return nil;
}

static char *
setalg(Espcb *ecb, char **f, int n, Algorithm *alg)
{
	uchar *key;
	int i, nbyte, nchar;
	int c;

	if(n < 2)
		return "bad format";
	for(; alg->name; alg++)
		if(strcmp(f[1], alg->name) == 0)
			break;
	if(alg->name == nil)
		return "unknown algorithm";

	if(n != 3)
		return "bad format";
	nbyte = (alg->keylen + 7) >> 3;
	nchar = strlen(f[2]);
	for(i=0; i<nchar; i++) {
		c = f[2][i];
		if(c >= '0' && c <= '9')
			f[2][i] -= '0';
		else if(c >= 'a' && c <= 'f')
			f[2][i] -= 'a'-10;
		else if(c >= 'A' && c <= 'F')
			f[2][i] -= 'A'-10;
		else
			return "bad character in key";
	}
	key = smalloc(nbyte);
	for(i=0; i<nchar && i*2<nbyte; i++) {
		c = f[2][nchar-i-1];
		if(i&1)
			c <<= 4;
		key[i>>1] |= c;
	}

	alg->init(ecb, alg->name, key, alg->keylen);
	free(key);
	return nil;
}

static int
nullcipher(Espcb*, uchar*, int)
{
	return 1;
}

static void
nullespinit(Espcb *ecb, char *name, uchar*, int)
{
	ecb->espalg = name;
	ecb->espblklen = 1;
	ecb->espivlen = 0;
	ecb->cipher = nullcipher;
}

static int
nullauth(Espcb*, uchar*, int, uchar*)
{
	return 1;
}

static void
nullahinit(Espcb *ecb, char *name, uchar*, int)
{
	ecb->ahalg = name;
	ecb->ahblklen = 1;
	ecb->ahlen = 0;
	ecb->auth = nullauth;
}

void
seanq_hmac_sha1(uchar hash[SHA1dlen], uchar *t, long tlen, uchar *key, long klen)
{
	uchar ipad[65], opad[65];
	int i;
	DigestState *digest;
	uchar innerhash[SHA1dlen];

	for(i=0; i<64; i++){
		ipad[i] = 0x36;
		opad[i] = 0x5c;
	}
	ipad[64] = opad[64] = 0;
	for(i=0; i<klen; i++){
		ipad[i] ^= key[i];
		opad[i] ^= key[i];
	}
	digest = sha1(ipad, 64, nil, nil);
	sha1(t, tlen, innerhash, digest);
	digest = sha1(opad, 64, nil, nil);
	sha1(innerhash, SHA1dlen, hash, digest);
}

static int
shaauth(Espcb *ecb, uchar *t, int tlen, uchar *auth)
{
	uchar hash[SHA1dlen];
	int r;

	memset(hash, 0, SHA1dlen);
	seanq_hmac_sha1(hash, t, tlen, (uchar*)ecb->ahstate, 16);
	r = memcmp(auth, hash, ecb->ahlen) == 0;
	memmove(auth, hash, ecb->ahlen);
	return r;
}

static void
shaahinit(Espcb *ecb, char *name, uchar *key, int klen)
{
	if(klen != 128)
		panic("shaahinit: bad keylen");
	klen >>= 8;	// convert to bytes

	ecb->ahalg = name;
	ecb->ahblklen = 1;
	ecb->ahlen = 12;
	ecb->auth = shaauth;
	ecb->ahstate = smalloc(klen);
	memmove(ecb->ahstate, key, klen);
}

void
seanq_hmac_md5(uchar hash[MD5dlen], uchar *t, long tlen, uchar *key, long klen)
{
	uchar ipad[65], opad[65];
	int i;
	DigestState *digest;
	uchar innerhash[MD5dlen];

	for(i=0; i<64; i++){
		ipad[i] = 0x36;
		opad[i] = 0x5c;
	}
	ipad[64] = opad[64] = 0;
	for(i=0; i<klen; i++){
		ipad[i] ^= key[i];
		opad[i] ^= key[i];
	}
	digest = md5(ipad, 64, nil, nil);
	md5(t, tlen, innerhash, digest);
	digest = md5(opad, 64, nil, nil);
	md5(innerhash, MD5dlen, hash, digest);
}

static int
md5auth(Espcb *ecb, uchar *t, int tlen, uchar *auth)
{
	uchar hash[MD5dlen];
	int r;

	memset(hash, 0, MD5dlen);
	seanq_hmac_md5(hash, t, tlen, (uchar*)ecb->ahstate, 16);
	r = memcmp(auth, hash, ecb->ahlen) == 0;
	memmove(auth, hash, ecb->ahlen);
	return r;
}

static void
md5ahinit(Espcb *ecb, char *name, uchar *key, int klen)
{
	if(klen != 128)
		panic("md5ahinit: bad keylen");
	klen >>= 3;	// convert to bytes


	ecb->ahalg = name;
	ecb->ahblklen = 1;
	ecb->ahlen = 12;
	ecb->auth = md5auth;
	ecb->ahstate = smalloc(klen);
	memmove(ecb->ahstate, key, klen);
}

static int
descipher(Espcb *ecb, uchar *p, int n)
{
	uchar tmp[8];
	uchar *pp, *tp, *ip, *eip, *ep;
	DESstate *ds = ecb->espstate;

	ep = p + n;
	if(ecb->incoming) {
		memmove(ds->ivec, p, 8);
		p += 8;
		while(p < ep){
			memmove(tmp, p, 8);
			block_cipher(ds->expanded, p, 1);
			tp = tmp;
			ip = ds->ivec;
			for(eip = ip+8; ip < eip; ){
				*p++ ^= *ip;
				*ip++ = *tp++;
			}
		}
	} else {
		memmove(p, ds->ivec, 8);
		for(p += 8; p < ep; p += 8){
			pp = p;
			ip = ds->ivec;
			for(eip = ip+8; ip < eip; )
				*pp++ ^= *ip++;
			block_cipher(ds->expanded, p, 0);
			memmove(ds->ivec, p, 8);
		}
	}
	return 1;
}
	
static void
desespinit(Espcb *ecb, char *name, uchar *k, int n)
{
	uchar key[8];
	uchar ivec[8];
	int i;
	
	// bits to bytes
	n = (n+7)>>3;
	if(n > 8)
		n = 8;
	memset(key, 0, sizeof(key));
	memmove(key, k, n);
	for(i=0; i<8; i++)
		ivec[i] = nrand(256);
	ecb->espalg = name;
	ecb->espblklen = 8;
	ecb->espivlen = 8;
	ecb->cipher = descipher;
	ecb->espstate = smalloc(sizeof(DESstate));
	setupDESstate(ecb->espstate, key, ivec);
}

static int
rc4cipher(Espcb *ecb, uchar *p, int n)
{
	Esprc4 *esprc4;
	RC4state tmpstate;
	ulong seq;
	long d, dd;

	if(n < 4)
		return 0;

	esprc4 = ecb->espstate;
	if(ecb->incoming) {
		seq = nhgetl(p);
		p += 4;
		n -= 4;
		d = seq-esprc4->cseq;
		if(d == 0) {
			rc4(&esprc4->current, p, n);
			esprc4->cseq += n;
			if(esprc4->ovalid) {
				dd = esprc4->cseq - esprc4->lgseq;
				if(dd > RC4back)
					esprc4->ovalid = 0;
			}
		} else if(d > 0) {
print("missing packet: %uld %ld\n", seq, d);
			// this link is hosed
			if(d > RC4forward) {
				strcpy(up->errstr, "rc4cipher: skipped too much");
				return 0;
			}
			esprc4->lgseq = seq;
			if(!esprc4->ovalid) {
				esprc4->ovalid = 1;
				esprc4->oseq = esprc4->cseq;
				memmove(&esprc4->old, &esprc4->current, sizeof(RC4state));
			}
			rc4skip(&esprc4->current, d);
			rc4(&esprc4->current, p, n);
			esprc4->cseq = seq+n;
		} else {
print("reordered packet: %uld %ld\n", seq, d);
			dd = seq - esprc4->oseq;
			if(!esprc4->ovalid || -d > RC4back || dd < 0) {
				strcpy(up->errstr, "rc4cipher: too far back");
				return 0;
			}
			memmove(&tmpstate, &esprc4->old, sizeof(RC4state));
			rc4skip(&tmpstate, dd);
			rc4(&tmpstate, p, n);
			return 1;
		}

		// move old state up
		if(esprc4->ovalid) {
			dd = esprc4->cseq - RC4back - esprc4->oseq;
			if(dd > 0) {
				rc4skip(&esprc4->old, dd);
				esprc4->oseq += dd;
			}
		}
	} else {
		hnputl(p, esprc4->cseq);
		p += 4;
		n -= 4;
		rc4(&esprc4->current, p, n);
		esprc4->cseq += n;
	}
	return 1;
}

static void
rc4espinit(Espcb *ecb, char *name, uchar *k, int n)
{	
	Esprc4 *esprc4;

	// bits to bytes
	n = (n+7)>>3;
	esprc4 = smalloc(sizeof(Esprc4));
	memset(esprc4, 0, sizeof(Esprc4));
	setupRC4state(&esprc4->current, k, n);
	ecb->espalg = name;
	ecb->espblklen = 4;
	ecb->espivlen = 4;
	ecb->cipher = rc4cipher;
	ecb->espstate = esprc4;
}
	
void
espinit(Fs *fs)
{
	Proto *esp;

	esp = smalloc(sizeof(Proto));
	esp->priv = smalloc(sizeof(Esppriv));
	esp->name = "esp";
	esp->connect = espconnect;
	esp->announce = nil;
	esp->ctl = espctl;
	esp->state = espstate;
	esp->create = espcreate;
	esp->close = espclose;
	esp->rcv = espiput;
	esp->advise = espadvise;
	esp->stats = espstats;
	esp->local = esplocal;
	esp->remote = espremote;
	esp->ipproto = IP_ESPPROTO;
	esp->nc = Nchans;
	esp->ptclsize = sizeof(Espcb);

	Fsproto(fs, esp);
}