Beispiel #1
0
func (client *clientImpl) getTCertsFromTCA(num int) ([][]byte, error) {
	client.node.log.Debug("Get [%d] certificates from the TCA...", num)

	// Contact the TCA
	TCertOwnerKDFKey, certDERs, err := client.callTCACreateCertificateSet(num)
	if err != nil {
		client.node.log.Debug("Failed contacting TCA [%s].", err.Error())

		return nil, err
	}

	//	client.node.log.Debug("TCertOwnerKDFKey [%s].", utils.EncodeBase64(TCertOwnerKDFKey))

	// Store TCertOwnerKDFKey and checks that every time it is always the same key
	if client.tCertOwnerKDFKey != nil {
		// Check that the keys are the same
		equal := bytes.Equal(client.tCertOwnerKDFKey, TCertOwnerKDFKey)
		if !equal {
			return nil, errors.New("Failed reciving kdf key from TCA. The keys are different.")
		}
	} else {
		client.tCertOwnerKDFKey = TCertOwnerKDFKey

		// TODO: handle this situation more carefully
		if err := client.storeTCertOwnerKDFKey(); err != nil {
			client.node.log.Error("Failed storing TCertOwnerKDFKey [%s].", err.Error())

			return nil, err
		}
	}

	// Validate the Certificates obtained

	TCertOwnerEncryptKey := utils.HMACTruncated(TCertOwnerKDFKey, []byte{1}, utils.AESKeyLength)
	ExpansionKey := utils.HMAC(TCertOwnerKDFKey, []byte{2})

	resCert := make([][]byte, num)

	j := 0
	for i := 0; i < num; i++ {
		client.node.log.Debug("Validating certificate [%d], [%s]", i, utils.EncodeBase64(certDERs[i]))

		// DER to x509
		x509Cert, err := utils.DERToX509Certificate(certDERs[i])
		if err != nil {
			client.node.log.Debug("Failed parsing certificate: [%s].", err)

			continue
		}

		// Handle Critical Extenstion TCertEncTCertIndex
		tCertIndexCT, err := utils.GetCriticalExtension(x509Cert, utils.TCertEncTCertIndex)
		if err != nil {
			client.node.log.Error("Failed getting extension TCERT_ENC_TCERTINDEX [%s].", err.Error())

			continue
		}

		// Verify certificate against root
		if _, err := utils.CheckCertAgainRoot(x509Cert, client.node.tcaCertPool); err != nil {
			client.node.log.Warning("Warning verifing certificate [%s].", err.Error())

			continue
		}

		// Verify public key

		// 384-bit ExpansionValue = HMAC(Expansion_Key, TCertIndex)
		// Let TCertIndex = Timestamp, RandValue, 1,2,…
		// Timestamp assigned, RandValue assigned and counter reinitialized to 1 per batch

		// Decrypt ct to TCertIndex (TODO: || EnrollPub_Key || EnrollID ?)
		pt, err := utils.CBCPKCS7Decrypt(TCertOwnerEncryptKey, tCertIndexCT)
		if err != nil {
			client.node.log.Error("Failed decrypting extension TCERT_ENC_TCERTINDEX [%s].", err.Error())

			continue
		}

		// Compute ExpansionValue based on TCertIndex
		TCertIndex := pt
		//		TCertIndex := []byte(strconv.Itoa(i))

		client.node.log.Debug("TCertIndex: [%s].", utils.EncodeBase64(TCertIndex))
		mac := hmac.New(utils.NewHash, ExpansionKey)
		mac.Write(TCertIndex)
		ExpansionValue := mac.Sum(nil)

		// Derive tpk and tsk accordingly to ExapansionValue from enrollment pk,sk
		// Computable by TCA / Auditor: TCertPub_Key = EnrollPub_Key + ExpansionValue G
		// using elliptic curve point addition per NIST FIPS PUB 186-4- specified P-384

		// Compute temporary secret key
		tempSK := &ecdsa.PrivateKey{
			PublicKey: ecdsa.PublicKey{
				Curve: client.node.enrollPrivKey.Curve,
				X:     new(big.Int),
				Y:     new(big.Int),
			},
			D: new(big.Int),
		}

		var k = new(big.Int).SetBytes(ExpansionValue)
		var one = new(big.Int).SetInt64(1)
		n := new(big.Int).Sub(client.node.enrollPrivKey.Params().N, one)
		k.Mod(k, n)
		k.Add(k, one)

		tempSK.D.Add(client.node.enrollPrivKey.D, k)
		tempSK.D.Mod(tempSK.D, client.node.enrollPrivKey.PublicKey.Params().N)

		// Compute temporary public key
		tempX, tempY := client.node.enrollPrivKey.PublicKey.ScalarBaseMult(k.Bytes())
		tempSK.PublicKey.X, tempSK.PublicKey.Y =
			tempSK.PublicKey.Add(
				client.node.enrollPrivKey.PublicKey.X, client.node.enrollPrivKey.PublicKey.Y,
				tempX, tempY,
			)

		// Verify temporary public key is a valid point on the reference curve
		isOn := tempSK.Curve.IsOnCurve(tempSK.PublicKey.X, tempSK.PublicKey.Y)
		if !isOn {
			client.node.log.Error("Failed temporary public key IsOnCurve check.")

			continue
		}

		// Check that the derived public key is the same as the one in the certificate
		certPK := x509Cert.PublicKey.(*ecdsa.PublicKey)

		cmp := certPK.X.Cmp(tempSK.PublicKey.X)
		if cmp != 0 {
			client.node.log.Error("Derived public key is different on X")

			continue
		}

		cmp = certPK.Y.Cmp(tempSK.PublicKey.Y)
		if cmp != 0 {
			client.node.log.Error("Derived public key is different on Y")

			continue
		}

		// Verify the signing capability of tempSK
		err = utils.VerifySignCapability(tempSK, x509Cert.PublicKey)
		if err != nil {
			client.node.log.Error("Failed verifing signing capability [%s].", err.Error())

			continue
		}

		// Marshall certificate and secret key to be stored in the database
		resCert[j] = certDERs[i]
		if err != nil {
			client.node.log.Error("Failed marshalling private key [%s].", err.Error())

			continue
		}

		if err := utils.CheckCertPKAgainstSK(x509Cert, interface{}(tempSK)); err != nil {
			client.node.log.Error("Failed checking TCA cert PK against private key [%s].", err.Error())

			continue
		}

		client.node.log.Debug("Sub index [%d]", j)
		j++
		client.node.log.Debug("Certificate [%d] validated.", i)
	}

	if j == 0 {
		client.node.log.Error("No valid TCert was sent")

		return nil, errors.New("No valid TCert was sent.")
	}

	return resCert[:j], nil
}
Beispiel #2
0
func (client *clientImpl) getTCertFromDER(der []byte) (tCert tCert, err error) {
	if client.tCertOwnerKDFKey == nil {
		return nil, fmt.Errorf("KDF key not initialized yet")
	}

	TCertOwnerEncryptKey := utils.HMACTruncated(client.tCertOwnerKDFKey, []byte{1}, utils.AESKeyLength)
	ExpansionKey := utils.HMAC(client.tCertOwnerKDFKey, []byte{2})

	// DER to x509
	x509Cert, err := utils.DERToX509Certificate(der)
	if err != nil {
		client.debug("Failed parsing certificate [% x]: [%s].", der, err)

		return
	}

	// Handle Critical Extenstion TCertEncTCertIndex
	tCertIndexCT, err := utils.GetCriticalExtension(x509Cert, utils.TCertEncTCertIndex)
	if err != nil {
		client.error("Failed getting extension TCERT_ENC_TCERTINDEX [%s].", err.Error())

		return
	}

	// Verify certificate against root
	if _, err = utils.CheckCertAgainRoot(x509Cert, client.tcaCertPool); err != nil {
		client.warning("Warning verifing certificate [%s].", err.Error())

		return
	}

	// Verify public key

	// 384-bit ExpansionValue = HMAC(Expansion_Key, TCertIndex)
	// Let TCertIndex = Timestamp, RandValue, 1,2,…
	// Timestamp assigned, RandValue assigned and counter reinitialized to 1 per batch

	// Decrypt ct to TCertIndex (TODO: || EnrollPub_Key || EnrollID ?)
	pt, err := utils.CBCPKCS7Decrypt(TCertOwnerEncryptKey, tCertIndexCT)
	if err != nil {
		client.error("Failed decrypting extension TCERT_ENC_TCERTINDEX [%s].", err.Error())

		return
	}

	// Compute ExpansionValue based on TCertIndex
	TCertIndex := pt
	//		TCertIndex := []byte(strconv.Itoa(i))

	client.debug("TCertIndex: [% x].", TCertIndex)
	mac := hmac.New(utils.NewHash, ExpansionKey)
	mac.Write(TCertIndex)
	ExpansionValue := mac.Sum(nil)

	// Derive tpk and tsk accordingly to ExapansionValue from enrollment pk,sk
	// Computable by TCA / Auditor: TCertPub_Key = EnrollPub_Key + ExpansionValue G
	// using elliptic curve point addition per NIST FIPS PUB 186-4- specified P-384

	// Compute temporary secret key
	tempSK := &ecdsa.PrivateKey{
		PublicKey: ecdsa.PublicKey{
			Curve: client.enrollPrivKey.Curve,
			X:     new(big.Int),
			Y:     new(big.Int),
		},
		D: new(big.Int),
	}

	var k = new(big.Int).SetBytes(ExpansionValue)
	var one = new(big.Int).SetInt64(1)
	n := new(big.Int).Sub(client.enrollPrivKey.Params().N, one)
	k.Mod(k, n)
	k.Add(k, one)

	tempSK.D.Add(client.enrollPrivKey.D, k)
	tempSK.D.Mod(tempSK.D, client.enrollPrivKey.PublicKey.Params().N)

	// Compute temporary public key
	tempX, tempY := client.enrollPrivKey.PublicKey.ScalarBaseMult(k.Bytes())
	tempSK.PublicKey.X, tempSK.PublicKey.Y =
		tempSK.PublicKey.Add(
			client.enrollPrivKey.PublicKey.X, client.enrollPrivKey.PublicKey.Y,
			tempX, tempY,
		)

	// Verify temporary public key is a valid point on the reference curve
	isOn := tempSK.Curve.IsOnCurve(tempSK.PublicKey.X, tempSK.PublicKey.Y)
	if !isOn {
		client.error("Failed temporary public key IsOnCurve check.")

		return nil, fmt.Errorf("Failed temporary public key IsOnCurve check.")
	}

	// Check that the derived public key is the same as the one in the certificate
	certPK := x509Cert.PublicKey.(*ecdsa.PublicKey)

	if certPK.X.Cmp(tempSK.PublicKey.X) != 0 {
		client.error("Derived public key is different on X")

		return nil, fmt.Errorf("Derived public key is different on X")
	}

	if certPK.Y.Cmp(tempSK.PublicKey.Y) != 0 {
		client.error("Derived public key is different on Y")

		return nil, fmt.Errorf("Derived public key is different on Y")
	}

	// Verify the signing capability of tempSK
	err = utils.VerifySignCapability(tempSK, x509Cert.PublicKey)
	if err != nil {
		client.error("Failed verifing signing capability [%s].", err.Error())

		return
	}

	// Marshall certificate and secret key to be stored in the database
	if err != nil {
		client.error("Failed marshalling private key [%s].", err.Error())

		return
	}

	if err = utils.CheckCertPKAgainstSK(x509Cert, interface{}(tempSK)); err != nil {
		client.error("Failed checking TCA cert PK against private key [%s].", err.Error())

		return
	}

	tCert = &tCertImpl{client, x509Cert, tempSK}

	return
}