/**
* Sign the provided payment request.
*
* @param paymentRequest Payment request to sign, in its builder form.
* @param certificateChain Certificate chain to send with the payment request, ordered from client
* certificate to root certificate. The root certificate itself may be omitted.
* @param privateKey The key to sign with. Must match the public key from the first certificate of
* the certificate chain.
*/
public static void signPaymentRequest(
Protos.PaymentRequest.Builder paymentRequest,
X509Certificate[] certificateChain,
PrivateKey privateKey) {
try {
final Protos.X509Certificates.Builder certificates = Protos.X509Certificates.newBuilder();
for (final Certificate certificate : certificateChain)
certificates.addCertificate(ByteString.copyFrom(certificate.getEncoded()));
paymentRequest.setPkiType("x509+sha256");
paymentRequest.setPkiData(certificates.build().toByteString());
paymentRequest.setSignature(ByteString.EMPTY);
final Protos.PaymentRequest paymentRequestToSign = paymentRequest.build();
final String algorithm;
if ("RSA".equalsIgnoreCase(privateKey.getAlgorithm())) algorithm = "SHA256withRSA";
else throw new IllegalStateException(privateKey.getAlgorithm());
final Signature signature = Signature.getInstance(algorithm);
signature.initSign(privateKey);
signature.update(paymentRequestToSign.toByteArray());
paymentRequest.setSignature(ByteString.copyFrom(signature.sign()));
} catch (final GeneralSecurityException x) {
// Should never happen so don't make users have to think about it.
throw new RuntimeException(x);
}
}
/**
* Uses the provided PKI method to find the corresponding public key and verify the provided
* signature.
*
* @param paymentRequest Payment request to verify.
* @param trustStore KeyStore of trusted root certificate authorities.
* @return verification data, or null if no PKI method was specified in the {@link
* Protos.PaymentRequest}.
* @throws PaymentProtocolException if payment request could not be verified.
*/
@Nullable
public static PkiVerificationData verifyPaymentRequestPki(
Protos.PaymentRequest paymentRequest, KeyStore trustStore) throws PaymentProtocolException {
List<X509Certificate> certs = null;
try {
final String pkiType = paymentRequest.getPkiType();
if ("none".equals(pkiType))
// Nothing to verify. Everything is fine. Move along.
return null;
String algorithm;
if ("x509+sha256".equals(pkiType)) algorithm = "SHA256withRSA";
else if ("x509+sha1".equals(pkiType)) algorithm = "SHA1withRSA";
else throw new PaymentProtocolException.InvalidPkiType("Unsupported PKI type: " + pkiType);
Protos.X509Certificates protoCerts =
Protos.X509Certificates.parseFrom(paymentRequest.getPkiData());
if (protoCerts.getCertificateCount() == 0)
throw new PaymentProtocolException.InvalidPkiData(
"No certificates provided in message: server config error");
// Parse the certs and turn into a certificate chain object. Cert factories can parse both DER
// and base64.
// The ordering of certificates is defined by the payment protocol spec to be the same as what
// the Java
// crypto API requires - convenient!
CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
certs = Lists.newArrayList();
for (ByteString bytes : protoCerts.getCertificateList())
certs.add((X509Certificate) certificateFactory.generateCertificate(bytes.newInput()));
CertPath path = certificateFactory.generateCertPath(certs);
// Retrieves the most-trusted CAs from keystore.
PKIXParameters params = new PKIXParameters(trustStore);
// Revocation not supported in the current version.
params.setRevocationEnabled(false);
// Now verify the certificate chain is correct and trusted. This let's us get an identity
// linked pubkey.
CertPathValidator validator = CertPathValidator.getInstance("PKIX");
PKIXCertPathValidatorResult result =
(PKIXCertPathValidatorResult) validator.validate(path, params);
PublicKey publicKey = result.getPublicKey();
// OK, we got an identity, now check it was used to sign this message.
Signature signature = Signature.getInstance(algorithm);
// Note that we don't use signature.initVerify(certs.get(0)) here despite it being the most
// obvious
// way to set it up, because we don't care about the constraints specified on the
// certificates: any
// cert that links a key to a domain name or other identity will do for us.
signature.initVerify(publicKey);
Protos.PaymentRequest.Builder reqToCheck = paymentRequest.toBuilder();
reqToCheck.setSignature(ByteString.EMPTY);
signature.update(reqToCheck.build().toByteArray());
if (!signature.verify(paymentRequest.getSignature().toByteArray()))
throw new PaymentProtocolException.PkiVerificationException(
"Invalid signature, this payment request is not valid.");
// Signature verifies, get the names from the identity we just verified for presentation to
// the user.
final X509Certificate cert = certs.get(0);
String displayName = X509Utils.getDisplayNameFromCertificate(cert, true);
if (displayName == null)
throw new PaymentProtocolException.PkiVerificationException(
"Could not extract name from certificate");
// Everything is peachy. Return some useful data to the caller.
return new PkiVerificationData(displayName, publicKey, result.getTrustAnchor());
} catch (InvalidProtocolBufferException e) {
// Data structures are malformed.
throw new PaymentProtocolException.InvalidPkiData(e);
} catch (CertificateException e) {
// The X.509 certificate data didn't parse correctly.
throw new PaymentProtocolException.PkiVerificationException(e);
} catch (NoSuchAlgorithmException e) {
// Should never happen so don't make users have to think about it. PKIX is always present.
throw new RuntimeException(e);
} catch (InvalidAlgorithmParameterException e) {
throw new RuntimeException(e);
} catch (CertPathValidatorException e) {
// The certificate chain isn't known or trusted, probably, the server is using an SSL root we
// don't
// know about and the user needs to upgrade to a new version of the software (or import a root
// cert).
throw new PaymentProtocolException.PkiVerificationException(e, certs);
} catch (InvalidKeyException e) {
// Shouldn't happen if the certs verified correctly.
throw new PaymentProtocolException.PkiVerificationException(e);
} catch (SignatureException e) {
// Something went wrong during hashing (yes, despite the name, this does not mean the sig was
// invalid).
throw new PaymentProtocolException.PkiVerificationException(e);
} catch (KeyStoreException e) {
throw new RuntimeException(e);
}
}
