Estoy tratando de descifrar y verificar un mensaje PGP usando las bibliotecas java BouncyCastle, pero me estoy topando con problemas, quejándome de los extremos prematuros de PartialInputStream.

Sé que el cifrado funciona bien, porque puedo descifrar y verificar los mensajes creados con la función de cifrado utilizando gpg en la línea de comandos.

Aquí está el código:

public static void signEncryptMessage(InputStream in, OutputStream out, PGPPublicKey publicKey, PGPPrivateKey secretKey, SecureRandom rand) throws Exception {
        out = new ArmoredOutputStream(out);

        PGPEncryptedDataGenerator encryptedDataGenerator = new PGPEncryptedDataGenerator(new BcPGPDataEncryptorBuilder(PGPEncryptedData.AES_256).setWithIntegrityPacket(true).setSecureRandom(rand));
        encryptedDataGenerator.addMethod(new BcPublicKeyKeyEncryptionMethodGenerator(publicKey));

        OutputStream compressedOut = new PGPCompressedDataGenerator(PGPCompressedData.ZIP).open(encryptedDataGenerator.open(out, 4096), new byte[4096]);

        PGPSignatureGenerator signatureGenerator = new PGPSignatureGenerator(new BcPGPContentSignerBuilder(publicKey.getAlgorithm(), HashAlgorithmTags.SHA512));
        signatureGenerator.init(PGPSignature.BINARY_DOCUMENT, secretKey);
        signatureGenerator.generateOnePassVersion(true).encode(compressedOut);

        OutputStream finalOut = new PGPLiteralDataGenerator().open(compressedOut, PGPLiteralData.BINARY, "", new Date(), new byte[4096]);

        byte[] buf = new byte[4096];
        int len;
        while ((len = in.read(buf)) > 0) {
            finalOut.write(buf, 0, len);
            signatureGenerator.update(buf, 0, len);
        }

        finalOut.close();
        in.close();
        signatureGenerator.generate().encode(compressedOut);
        compressedOut.close();
        encryptedDataGenerator.close();
        out.close();
    }

    public static void decryptVerifyMessage(InputStream in, OutputStream out, PGPPrivateKey secretKey, PGPPublicKey publicKey) throws Exception {
        in = new ArmoredInputStream(in);

        PGPObjectFactory pgpF = new PGPObjectFactory(in);
        PGPEncryptedDataList enc = (PGPEncryptedDataList) pgpF.nextObject();

        PGPObjectFactory plainFact = new PGPObjectFactory(((PGPPublicKeyEncryptedData) enc.getEncryptedDataObjects().next()).getDataStream(new JcePublicKeyDataDecryptorFactoryBuilder().setProvider("BC").build(secretKey)));

        Object message = null;

        PGPOnePassSignatureList onePassSignatureList = null;
        PGPSignatureList signatureList = null;
        PGPCompressedData compressedData = null;

        message = plainFact.nextObject();
        ByteArrayOutputStream actualOutput = new ByteArrayOutputStream();

        while (message != null) {
            System.out.println(message.toString());
            if (message instanceof PGPCompressedData) {
                compressedData = (PGPCompressedData) message;
                plainFact = new PGPObjectFactory(compressedData.getDataStream());
                message = plainFact.nextObject();
                System.out.println(message.toString());
            }

            if (message instanceof PGPLiteralData) {
                Streams.pipeAll(((PGPLiteralData) message).getInputStream(), actualOutput);
            } else if (message instanceof PGPOnePassSignatureList) {
                onePassSignatureList = (PGPOnePassSignatureList) message;
            } else if (message instanceof PGPSignatureList) {
                signatureList = (PGPSignatureList) message;
            } else {
                throw new PGPException("message unknown message type.");
            }
            message = plainFact.nextObject();
        }
        actualOutput.close();
        byte[] output = actualOutput.toByteArray();
        if (onePassSignatureList == null || signatureList == null) {
            throw new PGPException("Poor PGP. Signatures not found.");
        } else {

            for (int i = 0; i < onePassSignatureList.size(); i++) {
                PGPOnePassSignature ops = onePassSignatureList.get(0);
                System.out.println("verifier : " + ops.getKeyID());
                if (publicKey != null) {
                    ops.init(new JcaPGPContentVerifierBuilderProvider().setProvider("BC"), publicKey);
                    ops.update(output);
                    PGPSignature signature = signatureList.get(i);
                    if (ops.verify(signature)) {
                        Iterator<?> userIds = publicKey.getUserIDs();
                        while (userIds.hasNext()) {
                            String userId = (String) userIds.next();
                            System.out.println("Signed by " + userId);
                        }
                        System.out.println("Signature verified");
                    } else {
                        throw new SignatureException("Signature verification failed");
                    }
                }
            }

        }

        out.write(output);
        out.flush();
        out.close();
    }

    public static void main(String args[]) {
        Security.insertProviderAt(new BouncyCastleProvider(), 0);
        byte inBytes[] = "The quick brown fox jumps over the lazy dog.".getBytes();

        try {
            SecureRandom rand = new SecureRandom();

            RSAKeyPairGenerator kpg = new RSAKeyPairGenerator();
            kpg.init(new RSAKeyGenerationParameters(BigInteger.valueOf(0x10001), rand, 1024, 90));

            BcPGPKeyPair sender = new BcPGPKeyPair(PGPPublicKey.RSA_GENERAL, kpg.generateKeyPair(), new Date());
            BcPGPKeyPair recip = new BcPGPKeyPair(PGPPublicKey.RSA_GENERAL, kpg.generateKeyPair(), new Date());

            ByteArrayOutputStream sendMessage = new ByteArrayOutputStream();
            ByteArrayOutputStream recvMessage = new ByteArrayOutputStream();
            signEncryptMessage(new ByteArrayInputStream(inBytes), sendMessage, recip.getPublicKey(), sender.getPrivateKey(), rand);

            System.out.println(sendMessage.toString());

            decryptVerifyMessage(new ByteArrayInputStream(sendMessage.toByteArray()), recvMessage, recip.getPrivateKey(), sender.getPublicKey());

            System.out.println(recvMessage.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Después de algunas carreras demessage = plainFact.nextObject(); se lanza la excepción:

-----BEGIN PGP MESSAGE-----
Version: BCPG v1.49
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=ApMf
-----END PGP MESSAGE-----

org.bouncycastle.openpgp.PGPCompressedData@cd36a6d
org.bouncycastle.openpgp.PGPOnePassSignatureList@7e224235
org.bouncycastle.openpgp.PGPLiteralData@7b28e644
java.io.EOFException: premature end of stream in PartialInputStream
    at org.bouncycastle.bcpg.BCPGInputStream$PartialInputStream.read(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream.read(Unknown Source)
    at java.io.InputStream.read(InputStream.java:101)
    at javax.crypto.CipherInputStream.getMoreData(CipherInputStream.java:103)
    at javax.crypto.CipherInputStream.read(CipherInputStream.java:177)
    at org.bouncycastle.bcpg.BCPGInputStream.read(Unknown Source)
    at org.bouncycastle.openpgp.PGPEncryptedData$TruncatedStream.read(Unknown Source)
    at java.io.InputStream.read(InputStream.java:170)
    at org.bouncycastle.util.io.TeeInputStream.read(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream.read(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream$PartialInputStream.read(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream.read(Unknown Source)
    at org.bouncycastle.openpgp.PGPCompressedData$1.fill(Unknown Source)
    at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:158)
    at org.bouncycastle.bcpg.BCPGInputStream.read(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream$PartialInputStream.read(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream.read(Unknown Source)
    at org.bouncycastle.util.io.Streams.readFully(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream.readFully(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream.readFully(Unknown Source)
    at org.bouncycastle.bcpg.MPInteger.<init>(Unknown Source)
    at org.bouncycastle.bcpg.SignaturePacket.<init>(Unknown Source)
    at org.bouncycastle.bcpg.BCPGInputStream.readPacket(Unknown Source)
    at org.bouncycastle.openpgp.PGPSignature.<init>(Unknown Source)
    at org.bouncycastle.openpgp.PGPObjectFactory.nextObject(Unknown Source)
    at main.decryptVerifyMessage(main.java:113)
    at main.main(main.java:167)

¿Algunas ideas?

Nota al margen, este código de descifrado vino de¿Cómo descifrar un archivo cifrado pgp firmado?, ligeramente modificado para adaptarse: los mensajes solo provendrán de ese método de encriptación y el manejo de las claves directamente en lugar de las secuencias de claves.

Aclamaciones

Ramo