让 BouncyCastle 解密 GPG 加密的消息

Question

如何让 BouncyCastle 解密 GPG 加密的消息？

我在 CentOS 7 命令行中使用 gpg --gen-key 创建了 GPG 密钥对。我选择 RSA RSA 作为加密类型，并使用gpg --export-secret-key -a "User Name" > /home/username/username_private.key 和gpg --armor --export 66677FC6 > /home/username/username_pubkey.asc 导出密钥

我能够将username_pubkey.asc 导入另一个电子邮件帐户的远程Thunderbird 客户端，并成功将加密电子邮件发送到username@mydomain.com。但是当我在 mydomain.com 上运行的 Java/BouncyCastle 代码尝试解密 GPG 编码的数据时，会出现以下错误：

org.bouncycastle.openpgp.PGPException:  
Encrypted message contains a signed message - not literal data.

如果您查看下面的代码，您会看到这与 PGPUtils.decryptFile() 中声明 else if (message instanceof PGPOnePassSignatureList) {throw new PGPException("Encrypted message contains a signed message - not literal data."); 的行相对应

原始代码来自the blog entry at this link，尽管我做了一些小改动以使其在 Eclipse Luna 中使用 Java 7 进行编译。链接博客的用户报告了同样的错误，博客作者回复说它不适用于 GPG。 那么我该如何解决这个问题以使其与 GPG 一起使用？

当 GPG-encoded-file 和 GPG-secret-key 传入Tester.testDecrypt() 时，Java 解密代码开始，如下所示：

Tester.java 包含：

public InputStream testDecrypt(String input, String output, String passphrase, String skeyfile) throws Exception {
    PGPFileProcessor p = new PGPFileProcessor();
    p.setInputFileName(input);//this is GPG-encoded data sent from another email address using Thunderbird
    p.setOutputFileName(output);
    p.setPassphrase(passphrase);
    p.setSecretKeyFileName(skeyfile);//this is the GPG-generated key
    return p.decrypt();//this line throws the error
}

PGPFileProcessor.java 包括：

public InputStream decrypt() throws Exception {
    FileInputStream in = new FileInputStream(inputFileName);
    FileInputStream keyIn = new FileInputStream(secretKeyFileName);
    FileOutputStream out = new FileOutputStream(outputFileName);
    PGPUtils.decryptFile(in, out, keyIn, passphrase.toCharArray());//error thrown here
    in.close();
    out.close();
    keyIn.close();
    InputStream result = new FileInputStream(outputFileName);//I changed return type from boolean on 1/27/15
    Files.deleteIfExists(Paths.get(outputFileName));//I also added this to accommodate change of return type on 1/27/15
    return result;
}

PGPUtils.java 包括：

/**
 * decrypt the passed in message stream
 */
@SuppressWarnings("unchecked")
public static void decryptFile(InputStream in, OutputStream out, InputStream keyIn, char[] passwd)
    throws Exception
{
    Security.addProvider(new BouncyCastleProvider());

    in = org.bouncycastle.openpgp.PGPUtil.getDecoderStream(in);

    //1/26/15 added Jca prefix to avoid eclipse warning, also used https://www.bouncycastle.org/docs/pgdocs1.5on/index.html
    PGPObjectFactory pgpF = new JcaPGPObjectFactory(in);
    PGPEncryptedDataList enc;

    Object o = pgpF.nextObject();
    //
    // the first object might be a PGP marker packet.
    //
    if (o instanceof  PGPEncryptedDataList) {enc = (PGPEncryptedDataList) o;}
    else {enc = (PGPEncryptedDataList) pgpF.nextObject();}

    //
    // find the secret key
    //
    Iterator<PGPPublicKeyEncryptedData> it = enc.getEncryptedDataObjects();
    PGPPrivateKey sKey = null;
    PGPPublicKeyEncryptedData pbe = null;

    while (sKey == null && it.hasNext()) {
        pbe = it.next(); 
        sKey = findPrivateKey(keyIn, pbe.getKeyID(), passwd);
    }

    if (sKey == null) {throw new IllegalArgumentException("Secret key for message not found.");}

    InputStream clear = pbe.getDataStream(new BcPublicKeyDataDecryptorFactory(sKey));

    //1/26/15 added Jca prefix to avoid eclipse warning, also used https://www.bouncycastle.org/docs/pgdocs1.5on/index.html
    PGPObjectFactory plainFact = new JcaPGPObjectFactory(clear);

    Object message = plainFact.nextObject();

    if (message instanceof  PGPCompressedData) {
        PGPCompressedData cData = (PGPCompressedData) message;
        //1/26/15 added Jca prefix to avoid eclipse warning, also used https://www.bouncycastle.org/docs/pgdocs1.5on/index.html
        PGPObjectFactory pgpFact = new JcaPGPObjectFactory(cData.getDataStream()); 
        message = pgpFact.nextObject();
    }

    if (message instanceof  PGPLiteralData) {
        PGPLiteralData ld = (PGPLiteralData) message;

        InputStream unc = ld.getInputStream();
        int ch;

        while ((ch = unc.read()) >= 0) {out.write(ch);}
    } else if (message instanceof  PGPOnePassSignatureList) {
        throw new PGPException("Encrypted message contains a signed message - not literal data.");
    } else {
        throw new PGPException("Message is not a simple encrypted file - type unknown.");
    }

    if (pbe.isIntegrityProtected()) {
        if (!pbe.verify()) {throw new PGPException("Message failed integrity check");}
    }
}

/**
 * Load a secret key ring collection from keyIn and find the private key corresponding to
 * keyID if it exists.
 *
 * @param keyIn input stream representing a key ring collection.
 * @param keyID keyID we want.
 * @param pass passphrase to decrypt secret key with.
 * @return
 * @throws IOException
 * @throws PGPException
 * @throws NoSuchProviderException
 */
public  static PGPPrivateKey findPrivateKey(InputStream keyIn, long keyID, char[] pass)
    throws IOException, PGPException, NoSuchProviderException
{
    //1/26/15 added Jca prefix to avoid eclipse warning, also used https://www.bouncycastle.org/docs/pgdocs1.5on/index.html
    PGPSecretKeyRingCollection pgpSec = new JcaPGPSecretKeyRingCollection(PGPUtil.getDecoderStream(keyIn));
    return findPrivateKey(pgpSec.getSecretKey(keyID), pass);

}

/**
 * Load a secret key and find the private key in it
 * @param pgpSecKey The secret key
 * @param pass passphrase to decrypt secret key with
 * @return
 * @throws PGPException
 */
public static PGPPrivateKey findPrivateKey(PGPSecretKey pgpSecKey, char[] pass)
    throws PGPException
{
    if (pgpSecKey == null) return null;

    PBESecretKeyDecryptor decryptor = new BcPBESecretKeyDecryptorBuilder(new BcPGPDigestCalculatorProvider()).build(pass);
    return pgpSecKey.extractPrivateKey(decryptor);
}  

所有三个 Java 文件的完整代码都可以在文件共享网站by clicking on this link 上找到。

可以找到错误的完整堆栈跟踪by clicking on this link。

作为参考，远程 Thunderbird 发送者加密的 GUI 说明总结在以下屏幕截图中：

我已经阅读了很多关于此的帖子和链接。尤其是this other SO posting looks similar，却是不同的。我的密钥使用 RSA RSA，但其他帖子没有。

编辑#1

根据@DavidHook 的建议，我已经阅读了SignedFileProcessor，并且我开始阅读更长的RFC 4880。但是，我需要学习实际的工作代码才能理解这一点。大多数通过 google 搜索找到此内容的人还需要工作代码来说明示例。

供参考，@DavidHook 推荐的SignedFileProcessor.verifyFile() 方法如下。 应如何自定义以解决上述代码中的问题？

private static void verifyFile(InputStream in, InputStream keyIn) throws Exception {
    in = PGPUtil.getDecoderStream(in);
    PGPObjectFactory pgpFact = new PGPObjectFactory(in);
    PGPCompressedData c1 = (PGPCompressedData)pgpFact.nextObject();
    pgpFact = new PGPObjectFactory(c1.getDataStream());
    PGPOnePassSignatureList p1 = (PGPOnePassSignatureList)pgpFact.nextObject();
    PGPOnePassSignature ops = p1.get(0);
    PGPLiteralData p2 = (PGPLiteralData)pgpFact.nextObject();
    InputStream dIn = p2.getInputStream();
    int ch;
    PGPPublicKeyRingCollection  pgpRing = new PGPPublicKeyRingCollection(PGPUtil.getDecoderStream(keyIn));
    PGPPublicKey key = pgpRing.getPublicKey(ops.getKeyID());
    FileOutputStream out = new FileOutputStream(p2.getFileName());
    ops.initVerify(key, "BC");
    while ((ch = dIn.read()) >= 0){
        ops.update((byte)ch);
        out.write(ch);
    }
    out.close();
    PGPSignatureList p3 = (PGPSignatureList)pgpFact.nextObject();
    if (ops.verify(p3.get(0))){System.out.println("signature verified.");}
    else{System.out.println("signature verification failed.");}
}

编辑#2

@DavidHook 推荐的SignedFileProcessor.verifyFile() 方法与我上面代码中的PGPUtils.verifyFile() 方法几乎相同，只是PGPUtils.verifyFile() 复制了extractContentFile 并调用PGPOnePassSignature.init() 而不是PGPOnePassSignature.initVerify()。这可能是由于版本差异。此外，PGPUtils.verifyFile() 返回一个布尔值，而SignedFileProcessor.verifyFile() 为两个布尔值提供 SYSO，并在 SYSO 之后返回 void。

如果我正确解释 @JRichardSnape 的 cmets，这意味着最好在上游调用 verifyFile() 方法以使用发送者的公钥确认传入文件的签名，然后，如果文件上的签名被验证，使用另一种方法使用接收者的私钥解密文件。它是否正确？如果是这样，我该如何重构代码来实现这一点？

Answer 1

这只是意味着内容已经签名然后加密，提供的例程不知道如何处理它，但至少告诉你。 PGP协议呈现为一系列数据包，其中一些可以包装在其他数据包中（例如压缩数据也可以包装签名数据或简单的文字数据，这些也可以用来生成加密数据，实际内容总是出现在文字数据中)。

如果您查看 Bouncy Castle OpenPGP 示例包中 SignedFileProcessor 中的 verifyFile 方法，您将了解如何处理签名数据并获取包含实际内容的文字数据。

我还建议您查看 RFC 4880，以便您了解该协议的工作原理。该协议非常松散，GPG、BC 和那里的各种产品都反映了这一点——也就是说，松散确实意味着如果您尝试剪切和粘贴您的解决方案，您最终会遇到灾难。并不复杂，但这里也需要理解。

Answer 2

如果有人有兴趣了解如何使用 bouncy castle openPGP 库加密和解密 gpg 文件，请查看以下 java 代码：

以下是您需要的 4 种方法：

以下方法将从 .asc 文件中读取并导入您的密钥：

public static PGPSecretKey readSecretKeyFromCol(InputStream in, long keyId) throws IOException, PGPException {
in = PGPUtil.getDecoderStream(in);
PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(in, new BcKeyFingerprintCalculator());

PGPSecretKey key = pgpSec.getSecretKey(keyId);

if (key == null) {
    throw new IllegalArgumentException("Can't find encryption key in key ring.");
}
return key;
}

以下方法将从 .asc 文件中读取并导入您的公钥：

@SuppressWarnings("rawtypes")
public static PGPPublicKey readPublicKeyFromCol(InputStream in) throws IOException, PGPException {
    in = PGPUtil.getDecoderStream(in);
    PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(in, new BcKeyFingerprintCalculator());
    PGPPublicKey key = null;
    Iterator rIt = pgpPub.getKeyRings();
    while (key == null && rIt.hasNext()) {
        PGPPublicKeyRing kRing = (PGPPublicKeyRing) rIt.next();
        Iterator kIt = kRing.getPublicKeys();
        while (key == null && kIt.hasNext()) {
            PGPPublicKey k = (PGPPublicKey) kIt.next();
            if (k.isEncryptionKey()) {
                key = k;
            }
        }
    }
    if (key == null) {
        throw new IllegalArgumentException("Can't find encryption key in key ring.");
    }
    return key;
}

以下2种解密和加密gpg文件的方法：

public void decryptFile(InputStream in, InputStream secKeyIn, InputStream pubKeyIn, char[] pass) throws IOException, PGPException, InvalidCipherTextException {
    Security.addProvider(new BouncyCastleProvider());

    PGPPublicKey pubKey = readPublicKeyFromCol(pubKeyIn);

    PGPSecretKey secKey = readSecretKeyFromCol(secKeyIn, pubKey.getKeyID());

    in = PGPUtil.getDecoderStream(in);

    JcaPGPObjectFactory pgpFact;


    PGPObjectFactory pgpF = new PGPObjectFactory(in, new BcKeyFingerprintCalculator());

    Object o = pgpF.nextObject();
    PGPEncryptedDataList encList;

    if (o instanceof PGPEncryptedDataList) {

        encList = (PGPEncryptedDataList) o;

    } else {

        encList = (PGPEncryptedDataList) pgpF.nextObject();

    }

    Iterator<PGPPublicKeyEncryptedData> itt = encList.getEncryptedDataObjects();
    PGPPrivateKey sKey = null;
    PGPPublicKeyEncryptedData encP = null;
    while (sKey == null && itt.hasNext()) {
        encP = itt.next();
        secKey = readSecretKeyFromCol(new FileInputStream("PrivateKey.asc"), encP.getKeyID());
        sKey = secKey.extractPrivateKey(new BcPBESecretKeyDecryptorBuilder(new BcPGPDigestCalculatorProvider()).build(pass));
    }
    if (sKey == null) {
        throw new IllegalArgumentException("Secret key for message not found.");
    }

    InputStream clear = encP.getDataStream(new BcPublicKeyDataDecryptorFactory(sKey));

    pgpFact = new JcaPGPObjectFactory(clear);

    PGPCompressedData c1 = (PGPCompressedData) pgpFact.nextObject();

    pgpFact = new JcaPGPObjectFactory(c1.getDataStream());

    PGPLiteralData ld = (PGPLiteralData) pgpFact.nextObject();
    ByteArrayOutputStream bOut = new ByteArrayOutputStream();

    InputStream inLd = ld.getDataStream();

    int ch;
    while ((ch = inLd.read()) >= 0) {
        bOut.write(ch);
    }

    //System.out.println(bOut.toString());

    bOut.writeTo(new FileOutputStream(ld.getFileName()));
    //return bOut;

}

public static void encryptFile(OutputStream out, String fileName, PGPPublicKey encKey) throws IOException, NoSuchProviderException, PGPException {
    Security.addProvider(new BouncyCastleProvider());

    ByteArrayOutputStream bOut = new ByteArrayOutputStream();

    PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(PGPCompressedData.ZIP);

    PGPUtil.writeFileToLiteralData(comData.open(bOut), PGPLiteralData.BINARY, new File(fileName));

    comData.close();

    PGPEncryptedDataGenerator cPk = new PGPEncryptedDataGenerator(new BcPGPDataEncryptorBuilder(SymmetricKeyAlgorithmTags.TRIPLE_DES).setSecureRandom(new SecureRandom()));

    cPk.addMethod(new BcPublicKeyKeyEncryptionMethodGenerator(encKey));

    byte[] bytes = bOut.toByteArray();

    OutputStream cOut = cPk.open(out, bytes.length);

    cOut.write(bytes);

    cOut.close();

    out.close();
}

现在这里是如何调用/运行上面的：

try {
         decryptFile(new FileInputStream("encryptedFile.gpg"), new FileInputStream("PrivateKey.asc"), new FileInputStream("PublicKey.asc"), "yourKeyPassword".toCharArray());

        PGPPublicKey pubKey = readPublicKeyFromCol(new FileInputStream("PublicKey.asc"));

        encryptFile(new FileOutputStream("encryptedFileOutput.gpg"), "fileToEncrypt.txt", pubKey);




    } catch (PGPException e) {
        fail("exception: " + e.getMessage(), e.getUnderlyingException());
    }