使用 BouncyCastle c# 进行 PgP 加密和解密

Question

我看过很多帖子，学习了很多教程，但似乎没有一个有效。有时，它们会引用一些未找到的类。能否指点一个地方，在那里我可以获得一个简单的教程，展示如何加密和解密文件。

我是 Pgp 的新手，欢迎任何帮助。

Answer 1

我知道这个问题已有多年历史，但在 Google 中使用 Bouncy Castle 进行与 PGP 解密相关的搜索仍然是第一或第二。由于似乎很难找到一个完整、简洁的示例，因此我想在这里分享我的工作解决方案来解密 PGP 文件。这只是其源文件中包含的 Bouncy Castle 示例的修改版本。

using System;
using System.IO;
using Org.BouncyCastle.Bcpg.OpenPgp;
using Org.BouncyCastle.Utilities.IO;

namespace PGPDecrypt
{
    class Program
    {
        static void Main(string[] args)
        {
            DecryptFile(
                @"path_to_encrypted_file.pgp",
                @"path_to_secret_key.asc",
                "your_password_here".ToCharArray(), 
                "output.txt"
            );
        }

        private static void DecryptFile(
            string inputFileName,
            string keyFileName,
            char[] passwd,
            string defaultFileName)
        {
            using (Stream input = File.OpenRead(inputFileName),
                   keyIn = File.OpenRead(keyFileName))
            {
                DecryptFile(input, keyIn, passwd, defaultFileName);
            }
        }

        private static void DecryptFile(
            Stream inputStream,
            Stream keyIn,
            char[] passwd,
            string defaultFileName)
        {
            inputStream = PgpUtilities.GetDecoderStream(inputStream);

            try
            {
                PgpObjectFactory pgpF = new PgpObjectFactory(inputStream);
                PgpEncryptedDataList enc;

                PgpObject o = pgpF.NextPgpObject();
                //
                // the first object might be a PGP marker packet.
                //
                if (o is PgpEncryptedDataList)
                {
                    enc = (PgpEncryptedDataList)o;
                }
                else
                {
                    enc = (PgpEncryptedDataList)pgpF.NextPgpObject();
                }

                //
                // find the secret key
                //
                PgpPrivateKey sKey = null;
                PgpPublicKeyEncryptedData pbe = null;
                PgpSecretKeyRingBundle pgpSec = new PgpSecretKeyRingBundle(
                    PgpUtilities.GetDecoderStream(keyIn));

                foreach (PgpPublicKeyEncryptedData pked in enc.GetEncryptedDataObjects())
                {
                    sKey = FindSecretKey(pgpSec, pked.KeyId, passwd);

                    if (sKey != null)
                    {
                        pbe = pked;
                        break;
                    }
                }

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

                Stream clear = pbe.GetDataStream(sKey);

                PgpObjectFactory plainFact = new PgpObjectFactory(clear);

                PgpObject message = plainFact.NextPgpObject();

                if (message is PgpCompressedData)
                {
                    PgpCompressedData cData = (PgpCompressedData)message;
                    PgpObjectFactory pgpFact = new PgpObjectFactory(cData.GetDataStream());

                    message = pgpFact.NextPgpObject();
                }

                if (message is PgpLiteralData)
                {
                    PgpLiteralData ld = (PgpLiteralData)message;

                    string outFileName = ld.FileName;
                    if (outFileName.Length == 0)
                    {
                        outFileName = defaultFileName;
                    }

                    Stream fOut = File.Create(outFileName);
                    Stream unc = ld.GetInputStream();
                    Streams.PipeAll(unc, fOut);
                    fOut.Close();
                }
                else if (message is 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())
                    {
                        Console.Error.WriteLine("message failed integrity check");
                    }
                    else
                    {
                        Console.Error.WriteLine("message integrity check passed");
                    }
                }
                else
                {
                    Console.Error.WriteLine("no message integrity check");
                }
            }
            catch (PgpException e)
            {
                Console.Error.WriteLine(e);

                Exception underlyingException = e.InnerException;
                if (underlyingException != null)
                {
                    Console.Error.WriteLine(underlyingException.Message);
                    Console.Error.WriteLine(underlyingException.StackTrace);
                }
            }
        }

        private static PgpPrivateKey FindSecretKey(PgpSecretKeyRingBundle pgpSec, long keyID, char[] pass)
        {
            PgpSecretKey pgpSecKey = pgpSec.GetSecretKey(keyID);

            if (pgpSecKey == null)
            {
                return null;
            }

            return pgpSecKey.ExtractPrivateKey(pass);
        }
    }
}

Answer 2

怎么样：

PartialInputStream during Bouncycastle PGP decryption

此外，zip 包含此处的示例：

http://www.bouncycastle.org/csharp/

希望这会有所帮助。如果您仍然卡住，请发布有关编译器抱怨的类的更多详细信息，社区将会查看。

Answer 3

我使用了 PgpCore 包，它是 Portable.BouncyCastle 的包装器。

它非常干净且易于使用。多个示例可用here。

Answer 4

现在，在 2021 年，Nikhil 的答案可能是最好的，因为它抽象出了直接使用 BouncyCastle 的需求。去给他点个赞吧。

如果您出于某种原因想直接使用 BouncyCastle，我有 Dan 的答案的现代实现以及他正在使用的示例，它直接在 NET5 中使用 BouncyCastle。看看：

using Org.BouncyCastle.Bcpg;
using Org.BouncyCastle.Bcpg.OpenPgp;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities.IO;

安装的是 Nuget Package Portable.BouncyCastle 1.8.10。

public class EncryptionService 
{
    public static void EncryptPGPFile(FileInfo inFile, FileInfo keyFile, FileInfo outFile, bool withIntegrityCheck = false, bool withArmor = false)
    {
        PgpPublicKeyRingBundle keyRing = null;
        using (var keyStream = keyFile.OpenRead())
        {
            keyRing = new PgpPublicKeyRingBundle(PgpUtilities.GetDecoderStream(keyStream));
        }

        var publicKey = keyRing.GetKeyRings()
            .Cast<PgpPublicKeyRing>()
            .FirstOrDefault()
            ?.GetPublicKeys()
            .Cast<PgpPublicKey>()
            .FirstOrDefault(x => x.IsEncryptionKey);

        using var outFileStream = outFile.Open(FileMode.Create);
        using var armoredStream = new ArmoredOutputStream(outFileStream);
        Stream outStream = withArmor ? armoredStream : outFileStream;

        byte[] compressedBytes;

        var compressor = new PgpCompressedDataGenerator(CompressionAlgorithmTag.Zip);

        using (var byteStream = new MemoryStream())
        {
            // Annoyingly, this is necessary. The compressorStream needs to be closed before the byteStream is read from, otherwise
            // data will be left in the buffer and not written to the byteStream. It would be nice if compressorStream exposed a "Flush"
            // method. - AJS
            using (var compressorStream = compressor.Open(byteStream))
            {
                PgpUtilities.WriteFileToLiteralData(compressorStream, PgpLiteralData.Binary, inFile);
            }
            compressedBytes = byteStream.ToArray();
        };

        var encrypter = new PgpEncryptedDataGenerator(SymmetricKeyAlgorithmTag.Cast5, withIntegrityCheck, new SecureRandom());
        encrypter.AddMethod(publicKey);

        using var finalOutputStream = encrypter.Open(outStream, compressedBytes.Length);
        finalOutputStream.Write(compressedBytes, 0, compressedBytes.Length);
    }

    public static void DecryptPGPFile(FileInfo inFile, FileInfo keyFile, string password, FileInfo outFile)
    {
        using var inputFile = inFile.OpenRead();
        using var input = PgpUtilities.GetDecoderStream(inputFile);

        var pgpFactory = new PgpObjectFactory(input);

        var firstObject = pgpFactory.NextPgpObject();
        if (firstObject is not PgpEncryptedDataList)
        {
            firstObject = pgpFactory.NextPgpObject();
        }

        PgpPrivateKey keyToUse = null;
        PgpSecretKeyRingBundle keyRing = null;

        using (var keyStream = keyFile.OpenRead())
        {
            keyRing = new PgpSecretKeyRingBundle(PgpUtilities.GetDecoderStream(keyStream));
        }

        var encryptedData = ((PgpEncryptedDataList)firstObject).GetEncryptedDataObjects()
            .Cast<PgpPublicKeyEncryptedData>()
            .FirstOrDefault(x =>
            {
                var key = keyRing.GetSecretKey(x.KeyId);
                if (key != null)
                {
                    keyToUse = key.ExtractPrivateKey(password.ToCharArray());
                    return true;
                }
                return false;
            });

        if (keyToUse == null)
        {
            throw new PgpException("Cannot find secret key for message.");
        }

        Stream clearText = encryptedData.GetDataStream(keyToUse);
        PgpObject message = new PgpObjectFactory(clearText).NextPgpObject();

        if (message is PgpCompressedData data)
        {
            message = new PgpObjectFactory(inputStream: data.GetDataStream()).NextPgpObject();
        }

        if (message is PgpLiteralData literalData)
        {
            using var outputFileStream = outFile.Open(FileMode.Create);
            Streams.PipeAll(literalData.GetInputStream(), outputFileStream);
        }
        else
        {
            throw new PgpException("message is not encoded correctly.");
        }

        if (encryptedData.IsIntegrityProtected() && !encryptedData.Verify())
        {
            throw new Exception("message failed integrity check!");
        }
    }
}