Add unit test to verify that decryption is possible

CREATE_RELEASE.md

@@ -29,8 +29,8 @@ This document describes how to create a new release.
 
 ### DigiTally
 
-- Compress all files from `output/Release/DigiTally/net472` into a `DigitaleBriefwahl.
-  DigiTally-1.4.0.zip` file.
+- Compress all files from `output/Release/DigiTally/net472` into a
+  `DigitaleBriefwahl.DigiTally-1.4.0.zip` file.
 
 ### MacOS
 

DigitaleBriefwahlTests/Encryption/DecryptHelper.cs

@@ -0,0 +1,93 @@
+using System.IO;
+using System.Linq;
+using Org.BouncyCastle.Bcpg.OpenPgp;
+using Org.BouncyCastle.Utilities.IO;
+
+namespace DigitaleBriefwahlTests.Encryption
+{
+	public static class DecryptHelper
+	{
+		private static PgpPrivateKey GetPrivateKey(string privateKeyPath, char[] passPhrase)
+		{
+			using Stream keyIn = File.OpenRead(privateKeyPath);
+			using Stream inputStream = PgpUtilities.GetDecoderStream(keyIn);
+			PgpSecretKeyRingBundle secretKeyRingBundle = new PgpSecretKeyRingBundle(inputStream);
+
+			PgpSecretKey key = null;
+			foreach (PgpSecretKeyRing kRing in secretKeyRingBundle.GetKeyRings())
+			{
+				foreach (PgpSecretKey secretKey in kRing.GetSecretKeys())
+				{
+					return secretKey.ExtractPrivateKey(passPhrase);
+				}
+			}
+
+			return null;
+		}
+
+		public static string DecryptFile(string inputFile, string privateKeyFile)
+		{
+			using var stream = File.OpenRead(inputFile);
+			var outputFile = Path.GetTempFileName();
+			if (DecryptFile(stream, outputFile, privateKeyFile))
+			{
+				var content = File.ReadAllText(outputFile);
+				File.Delete(outputFile);
+				return content;
+			}
+
+			File.Delete(outputFile);
+			return null;
+		}
+
+		private static bool DecryptFile(Stream inputStream, string outputFile,
+			string privateKeyLoc)
+		{
+			PgpEncryptedDataList enc;
+
+			using var newStream = PgpUtilities.GetDecoderStream(inputStream);
+			var pgpObjF = new PgpObjectFactory(newStream);
+			if (pgpObjF.NextPgpObject() is PgpEncryptedDataList list)
+			{
+				enc = list;
+			}
+			else
+			{
+				enc = (PgpEncryptedDataList)pgpObjF.NextPgpObject();
+			}
+
+			var privKey = GetPrivateKey(privateKeyLoc, null);
+
+			var pbe = enc.GetEncryptedDataObjects().Cast<PgpPublicKeyEncryptedData>().First();
+
+			using var clear = pbe.GetDataStream(privKey);
+			using var memoryStream = new MemoryStream();
+			clear.CopyTo(memoryStream);
+			var plainBytes = memoryStream.ToArray();
+			var plainFact = new PgpObjectFactory(plainBytes);
+			var message = plainFact.NextPgpObject();
+			if (message is PgpCompressedData cData)
+			{
+				using var compDataIn = cData.GetDataStream();
+				var o = new PgpObjectFactory(compDataIn);
+				message = o.NextPgpObject();
+				if (message is PgpOnePassSignatureList)
+				{
+					message = o.NextPgpObject();
+				}
+
+				PgpLiteralData literalData = null;
+				literalData = (PgpLiteralData)message;
+				if (literalData != null)
+				{
+					using var output = File.Create(outputFile);
+					using var unc = literalData.GetInputStream();
+					Streams.PipeAll(unc, output);
+					return true;
+				}
+			}
+
+			return false;
+		}
+	}
+}

DigitaleBriefwahlTests/Encryption/EncryptVoteTests.cs

@@ -0,0 +1,211 @@
+// Copyright (c) 2021 Eberhard Beilharz
+// This software is licensed under the GNU General Public License version 3
+// (https://opensource.org/licenses/GPL-3.0)
+
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+using System.Text;
+using DigitaleBriefwahl;
+using DigitaleBriefwahl.Encryption;
+using DigitaleBriefwahl.Model;
+using NUnit.Framework;
+using Org.BouncyCastle.Bcpg;
+using Org.BouncyCastle.Utilities.Encoders;
+using Org.BouncyCastle.Utilities.IO;
+
+namespace DigitaleBriefwahlTests.Encryption
+{
+	[TestFixture]
+	public class EncryptVoteTests
+	{
+		private readonly List<string> _filesToDelete = new List<string>();
+
+		[TearDown]
+		public void TearDown()
+		{
+			foreach (var file in _filesToDelete)
+			{
+				try
+				{
+					if (Directory.Exists(file))
+					{
+						foreach (var f in Directory.GetFiles(file))
+						{
+							File.Delete(f);
+						}
+
+						Directory.Delete(file);
+					}
+					else
+					{
+						File.Delete(file);
+					}
+				}
+				// ReSharper disable once EmptyGeneralCatchClause
+				catch
+				{
+				}
+			}
+			_filesToDelete.Clear();
+		}
+
+		[Test]
+		[Repeat(10)]
+		public void BallotFilePath_HasConstantLength()
+		{
+			var sut = new EncryptVote("foo");
+			var ballotFilePath = sut.BallotFilePath;
+			var tempPath = Path.GetTempPath();
+			tempPath = tempPath.Replace(@"\", @"\\");
+			Assert.That(ballotFilePath, Does.Match($"{tempPath}foo_[0-9A-F]{{32}}.txt"));
+			Assert.That(ballotFilePath.Length, Is.EqualTo(Path.GetTempPath().Length + 4 /* foo_ */ + 32 + 4 /* .txt */));
+		}
+
+		[Test]
+		public void BallotFilePath_NumberMatchesBallotId()
+		{
+			var ballotId = BallotHelper.BallotId;
+			var expectedNumber = ballotId.Replace("-", "");
+
+			var sut = new EncryptVote("foo");
+			Assert.That(sut.BallotFilePath, Is.EqualTo($"{Path.GetTempPath()}foo_{expectedNumber}.txt"));
+		}
+
+		[Test]
+		public void GetEncryptedFilePath()
+		{
+			var sut = new EncryptVote("foo");
+			Assert.That(sut.GetEncryptedFilePath(sut.BallotFilePath),
+				Is.EqualTo(sut.BallotFilePath.Substring(0, sut.BallotFilePath.Length - 4) + ".gpg"));
+		}
+
+		[Test]
+		public void GetEncryptedFilePath_Umlaut_AllASCII()
+		{
+			var sut= new EncryptVote("ÄÖÜäöüß");
+			var filePath = Path.GetFileName(sut.GetEncryptedFilePath(sut.BallotFilePath));
+			Assert.That(filePath.StartsWith("AEOEUEaeoeuess"), Is.True,
+				$"Unexpected FilePath.\n    Expected: AEOEUEaeoeuess...\n    But was:  {filePath}");
+		}
+
+		[Test]
+		public void GetEncryptedFilePath_Other_AllASCII()
+		{
+			var sut= new EncryptVote("ខ្មែរ");
+			var filePath = sut.GetEncryptedFilePath(sut.BallotFilePath);
+			foreach (var c in filePath.ToCharArray())
+			{
+				Assert.That(c, Is.LessThanOrEqualTo(128),
+					$"FilePath contains non-ASCII characters: {filePath}");
+			}
+		}
+
+		#region Test Keys
+
+		private const string KeyHandle = "484AE369B6634B18";
+		private const string PublicKey = @"-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+=Iqyo
+-----END PGP PUBLIC KEY BLOCK-----
+";
+
+		private const string PrivateKeyData = @"lQHYBGZnOt8BBADWJ0pLf7NUuycZ/VnTf6GZQ0cPjUXBW+g604PaopfiAaEOeko/7ByZoTrp2XDU
+kL95dSs2flMviSDlwnndBRoKIqXNEyVIwmWvCO7/0N9Cz7ZaLUq94A46Bc/XnQ0Or0hFIimjawTM
+qsgbu+qOurPGm32t+kMViuwhZ7pvM7UeiQARAQABAAP+IAvLG1clr8U9ya7W1UZhGT0vEg2y5Ydq
+Tfs+3OW90q0pu6/jEoOzl+2/kiTetIBglr1I1SO8MP3VNWyPrdpIlftdNvo3b4F/P+To43pgk2+9
+Dk7RP885AG+9auDGZNiqAxJgm40RlnleV2EDOYBlb/yNHWecqkAGr/F+p/oWnC0CANdfdtbMT4bm
+PCdHA7xa+wmfP+ZbtzLQFuy16SvCgJMH9aybZijO2Opuq3bfQ8RE4pTNWN2USlp8gnn5TjuO+h8C
+AP6M8FCynwun7PBOXDaoueQzgJt4KLrZBRXeRKHdAeET3M0XDRsGezSEH/cVGCytr72RxBzPvYTU
+zMnR5rZaIlcB/2yDh4SNjvUYpecuLtEvcMMsCU40QEDBmrpZ+2xwsm6ohuSrI87o6YV13vbZoAZq
+qFxWFglgG9w+cFFK+setVZamsrQNRGlnaXdhaGwgVGVzdIjOBBMBCgA4FiEEoZe7NEOYJDQqDEDg
+SErjabZjSxgFAmZnOt8CGwMFCwkIBwMFFQoJCAsFFgIDAQACHgECF4AACgkQSErjabZjSxhskgP/
+UlbmSGORyzNZ6PUGcZ+5t0ov/mq4h/NnRXpv9StOZbBIU2eW9eEW8YTJ+m2bka7BdMVNCrKhaVVM
+jRK1bFNuFgQIsNR0a2t4qw0gMI1LGiYNvx8HvBnHpX6ffgyZyWzUNHJju/dQkbum906E5iI/lWux
+NL/mwnf9/VkZA7BYdp2dAdgEZmc63wEEAMyV9mBNWfDcL5xCZAIIHCr/aSkFswn2/hwfI5DXR2Gp
+BJsaF5GD9mFZwmfHHRmHKy32mRIfJdH3oEhZKSI74+wRTR5GpAlWzQRNV1vHJJYPF9tliDFl1DTH
+xLeWMkiW1J8GbZth94zP7JRkk7YTswDMdeT/eAThj3Y+FK6VgMsBABEBAAEAA/0YNwPDYERuAtHL
+z/vgVa9n03VR+q+3VTm8gF8ITMLRJ105Mnxpp9HoseQVvnaOR/ZvaUmy4GbslD+vcIYy3B3c4+1Z
+iYsGgJMr9m02aFCXzpHLFVvb0t+hZ7RFpEav0J5Zmp23br/SUoby+QhKp5cW8xTte7jtawTKWj2j
+DBz0wQIA2cM4nJ1ia/tJp+jNuFEni64OWm3J0OmL4zWWUB9o0fUPT5tRzyjB4Z+thMaRLp2IPGiz
+yhkisQbDnmNyNHyoaQIA8IJsWcdJK6WWSnA15BZ0pXwpaYZqZU/m7SaANCR+kRZFqGOHkdeijq7v
+hX93eIwY0SLsFHQh60m3gdNRYHR62QIA49xtsTi3bj1MXe00fhN6dm2pbXaVJdZrzKSVuZkMgBqP
+u7r9CBhSzYE6jtp27v4nfBBq6uECgq7qIe0RnTugNqXtiLYEGAEKACAWIQShl7s0Q5gkNCoMQOBI
+SuNptmNLGAUCZmc63wIbDAAKCRBISuNptmNLGL7YA/9t0kpUNAvN+YwgXyUYZun8EpwpOFfSmVIO
+biJPG/vD+xbIiaXZeBsGjyvG8GEt8jRP4pQUwUe7PHh1iPEzmRQoYjiWV1NFAci/TJUl+pKLP5AB
+LvLVc3MNp8K/TwAuyC0+hHLy7jwqkO49NT2fhie8Rpxwf1udyJvgyDMXaJ+vpQ==
+";
+		#endregion
+
+		[Test]
+		public void EncryptVote_CanDecrypt()
+		{
+			// Setup
+			var privateKeyFile = Path.GetTempFileName();
+			_filesToDelete.Add(privateKeyFile);
+			var privateKey = Base64.Decode(PrivateKeyData);
+			File.WriteAllBytes(privateKeyFile, privateKey);
+
+			var tempFolder = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
+			Directory.CreateDirectory(tempFolder);
+			_filesToDelete.Add(tempFolder);
+
+			var publicKey = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location),
+				$"{KeyHandle}.asc");
+			File.WriteAllText(publicKey, PublicKey);
+
+			var wahlini = Path.Combine(tempFolder, "wahl.ini");
+			File.WriteAllText(wahlini, @$"[Wahlen]
+Titel=Test
+PublicKey={KeyHandle}.asc
+Email=nobody@example.com");
+
+			var configuration = Configuration.Configure(wahlini);
+
+			var vote = "Vereinswahlen 2024\r\n" +
+				"==================\r\n" +
+				"\r\n" +
+				"Geschäftsführer\r\n" +
+				"---------------\r\n" +
+				"(J=Ja, E=Enthaltung, N=Nein)\r\n" +
+				"1. [J] Siegfried Siegreich\r\n" +
+				"\r\n" +
+				"Vorstand\r\n" +
+				"--------\r\n" +
+				"(1 Stimme; Wahl mit 1. kennzeichnen)\r\n" +
+				"   Max Mayer\r\n" +
+				"1. Anton Anders\r\n" +
+				"   Gustav Graf\r\n" +
+				"\r\n" +
+				"\r\n" +
+				$"{BallotHelper.BallotId}\r\n";
+
+			var voteFile = Path.Combine(tempFolder,
+				$"Test_{BallotHelper.BallotId.Replace("-", "")}.txt");
+
+			// Execute
+			var filename = new EncryptVote("Test").WriteVote(vote, voteFile);
+			_filesToDelete.Add(filename);
+
+			// Verify
+			Assert.That(filename, Is.EqualTo(Path.Combine(tempFolder, Path.GetFileNameWithoutExtension
+				(voteFile) + ".gpg")));
+			Assert.That(DecryptHelper.DecryptFile(filename, privateKeyFile), Is.EqualTo(vote));
+		}
+	}
+}