RAR5 decryption support

src/SharpCompress/Archives/Rar/SeekableFilePart.cs

@@ -25,10 +25,19 @@ internal class SeekableFilePart : RarFilePart
     internal override Stream GetCompressedStream()
     {
         stream.Position = FileHeader.DataStartPosition;
+
         if (FileHeader.R4Salt != null)
         {
-            return new RarCryptoWrapper(stream, password!, FileHeader.R4Salt);
+            var cryptKey = new CryptKey3(password!);
+            return new RarCryptoWrapper(stream, FileHeader.R4Salt, cryptKey);
         }
+
+        if (FileHeader.Rar5CryptoInfo != null)
+        {
+            var cryptKey = new CryptKey5(password!, FileHeader.Rar5CryptoInfo);
+            return new RarCryptoWrapper(stream, FileHeader.Rar5CryptoInfo.Salt, cryptKey);
+        }
+
         return stream;
     }
 

src/SharpCompress/Common/Rar/CryptKey3.cs

@@ -0,0 +1,87 @@
+#nullable disable
+
+using System.Security.Cryptography;
+using System.Text;
+using SharpCompress.Common.Rar.Headers;
+
+namespace SharpCompress.Common.Rar;
+
+internal class CryptKey3 : ICryptKey
+{
+    const int AES_128 = 128;
+
+    private string _password;
+
+    public CryptKey3(string password)
+    {
+        _password = password ?? "";
+    }
+
+    public ICryptoTransform Transformer(byte[] salt)
+    {
+        var aesIV = new byte[EncryptionConstV5.SIZE_INITV];
+
+        var rawLength = 2 * _password.Length;
+        var rawPassword = new byte[rawLength + EncryptionConstV5.SIZE_SALT30];
+        var passwordBytes = Encoding.UTF8.GetBytes(_password);
+        for (var i = 0; i < _password.Length; i++)
+        {
+            rawPassword[i * 2] = passwordBytes[i];
+            rawPassword[(i * 2) + 1] = 0;
+        }
+
+        for (var i = 0; i < salt.Length; i++)
+        {
+            rawPassword[i + rawLength] = salt[i];
+        }
+
+        var msgDigest = SHA1.Create();
+        const int noOfRounds = (1 << 18);
+        const int iblock = 3;
+
+        byte[] digest;
+        var data = new byte[(rawPassword.Length + iblock) * noOfRounds];
+
+        //TODO slow code below, find ways to optimize
+        for (var i = 0; i < noOfRounds; i++)
+        {
+            rawPassword.CopyTo(data, i * (rawPassword.Length + iblock));
+
+            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 0] = (byte)i;
+            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 1] = (byte)(i >> 8);
+            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 2] = (byte)(i >> 16);
+
+            if (i % (noOfRounds / EncryptionConstV5.SIZE_INITV) == 0)
+            {
+                digest = msgDigest.ComputeHash(data, 0, (i + 1) * (rawPassword.Length + iblock));
+                aesIV[i / (noOfRounds / EncryptionConstV5.SIZE_INITV)] = digest[19];
+            }
+        }
+        digest = msgDigest.ComputeHash(data);
+        //slow code ends
+
+        var aesKey = new byte[EncryptionConstV5.SIZE_INITV];
+        for (var i = 0; i < 4; i++)
+        {
+            for (var j = 0; j < 4; j++)
+            {
+                aesKey[(i * 4) + j] = (byte)(
+                    (
+                        ((digest[i * 4] * 0x1000000) & 0xff000000)
+                        | (uint)((digest[(i * 4) + 1] * 0x10000) & 0xff0000)
+                        | (uint)((digest[(i * 4) + 2] * 0x100) & 0xff00)
+                        | (uint)(digest[(i * 4) + 3] & 0xff)
+                    ) >> (j * 8)
+                );
+            }
+        }
+
+        var aes = Aes.Create();
+        aes.KeySize = AES_128;
+        aes.Mode = CipherMode.CBC;
+        aes.Padding = PaddingMode.None;
+        aes.Key = aesKey;
+        aes.IV = aesIV;
+        return aes.CreateDecryptor();
+    }
+}

src/SharpCompress/Common/Rar/CryptKey5.cs

@@ -0,0 +1,97 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+using SharpCompress.Common.Rar.Headers;
+
+namespace SharpCompress.Common.Rar;
+
+internal class CryptKey5 : ICryptKey
+{
+    const int AES_256 = 256;
+    const int DERIVED_KEY_LENGTH = 0x10;
+    const int SHA256_DIGEST_SIZE = 32;
+
+    private string _password;
+    private Rar5CryptoInfo _cryptoInfo;
+    private byte[] _pswCheck = { };
+    private byte[] _hashKey = { };
+
+    public CryptKey5(string password, Rar5CryptoInfo rar5CryptoInfo)
+    {
+        _password = password;
+        _cryptoInfo = rar5CryptoInfo;
+    }
+
+    public byte[] PswCheck => _pswCheck;
+
+    public byte[] HashKey => _hashKey;
+
+    private static List<byte[]> GenerateRarPBKDF2Key(
+        string password,
+        byte[] salt,
+        int iterations,
+        int keyLength
+    )
+    {
+        using (HMACSHA256 hmac = new HMACSHA256(Encoding.UTF8.GetBytes(password)))
+        {
+            byte[] block = hmac.ComputeHash(salt);
+            byte[] finalHash = (byte[])block.Clone();
+
+            var loop = new int[] { iterations, 17, 17 };
+            var res = new List<byte[]> { };
+
+            for (int x = 0; x < 3; x++)
+            {
+                for (int i = 1; i < loop[x]; i++)
+                {
+                    block = hmac.ComputeHash(block);
+                    for (int j = 0; j < finalHash.Length; j++)
+                    {
+                        finalHash[j] ^= block[j];
+                    }
+                }
+
+                res.Add((byte[])finalHash.Clone());
+            }
+
+            return res;
+        }
+    }
+
+    public ICryptoTransform Transformer(byte[] salt)
+    {
+        int iterations = (1 << _cryptoInfo.LG2Count); // Adjust the number of iterations as needed
+
+        var salt_rar5 = salt.Concat(new byte[] { 0, 0, 0, 1 });
+        var derivedKey = GenerateRarPBKDF2Key(
+            _password,
+            salt_rar5.ToArray(),
+            iterations,
+            DERIVED_KEY_LENGTH
+        );
+
+        _hashKey = derivedKey[1];
+
+        _pswCheck = new byte[EncryptionConstV5.SIZE_PSWCHECK];
+
+        for (int i = 0; i < SHA256_DIGEST_SIZE; i++)
+        {
+            _pswCheck[i % EncryptionConstV5.SIZE_PSWCHECK] ^= derivedKey[2][i];
+        }
+
+        if (_cryptoInfo.UsePswCheck && !_cryptoInfo.PswCheck.SequenceEqual(_pswCheck))
+        {
+            throw new CryptographicException("The password did not match.");
+        }
+
+        var aes = Aes.Create();
+        aes.KeySize = AES_256;
+        aes.Mode = CipherMode.CBC;
+        aes.Padding = PaddingMode.None;
+        aes.Key = derivedKey[0];
+        aes.IV = _cryptoInfo.InitV;
+        return aes.CreateDecryptor();
+    }
+}

src/SharpCompress/Common/Rar/Headers/ArchiveCryptHeader.cs

@@ -1,50 +1,21 @@
 #nullable disable
 
+using System;
+using System.Security.Cryptography;
+using SharpCompress.Common.Rar.Headers;
 using SharpCompress.IO;
 
 namespace SharpCompress.Common.Rar.Headers;
 
 internal class ArchiveCryptHeader : RarHeader
 {
-    private const int CRYPT_VERSION = 0; // Supported encryption version.
-    private const int SIZE_SALT50 = 16;
-    private const int SIZE_PSWCHECK = 8;
-    private const int SIZE_PSWCHECK_CSUM = 4;
-    private const int CRYPT5_KDF_LG2_COUNT_MAX = 24; // LOG2 of maximum accepted iteration count.
-
-    private bool _usePswCheck;
-    private uint _lg2Count; // Log2 of PBKDF2 repetition count.
-    private byte[] _salt;
-    private byte[] _pswCheck;
-    private byte[] _pswCheckCsm;
-
     public ArchiveCryptHeader(RarHeader header, RarCrcBinaryReader reader)
         : base(header, reader, HeaderType.Crypt) { }
 
+    public Rar5CryptoInfo CryptInfo = new Rar5CryptoInfo();
+
     protected override void ReadFinish(MarkingBinaryReader reader)
     {
-        var cryptVersion = reader.ReadRarVIntUInt32();
-        if (cryptVersion > CRYPT_VERSION)
-        {
-            //error?
-            return;
-        }
-        var encryptionFlags = reader.ReadRarVIntUInt32();
-        _usePswCheck = FlagUtility.HasFlag(encryptionFlags, EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
-        _lg2Count = reader.ReadRarVIntByte(1);
-
-        //UsePswCheck = HasHeaderFlag(EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
-        if (_lg2Count > CRYPT5_KDF_LG2_COUNT_MAX)
-        {
-            //error?
-            return;
-        }
-
-        _salt = reader.ReadBytes(SIZE_SALT50);
-        if (_usePswCheck)
-        {
-            _pswCheck = reader.ReadBytes(SIZE_PSWCHECK);
-            _pswCheckCsm = reader.ReadBytes(SIZE_PSWCHECK_CSUM);
-        }
+        CryptInfo = new Rar5CryptoInfo(reader, false);
     }
 }