refactor for enc type header and cryptokey

src/App/Abstractions/Services/IAuthService.cs

@@ -14,6 +14,6 @@ namespace Bit.App.Abstractions
 
         void LogOut();
         Task<FullLoginResult> TokenPostAsync(string email, string masterPassword);
-        Task<LoginResult> TokenPostTwoFactorAsync(string token, string email, string masterPasswordHash, byte[] key);
+        Task<LoginResult> TokenPostTwoFactorAsync(string token, string email, string masterPasswordHash, CryptoKey key);
     }
 }

src/App/Abstractions/Services/ICryptoService.cs

@@ -4,16 +4,15 @@ namespace Bit.App.Abstractions
 {
     public interface ICryptoService
     {
-        string Base64Key { get; }
+        CryptoKey Key { get; set; }
-        byte[] Key { get; set; }
+        CryptoKey PreviousKey { get; }
-        byte[] PreviousKey { get; }
         bool KeyChanged { get; }
 
-        string Decrypt(CipherString encyptedValue);
+        string Decrypt(CipherString encyptedValue, CryptoKey key = null);
-        CipherString Encrypt(string plaintextValue);
+        CipherString Encrypt(string plaintextValue, CryptoKey key = null);
-        byte[] MakeKeyFromPassword(string password, string salt);
+        CryptoKey MakeKeyFromPassword(string password, string salt);
         string MakeKeyFromPasswordBase64(string password, string salt);
-        byte[] HashPassword(byte[] key, string password);
+        byte[] HashPassword(CryptoKey key, string password);
-        string HashPasswordBase64(byte[] key, string password);
+        string HashPasswordBase64(CryptoKey key, string password);
     }
 }

src/App/App.csproj

@@ -80,6 +80,7 @@
     <Compile Include="Controls\FormEntryCell.cs" />
     <Compile Include="Controls\PinControl.cs" />
     <Compile Include="Controls\VaultListViewCell.cs" />
+    <Compile Include="Enums\EncryptionType.cs" />
     <Compile Include="Enums\LockType.cs" />
     <Compile Include="Enums\CipherType.cs" />
     <Compile Include="Enums\PushType.cs" />
@@ -108,6 +109,7 @@
     <Compile Include="Models\Api\LoginDataModel.cs" />
     <Compile Include="Models\Cipher.cs" />
     <Compile Include="Models\CipherString.cs" />
+    <Compile Include="Models\CryptoKey.cs" />
     <Compile Include="Models\Data\SettingsData.cs" />
     <Compile Include="Models\Data\FolderData.cs" />
     <Compile Include="Abstractions\IDataObject.cs" />

src/App/Enums/EncryptionType.cs

@@ -0,0 +1,10 @@
+namespace Bit.App.Enums
+{
+    public enum EncryptionType : byte
+    {
+        AesCbc256_B64 = 0,
+        AesCbc128_HmacSha256_B64 = 1,
+        AesCbc256_HmacSha256_B64 = 2,
+        RsaOaep_Sha256_B64 = 3
+    }
+}

src/App/Models/CipherString.cs

@@ -1,6 +1,7 @@
 using System;
 using Bit.App.Abstractions;
 using XLabs.Ioc;
+using Bit.App.Enums;
 
 namespace Bit.App.Models
 {
@@ -15,10 +16,58 @@ namespace Bit.App.Models
                 throw new ArgumentException(nameof(encryptedString));
             }
 
+            var headerPieces = encryptedString.Split('.');
+            string[] encPieces;
+            if(headerPieces.Length == 2 && Enum.TryParse(headerPieces[0], out EncryptionType encType))
+            {
+                EncryptionType = encType;
+                encPieces = headerPieces[1].Split('|');
+            }
+            else if(headerPieces.Length == 1)
+            {
+                encPieces = headerPieces[0].Split('|');
+                EncryptionType = encPieces.Length == 3 ? EncryptionType.AesCbc128_HmacSha256_B64 : EncryptionType.AesCbc256_B64;
+            }
+            else
+            {
+                throw new ArgumentException("Malformed header.");
+            }
+
+            switch(EncryptionType)
+            {
+                case EncryptionType.AesCbc256_B64:
+                    if(encPieces.Length != 2)
+                    {
+                        throw new ArgumentException("Malformed encPieces.");
+                    }
+                    InitializationVector = encPieces[0];
+                    CipherText = encPieces[1];
+                    break;
+                case EncryptionType.AesCbc128_HmacSha256_B64:
+                case EncryptionType.AesCbc256_HmacSha256_B64:
+                    if(encPieces.Length != 3)
+                    {
+                        throw new ArgumentException("Malformed encPieces.");
+                    }
+                    InitializationVector = encPieces[0];
+                    CipherText = encPieces[1];
+                    Mac = encPieces[2];
+                    break;
+                case EncryptionType.RsaOaep_Sha256_B64:
+                    if(encPieces.Length != 1)
+                    {
+                        throw new ArgumentException("Malformed encPieces.");
+                    }
+                    CipherText = encPieces[0];
+                    break;
+                default:
+                    throw new ArgumentException("Unknown encType.");
+            }
+
             EncryptedString = encryptedString;
         }
 
-        public CipherString(string initializationVector, string cipherText, string mac = null)
+        public CipherString(EncryptionType encryptionType, string initializationVector, string cipherText, string mac = null)
         {
             if(string.IsNullOrWhiteSpace(initializationVector))
             {
@@ -30,30 +79,24 @@ namespace Bit.App.Models
                 throw new ArgumentNullException(nameof(cipherText));
             }
 
-            EncryptedString = string.Format("{0}|{1}", initializationVector, cipherText);
+            EncryptionType = encryptionType;
+            EncryptedString = string.Format("{0}.{1}|{2}", (byte)encryptionType, initializationVector, cipherText);
 
             if(!string.IsNullOrWhiteSpace(mac))
             {
                 EncryptedString = string.Format("{0}|{1}", EncryptedString, mac);
             }
+
+            CipherText = cipherText;
+            InitializationVector = initializationVector;
+            Mac = mac;
         }
 
+        public EncryptionType EncryptionType { get; private set; }
         public string EncryptedString { get; private set; }
-        public string InitializationVector => EncryptedString?.Split('|')[0] ?? null;
+        public string InitializationVector { get; private set; }
-        public string CipherText => EncryptedString?.Split('|')[1] ?? null;
+        public string CipherText { get; private set; }
-        public string Mac
+        public string Mac { get; private set; }
-        {
-            get
-            {
-                var pieces = EncryptedString?.Split('|') ?? new string[0];
-                if(pieces.Length > 2)
-                {
-                    return pieces[2];
-                }
-
-                return null;
-            }
-        }
         public byte[] InitializationVectorBytes => Convert.FromBase64String(InitializationVector);
         public byte[] CipherTextBytes => Convert.FromBase64String(CipherText);
         public byte[] MacBytes => Mac == null ? null : Convert.FromBase64String(Mac);

src/App/Models/CryptoKey.cs

@@ -0,0 +1,62 @@
+using Bit.App.Enums;
+using System;
+using System.Linq;
+
+namespace Bit.App.Models
+{
+    public class CryptoKey
+    {
+        public CryptoKey(byte[] rawBytes, EncryptionType? encType = null)
+        {
+            if(rawBytes == null || rawBytes.Length == 0)
+            {
+                throw new Exception("Must provide keyBytes.");
+            }
+
+            if(encType == null)
+            {
+                if(rawBytes.Length == 32)
+                {
+                    encType = EncryptionType.AesCbc256_B64;
+                }
+                else if(rawBytes.Length == 64)
+                {
+                    encType = EncryptionType.AesCbc256_HmacSha256_B64;
+                }
+                else
+                {
+                    throw new Exception("Unable to determine encType.");
+                }
+            }
+
+            EncryptionType = encType.Value;
+            Key = rawBytes;
+
+            if(EncryptionType == EncryptionType.AesCbc256_B64 && Key.Length == 32)
+            {
+                EncKey = Key;
+                MacKey = null;
+            }
+            else if(EncryptionType == EncryptionType.AesCbc128_HmacSha256_B64 && Key.Length == 32)
+            {
+                EncKey = Key.Take(16).ToArray();
+                MacKey = Key.Skip(16).Take(16).ToArray();
+            }
+            else if(EncryptionType == EncryptionType.AesCbc256_HmacSha256_B64 && Key.Length == 64)
+            {
+                EncKey = Key.Take(32).ToArray();
+                MacKey = Key.Skip(32).Take(32).ToArray();
+            }
+            else
+            {
+                throw new Exception("Unsupported encType/key length.");
+            }
+        }
+
+        public byte[] Key { get; set; }
+        public string B64Key => Convert.ToBase64String(Key);
+        public byte[] EncKey { get; set; }
+        public byte[] MacKey { get; set; }
+        public EncryptionType EncryptionType { get; set; }
+    }
+}

src/App/Models/LoginResult.cs

@@ -9,7 +9,7 @@
     public class FullLoginResult : LoginResult
     {
         public bool TwoFactorRequired { get; set; }
-        public byte[] Key { get; set; }
+        public CryptoKey Key { get; set; }
         public string MasterPasswordHash { get; set; }
     }
 }

src/App/Pages/Lock/LockPasswordPage.cs

@@ -120,7 +120,7 @@ namespace Bit.App.Pages
             }
 
             var key = _cryptoService.MakeKeyFromPassword(PasswordCell.Entry.Text, _authService.Email);
-            if(key.SequenceEqual(_cryptoService.Key))
+            if(key.Key.SequenceEqual(_cryptoService.Key.Key))
             {
                 _settings.AddOrUpdateValue(Constants.Locked, false);
                 await Navigation.PopModalAsync();

src/App/Pages/LoginTwoFactorPage.cs

@@ -7,6 +7,7 @@ using XLabs.Ioc;
 using Acr.UserDialogs;
 using System.Threading.Tasks;
 using PushNotification.Plugin.Abstractions;
+using Bit.App.Models;
 
 namespace Bit.App.Pages
 {
@@ -19,9 +20,9 @@ namespace Bit.App.Pages
         private IPushNotification _pushNotification;
         private readonly string _email;
         private readonly string _masterPasswordHash;
-        private readonly byte[] _key;
+        private readonly CryptoKey _key;
 
-        public LoginTwoFactorPage(string email, string masterPasswordHash, byte[] key)
+        public LoginTwoFactorPage(string email, string masterPasswordHash, CryptoKey key)
             : base(updateActivity: false)
         {
             _email = email;

src/App/Services/AuthService.cs

@@ -6,8 +6,6 @@ using Bit.App.Models.Api;
 using Plugin.Settings.Abstractions;
 using Bit.App.Models;
 using System.Linq;
-using Xamarin.Forms;
-using PushNotification.Plugin.Abstractions;
 
 namespace Bit.App.Services
 {
@@ -237,7 +235,7 @@ namespace Bit.App.Services
         }
 
         public async Task<LoginResult> TokenPostTwoFactorAsync(string token, string email, string masterPasswordHash,
-            byte[] key)
+            CryptoKey key)
         {
             var result = new LoginResult();
 
@@ -263,7 +261,7 @@ namespace Bit.App.Services
             return result;
         }
 
-        private void ProcessLoginSuccess(byte[] key, TokenResponse response)
+        private void ProcessLoginSuccess(CryptoKey key, TokenResponse response)
         {
             _cryptoService.Key = key;
             _tokenService.Token = response.AccessToken;

src/App/Services/CryptoService.cs

@@ -5,7 +5,6 @@ using Bit.App.Abstractions;
 using Bit.App.Models;
 using PCLCrypto;
 using System.Linq;
-using Xamarin.Forms;
 
 namespace Bit.App.Services
 {
@@ -17,8 +16,9 @@ namespace Bit.App.Services
 
         private readonly ISecureStorageService _secureStorage;
         private readonly IKeyDerivationService _keyDerivationService;
-        private byte[] _key;
+        private CryptoKey _key;
-        private byte[] _previousKey;
+        private CryptoKey _legacyEtmKey;
+        private CryptoKey _previousKey;
 
         public CryptoService(
             ISecureStorageService secureStorage,
@@ -28,13 +28,13 @@ namespace Bit.App.Services
             _keyDerivationService = keyDerivationService;
         }
 
-        public byte[] Key
+        public CryptoKey Key
         {
             get
             {
                 if(_key == null)
                 {
-                    _key = _secureStorage.Retrieve(KeyKey);
+                    _key = new CryptoKey(_secureStorage.Retrieve(KeyKey));
                 }
 
                 return _key;
@@ -43,37 +43,25 @@ namespace Bit.App.Services
             {
                 if(value != null)
                 {
-                    _secureStorage.Store(KeyKey, value);
+                    _secureStorage.Store(KeyKey, value.Key);
                 }
                 else
                 {
                     PreviousKey = _key;
                     _secureStorage.Delete(KeyKey);
                     _key = null;
+                    _legacyEtmKey = null;
                 }
             }
         }
 
-        public string Base64Key
+        public CryptoKey PreviousKey
-        {
-            get
-            {
-                if(Key == null)
-                {
-                    return null;
-                }
-
-                return Convert.ToBase64String(Key);
-            }
-        }
-
-        public byte[] PreviousKey
         {
             get
             {
                 if(_previousKey == null)
                 {
-                    _previousKey = _secureStorage.Retrieve(PreviousKeyKey);
+                    _previousKey = new CryptoKey(_secureStorage.Retrieve(PreviousKeyKey));
                 }
 
                 return _previousKey;
@@ -82,7 +70,7 @@ namespace Bit.App.Services
             {
                 if(value != null)
                 {
-                    _secureStorage.Store(PreviousKeyKey, value);
+                    _secureStorage.Store(PreviousKeyKey, value.Key);
                     _previousKey = value;
                 }
             }
@@ -102,18 +90,20 @@ namespace Bit.App.Services
                     return Key != null;
                 }
 
-                return !PreviousKey.SequenceEqual(Key);
+                return !PreviousKey.Key.SequenceEqual(Key.Key);
             }
         }
 
-        public byte[] EncKey => Key?.Take(16).ToArray();
+        public CipherString Encrypt(string plaintextValue, CryptoKey key = null)
-        public byte[] MacKey => Key?.Skip(16).Take(16).ToArray();
-
-        public CipherString Encrypt(string plaintextValue)
         {
-            if(Key == null)
+            if(key == null)
             {
-                throw new ArgumentNullException(nameof(Key));
+                key = Key;
+            }
+
+            if(key == null)
+            {
+                throw new ArgumentNullException(nameof(key));
             }
 
             if(plaintextValue == null)
@@ -124,23 +114,26 @@ namespace Bit.App.Services
             var plaintextBytes = Encoding.UTF8.GetBytes(plaintextValue);
 
             var provider = WinRTCrypto.SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithm.AesCbcPkcs7);
-            // TODO: Turn on whenever ready to support encrypt-then-mac
+            var cryptoKey = provider.CreateSymmetricKey(key.EncKey);
-            var cryptoKey = provider.CreateSymmetricKey(true ? EncKey : Key);
             var iv = WinRTCrypto.CryptographicBuffer.GenerateRandom(provider.BlockLength);
             var encryptedBytes = WinRTCrypto.CryptographicEngine.Encrypt(cryptoKey, plaintextBytes, iv);
-            // TODO: Turn on whenever ready to support encrypt-then-mac
+            var mac = key.MacKey != null ? ComputeMac(encryptedBytes, iv, key.MacKey) : null;
-            var mac = true ? ComputeMac(encryptedBytes, iv) : null;
 
-            return new CipherString(Convert.ToBase64String(iv), Convert.ToBase64String(encryptedBytes), mac);
+            return new CipherString(key.EncryptionType, Convert.ToBase64String(iv), Convert.ToBase64String(encryptedBytes), mac);
         }
 
-        public string Decrypt(CipherString encyptedValue)
+        public string Decrypt(CipherString encyptedValue, CryptoKey key = null)
         {
             try
             {
-                if(Key == null)
+                if(key == null)
                 {
-                    throw new ArgumentNullException(nameof(Key));
+                    key = Key;
+                }
+
+                if(key == null)
+                {
+                    throw new ArgumentNullException(nameof(key));
                 }
 
                 if(encyptedValue == null)
@@ -148,9 +141,27 @@ namespace Bit.App.Services
                     throw new ArgumentNullException(nameof(encyptedValue));
                 }
 
-                if(encyptedValue.Mac != null)
+                if(encyptedValue.EncryptionType == Enums.EncryptionType.AesCbc128_HmacSha256_B64 &&
+                    key.EncryptionType == Enums.EncryptionType.AesCbc256_B64)
                 {
-                    var computedMac = ComputeMac(encyptedValue.CipherTextBytes, encyptedValue.InitializationVectorBytes);
+                    // Old encrypt-then-mac scheme, swap out the key
+                    if(_legacyEtmKey == null)
+                    {
+                        _legacyEtmKey = new CryptoKey(key.Key, Enums.EncryptionType.AesCbc128_HmacSha256_B64);
+                    }
+
+                    key = _legacyEtmKey;
+                }
+
+                if(encyptedValue.EncryptionType != key.EncryptionType)
+                {
+                    throw new ArgumentException("encType unavailable.");
+                }
+
+                if(key.MacKey != null && !string.IsNullOrWhiteSpace(encyptedValue.Mac))
+                {
+                    var computedMac = ComputeMac(encyptedValue.CipherTextBytes,
+                        encyptedValue.InitializationVectorBytes, key.MacKey);
                     if(computedMac != encyptedValue.Mac)
                     {
                         throw new InvalidOperationException("MAC failed.");
@@ -158,7 +169,7 @@ namespace Bit.App.Services
                 }
 
                 var provider = WinRTCrypto.SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithm.AesCbcPkcs7);
-                var cryptoKey = provider.CreateSymmetricKey(encyptedValue.Mac != null ? EncKey : Key);
+                var cryptoKey = provider.CreateSymmetricKey(key.EncKey);
                 var decryptedBytes = WinRTCrypto.CryptographicEngine.Decrypt(cryptoKey, encyptedValue.CipherTextBytes,
                     encyptedValue.InitializationVectorBytes);
                 return Encoding.UTF8.GetString(decryptedBytes, 0, decryptedBytes.Length).TrimEnd('\0');
@@ -170,11 +181,11 @@ namespace Bit.App.Services
             }
         }
 
-        private string ComputeMac(byte[] ctBytes, byte[] ivBytes)
+        private string ComputeMac(byte[] ctBytes, byte[] ivBytes, byte[] macKey)
         {
-            if(MacKey == null)
+            if(macKey == null)
             {
-                throw new ArgumentNullException(nameof(MacKey));
+                throw new ArgumentNullException(nameof(macKey));
             }
 
             if(ctBytes == null)
@@ -188,13 +199,13 @@ namespace Bit.App.Services
             }
 
             var algorithm = WinRTCrypto.MacAlgorithmProvider.OpenAlgorithm(MacAlgorithm.HmacSha256);
-            var hasher = algorithm.CreateHash(MacKey);
+            var hasher = algorithm.CreateHash(macKey);
             hasher.Append(ivBytes.Concat(ctBytes).ToArray());
             var mac = hasher.GetValueAndReset();
             return Convert.ToBase64String(mac);
         }
 
-        public byte[] MakeKeyFromPassword(string password, string salt)
+        public CryptoKey MakeKeyFromPassword(string password, string salt)
         {
             if(password == null)
             {
@@ -209,17 +220,17 @@ namespace Bit.App.Services
             var passwordBytes = Encoding.UTF8.GetBytes(password);
             var saltBytes = Encoding.UTF8.GetBytes(salt);
 
-            var key = _keyDerivationService.DeriveKey(passwordBytes, saltBytes, 5000);
+            var keyBytes = _keyDerivationService.DeriveKey(passwordBytes, saltBytes, 5000);
-            return key;
+            return new CryptoKey(keyBytes);
         }
 
         public string MakeKeyFromPasswordBase64(string password, string salt)
         {
             var key = MakeKeyFromPassword(password, salt);
-            return Convert.ToBase64String(key);
+            return Convert.ToBase64String(key.Key);
         }
 
-        public byte[] HashPassword(byte[] key, string password)
+        public byte[] HashPassword(CryptoKey key, string password)
         {
             if(key == null)
             {
@@ -232,11 +243,11 @@ namespace Bit.App.Services
             }
 
             var passwordBytes = Encoding.UTF8.GetBytes(password);
-            var hash = _keyDerivationService.DeriveKey(key, passwordBytes, 1);
+            var hash = _keyDerivationService.DeriveKey(key.Key, passwordBytes, 1);
             return hash;
         }
 
-        public string HashPasswordBase64(byte[] key, string password)
+        public string HashPasswordBase64(CryptoKey key, string password)
         {
             var hash = HashPassword(key, password);
             return Convert.ToBase64String(hash);