key derivation service that pinvokes into CommonCrypto for PBKDF2 key

src/App/Abstractions/Services/IKeyDerivationService.cs

@@ -0,0 +1,7 @@
+namespace Bit.App.Abstractions
+{
+    public interface IKeyDerivationService
+    {
+        byte[] DeriveKey(string password, string salt);
+    }
+}

src/App/App.csproj

@@ -41,6 +41,7 @@
     <Compile Include="Abstractions\Services\IAppIdService.cs" />
     <Compile Include="Abstractions\Services\IAuthService.cs" />
     <Compile Include="Abstractions\Services\IClipboardService.cs" />
+    <Compile Include="Abstractions\Services\IKeyDerivationService.cs" />
     <Compile Include="Abstractions\Services\IReflectionService.cs" />
     <Compile Include="Abstractions\Services\ISiteService.cs" />
     <Compile Include="Abstractions\Services\IFolderService.cs" />

src/iOS/Main.cs

@@ -12,6 +12,8 @@ namespace Bit.iOS
         // This is the main entry point of the application.
         static void Main(string[] args)
         {
+            ObjCRuntime.Dlfcn.dlopen(ObjCRuntime.Constants.libSystemLibrary, 0);
+
             // if you want to use a different Application Delegate class from "AppDelegate"
             // you can specify it here.
             UIApplication.Main(args, null, "AppDelegate");

src/iOS/Services/KeyDerivationService.cs

@@ -0,0 +1,35 @@
+using Bit.App.Abstractions;
+using Foundation;
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace Bit.iOS.Services
+{
+    public class KeyDerivationService : IKeyDerivationService
+    {
+        private const uint PBKDFAlgorithm = 2; // PBKDF2
+        private const uint PseudoRandomAlgorithm = 3; // SHA256
+        private const uint Rounds = 5000;
+
+        public byte[] DeriveKey(string password, string salt)
+        {
+            var passwordData = NSData.FromArray(Encoding.UTF8.GetBytes(password));
+            var saltData = NSData.FromArray(Encoding.UTF8.GetBytes(salt));
+
+            var keyData = new NSMutableData();
+            keyData.Length = 32;
+            var result = CCKeyCerivationPBKDF(PBKDFAlgorithm, passwordData.Bytes, passwordData.Length, saltData.Bytes, 
+                saltData.Length, PseudoRandomAlgorithm, Rounds, keyData.MutableBytes, keyData.Length);
+
+            byte[] keyBytes = new byte[keyData.Length];
+            Marshal.Copy(keyData.Bytes, keyBytes, 0, Convert.ToInt32(keyData.Length));
+            return keyBytes;
+        }
+
+        // ref: http://opensource.apple.com//source/CommonCrypto/CommonCrypto-55010/CommonCrypto/CommonKeyDerivation.h
+        [DllImport(ObjCRuntime.Constants.libSystemLibrary, EntryPoint = "CCKeyDerivationPBKDF")]
+        public extern static int CCKeyCerivationPBKDF(uint algorithm, IntPtr password, nuint passwordLen,
+            IntPtr salt, nuint saltLen, uint prf, nuint rounds, IntPtr derivedKey, nuint derivedKeyLength);
+    }
+}

src/iOS/iOS.csproj

@@ -140,6 +140,7 @@
     <Compile Include="Services\ClipboardService.cs" />
     <Compile Include="Main.cs" />
     <Compile Include="AppDelegate.cs" />
+    <Compile Include="Services\KeyDerivationService.cs" />
     <Compile Include="Services\ReflectionService.cs" />
     <None Include="app.config" />
     <None Include="Entitlements.plist" />