Dotnet Core support

1 files changed, 78 insertions, 0 deletions

diff --git a/TwoStepsAuthenticator.DotnetCore/Authenticator.cs b/TwoStepsAuthenticator.DotnetCore/Authenticator.cs
new file mode 100644
index 0000000..95ce955
--- /dev/null
+++ b/TwoStepsAuthenticator.DotnetCore/Authenticator.cs
@@ -0,0 +1,78 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TwoStepsAuthenticator
+{
+    public abstract class Authenticator
+    {
+#if CORE
+        private static readonly RandomNumberGenerator Random = RandomNumberGenerator.Create(); 
+#else
+        private static readonly RNGCryptoServiceProvider Random = new RNGCryptoServiceProvider();
+#endif
+        private static readonly int KeyLength = 16;
+        private static readonly string AvailableKeyChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+
+        public static string GenerateKey() {
+            var keyChars = new char[KeyLength];
+            for (int i = 0; i < keyChars.Length; i++) {
+                keyChars[i] = AvailableKeyChars[RandomInt(AvailableKeyChars.Length)];
+            }
+            return new String(keyChars);
+        }
+
+        protected string GetCodeInternal(string secret, ulong challengeValue) {
+            ulong chlg = challengeValue;
+            byte[] challenge = new byte[8];
+            for (int j = 7; j >= 0; j--) {
+                challenge[j] = (byte)((int)chlg & 0xff);
+                chlg >>= 8;
+            }
+
+            var key = Base32Encoding.ToBytes(secret);
+            for (int i = secret.Length; i < key.Length; i++) {
+                key[i] = 0;
+            }
+
+            HMACSHA1 mac = new HMACSHA1(key);
+            var hash = mac.ComputeHash(challenge);
+
+            int offset = hash[hash.Length - 1] & 0xf;
+
+            int truncatedHash = 0;
+            for (int j = 0; j < 4; j++) {
+                truncatedHash <<= 8;
+                truncatedHash |= hash[offset + j];
+            }
+
+            truncatedHash &= 0x7FFFFFFF;
+            truncatedHash %= 1000000;
+
+            string code = truncatedHash.ToString();
+            return code.PadLeft(6, '0');
+        }
+
+        protected bool ConstantTimeEquals(string a, string b) {
+            uint diff = (uint)a.Length ^ (uint)b.Length;
+
+            for (int i = 0; i < a.Length && i < b.Length; i++) {
+                diff |= (uint)a[i] ^ (uint)b[i];
+            }
+
+            return diff == 0;
+        }
+
+        protected static int RandomInt(int max) {
+            var randomBytes = new byte[4];
+            Random.GetBytes(randomBytes);
+
+            return Math.Abs((int)BitConverter.ToUInt32(randomBytes, 0) % max);
+        }
+
+
+    }
+}