Merge pull request #37 from Mastercard/fix/tag-length

Fix RSA parameter lengths

Author: joseph-neeraj

Mastercard.Developer.ClientEncryption.Core/Utils/RsaKeyUtils.cs

@@ -148,14 +148,31 @@ private static RSA ReadPkcs1Key(byte[] pkcs1Bytes)
                     throw new ArgumentException("Failed to parse PKCS#1 key, 0x00 was expected!");
                 }
 
+                byte[] padded(byte[] array, int totalLength)
+                {
+                    var currentLength = array.Length;
+                    if(currentLength >= totalLength) {
+                        return array;
+                    }
+
+                    var paddedArray = new byte[totalLength];
+                    Array.Copy(array, 0, paddedArray, totalLength - currentLength, currentLength);
+
+                    return paddedArray;
+                }
+
                 var modulus = reader.ReadBytes(GetIntegerSize(reader));
+                
+                var modulusLength = modulus.Length;
+                var modulusHalfLength = (modulus.Length + 1) / 2; // half length rounded up
+
                 var publicExponent = reader.ReadBytes(GetIntegerSize(reader));
-                var privateExponent = reader.ReadBytes(GetIntegerSize(reader));
-                var prime1 = reader.ReadBytes(GetIntegerSize(reader));
-                var prime2 = reader.ReadBytes(GetIntegerSize(reader));
-                var exponent1 = reader.ReadBytes(GetIntegerSize(reader));
-                var exponent2 = reader.ReadBytes(GetIntegerSize(reader));
-                var coefficient = reader.ReadBytes(GetIntegerSize(reader));
+                var privateExponent = padded(reader.ReadBytes(GetIntegerSize(reader)), modulusLength);
+                var prime1 = padded(reader.ReadBytes(GetIntegerSize(reader)), modulusHalfLength);
+                var prime2 = padded(reader.ReadBytes(GetIntegerSize(reader)), modulusHalfLength);
+                var exponent1 = padded(reader.ReadBytes(GetIntegerSize(reader)), modulusHalfLength);
+                var exponent2 = padded(reader.ReadBytes(GetIntegerSize(reader)), modulusHalfLength);
+                var coefficient = padded(reader.ReadBytes(GetIntegerSize(reader)), modulusHalfLength);
 
                 var rsa = CreateRsa();
                 rsa.ImportParameters(new RSAParameters

Mastercard.Developer.ClientEncryption.Tests/Mastercard.Developer.ClientEncryption.Tests.csproj

@@ -68,6 +68,10 @@
       <Link>_Resources\Keys\Pkcs1\test_key_pkcs1-2048.pem</Link>
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </EmbeddedResource>
+	<EmbeddedResource Include=".\Tests\_Resources\Keys\Pkcs1\test_key_pkcs1-2048_uneven_length.pem">
+	  <Link>_Resources\Keys\Pkcs1\test_key_pkcs1-2048_uneven_length.pem</Link>
+	  <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+	</EmbeddedResource>
     <EmbeddedResource Include=".\Tests\_Resources\Keys\Pkcs1\test_key_pkcs1-4096.pem">
       <Link>_Resources\Keys\Pkcs1\test_key_pkcs1-4096.pem</Link>
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>

Mastercard.Developer.ClientEncryption.Tests/Tests/Utils/RsaKeyUtilsTest.cs

@@ -44,6 +44,7 @@ public void TestReadPrivateKeyFile(string keyPath, int expectedKeySize)
         [DataRow("./_Resources/Keys/Pkcs1/test_key_pkcs1-512.pem", 512)]
         [DataRow("./_Resources/Keys/Pkcs1/test_key_pkcs1-1024.pem", 1024)]
         [DataRow("./_Resources/Keys/Pkcs1/test_key_pkcs1-2048.pem", 2048)]
+        [DataRow("./_Resources/Keys/Pkcs1/test_key_pkcs1-2048_uneven_length.pem", 2048)]
         [DataRow("./_Resources/Keys/Pkcs1/test_key_pkcs1-4096.pem", 4096)]
         public void TestReadPrivateKey(string keyPath, int expectedKeySize)
         {

Mastercard.Developer.ClientEncryption.Tests/Tests/_Resources/Keys/Pkcs1/test_key_pkcs1-2048_uneven_length.pem

@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----