Fixed license validation for .NET Core under Linux and MacOS (#269)

Author: ivaylokenov

src/MyTested.AspNetCore.Mvc.Licensing/CryptographyHelpers.cs

@@ -0,0 +1,96 @@
+#if NETSTANDARD1_4
+namespace MyTested.AspNetCore.Mvc.Licensing
+{
+    using System;
+    using System.IO;
+    using System.Security.Cryptography;
+
+    public static class CryptographyHelpers
+    {
+        private const int ALG_TYPE_RSA = (2 << 9);
+        private const int ALG_CLASS_KEY_EXCHANGE = (5 << 13);
+        private const int CALG_RSA_KEYX = (ALG_CLASS_KEY_EXCHANGE | ALG_TYPE_RSA | 0);
+
+        internal static RSAParameters ToRSAParameters(this byte[] cspBlob, bool includePrivateParameters)
+        {
+            BinaryReader br = new BinaryReader(new MemoryStream(cspBlob));
+
+            byte bType = br.ReadByte(); // BLOBHEADER.bType: Expected to be 0x6 (PUBLICKEYBLOB) or 0x7 (PRIVATEKEYBLOB), though there's no check for backward compat reasons. 
+            byte bVersion = br.ReadByte(); // BLOBHEADER.bVersion: Expected to be 0x2, though there's no check for backward compat reasons.
+            br.ReadUInt16(); // BLOBHEADER.wReserved
+            int algId = br.ReadInt32(); // BLOBHEADER.aiKeyAlg
+            if (algId != CALG_RSA_KEYX)
+                throw new PlatformNotSupportedException(); // The FCall this code was ported from supports other algid's but we're only porting what we use.
+
+            int magic = br.ReadInt32(); // RSAPubKey.magic: Expected to be 0x31415352 ('RSA1') or 0x32415352 ('RSA2') 
+            int bitLen = br.ReadInt32(); // RSAPubKey.bitLen
+
+            int modulusLength = bitLen / 8;
+            int halfModulusLength = (modulusLength + 1) / 2;
+
+            uint expAsDword = br.ReadUInt32();
+
+            RSAParameters rsaParameters = new RSAParameters();
+            rsaParameters.Exponent = ExponentAsBytes(expAsDword);
+            rsaParameters.Modulus = br.ReadReversed(modulusLength);
+            if (includePrivateParameters)
+            {
+                rsaParameters.P = br.ReadReversed(halfModulusLength);
+                rsaParameters.Q = br.ReadReversed(halfModulusLength);
+                rsaParameters.DP = br.ReadReversed(halfModulusLength);
+                rsaParameters.DQ = br.ReadReversed(halfModulusLength);
+                rsaParameters.InverseQ = br.ReadReversed(halfModulusLength);
+                rsaParameters.D = br.ReadReversed(modulusLength);
+            }
+
+            return rsaParameters;
+        }
+
+        /// <summary>
+        /// Helper for converting a UInt32 exponent to bytes.
+        /// </summary>
+        private static byte[] ExponentAsBytes(uint exponent)
+        {
+            if (exponent <= 0xFF)
+            {
+                return new[] { (byte)exponent };
+            }
+            if (exponent <= 0xFFFF)
+            {
+                return new[]
+                {
+                    (byte) (exponent >> 8),
+                    (byte) (exponent)
+                };
+            }
+            if (exponent <= 0xFFFFFF)
+            {
+                return new[]
+                {
+                    (byte) (exponent >> 16),
+                    (byte) (exponent >> 8),
+                    (byte) (exponent)
+                };
+            }
+
+            return new[]
+            {
+                (byte) (exponent >> 24),
+                (byte) (exponent >> 16),
+                (byte) (exponent >> 8),
+                (byte) (exponent)
+            };
+        }
+
+        /// <summary>
+        /// Read in a byte array in reverse order.
+        /// </summary>
+        private static byte[] ReadReversed(this BinaryReader br, int count)
+        {
+            byte[] data = br.ReadBytes(count);
+            Array.Reverse(data);
+            return data;
+        }
+    }
+}
+#endif

src/MyTested.AspNetCore.Mvc.Licensing/LicenseValidator.cs

@@ -40,7 +40,7 @@ public static bool Validate(IEnumerable<string> licenses, DateTime releaseDate,
 
             return true;
         }
-        
+
         public static IEnumerable<LicenseDetails> GetLicenseDetails()
         {
             if (registeredLicenses == null || !registeredLicenses.Any())
@@ -135,18 +135,29 @@ private static void Validate(string license, DateTime releaseDate, string projec
             };
 
             var parsedSigningData = licenseDetails.GetSignificateData();
+
+            var signingData = new byte[SigningDataLength];
+            Array.Copy(licenseAsBytes, signingData, SigningDataLength);
 
+#if NETSTANDARD1_4
+            var cryptoProvider = RSA.Create();
+            cryptoProvider.KeySize = 1024;
+
+            var parameters = CryptographyHelpers.ToRSAParameters(Convert.FromBase64String(PublicKey), false);
+            cryptoProvider.ImportParameters(parameters);
+
+            var dataVerified = cryptoProvider.VerifyData(parsedSigningData, signingData, HashAlgorithmName.SHA1, RSASignaturePadding.Pkcs1);
+#else
             var cryptoProvider = new RSACryptoServiceProvider(1024)
             {
                 PersistKeyInCsp = false
             };
 
             cryptoProvider.ImportCspBlob(Convert.FromBase64String(PublicKey));
 
-            var signingData = new byte[SigningDataLength];
-            Array.Copy(licenseAsBytes, signingData, SigningDataLength);
-
-            if (!cryptoProvider.VerifyData(parsedSigningData, SHA1.Create(), signingData))
+            var dataVerified = cryptoProvider.VerifyData(parsedSigningData, SHA1.Create(), signingData);
+#endif
+            if (!dataVerified)
             {
                 throw new InvalidLicenseException("License text does not match signature");
             }