Add and use TpmSanEncoder

Author: iamcarbon

Test/Asn1Tests.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Formats.Asn1;
 using System.Linq;
+using System.Security.Cryptography;
 using System.Text;
 
 using Fido2NetLib;
@@ -11,6 +12,16 @@ namespace Test
 {
     public class Asn1Tests
     {
+        [Fact]
+        public void EncodeTpmSan()
+        {
+            Assert.Equal("MG2kazBpMRYwFAYFZ4EFAgEMC2lkOkZGRkZGMUQwMTcwNQYFZ4EFAgIMLEZJRE8yLU5FVC1MSUItVGVzdFRQTUFpa0NlcnRTQU5UQ0dDb25mb3JtYW50MRYwFAYFZ4EFAgMMC2lkOkYxRDAwMDAy", Convert.ToBase64String(TpmSanEncoder.Encode(
+                ( new Oid("2.23.133.2.1"), "id:FFFFF1D0" ),
+                ( new Oid("2.23.133.2.2"), "FIDO2-NET-LIB-TestTPMAikCertSANTCGConformant" ),
+                ( new Oid("2.23.133.2.3"), "id:F1D00002")
+            )));
+        }
+
         [Fact]
         public void DecodeObjectIdentifierAsOctetString()
         {

Test/Attestation/Tpm.cs

@@ -45,15 +45,11 @@ public Tpm()
                 },
                 false);
 
-
-            var tpmManufacturer = AsnElt.Make(AsnElt.SEQUENCE, new AsnElt[] { AsnElt.MakeOID("2.23.133.2.1"), AsnElt.MakeString(AsnElt.UTF8String, "id:FFFFF1D0") });
-            var tpmModel = AsnElt.Make(AsnElt.SEQUENCE, new AsnElt[] { AsnElt.MakeOID("2.23.133.2.2"), AsnElt.MakeString(AsnElt.UTF8String, "FIDO2-NET-LIB-TEST-TPM") });
-            var tpmVersion = AsnElt.Make(AsnElt.SEQUENCE, new AsnElt[] { AsnElt.MakeOID("2.23.133.2.3"), AsnElt.MakeString(AsnElt.UTF8String, "id:F1D00002") });
-            var tpmDeviceAttributes = AsnElt.Make(AsnElt.SET, new AsnElt[] { tpmManufacturer, tpmModel, tpmVersion });
-            var tpmDirectoryName = AsnElt.Make(AsnElt.SEQUENCE, tpmDeviceAttributes);
-            var tpmGeneralName = AsnElt.MakeExplicit(AsnElt.OCTET_STRING, tpmDirectoryName);
-            var tpmSAN = AsnElt.Make(AsnElt.SEQUENCE, tpmGeneralName);
-            var asnEncodedSAN = tpmSAN.Encode();
+            byte[] asnEncodedSAN = TpmSanEncoder.Encode(
+                manufacturer : "id:FFFFF1D0", 
+                model        : "FIDO2-NET-LIB-TEST-TPM",
+                version      : "id:F1D00002"
+            );
 
             aikCertSanExt = new X509Extension(
                 "2.5.29.17",
@@ -382,17 +378,11 @@ public void TestTPMAikCertSANTCGConformant()
 
                     attRequest.CertificateExtensions.Add(idFidoGenCeAaguidExt);
 
-                    var tcpaTpmManufacturer = AsnElt.Make(AsnElt.SEQUENCE, new AsnElt[] { AsnElt.MakeOID("2.23.133.2.1"), AsnElt.MakeString(AsnElt.UTF8String, "id:FFFFF1D0") });
-                    var tcpaTpmModel = AsnElt.Make(AsnElt.SEQUENCE, new AsnElt[] { AsnElt.MakeOID("2.23.133.2.2"), AsnElt.MakeString(AsnElt.UTF8String, "FIDO2-NET-LIB-TestTPMAikCertSANTCGConformant") });
-                    var tcpaTpmVersion = AsnElt.Make(AsnElt.SEQUENCE, new AsnElt[] { AsnElt.MakeOID("2.23.133.2.3"), AsnElt.MakeString(AsnElt.UTF8String, "id:F1D00002") });
-                    var asnEncodedSAN = AsnElt.Make(AsnElt.SEQUENCE, new AsnElt[] {
-                AsnElt.Make(AsnElt.CONTEXT, AsnElt.OCTET_STRING, AsnElt.Make(
-                    AsnElt.SEQUENCE, new AsnElt[] {
-                        AsnElt.Make(AsnElt.SET, tcpaTpmManufacturer),
-                        AsnElt.Make(AsnElt.SET, tcpaTpmModel),
-                        AsnElt.Make(AsnElt.SET, tcpaTpmVersion)
-                    })
-                )}).Encode();
+                    byte[] asnEncodedSAN = TpmSanEncoder.Encode(
+                        manufacturer : "id:FFFFF1D0",
+                        model        : "FIDO2-NET-LIB-TestTPMAikCertSANTCGConformant",
+                        version      : "id:F1D00002"
+                    );
 
                     var aikCertSanExt = new X509Extension(
                         "2.5.29.17",
@@ -662,11 +652,8 @@ public void TestTPMSigNotByteString()
                     var attRequest = new CertificateRequest(attDN, rsaAtt, HashAlgorithmName.SHA256, padding);
 
                     attRequest.CertificateExtensions.Add(notCAExt);
-
                     attRequest.CertificateExtensions.Add(idFidoGenCeAaguidExt);
-
                     attRequest.CertificateExtensions.Add(aikCertSanExt);
-
                     attRequest.CertificateExtensions.Add(tcgKpAIKCertExt);
 
                     var serial = new byte[12];
@@ -694,7 +681,6 @@ public void TestTPMSigNotByteString()
 
                     _credentialPublicKey = new CredentialPublicKey(cpk);
 
-
                     unique = rsaparams.Modulus;
                     exponent = rsaparams.Exponent;
 

Test/Extensions/TpmSanEncoder.cs

@@ -0,0 +1,53 @@
+using System.Formats.Asn1;
+using System.Security.Cryptography;
+
+namespace Test
+{
+    internal static class TpmSanEncoder
+    {
+        internal static class Oids
+        {
+            public static readonly Oid Manufacturer = new ("2.23.133.2.1");
+            public static readonly Oid Model        = new ("2.23.133.2.2");
+            public static readonly Oid Version      = new ("2.23.133.2.3");
+        }
+
+        public static byte[] Encode(string manufacturer, string model, string version)
+        {
+            return Encode(
+                (Oids.Manufacturer, manufacturer),
+                (Oids.Model, model),
+                (Oids.Version, version)
+            );
+        }
+
+        public static byte[] Encode(params (Oid, string)[] items)
+        {
+            var writer = new AsnWriter(AsnEncodingRules.BER);
+
+            using (writer.PushSequence())
+            using (writer.PushSequence(new Asn1Tag(TagClass.ContextSpecific, 4, true)))
+            {
+                using (writer.PushSequence())
+                {
+                    foreach ((Oid oid, string value) in items)
+                    {
+                        WriteSet(writer, oid, value);
+                    }
+                }
+            }
+
+            return writer.Encode();
+        }
+
+        private static void WriteSet(AsnWriter writer, Oid oid, string text)
+        {
+            using (writer.PushSetOf())
+            using (writer.PushSequence())
+            {
+                writer.WriteObjectIdentifier(oid.Value);
+                writer.WriteCharacterString(UniversalTagNumber.UTF8String, text);
+            }
+        }
+    }
+}