Revert "Simplify parsing of RSA COSE public keys"

This reverts commit f207b27.

Author: emlun

webauthn-server-core/src/main/java/com/yubico/webauthn/WebAuthnCodecs.java

@@ -31,11 +31,13 @@
 import com.yubico.webauthn.data.ByteArray;
 import com.yubico.webauthn.data.COSEAlgorithmIdentifier;
 import java.io.IOException;
+import java.math.BigInteger;
 import java.security.KeyFactory;
 import java.security.NoSuchAlgorithmException;
 import java.security.PublicKey;
 import java.security.interfaces.ECPublicKey;
 import java.security.spec.InvalidKeySpecException;
+import java.security.spec.RSAPublicKeySpec;
 import java.security.spec.X509EncodedKeySpec;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -123,17 +125,29 @@ static PublicKey importCosePublicKey(ByteArray key)
     final int kty = cose.get(CBORObject.FromObject(1)).AsInt32();
     switch (kty) {
       case 1:
-        // COSE-JAVA is hardcoded to ed25519-java provider ("EdDSA") which would require an
-        // additional dependency to parse EdDSA keys via the OneKey constructor
         return importCoseEdDsaPublicKey(cose);
-      case 2: // Fall through
+      case 2:
+        return importCoseP256PublicKey(cose);
       case 3:
-        return new OneKey(cose).AsPublicKey();
+        return importCoseRsaPublicKey(cose);
       default:
         throw new IllegalArgumentException("Unsupported key type: " + kty);
     }
   }
 
+  private static PublicKey importCoseRsaPublicKey(CBORObject cose)
+      throws NoSuchAlgorithmException, InvalidKeySpecException {
+    RSAPublicKeySpec spec =
+        new RSAPublicKeySpec(
+            new BigInteger(1, cose.get(CBORObject.FromObject(-1)).GetByteString()),
+            new BigInteger(1, cose.get(CBORObject.FromObject(-2)).GetByteString()));
+    return KeyFactory.getInstance("RSA").generatePublic(spec);
+  }
+
+  private static ECPublicKey importCoseP256PublicKey(CBORObject cose) throws CoseException {
+    return (ECPublicKey) new OneKey(cose).AsPublicKey();
+  }
+
   private static PublicKey importCoseEdDsaPublicKey(CBORObject cose)
       throws InvalidKeySpecException, NoSuchAlgorithmException {
     final int curveId = cose.get(CBORObject.FromObject(-1)).AsInt32();