Use CryptoKit for recovering public key from private EC keys on macOS

src/libraries/Common/src/System/Security/Cryptography/EccAppleCrypto.cs

@@ -232,6 +232,36 @@ internal int ImportParameters(ECParameters parameters)
             return size;
         }
 
+        private static void ExtractPublicKeyFromPrivateKey(ref ECParameters ecParameters)
+        {
+            int keySizeInBits = ecParameters.Curve.Oid.Value switch
+            {
+                Oids.secp256r1 => 256,
+                Oids.secp384r1 => 384,
+                Oids.secp521r1 => 521,
+                _ => throw DebugFail(), // Apple only supports NIST curves.
+            };
+
+            byte[] privateKey = ecParameters.D!;
+            int fieldSize = (keySizeInBits + 7) / 8;
+            Debug.Assert(privateKey.Length == fieldSize);
+
+            const int MaxPublicKeySize = 136; // P-521 is 133 bytes, round this off to 136.
+            Span<byte> publicKey = (stackalloc byte[MaxPublicKeySize]).Slice(0, 1 + 2 * fieldSize);
+            Interop.AppleCrypto.EccExportPublicKeyFromPrivateKey(keySizeInBits, privateKey, publicKey);
+            AsymmetricAlgorithmHelpers.DecodeFromUncompressedAnsiX963Key(
+                publicKey,
+                hasPrivateKey: false,
+                out ECParameters publicParameters);
+            ecParameters.Q = publicParameters.Q;
+
+            static Exception DebugFail()
+            {
+                Debug.Fail($"Unexpected curve with OID.");
+                return new CryptographicException();
+            }
+        }
+
         private static int GetKeySize(SecKeyPair newKeys)
         {
             int size = Interop.AppleCrypto.EccGetKeySizeInBits(newKeys.PublicKey);

src/libraries/Common/src/System/Security/Cryptography/EccAppleCrypto.iOS.cs

@@ -1,13 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Buffers;
-using System.Diagnostics;
-using System.Formats.Asn1;
-using System.Runtime.InteropServices;
-using System.Security.Cryptography.Apple;
-using Internal.Cryptography;
-
 namespace System.Security.Cryptography
 {
     internal sealed partial class EccAppleCrypto
@@ -16,35 +9,5 @@ internal sealed partial class EccAppleCrypto
         private static ECParameters ExportParametersFromLegacyKey(SecKeyPair keys, bool includePrivateParameters)
             => throw new CryptographicException();
 #pragma warning restore IDE0060
-
-        private static void ExtractPublicKeyFromPrivateKey(ref ECParameters ecParameters)
-        {
-            int keySizeInBits = ecParameters.Curve.Oid.Value switch
-            {
-                Oids.secp256r1 => 256,
-                Oids.secp384r1 => 384,
-                Oids.secp521r1 => 521,
-                _ => throw DebugFail(), // Apple only supports NIST curves.
-            };
-
-            byte[] privateKey = ecParameters.D!;
-            int fieldSize = (keySizeInBits + 7) / 8;
-            Debug.Assert(privateKey.Length == fieldSize);
-
-            const int MaxPublicKeySize = 136; // P-521 is 133 bytes, round this off to 136.
-            Span<byte> publicKey = (stackalloc byte[MaxPublicKeySize]).Slice(0, 1 + 2 * fieldSize);
-            Interop.AppleCrypto.EccExportPublicKeyFromPrivateKey(keySizeInBits, privateKey, publicKey);
-            AsymmetricAlgorithmHelpers.DecodeFromUncompressedAnsiX963Key(
-                publicKey,
-                hasPrivateKey: false,
-                out ECParameters publicParameters);
-            ecParameters.Q = publicParameters.Q;
-
-            static Exception DebugFail()
-            {
-                Debug.Fail($"Unexpected curve with OID.");
-                return new CryptographicException();
-            }
-        }
     }
 }

src/libraries/Common/src/System/Security/Cryptography/EccAppleCrypto.macOS.cs

@@ -1,13 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Buffers;
-using System.Diagnostics;
-using System.Formats.Asn1;
-using System.Runtime.InteropServices;
-using System.Security.Cryptography.Apple;
-using Internal.Cryptography;
-
 namespace System.Security.Cryptography
 {
     internal sealed partial class EccAppleCrypto
@@ -48,34 +41,5 @@ private static ECParameters ExportParametersFromLegacyKey(SecKeyPair keys, bool
                 CryptographicOperations.ZeroMemory(keyBlob);
             }
         }
-
-        private static void ExtractPublicKeyFromPrivateKey(ref ECParameters ecParameters)
-        {
-            using (SafeSecKeyRefHandle secPrivateKey = ImportLegacyPrivateKey(ref ecParameters))
-            {
-                const string ExportPassword = "DotnetExportPassphrase";
-                byte[] keyBlob = Interop.AppleCrypto.SecKeyExport(secPrivateKey, exportPrivate: true, password: ExportPassword);
-                EccKeyFormatHelper.ReadEncryptedPkcs8(keyBlob, (ReadOnlySpan<char>)ExportPassword, out _, out ecParameters);
-                CryptographicOperations.ZeroMemory(keyBlob);
-            }
-        }
-
-        private static SafeSecKeyRefHandle ImportLegacyPrivateKey(ref ECParameters parameters)
-        {
-            AsnWriter keyWriter = EccKeyFormatHelper.WriteECPrivateKey(parameters);
-
-            try
-            {
-                return keyWriter.Encode(static encoded =>
-                {
-                    return Interop.AppleCrypto.ImportEphemeralKey(encoded, true);
-                });
-            }
-            finally
-            {
-                // Explicitly clear the inner buffer
-                keyWriter.Reset();
-            }
-        }
     }
 }