Obsolete ToXmlString and FromXmlString on ECC types

Co-authored-by: NJeremy Barton <jbarton@microsoft.com>

docs/project/list-of-diagnostics.md

@@ -96,6 +96,7 @@ The PR that reveals the implementation of the `<IncludeInternalObsoleteAttribute
 |  __`SYSLIB0039`__ | TLS versions 1.0 and 1.1 have known vulnerabilities and are not recommended. Use a newer TLS version instead, or use SslProtocols.None to defer to OS defaults. |
 |  __`SYSLIB0040`__ | EncryptionPolicy.NoEncryption and AllowEncryption significantly reduce security and should not be used in production code. |
 |  __`SYSLIB0041`__ | The default hash algorithm and iteration counts in Rfc2898DeriveBytes constructors are outdated and insecure. Use a constructor that accepts the hash algorithm and the number of iterations. |
+|  __`SYSLIB0042`__ | ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys. |
 
 ## Analyzer Warnings
 

src/libraries/Common/src/System/Obsoletions.cs

@@ -135,5 +135,8 @@ internal static class Obsoletions
 
         internal const string Rfc2898OutdatedCtorMessage = "The default hash algorithm and iteration counts in Rfc2898DeriveBytes constructors are outdated and insecure. Use a constructor that accepts the hash algorithm and the number of iterations.";
         internal const string Rfc2898OutdatedCtorDiagId = "SYSLIB0041";
+
+        internal const string EccXmlExportImportMessage = "ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.";
+        internal const string EccXmlExportImportDiagId = "SYSLIB0042";
     }
 }

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

@@ -24,7 +24,9 @@ internal ECDiffieHellmanAndroidPublicKey(ECParameters parameters)
                 _key = new ECAndroid(parameters);
             }
 
+#pragma warning disable 0672 // Member overrides an obsolete member.
             public override string ToXmlString()
+#pragma warning restore 0672
             {
                 throw new PlatformNotSupportedException();
             }

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

@@ -31,7 +31,9 @@ internal ECDiffieHellmanOpenSslPublicKey(ECParameters parameters)
             _key = new ECOpenSsl(parameters);
         }
 
+#pragma warning disable 0672 // Member overrides an obsolete member.
         public override string ToXmlString()
+#pragma warning restore 0672
         {
             throw new PlatformNotSupportedException();
         }

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

@@ -251,7 +251,9 @@ public ECDiffieHellmanSecurityTransformsPublicKey(ECParameters ecParameters)
                     _ecc.ImportParameters(ecParameters);
                 }
 
+#pragma warning disable 0672 // Member overrides an obsolete member.
                 public override string ToXmlString()
+#pragma warning restore 0672
                 {
                     throw new PlatformNotSupportedException();
                 }

src/libraries/System.Security.Cryptography/ref/System.Security.Cryptography.cs

@@ -996,12 +996,14 @@ public sealed partial class ECDiffieHellmanCng : System.Security.Cryptography.EC
         public override byte[] ExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters) { throw null; }
         public override System.Security.Cryptography.ECParameters ExportExplicitParameters(bool includePrivateParameters) { throw null; }
         public override System.Security.Cryptography.ECParameters ExportParameters(bool includePrivateParameters) { throw null; }
+        [System.ObsoleteAttribute("ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.", DiagnosticId="SYSLIB0042", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public void FromXmlString(string xml, System.Security.Cryptography.ECKeyXmlFormat format) { }
         public override void GenerateKey(System.Security.Cryptography.ECCurve curve) { }
         public override void ImportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<byte> passwordBytes, System.ReadOnlySpan<byte> source, out int bytesRead) { throw null; }
         public override void ImportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.ReadOnlySpan<byte> source, out int bytesRead) { throw null; }
         public override void ImportParameters(System.Security.Cryptography.ECParameters parameters) { }
         public override void ImportPkcs8PrivateKey(System.ReadOnlySpan<byte> source, out int bytesRead) { throw null; }
+        [System.ObsoleteAttribute("ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.", DiagnosticId="SYSLIB0042", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public string ToXmlString(System.Security.Cryptography.ECKeyXmlFormat format) { throw null; }
         public override bool TryExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<byte> passwordBytes, System.Security.Cryptography.PbeParameters pbeParameters, System.Span<byte> destination, out int bytesWritten) { throw null; }
         public override bool TryExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters, System.Span<byte> destination, out int bytesWritten) { throw null; }
@@ -1016,8 +1018,10 @@ public sealed partial class ECDiffieHellmanCngPublicKey : System.Security.Crypto
         public override System.Security.Cryptography.ECParameters ExportParameters() { throw null; }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public static System.Security.Cryptography.ECDiffieHellmanPublicKey FromByteArray(byte[] publicKeyBlob, System.Security.Cryptography.CngKeyBlobFormat format) { throw null; }
+        [System.ObsoleteAttribute("ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.", DiagnosticId="SYSLIB0042", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public static System.Security.Cryptography.ECDiffieHellmanCngPublicKey FromXmlString(string xml) { throw null; }
         public System.Security.Cryptography.CngKey Import() { throw null; }
+        [System.ObsoleteAttribute("ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.", DiagnosticId="SYSLIB0042", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public override string ToXmlString() { throw null; }
     }
     public enum ECDiffieHellmanKeyDerivationFunction
@@ -1073,6 +1077,7 @@ public abstract partial class ECDiffieHellmanPublicKey : System.IDisposable
         public virtual System.Security.Cryptography.ECParameters ExportParameters() { throw null; }
         public virtual byte[] ExportSubjectPublicKeyInfo() { throw null; }
         public virtual byte[] ToByteArray() { throw null; }
+        [System.ObsoleteAttribute("ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.", DiagnosticId="SYSLIB0042", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public virtual string ToXmlString() { throw null; }
         public virtual bool TryExportSubjectPublicKeyInfo(System.Span<byte> destination, out int bytesWritten) { throw null; }
     }
@@ -1147,6 +1152,7 @@ public sealed partial class ECDsaCng : System.Security.Cryptography.ECDsa
         public override byte[] ExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters) { throw null; }
         public override System.Security.Cryptography.ECParameters ExportExplicitParameters(bool includePrivateParameters) { throw null; }
         public override System.Security.Cryptography.ECParameters ExportParameters(bool includePrivateParameters) { throw null; }
+        [System.ObsoleteAttribute("ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.", DiagnosticId="SYSLIB0042", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public void FromXmlString(string xml, System.Security.Cryptography.ECKeyXmlFormat format) { }
         public override void GenerateKey(System.Security.Cryptography.ECCurve curve) { }
         protected override byte[] HashData(byte[] data, int offset, int count, System.Security.Cryptography.HashAlgorithmName hashAlgorithm) { throw null; }
@@ -1159,6 +1165,7 @@ public sealed partial class ECDsaCng : System.Security.Cryptography.ECDsa
         public byte[] SignData(byte[] data, int offset, int count) { throw null; }
         public byte[] SignData(System.IO.Stream data) { throw null; }
         public override byte[] SignHash(byte[] hash) { throw null; }
+        [System.ObsoleteAttribute("ToXmlString and FromXmlString have no implementation for ECC types, and are obsolete. Use a standard import and export format such as ExportSubjectPublicKeyInfo or ImportSubjectPublicKeyInfo for public keys and ExportPkcs8PrivateKey or ImportPkcs8PrivateKey for private keys.", DiagnosticId="SYSLIB0042", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public string ToXmlString(System.Security.Cryptography.ECKeyXmlFormat format) { throw null; }
         public override bool TryExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<byte> passwordBytes, System.Security.Cryptography.PbeParameters pbeParameters, System.Span<byte> destination, out int bytesWritten) { throw null; }
         public override bool TryExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters, System.Span<byte> destination, out int bytesWritten) { throw null; }

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/Cng.NotSupported.cs

@@ -258,7 +258,9 @@ public ECDiffieHellmanCng(ECCurve curve)
         public SafeNCryptSecretHandle DeriveSecretAgreementHandle(CngKey otherPartyPublicKey) => null!;
         public SafeNCryptSecretHandle DeriveSecretAgreementHandle(ECDiffieHellmanPublicKey otherPartyPublicKey) => null!;
         public byte[] DeriveKeyMaterial(CngKey otherPartyPublicKey) => null!;
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void FromXmlString(string xml, ECKeyXmlFormat format) { }
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public string ToXmlString(ECKeyXmlFormat format) => null!;
         public override ECDiffieHellmanPublicKey PublicKey => null!;
     }
@@ -275,11 +277,17 @@ public static ECDiffieHellmanPublicKey FromByteArray(byte[] publicKeyBlob, CngKe
             throw new PlatformNotSupportedException(SR.PlatformNotSupported_CryptographyCng);
         }
 
-        // Also throws in Windows, no SupportedOSPlatform required.
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static ECDiffieHellmanCngPublicKey FromXmlString(string xml)
         {
             throw new PlatformNotSupportedException(SR.PlatformNotSupported_CryptographyCng);
         }
+
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        public override string ToXmlString()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_CryptographyCng);
+        }
     }
     public sealed partial class ECDsaCng : ECDsa
     {
@@ -309,10 +317,12 @@ public ECDsaCng(ECCurve curve)
 
         public CngAlgorithm HashAlgorithm { get => null!; set { } }
         public CngKey Key => null!;
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void FromXmlString(string xml, ECKeyXmlFormat format) { }
         public byte[] SignData(byte[] data) => null!;
         public byte[] SignData(byte[] data, int offset, int count) => null!;
         public byte[] SignData(System.IO.Stream data) => null!;
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public string ToXmlString(ECKeyXmlFormat format) => null!;
         public bool VerifyData(byte[] data, byte[] signature) => false;
         public bool VerifyData(byte[] data, int offset, int count, byte[] signature) => false;

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECDiffieHellmanCng.Xml.cs

@@ -5,11 +5,13 @@ namespace System.Security.Cryptography
 {
     public sealed partial class ECDiffieHellmanCng : ECDiffieHellman
     {
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void FromXmlString(string xml, ECKeyXmlFormat format)
         {
             throw new PlatformNotSupportedException();
         }
 
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public string ToXmlString(ECKeyXmlFormat format)
         {
             throw new PlatformNotSupportedException();

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECDiffieHellmanCngPublicKey.cs

@@ -34,11 +34,13 @@ protected override void Dispose(bool disposing)
             base.Dispose(disposing);
         }
 
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public override string ToXmlString()
         {
             throw new PlatformNotSupportedException();
         }
 
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static ECDiffieHellmanCngPublicKey FromXmlString(string xml)
         {
             throw new PlatformNotSupportedException();

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECDiffieHellmanPublicKey.cs

@@ -33,6 +33,7 @@ public virtual byte[] ToByteArray()
         }
 
         // This method must be implemented by derived classes. In order to conform to the contract, it cannot be abstract.
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public virtual string ToXmlString()
         {
             throw new NotImplementedException(SR.NotSupported_SubclassOverride);

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECDiffieHellmanWrapper.cs

@@ -197,7 +197,9 @@ protected override void Dispose(bool disposing)
 
             public override byte[] ToByteArray() => _wrapped.ToByteArray();
 
+#pragma warning disable 0672, SYSLIB0042 // Member overrides an obsolete member, ToXmlString is obsolete.
             public override string ToXmlString() => _wrapped.ToXmlString();
+#pragma warning restore 0672, SYSLIB0042
 
             public override bool Equals(object? obj) => _wrapped.Equals(obj);
 

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECDsaCng.cs

@@ -127,6 +127,7 @@ private byte[] ExportEncryptedPkcs8(ReadOnlySpan<char> pkcs8Password, int kdfCou
                 out bytesWritten);
         }
 
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void FromXmlString(string xml, ECKeyXmlFormat format)
             => throw new PlatformNotSupportedException();
 
@@ -139,6 +140,7 @@ public byte[] SignData(byte[] data)
         public byte[] SignData(Stream data)
             => SignData(data, new HashAlgorithmName(HashAlgorithm.Algorithm));
 
+        [Obsolete(Obsoletions.EccXmlExportImportMessage, DiagnosticId = Obsoletions.EccXmlExportImportDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public string ToXmlString(ECKeyXmlFormat format)
             => throw new PlatformNotSupportedException();
 

src/libraries/System.Security.Cryptography/tests/ECDiffieHellmanPublicKeyTests.cs

@@ -34,7 +34,9 @@ public void TestToXmlString()
             byte[] arg = new byte[1] { 1 };
             var pk = new TestDerived(arg);
 
+#pragma warning disable SYSLIB0042 // ToXmlString and FromXmlString are obsolete
             Assert.Throws<NotImplementedException>(() => pk.ToXmlString());
+#pragma warning restore SYSLIB0042
         }
     }
 }