PKCS#8 and SPKI PEM Exports

src/libraries/Common/src/Internal/Cryptography/PemKeyImportHelpers.cs → src/libraries/Common/src/Internal/Cryptography/PemKeyHelpers.cs

@@ -7,8 +7,106 @@
 
 namespace Internal.Cryptography
 {
-    internal static class PemKeyImportHelpers
+    internal static class PemKeyHelpers
     {
+        public delegate bool TryExportKeyAction<T>(T arg, Span<byte> destination, out int bytesWritten);
+        public delegate bool TryExportEncryptedKeyAction<T>(
+            T arg,
+            ReadOnlySpan<char> password,
+            PbeParameters pbeParameters,
+            Span<byte> destination,
+            out int bytesWritten);
+
+        public static unsafe bool TryExportToEncryptedPem<T>(
+            T arg,
+            ReadOnlySpan<char> password,
+            PbeParameters pbeParameters,
+            TryExportEncryptedKeyAction<T> exporter,
+            Span<char> destination,
+            out int charsWritten)
+        {
+            int bufferSize = 4096;
+
+            while (true)
+            {
+                byte[] buffer = CryptoPool.Rent(bufferSize);
+                int bytesWritten = 0;
+                bufferSize = buffer.Length;
+
+                // Fixed to prevent GC moves.
+                fixed (byte* bufferPtr = buffer)
+                {
+                    try
+                    {
+                        if (exporter(arg, password, pbeParameters, buffer, out bytesWritten))
+                        {
+                            Span<byte> writtenSpan = new Span<byte>(buffer, 0, bytesWritten);
+                            return PemEncoding.TryWrite(PemLabels.EncryptedPkcs8PrivateKey, writtenSpan, destination, out charsWritten);
+                        }
+                    }
+                    finally
+                    {
+                        CryptoPool.Return(buffer, bytesWritten);
+                    }
+
+                    bufferSize = checked(bufferSize * 2);
+                }
+            }
+        }
+
+        public static unsafe bool TryExportToPem<T>(
+            T arg,
+            string label,
+            TryExportKeyAction<T> exporter,
+            Span<char> destination,
+            out int charsWritten)
+        {
+            int bufferSize = 4096;
+
+            while (true)
+            {
+                byte[] buffer = CryptoPool.Rent(bufferSize);
+                int bytesWritten = 0;
+                bufferSize = buffer.Length;
+
+                // Fixed to prevent GC moves.
+                fixed (byte* bufferPtr = buffer)
+                {
+                    try
+                    {
+                        if (exporter(arg, buffer, out bytesWritten))
+                        {
+                            Span<byte> writtenSpan = new Span<byte>(buffer, 0, bytesWritten);
+                            return PemEncoding.TryWrite(label, writtenSpan, destination, out charsWritten);
+                        }
+                    }
+                    finally
+                    {
+                        CryptoPool.Return(buffer, bytesWritten);
+                    }
+
+                    bufferSize = checked(bufferSize * 2);
+                }
+            }
+        }
+
+        internal static string CreatePemFromData(string label, ReadOnlyMemory<byte> data)
+        {
+            int pemSize = PemEncoding.GetEncodedSize(label.Length, data.Length);
+
+            return string.Create(pemSize, (label, data), static (destination, args) =>
+            {
+                (string label, ReadOnlyMemory<byte> data) = args;
+
+                if (!PemEncoding.TryWrite(label, data.Span, destination, out int charsWritten) ||
+                    charsWritten != destination.Length)
+                {
+                    Debug.Fail("Pre-allocated buffer was not the correct size.");
+                    throw new CryptographicException();
+                }
+            });
+        }
+
         public delegate void ImportKeyAction(ReadOnlySpan<byte> source, out int bytesRead);
         public delegate ImportKeyAction? FindImportActionFunc(ReadOnlySpan<char> label);
         public delegate void ImportEncryptedKeyAction<TPass>(

src/libraries/System.Security.Cryptography.Algorithms/src/System.Security.Cryptography.Algorithms.csproj

@@ -108,8 +108,8 @@
              Link="Internal\Cryptography\BasicSymmetricCipher.cs" />
     <Compile Include="$(CommonPath)Internal\Cryptography\Helpers.cs"
              Link="Internal\Cryptography\Helpers.cs" />
-    <Compile Include="$(CommonPath)Internal\Cryptography\PemKeyImportHelpers.cs"
-             Link="Common\Internal\Cryptography\PemKeyImportHelpers.cs" />
+    <Compile Include="$(CommonPath)Internal\Cryptography\PemKeyHelpers.cs"
+             Link="Common\Internal\Cryptography\PemKeyHelpers.cs" />
     <Compile Include="$(CommonPath)Internal\Cryptography\ILiteSymmetricCipher.cs"
              Link="Internal\Cryptography\ILiteSymmetricCipher.cs" />
     <Compile Include="$(CommonPath)Internal\Cryptography\SymmetricPadding.cs"

src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/ECDiffieHellman.cs

@@ -469,7 +469,7 @@ public virtual unsafe bool TryExportECPrivateKey(Span<byte> destination, out int
         /// </remarks>
         public override void ImportFromPem(ReadOnlySpan<char> input)
         {
-            PemKeyImportHelpers.ImportPem(input, label => {
+            PemKeyHelpers.ImportPem(input, label => {
                 if (label.SequenceEqual(PemLabels.Pkcs8PrivateKey))
                 {
                     return ImportPkcs8PrivateKey;

src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/ECDsa.cs

@@ -1333,7 +1333,7 @@ public int GetMaxSignatureSize(DSASignatureFormat signatureFormat)
         /// </remarks>
         public override void ImportFromPem(ReadOnlySpan<char> input)
         {
-            PemKeyImportHelpers.ImportPem(input, label => {
+            PemKeyHelpers.ImportPem(input, label => {
                 if (label.SequenceEqual(PemLabels.Pkcs8PrivateKey))
                 {
                     return ImportPkcs8PrivateKey;

src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/RSA.cs

@@ -679,7 +679,7 @@ public override unsafe void ImportEncryptedPkcs8PrivateKey(
         /// </remarks>
         public override void ImportFromPem(ReadOnlySpan<char> input)
         {
-            PemKeyImportHelpers.ImportPem(input, label => {
+            PemKeyHelpers.ImportPem(input, label => {
                 if (label.SequenceEqual(PemLabels.RsaPrivateKey))
                 {
                     return ImportRSAPrivateKey;

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

@@ -63,8 +63,11 @@ public void Dispose() { }
         protected virtual void Dispose(bool disposing) { }
         public virtual byte[] ExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<byte> passwordBytes, System.Security.Cryptography.PbeParameters pbeParameters) { throw null; }
         public virtual byte[] ExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters) { throw null; }
+        public string ExportEncryptedPkcs8PrivateKeyPem(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters) { throw null; }
         public virtual byte[] ExportPkcs8PrivateKey() { throw null; }
+        public string ExportPkcs8PrivateKeyPem() { throw null; }
         public virtual byte[] ExportSubjectPublicKeyInfo() { throw null; }
+        public string ExportSubjectPublicKeyInfoPem() { throw null; }
         public virtual void FromXmlString(string xmlString) { }
         public virtual void ImportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<byte> passwordBytes, System.ReadOnlySpan<byte> source, out int bytesRead) { throw null; }
         public virtual void ImportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.ReadOnlySpan<byte> source, out int bytesRead) { throw null; }
@@ -76,8 +79,11 @@ public virtual void ImportFromPem(System.ReadOnlySpan<char> input) { }
         public virtual string ToXmlString(bool includePrivateParameters) { throw null; }
         public virtual bool TryExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<byte> passwordBytes, System.Security.Cryptography.PbeParameters pbeParameters, System.Span<byte> destination, out int bytesWritten) { throw null; }
         public virtual bool TryExportEncryptedPkcs8PrivateKey(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters, System.Span<byte> destination, out int bytesWritten) { throw null; }
+        public bool TryExportEncryptedPkcs8PrivateKeyPem(System.ReadOnlySpan<char> password, System.Security.Cryptography.PbeParameters pbeParameters, System.Span<char> destination, out int charsWritten) { throw null; }
         public virtual bool TryExportPkcs8PrivateKey(System.Span<byte> destination, out int bytesWritten) { throw null; }
+        public bool TryExportPkcs8PrivateKeyPem(System.Span<char> destination, out int charsWritten) { throw null; }
         public virtual bool TryExportSubjectPublicKeyInfo(System.Span<byte> destination, out int bytesWritten) { throw null; }
+        public bool TryExportSubjectPublicKeyInfoPem(System.Span<char> destination, out int charsWritten) { throw null; }
     }
     [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
     public abstract partial class AsymmetricKeyExchangeFormatter

src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj

@@ -21,8 +21,8 @@
              Link="Common\System\Obsoletions.cs" />
     <Compile Include="$(CommonPath)Internal\Cryptography\Helpers.cs"
              Link="Internal\Cryptography\Helpers.cs" />
-    <Compile Include="$(CommonPath)Internal\Cryptography\PemKeyImportHelpers.cs"
-             Link="Internal\Cryptography\PemKeyImportHelpers.cs" />
+    <Compile Include="$(CommonPath)Internal\Cryptography\PemKeyHelpers.cs"
+             Link="Internal\Cryptography\PemKeyHelpers.cs" />
     <Compile Include="$(CommonPath)System\Security\Cryptography\CryptoPool.cs"
              Link="Common\System\Security\Cryptography\CryptoPool.cs" />
     <Compile Include="$(CommonPath)System\Security\Cryptography\KeySizeHelpers.cs"