Kestrel response header encoding (#33776)

src/Servers/Kestrel/Core/src/Internal/Http/HttpHeaders.cs

@@ -9,6 +9,7 @@
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Text;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure;
 using Microsoft.Extensions.Primitives;
@@ -260,21 +261,25 @@ IEnumerator IEnumerable.GetEnumerator()
             return TryGetValueFast(key, out value);
         }
 
-        public static void ValidateHeaderValueCharacters(StringValues headerValues)
+        public static void ValidateHeaderValueCharacters(string headerName, StringValues headerValues, Func<string, Encoding?> encodingSelector)
         {
+            var requireAscii = ReferenceEquals(encodingSelector, KestrelServerOptions.DefaultHeaderEncodingSelector)
+                || encodingSelector(headerName) == null;
+
             var count = headerValues.Count;
             for (var i = 0; i < count; i++)
 
             {
-                ValidateHeaderValueCharacters(headerValues[i]);
+                ValidateHeaderValueCharacters(headerValues[i], requireAscii);
             }
         }
 
-        public static void ValidateHeaderValueCharacters(string headerCharacters)
+        public static void ValidateHeaderValueCharacters(string headerCharacters, bool requireAscii)
         {
             if (headerCharacters != null)
             {
-                var invalid = HttpCharacters.IndexOfInvalidFieldValueChar(headerCharacters);
+                var invalid = requireAscii ? HttpCharacters.IndexOfInvalidFieldValueChar(headerCharacters)
+                    : HttpCharacters.IndexOfInvalidFieldValueCharExtended(headerCharacters);
                 if (invalid >= 0)
                 {
                     ThrowInvalidHeaderCharacter(headerCharacters[invalid]);

src/Servers/Kestrel/Core/src/Internal/Http/HttpProtocol.cs

@@ -374,6 +374,7 @@ public void Reset()
             HttpRequestHeaders.EncodingSelector = ServerOptions.RequestHeaderEncodingSelector;
             HttpRequestHeaders.ReuseHeaderValues = !ServerOptions.DisableStringReuse;
             HttpResponseHeaders.Reset();
+            HttpResponseHeaders.EncodingSelector = ServerOptions.ResponseHeaderEncodingSelector;
             RequestHeaders = HttpRequestHeaders;
             ResponseHeaders = HttpResponseHeaders;
             RequestTrailers.Clear();

src/Servers/Kestrel/Core/src/Internal/Http/HttpRequestHeaders.cs

@@ -24,7 +24,7 @@ internal sealed partial class HttpRequestHeaders : HttpHeaders
         public HttpRequestHeaders(bool reuseHeaderValues = true, Func<string, Encoding?>? encodingSelector = null)
         {
             ReuseHeaderValues = reuseHeaderValues;
-            EncodingSelector = encodingSelector ?? KestrelServerOptions.DefaultRequestHeaderEncodingSelector;
+            EncodingSelector = encodingSelector ?? KestrelServerOptions.DefaultHeaderEncodingSelector;
         }
 
         public void OnHeadersComplete()
@@ -97,7 +97,7 @@ private void AppendContentLength(ReadOnlySpan<byte> value)
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         [SkipLocalsInit]
-        private void AppendContentLengthCustomEncoding(ReadOnlySpan<byte> value, Encoding? customEncoding)
+        private void AppendContentLengthCustomEncoding(ReadOnlySpan<byte> value, Encoding customEncoding)
         {
             if (_contentLength.HasValue)
             {
@@ -106,7 +106,7 @@ private void AppendContentLengthCustomEncoding(ReadOnlySpan<byte> value, Encodin
 
             // long.MaxValue = 9223372036854775807 (19 chars)
             Span<char> decodedChars = stackalloc char[20];
-            var numChars = customEncoding!.GetChars(value, decodedChars);
+            var numChars = customEncoding.GetChars(value, decodedChars);
             long parsed = -1;
 
             if (numChars > 19 ||

src/Servers/Kestrel/Core/src/Internal/Http/HttpResponseHeaders.cs

@@ -4,10 +4,11 @@
 using System;
 using System.Buffers;
 using System.Diagnostics.CodeAnalysis;
-using System.IO.Pipelines;
 using System.Collections;
 using System.Collections.Generic;
+using System.IO.Pipelines;
 using System.Runtime.CompilerServices;
+using System.Text;
 using Microsoft.Extensions.Primitives;
 using Microsoft.Net.Http.Headers;
 
@@ -19,6 +20,13 @@ internal sealed partial class HttpResponseHeaders : HttpHeaders
         private static ReadOnlySpan<byte> CrLf => new[] { (byte)'\r', (byte)'\n' };
         private static ReadOnlySpan<byte> ColonSpace => new[] { (byte)':', (byte)' ' };
 
+        public Func<string, Encoding?> EncodingSelector { get; set; }
+
+        public HttpResponseHeaders(Func<string, Encoding?>? encodingSelector = null)
+        {
+            EncodingSelector = encodingSelector ?? KestrelServerOptions.DefaultHeaderEncodingSelector;
+        }
+
         public Enumerator GetEnumerator()
         {
             return new Enumerator(this);
@@ -34,10 +42,18 @@ internal void CopyTo(ref BufferWriter<PipeWriter> buffer)
             CopyToFast(ref buffer);
 
             var extraHeaders = MaybeUnknown;
+            // Only reserve stack space for the enumerators if there are extra headers
             if (extraHeaders != null && extraHeaders.Count > 0)
             {
-                // Only reserve stack space for the enumartors if there are extra headers
-                CopyExtraHeaders(ref buffer, extraHeaders);
+                var encodingSelector = EncodingSelector;
+                if (ReferenceEquals(encodingSelector, KestrelServerOptions.DefaultHeaderEncodingSelector))
+                {
+                    CopyExtraHeaders(ref buffer, extraHeaders);
+                }
+                else
+                {
+                    CopyExtraHeadersCustomEncoding(ref buffer, extraHeaders, encodingSelector);
+                }
             }
 
             static void CopyExtraHeaders(ref BufferWriter<PipeWriter> buffer, Dictionary<string, StringValues> headers)
@@ -56,6 +72,33 @@ static void CopyExtraHeaders(ref BufferWriter<PipeWriter> buffer, Dictionary<str
                     }
                 }
             }
+
+            static void CopyExtraHeadersCustomEncoding(ref BufferWriter<PipeWriter> buffer, Dictionary<string, StringValues> headers,
+                Func<string, Encoding?> encodingSelector)
+            {
+                foreach (var kv in headers)
+                {
+                    var encoding = encodingSelector(kv.Key);
+                    foreach (var value in kv.Value)
+                    {
+                        if (value != null)
+                        {
+                            buffer.Write(CrLf);
+                            buffer.WriteAscii(kv.Key);
+                            buffer.Write(ColonSpace);
+
+                            if (encoding is null)
+                            {
+                                buffer.WriteAscii(value);
+                            }
+                            else
+                            {
+                                buffer.WriteEncoded(value, encoding);
+                            }
+                        }
+                    }
+                }
+            }
         }
 
         private static long ParseContentLength(string value)

src/Servers/Kestrel/Core/src/Internal/Http/HttpResponseTrailers.cs

@@ -5,12 +5,20 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using System.Text;
 using Microsoft.Extensions.Primitives;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 {
     internal partial class HttpResponseTrailers : HttpHeaders
     {
+        public Func<string, Encoding?> EncodingSelector { get; set; }
+
+        public HttpResponseTrailers(Func<string, Encoding?>? encodingSelector = null)
+        {
+            EncodingSelector = encodingSelector ?? KestrelServerOptions.DefaultHeaderEncodingSelector;
+        }
+
         public Enumerator GetEnumerator()
         {
             return new Enumerator(this);

src/Servers/Kestrel/Core/src/Internal/Http2/HPackHeaderWriter.cs

@@ -87,7 +87,7 @@ private static bool EncodeStatusHeader(int statusCode, DynamicHPackEncoder hpack
                 default:
                     const string name = ":status";
                     var value = StatusCodes.ToStatusString(statusCode);
-                    return hpackEncoder.EncodeHeader(buffer, H2StaticTable.Status200, HeaderEncodingHint.Index, name, value, out length);
+                    return hpackEncoder.EncodeHeader(buffer, H2StaticTable.Status200, HeaderEncodingHint.Index, name, value, valueEncoding: null, out length);
             }
         }
 
@@ -99,6 +99,9 @@ private static bool EncodeHeadersCore(DynamicHPackEncoder hpackEncoder, Http2Hea
                 var staticTableId = headersEnumerator.HPackStaticTableId;
                 var name = headersEnumerator.Current.Key;
                 var value = headersEnumerator.Current.Value;
+                var valueEncoding =
+                    ReferenceEquals(headersEnumerator.EncodingSelector, KestrelServerOptions.DefaultHeaderEncodingSelector)
+                    ? null : headersEnumerator.EncodingSelector(name);
 
                 var hint = ResolveHeaderEncodingHint(staticTableId, name);
 
@@ -108,6 +111,7 @@ private static bool EncodeHeadersCore(DynamicHPackEncoder hpackEncoder, Http2Hea
                     hint,
                     name,
                     value,
+                    valueEncoding,
                     out var headerLength))
                 {
                     // If the header wasn't written, and no headers have been written, then the header is too large.

src/Servers/Kestrel/Core/src/Internal/Http2/Http2FrameWriter.cs

@@ -189,11 +189,13 @@ public void WriteResponseHeaders(int streamId, int statusCode, Http2HeadersFrame
                     var done = HPackHeaderWriter.BeginEncodeHeaders(statusCode, _hpackEncoder, _headersEnumerator, buffer, out var payloadLength);
                     FinishWritingHeaders(streamId, payloadLength, done);
                 }
-                catch (HPackEncodingException hex)
+                // Any exception from the HPack encoder can leave the dynamic table in a corrupt state.
+                // Since we allow custom header encoders we don't know what type of exceptions to expect.
+                catch (Exception ex)
                 {
-                    _log.HPackEncodingError(_connectionId, streamId, hex);
-                    _http2Connection.Abort(new ConnectionAbortedException(hex.Message, hex));
-                    throw new InvalidOperationException(hex.Message, hex); // Report the error to the user if this was the first write.
+                    _log.HPackEncodingError(_connectionId, streamId, ex);
+                    _http2Connection.Abort(new ConnectionAbortedException(ex.Message, ex));
+                    throw new InvalidOperationException(ex.Message, ex); // Report the error to the user if this was the first write.
                 }
             }
         }
@@ -215,10 +217,12 @@ public ValueTask<FlushResult> WriteResponseTrailersAsync(int streamId, HttpRespo
                     var done = HPackHeaderWriter.BeginEncodeHeaders(_hpackEncoder, _headersEnumerator, buffer, out var payloadLength);
                     FinishWritingHeaders(streamId, payloadLength, done);
                 }
-                catch (HPackEncodingException hex)
+                // Any exception from the HPack encoder can leave the dynamic table in a corrupt state.
+                // Since we allow custom header encoders we don't know what type of exceptions to expect.
+                catch (Exception ex)
                 {
-                    _log.HPackEncodingError(_connectionId, streamId, hex);
-                    _http2Connection.Abort(new ConnectionAbortedException(hex.Message, hex));
+                    _log.HPackEncodingError(_connectionId, streamId, ex);
+                    _http2Connection.Abort(new ConnectionAbortedException(ex.Message, ex));
                 }
 
                 return TimeFlushUnsynchronizedAsync();

src/Servers/Kestrel/Core/src/Internal/Http2/Http2HeaderEnumerator.cs → src/Servers/Kestrel/Core/src/Internal/Http2/Http2HeadersEnumerator.cs

@@ -1,9 +1,11 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Net.Http.HPack;
+using System.Text;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http;
 using Microsoft.Extensions.Primitives;
 
@@ -25,23 +27,23 @@ private enum HeadersType : byte
         private bool _hasMultipleValues;
         private KnownHeaderType _knownHeaderType;
 
+        public Func<string, Encoding?> EncodingSelector { get; set; } = KestrelServerOptions.DefaultHeaderEncodingSelector;
+
         public int HPackStaticTableId => GetResponseHeaderStaticTableId(_knownHeaderType);
         public KeyValuePair<string, string> Current { get; private set; }
         object IEnumerator.Current => Current;
 
-        public Http2HeadersEnumerator()
-        {
-        }
-
         public void Initialize(HttpResponseHeaders headers)
         {
+            EncodingSelector = headers.EncodingSelector;
             _headersEnumerator = headers.GetEnumerator();
             _headersType = HeadersType.Headers;
             _hasMultipleValues = false;
         }
 
         public void Initialize(HttpResponseTrailers headers)
         {
+            EncodingSelector = headers.EncodingSelector;
             _trailersEnumerator = headers.GetEnumerator();
             _headersType = HeadersType.Trailers;
             _hasMultipleValues = false;

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Stream.FeatureCollection.cs

@@ -25,7 +25,7 @@ IHeaderDictionary IHttpResponseTrailersFeature.Trailers
             {
                 if (ResponseTrailers == null)
                 {
-                    ResponseTrailers = new HttpResponseTrailers();
+                    ResponseTrailers = new HttpResponseTrailers(ServerOptions.ResponseHeaderEncodingSelector);
                     if (HasResponseCompleted)
                     {
                         ResponseTrailers.SetReadOnly();

src/Servers/Kestrel/Core/src/Internal/Http3/Http3FrameWriter.cs

@@ -8,6 +8,7 @@
 using System.IO.Pipelines;
 using System.Net.Http;
 using System.Net.Http.QPack;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
@@ -44,7 +45,7 @@ internal class Http3FrameWriter
         // Write headers to a buffer that can grow. Possible performance improvement
         // by writing directly to output writer (difficult as frame length is prefixed).
         private readonly ArrayBufferWriter<byte> _headerEncodingBuffer;
-        private IEnumerator<KeyValuePair<string, string>>? _headersEnumerator;
+        private Http3HeadersEnumerator _headersEnumerator = new();
         private int _headersTotalSize;
 
         private long _unflushedBytes;
@@ -271,7 +272,7 @@ public ValueTask<FlushResult> WriteResponseTrailersAsync(long streamId, HttpResp
 
                 try
                 {
-                    _headersEnumerator = EnumerateHeaders(headers).GetEnumerator();
+                    _headersEnumerator.Initialize(headers);
                     _headersTotalSize = 0;
                     _headerEncodingBuffer.Clear();
 
@@ -280,9 +281,12 @@ public ValueTask<FlushResult> WriteResponseTrailersAsync(long streamId, HttpResp
                     var done = QPackHeaderWriter.BeginEncode(_headersEnumerator, buffer, ref _headersTotalSize, out var payloadLength);
                     FinishWritingHeaders(payloadLength, done);
                 }
-                catch (QPackEncodingException ex)
+                // Any exception from the QPack encoder can leave the dynamic table in a corrupt state.
+                // Since we allow custom header encoders we don't know what type of exceptions to expect.
+                catch (Exception ex)
                 {
                     _log.QPackEncodingError(_connectionId, streamId, ex);
+                    _connectionContext.Abort(new ConnectionAbortedException(ex.Message, ex));
                     _http3Stream.Abort(new ConnectionAbortedException(ex.Message, ex), Http3ErrorCode.InternalError);
                 }
 
@@ -314,7 +318,7 @@ public ValueTask<FlushResult> FlushAsync(IHttpOutputAborter? outputAborter, Canc
             }
         }
 
-        internal void WriteResponseHeaders(int statusCode, IHeaderDictionary headers)
+        internal void WriteResponseHeaders(int statusCode, HttpResponseHeaders headers)
         {
             lock (_writeLock)
             {
@@ -325,15 +329,19 @@ internal void WriteResponseHeaders(int statusCode, IHeaderDictionary headers)
 
                 try
                 {
-                    _headersEnumerator = EnumerateHeaders(headers).GetEnumerator();
+                    _headersEnumerator.Initialize(headers);
 
                     _outgoingFrame.PrepareHeaders();
                     var buffer = _headerEncodingBuffer.GetSpan(HeaderBufferSize);
                     var done = QPackHeaderWriter.BeginEncode(statusCode, _headersEnumerator, buffer, ref _headersTotalSize, out var payloadLength);
                     FinishWritingHeaders(payloadLength, done);
                 }
-                catch (QPackEncodingException ex)
+                // Any exception from the QPack encoder can leave the dynamic table in a corrupt state.
+                // Since we allow custom header encoders we don't know what type of exceptions to expect.
+                catch (Exception ex)
                 {
+                    _log.QPackEncodingError(_connectionId, _http3Stream.StreamId, ex);
+                    _connectionContext.Abort(new ConnectionAbortedException(ex.Message, ex));
                     _http3Stream.Abort(new ConnectionAbortedException(ex.Message, ex), Http3ErrorCode.InternalError);
                     throw new InvalidOperationException(ex.Message, ex); // Report the error to the user if this was the first write.
                 }
@@ -347,7 +355,6 @@ private void FinishWritingHeaders(int payloadLength, bool done)
             while (!done)
             {
                 ValidateHeadersTotalSize();
-
                 var buffer = _headerEncodingBuffer.GetSpan(HeaderBufferSize);
                 done = QPackHeaderWriter.Encode(_headersEnumerator!, buffer, ref _headersTotalSize, out payloadLength);
                 _headerEncodingBuffer.Advance(payloadLength);
@@ -404,16 +411,5 @@ public void Abort(ConnectionAbortedException error)
                 _outputWriter.Complete();
             }
         }
-
-        private static IEnumerable<KeyValuePair<string, string>> EnumerateHeaders(IHeaderDictionary headers)
-        {
-            foreach (var header in headers)
-            {
-                foreach (var value in header.Value)
-                {
-                    yield return new KeyValuePair<string, string>(header.Key, value);
-                }
-            }
-        }
     }
 }