Support LF request line terminator in HttpParser

src/Servers/Kestrel/Core/src/Internal/KestrelServerImpl.cs

@@ -126,7 +126,7 @@ private static ServiceContext CreateServiceContext(IOptions<KestrelServerOptions
         {
             Log = trace,
             Scheduler = PipeScheduler.ThreadPool,
-            HttpParser = new HttpParser<Http1ParsingHandler>(trace.IsEnabled(LogLevel.Information)),
+            HttpParser = new HttpParser<Http1ParsingHandler>(trace.IsEnabled(LogLevel.Information), serverOptions.DisableHttp1LineFeedTerminators),
             SystemClock = heartbeatManager,
             DateHeaderValueManager = dateHeaderValueManager,
             ConnectionManager = connectionManager,

src/Servers/Kestrel/Core/src/KestrelServerOptions.cs

@@ -25,6 +25,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core;
 /// </summary>
 public class KestrelServerOptions
 {
+    internal const string DisableHttp1LineFeedTerminatorsSwitchKey = "Microsoft.AspNetCore.Server.Kestrel.DisableHttp1LineFeedTerminators";
+
     // internal to fast-path header decoding when RequestHeaderEncodingSelector is unchanged.
     internal static readonly Func<string, Encoding?> DefaultHeaderEncodingSelector = _ => null;
 
@@ -175,6 +177,24 @@ internal bool EnableWebTransportAndH3Datagrams
         set => _enableWebTransportAndH3Datagrams = value;
     }
 
+    /// <summary>
+    /// Internal AppContext switch to toggle whether a request line can end with LF only instead of CR/LF.
+    /// </summary>
+    private bool? _disableHttp1LineFeedTerminators;
+    internal bool DisableHttp1LineFeedTerminators
+    {
+        get
+        {
+            if (!_disableHttp1LineFeedTerminators.HasValue)
+            {
+                _disableHttp1LineFeedTerminators = AppContext.TryGetSwitch(DisableHttp1LineFeedTerminatorsSwitchKey, out var disabled) && disabled;
+            }
+
+            return _disableHttp1LineFeedTerminators.Value;
+        }
+        set => _disableHttp1LineFeedTerminators = value;
+    }
+
     /// <summary>
     /// Specifies a configuration Action to run for each newly created endpoint. Calling this again will replace
     /// the prior action.

src/Servers/Kestrel/shared/test/HttpParsingData.cs

@@ -205,7 +205,15 @@ public static IEnumerable<string> RequestLineInvalidData
                     "CUSTOM / HTTP/1.1a\n",
                     "CUSTOM / HTTP/1.1a\r\n",
                     "CUSTOM / HTTP/1.1ab\r\n",
+                    "CUSTOM / H\n",
+                    "CUSTOM / HT\n",
+                    "CUSTOM / HTT\n",
+                    "CUSTOM / HTTP\n",
+                    "CUSTOM / HTTP/\n",
+                    "CUSTOM / HTTP/1\n",
+                    "CUSTOM / HTTP/1.\n",
                     "CUSTOM / hello\r\n",
+                    "CUSTOM / hello\n",
                     "CUSTOM ? HTTP/1.1\r\n",
                     "CUSTOM /a?b=cHTTP/1.1\r\n",
                     "CUSTOM /a%20bHTTP/1.1\r\n",
@@ -217,6 +225,21 @@ public static IEnumerable<string> RequestLineInvalidData
         }
     }
 
+    // This list is valid in quirk mode
+    public static IEnumerable<string> RequestLineInvalidDataLineFeedTerminator
+    {
+        get
+        {
+            return new[]
+            {
+                    "GET / HTTP/1.0\n",
+                    "GET / HTTP/1.1\n",
+                    "CUSTOM / HTTP/1.0\n",
+                    "CUSTOM / HTTP/1.1\n",
+                };
+        }
+    }
+
     // Bad HTTP Methods (invalid according to RFC)
     public static IEnumerable<string> MethodWithNonTokenCharData
     {
@@ -364,13 +387,19 @@ public static IEnumerable<string> TargetWithNullCharData
             "8charact",
         };
 
-    public static IEnumerable<object[]> RequestHeaderInvalidData => new[]
+    public static IEnumerable<object[]> RequestHeaderInvalidDataLineFeedTerminator => new[]
     {
             // Missing CR
             new[] { "Header: value\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"Header: value\x0A") },
             new[] { "Header-1: value1\nHeader-2: value2\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"Header-1: value1\x0A") },
             new[] { "Header-1: value1\r\nHeader-2: value2\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"Header-2: value2\x0A") },
 
+            // Empty header name
+            new[] { ":a\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@":a\x0A") },
+        };
+
+    public static IEnumerable<object[]> RequestHeaderInvalidData => new[]
+    {
             // Line folding
             new[] { "Header: line1\r\n line2\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@" line2\x0D\x0A") },
             new[] { "Header: line1\r\n\tline2\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"\x09line2\x0D\x0A") },
@@ -404,7 +433,7 @@ public static IEnumerable<string> TargetWithNullCharData
             new[] { "Header-1 value1\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"Header-1 value1\x0D\x0A") },
             new[] { "Header-1 value1\r\nHeader-2: value2\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"Header-1 value1\x0D\x0A") },
             new[] { "Header-1: value1\r\nHeader-2 value2\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"Header-2 value2\x0D\x0A") },
-            new[] { "\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"\x0A") },
+            new[] { "HeaderValue1\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"HeaderValue1\x0D\x0A") },
 
             // Starting with whitespace
             new[] { " Header: value\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@" Header: value\x0D\x0A") },
@@ -435,11 +464,13 @@ public static IEnumerable<string> TargetWithNullCharData
 
             // Headers not ending in CRLF line
             new[] { "Header-1: value1\r\nHeader-2: value2\r\n\r\r", CoreStrings.BadRequest_InvalidRequestHeadersNoCRLF },
-            new[] { "Header-1: value1\r\nHeader-2: value2\r\n\r ", CoreStrings.BadRequest_InvalidRequestHeadersNoCRLF  },
+            new[] { "Header-1: value1\r\nHeader-2: value2\r\n\r ", CoreStrings.BadRequest_InvalidRequestHeadersNoCRLF },
             new[] { "Header-1: value1\r\nHeader-2: value2\r\n\r \n", CoreStrings.BadRequest_InvalidRequestHeadersNoCRLF },
+            new[] { "Header-1: value1\r\nHeader-2\t: value2 \n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@"Header-2\x09: value2 \x0A") },
 
             // Empty header name
             new[] { ": value\r\n\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@": value\x0D\x0A") },
+            new[] { ":a\r\n", CoreStrings.FormatBadRequest_InvalidRequestHeader_Detail(@":a\x0D\x0A") },
         };
 
     public static TheoryData<string, string> HostHeaderData

src/Servers/Kestrel/shared/test/TestServiceContext.cs

@@ -17,17 +17,17 @@ internal class TestServiceContext : ServiceContext
 {
     public TestServiceContext()
     {
-        Initialize(NullLoggerFactory.Instance, CreateLoggingTrace(NullLoggerFactory.Instance));
+        Initialize(NullLoggerFactory.Instance, CreateLoggingTrace(NullLoggerFactory.Instance), false);
     }
 
-    public TestServiceContext(ILoggerFactory loggerFactory)
+    public TestServiceContext(ILoggerFactory loggerFactory, bool disableHttp1LineFeedTerminators = true)
     {
-        Initialize(loggerFactory, CreateLoggingTrace(loggerFactory));
+        Initialize(loggerFactory, CreateLoggingTrace(loggerFactory), disableHttp1LineFeedTerminators);
     }
 
-    public TestServiceContext(ILoggerFactory loggerFactory, KestrelTrace kestrelTrace)
+    public TestServiceContext(ILoggerFactory loggerFactory, KestrelTrace kestrelTrace, bool disableHttp1LineFeedTerminators = true)
     {
-        Initialize(loggerFactory, kestrelTrace);
+        Initialize(loggerFactory, kestrelTrace, disableHttp1LineFeedTerminators);
     }
 
     private static KestrelTrace CreateLoggingTrace(ILoggerFactory loggerFactory)
@@ -49,7 +49,7 @@ public void InitializeHeartbeat()
         SystemClock = heartbeatManager;
     }
 
-    private void Initialize(ILoggerFactory loggerFactory, KestrelTrace kestrelTrace)
+    private void Initialize(ILoggerFactory loggerFactory, KestrelTrace kestrelTrace, bool disableHttp1LineFeedTerminators)
     {
         LoggerFactory = loggerFactory;
         Log = kestrelTrace;
@@ -58,7 +58,7 @@ private void Initialize(ILoggerFactory loggerFactory, KestrelTrace kestrelTrace)
         SystemClock = MockSystemClock;
         DateHeaderValueManager = new DateHeaderValueManager();
         ConnectionManager = new ConnectionManager(Log, ResourceCounter.Unlimited);
-        HttpParser = new HttpParser<Http1ParsingHandler>(Log.IsEnabled(LogLevel.Information));
+        HttpParser = new HttpParser<Http1ParsingHandler>(Log.IsEnabled(LogLevel.Information), disableHttp1LineFeedTerminators);
         ServerOptions = new KestrelServerOptions
         {
             AddServerHeader = false

src/Servers/Kestrel/test/InMemory.FunctionalTests/BadHttpRequestTests.cs

@@ -524,5 +524,7 @@ public static TheoryData<string, string> InvalidRequestLineData
 
     public static IEnumerable<object[]> InvalidRequestHeaderData => HttpParsingData.RequestHeaderInvalidData;
 
+    public static IEnumerable<object[]> InvalidRequestHeaderDataLineFeedTerminator => HttpParsingData.RequestHeaderInvalidDataLineFeedTerminator;
+
     public static TheoryData<string, string> InvalidHostHeaderData => HttpParsingData.HostHeaderInvalidData;
 }

src/Servers/Kestrel/test/InMemory.FunctionalTests/RequestTests.cs

@@ -2284,6 +2284,49 @@ await connection.Receive(
         }
     }
 
+    [Fact]
+    public async Task SingleLineFeedIsSupportedAnywhere()
+    {
+        // Exercises all combinations of LF and CRLF as line separators.
+        // Uses a bit mask for all the possible combinations.
+
+        var lines = new[]
+        {
+                $"GET / HTTP/1.1",
+                "Content-Length: 0",
+                $"Host: localhost",
+                "",
+            };
+
+        await using (var server = new TestServer(context => Task.CompletedTask, new TestServiceContext(LoggerFactory, disableHttp1LineFeedTerminators: false)))
+        {
+            var mask = Math.Pow(2, lines.Length) - 1;
+
+            for (var m = 0; m <= mask; m++)
+            {
+                using (var client = server.CreateConnection())
+                {
+                    var sb = new StringBuilder();
+
+                    for (var pos = 0; pos < lines.Length; pos++)
+                    {
+                        sb.Append(lines[pos]);
+                        var separator = (m & (1 << pos)) != 0 ? "\n" : "\r\n";
+                        sb.Append(separator);
+                    }
+
+                    var text = sb.ToString();
+                    var writer = new StreamWriter(client.Stream, Encoding.GetEncoding("iso-8859-1"));
+                    await writer.WriteAsync(text).ConfigureAwait(false);
+                    await writer.FlushAsync().ConfigureAwait(false);
+                    await client.Stream.FlushAsync().ConfigureAwait(false);
+
+                    await client.Receive("HTTP/1.1 200");
+                }
+            }
+        }
+    }
+
     public static TheoryData<string, string> HostHeaderData => HttpParsingData.HostHeaderData;
 
     private class IntAsClass