[release/5.0] Fix NegotiateStream handling of EOF

src/libraries/System.Net.Security/src/System/Net/Security/NegotiateStream.cs

@@ -362,7 +362,7 @@ private async ValueTask<int> ReadAsync<TAdapter>(TAdapter adapter, Memory<byte>
 
                 while (true)
                 {
-                    int readBytes = await ReadAllAsync(adapter, _readHeader).ConfigureAwait(false);
+                    int readBytes = await ReadAllAsync(adapter, _readHeader, allowZeroRead: true).ConfigureAwait(false);
                     if (readBytes == 0)
                     {
                         return 0;
@@ -386,12 +386,8 @@ private async ValueTask<int> ReadAsync<TAdapter>(TAdapter adapter, Memory<byte>
                     {
                         _readBuffer = new byte[readBytes];
                     }
-                    readBytes = await ReadAllAsync(adapter, new Memory<byte>(_readBuffer, 0, readBytes)).ConfigureAwait(false);
-                    if (readBytes == 0)
-                    {
-                        // We already checked that the frame body is bigger than 0 bytes. Hence, this is an EOF.
-                        throw new IOException(SR.net_io_eof);
-                    }
+
+                    readBytes = await ReadAllAsync(adapter, new Memory<byte>(_readBuffer, 0, readBytes), allowZeroRead: false).ConfigureAwait(false);
 
                     // Decrypt into internal buffer, change "readBytes" to count now _Decrypted Bytes_
                     // Decrypted data start from zero offset, the size can be shrunk after decryption.
@@ -423,27 +419,28 @@ private async ValueTask<int> ReadAsync<TAdapter>(TAdapter adapter, Memory<byte>
                 _readInProgress = 0;
             }
 
-            static async ValueTask<int> ReadAllAsync(TAdapter adapter, Memory<byte> buffer)
+            static async ValueTask<int> ReadAllAsync(TAdapter adapter, Memory<byte> buffer, bool allowZeroRead)
             {
-                int length = buffer.Length;
+                int read = 0;
 
                 do
                 {
                     int bytes = await adapter.ReadAsync(buffer).ConfigureAwait(false);
                     if (bytes == 0)
                     {
-                        if (!buffer.IsEmpty)
+                        if (read != 0 || !allowZeroRead)
                         {
                             throw new IOException(SR.net_io_eof);
                         }
                         break;
                     }
 
                     buffer = buffer.Slice(bytes);
+                    read += bytes;
                 }
                 while (!buffer.IsEmpty);
 
-                return length;
+                return read;
             }
         }
 

src/libraries/System.Net.Security/tests/FunctionalTests/NegotiateStreamStreamToStreamTest.cs

@@ -376,6 +376,29 @@ await TestConfiguration.WhenAllOrAnyFailedWithTimeout(
                 await Assert.ThrowsAnyAsync<OperationCanceledException>(() => t);
             }
         }
+
+        [ConditionalFact(nameof(IsNtlmInstalled))]
+        public async Task NegotiateStream_ReadToEof_Returns0()
+        {
+            (Stream stream1, Stream stream2) = TestHelper.GetConnectedStreams();
+            using (var client = new NegotiateStream(stream1))
+            using (var server = new NegotiateStream(stream2))
+            {
+                await TestConfiguration.WhenAllOrAnyFailedWithTimeout(
+                    AuthenticateAsClientAsync(client, CredentialCache.DefaultNetworkCredentials, string.Empty),
+                    AuthenticateAsServerAsync(server));
+
+                client.Write(Encoding.UTF8.GetBytes("hello"));
+                client.Dispose();
+
+                Assert.Equal('h', server.ReadByte());
+                Assert.Equal('e', server.ReadByte());
+                Assert.Equal('l', server.ReadByte());
+                Assert.Equal('l', server.ReadByte());
+                Assert.Equal('o', server.ReadByte());
+                Assert.Equal(-1, server.ReadByte());
+            }
+        }
     }
 
     public sealed class NegotiateStreamStreamToStreamTest_Async_Array : NegotiateStreamStreamToStreamTest