Model binding failed with gzipped request body

[kshyju]

When handling a request which was gzip compressed (Accept-Encoding: gzip), Model binding does not work. Asp.net core version 3.1

Throws this error.

System.Text.DecoderFallbackException: Unable to translate bytes [8B] at index 1 from specified code page to Unicode.
   at System.Text.DecoderExceptionFallbackBuffer.Throw(Byte[] bytesUnknown, Int32 index)
   at System.Text.DecoderExceptionFallbackBuffer.Fallback(Byte[] bytesUnknown, Int32 index)
   at System.Text.Encoding.GetCharsWithFallback(ReadOnlySpan`1 bytes, Int32 originalBytesLength, Span`1 chars, Int32 originalCharsLength, DecoderNLS decoder)
   at System.Text.UTF8Encoding.GetCharsWithFallback(ReadOnlySpan`1 bytes, Int32 originalBytesLength, Span`1 chars, Int32 originalCharsLength, DecoderNLS decoder)
   at System.Text.Encoding.GetCharsWithFallback(Byte* pOriginalBytes, Int32 originalByteCount, Char* pOriginalChars, Int32 originalCharCount, Int32 bytesConsumedSoFar, Int32 charsWrittenSoFar, DecoderNLS decoder)
   at System.Text.Encoding.GetChars(Byte* pBytes, Int32 byteCount, Char* pChars, Int32 charCount, DecoderNLS decoder)
   at System.Text.DecoderNLS.GetChars(Byte[] bytes, Int32 byteIndex, Int32 byteCount, Char[] chars, Int32 charIndex, Boolean flush)
   at System.Text.DecoderNLS.GetChars(Byte[] bytes, Int32 byteIndex, Int32 byteCount, Char[] chars, Int32 charIndex)
   at Microsoft.AspNetCore.WebUtilities.HttpRequestStreamReader.ReadIntoBuffer()
   at Microsoft.AspNetCore.WebUtilities.HttpRequestStreamReader.Read(Char[] buffer, Int32 index, Int32 count)
   at Newtonsoft.Json.JsonTextReader.ReadData(Boolean append, Int32 charsRequired)
   at Newtonsoft.Json.JsonTextReader.ParseValue()
   at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Formatters.NewtonsoftJsonInputFormatter.ReadRequestBodyAsync(InputFormatterContext context, Encoding encoding)
   at Microsoft.AspNetCore.Mvc.ModelBinding.Binders.BodyModelBinder.BindModelAsync(ModelBindingContext bindingContext)
   at Microsoft.AspNetCore.Mvc.ModelBinding.ParameterBinder.BindModelAsync(ActionContext actionContext, IModelBinder modelBinder, IValueProvider valueProvider, ParameterDescriptor parameter, ModelMetadata metadata, Object value)
   at Microsoft.AspNetCore.Mvc.Controllers.ControllerBinderDelegateProvider.<>c__DisplayClass0_0.<<CreateBinderDelegate>g__Bind|0>d.MoveNext()

Is GZIP decompression not built into default model binder ? What is the recommended solution to handle an http post request which is gzip compressed ? Should I be writing a middleware which decompresses and set the context.Request.Body before modelbinder middleware is invoked, like below ?

var gzipStream = new GZipStream(context.Request.Body, CompressionMode.Decompress, leaveOpen: true);
context.Request.Body = gzipStream;

[davidfowl]

Is GZIP decompression not built into default model binder ?

No, the gzip stream is not built in.

Should I be writing a middleware which decompresses and set the context.Request.Body before modelbinder middleware is invoked, like below ?

Yep.

[kshyju]

Thanks for confirmation. Closing.