Question

I have an asp.net .asmx webservice written to handle requests from a third party tool. The third party tool makes an http POST request to the webservice to get user information. I’m using IIS7

Running Fiddler with “Remove All Encodings” checked, I can see the webservice call and and everything functions properly. If I uncheck “Remove All Encodings”, the webservice call fails with a 400 Bad Request. The difference I see is that the header “Content-Encoding: gzip” is being removed by Fiddler and the content is being decompressed.

So, when the Content-Encoding header is removed and the content is decompressed, my webservice functions perfectly. When the header is present and the content is compressed, the webservice fails.

How can I either:

1. Configure my webservice to tell the client that it won’t accept compressed requests (and hope that the third party tool respects that)
2. Decompress the content early in the asp.net handling
3. Modify my webservice to work with compressed data

Update: To be clear, I don’t need to configure gzip encoding in the Response, I need to deal with a Request TO my webservice that is gzip encoded.

Update 2: The third-party tool is the Salesforce.com Outlook plugin. So, I don’t have access to modify it and it is used by many other companies without trouble. It’s got to be something I’m doing (or not doing)

Update 3: I found one post here that says that IIS does not support incoming POST requests with compressed data, it only supports compressed Responses. Can this still be true?

Answer 1

I’ve found a partial answer here.

class DecompressStream : Stream
{
    ...

    public override int Read(byte[] buffer, int offset, int count)
    {
        GZipStream test = new GZipStream(_sink, CompressionMode.Decompress);

        int c = test.Read(buffer, offset, count);

        return c;
    }

    ...
}

I can then specify the filter on the request object like this:

void Application_BeginRequest(object sender, EventArgs e)
    {
        string contentEncoding = Request.Headers["Content-Encoding"];
        Stream prevCompressedStream = Request.Filter;

        if(contentEncoding == null || contentEncoding.Length == 0)
            return;

        contentEncoding = contentEncoding.ToLower();

        if(contentEncoding.Contains("gzip"))
        {
            Request.Filter = new DecompressStream(Request.Filter);
        }
    }

I say partial answer because even though I can now process the incoming request, the response is getting a “Content-Encoding: gzip” header even though the response is not encoded. I can verify in Fiddler that the content is not encoded.

If I do encode the response, the client for the webservice fails. It seems that even though it is sending “Accept-Encoding: gzip”, it does not in fact accept gzip compressed response. I can verify in Fiddler that the response is compressed and Fiddler will decompress it successfully.

So, now I’m stuck trying to get a stray “Content-Encoding: gzip” header removed from the response. I’ve removed all references I can find to compression from the application, the web.config, and IIS.