Upload to S3 from HTTPWebResponse.GetResponseStream() in c#

Question

I am trying to upload from an HTTP stream directly to S3, without storing in memory or as a file first. I am already doing this with Rackspace Cloud Files as HTTP to HTTP, however the AWS authentication is beyond me so am trying to use the SDK.

The problem is the upload stream is failing with this exception:

"This stream does not support seek operations."

I've tried with PutObject and TransferUtility.Upload, both fail with the same thing.

Is there any way to stream into S3 as the stream comes in, rather than buffering the whole thing to a MemoryStream or FileStream?

or is there any good examples of doing the authentication into S3 request using HTTPWebRequest, so I can duplicate what I do with Cloud Files?

Edit: or is there a helper function in the AWSSDK for generating the authorization header?

CODE:

This is the failing S3 part (both methods included for completeness):

string uri = RSConnection.StorageUrl + "/" + container + "/" + file.SelectSingleNode("name").InnerText;
var req = (HttpWebRequest)WebRequest.Create(uri);
req.Headers.Add("X-Auth-Token", RSConnection.AuthToken);
req.Method = "GET";

using (var resp = req.GetResponse() as HttpWebResponse)
{
    using (Stream stream = resp.GetResponseStream())
    {
        Amazon.S3.Transfer.TransferUtility trans = new Amazon.S3.Transfer.TransferUtility(S3Client);
        trans.Upload(stream, config.Element("root").Element("S3BackupBucket").Value, container + file.SelectSingleNode("name").InnerText);

        //Use EITHER the above OR the below

        PutObjectRequest putReq = new PutObjectRequest();
        putReq.WithBucketName(config.Element("root").Element("S3BackupBucket").Value);
        putReq.WithKey(container + file.SelectSingleNode("name").InnerText);
        putReq.WithInputStream(Amazon.S3.Util.AmazonS3Util.MakeStreamSeekable(stream));
        putReq.WithMetaData("content-length", file.SelectSingleNode("bytes").InnerText);

        using (S3Response putResp = S3Client.PutObject(putReq))
        {

        }
    }

}

And this is how I do it successfully from S3 to Cloud Files:

using (GetObjectResponse getResponse = S3Client.GetObject(new GetObjectRequest().WithBucketName(bucket.BucketName).WithKey(file.Key)))
{
    using (Stream s = getResponse.ResponseStream)
    {
        //We can stream right from s3 to CF, no need to store in memory or filesystem.                                            
        var req = (HttpWebRequest)WebRequest.Create(uri);
        req.Headers.Add("X-Auth-Token", RSConnection.AuthToken);
        req.Method = "PUT";

        req.AllowWriteStreamBuffering = false;
        if (req.ContentLength == -1L)
            req.SendChunked = true;


        using (Stream stream = req.GetRequestStream())
        {
            byte[] data = new byte[32768];
            int bytesRead = 0;
            while ((bytesRead = s.Read(data, 0, data.Length)) > 0)
            {
                stream.Write(data, 0, bytesRead);
            }
            stream.Flush();
            stream.Close();
        }
        req.GetResponse().Close();
    }
}   

Answer 1

As no-one answering seems to have done it, I spent the time working it out based on guidance from Steve's answer:

In answer to this question "is there any good examples of doing the authentication into S3 request using HTTPWebRequest, so I can duplicate what I do with Cloud Files?", here is how to generate the auth header manually:

string today = String.Format("{0:ddd,' 'dd' 'MMM' 'yyyy' 'HH':'mm':'ss' 'zz00}", DateTime.Now);

string stringToSign = "PUT\n" +
    "\n" +
    file.SelectSingleNode("content_type").InnerText + "\n" +
    "\n" +
    "x-amz-date:" + today + "\n" +
    "/" + strBucketName + "/" + strKey;

Encoding ae = new UTF8Encoding();
HMACSHA1 signature = new HMACSHA1(ae.GetBytes(AWSSecret));
string encodedCanonical = Convert.ToBase64String(signature.ComputeHash(ae.GetBytes(stringToSign)));

string authHeader = "AWS " + AWSKey + ":" + encodedCanonical;

string uriS3 = "https://" + strBucketName + ".s3.amazonaws.com/" + strKey;
var reqS3 = (HttpWebRequest)WebRequest.Create(uriS3);
reqS3.Headers.Add("Authorization", authHeader);
reqS3.Headers.Add("x-amz-date", today);
reqS3.ContentType = file.SelectSingleNode("content_type").InnerText;
reqS3.ContentLength = Convert.ToInt32(file.SelectSingleNode("bytes").InnerText);
reqS3.Method = "PUT";

Note the added x-amz-date header as HTTPWebRequest sends the date in a different format to what AWS is expecting.

From there it was just a case of repeating what I was already doing.