通过REST API上传Azure Blob时无法设置contentType

Question

I have the below code which successfully uploads an image to my Azure Blob storage container. However, by default it sets the ContentType of the stored file to application/octet-stream I would like to change this to image/jpg .

To do that I wrote the lines which are in comments below. They set the required content-type headers as far as I understand them from the Azure documentation , however the request now results in a 403 Unauthorized response instead of a 200 .

private static void PutBlob(string filenameToSave)
{
    var requestMethod = "PUT";
    var urlPath = _storageContainer + "/" + filenameToSave;
    var storageServiceVersion = "2015-12-11";
    var date = DateTime.UtcNow.ToString("R", CultureInfo.InvariantCulture);
    var blobType = "BlockBlob";
    var imageBytes = GetImageBytes();
    var canonicalizedResource = "/" + _storageAccount + "/" + urlPath;

    // DOESN'T WORK:
    var canonicalizedHeaders = "x-ms-blob-type:" + blobType + "\nx-ms-blob-content-type:image/jpeg\nx-ms-date:" + date + "\nx-ms-version:" + storageServiceVersion;
    // WORKS:
    //var canonicalizedHeaders = "x-ms-blob-type:" + blobType + "\nx-ms-date:" + date + "\nx-ms-version:" + storageServiceVersion;

    // DOESN'T WORK:
    string stringToSign = requestMethod + "\nimage/jpeg\n\n" + imageBytes.Length + "\n\n\n\n\n\n\n\n\n" + canonicalizedHeaders + "\n" + canonicalizedResource;
    // WORKS:
    //string stringToSign = requestMethod + "\n\n\n" + imageBytes.Length + "\n\n\n\n\n\n\n\n\n" + canonicalizedHeaders + "\n" + canonicalizedResource;

    string authorizationHeader = GenerateSharedKey(stringToSign, _storageKey, _storageAccount);

    var uri = $"https://{_storageAccount}.blob.core.windows.net/{urlPath}";
    var request = (HttpWebRequest)WebRequest.Create(uri);
    request.Method = requestMethod;
    request.ContentType = "image/jpeg"; // DOESN'T WORK

    request.Headers.Add("x-ms-blob-content-type", "image/jpeg"); // DOESN'T WORK
    request.Headers.Add("x-ms-blob-type", blobType);
    request.Headers.Add("x-ms-date", date);
    request.Headers.Add("x-ms-version", storageServiceVersion);
    request.Headers.Add("Authorization", authorizationHeader);

    var stream = request.GetRequestStream();
    stream.Write(imageBytes, 0, imageBytes.Length);

    using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
    {
        // check the response status here, 200/201 means it worked

        Console.WriteLine("File uploaded");
    }
}

private static string GenerateSharedKey(string stringToSign, string key, string account)
{
    string signature;
    var unicodeKey = Convert.FromBase64String(key);
    using (var hmacSha256 = new HMACSHA256(unicodeKey))
    {
        var dataToHmac = Encoding.UTF8.GetBytes(stringToSign);
        signature = Convert.ToBase64String(hmacSha256.ComputeHash(dataToHmac));
    }
    return string.Format(CultureInfo.InvariantCulture, "{0} {1}:{2}", "SharedKey", account, signature);
}

I can see that the issue is with the generated authorizationHeader , but I cannot see why as I have followed the guide. Can anyone help me shed some light on this.

Also note that I have to do this through the REST API and not the Microsoft.WindowsAzure.Storage library (annoyingly, as I know it's a fraction of the code when done in that way).

Thanks.

Answer 1

I discovered one issue in your code:

// DOESN'T WORK:
    string stringToSign = requestMethod + "\nimage/jpeg\n\n" + imageBytes.Length + "\n\n\n\n\n\n\n\n\n" + canonicalizedHeaders + "\n" + canonicalizedResource;

Essentially ContentType should not be the 2nd parameter. 2nd parameter is Content-Encoding based on the documentation

StringToSign = VERB + "\n" +
               Content-Encoding + "\n" +
               Content-Language + "\n" +
               Content-Length + "\n" +
               Content-MD5 + "\n" +
               Content-Type + "\n" +
               Date + "\n" +
               If-Modified-Since + "\n" +
               If-Match + "\n" +
               If-None-Match + "\n" +
               If-Unmodified-Since + "\n" +
               Range + "\n" +
               CanonicalizedHeaders + 
               CanonicalizedResource;

So once you change this, your code should work:

        string stringToSign = requestMethod + "\n" +
            "\n" + //Content Encoding
            "\n" + //Content Language
            imageBytes.Length + "\n" + //Content Length
            "\n" + //Content MD5
            "image/jpeg" + "\n" + //Content Type
            "\n" + //Date
            "\n" + //If - Modified - Since
            "\n" + //If - Match
            "\n" + //If - None - Match
            "\n" + //If - Unmodified - Since
            "\n" + //Range +
           canonicalizedHeaders + "\n" +
           canonicalizedResource;

Also, you don't need to specify both Content-Type and x-ms-blob-content-type . If you define x-ms-blob-content-type , then it should be included in canonicalizedHeaders .

Here's the code I used to test this:

    private static void PutBlob(string filenameToSave)
    {
        var requestMethod = "PUT";
        var urlPath = "<container-name>" + "/" + filenameToSave;
        var storageServiceVersion = "2015-12-11";
        var date = DateTime.UtcNow.ToString("R", CultureInfo.InvariantCulture);
        var blobType = "BlockBlob";
        var imageBytes = File.ReadAllBytes(@"File Path");
        var canonicalizedResource = "/" + accountName + "/" + urlPath;

        // DOESN'T WORK:
        //var canonicalizedHeaders = "x-ms-blob-type:" + blobType + "\nx-ms-blob-content-type:image/jpeg\nx-ms-date:" + date + "\nx-ms-version:" + storageServiceVersion;
        // WORKS:
        var canonicalizedHeaders = "x-ms-blob-type:" + blobType + "\nx-ms-date:" + date + "\nx-ms-version:" + storageServiceVersion + "\n";

        // DOESN'T WORK:
        //string stringToSign = requestMethod + "\nimage/jpeg\n\n" + imageBytes.Length + "\n\n\n\n\n\n\n\n\n" + canonicalizedHeaders + "\n" + canonicalizedResource;
        // WORKS:
        //string stringToSign = requestMethod + "\n\n\n" + imageBytes.Length + "\n\n\n\n\n\n\n\n\n" + canonicalizedHeaders + "\n" + canonicalizedResource;
        string stringToSign = requestMethod + "\n" +
            "\n" + //Content Encoding
            "\n" + //Content Language
            imageBytes.Length + "\n" + //Content Length
            "\n" + //Content MD5
            "image/jpeg" + "\n" + //Content Type
            "\n" + //Date
            "\n" + //If - Modified - Since
            "\n" + //If - Match
            "\n" + //If - None - Match
            "\n" + //If - Unmodified - Since
            "\n" + //Range +
           canonicalizedHeaders +
           canonicalizedResource;
        string authorizationHeader = GenerateSharedKey(stringToSign, accountKey, accountName);

        var uri = "https://" + accountName + ".blob.core.windows.net/" + urlPath;

        var request = (HttpWebRequest)WebRequest.Create(uri);
        request.Method = requestMethod;
        request.ContentType = "image/jpeg"; // DOESN'T WORK

        //request.Headers.Add("x-ms-blob-content-type", "image/jpeg"); // DOESN'T WORK
        request.Headers.Add("x-ms-blob-type", blobType);
        request.Headers.Add("x-ms-date", date);
        request.Headers.Add("x-ms-version", storageServiceVersion);
        request.Headers.Add("Authorization", authorizationHeader);

        var stream = request.GetRequestStream();
        stream.Write(imageBytes, 0, imageBytes.Length);

        using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
        {
            // check the response status here, 200/201 means it worked

            Console.WriteLine("File uploaded");
        }
    }