The MAC signature found in the HTTP request '***' is not the same as any computed signature. Server used following string to sign: 'POST

Question

Hi,
When trying with Postman sending a REST call to Azure Storage Queues I get:
The MAC signature found in the HTTP request '***' is not the same as any computed signature. Server used following string to sign: 'POST.
The code I have for creating the Authorization Header:
var accountName = "my_account";
string key = ConfigurationManager.AppSettings["my_access_key"];
DateTime dt = DateTime.Now;
string formattedDate = String.Format("{0:r}", dt);
var canonicalizedHeaders = "x-ms-date:" + formattedDate + "\n" + "x-ms-version:2009-09-19" + "\n" ;
var canonicalizedResource = "/my_account/myqueue/messages";
var stringToSign = String.Format("POST,\n\n\n\n\n\n\n\n\n\n\n{0}{1}", canonicalizedHeaders, canonicalizedResource);
stringToSign = HttpUtility.UrlEncode(stringToSign);
HMACSHA256 hmac = new HMACSHA256(Encoding.UTF8.GetBytes(key));
var signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));
var authorizationHeader = String.Format(CultureInfo.InvariantCulture, "SharedKey {0}:{1}", accountName, signature);
return authorizationHeader;
Anyone any idea what I'm missing/doing wrong?
Additional question: do i have to create for every message I want to send a new Authorization header? Or is there an option (as with Service Bus Topics) to create a header that can be used for a certain timeframe?
Thanks.

Answer 1

One issue is with this line of code:
HMACSHA256 hmac = new HMACSHA256(Encoding.UTF8.GetBytes(key));
Please use the following:
HMACSHA256 hmac = new HMACSHA256(Convert.FromBase64String(key));
and that should take care of the problem.
Regarding your question, "do i have to create for every message I want to send a new Authorization header? Or is there an option (as with Service Bus Topics) to create a header that can be used for a certain timeframe?"
With your current approach, the answer is yes. What you can do is create a Shared Access Signature on the queue which will be valid for certain duration and then use that for posting messages to a queue using simple HttpWebRequest/HttpWebResponse.
Hope this helps.