How to create azure file storage SAS url(without azure libraries)? - file

Question

My main target is to create a SAS url (without azure libraries)for file.
I tried to create azure storage SAS with blob and everything worked correctly. When I try to do the same in File i got an error. This is my code:
string azAccName = "AccountName";
string resource = "/upgfile/prt.png";
string endPoint = "https://" + azAccName + ".file.core.windows.net";
string uri = endPoint + resource;
string _now = DateTime.UtcNow.ToString("s") + "Z";
string _noww = DateTime.UtcNow.AddHours(3).AddMinutes(5).ToString("s") + "Z";
string StorageKey = "xxx";
string signedpermissions = "r";
string signedstart = _now;//"2017-02-14"; //yyyy-mm--dd
string signedexpiry = _noww;// "2017-02-14";
string canonicalizedresource = "/file/" + azAccName + resource; //"/blob/myaccount/music/intro.mp3"
string signedidentifier = ""; //YWJjZGVmZw==
string signedIP = "";
string signedProtocol = "https";
string signedversion = "2015-02-21";
string rscc = ""; //Cache-Control
string rscd = "file; attachment"; //Content-Disposition
string rsce = ""; //Content-Encoding
string rscl = ""; //Content-Language
string rsct = "binary"; //Content-Type binary
string StringToSign = signedpermissions + "\n" +
signedstart + "\n" +
signedexpiry + "\n" +
canonicalizedresource + "\n" +
signedidentifier + "\n" +
signedversion + "\n" +
rscc + "\n" +
rscd + "\n" +
rsce + "\n" +
rscl + "\n" +
rsct;
HMACSHA256 hmac = new HMACSHA256(Convert.FromBase64String(StorageKey));
string signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(StringToSign)));
string link = String.Format("{0}?sv={1}&st={2}&se={3}&sr={4}&sp={5}&rscd={8}&rsct={9}&spr={6}&sig={7}",
uri,
signedversion,
signedstart,
signedexpiry,
"c", //b for blob
signedpermissions,
"https",
signature.Replace("/", "%2"),
rscd,///////////////
rsct);
I am getting this error.
<Error>
<Code>AuthenticationFailed</Code>
<Message>
Server failed to authenticate the request. Make sure the value of Authorization header is formed correctly including the signature. RequestId:92eda75a-001a-0072-501d-1bb6fd000000 Time:2017-08-22T08:03:58.6115733Z
</Message>
<AuthenticationErrorDetail>Signature fields not well formed.</AuthenticationErrorDetail>
</Error>
I have almost the same code for blob(small differences) and it works correctly.
Any suggestions?

Answer 1

I believe the issue is missing parameters in your stringToSign. You must include all parameters as specified here:
StringToSign = signedpermissions + "\n" +
signedstart + "\n" +
signedexpiry + "\n" +
canonicalizedresource + "\n" +
signedidentifier + "\n" +
signedIP + "\n" +
signedProtocol + "\n" +
signedversion + "\n" +
rscc + "\n" +
rscd + "\n" +
rsce + "\n" +
rscl + "\n" +
rsct
If you're not using a parameter (for example signedIP in your case), you must specify an empty line.
Based on this, your StringToSign should be:
string StringToSign = signedpermissions + "\n" +
signedstart + "\n" +
signedexpiry + "\n" +
canonicalizedresource + "\n" +
signedidentifier + "\n" +
"\n" + //For signed IP
"\n" + //For signed Protocol
signedversion + "\n" +
rscc + "\n" +
rscd + "\n" +
rsce + "\n" +
rscl + "\n" +
rsct;
Furthermore sr (signed resource type) in the link should be f (for file) instead of c that you're using.