AWS IoT - Access shadow through .Net, REST, with certificate

0 votes

Trying to learn AWS IoT, I created a few "Things" + a Policy and I am even able to use IoT CLI to list-things or list-policies. I am even able to update the shadow through CLI with update-thingcommand through CLI. But once I try to access a Shadow through REST GET / POST request (through a .Net program or directly like https://XXXXXXXXXXXXX.iot.us-west-2.amazonaws.com/things/mything/shadow), I receive a

"Missing Authentication Token"

. So I started to use a certificate. Here is part of my code:

string Certificate = "xxxxxxxxx-certificate.crt"; // downloaded from my thing
X509Certificate cert = new X509Certificate(Certificate);
WebRequestHandler handler = new WebRequestHandler();
handler.ClientCertificates.Add(cert);
HttpClient client = new HttpClient(handler);
// url = @"https://xxxxxxxxxxxxx.iot.us-west-2.amazonaws.com/things/<mything>/shadow";
HttpResponseMessage webResponse = client.GetAsync(url, HttpCompletionOption.ResponseContentRead).Result;

The result is:

StatusCode: 403, ReasonPhrase: 'Forbidden', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
x-amzn-RequestId: 25f3c1dc-9ddd-4787-a4cf-cb79dc96748b
connection: Keep-Alive
x-amzn-ErrorType: ForbiddenException:
Date: Tue, 15 Dec 2015 08:53:56 GMT
Content-Length: 91
Content-Type: application/json
}

Any assistance?

Jul 25, 2018 in IoT (Internet of Things) by Matt
• 2,260 points
49 views

1 answer to this question.

Your answer

Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
0 votes

If you want to publish and/or subscribe to topics, you can take two different approach.

  1. HTTPS calls to API endpoints.
  2. Using any of the supported AWS SDKs of your choice (python, java, .NET etc.,) or AWS CLI

For the "missing authentication token" exception you get is due to unavailability of authentication tokens and amazon specific headers in your request. To make your HTTPS request work, You either use a rest client to add amazon specific headers or write a program.

You should try doing the following steps to make your https requests to work.

For detailed steps, refer http://docs.aws.amazon.com/general/latest/gr/sigv4-calculate-signature.html

TASK 1: CREATE A CANONICAL REQUEST

  • Step 1 is to define the verb (GET, POST, etc.)
  • Step 2: Create canonical URI.
  • Step 3: Create the canonical query string.
  • Step 4: Create the canonical headers and signed headers.
  • Step 5: Create the list of signed headers.
  • Step 6: Create payload hash (hash of the request body content)
  • Step 7: Combine elements to create create canonical request

TASK 2: CREATE THE STRING TO SIGN Using SHA256 algorithm, hash the canonical request (using any programming language/tools) and create a string to sign like below

string_to_sign = YourHashingAlgorithm + '\n' + CurrentDateInUTC+ '\n' + credential_scope + '\n' + yourHashedCanonicalRequest

API's to AWS services are uniquely identified by service paths. For IOT it is "iotdata/aws4_request". So your credential_scope in the above 'string_to_sign' should be like

credential_scope = datestamp + '/' + us-west-2+ '/' + iotdata+ '/' + 'aws4_request'

TASK 3: CALCULATE THE SIGNATURE

Calculate the hash using the same algorithm used in previous steps.

Refer the above said link for more details.

TASK 4: ADD SIGNING INFORMATION TO THE REQUEST

Here you need to set some of the headers like 'x-amz-date','Authorization', 'SignedHeaders' and 'Signature'. This Signature header will carry the final value of the Step 3.

Note: None of these headers are optional. Every HTTPS request should have all this information for authentication and authorization. Else AWS API will reject it.

You should get a 200 OK response to assure that your request is actually processed.

Coming to your .Net approach, you can try using AWS's .NET SDK and try inspecting the final request. I never tried using x.509 certificates directly in code. I think you are missing headers in your requests.

In cURL it would be something like below

curl "https://iot.amazonaws.com" \ --request GET \ --form "Action=UpdateThing" \ --form "UserName=iam_user" \ --form "CertificateBody=@~/.aws/credentials/sample/cert.pem" \ --form "Version=2010-05-08" \ --form "AUTHPARAMS"

Hope this helps

answered Jul 25, 2018 by anonymous2
• 4,260 points

Related Questions In IoT (Internet of Things)

0 votes
1 answer
0 votes
1 answer
0 votes
1 answer

How to work a AWS IOT Lambda with a devices?

Hey KanaguRaj, use this for reference: https://serverless.com/b ...READ MORE

answered Apr 12 in IoT (Internet of Things) by Vardhan
• 10,560 points
29 views
0 votes
1 answer

Display time in a Windows Core IoT app with a clock!

It is possible, but you should understand ...READ MORE

answered Jul 9, 2018 in IoT (Internet of Things) by nirvana
• 3,040 points
47 views
0 votes
1 answer

aws iot describe-endpoint::You must specify a region

This fixed the problem: Browse to https://console.aws.amazon.com/iam/home?region=us-west-2#security_credentialand then if ...READ MORE

answered Jul 11, 2018 in IoT (Internet of Things) by anonymous2
• 4,260 points
133 views
0 votes
1 answer
0 votes
1 answer

Configuring Raspberry Pi with Windows 10 IoT App using Rest API

You should use HttpClient instead of WebClient. Try ...READ MORE

answered Oct 10, 2018 in IoT (Internet of Things) by anonymous2
• 4,260 points
62 views
0 votes
1 answer

© 2018 Brain4ce Education Solutions Pvt. Ltd. All rights Reserved.
"PMP®","PMI®", "PMI-ACP®" and "PMBOK®" are registered marks of the Project Management Institute, Inc. MongoDB®, Mongo and the leaf logo are the registered trademarks of MongoDB, Inc.