如何在 .NET AWS SDK 中担任角色

Question

I'm trying to build a .net core mvc app that allows the user to send data to a dynamodb, but I can't seem to assume the role for permissions to describe my table. I get the following error every time I try:

Unable to get IAM security credentials from EC2 Instance Metadata Service

First I have my controller (Index is where the user form is submitted):

public class RfiController : Controller
{
    private readonly IDynamoDBClient capture;
    public RfiController(IDynamoDBClient dynamodb)
    {
        capture = dynamodb;
    }
    . . .
    [HttpPost]
    [ValidateAntiForgeryToken]
    public IActionResult Index(ViewModel Model)
    {
            . . .
            ///ASSUME THE role
            ConfigProvider config = new ConfigProvider();
            config.AWSRoleName = "rolename";
            config.AWSRegion = "region";
            config.Environment = "dev";
            capture.DynamoDBClientService(config);
            return View(Model);
        }
    }
}

This calls a library I created to handle my dynamodb connections and stuff. Here is the class:

public class DynamoDBClient: IDynamoDBClient
{
    private readonly IAmazonDynamoDB _client;
    public DynamoDBClient(IAmazonDynamoDB dynamoDBClient)
    {
         _client = dynamoDBClient;
    }

    public void DynamoDBClientService(ConfigProvider config)
    {
        try
        {
            DescribeTableRequest request = new DescribeTableRequest
            {
                TableName = "tablename"
            };
            var result = _client.DescribeTableAsync(request);

            var status = result.Result.Table.TableStatus;
        }
        catch (Exception ex) //I catch and error `Unable to get IAM security credentials from EC2 Instance Metadata Service` here
        {
            throw ex;
        }
    }

    static AssumeRoleResponse GetAssumeRoleResponseAsync(AmazonSecurityTokenServiceClient client, AssumeRoleRequest request)
    {
        AssumeRoleResponse response;
        try
        {
            response = client.AssumeRoleAsync(request).Result;

        }
        catch (Exception ex)
        {
            throw ex;
        }
        return response;
    }
}

I'm of course using my aws account in a credentials file. When I try to run the app, I catch an error where I have specified. How am i doing this wrong? I'm about as new to the aws sdk as one can be, so please forgive me of the answer if obvious.

Answer 1

It's better if you can create an IAM role and attach it to your instance on which you are running the.Net code.

IAM Role: https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles.html

Also, make sure that you can reach the metadata url from within the instance: http://169.254.169.254/latest/meta-data/

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instancedata-data-retrieval.html