Simple DB policy being ignored?

Question

I'm trying to use AWS IAM to generate temporary tokens for a mobile app. I'm using the AWS C# SDK.

Here's my code...

The token generating service

public string GetIAMKey(string deviceId)
    {
        //fetch IAM key...

        var credentials = new BasicAWSCredentials("MyKey", "MyAccessId");

        var sts = new AmazonSecurityTokenServiceClient(credentials);

        var tokenRequest = new GetFederationTokenRequest();
        tokenRequest.Name = deviceId;
        tokenRequest.Policy = File.ReadAllText(HostingEnvironment.MapPath("~/policy.txt"));
        tokenRequest.DurationSeconds = 129600;

        var tokenResult = sts.GetFederationToken(tokenRequest);

        var details = new IAMDetails { SessionToken = tokenResult.GetFederationTokenResult.Credentials.SessionToken, AccessKeyId = tokenResult.GetFederationTokenResult.Credentials.AccessKeyId, SecretAccessKey = tokenResult.GetFederationTokenResult.Credentials.SecretAccessKey, };

        return JsonConvert.SerializeObject(details);
    }

The client

var iamkey = Storage.LoadPersistent<IAMDetails>("iamkey");

        var simpleDBClient = new AmazonSimpleDBClient(iamkey.AccessKeyId, iamkey.SecretAccessKey, iamkey.SessionToken);

        try
        {
            var details = await simpleDBClient.SelectAsync(new SelectRequest { SelectExpression = "select * from mydomain" });

            return null;
        }
        catch (Exception ex)
        {
            Storage.ClearPersistent("iamkey");
        }

The policy file contents

{ "Statement":[{ "Effect":"Allow", "Action":"sdb:* ", "Resource":"arn:aws:sdb:eu-west-1:* :domain/mydomain*" } ]}

I keep getting the following error...

User (arn:aws:sts::myaccountid:federated-user/654321) does not have permission to perform (sdb:Select) on resource (arn:aws:sdb:us-east-1:myaccountid:domain/mydomain)

Notice that my policy file clearly specifies two things

1. region should be eu-west-1
2. allowed action is a wild-card, ie, allow everything

But the exception thrown claims that my user doesn't have permission to us-east-1

Any ideas as to why I'm getting this error?

Answer 1

Ok figured it out.

You have to set the region endpoint on your call to the service from the client.

So

var simpleDBClient = new AmazonSimpleDBClient(iamkey.AccessKeyId, iamkey.SecretAccessKey, iamkey.SessionToken, Amazon.RegionEndpoint.EUWest1);