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I am in the early stages of writing an AWS app for our users that will run our research algorithms using their AWS resources. For example, our code will need to spin up EC2 instances running our 'worker' app, access RDS databases, and create access SQS queues. The AWS Java SDK examples (we are writing this in Java) use a AwsCredentials.properties file to store the Access Key ID and Secret Access Key, which is fine for examples, but obviously not acceptable for our users, who are would be in essence giving us access to all their resources. What is a clean way to go about running our system on their behalf? I discovered AWS Identity and Access Management (IAM) which seems to be for this purpose (I haven't got my head around it yet), esp. Cross-account access between AWS accounts. This post makes it sound straightforward:

Use the amazon IAM service to create a set of keys that only has permission to perform the tasks that you require for your script. http://aws.amazon.com/iam/

However, other posts (e.g., Within IAM, can I restrict a group of users to access/launch/terminate only certain EC2 AMIs or instances?) suggest there are limitations to using IAM with EC2 in particular.

Any advice would be really helpful!

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Matthew Cornell
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The key limitation with regards to RDS and EC2 is that while you can restrict access to certain API actions there are no resource level constraints. For example with an IAM S3 policy you can restrict a user to only being able to perform certain actions on certain buckets. You can write a policy for EC2 that says that user is allowed to stop instances, but not one that says you can only stop certain instances.

Another option is for them to provide you with temporary credentials via the Security Token Service. Another variant on that is to use the new IAM roles service. With this an instance has a set of policies associated with it. You don't need to provide an AwsCredentials.proprties file because the SDK can fetch credentials from the metadata service.

Finally one last option might be consolidated billing. If the reason you are using their AWS resources is just because of the billing, then setup a new account which is billed from their account. The accounts are isolated from each other so you can't for example delete their instances by accident. Equally you can't access their RDS snapshots and things like that (access to an RDS instance via mysql (as opposed to the AWS api) would depend on the instance's security group). You can of course combine this with the previous options - they could provide you with credentials that only allow you to perform certain actions within that isolated account.

Frederick Cheung
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