java - How can I deduce the AWS Account ID from available BasicAWSCredentials?

Question

Can't seem to find this anywhere in the docs; if I am authenticated with BasicAWSCredentials, e.g. AccessKeyId and SecretKey, is it possible to get the AWS Account ID?

Answer 1

Update

AWS has just silently addressed this long standing gap by introducing the dedicated STS API action GetCallerIdentity, which returns details about the IAM identity whose credentials are used to call the API, including the AWS Account ID - there are a few sample responses, e.g.:

<GetCallerIdentityResponse xmlns="https://sts.amazonaws.com/doc/2011-06-15/">
  <GetCallerIdentityResult>
   <Arn>arn:aws:iam::123456789012:user/Alice</Arn>
    <UserId>AKIAI44QH8DHBEXAMPLE</UserId>
    <Account>123456789012</Account>
  </GetCallerIdentityResult>
  <ResponseMetadata>
    <RequestId>01234567-89ab-cdef-0123-456789abcdef</RequestId>
  </ResponseMetadata>
</GetCallerIdentityResponse>

You can use the AWS Command Line Interface to obtain just the account ID, here's an example:

$ aws sts get-caller-identity --output text --query Account
121371349383

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Initial Answer

This is at least indirectly possible via AWS Identity and Access Management (IAM) by means of the GetUser action (available via getUser() in the AWS SDK for Java):

Retrieves information about the specified user, including the user's path, GUID, and ARN.

If you do not specify a user name, IAM determines the user name implicitly based on the AWS Access Key ID signing the request.

The returned User data type (Class User) contains an Arn element (getArn()), which is the Amazon Resource Name (ARN) specifying the user. This is further detaild in Identifiers for IAM Entities, specifically in section ARNs, which describes the format of the User Resource Type:

arn:aws:iam::{account_ID}:user/{path/to/user/UserName}

Example: arn:aws:iam::123456789012:user/division_abc/subdivision_xyz/Bob