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Difficulty: MediumAWS SDKs and Credential Management

A developer is testing an application locally that uses the AWS SDK for JavaScript. The developer wants to ensure the SDK uses the correct IAM permissions. The following configurations exist on the developer's workstation:

* The environment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are set to valid credentials for Developer A.
* The shared credentials file (~/.aws/credentials) contains a [default] profile for Developer B and a [testing] profile for Developer C.
* The environment variable AWS_PROFILE is set to testing.

The SDK client is initialized in the code without any custom credential configuration arguments. Which credentials will the AWS SDK use when making API calls?

  1. A
    The credentials for Developer C, because the AWS_PROFILE environment variable overrides other environment variables to load the specific profile configuration.
  2. The credentials for Developer A, because environment variables have higher precedence in the SDK default credential provider chain than the shared credentials file.Answer
  3. C
    The credentials for Developer B, because the default profile in the shared credentials file is always resolved before environment variables are evaluated.
  4. D
    The credentials retrieved from AWS Systems Manager Parameter Store under the name specified by the AWS_PROFILE environment variable.

Answer

The credentials for Developer A, because environment variables have higher precedence in the SDK default credential provider chain than the shared credentials file.
The correct answer is the option stating that the credentials for Developer A are used. In the AWS SDK default credentials provider chain, individual environment variables (specifically AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY) have higher precedence than profile configurations in the shared credentials file. As a result, the SDK resolves Developer A's credentials and terminates its search.

Step-by-Step Solution

1
Analyze the SDK client initialization and check if custom credentials are provided.
The SDK is initialized without arguments, meaning it falls back to the default credentials provider chain.
This determines that the standard credential resolution order will be applied.
2
Check for environment variables containing explicit access keys.
AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are found containing credentials for Developer A.
Environment variables are evaluated at the beginning of the default credentials provider chain.
3
Determine if the resolution process stops or continues to other sources like AWS_PROFILE.
The credentials for Developer A are selected, and the search stops. The profiles in the shared credentials file are ignored.
Once the SDK resolves valid credentials in a high-precedence source, it stops searching further down the chain.

Key Concept

AWS SDK Default Credentials Provider Chain Precedence
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Topics

AWS SDKs and Credential Management

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