[client-kms] Setting AWS_SDK_LOAD_CONFIG does not enable region loading from config file

[ProjectFrank]

Checkboxes for prior research

• I've gone through Developer Guide and API reference
• I've checked AWS Forums and StackOverflow.
• I've searched for previous similar issues and didn't find any solution.

Describe the bug

Setting AWS_SDK_LOAD_CONFIG=true does not allow the KMSClient constructor (called with no arguments) to use the region specified in ~/.aws/config.

Regression Issue

• Select this option if this issue appears to be a regression.

SDK version number

@aws-sdk/client-kms@npm:^3.658.0

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

v20.9.0

Reproduction Steps

Contents of ~/.aws/config:
[default]
region = us-east-1

Snippet:

import { KMSClient, GenerateMacCommand } from '@aws-sdk/client-kms';

const client = new KMSClient();
const keyArn = 'your-key-arn';
const command = new GenerateMacCommand({
  Message: Buffer.from('abc'),
  KeyId: keyArn,
  MacAlgorithm: 'HMAC_SHA_512',
});
await client.send(command);

Observed Behavior

When using the above snippet to make a request, I encounter the following error:

Unhandled error Error: getaddrinfo ENOTFOUND kms.undefined.amazonaws.com

Expected Behavior

I expect the command to work (e.g. by sending a request to kms.us-east-1.amazonaws.com).

Possible Solution

No response

Additional Information/Context

smithy-codegen

[aBurmeseDev]

Hi @ProjectFrank - thanks for reaching out.

Before I further look into the issue, there are a couple of things I'd like to confirm:

• Are you able to successfully execute the code when you explicitly specify the region in the client constructor? For example, new KMSClient({region: 'us-east-1'}).
• If possible, could you try running a different AWS client with the environment variable AWS_SDK_LOAD_CONFIG="true"? This may provide additional insights into the problem.

---

I'll share these docs for your reference:

• Use a shared config file - https://docs.aws.amazon.com/sdk-for-javascript/v3/developer-guide/setting-region.html#setting-region-config-file
• Shared config and credentials files - https://docs.aws.amazon.com/sdkref/latest/guide/file-format.html

[ProjectFrank]

Yes, the code works correctly when the region is explicitly specified.

Strangely enough, the client also doesn't seem to be picking up the region when specifying the region by running export AWS_REGION=us-east-1.

I can try to find time and put together a snippet using a different sdk.

[ProjectFrank]

This may be a problem having to do with running the code via https://github.com/dherault/serverless-offline . I will close this issue for now.

[github-actions]

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