Credentials object returned from sts.assumeRole cannot be used as credentials for clients

[jonpbbc]

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

If you use sts.assumeRole to get session credentials for an assumed role and then pass those credentials to a client the case mis-match means you recieve the TypeError: Cannot read property 'byteLength' of undef described in #2282

This doesn't feel like a documentation error as in #3268, as I am trying to use SDK objects to populate SDK objects.

SDK version number

"@aws-sdk/client-iam": "^3.154.0", "@aws-sdk/client-sts": "^3.168.0"

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

Node 14 via aws/codebuild/standard:5.0

Reproduction Steps

      const sts = new STS()
      const assumeRoleResponse = await sts.assumeRole({ "RoleArn": `arn:aws:iam::${accountId}:role/${roleName}`, "RoleSessionName": sessionName" })
      const iam = new IAM({ credentials: assumeRoleResponse.Credentials})
      const response = await iam.listPolicies({ "Scope": "AWS, "MaxItems": 1 })

Observed Behavior

TypeError: Cannot read property 'byteLength' of undefined as per #2282

Expected Behavior

I would expect to be able to use the returned Credentials object as the credentials for constructing a subsequent client object.

Possible Solution

No response

Additional Information/Context

Work-around to avoid error:

      const sts = new STS()
      const assumeRoleResponse = await sts.assumeRole({ "RoleArn": `arn:aws:iam::${accountId}:role/${roleName}`, "RoleSessionName": sessionName" })
      const iam = new IAM({ credentials: {
        accessKeyId: assumeRoleResponse.Credentials.AccessKeyId,
        secretAccessKey: assumeRoleResponse.Credentials.SecretAccessKey,
        sessionToken: assumeRoleResponse.Credentials.SessionToken
       }})
      const response = await iam.listPolicies({ "Scope": "AWS, "MaxItems": 1 })

[RanVaknin]

Hi @jonpbbc ,

Thanks for opening the issue and engaging in the community.

I think the reason your first code snippet isn't working as expected is because Client credentials and the Credential object returned from STS are of different type.

Type 'Credentials | undefined' is not assignable to type 'Credentials | Provider | undefined'.
Type 'Credentials' is not assignable to type 'Credentials | Provider | undefined'.ts(2322)

I'd say the "work around" is the correct way to make that request. Did you reference an official example or docs for the first code snippet you have provided?

All the best,
Ran~

[jonpbbc]

Hi @RanVaknin ,

I was working from the documentation, specifically the IAM client config as part of calling the IAM constructor. That references this Credentials interface and when I saw the assume role output contains a object of type Credentials I have absolutely believed that Credentials and Credentials are the same type.

If Credentials is not supposed to be the same type as Credentials then I would say that the duplicate naming is the root of this issue - but given the purpose of both Credentials types is to return or supply the same logical data, with the same names, I completely it expect it to be compatible within the same overall API. If they are not supposed to be compatible, I propose the renaming of the types so Credentials is not confused with Credentials - but as a user of the API I would much rather they be made compatible.

My route to the work around was searching for the TypeError in relation to the SDK and finding #2282 - not really an intuitive path.

Hope that helps,

Jon

[RanVaknin]

Hi Jon,

Thanks for your response! I totally see what you are saying and it makes a lot of sense. I'll speak with the development team regarding this issue and will raise a backlog item.

In the spirit of transparency I'll share that the team is slammed, and since this has a workaround it will get lower priority, but will get addressed later on.

Thanks again for being an active member in the community, we hope to hear back from you!
All the best,
Ran~