Rusoto: StsAssumeRoleSessionCredentialsProvider is not using the session_duration attribute & is calling assume role with each request.

[ksamykandil]

There is a bug in the StsAssumeRoleSessionCredentialsProvider that a new request to assume role is done with each request of AWS resource & the session_duration parameter is not used for caching.

This cause a huge load on performance & throttling the Assume role API if you have a high load.

This value is valid for one hour, so it should be used till it expires as it blocks the cross account usage of Rusoto.

Example: Kinesis stream get records API is calling Assume Role with each request which shouldn't be the case.

[ksamykandil]

1. rusoto_credential::AutoRefreshingProvider is the solution to wrap the StsAssumeRoleSessionCredentialsProvider.

2. StsAssumeRoleSessionCredentialsProvider should have AutoRefreshingProvider implementation so it will be there by default.

3. The documentation part of the example using the StsAssumeRoleSessionCredentialsProvider should be updated to avoid such issues.

[matthewkmayer]

Thanks for the bug report and the writeup on how you found it. I wish it was discovered in a less expensive way, though. 😭

At the very least we should get a PR for point three: update the documentation to explain current behavior. I really want to keep others from getting a surprise bill like that!

On a more general note, our STS testing is lackluster and should be improved.

[ksamykandil]

@matthewkmayer I'm working on the fix, will be ready in a week hopefully, will update the documentation as well & make a pull request.

[ksamykandil]

@matthewkmayer I made a pull request for the documentation update.
https://github.com/rusoto/rusoto/pull/1181

Thanks!

[copumpkin]

Is it likely that the STS provider will eventually include the auto refreshing behavior itself? It seems pretty counterintuitive to have to wrap it before getting sensible behavior, but I could see some argument for the current behavior.

[matthewkmayer]

Yes, the STS provider should get auto refreshing and caching behavior. Nobody's gotten around to doing that yet. 😄

I think it could be done by using the re-exported rusoto_credential crate from rusoto_core and making some custom code for STS. Making the workaround part of the STS crate so it can be found and used. 👍