Feature request: Use the aws-cli cache

[eddieSullivan]

Problem:

When making multiple encryption/decryption requests to aws-encryption-cli, if you have MFA enabled, an MFA key is required for every request.

This differs from the standard aws command-line program, which caches credentials in "~/.aws/cli/cache" (at least that's where it goes in my system, running MacOS).

Solution:

It would be great if aws-encryption-cli could use that same credential cache so we wouldn't have to enter an MFA token for each invocation of the command.

I did a test by running an aws command to populate the cache, then manually extracting values from the JSON file in the cache to populate the credential environment variables AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN, and then calling aws-encryption-cli. That worked -- it did not ask me for an MFA token.

Thanks in advance. I know this would help my workflow tremendously, and I suspect many others would benefit as well.