When using AWS authentication with Atlas, the connection can only be established when the access key, secret, and session token are specified either explicitly as options or as part of the connection string.

When these are set as environment variables (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN), authentication does not work.

Only tested with driver v4 - not 3.x.

Relevant part of the spec: https://github.com/mongodb/specifications/blob/master/source/auth/auth.rst#environment-variables.