Thomas Sandmann’s blog - Refreshing & exporting temporary AWS credentials

To increase security when interacting with AWS services, the AWS IAM Identity Center (formerly known as AWS SSO) generates temporary credentials for different AWS roles.

Today I learned how to configure and refresh these credentials in the command line, as well how to export them either as environmental variables or write them to the credentials file where tools that do not interact with AWS SSO natively can access them.

Configuring an AWS SSO profile

First, we need to configure a named profile for use with AWS SSO. The following AWS CLI version 2 command will interactively walk you through the necessary steps:

aws configure sso

The information you provide will be written to the config file, located in the ~/.aws directory on Mac OS. Here is an example:

[profile my-dev-profile]
sso_start_url = https://my-sso-portal.awsapps.com/start
sso_region = us-east-1
sso_account_id = 123456789011
sso_role_name = readOnly
region = us-west-2
output = json

Logging into the AWS SSO profile

Now we can log into AWS SSO and request temporary credentials:

aws sso login --profile my-dev-profile

This command will try to open a web browser for you and prompt you to confirm the login. Alternatively, you can copy & paste the displayed URL and manually enter the confirmation code output by the command.

If the login was successful, you can now adopt the my-dev-profile when using the AWS CLI, e.g.

aws s3 ls --profile my-dev-profile

The AWS SSO endpoint recognizes many environmental variables that you can use to specify defaults, e.g.

AWS_PROFILE: The profile to use (e.g. my-dev-profile)
AWS_SHARED_CREDENTIALS_FILE: the location of the shared credentials files (default on Mac OS: ~/.aws/.credentials)
AWS_CONFIG_FILE: the location of the AWS CLI configuration file (default on Mac OS: ~/.aws.config)

Accessing temporary credentials

The AWS CLI and many of the AWS SKDs will automatically detect and use SSO credentials. But other tools might not (yet) be compatible with this authentication route. Instead, they might

read credentials for a profile from the credentials file
rely on environmental variables, e.g. AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY

To expose the temporary credentials, Ben Kehoe has made the aws-export-credentials tool available.

Installing aws-export-credentials

The recommended way to install aws-export-credentials is via pipx because it will automatically make it available in your PATH.

If you don’t have pipx available on your system, install it first.
Next, install aws-export-credentials by executing the following steps in your shell:

pipx ensurepath  # in case you haven't run this before
pipx install aws-export-credentials
aws-export-credentials --version  # verify the installation

Updating the credentials file

At the beginning of your workday - or whenever needed - run the following set of commands. (Replace the SSO profile with the one you want to adopt.)

PROFILE="my-dev-profile"

# retrieve new credentials from AWS
aws sso login --profile "${PROFILE}"

# write the temporary credentials to the ~/.aws/credentials file
aws-export-credentials \
  --profile "${PROFILE}" \
  --credentials-file-profile "${PROFILE}"

This will refresh the credentials (via aws sso login) and then write them to the my-dev-profile profiles in the ~/.aws/.credentials file. Now we can access them e.g. in the aws.s3 R package:

library(aws.s3)
library(aws.signature)
aws.signature::use_credentials(profile = "my-dev-profile")
aws.s3::bucketlist()

Exposing environmental variables

Some tools only recognize environmental variables. Luckily, aws-export-credentials can automate this process, too:

export $(aws-export-credentials --profile my-dev-profile --env-export)

will export AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY variables in your shell session.

Sourcing credentials with an external process

Finally, you can also include a command that looks up credentials as a credential_process in your config file. (More information here) But that’s not a use case I have explored, yet.

This work is licensed under a Creative Commons Attribution 4.0 International License.