Bash script to set MFA IAM session in environment variables

mfa-env

#!/bin/bash
#description     : Set MFA session in environment variables
#usage           : source mfa-env [token-from-mfa-device]
#requirements    : Install aws-cli v2

mfa_config=~/.aws/mfa
mfa_device_arn=""
mfa_token="${1-}"

if [ ! -f $mfa_config ]; then
  echo "Please create a config file at ~/.aws/mfa!"
  echo "Config should contain line with \"mfa-device = mfa-device-arn\"."
  echo
  return 1
fi

while IFS= read -r line; do
  if [[ $line == mfa-device* ]]; then
    mfa_device_arn="${line/mfa-device = /}"
  fi
done < $mfa_config

if [[ "$mfa_device_arn" == "" ]]; then
  echo "Config should contain line with \"mfa-device = mfa-device-arn\"."
  return 2
fi

if [[ "$mfa_token" == "" ]]; then
  echo "\`mfa-env\` must be called with the current MFA token from your device!"
  return 3
fi

# Can't run get-session-token with session credentials!
unset AWS_ACCESS_KEY_ID
unset AWS_SECRET_ACCESS_KEY
unset AWS_SESSION_TOKEN

credentials=($(aws sts get-session-token --serial-number "$mfa_device_arn" --token-code "$mfa_token" --output text))

[ $? -ne 0 ] && return 4

export AWS_ACCESS_KEY_ID="${credentials[2]}"
export AWS_SECRET_ACCESS_KEY="${credentials[4]}"
export AWS_SESSION_TOKEN="${credentials[5]}"