AWS STS - GET SESSION TOKEN WITH MFA allowing CLI access to commands without switching to an IAM Role

aws_get_session_token.sh

#!/usr/bin/env bash
# shellcheck disable=2086,2162,2005,2046,1091

# GET AWS SESSION TOKEN WITH MFA
#   allowing CLI access to commands without switching to an IAM Role, e.g. for accessing the Well-Architected Tool

source colours > /dev/null 2>&1  # import colours script if it exists in the PATH

usage(){
  echo "
Get session token with MFA, allowing CLI access to commands without switching 
to an IAM Role, e.g. accessing the Well-Architected Tool

Add alias to .bashrc, .zshrc or equivalent:
  alias aws-get-session-token=\"source aws-get-session-token\"
"
}

if [[ "$*" == *"-d"* ]] || [[ "$*" == *"debug"* ]] || [[ "$*" == *"DEBUG"* ]]; then DEBUG=true; fi
if [[ "$*" == *"-h"* ]] || [[ "$*" == *"help"* ]]; then usage; return; fi

get_mfa(){
  echo
  echo -n "${RED}Enter MFA Token:${NORM} "
  read TOKENCODE
  if [[ -z $TOKENCODE ]]; then echo "${YELLOW}No MFA token supplied${NORM}"; return 1; fi
}

get_user_details(){
  read -r \
    USERARN \
    ACCOUNTID \
      < <(echo $(aws sts get-caller-identity --out json | jq -r '. | .Arn, .Account'))
  MFAARN="${USERARN/\:user\//:mfa/}"
  IAMUSER="${USERARN#*/}"
  echo "${YELLOW}IAM User : ${IAMUSER}${NORM}"
  echo "${YELLOW}Account  : ${ACCOUNTID}${NORM}"

  if [[ -n $DEBUG ]]; then
    echo "${YELLOW}User Arn : ${USERARN}${NORM}"
    echo "${YELLOW}MFA Arn  : ${MFAARN}${NORM}"
  fi
}

get_token(){
  aws sts get-session-token --serial-number ${MFAARN} --token-code ${TOKENCODE} \
    | jq -r '.Credentials | .AccessKeyId, .SecretAccessKey, .SessionToken, .Expiration'
}

get_token_vars(){
  read -r \
    AWS_ACCESS_KEY_ID \
    AWS_SECRET_ACCESS_KEY \
    AWS_SESSION_TOKEN \
    AWS_SESSION_TOKEN_EXPIRY \
      < <(echo $(get_token))

  export AWS_ACCESS_KEY_ID
  export AWS_SECRET_ACCESS_KEY
  export AWS_SESSION_TOKEN
  export AWS_SESSION_TOKEN_EXPIRY
}

if (return 0 2>/dev/null); then
  get_user_details && \
  get_mfa && \
  get_token_vars && \
  echo -e "\n${GREEN}${BOLD}Token expiry: ${AWS_SESSION_TOKEN_EXPIRY}${NORM}\n"
else echo "${RED}This script has to be sourced${NORM}"; usage; 
fi