google-oauth2.sh

#!/usr/bin/env bash

# A simple curl OAuth2 authenticator
#
# Usage:
#	./google-oauth2.sh create - authenticates a user
#	./google-oauth2.sh refresh <token> - gets a new token
#
# Set CLIENT_ID and CLIENT_SECRET and SCOPE
# See SCOPES at https://developers.google.com/identity/protocols/oauth2/scopes#docsv1

shortHelp() {
    printf "
No valid arguments provided.
Usage:

 ./%s create - authenticates a user.
 ./%s refresh - gets a new access token.

  Use update as second argument to update the local config with the new REFRESH TOKEN.
  e.g: ./%s create/refresh update\n" "${0##*/}" "${0##*/}" "${0##*/}"
    exit 0
}

[[ ${1} = create ]] || [[ ${1} = refresh ]] || shortHelp

[[ ${2} = update ]] && UPDATE="updateConfig"

# Move cursor to nth no. of line and clear it to the begining.
clearLine() {
    printf "\033[%sA\033[2K" "${1}"
}

# Method to extract data from json response.
# Usage: jsonValue key < json ( or use with a pipe output ).
jsonValue() {
    [[ $# = 0 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 1
    declare LC_ALL=C num="${2:-1}"
    grep -o "\"""${1}""\"\:.*" | sed -e "s/.*\"""${1}""\": //" -e 's/[",]*$//' -e 's/["]*$//' -e 's/[,]*$//' -e "s/\"//" -n -e "${num}"p
}

# Remove array duplicates, maintain the order as original.
# Usage: removeArrayDuplicates "${somearray[@]}"
# https://stackoverflow.com/a/37962595
removeArrayDuplicates() {
    [[ $# = 0 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 1
    declare -A Aseen
    Aunique=()
    for i in "$@"; do
        { [[ -z ${i} || ${Aseen[${i}]} ]]; } && continue
        Aunique+=("${i}") && Aseen[${i}]=x
    done
    printf '%s\n' "${Aunique[@]}"
}

# Update Config. Incase of old value, update, for new value add.
# Usage: updateConfig valuename value configpath
updateConfig() {
    [[ $# -lt 3 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 1
    declare VALUE_NAME="${1}" VALUE="${2}" CONFIG_PATH="${3}" FINAL=()
    printf "" >> "${CONFIG_PATH}" # If config file doesn't exist.
    mapfile -t VALUES < "${CONFIG_PATH}" && VALUES+=("${VALUE_NAME}=\"${VALUE}\"")
    for i in "${VALUES[@]}"; do
        [[ ${i} =~ ${VALUE_NAME}\= ]] && FINAL+=("${VALUE_NAME}=\"${VALUE}\"") || FINAL+=("${i}")
    done
    removeArrayDuplicates "${FINAL[@]}" >| "${CONFIG_PATH}"
}

printf "Starting script..\n"

CLIENT_ID=""
CLIENT_SECRET=""
SCOPE="https://www.googleapis.com/auth/drive"
REDIRECT_URI="urn:ietf:wg:oauth:2.0:oob"
TOKEN_URL="https://accounts.google.com/o/oauth2/token"

# shellcheck source=/dev/null
[[ -f ${HOME}/.googledrive.conf ]] && source "${HOME}"/.googledrive.conf

printf "Checking credentials..\n"

# Credentials
if [[ -z ${CLIENT_ID} ]]; then
    read -r -p "Client ID: " CLIENT_ID
    [[ -z ${CLIENT_ID} ]] && printf "Error: No value provided.\n" 1>&2 && exit 1
    updateConfig CLIENT_ID "${CLIENT_ID}" "${HOME}"/.googledrive.conf
fi
if [[ -z ${CLIENT_SECRET} ]]; then
    read -r -p "Client Secret: " CLIENT_SECRET
    [[ -z ${CLIENT_SECRET} ]] && printf "Error: No value provided.\n" 1>&2 && exit 1
    updateConfig CLIENT_SECRET "${CLIENT_SECRET}" "${HOME}"/.googledrive.conf
fi

for _ in {1..2}; do clearLine 1; done

if [[ ${1} = create ]]; then
    printf "Required credentials set.\n"
    printf "Visit the below URL, tap on allow and then enter the code obtained:\n"
    URL="https://accounts.google.com/o/oauth2/auth?client_id=${CLIENT_ID}&redirect_uri=${REDIRECT_URI}&scope=${SCOPE}&response_type=code&prompt=consent"
    printf "%s\n\n" "${URL}"
    read -r -p "Enter the authorization code: " CODE

    CODE="${CODE//[[:space:]]/}"
    if [[ -n ${CODE} ]]; then
        RESPONSE="$(curl --compressed -s -X POST --data "client_id=${CLIENT_ID}&client_secret=${CLIENT_SECRET}&refresh_token=${REFRESH_TOKEN}&grant_type=refresh_token" ${TOKEN_URL})"

        ACCESS_TOKEN="$(jsonValue access_token <<< "${RESPONSE}")"
        REFRESH_TOKEN="$(jsonValue refresh_token <<< "${RESPONSE}")"

        if [[ -n ${ACCESS_TOKEN} && -n ${REFRESH_TOKEN} ]]; then
            "${UPDATE:-:}" REFRESH_TOKEN "${REFRESH_TOKEN}" "${CONFIG:-${HOME}/.googledrive.conf}"
            "${UPDATE:-:}" ACCESS_TOKEN "${ACCESS_TOKEN}" "${CONFIG:-${HOME}/.googledrive.conf}"

            printf "Access Token: %s\n" "${ACCESS_TOKEN}"
            printf "Refresh Token: %s\n" "${REFRESH_TOKEN}"
        else
            printf "Error: Wrong code given, make sure you copy the exact code\n"
            exit 1
        fi
    else
        printf "\nNo code provided, run the script and try again.\n"
        exit 1
    fi
elif [[ ${1} = refresh ]]; then
    # Method to regenerate access_token ( also updates in config ).
    # Make a request on https://www.googleapis.com/oauth2/""${API_VERSION}""/tokeninfo?access_token=${ACCESS_TOKEN} url and check if the given token is valid, if not generate one.
    # Requirements: Refresh Token
    getTokenandUpdate() {
        RESPONSE="$(curl --compressed -s -X POST --data "client_id=${CLIENT_ID}&client_secret=${CLIENT_SECRET}&refresh_token=${REFRESH_TOKEN}&grant_type=refresh_token" "${TOKEN_URL}")"
        ACCESS_TOKEN="$(jsonValue access_token <<< "${RESPONSE}")"
        "${UPDATE:-:}" ACCESS_TOKEN "${ACCESS_TOKEN}" "${CONFIG:-${HOME}/.googledrive.conf}"
    }
    if [[ -n ${REFRESH_TOKEN} ]]; then
        printf "Required credentials set.\n"
        getTokenandUpdate
        clearLine 1
        printf "Access Token: %s\n" "${ACCESS_TOKEN}"
    else
        printf "Refresh Token not set, use %s create to generate one.\n" "${0}"
    fi
fi