oauth-token.sh

#!/bin/bash
# vim: tabstop=4

GRANT_TYPE='client_credentials'

###############  Functions  ###############

parse_json() {
	local input=$1
	local attr=$2
	python -c "import json;obj=json.loads('$input');print(obj['$attr'])" 2>/dev/null
}

###############  Arguments  ###############

usage() {
	cat <<-EOF
		Damn simple cript to requests access token from OAuth 2.0 authorization server.

		Usage: ${scriptname} <options>

		Options:
		-c, --client-id CLIENT_ID
		-p, --client-secret SECRET
		-s, --scope SCOPE...
		-u, --oaas-uri URI
		-v, --verbose
		-h, --help
	EOF
}

scriptname=$(basename $0)
client=
secret=
scope=()
oaas_uri='https://auth.fit.cvut.cz'
verbosity='silent'

while [ $# -gt 0 ]; do
	case $1
	in
		-c | --client-id)
			client=$2
			shift 2
	;;
		-h | --help)
			usage
			exit 0
	;;
		-p | --client-secret)
			secret=$2
			shift 2
	;;
		-s | --scope)
			scope+=("$2")
			shift 2
	;;
		-u | --oaas-uri)
			oaas_uri=$2
			shift 2
	;;
		-v | --verbose)
			verbosity='verbose'
			shift 1
	;;
		*)
			echo "${scriptname}: Unknown option $1" >&2
			echo; usage
			exit 1
	;;
	esac
done

if [[ -z "$client" || -z "$secret" ]]; then
	echo "${scriptname}: Missing CLIENT_ID or SECRET" >&2
	echo; usage
	exit 1
fi


###############  Main  ###############

data="grant_type=${GRANT_TYPE}"
if [ -n "$scope" ]; then
	data+="&scope=${scope[@]}"
fi

curl_opts="
	--data "$data" \
	--header 'Content-Type: application/x-www-form-urlencoded' \
	--user ${client}:${secret} \
	--$verbosity"

response=$(curl $curl_opts "${oaas_uri}/oauth/token")
token=$(parse_json "$response" 'access_token')

if [ $? -eq 0 ]; then
	echo $token
else
	echo "Failed with response: $response" >&2
	exit 2
fi