#!/bin/sh -e
DEFAULT_ORG="Asterisk"
DEFAULT_CA_CN="Asterisk Private CA"
DEFAULT_CLIENT_CN="asterisk"
DEFAULT_SERVER_CN=`hostname -f`

# arguments
# $1 "ca" if we are to generate a CA cert
# $2 alternate config file name (for ca)
# $3 alternate common name
# $4 alternate org name
create_config () {
	if [ "$1" = "ca" ]
	then
castring="
[ext]
basicConstraints=CA:TRUE"
	fi

cat > ${2:-"${CONFIG_FILE}"} << EOF
[req]
distinguished_name = req_distinguished_name
prompt = no

[req_distinguished_name]
CN=${3:-"${COMMON_NAME}"}
O=${4:-"${ORG_NAME}"}
${castring}
EOF
}

create_ca () {
	echo "Creating ${CAKEY}"
	openssl genrsa -des3 -out ${CAKEY} 4096 > /dev/null
	echo "Creating ${CACERT}"
	openssl req -new -config ${CACFG} -x509 -days 365 -key ${CAKEY} -out ${CACERT} > /dev/null
}

create_cert () {
	local base=${OUTPUT_DIR}/${OUTPUT_BASE}
	echo "Creating ${base}.key"
	openssl genrsa -out ${base}.key 1024 > /dev/null
	echo "Creating signing request"
	openssl req -batch -new -config ${CONFIG_FILE} -key ${base}.key -out ${base}.csr > /dev/null
	echo "Creating ${base}.crt"
	openssl x509 -req -days 365 -in ${base}.csr -CA ${CACERT} -CAkey ${CAKEY} -set_serial 01 -out ${base}.crt > /dev/null
	echo "Combining key and crt into ${base}.pem"
	cat ${base}.key > ${base}.pem
	cat ${base}.crt >> ${base}.pem
}

usage () {
cat << EOF
This script is useful for quickly generating self-signed CA, server, and client
certificates for use with Asterisk. It is still recommended to obtain
certificates from a recognized Certificate Authority and to develop an
understanding how SSL certificates work. Real security is hard work.

OPTIONS:
  -h  Show this message
  -m  Type of cert "client" or "server". Defaults to server.
  -f  Config filename (openssl config file format)
  -c  CA cert filename (creates new CA cert/key as ca.crt/ca.key if not passed)
  -k  CA key filename
  -C  Common name (cert field)
        For a server cert, this should be the same address that clients
        attempt to connect to. Usually this will be the Fully Qualified
        Domain Name, but might be the IP of the server. For a CA or client
        cert, it is merely informational. Make sure your certs have unique
        common names.
  -O  Org name (cert field)
        An informational string (company name)
  -o  Output filename base (defaults to asterisk) 
  -d  Output directory (defaults to the current directory)

Example:

To create a CA and a server (pbx.mycompany.com) cert with output in /tmp:
  ast_tls_cert -C pbx.mycompany.com -O "My Company" -d /tmp

This will create a CA cert and key as well as asterisk.pem and the the two
files that it is made from: asterisk.crt and asterisk.key. Copy asterisk.pem
and ca.crt somewhere (like /etc/asterisk) and set tlscertfile=/etc/asterisk.pem
and tlscafile=/etc/ca.crt. Since this is a self-signed key, many devices will
require you to import the ca.crt file as a trusted cert.

To create a client cert using the CA cert created by the example above:
  ast_tls_cert -m client -c /tmp/ca.crt -k /tmp/ca.key -C "Joe User" -O \\
    "My Company" -d /tmp -o joe_user

This will create client.crt/key/pem in /tmp. Use this if your device supports
a client certificate. Make sure that you have the ca.crt file set up as
a tlscafile in the necessary Asterisk configs. Make backups of all .key files
in case you need them later.
EOF
}

if ! type openssl >/dev/null 2>&1
then
	echo "This script requires openssl to be in the path"
	exit 1
fi

OUTPUT_BASE=asterisk # Our default cert basename
CERT_MODE=server
ORG_NAME=${DEFAULT_ORG}

while getopts "hf:c:k:o:d:m:C:O:" OPTION
do
	case ${OPTION} in
		h)
			usage
			exit 1
			;;
		f)
			CONFIG_FILE=${OPTARG}
			;;
		c)
			CACERT=${OPTARG}
			;;
		k)
			CAKEY=${OPTARG}
			;;
		o)
			OUTPUT_BASE=${OPTARG}
			;;
		d)
			OUTPUT_DIR=${OPTARG}
			;;
		m)
			CERT_MODE=${OPTARG}
			;;
		C)
			COMMON_NAME=${OPTARG}
			;;
		O)
			ORG_NAME=${OPTARG}
			;;
		?)
			usage
			exit
			;;
	esac
done

if [ -z "${OUTPUT_DIR}" ]
then
	OUTPUT_DIR=.
else
	mkdir -p "${OUTPUT_DIR}"
fi

umask 177

case "${CERT_MODE}" in
	server)
		COMMON_NAME=${COMMON_NAME:-"${DEFAULT_SERVER_CN}"}
		;;
	client)
		COMMON_NAME=${COMMON_NAME:-"${DEFAULT_CLIENT_CN}"}
		;;
	*)
		echo
		echo "Unknown mode. Exiting."
		exit 1
		;;
esac

if [ -z "${CONFIG_FILE}" ]
then
	CONFIG_FILE="${OUTPUT_DIR}/tmp.cfg"
	echo
	echo "No config file specified, creating '${CONFIG_FILE}'"
	echo "You can use this config file to create additional certs without"
	echo "re-entering the information for the fields in the certificate"
	create_config
fi

if [ -z ${CACERT} ]
then
	CAKEY=${OUTPUT_DIR}/ca.key
	CACERT=${OUTPUT_DIR}/ca.crt
	CACFG=${OUTPUT_DIR}/ca.cfg
	create_config ca "${CACFG}" "${DEFAULT_CA_CN}" "${DEFAULT_CA_ORG}"
	create_ca
fi

create_cert