#!/bin/bash
usage() {
   echo "Script name: $0";
   echo "";
   echo "Usage: $0 --key-type [ RSA | EC | EX25519 ]";
   echo "                      --curve [ P-256 | P-384 | P512 ]";
   echo "                      --rsa-bits [ 2048 | 4096 ]";
   echo "                      --days <n>";
   echo "";
   echo "Options: ";
   echo "      --key-type [ RSA | EC | EC25519 ]";
   echo "          Note: Pico W can use EC or RSA keys only, not EC25519,";
   echo "                and Tasmota can only use 2048 bit RSA keys.";
   echo "      --curve [ P-256 | P-384 | P512 ]";
   echo "      --rsa-bits [ 2048 | 4096 ]";
   echo "      --days [ <integer> ]";
   echo "      --dir [ <mosquitto directory> ]";
   echo "      --output-format [ PEM | DER ]";
   echo "      --server_only [ True | False ]";
   echo "      --subjectAltName <subjectAltName>";
   echo "       Example subjectAltName: DNS.1:example.com,DNS.2:192.168.1.167,IP.1:192.168.1.167'";
}

# This creates a very slimline CA and Server cert with a full SAN multihost server.
# The Mosquitto server requires keys and certs in PEM format, but it also exports
# the CA Cert in DER for use in clients such as the Pico W
TEMP="$(getopt -o h --long help,key-type:,curve:,rsa-bits:,ca_valid_for:,days:,dir:,output-format:,server_only:,subjectAltName: -- "$@")"

eval set -- "$TEMP"

if [ $# == 0 ] ; then
    usage;
    exit 1;
fi

mosquitto_dir="/home/erg/cert_test_1"
key_type='EC'
curve='P-256'
rsa_bits='2048'
# Choice to encrypt the CA Key or not? either BLANK or cypher (preferably aes-256-cbc)
encryption=''
# encryption='-aes-256-cbc'
output_format='der'
# Multiple DNS names and IP Addresses. Note mbedtls can't currently use data from IP fields,
# but can read an IP from a DNS field, to the same effect.
# Use as many unique names as you need, in the format DNS.1, DNS.2, DNS.3, IP.1, IP.2 etc.
# subjectAltName='DNS.1:server_name,DNS.2:server_name.example.com,DNS.3:192.168.1.1,IP.1:192.168.1.1'
subjectAltName='DNS.1:example.com,DNS.2:192.168.0.167,IP.1:192.168.0.167'
ca_valid_for=3650
certs_valid_for=365
server_only="True"

while true
do
  case "$1" in
    -h|--help)
        usage
        exit 0;
        ;;
        # Note: Pico W can use EC or RSA keys only, not EC25519, and Tasmota can only use 2048 bit RSA keys.
        # Default choice of Key Types: RSA || EC || ED25519
    --key-type) key_type="$2"; shift 2;;
        # Choice of NIST Curves for EC Keys: P-256 || P-384 || P-521
    --curve) curve="$2"; shift 2;;
        # Choice of Bits for RSA Keys: 2048 || 4096
    --rsa-bits) rsa_bits="$2"; shift 2;;
        # How many days is the CA Cert valid for:
    --ca_valid_for) ca_valid_for="$2"; shift;;
        # How many days is the Cert valid for:
    --days) certs_valid_for="$2"; shift 2;;
        # Mosquitto directory:
    --dir) mosquitto_dir="$2"; shift 2;;
        # Output format: PEM ||  DER
    --output-format) output_format="$2"; shift 2;;
        # Only generate server certificate and key, not the CA. Defaults to True.
    --server_only) server_only="$2";shift 2;;
    --subjectAltName) subjectAltName="$2";shift 2;;
    -- ) shift; break;;
    * ) break;;
  esac
done

echo "subjectAltName you specified: $subjectAltName"

if [ "$server_only" == "True" ] || [ "$server_only" == "true" ]|| [ "$server_only" == "Yes" ] || [ "$server_only" == 'yes' ]; then
    server_only='True'
else
    server_only='False'
fi

# Mosquitto subdirectories:
mosquitto_dir_ca="${mosquitto_dir}/certs/CA"
mosquitto_dir_server="${mosquitto_dir}/certs/server"
mosquitto_dir_csr="${mosquitto_dir}/certs/csr_files"
ssl_ca_crt="${mosquitto_dir_ca}/ca_crt.${output_format}"
ssl_ca_key="${mosquitto_dir_ca}/ca_key.${output_format}"

# NOTE: If you need to create one or more client Keys and Certs in either PEM or DER format,
# you can call the 'client_maker' script one or more times at the bottom of this script, so
# just scroll right to the end to add the details. You can call 'client_maker' independantly
# whenever you need more clients.

#############################################################
#                   Check passed option values sane         #
#############################################################
echo "Checking if CA dir exists: $mosquitto_dir_ca ..."
if [ ! -d $mosquitto_dir_ca ];then
    echo "Certificate authority folder does not exist, exiting"
    exit 1
fi

# Check CA key and cert exist:
echo "Checking CA key and cert exist: ..."
if [ ! -f ${ssl_ca_crt} ]; then # I: Double quote to prevent globbing and word splitting.
    echo "CA certificate does not exist, exiting!"
    exit 1
fi
if [ ! -f "${mosquitto_dir_ca}/ca_key.pem" ] && [ ! -f "${mosquitto_dir_ca}/ca_key.der" ]; then
    echo "CA key does not exist, exiting!"
    exit 1
fi
# Check CA certificate is still valid:
# Date format we get from openssl:
#  Nov 18 13:47:56 2034 GMT
#  %b %d  %H:%M:%S %Y %Z
#  compare dates from the CA cert and current one:
echo "Checking CA certificate valid ..."
cert_valid_until=$(openssl x509 -enddate -noout -in "${ssl_ca_crt}" | cut -d'=' -f2)
echo "CA certificate valid until: ${cert_valid_until}"
if [ ! $(($(date -d "$cert_valid_until" +"%s") > $(date +"%s"))) ];then
    echo "CA certificate expired, exiting!"
    exit 1
fi
# Check key type:
if [ "$key_type" != 'EC' ] && [ "$key_type" != 'RSA' ] && [ "$key_type" != 'EC25519' ]; then
    echo "Wrong key type specified: '$key_type'"
    echo "Valid keys: [ EC | RSA | EC25519 ]"
    usage
    exit 1;
fi

# Check curve:
if [ "$curve" != 'P-256' ] && [ "$curve" != 'P-384' ] && [ "$curve" != 'P-521' ]; then
    echo "Wrong NIST curve specified: '$curve'"
    echo "Curve must be one of: [ P-256 | P-384 | P-521 ]"
    usage
    exit 1;
fi

# Check RSA bits:
if [ "$rsa_bits" != '2048' ] && [ "$rsa_bits" != '4096' ]; then
    echo "Wrong RSA bits specified: '$rsa_bits'"
    echo "Must be one of: [ 2048 | 4096 ]"
    usage
    exit 1;
fi

# Check days parameter is a number:
if [ -n "$certs_valid_for" ] && [ "$certs_valid_for" -eq "$certs_valid_for" ] 2>/dev/null; then
  echo "Certificate will be valid for: '$certs_valid_for' days"
else
  echo "Not a number: $certs_valid_for"
  usage
  exit 1;
fi

# Check output format:
if [ ${output_format} == 'PEM' ] || [ ${output_format} == 'pem' ]; then # I: Double quote to prevent globbing and word splitting.
  output_format="pem"
elif [ $output_format == 'DER' ] || [ $output_format == 'der' ]; then # I: Double quote to prevent globbing and word splitting.
  output_format="der"
else echo "Incorrect certificate format type specified: '$output_format'";
    usage
    exit 1;
fi


############################################################
#   End of user defined variables
############################################################


# Set the algorithm
algorithm="-algorithm ${key_type}"

# Set the specific pkeyopt for the chosen algorithm (BLANK for ED25519)
if [ "${key_type}" == "EC" ]; then
  echo 'Creating EC Key ...'
  pkeyopt="-pkeyopt ec_paramgen_curve:${curve}"
elif [ "${key_type}" == "RSA" ]; then
  echo 'Creating RSA Key ...'
  pkeyopt="-pkeyopt rsa_keygen_bits:${rsa_bits}"
elif [ "${key_type}" == "ED25519" ]; then
  echo 'Creating ED25519 Key'
  pkeyopt=""
else
  echo 'Key Type not found!'
  exit 1
fi

############################################################
#   Backup existing certs and create dir structure
############################################################

# if certs dir already exists, rename it so we don't overwrite anything important
# but if it doesn't, then redirect the 'No such file or directory' error to null
time_stamp=$(date +"%Y-%m-%d_%H-%M")
if [ ! -d "${mosquitto_dir_ca}" ]; then
    mkdir -p "${mosquitto_dir_ca}-${time_stamp}" 2>/dev/null
else
    cp "${mosquitto_dir_ca}" "${mosquitto_dir_ca}-${time_stamp}" 2>/dev/null
fi

if [ ! -d "${mosquitto_dir_server}" ]; then
    mkdir -p "${mosquitto_dir_server}-${time_stamp}" 2>/dev/null
else
    cp "${mosquitto_dir_server}" "${mosquitto_dir_server}-$time_stamp" 2>/dev/null
fi

# create a sensible directory structure to store everything if not exists:
mkdir -p "${mosquitto_dir}"/certs/{DH,CA,server,clients,csr_files}


###########################################################
# dhparamfile Creation
###########################################################

# Output DH parameters for safe prime group ffdhe2048
if [ "$server_only" == "True" ]; then
openssl genpkey \
    -genparam \
    -algorithm DH \
    -pkeyopt group:ffdhe2048 \
    -out "$mosquitto_dir/certs/DH/dhp_ffdhe2048.pem"
fi

###########################################################
# CA Creation
###########################################################

if [ "${server_only}" == 'True' ]; then
openssl genpkey \
    $algorithm $pkeyopt \
    -outform pem \
    -out "$mosquitto_dir_ca/ca_key.pem" "$encryption"
fi


# Self sign the CA cert

if [ "${server_only}" == 'True' ]; then
openssl req \
    -x509 \
    -new \
    -key "$mosquitto_dir_ca/ca_key.pem" \
    -days $ca_valid_for\
    -subj '/CN=MQTT CA' \
    -outform pem \
    -out "$mosquitto_dir_ca/ca_crt.pem"
fi

###########################################################
# Server Creation
###########################################################

# Create the Key
openssl genpkey \
    $algorithm $pkeyopt \
    -outform pem \
    -out "$mosquitto_dir_server/server_key.pem"

# Create the certificate signing request (CSR)
openssl req \
    -new \
    -subj "/CN=MQTT Server" \
    -addext "subjectAltName = ${subjectAltName}" \
    -nodes \
    -key "$mosquitto_dir_server/server_key.pem" \
    -out "$mosquitto_dir_server/server_req.csr"

# Sign and authenticate it with the CA
# We use copy_extensions to include the subjectAltNames from the CSR in the Server Cert
echo "Sign and authenticate CSR with the CA ..."
openssl x509 \
    -req \
    -in "$mosquitto_dir_server/server_req.csr" \
    -copy_extensions copy \
    -CA "${mosquitto_dir_ca}/ca_crt.pem" \
    -CAkey "${mosquitto_dir_ca}/ca_key.pem" \
    -CAcreateserial \
    -days "${certs_valid_for}" \
    -outform pem \
    -out "$mosquitto_dir_server/server_crt.pem"


###########################################################
# Key and Cert Checking
###########################################################

# Examine the key to check that it looks OK
openssl pkey \
    -in "$mosquitto_dir_server/server_key.pem" \
    -text \
    -noout

# Examine the CSR
openssl req \
    -in "$mosquitto_dir_server/server_req.csr" \
    -noout \
    -text

# Validate the CA certificate
openssl x509 \
    -in "$mosquitto_dir_server/server_crt.pem" \
    -text \
    -noout

#clean up after the server cert creation
mv "$mosquitto_dir_server/server_req.csr" "$mosquitto_dir_csr"

###########################################################
# Key Export and Read Permissions fix
###########################################################

#We need to export a copy of our CA Certificate in DER format for micropython.
openssl x509 \
    -in "$mosquitto_dir_ca/ca_crt.pem" \
    -out "$mosquitto_dir_ca/ca_crt.der" \
    -outform "$output_format"

# and save a copy of it somewhere useful
cp \
    "$mosquitto_dir_ca/ca_crt.der" \
    "$mosquitto_dir/certs/clients"

# but pem based clients need the pem version of it too
cp \
   "$mosquitto_dir_ca/ca_crt.pem" \
   "$mosquitto_dir/certs/clients"

# We also need to give read access to server_key.pem so it can be used by Mosquitto
chmod 644 "$mosquitto_dir_server/server_key.pem"


# move the ca_maker script to certs/CA  and remove its execute permissions
# to reduce the probability of running it by accident again
# and overwriting everything in your certs directory
#mv $mosquitto_dir/ca_maker $mosquitto_dir/certs/CA/ca_maker
#chmod -x $mosquitto_dir/certs/CA/ca_maker

# auto run the client_maker pem/der username
# ./client_maker der pico
#client_maker pem user2
#client_maker pem user3
#client_maker der user4