#!/usr/bin/env bash
set -e

usage() {
    echo "usage: $0 [--force] [--exists-ok] EXTERNAL_HOST" >&2
    exit 1
}

args="$(getopt -o '' --long help,force,exists-ok -- "$@")"
eval "set -- $args"
while true; do
    case "$1" in
        --help) usage;;
        --force) FORCE=1; shift;;
        --exists-ok) EXISTS_OK=1; shift;;
        --) shift; break;;
        *) usage;;
    esac
done
EXTERNAL_HOST="$1"

if [ -z "$EXTERNAL_HOST" ]; then
    usage
fi

if [ "$EUID" -ne 0 ]; then
    echo "error: this script must be run as root" >&2
    exit 1
fi

set -x

is_redhat=false
if [ -e /etc/redhat-release ]; then
    is_redhat=true
    SSLDIR=/etc/pki/tls
else
    SSLDIR=/etc/ssl
fi
KEYFILE=$SSLDIR/private/zulip.key
CERTFILE=$SSLDIR/certs/zulip.combined-chain.crt

if [ -n "$EXISTS_OK" ] && [ -e "$KEYFILE" ] && [ -e "$CERTFILE" ]; then
    exit 0
fi

if [ -z "$FORCE" ] && { [ -e "$KEYFILE" ] || [ -e "$CERTFILE" ]; }; then
    echo "$0: certificate and/or key already exists; use --force to overwrite." >&2
    exit 1
fi
rm -f "$KEYFILE" "$CERTFILE"

if [[ "$EXTERNAL_HOST" =~ ^(([0-9]+\.){3}[0-9]+)(:[0-9]+)?$ ]]; then
    subjectAltName="IP:${BASH_REMATCH[1]}"  # IPv4 address
elif [[ "$EXTERNAL_HOST" =~ ^\[([^][]*)\](:[0-9]+)?$ ]]; then
    subjectAltName="IP:${BASH_REMATCH[1]}"  # IPv6 address
elif [[ "$EXTERNAL_HOST" =~ ^([^:]+)(:[0-9]+)?$ ]]; then
    subjectAltName="DNS:${BASH_REMATCH[1]}"
else
    echo "$0: invalid host $EXTERNAL_HOST" >&2
    exit 1
fi

config="$(mktemp)" || exit 1
trap 'rm -f "$config"' EXIT

cat >"$config" <<EOF
# Based on /usr/share/ssl-cert/ssleay.cnf from Debian's \`ssl-cert\`
# package, which is used for the system's snakeoil cert in /etc/ssl/.

RANDFILE            = /dev/urandom

[ req ]
default_bits        = 2048
distinguished_name  = req_distinguished_name
prompt              = no
policy              = policy_anything
req_extensions      = v3_req
x509_extensions     = v3_req

[ req_distinguished_name ]
commonName          = $EXTERNAL_HOST

[ v3_req ]
basicConstraints    = CA:FALSE
subjectAltName      = $subjectAltName
EOF

if [ "$is_redhat" = true ]; then
    yum install -y openssl
else
    apt-get install -y openssl
fi

# Based on /usr/sbin/make-ssl-cert from Debian's `ssl-cert` package.
openssl req -new -x509 \
        -config "$config" -days 3650 -nodes -sha256 \
        -out "$CERTFILE" -keyout "$KEYFILE"

chmod 644 "$CERTFILE"
chmod 640 "$KEYFILE"