#!/usr/bin/perl -w

# ssh://git.mdcc.cx/git/ad1810-stuff.git git/ad1810-stuff/scripts

# june 2025

# based upon
# https://github.com/dehydrated-io/dehydrated/wiki/Import-from-official-letsencrypt-client

# Depends: libcrypt-openssl-rsa-perl, libfile-slurper-perl

# Import account key
#
# If for any reason you want to import your existing account key from the
# official letsencrypt client place this perl script next to private_key.json
# (should be in a subdirectory under
# /etc/letsencrypt/accounts/acme-v01.api.letsencrypt.org/directory) and run it.
# It should return your private key in PEM format, which you can pipe directly
# into private_key.pem.

use strict;

use Crypt::OpenSSL::RSA;
use Crypt::OpenSSL::Bignum;
use JSON;
use File::Slurper 'read_text';
use MIME::Base64;

my $json_file = "private_key.json";
my $json_content = read_text($json_file);
$json_content =~ tr/-/+/;
$json_content =~ tr/_/\//;

my $json = decode_json($json_content);

my $n = Crypt::OpenSSL::Bignum->new_from_bin(decode_base64($json->{n}));
my $e = Crypt::OpenSSL::Bignum->new_from_bin(decode_base64($json->{e}));
my $d = Crypt::OpenSSL::Bignum->new_from_bin(decode_base64($json->{d}));
my $p = Crypt::OpenSSL::Bignum->new_from_bin(decode_base64($json->{p}));
my $q = Crypt::OpenSSL::Bignum->new_from_bin(decode_base64($json->{q}));

my $rsa = Crypt::OpenSSL::RSA->new_key_from_parameters($n, $e, $d, $p, $q);

print($rsa->get_private_key_string());