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#!/usr/bin/env perl
# This is a simplified rewrite of acme-tiny in Perl, since Python 3 is 125 MiB
# but Perl is everywhere and JSON::PP mostly in default installations.
# Depends on curl and openssl.
#
# TODO: eventually the ACME protocol will stabilize:
# https://github.com/ietf-wg-acme/acme/blob/master/draft-ietf-acme-acme.md
use strict;
use warnings;
use MIME::Base64 qw(encode_base64 encode_base64url);
use JSON::PP;
use Digest::SHA qw(sha256);
use IPC::Open2;
# https://acme-staging.api.letsencrypt.org
# https://acme-v01.api.letsencrypt.org
my $ca = $ENV{ACME_CA} || die 'ACME_CA not set';
my $account_key = $ENV{ACCOUNT_KEY} || die 'ACCOUNT_KEY not set';
my $csr_file = shift || die 'no file was given';
my $acme_dir = $ENV{ACME_DIR} || die 'ACME_DIR not set';
# Prepare some values derived from account key for the ACME protocol
sub b64 { encode_base64url(shift, '') =~ s/=//gr }
my $key_info = `openssl rsa -in '$account_key' -noout -text`;
die 'cannot process account key' if $?;
my ($pub_hex, $pub_exp) =
$key_info =~ /modulus:\n\s+00:([a-f\d:\s]+?)\npublicExponent: (\d+)/m;
$pub_exp = sprintf("%x", $pub_exp);
$pub_exp = "0$pub_exp" if length($pub_exp) % 2;
my $header = { alg => 'RS256', jwk => { kty => 'RSA',
e => b64(pack 'H*', $pub_exp),
n => b64(pack 'H*', $pub_hex =~ s/\s|://gr)
}};
my $json = JSON::PP->new->pretty(0)->canonical(1);
my $thumbprint = b64(sha256($json->encode($header->{jwk})));
# Pipe data through an external program, keeping status in $?
sub communicate {
my $data = pop;
my $pid = open2(\*Reader, \*Writer, @_);
print Writer $data if defined($data);
close Writer;
local $/ = undef;
my $resp = <Reader>;
waitpid $pid, 0;
return $resp;
}
# Use cURL to download a file over HTTPS but parse it ourselves (quite silly)
sub get {
my ($url, $data) = @_;
my @args = ('curl', '-sS', '-D-', '-H', 'Expect:');
push @args, ('-X', 'POST', '--data-binary', '@-') if defined($data);
my $resp = communicate(@args, $url, $data);
die 'cannot download' if $? >> 8;
my ($code, $headers, $body) =
$resp =~ m#\AHTTP/\d(?:\.\d)? (\d+) .*?\r\n(.*?)\r\n\r\n(.*)#sm;
return ($code, $body, { $headers =~ /(\S+?): (.*)\r\n/mg })
}
# Make a signed request to an ACME endpoint
sub send_signed {
my ($url, $payload) = @_;
my $protected = { nonce => `curl -sSfI '$ca/directory'`
=~ /Replay-Nonce: (\S+)/i, %$header };
die 'cannot retrieve nonce' if $?;
my $b64payload = b64 $json->encode($payload);
my $b64protected = b64 $json->encode($protected);
my $out = communicate('openssl', 'dgst', '-sha256', '-sign',
$account_key, "$b64protected.$b64payload");
die 'cannot sign request' if $? >> 8;
return get $url, $json->encode({
header => $header, protected => $b64protected,
payload => $b64payload, signature => b64 $out
})
}
# Find all domains specified in the certificate request
my $csr = `openssl req -in '$csr_file' -noout -text`;
die 'cannot parse CSR' if $?;
my @domains;
push @domains, $1 if $csr =~ /Subject:.*? CN *= *([^\s,;\/]+)/;
# FIXME: this may not parse correctly anymore, try it out
push @domains, map { substr $_, 4 } grep { /^DNS:/ } split(/, /)
for $csr =~ /X509v3 Subject Alternative Name: \n +([^\n]+)\n/g;
# Get certificate domains and expiration
my ($code, $result, $headers) = get "$ca/terms";
($code, $result) = send_signed("$ca/acme/new-reg", {
resource => 'new-reg',
agreement => ($code == 302 && exists $headers->{Location})
? $headers->{Location}
: 'https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf'
});
die "cannot register: $code\n$result" if $code != 201 && $code != 409;
# Check if the file is really there, submit an HTTP challenge and wait
sub verify_http {
my ($checked_url, $key_auth, $challenge_uri) = @_;
my ($code, $result) = get $checked_url;
die "checking $checked_url failed: $code" if $code != 200;
die 'challenge contents differ' if $result ne $key_auth;
($code, $result) = send_signed($challenge_uri, {
resource => 'challenge', keyAuthorization => $key_auth
});
die "challenge submission failed: $code\n$result" if $code != 202;
while (1) {
($code, $result) = get $challenge_uri;
die "challenge verification failed: $code\n$result" if $code >= 400;
my $status = $json->decode($result);
if ($status->{status} eq 'valid') {
last;
} elsif ($status->{status} eq 'pending') {
sleep 1;
} else {
die "challenge verification failed: $result";
}
}
}
for my $domain (@domains) {
my ($code, $result) = send_signed("$ca/acme/new-authz", {
resource => 'new-authz',
identifier => { type => 'dns', value => $domain }
});
die "cannot request challenge: $code\n$result" if $code != 201;
my ($challenge) = grep { $_->{type} eq 'http-01' }
@{$json->decode($result)->{challenges}};
my $token = $challenge->{token} =~ s/[^A-Za-z0-9_-]/_/gr;
my $key_auth = "$token.$thumbprint";
my $known_path = "$acme_dir/$token";
open(my $fh, '>', $known_path) or die "cannot write to $known_path: $!";
print $fh $key_auth;
close $fh;
eval { verify_http("http://$domain/.well-known/acme-challenge/$token",
$key_auth, $challenge->{uri}) };
unlink $known_path;
die "$domain: $@" if $@;
}
# Get the new certificate and convert it to the PEM format
my $der = `openssl req -in '$csr_file' -outform DER`;
die 'cannot convert CSR' if $?;
($code, $result) = send_signed("$ca/acme/new-cert", {
resource => 'new-cert', csr => b64 $der
});
die "cannot sign certificate: $code\n$result" if $code != 201;
my $pem = join("\n", unpack '(A64)*', encode_base64($result, ''));
print "-----BEGIN CERTIFICATE-----\n$pem\n-----END CERTIFICATE-----\n";