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|
#!/usr/bin/perl -T
#----------------------------------------------------------------------
# ACME client written with process isolation and minimal privileges in mind
# Copyright © 2015,2016 Guilhem Moulin <guilhem@fripost.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#----------------------------------------------------------------------
use strict;
use warnings;
# Usage: client COMMAND CONFIG_FD SOCKET_FD [ARGUMENTS]
#
# fdopen(3) the file descriptor SOCKET_FD (corresponding to the
# listening lacme-accountd socket), connect(2) to it to retrieve the
# account key's public parameters and later send data to be signed by
# the master component (using the account key).
#
# CONFIG_FD is a read-only file descriptor associated with the
# configuration file at pos 0. (This is needed since this process
# doesn't know its name and might not have read access to it.)
#
# NOTE: one needs to chdir(2) to an appropriate ACME challenge directory
# before running this program, since challenge tokens are (on purpose)
# only written to the current directory. If COMMAND is challenge-less,
# one should chdir(2) to the root directory "/" instead.
#
# NOTE: one should run this program as an unprivileged user:group such
# as "nobody:nogroup"; bind(2)'ing to a restricted UNIX socket (for
# instance own by another user and created with umask 0177) is not a
# problem since SOCKET_FD can be bound as root prior to the execve(2).
my $PROTOCOL_VERSION = 1;
use Errno 'EEXIST';
use Fcntl qw/O_CREAT O_EXCL O_WRONLY/;
use Digest::SHA qw/sha256 sha256_hex/;
use MIME::Base64 qw/encode_base64 encode_base64url/;
use LWP::UserAgent ();
use JSON ();
use Config::Tiny ();
# Clean up PATH
$ENV{PATH} = join ':', qw{/usr/bin /bin};
delete @ENV{qw/IFS CDPATH ENV BASH_ENV/};
my $COMMAND = shift @ARGV // die;
# Untaint and fdopen(3) the configuration file and listening socket
(shift @ARGV // die) =~ /\A(\d+)\z/ or die;
open my $CONFFILE, '<&=', $1 or die "fdopen $1: $!";
(shift @ARGV // die) =~ /\A(\d+)\z/ or die;
open my $S, '+<&=', $1 or die "fdopen $1: $!";
#############################################################################
# Read the protocol version and JSON Web Key (RFC 7517) from the
# lacme-accountd socket
#
die "Error: Invalid client version\n" unless
$S->getline() =~ /\A(\d+) OK(?:.*)\r\n\z/ and $1 == $PROTOCOL_VERSION;
my $JWK = JSON::->new->decode($S->getline());
# JSON keys need to be sorted lexicographically (for instance in the thumbprint)
sub json() { JSON::->new->utf8->canonical(); }
my $JWK_thumbprint = encode_base64url(sha256(json()->encode($JWK)));
my $NONCE;
#############################################################################
# Parse configuration (already validated by the master) and create the
# LWP::UserAgent object
#
my $CONFIG = do {
my $conf = do { local $/ = undef; <$CONFFILE> };
close $CONFFILE or die "Can't close: $!";
my $h = Config::Tiny::->read_string($conf) or die Config::Tiny::->errstr()."\n";
$h->{_} //= {};
$h->{client}->{$_} //= $h->{_}->{$_} foreach keys %{$h->{_}}; # add defaults
$h->{client};
};
my $UA = do {
my %args = %$CONFIG;
my $verify = lc (delete $args{SSL_verify} // 'Yes') eq 'no' ? 0 : 1;
my %ssl_opts = ( verify_hostname => $verify );
$ssl_opts{$_} = $args{$_} foreach grep /^SSL_/, keys %args;
LWP::UserAgent::->new( ssl_opts => \%ssl_opts );
} // die "Can't create LWP::UserAgent object";
#############################################################################
# Send an HTTP request to the ACME server. If $json is defined, send
# its encoding as the request content, with "application/json" as
# Content-Type.
#
sub request($$;$) {
my ($method, $uri, $json) = @_;
print STDERR "[$$] >>> $method $uri <<<\n" if $ENV{DEBUG};
my $req = HTTP::Request::->new($method => $uri) or die "Can't $method $uri";
if (defined $json) {
$req->content_type('application/json');
$req->content(json()->encode($json));
}
my $r = $UA->request($req) or die "Can't $method $uri";
$NONCE = $r->header('Replay-Nonce'); # undef $NONCE if the header is missing
print STDERR "[$$] >>> ", $r->status_line, "\n", $r->headers->as_string, "\n" if $ENV{DEBUG};
return $r;
}
# List all 'Links' headers with the relationship $rel (RFC 5988)
sub request_link_rel($$) {
my ($r, $rel) = @_;
grep defined, map
{ /\A<([^>]+)>.*;\s*rel=([^;]+)/
; my ($link, $rels) = ($1, $2 // '')
; (grep { $rel eq $_ } map { /^"(.*)"/ ? $1 : $_ } split(/\s+/, $rels)) ? $link : undef
}
$r->header('Link');
}
# The request's Status Line; if the Content-Type is
# application/problem+json, parse the decoded content as JSON and add
# the value of the 'detail' field to the Status Line.
# https://tools.ietf.org/html/draft-ietf-appsawg-http-problem
sub request_status_line($) {
my $r = shift;
my $msg = $r->status_line;
if ($r->content_type() eq 'application/problem+json') {
my $content = json()->decode($r->decoded_content());
print STDERR json()->pretty->encode($content), "\n" if $ENV{DEBUG};
$msg .= " (".$content->{detail}.")" if defined $content->{detail};
}
return $msg;
}
# Parse and return the request's decoded content as JSON; or print the
# Status Line and fail if the request failed.
# If $dump is set, also pretty-print the decoded content.
sub request_json_decode($;$) {
my $r = shift;
my $dump = shift || $ENV{DEBUG};
die request_status_line($r), "\n" unless $r->is_success();
my $content = $r->decoded_content();
die "Content-Type: ".$r->content_type()." is not application/json\n"
unless $r->content_type() eq 'application/json';
$content = json()->decode($content);
print STDERR json()->pretty->encode($content), "\n" if $dump;
return $content;
}
#############################################################################
# JSON-encode the hash reference $h and send it to the ACME server $uri
# encapsulated it in a JSON Web Signature (JWS).
# https://tools.ietf.org/html/draft-ietf-acme-acme
#
sub acme($$) {
my ($uri, $h) = @_;
# the ACME server MUST provide a Replay-Nonce header field in
# response to a HEAD request for any valid resource
request(HEAD => $uri) unless defined $NONCE;
# Produce the JSON Web Signature: RFC 7515 section 5
my $payload = encode_base64url(json()->encode($h));
my %header = ( alg => 'RS256', jwk => $JWK );
my $protected = encode_base64url(json()->encode({ %header, nonce => $NONCE }));
my $data = $protected .'.'. $payload;
$S->printflush($data, "\r\n");
my $sig = $S->getline();
$sig =~ s/\r\n\z// or die;
# Flattened JSON Serialization, RFC 7515 section 7.2.2
request(POST => $uri, {
payload => $payload,
protected => $protected,
header => \%header,
signature => $sig
});
}
my $SERVER_URI = $CONFIG->{server} // 'https://acme-v01.api.letsencrypt.org/';
$SERVER_URI .= '/' unless substr($SERVER_URI, -1, 1) eq '/';
my %RES;
# Get the resource URI from the directory
sub acme_resource($%) {
my $r = shift;
# Query the root ACME directory to initialize the nonce and get the resources URIs
%RES = %{ request_json_decode(request(GET => $SERVER_URI.'directory')) } unless %RES;
my $uri = $RES{$r} // die "Missing ressource for \"$r\"\n";
acme($uri, {resource => $r, @_});
}
#############################################################################
# new-reg AGREEMENT_URI [CONTACT ..]
#
if ($COMMAND eq 'new-reg') {
my $agreement = shift @ARGV;
print STDERR "Requesting new registration ".(@ARGV ? ("for ".join(', ', @ARGV)) : "")."\n";
my %h = (contact => \@ARGV);
$h{agreement} = $agreement if $agreement ne '';
my $r = acme_resource('new-reg', %h);
my ($terms) = request_link_rel($r, 'terms-of-service');
request_json_decode($r,1) if $r->is_success() and $ENV{DEBUG}; # pretty-print the JSON
print STDERR request_status_line($r), "\n";
print STDERR "Subscriber Agreement URI: $terms\n" if defined $terms;
print STDERR "Registration URI: ", $r->header('Location'), "\n";
exit ($r->is_success() ? 0 : 1);
}
#############################################################################
# reg=URI AGREEMENT_URI [CONTACT ..]
#
elsif ($COMMAND =~ /\Areg=(\p{Print}+)\Z/) {
die "Empty registration URI (use the 'new-reg' command to determine the URI)\n" if $1 eq '';
my $uri = $SERVER_URI.$1;
my $agreement = shift @ARGV;
my %h = (resource => 'reg');
$h{agreement} = $agreement if $agreement ne '';
$h{contact} = \@ARGV if @ARGV; # don't empty the contact list
my $r = acme($uri, \%h);
my ($terms) = request_link_rel($r, 'terms-of-service');
$r->is_success() ? request_json_decode($r,1) # pretty-print the JSON
: print STDERR request_status_line($r), "\n";
print STDERR "Subscriber Agreement URI: $terms\n" if defined $terms;
exit ($r->is_success() ? 0 : 1);
}
#############################################################################
# new-cert AUTHZ [AUTHZ ..]
# Read the CSR (in DER format) from STDIN, print the cert (in PEM format
# to STDOUT)
#
elsif ($COMMAND eq 'new-cert') {
die unless @ARGV;
my $timeout = $CONFIG->{timeout} // 10;
foreach my $domain (@ARGV) {
print STDERR "Processing new DNS authz for $domain\n" if $ENV{DEBUG};
my $r = acme_resource('new-authz', identifier => {type => 'dns', value => $domain});
my ($challenge) = grep {$_->{type} eq 'http-01'}
@{request_json_decode($r)->{challenges} // []};
die "Missing 'http-01' challenge in server response" unless defined $challenge;
die "Invalid challenge token ".($challenge->{token} // '')."\n"
# ensure we don't write outside the cwd
unless ($challenge->{token} // '') =~ /\A[A-Za-z0-9_\-]+\z/;
my $keyAuthorization = $challenge->{token}.'.'.$JWK_thumbprint;
# serve $keyAuthorization at http://$domain/.well-known/acme-challenge/$challenge->{token}
if (sysopen(my $fh, $challenge->{token}, O_CREAT|O_EXCL|O_WRONLY, 0644)) {
$fh->print($keyAuthorization);
$fh->close() or die "Can't close: $!";
} elsif ($! == EEXIST) {
print STDERR "WARNING: File exists: $challenge->{token}\n";
} else {
die "Can't open $challenge->{token}: $!";
}
$r = acme($challenge->{uri}, {
resource => 'challenge',
keyAuthorization => $keyAuthorization
});
# wait until the status become 'valid'
for ( my $i = 0, my $content, my $status;
$content = request_json_decode($r),
$status = $content->{status} // 'pending',
$status ne 'valid';
$r = request('GET' => $challenge->{uri})) {
if (defined (my $problem = $content->{error})) { # problem document (RFC 7807)
my $msg = $problem->{status};
$msg .= " " .$problem->{title} if defined $problem->{title};
$msg .= " (".$problem->{detail}.")" if defined $problem->{detail};
die $msg, "\n";
}
die "Error: Invalid challenge for $domain (status: ".$status.")\n" if $status ne 'pending';
my $sleep = 1;
if (defined (my $retry_after = $r->header('Retry-After'))) {
print STDERR "Retrying after $retry_after seconds...\n";
$sleep = $retry_after;
}
$i += $sleep;
die "Timeout exceeded while waiting for challenge to pass ($domain)\n" if $timeout > 0 and $i >= $timeout;
sleep $sleep;
}
}
my $csr = do { local $/ = undef; <STDIN> };
my $r = acme_resource('new-cert', csr => encode_base64url($csr));
die request_status_line($r), "\n" unless $r->is_success();
my $uri = $r->header('Location');
# https://acme-v01.api.letsencrypt.org/acme/cert/$serial
print STDERR "Certificate URI: $uri\n";
if ($r->decoded_content() eq '') { # wait for the cert
for (my $i = 0;;) {
$r = request('GET' => $uri);
die request_status_line($r), "\n" unless $r->is_success();
last unless $r->code == 202; # Accepted
my $retry_after = $r->header('Retry-After') // 1;
print STDERR "Retrying after $retry_after seconds...\n";
$i += $retry_after;
die "Timeout exceeded while waiting for certificate\n" if $timeout > 0 and $i >= $timeout;
sleep $retry_after;
}
}
my $der = $r->decoded_content();
# conversion DER -> PEM
pipe my $rd, my $wd or die "Can't pipe: $!";
my $pid = fork // die "Can't fork: $!";
unless ($pid) {
open STDIN, '<&', $rd or die "Can't dup: $!";
exec qw/openssl x509 -inform DER -outform PEM/ or die;
}
$rd->close() or die "Can't close: $!";
$wd->print($der);
$wd->close() or die "Can't close: $!";
waitpid $pid => 0;
die $? if $? > 0;
}
#############################################################################
# revoke-cert
# The certificate to revoke is passed (in DER format) to STDIN; this
# is required since the ACME client might not have read access to the
# X.509 file
#
elsif ($COMMAND eq 'revoke-cert') {
die if @ARGV;
my $der = do { local $/ = undef; <STDIN> };
close STDIN or die "Can't close: $!";
my $r = acme_resource('revoke-cert', certificate => encode_base64url($der));
exit 0 if $r->is_success();
die request_status_line($r), "\n";
}
|