path: root/letsencrypt

#!/usr/bin/perl -T

#----------------------------------------------------------------------
# Let's Encrypt ACME client
# Copyright © 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;

our $VERSION = '0.0.1';
my $NAME = 'letsencrypt';

use Errno qw/EADDRINUSE EINTR/;
use Fcntl qw/F_GETFD F_SETFD FD_CLOEXEC SEEK_SET/;
use File::Temp ();
use Getopt::Long qw/:config posix_default no_ignore_case gnu_getopt auto_version/;
use List::Util 'first';
use POSIX ();
use Socket qw/PF_INET PF_INET6 PF_UNIX INADDR_ANY IN6ADDR_ANY
              SOCK_STREAM SOL_SOCKET SO_REUSEADDR SHUT_RDWR/;

use Config::Tiny ();
use Net::SSLeay ();

# Clean up PATH
$ENV{PATH} = join ':', qw{/usr/bin /bin};
delete @ENV{qw/IFS CDPATH ENV BASH_ENV/};

my ($COMMAND, %OPTS, $CONFFILE, $CONFIG, @CLEANUP);
$SIG{$_} = sub() { exit 1 } foreach qw/INT TERM/; # run the END block upon SIGINT/SIGTERM


#############################################################################
# Parse and validate configuration
#
sub usage(;$$) {
    my $rv = shift // 0;
    if ($rv) {
        my $msg = shift;
        print STDERR $msg."\n" if defined $msg;
        print STDERR "Try '$NAME --help' or consult the manpage for more information.\n";
    }
    else {
        print STDERR "Usage: $NAME [--config=FILE] [--socket=PATH] [OPTIONS] COMMAND [ARGUMENT ..]\n"
                    ."Consult the manpage for more information.\n";
    }
    exit $rv;
}
usage(1) unless GetOptions(\%OPTS, qw/config=s config-certs=s socket=s agreement-uri=s debug help|h/);
usage(0) if $OPTS{help};

$COMMAND = shift(@ARGV) // usage(1, "Missing command");
$COMMAND = $COMMAND =~ /\A(new-reg|reg=\p{Print}*|new-cert|revoke-cert)\z/ ? $1
         : usage(1, "Invalid command: $COMMAND"); # validate and untaint $COMMAND
@ARGV = map { /\A(\p{Print}*)\z/ ? $1 : die } @ARGV; # untaint @ARGV

do {
    my $conffile = $OPTS{config} // first { -f $_ }
        ( "./$NAME.conf"
        , ($ENV{XDG_CONFIG_HOME} // "$ENV{HOME}/.config")."/letsencrypt-tiny/$NAME.conf"
        , "/etc/letsencrypt-tiny/$NAME.conf"
        );
    die "Error: Can't find configuration file\n" unless defined $conffile;
    print STDERR "Using configuration file: $conffile\n" if $OPTS{debug};
    open $CONFFILE, '<', $conffile or die "Can't open $conffile: $!\n";
    my $conf = do { local $/ = undef, <$CONFFILE> };
    # don't close $CONFFILE so we can pass it to the client

    my $h = Config::Tiny::->read_string($conf) or die Config::Tiny::->errstr()."\n";
    my $defaults = delete $h->{_} // {};
    my %valid = (
        client => {
            socket  => (defined $ENV{XDG_RUNTIME_DIR} ? "$ENV{XDG_RUNTIME_DIR}/S.letsencrypt" : undef),
            user    => 'nobody',
            group   => 'nogroup',
            command => '/usr/lib/letsencrypt-tiny/client',
            # the rest is for the ACME client
            map {$_ => undef} qw/server timeout SSL_verify SSL_version SSL_cipher_list/
        },
        webserver => {
            listen                => ':80',
            'challenge-directory' => '/var/www/acme-challenge',
            user                  => 'www-data',
            group                 => 'www-data',
            command               => '/usr/lib/letsencrypt-tiny/webserver',
            iptables              => 'Yes'

        }
    );
    foreach my $s (keys %valid) {
        my $h = delete $h->{$s} // {};
        my %v = map { $_ => delete $h->{$_} // $valid{$s}->{$_} } keys %{$valid{$s}};
        die "Unknown option(s) in [$s]: ".join(', ', keys %$h)."\n" if %$h;
        $h->{$_} //= $defaults->{$_} foreach keys %$defaults;
        $CONFIG->{$s} = \%v;
    }
    die "Invalid section(s): ".join(', ', keys %$h)."\n" if %$h;
    $CONFIG->{_} = $defaults;
};

# Regular expressions for domain validation
my $RE_LABEL  = qr/[0-9a-z](?:[0-9a-z\x2D]{0,61}[0-9a-z])?/aai;
my $RE_DOMAIN = qr/$RE_LABEL(?:\.$RE_LABEL)+/;


#############################################################################
# Generate a Certificate Signing Request (in DER format)
#
sub gen_csr(%) {
    my %args = @_;
    return unless defined $args{'certificate-key'} and defined $args{subject};
    return if defined $args{hash} and !grep { $args{hash} eq $_ } qw/md5 rmd160 sha1 sha224 sha256 sha384 sha512/;

    my $config = File::Temp::->new(SUFFIX => '.conf', TMPDIR => 1) // die;
    $config->print(
        "[ req ]\n",
        "distinguished_name = req_distinguished_name\n",
        "req_extensions     = v3_req\n",

        "[ req_distinguished_name ]\n",

        "[ v3_req ]\n",
        # XXX Golang errors on extensions marked critical
        # https://github.com/letsencrypt/boulder/issues/565
        #"basicConstraints     = critical, CA:FALSE\n",
        "basicConstraints     = CA:FALSE\n",
        "subjectKeyIdentifier = hash\n"
    );
    #$config->print("keyUsage = critical, $args{keyUsage}\n")   if defined $args{keyUsage};
    $config->print("keyUsage = $args{keyUsage}\n")             if defined $args{keyUsage};
    $config->print("subjectAltName = $args{subjectAltName}\n") if defined $args{subjectAltName};
    $config->close() or die "Can't close: $!";

    my @args = (qw/-new -batch -key/, $args{'certificate-key'});
    push @args, "-$args{hash}" if defined $args{hash};
    push @args, '-subj', $args{subject}, '-config', $config->filename(), qw/-reqexts v3_req/;

    open my $fh, '-|', qw/openssl req -outform DER/, @args or die "fork: $!";
    my $csr = do { local $/ = undef; <$fh> };
    close $fh or $! ? die "Can't close: $!" : return;

    if ($OPTS{debug}) {
        # print out the CSR in text form
        pipe my $rd, my $wd or die "pipe: $!";
        my $pid = fork // die "fork: $!";
        unless ($pid) {
            open STDIN,  '<&', $rd      or die "Can't dup: $!";
            open STDOUT, '>&', \*STDERR or die "Can't dup: $!";
            exec qw/openssl req -noout -text -inform DER/ or die;
        }
        $rd->close() or die "Can't close: $!";
        $wd->print($csr);
        $wd->close() or die "Can't close: $!";

        waitpid $pid => 0;
        die $? if $? > 0;
    }

    return $csr;
}


#############################################################################
# Get the timestamp of the given cert's expiration date.
# Internally the expiration date is stored as a RFC3339 string (such as
# yyyy-mm-ddThh:mm:ssZ); we convert it to a timestamp manually.
#
sub x509_enddate($) {
    my $filename = shift;
    my ($bio, $x509, $time, $dt);

    $bio  = Net::SSLeay::BIO_new_file($filename, 'r');
    $x509 = Net::SSLeay::PEM_read_bio_X509($bio)        if defined $bio;
    $time = Net::SSLeay::X509_get_notAfter($x509)       if defined $x509;
    $dt   = Net::SSLeay::P_ASN1_TIME_get_isotime($time) if defined $time;

    my $t;
    if (defined $dt and $dt =~ s/\A(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})//) {
        # RFC3339 datetime strings; assume epoch is on January 1 of $epoch_year
        my ($y, $m, $d, $h, $min, $s) = ($1, $2, $3, $4, $5, $6);
        my (undef,undef,undef,undef,undef,$epoch_year,undef,undef,undef) = gmtime(0);
        $t = 0;
        foreach (($epoch_year+1900) .. $y-1) {
            $t += 365*86400;
            $t += 86400 if ($_ % 4 == 0 and $_ % 100 != 0) or ($_ % 400 == 0); # leap
        }

        if ($m > 1) {
            my @m = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
            $m[1]++ if ($y % 4 == 0 and $y % 100 != 0) or ($y % 400 == 0); # leap
            $t += 86400*$m[$_] for (0 .. $m-2);
        }

        $t += 86400*($d-1);
        $t += $s + 60*($min + 60*$h);

        $dt =~ s/\A\.(\d{1,9})\d*//; # ignore nanosecs

        if ($dt =~ /\A([+-])(\d{2}):(\d{2})\z/) {
            my $tz = 60*($3 + 60*$2);
            $t = $1 eq '-' ? ($t+$tz) : ($t-$tz);
        }
    }

    Net::SSLeay::X509_free($x509) if defined $x509;
    Net::SSLeay::BIO_free($bio)   if defined $bio;
    return $t;
}


#############################################################################
# Drop privileges and chdir afterwards
#
sub drop_privileges($$$) {
    my ($user, $group, $dir) = @_;

    # set effective and real gid; also set the list of supplementary gids to that single gid
    if ($group ne '') {
        my $gid = getgrnam($group) // die "Can't getgrnam($group): $!";
        $) = "$gid $gid";
        die "Can't setgroups: $!" if $@;
        POSIX::setgid($gid) or die "Can't setgid: $!";
        die "Couldn't setgid/setguid" unless $( eq "$gid $gid" and $) eq "$gid $gid"; # safety check
    }

    # set effective and real uid
    if ($user ne '') {
        my $uid = getpwnam($user) // die "Can't getpwnam($user): $!";
        POSIX::setuid($uid) or die "Can't setuid: $!";
        die "Couldn't setuid/seteuid" unless $< == $uid and $> == $uid; # safety check
    }

    chdir $dir or die "Can't chdir to $dir: $!";
}


#############################################################################
# Ensure the FD_CLOEXEC bit is $set on $fd
#
sub set_FD_CLOEXEC($$) {
    my ($fd, $set) = @_;
    my $flags = fcntl($fd, F_GETFD, 0) or die "Can't fcntl F_GETFD: $!";
    my $flags2 = $set ? ($flags | FD_CLOEXEC) : ($flags & ~FD_CLOEXEC);
    return if $flags == $flags2;
    fcntl($fd, F_SETFD, $flags2) or die "Can't fcntl F_SETFD: $!";
}


#############################################################################
# Try to spawn a webserver to serve ACME challenges, and return the
# temporary challenge directory.
# If a webserver is already listening, symlink the 'challenge-directory'
# configuration option to the temporary challenge directory.
# Otherwise, bind(2) a socket, pass its fileno to the webserver
# component, and optionally install iptables rules.
#
sub spawn_webserver() {
    # create a temporary directory; give write access to the ACME client
    # and read access to the webserver
    my $tmpdir = File::Temp::->newdir(CLEANUP => 1, TMPDIR => 1) // die;
    chmod 0755, $tmpdir or die "Can't chmod: $!";
    if ((my $username = $CONFIG->{client}->{user}) ne '') {
        my $uid = getpwnam($username) // die "Can't getgrnam($username): $!";
        chown($uid, -1, $tmpdir) or die "Can't chown: $!";
    }

    my $conf = $CONFIG->{webserver};
    my ($fam, $addr, $port) = (PF_INET, $conf->{listen}, 80);
    $port = $1 if $addr =~ s/:(\d+)$//;
    $addr = Socket::inet_ntop(PF_INET, INADDR_ANY) if $addr eq '';
    $fam = PF_INET6 if $addr =~ s/^\[(.+)\]$/$1/;

    my $proto = getprotobyname("tcp") // die;
    socket(my $srv, $fam, SOCK_STREAM, $proto) or die "socket: $!";
    setsockopt($srv, SOL_SOCKET, SO_REUSEADDR, pack("l", 1)) or die "setsockopt: $!";
    $addr = Socket::inet_pton($fam, $addr) // die "Invalid address $conf->{listen}\n";
    my $sockaddr = $fam == PF_INET  ? Socket::pack_sockaddr_in($port,  $addr)
                 : $fam == PF_INET6 ? Socket::pack_sockaddr_in6($port, $addr)
                 : die;

    # try to bind aginst the specified address:port
    bind($srv, $sockaddr) or do {
        die "Can't bind to $conf->{listen}: $!" if $! != EADDRINUSE;
        print STDERR "[$$] Using existing webserver on $conf->{listen}\n" if $OPTS{debug};
        my $dir = $conf->{'challenge-directory'};
        symlink $tmpdir, $dir or die "Can't symlink $dir -> $tmpdir: $!";
        push @CLEANUP, sub() {
            print STDERR "Unlinking $dir\n" if $OPTS{debug};
            unlink $dir or warn "Warning: Can't unlink $dir: $!";
        };
        return $tmpdir;
    };
    listen($srv, 5) or die "listen: $!";

    # spawn the webserver component
    my $pid = fork() // "fork: $!";
    unless ($pid) {
        drop_privileges($conf->{user}, $conf->{group}, $tmpdir);
        set_FD_CLOEXEC($srv, 0);
        $ENV{DEBUG} = $OPTS{debug};
        # use execve(2) rather than a Perl pseudo-process to ensure that
        # the child doesn't have access to the parent's memory
        exec $conf->{command}, fileno($srv) or die;
    }

    print STDERR "[$$] Forking ACME webserver, child PID $pid\n" if $OPTS{debug};
    set_FD_CLOEXEC($srv, 1);
    push @CLEANUP, sub() {
        print STDERR "[$$] Shutting down ACME webserver\n" if $OPTS{debug};
        shutdown($srv, SHUT_RDWR) or warn "shutdown: $!";
        kill 15 => $pid;
        waitpid $pid => 0;
    };

    return $tmpdir if lc ($conf->{iptables} // 'Yes') eq 'no';

    # install iptables
    my $iptables_bin = $fam == PF_INET ? 'iptables' : $fam == PF_INET6 ? 'ip6tables' : die;
    my $iptables_tmp = File::Temp::->new(TMPDIR => 1) // die;
    set_FD_CLOEXEC($iptables_tmp, 1);

    my $pid2 = fork() // die "fork: $!";
    unless ($pid2) {
        open STDIN,  '<',  '/dev/null'   or die "Can't open /dev/null: $!";
        open STDOUT, '>&', $iptables_tmp or die "Can't dup: $!";
        $| = 1; # turn off buffering for STDOUT
        exec "/sbin/$iptables_bin-save", "-c" or die;
    }
    waitpid $pid2 => 0;
    die "Error: /sbin/$iptables_bin-save exited with value ".($? >> 8) if $? > 0;

    # seek back to the begining, as we'll restore directly from the
    # handle and not from the file.  XXX if there was a way in Perl to
    # use open(2) with the O_TMPFILE flag we would use that to avoid
    # creating a file to start with
    seek($iptables_tmp, SEEK_SET, 0) or die "Can't seek: $!";

    push @CLEANUP, sub() {
        print STDERR "[$$] Restoring iptables\n" if $OPTS{debug};
        my $pid2 = fork() // die "fork: $!";
        unless ($pid2) {
            open STDIN, '<&', $iptables_tmp or die "Can't dup: $!";
            open STDOUT, '>', '/dev/null'   or die "Can't open /dev/null: $!";
            exec "/sbin/$iptables_bin-restore", "-c" or die;
        }
        waitpid $pid2 => 0;
        warn "Warning: /sbin/$iptables_bin-restore exited with value ".($? >> 8) if $? > 0;
    };

    # it's safe to install the new iptables to open $port now that the
    # restore hook is in place
    my $mask = $fam == PF_INET  ? ($addr eq INADDR_ANY  ? '0' : '32')
             : $fam == PF_INET6 ? ($addr eq IN6ADDR_ANY ? '0' : '128')
             : die;
    my $dest = Socket::inet_ntop($fam, $addr) .'/'. $mask;

    system ("/sbin/$iptables_bin", qw/-I INPUT  -p tcp -m tcp -m state/,
            '-d', $dest, '--dport', $port,
            '--state', 'NEW,ESTABLISHED', '-j', 'ACCEPT') == 0 or die;
    system ("/sbin/$iptables_bin", qw/-I OUTPUT -p tcp -m tcp -m state/,
            '-s', $dest, '--sport', $port,
            '--state',     'ESTABLISHED', '-j', 'ACCEPT') == 0 or die;

    return $tmpdir;
}


#############################################################################
# Spawn the client component, and wait for it to return.
# If $args->{in} is defined, the data is written to the client's STDIN.
# If $args->{out} is defined, its value is set to client's STDOUT data.
#
sub acme_client($@) {
    my $args = shift;
    my @args = @_;

    my @stat;
    my $conf = $CONFIG->{client};
    my $sockname = $OPTS{socket} // $conf->{socket} // die "Missing socket option\n";
    $sockname = $sockname =~ /\A(\p{Print}+)\z/ ? $1 : die "Invalid socket name\n"; # untaint $sockname

    # ensure we're the only user with write access to the parent dir
    my $dirname = $sockname =~ s/[^\/]+$//r;
    @stat = stat($dirname) or die "Can't stat $dirname: $!";
    die "Error: insecure permissions on $dirname\n" if ($stat[2] & 0022) != 0;

    # ensure we're the only user with read/write access to the socket
    @stat = stat($sockname) or die "Can't stat $sockname: $!  (Is letsencrypt-accountd running?)\n";
    die "Error: insecure permissions on $sockname\n" if ($stat[2] & 0066) != 0;

    # connect(2) to the socket
    socket(my $client, PF_UNIX, SOCK_STREAM, 0) or die "socket: $!";
    my $sockaddr = Socket::sockaddr_un($sockname) // die "Invalid address $sockname\n";
    until (connect($client, $sockaddr)) {
        next if $! == EINTR; # try again if connect(2) was interrupted by a signal
        die "connect: $!";
    }

    # use execve(2) rather than a Perl pseudo-process to ensure that the
    # child doesn't have access to the parent's memory
    my @fileno = map { fileno($_) =~ /^(\d+)$/ ? $1 : die } ($CONFFILE, $client); # untaint fileno
    spawn({%$args{qw/in out/}, child => sub() {
        drop_privileges($conf->{user}, $conf->{group}, $args->{chdir} // '/');
        set_FD_CLOEXEC($_, 0) foreach ($CONFFILE, $client);
        seek($CONFFILE, SEEK_SET, 0) or die "Can't seek: $!";
        $ENV{DEBUG} = $OPTS{debug};
    }}, $conf->{command}, $COMMAND, @fileno, @args);
}

sub spawn($@) {
    my $args = shift;
    my @exec = @_;

    # create communication pipes if needed
    my ($in_rd, $in_wd, $out_rd, $out_wd);
    if (defined $args->{in}) {
        pipe $in_rd, $in_wd or die "pipe: $!";
    }
    if (defined $args->{out}) {
        pipe $out_rd, $out_wd or die "pipe: $!";
    }

    my $pid = fork() // "fork: $!";
    unless ($pid) {
        # child
        $args->{child}->() if defined $args->{child};
        if (defined $args->{in}) {
            close $in_wd or die "Can't close: $!";
            open STDIN, '<&', $in_rd or die "Can't dup: $!";
        } else {
            open STDIN, '<', '/dev/null' or die "Can't open /dev/null: $!";
        }
        if (defined $args->{out}) {
            close $out_rd or die "Can't close: $!";
            open STDOUT, '>&', $out_wd or die "Can't dup: $!";
        } else {
            open STDOUT, '>', '/dev/null' or die "Can't open /dev/null: $!";
        }
        exec { $exec[0] } @exec or die;
    }
    push @CLEANUP, sub() {
        kill 15 => $pid;
        waitpid $pid => 0;
    };

    # parent
    print STDERR "[$$] Forking $exec[0], child PID $pid\n" if $OPTS{debug};
    if (defined $args->{in}) {
        $in_rd->close() or die "Can't close: $!";
        $in_wd->print($args->{in});
        $in_wd->close() or die "Can't close: $!";
    }
    if (defined $args->{out}) {
        $out_wd->close() or die "Can't close: $!";
        ${$args->{out}} = do { local $/ = undef; $out_rd->getline() };
        $out_rd->close() or die "Can't close: $!";
    }
    waitpid $pid => 0;
    pop @CLEANUP;
    undef ${$args->{out}} if defined $args->{out} and $? > 0;
    return $? > 255 ? ($? >> 8) : $? > 0 ? 1 : 0;
}


#############################################################################
# Install the certificate
#
sub install_cert($$@) {
    my $filename = shift;
    my $x509 = shift;

    open my $fh, '>', $filename or die "Can't open $filename: $!";
    print $fh $x509;
    foreach (@_) { # append the chain
        open my $fh2, '<', $_ or die "Can't open $_: $!";
        my $ca = do { local $/ = undef; $fh2->getline() };
        print $fh $ca;
        close $fh2 or die "Can't close: $!";
    }
    close $fh or die "Can't close: $!";
}


#############################################################################
# new-reg [--agreement-uri=URI] [CONTACT ..]
# reg=URI [--agreement-uri=URI] [CONTACT ..]
#
if ($COMMAND eq 'new-reg' or $COMMAND =~ /^reg=/) {
    die "Invalid registration URI (use the 'new-reg' command to determine the URI)\n"
        if $COMMAND eq 'reg=';
    $OPTS{'agreement-uri'} = $OPTS{'agreement-uri'} =~ /\A(\p{Print}+)\z/ ? $1
                           : die "Invalid value for --agreement-uri\n"
        if defined $OPTS{'agreement-uri'};

    unshift @ARGV, ($OPTS{'agreement-uri'} // '');
    exit acme_client({}, @ARGV);
}


#############################################################################
# new-cert [SECTION ..]
#   TODO: renewal without the account key, see
#         https://github.com/letsencrypt/acme-spec/pull/168
#
elsif ($COMMAND eq 'new-cert') {
    my $conf;
    do {
        my $conffile = $OPTS{'config-certs'} // $CONFIG->{_}->{'config-certs'} // first { -f $_ }
            ( "./$NAME-certs.conf"
            , ($ENV{XDG_CONFIG_HOME} // "$ENV{HOME}/.config")."/letsencrypt-tiny/$NAME-certs.conf"
            , "/etc/letsencrypt-tiny/$NAME-certs.conf"
            );
        die "Error: Can't find certificate configuration file\n" unless defined $conffile;
        my $h = Config::Tiny::->read($conffile) or die Config::Tiny::->errstr()."\n";
        my $defaults = delete $h->{_} // {};
        my @valid = qw/certificate certificate-chain certificate-key min-days CAfile
                       hash keyUsage subject subjectAltName chown chmod notify/;
        foreach my $s (keys %$h) {
            $conf->{$s} = { map { $_ => delete $h->{$s}->{$_} } @valid };
            die "Unknown option(s) in [$s]: ".join(', ', keys %{$h->{$s}})."\n" if %{$h->{$s}};
            $conf->{$s}->{$_} //= $defaults->{$_} foreach keys %$defaults;
        }
    };

    my $challenge_dir;
    my $rv = 0;
    foreach my $s (@ARGV ? @ARGV : keys %$conf) {
        my $conf = $conf->{$s} // do {
            print STDERR "Warning: No such section $s, skipping\n";
            $rv = 1;
            next;
        };

        my $certtype = first { defined $conf->{$_} } qw/certificate certificate-chain/;
        unless (defined $certtype) {
            print STDERR "[$s] Warning: Missing 'certificate' and 'certificate-chain', skipping\n";
            $rv = 1;
            next;
        }

        # skip certificates that expire at least $conf->{'min-days'} days in the future
        if (-f $conf->{$certtype} and defined (my $t = x509_enddate($conf->{$certtype}))) {
            my $d = $conf->{'min-days'} // 10;
            if ($d > 0 and $t - time > $d*86400) {
                my $d = POSIX::strftime('%Y-%m-%d %H:%M:%S UTC', gmtime($t));
                print STDERR "[$s] Valid until $d, skipping\n";
                next;
            }
        }

        # generate the CSR
        my $csr = gen_csr(%$conf{qw/certificate-key subject subjectAltName keyUsage hash/}) // do {
            print STDERR "[$s] Warning: Couldn't generate CSR, skipping\n";
            $rv = 1;
            next;
        };

        # spawn the webserver if not done already
        $challenge_dir //= spawn_webserver();

        # list all authorization domains to request
        my @authz;
        push @authz, $1 if defined $conf->{subject} =~ /\A.*\/CN=($RE_DOMAIN)\z/o;
        if (defined $conf->{subjectAltName}) {
            foreach my $d (split /,/, $conf->{subjectAltName}) {
                next unless $d =~ s/\A\s*DNS://;
                if ($d =~ /\A$RE_DOMAIN\z/o) {
                    push @authz, $d unless grep {$_ eq $d} @authz;
                } else {
                    print STDERR "[$s] Warning: Ignoring invalid domain $d\n";
                }
            }
        }

        my ($x509, $csr_pubkey, $x509_pubkey);
        print STDERR "[$s] Will request authorization for: ".join(", ", @authz), "\n" if $OPTS{debug};
        if (acme_client({chdir => $challenge_dir, in => $csr, out => \$x509}, @authz)) {
            print STDERR "[$s] Error: Couldn't issue X.509 certificate!\n";
            $rv = 1;
            next;
        }

        # extract pubkeys from CSR and cert, and ensure they match
        spawn({in => $csr,  out => \$csr_pubkey }, qw/openssl req  -inform DER -noout -pubkey/);
        spawn({in => $x509, out => \$x509_pubkey}, qw/openssl x509 -inform PEM -noout -pubkey/);
        unless (defined $x509_pubkey and defined $csr_pubkey and $x509_pubkey eq $csr_pubkey) {
            print STDERR "[$s] Error: Received bogus X.509 certificate from ACME server!\n";
            $rv = 1;
            next;
        };

        # verify certificate validity against the CA
        $conf->{CAfile} //= '/usr/share/letsencrypt-tiny/lets-encrypt-x1-cross-signed.pem';
        if ($conf->{CAfile} ne '' and spawn({in => $x509}, 'openssl', 'verify', '-CAfile', $conf->{CAfile},
                                                                      qw/-purpose sslserver -x509_strict/)) {
            print STDERR "[$s] Error: Received invalid X.509 certificate from ACME server!\n";
            $rv = 1;
            next;
        }

        # install certificate
        if (defined $conf->{'certificate'}) {
            print STDERR "Installing X.509 certificate $conf->{'certificate'}\n";
            install_cert($conf->{'certificate'}, $x509);
        }
        if (defined $conf->{'certificate-chain'}) {
            print STDERR "Installing X.509 certificate chain $conf->{'certificate-chain'}\n";
            install_cert($conf->{'certificate-chain'}, $x509, $conf->{CAfile});
        }

        if (defined $conf->{chown}) {
            my ($user, $group) = split /:/, $conf->{chown}, 2;
            my $uid = getpwnam($user) // die "Can't getpwnam($user): $!";
            my $gid = defined $group ? (getgrnam($group) // die "Can't getgrnam($group): $!") : -1;
            foreach (grep defined, @$conf{qw/certificate certificate-chain/}) {
                chown($uid, $gid, $_) or die "Can't chown: $!";
            }
        }
        if (defined $conf->{chmod}) {
            my $mode = oct($conf->{chmod}) // die;
            foreach (grep defined, @$conf{qw/certificate certificate-chain/}) {
                chmod($mode, $_) or die "Can't chown: $!";
            }
        }

        my @certopts = join ',', qw/no_header no_version no_pubkey no_sigdump/;
        open my $fh, '|-', qw/openssl x509 -noout -fingerprint -sha256 -text -certopt/, @certopts
            or die "fork: $!";
        print $fh $x509;
        close $fh or die $! ?
            "Can't close: $!" :
            "Error: x509(1ssl) exited with value ".($? >> 8)."\n";

        if (defined $conf->{notify}) {
            print STDERR "Running notification command `$conf->{notify}`\n";
            if (system($conf->{notify}) != 0) {
                print STDERR "Warning: notification command exited with value ".($? >> 8)."\n";
                $rv = 1;
            }
        }
    }
    undef $challenge_dir;
    exit $rv;
}


#############################################################################
# revoke-cert FILE [FILE ..]
#
elsif ($COMMAND eq 'revoke-cert') {
    die "Nothing to revoke\n" unless @ARGV;
    my $rv = 0;
    foreach my $filename (@ARGV) {
        print STDERR "Revoking $filename\n";

        # conversion PEM -> DER
        open my $fh, '-|', qw/openssl x509 -outform DER -in/, $filename or die "fork: $!";
        my $der = do { local $/ = undef; <$fh> };
        close $fh or die $! ?
            "Can't close: $!" :
            "Error: x509(1ssl) exited with value ".($? >> 8)."\n";

        my @certopts = join ',', qw/no_header no_version no_pubkey no_sigdump no_extensions/;
        open my $fh2, '|-', qw/openssl x509 -inform DER -noout -fingerprint -sha256 -text -certopt/, @certopts
            or die "fork: $!";
        print $fh2 $der;
        close $fh2 or die $! ?
            "Can't close: $!" :
            "Error: x509(1ssl) exited with value ".($? >> 8)."\n";

        if (acme_client({in => $der})) {
            print STDERR "Warning: Couldn't revoke $filename\n";
            $rv = 1;
        }
    }
    exit $rv;
}


#############################################################################
#
else {
    die "Unknown command $COMMAND"
}


END {
    local $?;
    $_->() foreach reverse @CLEANUP;
}