Ubuntu Manpage: ualpn - lightweight proxying ACMEv2 tls-alpn-01 responder

NAME

       ualpn - lightweight proxying ACMEv2 tls-alpn-01 responder

SYNOPSIS

       ualpn [-4|--ipv4] [-6|--ipv6] [-b|--bind address[@port]] [-c|--connect address[@port]]
       [-d|--daemon] [-l|--logfile file] [-m|--max-auths N] [-n|--num-workers N] [-p|--pidfile
       file] [-P|--proxy N] [-r|--chroot dir] [-s|--sock path] [-S|--sock-mode mode]
       [-t|--terminate] [-u|--user user[:group]] [-v|--verbose ...] [-V|--version] [-?|--help]

DESCRIPTION

ualpn is a lightweight proxying ACMEv2 tls-alpn-01 challenge responder compliant with
RFC8737 (https://tools.ietf.org/html/RFC8737) and RFC8738
(https://tools.ietf.org/html/RFC8738).

Depending on how it is invoked, ualpn runs in either client or server mode. In client mode
ualpn connects to a running server mode instance of itself through a unix domain socket,
in order to add or remove ACMEv2 authorizations. See CLIENT MODE below.

In server mode ualpn listens for incoming connections (by default on port 443, which is
mandatory for tls-alpn-01 challenges). It then handles any such connection in one of two
different ways:

• if the connection begins with a "ClientHello" TLS handshake packet including a
"acme-tls/1" RFC7301 Application Level Protocol Negotiation extension and a RFC6066
Server Name Indication extension matching an identifier for which it has an
authorization, ualpn performs the tls-alpn-01 handshake and closes the connection;

• otherwise ualpn transparently proxies the connection to one of the backend servers it
is configured with. By default ualpn adds PROXY v1 headers
(http://www.haproxy.org/download/1.8/doc/proxy-protocol.txt) in order to safely
transport connection information such as the client’s address to the backend. The
PROXY protocol is currently supported by apache, nginx and several other server
programs.

The event-driven implementation is based on libev (http://libev.schmorp.de) and
considerably reduces the cost of context switches and memory usage. In addition on systems
such as Linux supporting the splice() system call, ualpn is able to move network data
without copying it to/from kernel/user address space.

OPTIONS

-4, --ipv4
Only listen to IPv4 connections

-6, --ipv6
Only listen to IPv6 connections

-b, --bind address[@port]
Enable server mode and listen to address. The address must be specified in numeric
format using the standard IPv4 or IPv6 notation. Optionally, a port number can be
given (default is 443). This flag can be specified multiple times to listen to
multiple IP addresses. If this flag is not specified and server mode was enabled by
some other option, ualpn listens to the wildcard interface; otherwise it runs in
client mode (see CLIENT MODE below).

-c, --connect address[@port]
Enable server mode and add a new backend. The backend address must be specified in
numeric format using the standard IPv4 or IPv6 notation. Optionally, a port number can
be given (default is 443). This flag can be specified multiple times to add multiple
backends. This flag must be specified at least once in server mode.

-d, --daemon
Enable server mode and fork in the background

-l, --logfile file
Log to file. By default ualpn logs to syslog if -d, --daemon was specified or stderr
otherwise. See also -v, --verbose

-m, --max-auths N
Enable server mode and allow managing ACMEv2 tls-alpn-01 challenges for up to N
different identifiers (default 100)

-n, --num-workers N
Enable server mode and spawn N worker processes (default 2) to handle connections.
Note that worker processes are single threaded but thanks to the event based
implementation each can handle several (potentially thousands) connections
concurrently.

-p, --pidfile file
Specify pidfile location (default /run/ualpn.pid)

-P, --proxy N
Enable server mode and disable (0) or specify (1, 2) the PROXY header version (default
1). The backend server needs to be configured accordingly:

• nginx: https://docs.nginx.com/nginx/admin-guide/load-balancer/using-proxy-protocol

• apache:
https://httpd.apache.org/docs/2.4/mod/mod_remoteip.html#remoteipproxyprotocol

-r, --chroot dir
Enable server mode and specify a directory to chroot to. If logging to syslog it is
necessary to ensure that a syslogd(8) socket is available at /dev/log in the chroot
directory, otherwise ualpn will not produce any log output.

-s, --sock path
Specify unix socket path (default /run/ualpn.sock)

-S, --sock-mode mode
Enable server mode and specify socket access permissions (default 644)

-t, --terminate
Try to terminate a running ualpn server. This is achieved by looking up the process id
stored by the server in the pidfile (see -p, --pidfile) and signalling it to
terminate.

-u, --user user[:group]
Enable server mode and drop user (and optionally group) privileges to those of user
after binding the sockets. Also affects the ownership of the unix socket, pidfile and
logfile (if any).

-v, --verbose
By default ualpn only produces logs upon errors or warnings. When this option is
specified ualpn also logs notice messages. This option can be specified more than once
to increase verbosity and include information (twice) or debug (three times) messages.

-V, --version
Print program version on stderr and exit.

-?, --help
Print a brief usage text on stderr and exit.

CLIENT MODE

       In client mode ualpn pipes stdin/stdout to/from the unix socket of the running server
       instance of itself. The protocol is ASCII text based, case sensitive, line oriented, with
       two commands:

       auth identifier authorization
           The auth command instructs the running ualpn server to handle ACMEv2 tls-alpn-01
           challenges for identifier, which can be a string representing either a domain (type
           dns according to RFC8555 section 9.7.8) or an IP address (type ip according to RFC8738
           section 6).  authorization must contain the base64url encoding of the SHA-256 digest
           of the key authorization computed according to RFC8737 section 3 (note the uacme
           software executes hook scripts with the correct authorization passed as the 5th
           argument). Upon successful invocation of the auth command ualpn generates a self
           signed certificate as required by the tls-alpn-01 challenge, and then uses it to
           perform tls-alpn-01 handshakes for the given identifier.

       unauth identifier
           The unauth command instructs the running ualpn server to no longer handle ACMEv2
           tls-alpn-01 challenges for identifier.

       ualpn responds to both commands with a line beginning with either "OK" or "ERR", followed
       by a space and additional error information.

EXAMPLES

       ualpn -vv -d -u nobody:nogroup -c 127.0.0.1@4443 -S 666
           start ualpn as a daemon, binding to the default port 443 on the wildcard interface.
           Proxy connections to port 4443 on 127.0.0.1 After opening the sockets, drop the user
           privileges and run as nobody:nogroup. Allow anyone on the local host to access the
           unix socket. Also increase the verbosity to include notice and information messages.

       echo "auth www.example.com DEi0apzMOdMT2DAro57oIvn-wEzPiYcAYDh2Cvjra3I" | ualpn
           Instruct the running ualpn server to handle ACMEv2 tls-alpn-01 challenges for
           www.example.com with the given key authorization.

       echo "unauth www.example.com" | ualpn
           Instruct the running ualpn server to no longer handle ACMEv2 tls-alpn-01 challenges
           for www.example.com

EXIT STATUS

       0
           Success

       1
           Failure (syntax or usage error; configuration error; processing failure; unexpected
           error).

EXAMPLE UACME HOOK SCRIPT

       The ualpn.sh hook script included in the distribution can be used to automate the
       certificate issuance with uacme, provided ualpn is listening on port 443 of the webserver
       for the domain being validated

           #!/bin/sh
           ARGS=5
           E_BADARGS=85

           if test $# -ne "$ARGS"
           then
               echo "Usage: $(basename "$0") method type ident token auth" 1>&2
               exit $E_BADARGS
           fi

           METHOD=$1
           TYPE=$2
           IDENT=$3
           TOKEN=$4
           AUTH=$5

           if [ "$TYPE" != "tls-alpn-01" ]; then
               exit 1
           fi

           case "$METHOD" in
               "begin")
                   UALPN_OUT=$(echo "auth $IDENT $AUTH" | ualpn)
                   if [ "x$UALPN_OUT" = "xOK" ]; then
                       exit 0
                   else
                       exit 1
                   fi
                   ;;
               "done"|"failed")
                   UALPN_OUT=$(echo "unauth $IDENT" | ualpn)
                   if [ "x$UALPN_OUT" = "xOK" ]; then
                       exit 0
                   else
                       exit 1
                   fi
                   ;;
               *)
                   echo "$0: invalid method" 1>&2
                   exit 1
           esac

BUGS

       If you believe you have found a bug, please create a new issue at
       https://github.com/ndilieto/uacme/issues with any applicable information.

AUTHOR

       ualpn was written by Nicola Di Lieto

COPYRIGHT

       Copyright © 2019-2023 Nicola Di Lieto <nicola.dilieto@gmail.com>

       This file is part of uacme.

       uacme 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.

       uacme 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/.