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.

SEE ALSO

       uacme(1)

AUTHOR

       ualpn was written by Nicola Di Lieto

COPYRIGHT

       Copyright © 2019-2021 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/.