ualpn.1.txt

UALPN(1)
========
:doctype: manpage
:man source:   ualpn
:man version:  {revision}
:man manual:   User Commands


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 {runstatedir}/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 {runstatedir}/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 (C) 2019-2024 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/>.