Ubuntu Manpage: lacme - ACME client written with process isolation and minimal privileges in mind

NAME

       lacme - ACME client written with process isolation and minimal privileges in mind

SYNOPSIS

       lacme [--config=FILENAME] [--socket=PATH] [OPTION ...] COMMAND [ARGUMENT ...]

DESCRIPTION

lacme is a small ACME client written with process isolation and minimal privileges in
mind. It is divided into four components, each with its own executable:

1. A lacme-accountd(1) process to manage the account key and issue SHA-256 signatures
needed for each ACME command. (This process binds to a UNIX-domain socket to reply to
signature requests from the ACME client.) One can use the UNIX-domain socket forwarding
facility of OpenSSH 6.7 and later to run lacme-accountd(1) and lacme on different
hosts. Alternatively, the lacme-accountd(1) process can be spawned by the “master”
lacme process below; in that case, the two processes communicate through a socket pair.

2. A “master” lacme process, which runs as root and is the only component with access to
the private key material of the server keys. It is used to fork the ACME client (and
optionally the ACME webserver) after dropping root privileges. For certificate
issuances (new-cert command), it also generates Certificate Signing Requests, then
verifies the validity of the issued certificate, and optionally reloads or restarts
services when the notify option is set.

3. An actual ACME client (specified with the command option of the [client] section of the
configuration file), which builds ACME commands and dialogues with the remote ACME
server. Since ACME commands need to be signed with the account key, the “master” lacme
process passes the lacme-accountd(1) UNIX-domain socket to the ACME client: data
signatures are requested by writing the data to be signed to the socket.

4. For certificate issuances (new-cert command), an optional webserver (specified with the
command option of the [webserver] section of the configuration file), which is spawned
by the “master” lacme. (The only challenge type currently supported by lacme is
http-01, which requires a webserver to answer challenges.) That webserver only
processes GET and HEAD requests under the /.well-known/acme-challenge/ URI. Moreover
temporary iptables(8) rules can be automatically installed to open the HTTP port.

COMMANDS

       lacme [--agreement-uri=URI] new-reg [CONTACT ...]
              Register  the  account  key  managed  by  lacme-accountd(1).   A  list  of  CONTACT
              information (such as maito: URIs) can be specified  in  order  for  the  server  to
              contact  the  client for issues related to this registration (such as notifications
              about server-initiated revocations).

              --agreement-uri= can be used to specify a URI referring to a  subscriber  agreement
              or  terms  of  service  provided  by  the server; adding this options indicates the
              client's agreement with the referenced terms.  Note that the server  might  require
              the client to agree to subscriber agreement before performing any further actions.

              If  the  account  key  is  already registered, lacme prints the URI of the existing
              registration and aborts.

       lacme [--agreement-uri=URI] reg=URI [CONTACT ...]
              Dump or edit the registration URI (relative  to  the  ACME  server  URI,  which  is
              specified  with  the  server  option  of  the [client] section of the configuration
              file).

              When specified, the list of CONTACT information and the agreement URI are  sent  to
              the server to replace the existing values.

       lacme [--config-certs=FILE] [--min-days=INT] new-cert [SECTION ...]
              Read  the  certificate  configuration  FILE (see the certificate configuration file
              section below for the configuration options), and request new Certificate  Issuance
              for each of its sections (or the given list of SECTIONs).

       lacme revoke-cert FILE [FILE ...]
              Request  that  the  given  certificate(s)  FILE(s)  be  revoked.  For this command,
              lacme-accountd(1) can be pointed to either the account key or the server's  private
              key.

GENERIC OPTIONS

       --config=filename
              Use  filename  as configuration file.  See the configuration file section below for
              the configuration options.

       --socket=path
              Use path as the lacme-accountd(1) UNIX-domain socket to connect  to  for  signature
              requests  from  the  ACME  client.  lacme aborts if path is readable or writable by
              other users, or  if  its  parent  directory  is  writable  by  other  users.   This
              command-line  option  overrides  the  socket  option of the [client] section of the
              configuration file.  Moreover this option is ignored when  the  configuration  file
              has an [accountd] section; in that case lacme spawns lacme-accountd(1), and the two
              processes communicate through a socket pair.

       -h, --help
              Display a brief help and exit.

       -q, --quiet
              Be quiet.

       --debug
              Turn on debug mode.

CONFIGURATION FILE

If --config= is not given, lacme uses the first existing configuration file among
./lacme.conf, $XDG_CONFIG_HOME/lacme/lacme.conf (or ~/.config/lacme/lacme.conf if the
XDG_CONFIG_HOME environment variable is not set), and /etc/lacme/lacme.conf. Valid
options are:

DEFAULT SECTION
config-certs
For certificate issuances (new-cert command), specify the space-separated list of
certificate configuration files or directories to use (see the certificate
configuration file section below for the configuration options).

Paths not starting with / are relative to the directory name of the configuration
filename. The list of files and directories is processed in order, with the later
items taking precedence. Files in a directory are processed in lexicographic
order, only considering the ones with suffix .conf.

Default: lacme-certs.conf lacme-certs.conf.d/.

[client] SECTION
This section is used for configuring the ACME client (which takes care of ACME commands
and dialogues with the remote ACME server).

socket See --socket=. Default: $XDG_RUNTIME_DIR/S.lacme if the XDG_RUNTIME_DIR
environment variable is set.

user The username to drop privileges to (setting both effective and real uid). Preserve
root privileges if the value is empty (not recommended). Default: nobody.

group The groupname to drop privileges to (setting both effective and real gid, and also
setting the list of supplementary gids to that single group). Preserve root
privileges if the value is empty (not recommended). Default: nogroup.

command
Path to the ACME client executable. Default: /usr/lib/lacme/client.

server Root URI of the ACME server. Default: https://acme-v01.api.letsencrypt.org/.

timeout
Timeout in seconds after which the client stops polling the ACME server and
considers the request failed. Default: 10.

SSL_verify
Whether to verify the server certificate chain. Default: Yes.

SSL_version
Specify the version of the SSL protocol used to transmit data.

SSL_cipher_list
Specify the cipher list for the connection, see ciphers(1ssl) for more information.

[webserver] SECTION
This section is used to configure how ACME challenge responses are served during
certificate issuance.

listen Comma- or space-separated list of addresses to listen on. Valid addresses are of
the form IPV4:PORT, [IPV6]:PORT (where the :PORT suffix is optional and defaults to
the HTTP port 80), or an absolute path of a UNIX-domain socket (created with mode
0666). Default: /var/run/lacme-www.socket.

Note: The default value is only suitable when an external HTTP daemon is publicly
reachable and passes all ACME challenge requests to the webserver component through
the UNIX-domain socket /var/run/lacme-www.socket (for instance using the provided
/etc/lacme/apache2.conf or /etc/lacme/nginx.conf configuration snippets for each
virtual host requiring authorization). If there is no HTTP daemon bound to port 80
one needs to set listen to [::] (or 0.0.0.0 [::] when dual IPv4/IPv6 stack is
disabled or unavailable), and possibly also set iptables to Yes.

challenge-directory
Specify a non-existent directory under which an external HTTP daemon is configured
to serve GET requests for challenge files under /.well-known/acme-challenge/ (for
each virtual host requiring authorization) as static files. This option is
required when listen is empty.

user The username to drop privileges to (setting both effective and real uid). Preserve
root privileges if the value is empty (not recommended). Default: www-data.

command
Path to the ACME webserver executable. A separate process is spawned for each
address to listen on. (In particular no webserver process is forked when the
listen option is empty.) Default: /usr/lib/lacme/webserver.

iptables
Whether to automatically install temporary iptables(8) rules to open the
ADDRESS[:PORT] specified with listen. The rules are automatically removed once
lacme exits. Default: No.

[accountd] SECTION
This section is used for configuring the lacme-accountd(1) process. If the section
(including its header) is absent or commented out, lacme connects to an existing
UNIX-domain socket bound by a running lacme-accountd(1) process.

user The username to drop privileges to (setting both effective and real uid). Preserve
root privileges if the value is empty.

group The groupname to drop privileges to (setting both effective and real gid, and also
setting the list of supplementary gids to that single group). Preserve root
privileges if the value is empty.

command
Path to the lacme-accountd(1) executable. Default: /usr/bin/lacme-accountd.

config Path to the lacme-accountd(1) configuration file. Default:
/etc/lacme/lacme-accountd.conf.

privkey
The (private) account key to use for signing requests. See lacme-accountd(1) for
details.

quiet Be quiet. Possible values: Yes/No.

CERTIFICATE CONFIGURATION FILE

For certificate issuances (new-cert command), a separate file is used to configure paths
to the certificate and key, as well as the subject, subjectAltName, etc. to generate
Certificate Signing Requests. Each section denotes a separate certificate issuance.
Valid options are:

certificate
Where to store the issued certificate (in PEM format). At least one of certificate
or certificate-chain is required.

certificate-chain
Where to store the issued certificate, concatenated with the content of the file
specified specified with the CAfile option (in PEM format). At least one of
certificate or certificate-chain is required.

certificate-key
Path the service's private key. This option is required. The following command
can be used to generate a new 4096-bits RSA key in PEM format with mode 0600:

openssl genrsa 4096 | install -m0600 /dev/stdin /path/to/srv.key

min-days
For an existing certificate, the minimum number of days before its expiration date
the section is considered for re-issuance. A negative value forces reissuance,
while the number 0 limits reissuance to expired certificates. Default: the value
of the CLI option --min-days, or 21 if there is no such option.

CAfile Path to the issuer's certificate. This is used for certificate-chain and to verify
the validity of each issued certificate. Specifying an empty value skip
certificate validation. Default:
/usr/share/lacme/lets-encrypt-x3-cross-signed.pem.

hash Message digest algorithm to sign the Certificate Signing Request with.

keyUsage
Comma-separated list of Key Usages, see x509v3_config(5ssl).

subject
Subject field of the Certificate Signing Request, in the form
/type0=value0/type1=value1/type2=.... This option is required.

subjectAltName
Comma-separated list of Subject Alternative Names, in the form
type0:value1,type1:value1,type2:... The only type currently supported is DNS, to
specify an alternative domain name.

chown An optional username[:groupname] to chown the issued certificate and
certificate-chain to.

chmod An optional octal mode to chmod the issued certificate and certificate-chain to.

notify Command to pass the the system's command shell (/bin/sh -c) after successful
installation of the certificate and/or certificate-chain.

EXAMPLES

              ~$ sudo lacme new-reg mailto:noreply@example.com
              ~$ sudo lacme reg=/acme/reg/123456 --agreement-uri=https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf
              ~$ sudo lacme new-cert
              ~$ sudo lacme revoke-cert /path/to/server/certificate.pem

BUGS AND FEEDBACK

       Bugs  or  feature requests for lacme should be filed with the Debian project's bug tracker
       at <https://www.debian.org/Bugs/>.

AUTHORS

       Guilhem Moulin (mailto:guilhem@fripost.org).

                                          December 2015                                  lacme(1)