APACHE

1. Initial configuration

Run

    acmeman --setup
    

It will detect the Apache layout, install an additional Apache configuration file, httpd-letsencrypt.conf and print the instructions on how to enable it. Follow them and enable the mod_macro module.

2. Apache domain setup: plain HTTP

To declare that a virtual host needs SSL certificate, add the following line to the Apache VirtualHost block serving plain HTTP for that host:

    Use LetsEncryptChallenge
    

This will instruct Apache httpd to serve ACME challenges and acmeman to request a certificate for that virtual host. The hostname declared with the ServerName statement will be used as the CN for the certificate, and any names declared via ServerAlias statements will form the list of alternative names. For example:

    <VirtualHost *:80>
        ServerName example.org
        ServerAlias www.example.com
        Use LetsEncryptChallenge
        ...
    </VirtualHost>
    

3. Issue the certificate

This step is needed if there is no certificate for this domain yet. Reload httpd to fire up the new configuration and run acmeman to issue the certificate. If anything goes wrong, try adding one or more -d options to acmeman to see what's going on. You can also use the -s option during initial debugging of the configuration. This option instructs acmeman to use the staging ACME server, instead of the production one. This eliminates the risk of hitting the ACME request per IP limit.

4. Apache domain setup: HTTPS

To use the created certificate, add another virtual server for that domain, with the same ServerName as above and with 443 as its port value. Add the following statement to it:

    Use LetsEncryptSSL DOMAIN
    

where DOMAIN must be the same as the ServerName value. For example, the HTTPS virtual host corresponding to the above example will be:

    <VirtualHost *:443>
        ServerName example.org
        ServerAlias www.example.com
        Use LetsEncryptSSL example.org
        ...
    </VirtualHost>
    

This can be further simplified by using the LetsEncryptServer macro instead of the ServerName and LetsEncryptSSL statements, as in:

    <VirtualHost *:443>
        Use LetsEncryptServer example.org
        ServerAlias www.example.com
        ...
    </VirtualHost>
    

HAPROXY

1. Create a directory for storing domain name files

This directory will keep domain name files, named after the corresponding HAProxy backends. E.g.

    mkdir /etc/haproxy/hosts
    

2. Configure acmeman

Example /usr/local/etc/acmeman.conf file is:

    [core]
       source = file /etc/haproxy/hosts
       postrenew = /usr/sbin/service haproxy restart
    [files default]
       type = single
       certificate-file = /etc/ssl/acme/crt/$domain.pem
    

The core section declares the source to use. The first argument to the file source is the name of the directory where the domain name lists are stored. The postrenew statement declares the command to be run after all certificates have been renewed. In our case, this command restarts haproxy, forcing it to re-read the certificates.

The files statement instructs the program to create, for each domain, a single file containing the private key, certificate chain and the domain certificate for that domain. The $domain variable in the certificate-file declaration will be replaced by the first domain name from the list (the CN) for that certificate.

This configuration will keep a separate certificate for each backend in haproxy that supports https access. If concerned about request rate limit, you can instruct acmeman to maintain a single certificate with all domain names as X509v3 subject alternative names instead. To do so, use the --host option in the source definition. Its argument specifies the domain name to use as the CN for the certificate. E.g.:

    [core]
       source = file /etc/haproxy/hosts --host=www.example.com
       ...
    

3. Configure haproxy

First, configure the plain HTTP frontend, which will be responsible for serving ACME challenges and redirecting the rest of the requests to HTTPS. The simplest definition is:

    frontend http-in
        mode http
        bind :::80 v4v6
        http-request redirect code 301 location https://%[hdr(host)]%[capture.req.uri] unless { path_beg /.well-known/acme-challenge }
        use_backend acme if { path_beg /.well-known/acme-challenge }
    

Actual backend configuration for the acme backend is beyond the scope of this manual. Use some simple and lightweight http server capable of serving static files, such as fileserv (<https://www.gnu.org.ua/projects/fileserv>), for example.

Then, configure HTTPS section to use certificates from the certificate file directory:

    frontend https-in
        mode http
        bind :::443 v4v6 ssl crt /etc/ssl/acme/crt
        # Direct each group of domain names to the corresponding
        # backend.
        use_backend d1 if { hdr(host) -f /etc/haproxy/hosts/d1 }
        use_backend d2 if { hdr(host) -f /etc/haproxy/hosts/d2 }
        ...
    

Finally, define the backends.

Direct configuration

    [core]
        source = null

Then, for each domain name use the domain section, as shown in the example below:

    [domain example.com]
        alt = www.example.com
        files = default

This section instructs acmeman that a certificate is needed for domain example.com, using www.example.com as its alternative name, The files statement identifies the name of a files section containing rules for creating certificate files for that domain. This section must be defined elsewhere in the configuration file. For example:

    [files default]
        type = split
        certificate-file = /etc/ssl/acme/$domain/cert.pem
        key-file = /etc/ssl/acme/$domain/privkey.pem
        ca-file = /etc/ssl/acme/$domain/ca.pem
        argument = $domain

This definition tells acmeman that it should store certificate, certificate key, and certificate authority chain in three separate files. Names of these files will be created by replacing the $domain string in the corresponding definition with the domain name from the domain section.

Several [domain] section can share the same [files] definition, or they can have their one, depending on your needs.

[core]

rootdir=DIR

Defines the root directory to use instead of the default </var/www/acme>. Root directory is the directory under which the .well-known/acme-challenge subdirectory is located.

time-delta=SECONDS

Sets the time window before the actual expiration time, when the certificate becomes eligible for renewal. N is time in seconds. The default value is 86400, which means that acmeman will attempt to renew any certificate that expires within 24 hours.

The command line option --time-delta overrides this setting.

postrenew=COMMAND

Defines the command to be run at the end of the run if at least one certificate has been updated. Normally this command reloads the httpd server (or whatever server is using the certificates). If more than one postrenew statements are defined, they will be run in sequence, in the same order as they appeared in the configuration file.

COMMAND inherits the environment from the acmeman process, with the following additional variables:

source=NAME [ARG...]

Defines the source of domain names. The NAME parameter identifies the source, and additional arguments supply the initialization parameters.

The present version of acmeman is shipped with three sources: null, apache, and file.

The null module is an empty source. It takes no additional arguments. Use this source if all domains are described in the configuration file using one or more domain sections.

The apache source module is the default. It scans httpd configuration files as described in section apache. One argument is allowed. If supplied, it defines the apache configuration layout. Allowed values are: debian, slackware, suse and rh (for Red Hat). Without arguments, the layout will be autodetected.

The file source reads domain names from one or more disk files. A mandatory argument specifies the name of the directory where the files are located. This mode is suitable for use with haproxy pattern files.

Multiple source statements can be defined. They will be processed sequentially.

files=NAME

Identifies the [files] section which describes how to create certificate files for domains which lack explicit files keyword. Default NAME is default. See the description of the files statement in domain section.

check-alt-names=BOOL

When set to true, it instructs the program to compare the list of alternative names of each certificate with the one gathered from the Apache configuration, and reissue the certificate if the two lists don't match. This uses an ad-hoc logic, due to the deficiency of the underlying X509 module, and therefore is not enabled by default.

Valid values for BOOL are: 1, on, true, or yes, for true, and 0, off, false, or no for false.

check-dns=BOOL

When set to true (the default), the program will check whether each host name has an A DNS record pointing back to one of the IP addresses of the server. Hostnames which don't satisfy this condition will be ignored. The IP of the server is determined by looking up the A record for its hostname. This can be overridden using the my-ip configuration statement.

key-size=N

Size of the RSA key to use, in bits. Default is 4096.

my-ip=IP [IP...]

Declares IP address (or addresses) of this server. Use this keyword if the server IP cannot be reliably determined by resolving its hostname. Special IP $hostip stands for the IP retrieved by resolving the hostname.

[account]

directory=DIR

Directory where to store credential files. Defaults to /etc/ssl/acme.

id=FILE

Name of the file with account key ID. Unless FILE begins with a directory separator, it is taken relative to account.directory.

Default: /etc/ssl/acme/key.id.

key=FILE

Name of the file with account key. Unless FILE begins with a directory separator, it is taken relative to account.directory.

Default: /etc/ssl/acme/key.pem.

[domain CN]

files=ID

Identifies the [files] section which describes how to create certificate files for this domain. In the absence of this statement, the files statement from the [core] section will be used.

alt=NAME

Defines alternative name for the certificate. Multiple alt statements are allowed.

key-size=N

Size of the RSA key to use, in bits. If not set, the core.key-size setting is used.

postrenew=CMD

Run CMD after successful update. If not given, the core.postrenew commands will be run.

CMD is run in the environment inherited from the calling acmeman process with the following additional variables defined:

[files ID]

The FILENAME arguments to the keywords below can contain references to a meta-variable, which will be replaced by the actual domain name when handling this section for a particular domain. By default, this meta-variable is $domain.

type=single|split

Type of the certificate to create. When set to single, a single certificate file will be created. Its name is determined by the certificate-file statement. The file will contain the certificate, certificate chain and the signature, in this order.

When set to split, the certificate, certificate chain and the signature will be saved to three distinct files, whose names are defined by certificate-file, ca-file, and key-file, correspondingly. If ca-file is not defined, only certificate and key files will be created.

The default is split.

certificate-file=FILENAME

Defines the name of the certificate file for this domain. This statement is mandatory.

key-file=FILENAME

Defines the name of the certificate key file. This statement must be present if type is set to split.

ca-file=FILENAME

Defines the name of the certificate authority file. This statement may be present if type is set to split.

argument=STRING

Defines the name of the meta-variable in FILENAME arguments, which will be replaced with the actual domain name. Default is $domain .

null

    [core]
        source = null

Declares empty source. This means that acmeman will handle only domain names explicitly declared in the configuration file using the domain setting.

apache

    [core]
        source = apache [--server-root=DIR] [LAYOUT]

This is the default source. It assumes Apache httpd, version 2.4 or later (although only minor changes are necessary to make it work with version 2.2). The optional LAYOUT argument defines the layout of the apache configuration files. Allowed layout values are: debian, slackware, suse and rh (for Red Hat). If not supplied, the layout is determined automatically.

Use the --server-root option to supply the name of the server root directory, if for some reason the module is unable to determine it automatically.

A special directory should be configured for receiving ACME challenges.

The package provides two Apache macros: for serving ACME challenges and declaring SSL virtual hosts.

Upon startup the program scans Apache configuration for virtual hosts that use ACME certificates, checks their expiration times, and renews those of the certificates that are nearing their expiration times within a predefined number of seconds (24 hours by default). If any of the certificates were updated during the run, acmeman will restart the httpd server.

Setup

To set up the necessary infrastructure, run acmeman --setup. It will create the configuration file httpd-letsencrypt.conf, defining two macros for SSL-enabled sites (mod_macro is needed). Finally, it will create the directory /var/www/acme, which will be used for receiving and serving ACME challenges. If another directory is preferred, it can be specified as an argument to acmeman --setup.

The tool will try to determine the layout of the Apache configuration files and place the created file accordingly, so that it will be included into the main configuration file. It will print the name of the created file at the end of the run. You are advised to ensure that the file is included and that the module mod_macro is loaded prior to it. You may also wish to revise httpd-letsencrypt.conf and edit the paths to SSL files configured there. By default, the directory /etc/acme/DOMAIN will be created for each domain name needing SSL, and two files will be placed there: cert.pem, containing the leaf and intermediate certificates for that domain, and privkey.pem, containing the private key for that domain.

The program will refuse to overwrite existing files httpd-letsencrypt.conf, unless given the --force (-F) option.

Configuring SSL

To declare that a virtual host needs SSL certificate, add the following line to the Apache VirtualHost block serving plain HTTP for that host:

    Use LetsEncryptChallenge

This will instruct acmeman to request a certificate for that virtual host. The hostname declared with the ServerName statement will be used as the CN for the certificate, and any names declared via ServerAlias statements will form the list of alternative names (obviously, wildcards are not allowed).

If such a certificate doesn't exist, it will be requested and created when acmeman is run.

To use the created certificate, create a new VirtualHost block that contains the following statement:

    Use LetsEncryptServer DOMAIN

where DOMAIN is the name used in the ServerName statement of the plain HTTP configuration. Copy the ServerAlias statements (if any), and add the rest of configuration statements. Note, that you need not use the ServerName statement, as it will be included when the LetsEncryptServer macro is expanded.

Example:

    <VirtualHost *:80>
        ServerName example.org
        ServerAlias www.example.com
        Use LetsEncryptChallenge
        ...
    </VirtualHost>

    <VirtualHost *:443>
        Use LetsEncryptServer example.org
        ServerAlias www.example.com
        ...
    </VirtualHost>

Alternatively, you can use the LetsEncryptSSL macro, which differs from LetsEncryptServer in that it configures only SSL settings, without the ServerName statement, which therefore must be included explicitly:

    <VirtualHost *:443>
        ServerName example.org
        ServerAlias www.example.com
        Use LetsEncryptSSL example.org
        ...
    </VirtualHost>

LetsEncrypt limits the number of certificates requested for a single registered domain per week (at the time of this writing - 20). To avoid hitting that limit, you may wish to use the same certificate for different virtual hosts. The special macro LetsEncryptReference is provided for that purpose. Suppose, for example, that you wish to configure server name git.example.org to use the same certificate as example.org (configured in the example above). You then declare the virtual host for the plain HTTP as follows:

    <VirtualHost *:80>
        ServerName git.example.org
        Use LetsEncryptReference example.org
        ...
    </VirtualHost>

The argument to the LetsEncryptReference macro indicates the CN name of the certificate to which the current server name (and aliases, if any) are to be added as alternative names. The corresponding virtual host for SSL will use the LetsEncryptSSL macro to configure the correct certificate:

    <VirtualHost *:80>
        ServerName git.example.org
        Use LetsEncryptSSL example.org
        ...
    </VirtualHost>

file

    [core]
        source = file PATTERN [--ignore=RX] [--host=HOST]

Domain names will be read from files matching PATTERN. The argument can be a single file or directory name, or a valid globbing pattern. If PATTERN is a directory name, the module will read all files from that directory, except those matching the following perl regexp: "^\.|~$|\.bak$|^#.*#$". The default regexp can be overridden using the --ignore (-i) option.

The input files must contain exactly one domain name per line. No empty lines or comments are allowed. The first domain name will become the CN of the issued certificate. The rest of domain names will form alternative names.

If the --host (-h) option is used, only one certificate will be issued. The HOST will be used as its CN. All the domain names read from the input files will form the list of its alternative names.