--- name: "lacme" section: "8" platform: "linux" package: "lacme" version: "0.8.3-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/lacme/8" --- # lacme(8) 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)](/lacme-accountd/1.md) 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)](/lacme-accountd/1.md) and lacme on different hosts. Alternatively, the [lacme-accountd(1)](/lacme-accountd/1.md) 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 (newOrder command), it also generates Certificate Signing Requests, then verifies the validity of the issued certificate, and optionally reloads or restarts services when the *notify* setting is set. - 3\. An actual ACME client (specified with the *command* setting 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)](/lacme-accountd/1.md) 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 (newOrder command), an optional webserver (specified with the *command* setting 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)](/iptables/8.md) rules can be automatically installed to open the HTTP port. ## COMMANDS - lacme account \[--tos-agreed\] \[--register\] \[*CONTACT* ...\] Register (if --registered is set) a [lacme-accountd(1)](/lacme-accountd/1.md)-managed account key. A list of *CONTACT* information (such as maito: URIs) can be specified in order for the ACME server to contact the client for issues related to this registration (such as notifications about server-initiated revocations). --tos-agreed indicates agreement with the ACME server’s Terms of Service (and might be required for registration). If the account key is already registered, update the contact info with the given list of *CONTACT* information. Upon success, lacme prints the new or updated Account Object from the ACME server. - lacme newOrder \[--config-certs=*FILE*\] \[--min-days=*INT*\|--force\] \[*SECTION* ...\] 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 *SECTION*s). Command alias: new-order. The flag --force is an alias for --min-days=-1, which forces renewal regardless of the expiration date of existing certificates. - lacme revokeCert *FILE* \[*FILE* ...\] Request that the given certificate(s) *FILE*(s) be revoked. For this command, [lacme-accountd(1)](/lacme-accountd/1.md) can be pointed to either the account key or the certificate key. Command alias: revoke-cert. ## GENERIC SETTINGS - \--config=*filename* Use *filename* as configuration file instead of %E/lacme/lacme.conf. The value is subject to %-specifier expansion. See the **configuration file** section below for the configuration options. - \--socket=*path* Use *path* as the [lacme-accountd(1)](/lacme-accountd/1.md) UNIX-domain socket to connect to for signature requests from the ACME client. The value is subject to %-specifier expansion. lacme aborts if *path* exists or if its parent directory is writable by other users. Default: %t/S.lacme. This command-line option overrides the *socket* setting of the \[client\] section of the configuration file; it also causes the \[accountd\] section to be ignored. - \-h, --help Display a brief help and exit. - \-q, --quiet Be quiet. - \--debug Turn on debug mode. ## CONFIGURATION FILE Valid settings are: ### DEFAULT SECTION - *config-certs* For certificate issuances (newOrder 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). Each item in that list is independently subject to %-specifier expansion. Paths not starting with / (after %-expansion) are relative to the parent directory of the **configuration filename**. The list of files and directories is processed in the specified 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=. - *user* The username to drop privileges to (setting both effective and real uid). Skip privilege drop if the value is empty (not recommended). Default: \_lacme-client. - *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). Skip privilege drop if the value is empty (not recommended). Default: nogroup. - *command* The ACME client command. It is split on whitespace, with the first item being the command to execute, the second its first argument etc. (Note that lacme might append more arguments when executing the command internally.) Default: /usr/libexec/lacme/client. - *server* Root URI of the ACME server. Default: https://acme-v02.api.letsencrypt.org/directory. - *timeout* Timeout in seconds after which the client stops polling the ACME server and considers the request failed. Default: 30. - *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)](/ciphers/1ssl.md) 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: /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 /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* 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. The directory *must* exist beforehand, *must* be empty, and the lacme client user (by default \_lacme-client) needs to be able to create files under it. This setting is required when *listen* is empty. Moreover its value is subject to %-specifier expansion *before* privilege drop. - *user* The username to drop privileges to (setting both effective and real uid). Skip privilege drop if the value is empty (not recommended). Default: \_lacme-www. - *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). Skip privilege drop if the value is empty (not recommended). Default: nogroup. - *command* The ACME webserver command. It is split on whitespace, with the first item being the command to execute, the second its first argument etc. (Note that lacme might append more arguments when executing the command internally.) A separate process is spawned for each address to *listen* on. (In particular no webserver process is forked when the *listen* setting is empty.) Default: /usr/libexec/lacme/webserver. - *iptables* Whether to automatically install temporary [iptables(8)](/iptables/8.md) rules to open the ADDRESS\[:PORT\] specified with *listen*. The rules are automatically removed once lacme exits. This setting is ignored when *challenge-directory* is set. Default: No. ### \[accountd\] SECTION This section is used for configuring the [lacme-accountd(1)](/lacme-accountd/1.md) child process. If the section (including its header) is absent or commented out, or if the CLI option --socket is specified, then lacme connects to an existing [lacme-accountd(1)](/lacme-accountd/1.md) process via the specified UNIX-domain socket. - *user* The username to drop privileges to (setting both effective and real uid). Skip privilege drop if the value is empty (the default). - *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). Skip privilege drop if the value is empty (the default). - *command* The [lacme-accountd(1)](/lacme-accountd/1.md) command. It is split on whitespace, with the first item being the command to execute, the second its first argument etc. (Note that lacme appends more arguments when executing the command internally.) Each item in that list is independently subject to %-specifier expansion *after* privilege drop. Default: /usr/bin/lacme-accountd. Use for instance \`ssh -T lacme@account.example.net lacme-accountd\` in order to spawn a remote [lacme-accountd(1)](/lacme-accountd/1.md) server. - *config* Path to the [lacme-accountd(1)](/lacme-accountd/1.md) configuration file. Note that the value might be subject to %-expansion by [lacme-accountd(1)](/lacme-accountd/1.md). - *quiet* Be quiet. Possible values: Yes/No. ## CERTIFICATE CONFIGURATION FILE For certificate issuances (newOrder 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 settings 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 along with its chain of trust (in PEM format). At least one of *certificate* or *certificate-chain* is required. - *certificate-key* Path to the service’s private key. This setting is required. The [genpkey(1ssl)](/genpkey/1ssl.md) command can be used to generate a new service RSA key: - ``` $ install -vm0600 /dev/null /path/to/service.rsa.key $ openssl genpkey -algorithm RSA -out /path/to/service.rsa.key ``` Alternatively, for an ECDSA key using the NIST P-256 curve: - ``` $ install -vm0600 /dev/null /path/to/service.ecdsa.key $ openssl genpkey -algorithm EC -out /path/to/service.ecdsa.key \ -pkeyopt ec_paramgen_curve:P-256 \ -pkeyopt ec_param_enc:named_curve ``` lacme supports any key algorithm than the underlying libssl (OpenSSL) version is able to manipulate, but the ACME server might reject CSRs associated with private keys of deprecated and/or “exotic” algorithms. For a dual cert setup (for instance RSA+ECDSA), duplicate the certificate section and use a distinct *certificate-key* resp. *certificate* (or *certificate-chain*) value for each key algorithm. - *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. - *subject* Subject field of the Certificate Signing Request, in the form /type0=value0/type1=value1/type2=.... This setting 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. - *CAfile* Path to the bundle of trusted issuer certificates. This is used for validating each certificate after issuance or renewal. Specifying an empty value skips certificate validation. Default: /usr/share/lacme/ca-certificates.crt. - *hash* Message digest to sign the Certificate Signing Request with, overriding the [req(1ssl)](/req/1ssl.md) default. - *keyUsage* Comma-separated list of Key Usages, for instance digitalSignature, keyEncipherment, to include in the Certificate Signing Request. See [x509v3\_config(5ssl)](/x509v3_config/5ssl.md) for a list of possible values. Note that the ACME server might override the value provided here. - *tlsfeature* Comma-separated list of TLS extension identifiers, such as status\_request for OCSP Must-Staple. See [x509v3\_config(5ssl)](/x509v3_config/5ssl.md) for a list of possible values. Note that the ACME server might override the value provided here. - *owner*, *chown* An optional username\[:groupname\] to chown the issued *certificate* and *certificate-chain* to. - *mode*, *chmod* An optional octal mode to chmod the issued *certificate* and *certificate-chain* to. By default the files are created with mode 0644 minus umask restrictions. - *notify* Command to pass the the system’s command shell (\`/bin/sh -c\`) after successful installation of the *certificate* and/or *certificate-chain*. ## %-SPECIFIERS Some CLI options and configuration settings are subject to %-expansion for the following specifiers. Check the documentation of each setting to see which ones are affected. | | | | --- | --- | | %C | /var/cache for the root user, and $XDG\_CACHE\_HOME for other users (or $HOME/.cache if the XDG\_CACHE\_HOME environment variable is unset or empty). | | %E | /etc for the root user, and $XDG\_CONFIG\_HOME for other users (or $HOME/.config if the XDG\_CONFIG\_HOME environment variable is unset or empty). | | %g | Current group name. | | %G | Current group ID. | | %h | Home directory of the current user. | | %t | /run for the root user, and $XDG\_RUNTIME\_DIR for other users. Non-root users may only use %t when the XDG\_RUNTIME\_DIR environment variable is set to a non-empty value. | | %T | $TMPDIR, or /tmp if the TMPDIR environment variable is unset or empty. | | %u | Current user name. | | %U | Current user ID. | | %% | A literal %. | ## EXAMPLES - ``` $ sudo lacme account --register --tos-agreed mailto:noreply@example.com $ sudo lacme newOrder $ sudo lacme revokeCert /path/to/service.crt ``` Automatic renewal can be scheduled via [crontab(5)](/crontab/5.md) or [systemd.timer(5)](/systemd.timer/5.md). In order to avoid deploying a single account key onto multiple nodes and/or dealing with multiple account keys, one can install a single [lacme-accountd(1)](/lacme-accountd/1.md) instance on a dedicated host, generate a single account key there (and keep it well), and set the following in the \[accountd\] section: - ``` command = ssh -T lacme@account.example.net lacme-accountd ``` If the user running lacme can connect to lacme@account.example.net using (passwordless) key authentication, this setting will spawn a remote [lacme-accountd(1)](/lacme-accountd/1.md) and use it to sign ACME requests. Further hardening can be achieved by means of [authorized\_keys(5)](/authorized_keys/5.md) restrictions: - ``` restrict,from="...",command="/usr/bin/lacme-accountd --quiet --stdio" ssh-rsa ... ``` ## BUGS AND FEEDBACK Bugs or feature requests for lacme should be filed with the Debian project’s bug tracker at \. ## SEE ALSO [lacme-accountd(1)](/lacme-accountd/1.md) ## AUTHORS Guilhem Moulin (mailto:guilhem@fripost.org).