External program

Since: v0.5.0 Solving the DNS-01 challenge using an external program.

  • Code: exec

Here is an example bash command using the External program provider:

EXEC_PATH=/the/path/to/myscript.sh \
lego --dns exec --domains my.domain.com --email my@email.com run

Base Configuration

Environment Variable Name Description
EXEC_MODE RAW, none
EXEC_PATH The path of the the external program.

Additional Configuration

Environment Variable Name Description
EXEC_POLLING_INTERVAL Time between DNS propagation check.
EXEC_PROPAGATION_TIMEOUT Maximum waiting time for DNS propagation.

Description

The file name of the external program is specified in the environment variable EXEC_PATH.

When it is run by lego, three command-line parameters are passed to it: The action (“present” or “cleanup”), the fully-qualified domain name and the value for the record.

For example, requesting a certificate for the domain ‘foo.example.com’ can be achieved by calling lego as follows:

EXEC_PATH=./update-dns.sh \
	lego --dns exec \
	--domains foo.example.com \
	--email invalid@example.com run

It will then call the program ‘./update-dns.sh’ with like this:

./update-dns.sh "present" "_acme-challenge.foo.example.com." "MsijOYZxqyjGnFGwhjrhfg-Xgbl5r68WPda0J9EgqqI"

The program then needs to make sure the record is inserted. When it returns an error via a non-zero exit code, lego aborts.

When the record is to be removed again, the program is called with the first command-line parameter set to cleanup instead of present.

If you want to use the raw domain, token, and keyAuth values with your program, you can set EXEC_MODE=RAW:

EXEC_MODE=RAW \
EXEC_PATH=./update-dns.sh \
	lego --dns exec \
	--domains foo.example.com \
	--email invalid@example.com run

It will then call the program ./update-dns.sh like this:

./update-dns.sh "present" "foo.example.com." "--" "some-token" "KxAy-J3NwUmg9ZQuM-gP_Mq1nStaYSaP9tYQs5_-YsE.ksT-qywTd8058G-SHHWA3RAN72Pr0yWtPYmmY5UBpQ8"

Commands

The -- is because the token MAY start with a -, and the called program may try and interpret a - as indicating a flag. In the case of urfave, which is commonly used, you can use the -- delimiter to specify the start of positional arguments, and handle such a string safely.

Present

Mode Command
default myprogram present -- <FQDN> <record>
RAW myprogram present -- <domain> <token> <key_auth>

Cleanup

Mode Command
default myprogram cleanup -- <FQDN> <record>
RAW myprogram cleanup -- <domain> <token> <key_auth>

Timeout

The command have to display propagation timeout and polling interval into Stdout.

The values must be formatted as JSON, and times are in seconds. Example: {"timeout": 30, "interval": 5}

If an error occurs or if the command is not provided: the default display propagation timeout and polling interval are used.

Mode Command
default myprogram timeout
RAW myprogram timeout