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Crypt::LE - Let's Encrypt / Buypass / ZeroSSL and other ACME-servers client and library in Perl for obtaining free SSL certificates (inc. generating RSA/ECC keys and CSRs). HTTP/DNS verification is supported out of the box, EAB (External Account Binding) supported, easily extended with plugins, easily dockerized.



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This module provides the functionality necessary to use Let's Encrypt API and generate free SSL certificates for your domains. It can also be used to generate private RSA/ECC keys and Certificate Signing Requests without resorting to openssl command line. Crypt::LE is shipped with a self-sufficient client for obtaining SSL certificates -

New v0.39 release is available. This introduces some new features, such as:

  • EAB (External Account Binding) support used by some CAs (via eab-kid and eab-hmac-key parameters).
  • Asynchronous order finalization support, which awaits for order completion respecting the retry intervals indicated by the CA.
  • Direct support of known ACME-compatible CAs via ca parameter, so you do not need to remember which URL some specific CA is using.

Such directly supported CAs are:,,,, You do not need to know or specify the URLs for those - only their name in the ca parameter. See the examples of using different CAs in the Other certificate providers and custom ACME servers section below.

Any other ACME-compatible CA can also be used by specifying the URL for its directory in the directory parameter.

Both ACME v1 and ACME v2 protocols and wildcard certificate issuance are supported.

Please note that ACME v1 is being deprecated by Let's Encrypt and, starting from version 0.34 of the client, the default version selected is ACME v2 (unless you have specified the version explicitly using --api option or specified a custom server using --server option - in the latter case the client will use auto-sensing to select appropriate protocol version).


  • The code has been successfully tested on more than 500 combinations of OS and Perl versions. It should install and run fine on Linux, FreeBSD, NetBSD, etc. It also works on Mac OS X and Windows (tested with ActiveState and Strawberry Perl).

  • If you are a Windows user, you can download portable Win32/Win64 binaries (they work even on Windows XP and require NO installation).

  • In addition, you can use the latest Docker Image (lightweight non-root container).

Table of Contents


For Linux

With Linux systems there are just 3 essential things which should be in place for the package to be successfully installed: "gcc", "make" and the SSL development package (usually either "libssl-dev" or "openssl-devel"). You can install those as shown below - note that your server may already have them, so you might just try installing the client/library itself.

  • For CentOS minimal installation: sudo yum install gcc openssl-devel

  • For Debian/Ubuntu server installation: sudo apt-get install make gcc libssl-dev

For Windows

With Windows there are no specific requirements at all and you don't have to install anything if you want to use Windows binaries - self-sufficient and portable. Otherwise you just need to install Perl (see below).

If you use Strawberry Perl, then CPANminus will be already pre-installed and you will only need to instatll Crypt::LE itself. It is enough to download the portable version of Strawberry Perl for your platform (64bit or less likely 32bit). Then just unzip it to the directory of your choice (say C:\Perl64) and use "cpanm" to install Crypt::LE.

If you use ActiveState Perl, then after installing the Perl itself, you will need to install App-cpanminus (using 'ppm' - Perl Package Manager). Note that for business license users ActiveState offers more ppm packages (including Crypt-LE), so it could then be installed directly, without the need to install App-cpanminus.


The installation is quite easy and straightforward. The provided client does not need any specific privileges (certainly does not need to be run as a root or any privileged user). Keep in mind that the client functionality can be extended with plugins, so make sure you have read the Plugins section and especially Plugins in multiuser environment notes.

For Windows you can just download and unzip the latest release of the client - you do not have to install anything, even if you intend to use custom Perl plugins. You would only need to install the Crypt::LE library on Windows if you intend to use it with your own client (or the custom version of For more details, checksum files and a 32bit client please see the releases page.

With CPANminus

cpanm Crypt::LE


cpan -i Crypt::LE

Manual installation

perl Makefile.PL
make test
make install

Windows installation (if you do not want to use the binaries)

cpanm -f Log::Log4perl
cpanm Crypt::LE

Note: there might be some rare cases where installation fails on Linux - for example on a freshly installed Debian 10 (buster) you may see an error for Net::SSLeay. This can be fixed by running sudo apt-get install libnet-ssleay-perl.



With you should be able to quickly get your SSL certificates issued. Run it without parameters to see how it is used or with --help for an extended help and examples. The client supports 'http' and 'dns' challenges out of the box.

Important: By default all your actions are run against the test server, which behaves exactly as the live one, but produces certificates not trusted by the browsers. Once you have tested the process and want to get an actual trusted certificate, always append --live parameter to the command line.

Quick start on Windows

Download and unzip the latest release of the client for Windows, then run the client and follow the instructions (replace with your domain):

le64.exe -email "" -key account.key -csr domain.csr -csr-key domain.key -crt domain.crt -domains "," -generate-missing -live

Quick start on Linux/Mac

Install the client using one of the methods described (usually cpan -i Crypt::LE should be sufficient), then run the client and follow the instructions (replace with your domain): -email "" -key account.key -csr domain.csr -csr-key domain.key -crt domain.crt -domains "," -generate-missing -live

Usage examples

Interactive certificate issuance: --key account.key --email "my@email.address" --csr domain.csr --csr-key domain.key --crt domain.crt --domains  "www.domain.ext,domain.ext" --generate-missing

That will generate an account key and a CSR if they are missing. If any of those files exists, they will just be loaded, so it is safe to re-run the client.

Please note that --email parameter is only used for the initial registration. To update it later you can use --update-contacts option. Even though it is optional, you may want to have your email registered to receive certificate expiration notifications.

To use HTTP verification and have challenge files created/removed automatically, you can use --path and --unlink parameters: --key account.key --email "my@email.address" --csr domain.csr --csr-key domain.key --crt domain.crt --domains "www.domain.ext,domain.ext" --generate-missing --unlink --path /some/path/.well-known/acme-challenge

If www.domain.ext and domain.ext use different "webroots", you can specify those in --path parameter, as a comma-separated list as follows: --key account.key --email "my@email.address" --csr domain.csr --csr-key domain.key --crt domain.crt --domains "www.domain.ext,domain.ext" --generate-missing --unlink --path /a/.well-known/acme-challenge,/b/.well-known/acme-challenge

Please note that with multiple webroots specified, the amount of those should match the amount of domains listed. They will be used in the same order as the domains given and all of those folders should be writable.

To use DNS verification of domain ownership, you can use --handle-as parameter: ... --handle-as dns

For more examples, logging configuration and all available parameters overview use --help: --help

Two step flow

If you want to run the process in two steps (accept a challenge and then continue after running some other process), you can use --delayed flag. That flag interrupts the process once the challenge is received and appropriate information about what is required is printed or logged.

Once you have fulfilled the requirements (by either creating a verification file or a DNS record), you can re-run the process with exactly the same parameters, BUT without --delayed option.

Other certificate providers and custom ACME servers

By default the client uses Let's Encrypt CA (Certificate Authority) to get SSL certificates. However, you can also use it with other ACME-compatible servers. Please note that those might have different limitations or requirements - for example, ZeroSSL does not have the staging/testing environment, and it also uses so-called EAB (External Account BInding), so you will need to use 2 parameters retrieved from the Developer's section of your ZeroSSL account - eab-kid and eab-hmac-key, and use those for your command. Another CA, such as Bypass, does have a testing environment, and it does not use EAB, but requires for the email address to be specified. It also does not support more than 5 domains on one certificate and does not support wildcards.

Some examples:
  1. Using ZeroSSL, providing the server parameter explicitly (to be deprecated), and providing eab-kid and eab-hmac-key: --csr domain.csr --csr-key domain.key --domains "some.domain.tld" --crt domain.crt --generate-missing --server --eab-kid ... --eab-hmac-key ... --key my.key

  1. Using ZeroSSL, providing the directory parameter explicitly, and providing eab-kid and eab-hmac-key: --csr domain.csr --csr-key domain.key --domains "some.domain.tld" --crt domain.crt --generate-missing --directory --eab-kid ... --eab-hmac-key ... --key my.key

  1. Using ZeroSSL, providing the ca parameter, and providing eab-kid and eab-hmac-key: --csr domain.csr --csr-key domain.key --domains "some.domain.tld" --crt domain.crt --generate-missing --ca --eab-kid ... --eab-hmac-key ... --key my.key --live

(notice the --live parameter in this case - that is because there is no staging environment, so running the command without --live would produce an error "CA does not support staging environment, please specify 'live' explicitly.")

  1. Using (staging environment): --csr domain.csr --csr-key domain.key --domains "some.domain.tld" --crt domain.crt --generate-missing --ca --key my.key --email "admin@domain.tld"

(notice that email parameter is mandatory for this CA, and without it you would get an error "Email is a required contact")

  1. Using (production environment): --csr domain.csr --csr-key domain.key --domains "some.domain.tld" --crt domain.crt --generate-missing --ca --key my.key --email "admin@domain.tld" --live

(notice that email parameter is mandatory for this CA, and without it you would get an error "Email is a required contact")

The CAs which are directly supported by name are currently these:,,,,

If CA is ACME-compatible, but not listed above, it would still be supported as long as you know the correct directory URL to specify via a directory parameter - for example, Digicert is supported, but you would need to get a unique directory URL along with the values for the eab-kid and eab-hmac-key parameters.


Everything described above for the Perl client is applicable to the Windows client, which you can download from the Releases page. The only difference is that you will be running either le32.exe or le64.exe (depending on your platform) instead of There is one thing though you need to take into account when you are specifying the --path to store verification files for the HTTP verification on Windows:

You should NOT use a single backslash before the closing quote (if you had path quoted) - you need to either use a double-backslash or none at all. This is specific to Windows environment. To illustrate:

  • --path C:\Directory - right
  • --path C:\Directory\ - right
  • --path "C:\Directory" - right
  • --path "C:\\Directory\\" - right
  • --path "C:\Directory\\" - right
  • --path "C:\Directory\" - wrong

You can also use a forward slash (/) if you like.


To issue a wildcard certificate, use DNS verification and specify the domain in the following format: *.some.domain. ... --domains "*.some.domain" --handle-as dns

Please note that at the moment wildcards are only supported by the v2.0 of the API and they can only be issued if DNS verification is used.

Important - if you are issuing a wildcard certificate and also want a so-called "naked domain" ("some.domain") to be covered, list both of those names in the domains parameter. You will then need to create two TXT records with identical names but different values - this is normal and this is how you should create them. ... --domains "*.some.domain, some.domain" --handle-as dns


Windows binaries include export functions into PFX/P12 format, which is normally required by IIS. The export (in addition to saving certificates in PEM format) can be activated by specifying a PFX password with --export-pfx option. ... --export-pfx "mypassword"

Note: This fuction does NOT require OpenSSL or any PFX conversion tools to be installed on your machine - it is supported internally by the client.

By default, exported PFX file will be seen as "Crypt::LE exported" under the "Friendly Name" column of the Certificate Management Console. If you want to specify your own arbitrary string instead, use --tag-pfx parameter. ... --export-pfx "mypassword" --tag-pfx "My own Friendly Name"

NB: If you are receiving an error mentioning PKCS12 during an attempt to export to PFX, please ensure that the domain key which you have specified with --csr-key option is indeed a private key in PEM format (with -----BEGIN and -----END lines around it). If it is a key exported via MMC in Windows for example, you may need to export the key and remove the passphrase from it before it can be used, for example as mentioned in this guide. If the key has been generated by the client itself, you should see no errors, as it is already in the expected format.


If you are using IDN (Internationalized Domain Names) and generating a certificate for those, you can either encode those into "punycode" form by yourself, or let the client do that for you. Please note that for the conversion to work properly you need to have correct locale settings on your system. For Linux-based systems you can check that with the "locale" command, for Windows make sure that "System locale" in the Control Panel is set correctly.


Some ACME-compatible Certificate Authorities manage their accounts differently from how ACME accounts are normally created, but link those to an ACME account through so-called External Account Binding. In essence, you would need to get 2 additional parameters from those CAs and use those on the command line. Those parameters are the "Key ID" (eab-kid) and "HMAC Key" (eab-hmac-key).

Please note that the same EAB credentials, depending on the CA, might be allowed to be used for multiple ACME accounts or just one.


Let's Encrypt recently started offering "alternative" certificates via the "alternate links" mechanism. When your certificate is requested, LE returns just one such link at the moment of writing, where an intemediate certificate is signed by "ISRG Root X1, Internet Security Research Group" rather than "DST Root CA X3, Digital Signature Trust Co.". You can fetch that alternative certificate instead of the "default" one using the --alternative option with a number corresponding to the order in which that alternative certificate was listed. So for the first alternative certificate it will be: ... --alternative 1


To RENEW your existing certificate use the same command line as you used for issuing the certificate, with one additional parameter:

   --renew XX, where XX is the number of days left until certificate expiration.

If client detects that it is XX or fewer days left until certificate expiration, then (and only then) the renewal process will be run, so the script can be safely put into crontab to run on a daily basis if needed.

The amount of days left is checked by either of two methods:

  • If the certificate (which name is used with --crt parameter) is available locally, then it will be loaded and checked.
  • If the certificate is not available locally (for example if you moved it to another server), then an attempt to connect to the domains listed in --domains or CSR will be made until the first successful response is received. The peer certificate will be then checked for expiration.


If you would like to receive expiration notifications for your domain, you can specify --email parameter and an appropriate email address during the initial registration of the account. Later, shall you want to change your email or specify more than one, you can use --update-contacts parameter to update your contact information. For example: --key account.key --update-contacts "one@email.address, another@email.address" --live

To reset your contact details, please specify "none" as a value, as follows: --key account.key --update-contacts "none" --live


Both the library and the client can be easily extended with custom plugins to handle Let's Encrypt challenges (both pre- and post-verification). See Crypt::LE::Challenge::Simple module as an example of such plugin.

The client application can also be easily extended with modules handling process completion. See Crypt::LE::Complete::Simple module as an example of such plugin.

Client options related to plugins are:

  • --handle-with
  • --handle-params
  • --handle-as
  • --complete-with
  • --complete-params

Please note that parameters for --handle-params and --complete-params are expected to be valid JSON documents or to point to files containing valid JSON documents (the latter is a preferable method).

Example of running the client with plugins (you can modify the source code of the provided Crypt::LE::Challenge::Simple and Crypt::LE::Complete::Simple): --key account.key --email "my@email.address" --csr domain.csr --csr-key domain.key --crt domain.crt --domains "www.domain.ext,domain.ext" --generate-missing --handle-with Crypt::LE::Challenge::Simple --complete-with Crypt::LE::Complete::Simple

Note: you can use the same plugin to cover both the challenge/verification and the completion process, as long as it has appropriately named methods defined. You can also point directly to a Perl module file rather than specify a name of the module.

This will work even on Windows, without any need to install anything - having just the binary file of the client and the plugin file is sufficient.

For example, if you have your le64.exe client and then created or downloaded the plugin code (see Plugins/ for example) into the same directory, you can use it like this:

le64.exe -key account.key -domains -csr test.csr -csr-key test.key -crt test.crt -generate-missing -handle-with -handle-as dns

All comand line parameters are passed to the methods of the plugin, along with the information about the challenge requirements and the verification results. For example, if you have defined handle_challenge_dns method, it will receive the challenge data and the parameters data. The challenge data will contain all the necessary details, including "domain", "host" and "record" values. In this case the "host" would be the same as the "domain", except the wildcard part removed (if it was present). To illustrate:

  • If the "domain" is, then the "host" is;
  • If the "domain is "*", then the "host" is;

So you would need to set _acme-challenge record in your "host" zone with the value of the "record".

In a similar way, for the HTTP verification, the method handle_challenge_http would have access to "file", which contains the name of the file to be created, and the "text", which contains the content of that file.

Please note that before v0.32 the parameters passed with --handle-params and --complete-params were accessible directly as keys of the parameters passed to the method. However, starting from v0.32 they are passed under their own key along with all the command line parameters. So if you have passed something like { "name": 123 } as JSON for --handle-params, then previously in your methos you would access that "name" as follows:

my $value = $params->{'name'};

Now you need to access it as follows:

my $value = $params->{'handle-params'}->{'name'};

This is a potentially breaking change if you used custom handlers and were passing additional custom parameters from the command line of the client, but it is necessary to make all command line parameters accessible to plugins and avoid overlapping the keys.

Plugins in multiuser environment

It is important to remember that the client code allows plugins to be used. While this makes the client rather flexible in terms of possible automation, it should be kept in mind that you should not be running it from a privileged user (and you do not need to), especially in the multiuser environment. As with any other application that can extend the functionality either by plugins or by executing some commands/hooks, it is never a good idea to make it writable by anyone else or make it run with the privileges it does not actually need. You can almost always achieve the resuts you need without resorting to making your application (or the script that runs it) running as a root or a privileged user - for example to allow reloading the web server on completion you can just configure sudo to allow that reload to a specific user, etc.


Client uses Log::Log4perl module for logging. You can easily configure it to log into file, database, syslog, etc. Logger object is available to plugins which are called from the client and to the library itself. Below is an example of a logging configuration file to log both to screen and into le.log file:

 log4perl.rootLogger=DEBUG, File, Screen
 log4perl.appender.File = Log::Log4perl::Appender::File
 log4perl.appender.File.filename = le.log
 log4perl.appender.File.mode = append
 log4perl.appender.File.layout = PatternLayout
 log4perl.appender.File.layout.ConversionPattern = %d [%p] %m%n
 log4perl.appender.File.utf8 = 1
 log4perl.appender.Screen = Log::Log4perl::Appender::Screen
 log4perl.appender.Screen.layout = PatternLayout
 log4perl.appender.Screen.layout.ConversionPattern = %d [%p] %m%n
 log4perl.appender.Screen.utf8 = 1

Save the configuration into some file and then run with --log-config parameter specifying that configuration file name, for those settings to take effect.


By default the client application produces a limited set of exit codes - 1 on help or unknown parameters and 255 in case of other errors. Additionally the case of attempting a renewal too early is not considered an error. This behaviour can be changed to assign custom exit codes to different errors (including setting an error code for an early renewal).

If you wish to change an exit code for a particular error, you need to find the associated message first and then assign some code via a config file. For example, say you are receiving an error message saying "Could not read the certificate file." and you want to assign an error code of 200 to it. If you you add --debug flag to the command line, that same error message would look as "[ CERTIFICATE_FILE_READ ] Could not read the certificate file." If now you create a configuration file as shown below, running the same command as before with --config name_of_your_configuration_file will change the exit code for that error to 200:



In the rare case of connecting through a proxy, you can instruct the client to use one by setting HTTPS_PROXY environment variable in the form of (user:pass@ part is only needed if proxy requires basic auth).


After installing, you can find documentation for this module with the perldoc command.

perldoc Crypt::LE

You can also look for information at:

For feedback see:


Crypt::LE has been initially created over weekend, when I noticed that some of my previously bought certificates are about to expire soon enough. The initial goal was to make this work, make it easy to use and possibly remove the need to use openssl command line. It may contain some (hopefully minor) bugs, so feel free to submit a bug report.

If you'd like to contribute a custom plugin, for example to support automatic DNS records creation and removal via API of certain DNS providers (or your registrar), feel free to create a module under Crypt::LE::Challenge:: namespace and either upload it to CPAN or submit a pull request.

In the former case please specify a dependency from Crypt::LE of at least version 0.11 in your Makefile.

In the latter case please be aware that your module might be uploaded to CPAN later (unless you object) and might be uploaded separately rather than as a part of Crypt::LE (this might happen if you are using dependencies not necessarily required for the rest of Crypt::LE package).

You can also contribute the completion-handling modules under Crypt::LE::Complete:: namespace, for example to scp the domain key and certificate to another host or to send an email about successful certificate renewal.

Copyright (C) 2016-2023 Alexander Yezhov

This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). You may obtain a copy of the full license at:

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