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Attention acme-client-portable is no longer maintained. Since acme-client made its way into OpenBSD, I've only been using the base version.

So if you're using this client, you're using old code! If you want to use the current version of acme-client, you'll need to use OpenBSD. Which I recommend doing anyway, of course.

If you can't use OpenBSD, it's not a difficult challenge to port the OpenBSD acme-client to your operating system. However, be aware that it won't share the security mechanisms available to the downstream code. Regardless, if anybody would like to take a stab at this, I'd be happy to review your work!

I suggest grabbing a copy of the OpenBSD version and setting up an oconfigure scaffold around the code. This will give you all of the usual string functions that might not be available. Next, you'll need to add in your system's sandbox mechanisms. This will require your own code. You can use the existing portability shim as a guide. Good luck!


acme-client-portable is yet another ACME client, specifically for Let's Encrypt, but one with a strong focus on security.

It was named letskencrypt-portable until version 0.1.11.

Please see for stable releases: this repository is for current development of the portable branch, which tracks acme-client with goop to allow compilation and secure operation on Linux, Mac OS X, NetBSD, and FreeBSD (hence "-portable"). You will need libressl on all systems and libbsd on Linux (except for musl libc systems like Alpine).

Linux has an experimental libseccomp sandbox, but you must enable it yourself. Details in

This repository mirrors the master CVS repository: any source changes will occur on the master and be pushed periodically to GitHub. If you have bug reports or patches, either file them here or e-mail them to me. Feature requests will be ignored unless joined by a patch.

What are the difference between this and the non-portable release?

  • Conditional support for OpenBSD's sandbox, Mac OS X, or experimentally on Linux.
  • Proper preprocessor flags for unlocking some Linux functions.
  • Different library names on Linux.
  • Uses GNU make instead of BSD make.

This version tries its best to be secure, but some of its supported operating systems are hostile to security.

On both Linux and Mac OS X, for example, the DNS resolution process is effectively run in the main file-system and un-sandboxed due to the complexity of lookups (needing mDNSresponder in the latter case or a slew of mystery files in the former).

Moreover, while the sandbox on Mac OS X (which is deprecated?) exists, its behaviour is not well-documented and, morever, is weakened to co-exist with the file-system jail.

Feature requests will be ignored unless joined by a patch. If there's something you need, I'm happy to work with you to make it happen. If you really need it, I'm available for contract (contact me by e-mail).


Since your system might not be one of the tested ones (FreeBSD, Linux, Linux with musl libc, etc.), you may need to tune some of the values in the GNUmakefile or config.h. Please tell me if you do so, so I can accommodate in future releases.

In the former, you can adjust system-specific compilation flags.

In the latter, you can set the NOBODY_USER value to be the name of an unprivileged user for privilege dropping. You can also set DEFAULT_CA_FILE for the location of the certificate file loaded by libtls. There's also PATH_VAR_EMPTY, which should be an empty directory into which we can create our jail.


Sources use the ISC (like OpenBSD) license. See the file for details.

The jsmn.c and jsmn.h files use the MIT license. See for details.


portable version of acme-client, a secure ACME client







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