Knowing Kristaps, he probably considers strong privsep and privdrop basic functionality. That is after all why he developed acme-client in the first place; he acknowledged at the time the plethora of “lightweight” certbot alternatives but was more concerned with security architecture.
> That certainly isn't true of Chrome (I run it on non-OpenBSD and there are no functionality / security issues in doing so). That isn't true of OpenSSH, which also supports pledge() on OpenBSD and still is pretty secure on other OSes.
Chrome uses different techniques depending on the platform. On OpenBSD it uses pledge() and unveil(), while on Linux it uses seccomp. Kristaps isn’t a fan of seccomp’s complexity, as he mentions in the readme: “Linux's security facilities are a mess, and will take an expert hand to properly secure.” He’s not suggesting it can’t be done, and the Google Chrome team in particular has the kind of expertise he’s talking about.
For projects of less‐than‐Chrome scale, though, Kristaps feels that seccomp is too difficult: https://github.com/kristapsdz/acme-client-portable/blob/mast...
> And I am worried, in particular, that the author means that the validator is not very strong, and the bulk of the validation is that it unveils the filesystem to the files it's supposed to write to and then blindly trusts the input, on the grounds that the remote side could just have sent different files.
I don’t understand this interpretation. It’s not what I got from the readme at all. What kind of validation do you expect Kristaps to be overlooking?