curl, Let's Encrypt and Apple laziness

The built-in version of curl on any Power Mac version of OS X will not be capable of TLS 1.1 or higher, so most of you who need it will have already upgraded to an equivalent with MacPorts. However, even for later Intel Macs that are ostensibly supported -- including my now legacy MacBook Air with Mojave I keep around for running 32-bit Intel -- the expiration of one of Let's Encrypt's root certificates yesterday will suddenly mean curl may suddenly cease connecting to TLS sites with Let's Encrypt certificates. Yesterday I was trying to connect to one of my own Floodgap sites, unexpectedly got certificate errors I wasn't seeing in TenFourFox or mainline Firefox, and, after a moment of panic, suddenly realized what had happened. While you can use -k to ignore the error, that basically defeats the entire idea of having a certificate to start with.

The real hell of it is that Mojave 10.14 is still technically supported by Apple, and you would think updating the curl root certificate store would be an intrinsic part of security updates, but you'd be wrong. The issue with old roots even affects Safari on some Monterey betas, making the best explanation more Apple laziness than benign neglect. Firefox added this root ages ago and so did TenFourFox.

If you are using MacPorts curl, which is (IMHO) the best solution on Power Macs due to Ken's diligence but is still a dandy alternative to Homebrew on Intel Macs, the easiest solution is to ensure curl-ca-bundle is up-to-date. Homebrew (and I presume Tigerbrew, for 10.4) can do brew install curl-ca-bundle, assuming your installation is current.

However, I use the built-in curl on the Mojave MacBook Air. Ordinarily I would just do an in-place update of the root certificate bundle, as I did on my 10.4 G5 before I started using a self-built curl, but thanks to System Integrity Protection you're not allowed to do that anymore even as root. Happily, the cURL maintainers themselves have a downloadable root certificate store which is periodically refreshed. Download that, put it somewhere in your home directory, and in your .login or .profile or whatever, set CURL_CA_BUNDLE to its location (on my system, I have a ~/bin directory, so I put it there and set it to /Users/yourname/bin/cacert.pem).