If you, like me, use MacOS and Homebrew, you may have had some trouble configuring Ruby from source - and maybe even more if you don't use Homebrew. You may also have gotten some odd error messages when you tried. I had some trouble on El Capitan, but a quick Google search will find many weird errors with OpenSSL and Ruby over many years and many versions. RVM goes so far as to download its own OpenSSL and link against it when it builds.
Of course, that doesn't help you if you're building from source, without using RVM.
How Do You Check?
First off, let's talk about how you see if you have openssl working. You *can* run "make check" in your Ruby source directory, but that's quite slow. Better is to start up irb and require "openssl". If Ruby can't find it, that means it didn't get built -- or your path is wrong. You can require something else to make sure it's not a path problem.
$ irb 2.3.1 :001 > require "tsort" => true 2.3.1 :002 > require "openssl" => true
(I required "tsort" just as a way of showing that, yes, my standard Ruby libraries were available.)
You can also cut that down to a one-liner by having Ruby evaluate code from the command line:
$ ruby -r openssl -e 'print "Working\n"' Working $
Okay, maybe I just really like one-liners :-)
What If It Doesn't Work?
Extensions don't always rebuild properly if Ruby can't detect the libraries. Specifically, configure doesn't always seem to figure out when it's been looking in the wrong place. So just re-making will often not rebuild Ruby's OpenSSL extension properly if it didn't get detected right the first time. This will manifest as a C error about incompatible prototypes for HMAC_CTX_copy, a function you've rightly never heard of and don't care about. That's because Ruby is using a very old, slightly wrong version of this function in its chunk of "you don't have OpenSSL" stub code.
You can track this down to a few old commits in 2008 (commit a8a111 in Ruby GitHub, and commit 87d524 in OpenSSL, not that I checked or anything.) But if you're getting prototypes not matching on HMAC_CTX_copy, it's because Ruby has the OpenSSL extension half-configured. Kill it with fire. If you're cloned from the Ruby GitHub repo, that looks like this in your Ruby source directory:
git clean -dxf
That first incantation, "git clean -dxf" means "destroy every file that wouldn't be there after a new clean git checkout." Even stuff in .gitignore. If Git didn't put it there, destroy it. If you wonder if your local Ruby checkout might be in an inconsistent state, I recommend that command highly. Of course, you'll also wait quite awhile for everything to be configured and built.
However, that will make sure you're seeing the OpenSSL that's actually available on your system instead of one that configure saw and cached several versions ago.
(Is it a problem that Ruby has some of the wrong prototypes for OpenSSL functions in its "you don't have OpenSSL" stub? Not really. They're very close. And you'll only see the compiler complain if you pull in both sets, which is an error, and a sign that things are already wrong. It's actually kind of nice, because you never wind up with a compiled-but-half-functioning Ruby with part stubs and part real OpenSSL.)
Any Hints on Why?
OpenSSL is one of a number of Ruby "extensions" which get compiled along with your Ruby. Ruby will try to build them, but may not if it can't find needed libraries, or if something fails when Ruby tries to compile it.
These extensions live in your Ruby source tree under the "ext" directory:
There may be a "mkmf.log" directory in any of them -- especially if something failed to build. You can see how the extensions above may not be around if something they need isn't there (Win32ole on a Mac, say, or zlib or openssl on a computer without those libraries installed.)
If you're basically C-literate, the mkmf.log file may be able to tell you that it can't find the library, or that there's an incompatibility. May I recommend not digging too deep in those cases unless you know OpenSSL quite well? That way, madness lies. Still, opening up mkmf.log and reading the last few entries can sometimes be quite useful ("wait, it's finding what version of OpenSSL? In what directory? Why is that there?")
It's possible to rebuild just the OpenSSL extension instead of all of Ruby as a way to see if you got the configuration right. I recommend not doing that. It's easy to wind up with a half-configured setup, some stuff cached by configure and passed in, and otherwise something that only sort-of works, and which you'll never be able to replicate if you ever need to build Ruby again. When possible, build clean and from the top level, even if it's slower, so that you'll be able to do it again later if you need to.
Homebrew? From Source?
I did a fair bit of uninstalling and reinstalling openssl in Homebrew, and from source. As it turns out, that wasn't my problem here. But in case you need it:
$ brew uninstall openssl # And in the OpenSSL source directory: ./config --prefix=/usr/local --openssldir=/usr/local/openssl ./Configure darwin64-x86_64-cc make depend make make test make install cd /usr/local/include && ln -s /usr/local/ssl/include/openssl .
What If It Still Doesn't Work?
Ruby can be picky on a Mac about picking up OpenSSL, which uses a slightly funky directory structure for a library anyway. I tried a bunch of things with setting LIBS when configuring, to no avail.
It turns out there's a utility already on your Mac that Ruby will use and that specializes in this sort of thing: pkg-config.
There's a nice blog post that explains how this works, but the sort answer looks like this:
By telling pkg-config exactly where to find OpenSSL and to look there first, Ruby finds it, and everything works... Almost.
You should put that in your ~/.bashrc file, so that it always happens. That way, next time you build Ruby it will just "magically work," instead of you having to remember where you read this blog post.
And When My Tests Fail?
All of that gets you almost all the way there. But when you run all the Ruby tests, such as with "make check", four will fail with timeouts on incoming network connections. And, if you're lucky, you'll get a little pop-up window telling you that Mac OS isn't so sure that your process should just get to open incoming sockets. Security!
Mac comes with something called Mac Application Firewall, which will cause some of Ruby's OpenSSL tests to fail, if you have it on.
Short answer: go to the "Security and Privacy" control panel, to the "Firewall" tab, and turn it off. You'll need to open the little lock icon at the bottom to make changes, just like always.
However, now it should be working!
What If It's Still Not Working?
I can only tell you what worked for me. But here are a few more possibilities that didn't help me, but might help you.
You can uninstall and reinstall OpenSSL via Homebrew. This will help if your version is damaged.
You can install a new OpenSSL from source, with the commands above. This will help if you're using the wrong version.
You can install Ruby via RVM. Remember that "rvm install ruby-head" will grab the latest, so you're not limited to released, stable versions. RVM has a lot of workarounds to get Ruby compiled with OpenSSL and downloads and configures its own, so it's often the easiest. Also, even if your local system OpenSSL is broken somehow, RVM won't be using it, so that may be a workaround for that problem. Ruby-build can also work for this.
You can install OpenSSL to a different directory. In the "configure OpenSSL from source" commands above, I put it under /usr/local. But you can put it directly under /usr, for instance, or otherwise try a place that might be easier to find.
If you can, install via RVM or ruby-build to avoid doing this yourself.
If you need latest source, but not often, still use rvm or ruby-build.
If you need to build locally, have pkg-config do the configuration, don't do it yourself.
If you still have to configure it yourself, make sure to "git clean -dxf" to avoid even the slightest chance of a half-cached older configuration.
If you'll need to build Ruby again, put the "export PKG_CONFIG_PATH=/usr/local/opt/openssl/lib/pkgconfig:/usr/local/lib/pkgconfig" into your ~/.bashrc file so it happens always, not just this one time.
In short, Ruby's code is part of the C ecosystem, with all the usual library-based problems that entails. If somebody else can do part of the configuration work for you, please let them :-)