[Help wanted] FastCGI with kfcgi on macOS

[nalzok]

I need some help using FastCGI with kfcgi on macOS. By now I've built the executable, but I have no idea how to configure the server.

Actually I don't even know which server I'm using! macOS ships with a built-in server, but I'm not sure whether it's Apache or httpd, since both names seem to refer to the same thing.

~|⇒ apachectl -v
Server version: Apache/2.4.33 (Unix)
Server built:   Apr  3 2018 18:00:56
~|⇒ httpd -v
Server version: Apache/2.4.33 (Unix)
Server built:   Apr  3 2018 18:00:56

Anyway, I followed your tutorial on working with httpd, but the server complains about a syntax error when I added the server "me.local" command into the configuration file /etc/apache2/httpd.conf.

~|⇒ apachectl -t
AH00526: Syntax error on line 564 of /private/etc/apache2/httpd.conf:
Invalid command 'server', perhaps misspelled or defined by a module not included in the server configuration

I tried consulting the document but was soon overwhelmed by the huge amount of info: which module should I use, mod_fastcgi, mod_fcgid, or mod_proxy_fcgi? It would be great if you could provide an example, since most people don't have a machine running OpenBSD by their hand (remote servers are an option, but the connections are usually quite slow!)

[kristapsdz]

The tutorial mentioned is for OpenBSD's httpd. I don't have any information on Mac OS X's Apache. You might want to start by searching for running CGI scripts on Mac OS X, then FastCGI---which will be much more complicated. kcgi's FastCGI scripts should work with kfcgi or the default Apache runner.

[nalzok]

I've managed to use this library with CGI on macOS, which is quite straightforward with your detailed tutorial, but working with FastCGI is indeed much harder!

I'll update this thread if I can get it to work.

[nalzok]

I don't know it's a good news or a bad one. Either way, I believe I've configured NGINX on macOS to work with the FastCGI protocol, but the result is a kernel panic. (Edit: you can fix this by passing -v to kfcgi, the reason behind this is very likely a macOS bug)

First, you need to build and install the application:

cc -I/usr/local/include -c -o fastcgi-app.o main.c
cc -L/usr/local/lib -o fastcgi-app fastcgi-app.o -lkcgi -lz
sudo mkdir -p /var/www
sudo install -m 0555 fastcgi-app /var/www

Note that I dropped -static, because it's not supported on macOS. As a workaround, we're going to copy all the dynamic libraries over to get the executable to work inside the file-system jail:

sudo mkdir -p /var/www/bin /var/www/usr/lib/system
sudo cp /bin/* /var/www/bin
sudo cp -R /usr/lib/* /var/www/usr/lib
sudo cp -R /usr/lib/system/* /var/www/usr/lib/system

Next, install NGINX with brew install nginx and edit /usr/local/etc/nginx/nginx.conf to add the following server configuration:

server {
    listen       8080;
    server_name  localhost;

    location / {
        fastcgi_pass unix:/var/www/run/httpd.sock;
    }
}

Now you can start NGINX by simply typing nginx into the terminal. The last step is to start the kfcgi FastCGI server:

sudo kfcgi -U `whoami` -u `whoami` -- /var/www/fastcgi-app

Nonetheless, as mentioned before, I got a kernel panic when visiting localhost:8080, which I presume as the result of my correct configuration. Correct me if I'm wrong, but now I think the bug mentioned in #39 wasn't triggered by the regress suite.

In this case, the application I used is the minimal example provided by your tutorial:

#include <sys/types.h> /* size_t, ssize_t */
#include <stdarg.h> /* va_list */
#include <stddef.h> /* NULL */
#include <stdint.h> /* int64_t */
#include <kcgi.h>

int
main(void)
{
  struct kreq req;
  struct kfcgi *fcgi;

  if (KCGI_OK != khttp_fcgi_init
     (&fcgi, NULL, 0, NULL, 0, 0))
    return 0;

  while (KCGI_OK == khttp_fcgi_parse(fcgi, &req)) {
    khttp_head(&req, kresps[KRESP_STATUS], 
      "%s", khttps[KHTTP_200]);
    khttp_head(&req, kresps[KRESP_CONTENT_TYPE], 
      "%s", kmimetypes[KMIME_TEXT_PLAIN]);
    khttp_body(&req);
    khttp_puts(&req, "Hello, world!\n");
    khttp_free(&req);
  }

  khttp_fcgi_free(fcgi);
  return 0;
}

When I run /var/www/fastcgi-app directly on the command line, it just hang up without causing a kernel failure, so I suspect that the offending line lies in khttp_fcgi_parse.

[kristapsdz]

Great job! I don't think it's worth digging around on this more: obviously there are some show-stopping bugs in Mac OS X. Thank you so much for spending the time to uncover these! I'll definitely take Apple off the list of supported systems.

[nalzok]

No problem, and you've also done a great job!

While it's regrettable to hear that you're going to drop support for macOS, I would say you've made a sensible decision, for it really doesn't qualify for a web server, at least not in the near future.

[kristapsdz]

I'll leave support enabled in case it's fixed, but just put up a PSA on the kcgi site that it might crash and shouldn't be trusted. You can always try basic CGI scripts---but first see if something like the abort test case, where a validator abort()s, crashes the system as it did in the regression suite; and if it does, just... make sure your systems never abort. :( Either way, you get full credit for this discovery. Thank you so much for your research!

As for FastCGI, variable mode (-r) might make a difference, but I doubt it. My uninformed guess is that Mac pukes because of something regarding socketpair IPC.

[nalzok]

You're welcome :)

Yeah I have no problems playing with CGI, not counting the test-abort-validator case. When it comes to FastCGI, I just tried variable mode, and it works on my system!!! You may want to include this piece of information into the PSA.

~|⇒ sudo kfcgi -r -p / -U `whoami` -u `whoami` -- /var/www/fastcgi-minimal
Password:
~|⇒ nginx
~|⇒ curl -i localhost:8080
HTTP/1.1 200 OK
Server: nginx/1.15.0
Date: Thu, 14 Jun 2018 16:55:18 GMT
Content-Type: text/plain
Transfer-Encoding: chunked
Connection: keep-alive

Hello, world!

PS: just a quick question, what does the -- do in the call to kfcgi? Everything seems to work well after I drop it, i.e.

~|⇒ sudo kfcgi -r -p / -U `whoami` -u `whoami` /var/www/fastcgi-minimal

(I'm reopening this issue because it appears that you won't receive a notification when I comment under a closed issue.)

[kristapsdz]

The -- indicates an end to optional arguments. See getopt(1) for details. Thank you again!