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SPNEGO For nginx - a start, at least

January 17th, 2010 Leave a comment Go to comments

I've been posting on the nginx mailing lists for a while that I've had a developer working on SPNEGO (Kerberos/GSSAPI/etc.) module for authentication for nginx. I never produced any code though, because I was constantly waiting for a bit more of a matured module before giving it out.

For now though, it might just be best to throw out there what I have, explain my findings, and let the community start testing it, hacking it, improving it, etc.


Opens for the developer still

  • He said he'd like to remove the dependency on the bundled spnegohelp library (apparently it's not needed or it can be filled with a system package)
  • Needs some more documentation

My questions, comments

  • Should it be called "mod_auth_sso" or something like "mod_auth_gssapi" - I believe Apache's equivalent has "gssapi" in the title somewhere. It was hard to determine which was the most up to date version - mod_auth_kerb, modgssapache, etc.
  • I cannot verify this still using my corporate domain setup. I did have to make a minor tweak in the source to change the principal name it was using (see below) and I still got access denied. I have no clue if the module is to blame, the machine's setup with the domain, or what.

A possible required tweak... around line 474 or so in ngx_http_auth_sso_module.c

- host_name = r->headers_in.host->value;
+ host_name = alcf->realm;

How to compile - yes, it's a bit messy, mainly due to the spnegohelp library dependency 🙂

wget http://sysoev.ru/nginx/nginx-0.8.31.tar.gz
tar xvfz nginx-0.8.31.tar.gz
cd nginx-0.8.31
./configure --conf-path=/etc/nginx/nginx.conf --prefix=/usr --user=www-data --group=www-data --error-log-path=/var/log/nginx/error.log --pid-path=/var/run/nginx.pid --lock-path=/var/lock/nginx.lock --http-log-path=/var/log/nginx/access.log --http-client-body-temp-path=/var/lib/nginx/body --http-proxy-temp-path=/var/lib/nginx/proxy --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --with-http_stub_status_module --with-http_gzip_static_module --without-mail_pop3_module --without-mail_smtp_module --without-mail_imap_module --with-http_flv_module --with-http_ssl_module --with-http_dav_module --with-http_realip_module --with-http_xslt_module --with-debug --add-module=/usr/src/build/ngx_http_auth_sso_module-current --with-ld-opt="-L/usr/src/build/ngx_http_auth_sso_module-current/spnegohelp"
cp -f /usr/src/build/ngx_http_auth_sso_module-0.3/spnegohelp/libspnegohelp.so /usr/lib64/libspnegohelp.so
... make, make install, whatever ...

I copied the libspnegohelp.so into the system so nginx can use it without any special runtime LD_LIBRARY_PATH crap.

How to configure (again, I could not validate this 100%)

location /test {
   auth_gss on;
   auth_gss_realm YOUR.KERBEROS.REALM;
   auth_gss_keytab /etc/krb5.keytab;
   auth_gss_service_name YOURMACHINENAMEIBELIEVE;

Your mileage will definitely vary but hopefully some people with more experience with Kerberos, C, nginx modules, or anything else helpful can pick it apart. I will post updates as I get them and I do want to post this on github or something... unless someone else wants to take ownership over it who will actually actively maintain/keep it up to date with nginx internals and maintain the github/whatever repository for it.

This was self-funded personally with no company sponsorship or anything, part of the terms of the project were also to keep it BSD licensed. Feel free to do whatever you want with it. If you want to send me any money to reimburse, I'll never say no to that - paypal AT mike2k.com. Or, pay a developer who can ensure it works end-to-end, if there is something missing.

Sadly, it does require the machine to be on the domain, I was hoping I could get away with it not having to be on the domain. I confirmed with Sam Hartman, who was a chief technologist at the MIT Kerberos Consortium - you can't really get more knowledgeable than that. I would have hired Sam for the project but it would have been too expensive. However if a company is willing to take this initial coding and have Sam add his magic to it, he knows C and was able to give me a real quick estimate and check how nginx modules work. He could possibly do it for cheaper now since the initial work might be done, and he would definitely be able to confirm all the logic is intact.

Thanks to YoctoPetaBorg at RentACoder.com for the initial work (and for hopefully soon finishing up the last bits of this :p) - it will be exciting to be able to use this at work and be able to have a fully functional module out there that people find useful.

Categories: nginx