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README.md

A minimal nginx auth_request authentication service, based on cookies and htpasswd.

Build Status

This little go tool can be used as an authentication service for nginx's ngx_http_auth_request_module, verifying that session cookies are valid and allowing users to log in and have their data validated against a .htpasswd file.

This means that if you run nginx and you have few users (and few-enough sessions), you can run this service next to an actual service you're running and have htpasswd-login run a RESTful service for authentication and even serve up a customizable authentication form.

Installation / running this

htpasswd-login requires a go modules to build, so a recent go checkout is recommended - in CI, this tool builds with go 1.14.x.

You can go get -u github.com/antifuchs/htpasswd-login and you should end up with a htpasswd-login binary in your $GOBIN directory.

Once installed, you can try out this service on the commandline like this (assuming /tmp/sessions exists):

htpasswd-login --sessions /tmp/sessions --htpasswd example/htpasswd --secure=false --loginform=example/page

See example/README.md for details.

Once the login form looks like you think it should, deploy this to be visible to the big, bad internet. The following sections are (in order of importance) what you will definitely need to do:

Use HTTPS

In deployment (if you're running on HTTPS, which you should), please run this with --secure=true so that no cookies leak over insecure channels.

Configure a CSRF secret

htpasswd-login uses CSRF protection to hopefully prevent some easy avenues for phishing from authenticated sites. You should generate a CSRF secret and re-use this (otherwise login forms served to clients will no longer be submittable if you restart the server).

To generate a secret once, use dd if=/dev/urandom bs=32 count=1 | openssl base64 > csrf-secret.b64

Then, to use that secret, pass the --csrf="$(cat csrf-secret.b64)" flag to htpasswd-login.

Set up a cron job to clean out old sessions

Once this is working for you, make sure to run the tool with the same arguments as you run the frontend with, and add -cleanup in a cron job once an hour or so, in order to clean out old sessions.

Configuring nginx

See the file auth_request.inc.conf in examples for an example config. Note that in addition to including this file in your server blocks, you'll also have to have an auth_request /auth stanza in every location block you wish to protect.

Limits & Operation

This tool is meant for personal use, and specifically constrains itself to some design choices that you shouldn't make when running this on a larger scale. Here are the assumptions I've made:

  • You don't have very many users. Credential lookup is O(n), which means that more users will make logins slow.

  • Each user doesn't have very many sessions. We store sessions in a directory, which means that as the total number of sessions grows into the many thousands, looking up those sessions will get slower (and may slow down your overall system).

  • You should run -cleanup regularly, to remove old sessions.

Why?

You obviously have questions. I have reasons for building this. (And I would have loved not to have to build this!) Here goes:

Why not just use HTTP Basic authentication?

That's a good question: HTTP Basic authentication is quite simple, and if you can use it, you probably should!

However, Basic auth has some drawbacks:

  • Most browsers present a UI that isn't suitable for password managers

  • Some backend programs are not completely able to deal with living behind Basic auth: Some generate URLs that just don't work.

I think this tool combines the nicest advantages of HTTP Basic authentication (namely, that you can use .htpasswd files, which are very well understood and easy to manipulate), with a nice and accessible way for your users to log in.

As an accomodation for native apps that act as API clients, requests bearing an HTTP Basic Authorization header matching the credentials in the .htpasswd file count as authenticated. So you can use Basic authentication, however your users won't receive a login prompt.

Why not build authentication into a the thing you're running behind the scenes?

That mostly has to do with the amount of trust I'm willing to place in the backend program: If that has a preauth bug, there's a problem. (That said, if this program has a preauth bug, I would love to hear about it!)

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A RESTful authentication service combining .htpasswd and nginx's auth_request

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