Conditional HTTP Basic Auth in Apache 2.4

Conditional HTTP Basic Auth in Apache 2.4

One of our internally used application uses HTTP Basic auth to authenticate a user against our LDAP instance. In a recent attempt I had the need to expose one endpoint publicly without the need of an authentication. I tried several solutions but each of them did not work for my specific use case. At first I tried several Location directives but that did not work as expected. I also tried the LocationMatch directive which also did not work. By accident I came across a blog post stating that Apache 2.4 supports if/else style syntax and that seemed to work fine for me.

<VirtualHost *:80>
    DocumentRoot /srv/app/web/

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

    <Directory /srv/app/web/>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted

    <Location />
        <If "%{THE_REQUEST} =~ m#^POST /my/trigger#i">
            # No authentication needed
            Require all granted
            # authnz_ldap logic here...

The if tag supports different expressions to evaluate data. You can use binary operators, different functions or regular expressions. In the example above I used a regex because the trigger url for my specific use case can contain different parameters. The expressions syntax also supports variables like REQUEST_URI or PATH_INFO. Due to some rewrite logic neither of those contained the requested url. Thus I had to use the THE_REQUEST variable. On the plus side this also gave me the chance to check for the HTTP method involved, making it possible to expose the url just for POST requests.

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Eintrag von Stephan Hochdörfer am 01.02.2017

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