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Asked: 2015-01-05 13:31:11 +0800 CST

Correct syntax for Apache If expressions with mod_macro

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I'm trying to exploit the power of Apache 2.4's <If> directives to customize a <Macro> by evaluating its parameters.

I'm currently trying to do the following:

  • If authenticationMode == "htpasswd" use .htpasswd file
  • If authenticationMode == "server" use pwauth
  • Else break Apache configuration

The following code (inside of a <Macro> tag) does not work

        SetEnv ROOT_PATH /somewhere #Set outside macro

        <If "$authenticationMode == 'htpasswd'"> # Guilty line!
            AuthUserFile $ROOT_PATH/path/to/.htpasswd
        </If>
        <ElseIf "$authenticationMode == 'server'">
            AuthBasicProvider external
            AuthExternal pwauth
        </ElseIf>
        <Else>
            DO_CRASH
        </Else>

Error message is Cannot parse condition clause: syntax error, unexpected T_OP_STR_EQ, expecting '('

How to fix?

apache-2.4

1 Answers

  1. Best Answer

    You can use <If> inside a <Macro>, but not to customize a <Macro> with <If>.

    As mentioned in my comment, the <Macro> is evaluated only at start up, and <If> are evaluated for each incoming request.

    To solve your problem, put your $authenticationMode variable into single quotes, because it is a string (as you have done for the right part):

    <If "'$authenticationMode' == 'htpasswd'">

    But what this macro will do is as follow:

    At start up you have somewhere in your config the instruction Use mymacro $param

    The mod_macro doc says:

    At server startup time, each of these Use invocations would be expanded into a full virtualhost (*), as described by the Macro definition.

    (* = The example in the doc is about virtualhosts)

    So if you have Use mymacro htpasswd, it will expand to following config:

    <If "'htpasswd' == 'htpasswd'"> # Guilty line!
    AuthUserFile $ROOT_PATH/path/to/.htpasswd
</If>
<ElseIf "'htpasswd' == 'server'">
    AuthBasicProvider external
    AuthExternal pwauth
</ElseIf>
<Else>
    DO_CRASH
</Else>

    This will test for each request some not very usefull conditions. And your server will never start because of the DO_CRASH instruction.

    As alternative way, I would think about writing 2 macros: one corresponding to the authenticationMode == "htpasswd" and another for the authenticationMode == "server".

    Please test and and take into account that I'm still learning Apache 2.4, so it may not be complete answer... Hope this helps!

    A good read of Apache's expression doc could be useful too.

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