Mod_rewrite: environment variables aren’t being expanded in RewriteConds

apache-2.2mod-rewrite

I've got a RewriteCond in a .htaccess similar to:

RewriteCond "%{ENV:FOO}" =bar

But the ${ENV:FOO} is being expanded to the value of FOO, it's always blank.

For example, if I SetEnv FOO "bar" just before the RewriteCond, then crank up the RewriteLogLevel, I get this in my rewrite log:

RewriteCond: input='' pattern='=bar' => not-matched

What am I doing wrong here? How can I make environment variables expand inside of RewriteConds?

Also, if I add a silly RewriteRule like RewriteRule .* %{ENV:FOO}, I can see in the rewrite log that the variable is being correctly expanded there.

My Apache version is 2.2.17.

Edit: I've found another reference to this problem. It seems like a “solution” is to use SetEnvIf instead of SetEnv… =\

Additionally, it doesn't seem like the location of the SetEnv has any effect. I've put it both in httpd.conf and in the .htaccess, and neither work.

Best Answer

Ah, here we go. From the SetEnv documentation (under "caveats"):

The SetEnv directive runs late during request processing meaning that directives such as SetEnvIf and RewriteCond will not see the variables set with it.

So, for now, I guess I'm using:

SetEnvIf _ .* FOO=bar

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Apache mod_rewrite, using current URL in RewriteCond

You can access the "current" URI via a backreference. From the RewriteRule documentation...

TestString is a string which can contain the following expanded constructs in addition to plain text:

RewriteRule backreferences: These are backreferences of the form $N (0 <= N <= 9), which provide access to the grouped parts (in parentheses) of the pattern, from the RewriteRule which is subject to the current set of RewriteCond conditions.

You can handle the initial slash more cleanly too — the request URI always starts with a /. (The shortest request you can make is GET / HTTP/1.0.) The solution is...

# Map '/' to '/home'
RewriteRule ^/$ /home

# Check for cached page
RewriteCond %{DOCUMENT_ROOT}/system/cache/$1.html -f
RewriteRule ^/(.+)$ /system/cache/$1.html [QSA,L]

Tomcat – Apache2 – mod_expire and mod_rewrite not working in httpd.conf – serving content from tomcat

Probably the ProxyPass / directive you have in your config routes all requests to the Tomcat backend, bypassing all your mod_rewrite directives. You can try to remove the ProxyPass directive and use RewriteRule with the [P] flag after your other rewrites:

mod_rewrite: P|proxy

For the expire headers the situation is worse — in another similar question a solution was not found.

Option +FollowSymLinks would be needed for using mod_rewrite in .htaccess files; in your case it is not required, because you can put everything in the Apache config. Moving rules from config to .htaccess is pointless and can only make things slower. However, there is an important difference between .htaccess and the Apache config — in .htaccess patterns in RewriteRule are matched against relative filesystem paths (which never start with /), while in the VirtualHost context these patterns are matched against the URL path after the hostname, which always starts with /. Therefore at least one of your rules is incorrect:

RewriteRule ^content/(js|css)/([a-z]+)-([0-9]+)\.(js|css)$ /content/$1/$2.$4

should be

RewriteRule ^/content/(js|css)/([a-z]+)-([0-9]+)\.(js|css)$ /content/$1/$2.$4

(note the additional slash in the beginning).

Best Answer

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Apache mod_rewrite, using current URL in RewriteCond

Tomcat – Apache2 – mod_expire and mod_rewrite not working in httpd.conf – serving content from tomcat

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