partial urlEncoding when using if and $request_uri

[Maxim Dounin]

Hello!

On Mon, Nov 11, 2013 at 09:51:01AM -0500, mte03 wrote:

> Hi,
> 
> I have observed strange behavior with nginx rewrites. What happens: I get
> request going to myserver.com/appID/path1/path2/uglyID and I need to proxy
> this to appID.backend.internal/path1/path2/uglyID. The uglyID is URL encoded
> because it contains characters like commas and forward slashes. When I do
> location matching in nginx, nginx will url decode $uri parameter on which it
> does matches. That's not a problem, when the location matches, I can extract
> the appID and then extract the rest from $request_uri. And here the issue
> happens. If I use:  
> 
> if ($request_uri ~ ^/[^\/]+(/.*)$ ) { set $path $1; }, the uglyID (but only
> uglyID) gets URL encoded again. The $path simply is
> /path1/path2/urlEncoded(uglyID). However, when I do 
> 
> if ($uri ~ ^/[^\/]+(/.*)$ ) { set $path $1; }, then $path will be the
> urlDecoded(/path1/path2/uglyID) - as expected.
> 
> I have tested this on ubuntu 12.04 (Linux ip-10-50-20-57 3.2.0-36-virtual
> #57-Ubuntu SMP Tue Jan 8 22:04:49 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux)
> and nginx versions nginx/1.1.19 and nginx/1.5.6 - and the behavior is
> consistently same in both versions. The nginx config is identical in all
> cases, only difference is the name of the variable in the if statement,
> where using $request_uri simply implies uglyID (but only uglyID - not the
> whole matched string) will be url encoded again. Meanwhile I have found
> possible workaround using maps, where matching on $request_uri works
> correctly and doesn't modify matched data anyhow. 
> 
> So I wonder, has anyone else experienced this? Is this expected? Why is the
> uglyID (but only uglyID) url encoded again? I would expect either
> urlEncoding of the whole match, or none at all - as it doesn't happen when I
> try to match e.g. $uri... Could this indicate a possible bug?

Yes, this looks like a bug.  Here is a ticket we already have for 
this:

http://trac.nginx.org/nginx/ticket/348

-- 
Maxim Dounin
http://nginx.org/en/donation.html