Reverse proxy replaces square brackets in request

Server NGINX
1

Hi,

I have a redirect loop problem with a website that gets reversed
proxied. It looks like the following is the cause (which I don’t know
how to solve)

Inspecting the site with httpfox, the request my browser sends looks
like this:
https://www.acme.eu/acm/admin/gui_call.php?Object=admin@GuiAdminStartpage&Params[gui]=&action=&no_subtitle=1

My nginx log tells me this:
GET
/acm/admin/gui_call.php?Object=admin@GuiAdminStartpage&Params%252525252525252525252525255bgui%252525252525252525252525255d=&action=&no_subtitle=1
HTTP/1.1"
HTTP/1.1" 301 486 “https://www.acme.eu/acm/ui/” “Mozilla/5.0 (X11;
Ubuntu; Linux x86_64; rv:13.0) Gecko/20100101 Firefox/13.0.1”

(This repeats over and over until firefox detects the loop)

To me it looks like somehow nginx changes the square brackets around
“gui” into “252525252525252525252525255b” and
“252525252525252525252525255d” respectively. I assume that because the
script gui_call.php gets wrong parameters, it redirects to /acm/ui.
/acm/ui calls gui_call.php with wrong paramters, and so on.

If my interpretation is correct, how can I stop this? If not, what is
going on here?

Isaac

2

Hello!

On Fri, Jul 13, 2012 at 12:49:08PM +0200, Isaac H. wrote:

My nginx log tells me this:
“252525252525252525252525255d” respectively. I assume that because
the script gui_call.php gets wrong parameters, it redirects to
/acm/ui. /acm/ui calls gui_call.php with wrong paramters, and so on.

If my interpretation is correct, how can I stop this? If not, what
is going on here?

The “GET … HTTP/1.1” in nginx logs is what your browser sent to
nginx. Original request from browser likely had
“…Params=%5bgui%5d…” in it (which is ok as per RFC 3986 square
brackets must be escaped).

It’s not clear why and where additional escaping of a “%”
character to “%25” happens, but likely in the same code which does
redirects, i.e. it’s probably up to your php script.

Maxim D.