nginx proxy pass and CROS(cross-origin resource sharing)

[peng yuehui]

I configed nginx to combine the CROS config and the proxy pass.

When I use 'if' statement to judge whether the domain is allowed to CROS, the proxy pass worked badly, It added another suffix to the origin url. Details see the following config snippet and explanation. I think the 'if' statement has some defects, hope you can fix it.

The config1 will get the right results, the config2 will add another "resource" path to the end of /sync/resource, like /sync/resource/resource, this leading to backend not response it. The if statement is true, I direct return 200 will see the origin headers existing, but why when I added the 'if' statement , the behavior of proxy pass changed.

config1
<snippet>

location /resource {

add_header 'Access-Control-Allow-Methods' 'GET,POST,DELETE,OPTIONS';
add_header 'Access-Control-Allow-Credentials' 'true';
add_header 'Access-Control-Allow-Origin' "$http_origin";
add_header 'Access-Control-Allow-Headers' 'WD-Since,WD-Start,WD-Direction,WD-Length,WD-Ids,Content-Type,WD-Client-Id';
add_header 'Access-Control-Expose-Headers' 'WD-Total-Length,WD-Phone-Modal,WD-Client-Id,WD-Udid,WD-Need-More';
proxy_cache off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass ​http://sync-nodes/sync/resource;

}

</snippet>

config2
<snippet>

location /resource {

if ($http_origin ~* "https?:.*\.XXXX\.com") {

add_header 'Access-Control-Allow-Methods' 'GET,POST,DELETE,OPTIONS';
add_header 'Access-Control-Allow-Credentials' 'true';
add_header 'Access-Control-Allow-Origin' "$http_origin";
add_header 'Access-Control-Allow-Headers' 'WD-Since,WD-Start,WD-Direction,WD-Length,WD-Ids,Content-Type,WD-Client-Id';
add_header 'Access-Control-Expose-Headers' 'WD-Total-Length,WD-Phone-Modal,WD-Client-Id,WD-Udid,WD-Need-More';

}
proxy_cache off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass ​http://sync-nodes/sync/resource;

}

</snippet>

[Maxim Dounin]

This is one of the known problems with the "if" directive used in a location context, see ​​http://wiki.nginx.org/IfIsEvil. Reduced test case is as follows (copied from the wiki page in question):

        # request will be sent to backend without uri changed
        # to '/' due to if
 
        location /proxy-pass-uri {
            proxy_pass http://127.0.0.1:8080/;
 
            set $true 1;
 
            if ($true) {
                # nothing
            }
        }

Closing this ticket as duplicate as we already have a ticket in track about various "if" directive problems, see #86.