Nginx url decoding URI problem with proxy_pass

[Igor A. Ippolitov]

Michael,

You can use rewrite. Just catch the host part:
 >rewrite /image_preview/https://(?<my_host>[^ :/]/(.*) /$1;
 >proxy_pass https://$my_host
rewrite will encode the URL back again.

On 26.07.2018 20:18, Michael Kovacs wrote:
> Greetings Nginx mailing list!
>
> I'm using nginx as an image proxy and am using proxy_pass to fetch the 
> image. Unfortunately if that image URL has a space in it the 
> proxy_pass fails. It works fine with any other image.
>
> example successful URL:
>
> /image_preview/https://somedomain.com/image.jpg 
> <https://somedomain.com/image.jpg>
>
> example failedl URL:
>
> /image_preview/https://somedomain.com/My%20Images/image.jpg 
> <https://somedomain.com/My%20Images/image.jpg>
>
> ^^
> Nginx is URL decoding the url in the path and putting the space back in.
>
> Here's my nginx.conf
>
>         # redirect thumbnail url to real world
>         location ~ ^/image_preview/(.*?)$  {
>             resolver ${HOST};
>
>             set $fallback_image_url ${FALLBACK_IMAGE_URL};
>             set $image_url $1;
>
>             if ($args) {
>                 set $image_url $1?$args;
>             }
>
>             proxy_intercept_errors on;
>             error_page 301 302 303 305 306 307 308 $fallback_image_url;
>             error_page 400 401 402 403 404 405 406 409 408 409 410 411 
> 412 413 414 415 416 417 $fallback_image_url;
>             error_page 500 501 502 503 504 505 506 507 508 509 510 511 
> 520 522 598 599 $fallback_image_url;
>
>             proxy_connect_timeout 2s;
>             proxy_read_timeout 4s;
>             proxy_pass_request_headers off;
>             proxy_buffering off;
>             proxy_redirect off;
>
>             proxy_pass $image_url;
>             proxy_set_header If-None-Match $http_if_none_match;
>             proxy_set_header If-Modified-Since $http_if_modified_since;
>         }
>
> I've scoured the docs, stackoverflow, and the internet in general but 
> don't see how to address this problem. As I see it I have two options:
>
> 1) Find a way to make nginx not URL decode the param URL (doesn't seem 
> possible)
> 2) The original $request_uri contains the URL encoded URL. Find a way 
> to create a rewrite rule to strip off the prefix and proxy_pass to the 
> resulting URL. I haven't found a way to do something liek that as it 
> appears rewrite rules will only operate on the URI in context and that 
> URI appears to be decoded.
>
> I've found an entire chapter in "Nginx Troubleshooting" on creating a 
> proxy for external links. But that example also appears to fall vicitm 
> to this same problem.
>
> Any help/pointers would be appreciated as I am pretty well stuck at 
> this point on an  approach that might work.
>
> Thanks,
> -Michael
>
>
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