md5 collision

[Maxim Dounin]

Hello!

On Thu, Sep 13, 2012 at 07:43:16PM -0400, karlseguin wrote:

> Yes, re-requesting the same image will cause the same error (can't say with
> 100% certainty that it'll always do it though).
> 
> 
> sudo hd /mnt/tmp/nginx/cache/5f/85/1b/56cc2e05fb85eb0a806444f1811b855f
> 00000000  ff d8 ff e0 00 10 4a 46  49 46 00 01 01 00 00 01 
> |......JFIF......|
> 
> Naively, there doesn't seem to be any special header bytes?

This looks like a completely corrupted cache file, without any 
headers at all.

> Relevant config is:
> 
>   upstream origin_magick {
>     server 127.0.0.1:4000;
>     keepalive 50;
>   }
> 
>   proxy_cache_path /mnt/tmp/nginx/cache levels=2:2:2 keys_zone=main:200m
> max_size=100G;
>   proxy_cache_use_stale updating;
>   proxy_http_version 1.1;
>   proxy_cache_valid any 1m;
>   more_clear_headers 'X-amz-*' 'x-amz-*' 'X-Content-Digest' 'X-Rack-Cache;
> 
>     location / {
>       proxy_cache_bypass $http_nocache;
>       proxy_cache main;
>       proxy_pass http://origin_magick;
>       more_set_headers -s '404 403' 'Cache-Control: public, max-age=120';
>     }

Please try removing the cache file in question (move it away or 
just delete) and re-request it twice (once to cache the response, 
and once to see the error) to see if problem persists.  Please 
also make sure you are able to reproduce the problem without any 
3rd party modules/patches (and preferably with latest nginx 
1.3.6).

If the problem persists, please follow 
http://wiki.nginx.org/Debugging and provide minimal full config 
you are able to reproduce the probem with, and full debug log 
(since file removal).

Maxim Dounin