[TYPO3-core] RFC: Make image hash names longer to avoid collisions

[Ernesto Baschny [cron IT]]

Karsten Dambekalns wrote: on 16.05.2007 14:55:

> Type: bugfix, somewhat
> Branches: all 4.x if you like
> 
> We recently saw some cases of wrong images being displayed. After
> investigating we concluded that the only possible explanation could be a
> name collision, because two different images got the same short md5 hash
> as generated filename.
> 
> This possible problem has been discussed back in 2004, btw:
> http://lists.netfielders.de/pipermail/typo3-dev/2004-July/004597.html
> 
> The attached patch fixes the issue for me, the length of the hash in
> then configurable via TYPO3_CONF_VARS, default stays with 10 chars to
> make sure nothing changes. For trunk we could make this 32, I'd say.
> Names will then have longer md5 names, massively reducing the risk of
> name collisions.

I guess if you had this problem with resizes created by imagemagick, we
will end up having the same problem in every place we currently use
"short" md5's. There might be places where the risk is lower (less
entries), but images are certainly not the only place where there might
be massive amounts of variants. So maybe we could switch to 32-chars on
more than just this place? I can think of: cHash, Imagemagick output,
GIFBUILDER output, maybe others. And also be aware of the places where
this has is written to the DB, the field might be too small.

Cheers,
Ernesto