Re: easy way to acquire height / width from images (PNG, JPEG) stored as bytea?

On 17/4/20 6:14 μ.μ., Imre Samu wrote:
> > it killed my 200+ days uptime FreeBSD box :( .
> > As I describe above, those attachments are nowhere as files.
> > They are email attachments. Also we got about half TB of them.
>
> it is possible - that  some image is a "decompression bomb" ?
>
> /"Because of the efficient compression method used in Portable Network
> Graphics (PNG) files, a small PNG file can expand tremendously, acting
> as a "decompression bomb". *Malformed PNG chunks can consume a large
> amount of CPU and wall-clock time and large amounts of memory, up to
> all memory available on a system, causing a Denial of Service (DoS).*
> Libpng-1.4.1 has been revised to use less CPU time and memory, and
> provides functions that applications can use to further defend against
> such files."/
> https://libpng.sourceforge.io/decompression_bombs.html
> https://stackoverflow.com/questions/33602308/how-to-check-png-file-if-its-a-decompression-bomb
>
> Regards,
>  Imre

Thank you  a lot Imre. Great info.

>
>
> Achilleas Mantzios <achill(at)matrix(dot)gatewaynet(dot)com
> <mailto:achill(at)matrix(dot)gatewaynet(dot)com>> ezt írta (időpont: 2020. ápr.
> 17., P, 16:39):
>
> On 17/4/20 4:09 μ.μ., Adam Brusselback wrote:
>
>> Why not extract and store that metadata with the image rather
>> than trying to extract it to filter on at query time? That way
>> you can index your height and width columns to speed up that
>> filtering if necessary.
>>
> Yes I thought of that, but those are coming automatically from our
> mail server (via synonym), we have written an alias : a program
> that parses and stores emails. This is generic, I wouldn't like to
> add specific code (or specific columns) just for image
> attachments. However I dig the idea of the indexes.
>> You may be able to write a wrapper for a command line tool like
>> imagemagic or something so you can call that from a function to
>> determine the size if you did want to stick with extracting that
>> at query time.
> As I describe above, those attachments are nowhere as files. They
> are email attachments. Also we got about half TB of them.
>