Our code, that we will be using to simulate server behaviour, looks like this: server.php In this article let's consider a scenario in which we'll be performing a security assessment of a PHP application that uses imageCreateFromPngor imagepng for image processing. They usually perform some image manipulation as cropping, compression etc., thus "destroying" the malicious input. Most of the web applications, however, show that it is rather unlikely to happen. php extension it would mean that you can easily gain RCE on the server. If you could upload a previously prepared image on the server as 1:1 copy with a. Moreover, you can create image with particular byte order that will form malicious payload as bytes’ representation. If you open an image file in a hex editor you will immediately notice that those pixels are nothing more than just bytes. PoC from our article was tested on PHP 7.3.10-1 (cli) (built: 05:24:47) (NTS)Įvery graphic file consists of pixels.
Php imagegif install#
If you don’t mind your image being skewed you can also supply the fourth argument (which is the output height). createThumbnail ( 'profile.jpg', 'profile_thumb.jpg', 160 ) Using this script you can now for example generate square 160 by 160 pixel thumbnails with the following command. */ function createThumbnail ( $src, $dest, $targetWidth, $targetHeight = null ) * $targetHeight - desired output height or null Link image type to correct image loader and saver // - makes it easier to add additional types later on // - makes the function easier to read const IMAGE_HANDLERS =, IMAGETYPE_PNG =>, IMAGETYPE_GIF => ] /** It’s well documented so each sub-step is explained.
Create a thumbnail by duplicating the image and resizing it.Load the image (using the correct PHP function).For those we’ll need the following PHP methods: As it’s really cumbersome to have a thumbnail function per image type our mission is to write one function to handle all the usual image types.
PHP has a long list of functions that can load images. Images ready? Launch your editor and let’s do some coding! The tutorial will not discuss uploading files to the server.
Php imagegif code#
Want to get the code and get back to your project? Download the script here.įor this article I’ll assume you’ve got some images uploaded on your PHP server. In this article we’ll look at a function that handles various image types and resizes them to a set width and height. If you’ve got photo galleries on your website or need to generate avatars from uploaded profile pictures you’ll most likely want to create thumbnails.
0 kommentar(er)
