How would i check that a file is either jpeg, pdf or tiff? And I mean actually checking, not just from mime type and file extension.
I have access to the raw file data (this check is part of an uploader) and i need to verify that the files are either jpeg, pdf or tiff. I assume I would have to check for some sort of headers in the files but I have no idea what to look for and where to start.
You need to implement byte sequence tests.
Here is a guide to checking byte sequences for the most common image formats.