Validating user input in php dating things talk
Perhaps you're saying to yourself at this point: "Self, it seems it's not effective to check things like file extensions and user-provided data.What I need to do is to check the content of the file itself!In short, it is a great function for validating user input (examples such as login forms or email forms). The function is intended for those people who, for some strange reason, don't use PDO and are subject to SQL injection.Bypassing filters can provide a very useful lesson in how not to validate user input securely.As you may have already guessed, it’s possible to bypass such a filter by creating a file which is both a JPEG or GIF and a PHP backdoor.By using a similar command to what is listed earlier, you can append a PHP file to a JPEG image and use this attack yourself." Now take a look at this script, which instead attempts to check the Content-type header of any uploaded file to ensure that it's consistent with the type of image the upload script is intended for, which in my experience tends to typically be images.In this case, only "image/gif" and "image/jpeg" are valid values for the Content-type header: Luckily (and somewhat comically) for us, the Content-type header can be set arbitrarily and will only affect the logic of the application, which in this case is simply checking it to ensure that it is some particular value.
Author Jon Peck shows how to build a magazine cataloging system while describing how to use a MVC (Model-View-Controller) framework like Code Igniter.We can send a Content-type header of "lol/wut" if we like, or "ilovemydoggy/heissocute" or even "hacknaked/bowtomyfirewallahh".It simply doesn't matter, and as such we can very easily satisfy the application with a Content-type header of "image/gif" despite the fact that we, as pen testers, are likely uploading a file using a "php" extension.(Disclaimer: The code provided below is offered only for purposes of illustrating the writer’s thoughts and should be considered INSECURE.The included code SHOULD NOT be used on ANY Web server except when it has been carefully isolated, and even then only for the specific purpose of conducting research.) Much of the time that I spend writing exploits for Web application security flaws is spent bypassing filters of various types.