verath / hashmagic

Appends data to a file until the SHA1 hash of the data is a magic hash

hashmagic

Appends data to a file until the SHA1 hash of the data is a magic hash (see e.g. http://turbochaos.blogspot.com/2013/08/exploiting-exotic-bugs-php-type-juggling.html). This can be used to make two different files that still bypass checks like this (note the usage of == rather than ===):

if (sha1_file($_FILES["file1"]["tmp_name"]) == sha1_file($_FILES["file2"]["tmp_name"])) {
    echo "Files are identical";
}

Created for a level of Hacky Easter 2018, but turned out not to be the appropriate solution.

Usage

$ go run main.go pathToFile

Produces a pathToFile.out that has the same content as pathToFile + some data added to the end so that SHA1(pathToFile.out) is a magic hash.