File Validator iOS

Validate files in the main bundle to prevent a user to change them. (to cheat on config files)

Just the first commit to save some work done this evening..

The idea is to compute a hash (SHA256) of a config file (for example a plist) plus a known secret (that will be compiled in the binary)

the repo comes with a static lib and an example, cocoapod spec will come with v0.1, this is just a first draft.

Usage

fingerprints.plist is a plist that need to be added to your project target and containing all the filenames that you want to secure with the relative correct hash ( without the script the way to fill this information is to run the validator and ... copy and paste the hash in the fingerprints plist)

usage is:

[FVFileValidator setSecret:@"asda8r32ijiwesjza9sa9idsadi0saidas0kdo3"];
BOOL isValid = [FVFileValidator validateFile:@"filetosecure.plist"];

First we need to set a string as a secret. Calling validateFile: will return YES if the file is valid (the sha256 of filetosecure.plist + the secret matches the one defined in the fingerprints.plist)

forgetting to set the secret, create the fingerprints.plist, having the entry of the file we want to check in the fingerprints.plist will raise an Exception

Now supports mutable fingerprints, stored in the NSUserDefaults, and always overwritten with the contents of the fingerprints.plist file, to enable app updates. You can add a signature to a file you trust to be correct ( which you modified or created ) using

[FVFileValidator signFile:@"filetosecure.plist"];

Not having the file in fingerprints.plist will now just silentry return false instead of throwing an exception.

TODO

• [ x ] ruby python script for filling the fingerprints.plist with the right hashes
• the above script modified as a pre build script to run in xcode
• [ x ] some bit byte operation to obfuscate a bit the secret