Use only pure streaming operations, except for one rewind.

[defuse]

The File encryption and decryption make heavy use of ftell() to measure file sizes and get the current position within the file. Does this make it vulnerable to any sort of TOCTTOU attacks?

Some ideas:

• What if we've opened a file in read-only mode and some other process has it open in append-only mode, and the size changes after we've measured it?
• Others?

What guarantees does "the operating system" provide once we have a file resource? Note that "the operating system" is every operating system PHP runs on, so we have to look at the lowest common denominator.

[paragonie-scott]

I wonder if we could use flock() too? :)

[defuse]

flock() is a different sort of thing. It doesn't actually give you exclusive rights to the file, it's more of a voluntary advisory thing.

[paragonie-scott]

Seems like a mostly useless feature then. Hmm.

[paragonie-scott]

Could we abstract everything into a stream object? Keep track of the file size and position without relying on ftell() etc.?

[paragonie-scott]

For example: paragonie/halite@e8c3e3b

https://github.com/paragonie/halite/blob/master/src/Stream/ReadOnlyFile.php

[defuse]

This is going to (probably) be fixed in the newer commit, but I want to take a look at the whole thing, not just diffs, before I close it.

[defuse]

It's much better now, but we're still using fstat and ftell to know when to pass the different length argument to readBytes. Hmm... Maybe readBytes() should just tell its caller when its reached EOF, so that we can check that and know when to stop. Then, it would be entirely stream based, and the only "weird" operation would be a simple rewind back to the beginning.

[defuse]

readBytes telling the caller about EOF also makes it super easy to fix #145.