Rob Mayoff mayoff

Summary text.

Hello World, how is it going?

Another thing.

Using LLVM's libfuzzer with Swift

Background

Of the many tools available for fuzzing, I've found that LLVM's libfuzzer is the easiest to use for Swift on macOS. Other tools seem to have a list of requirements taht are difficult to meet. libfuzzer on the other hand is built into LLVM and is available on macOS in the custom Swift toolchains: https://www.swift.org/download/

In this document I'll describe how to use libfuzzer with Swift and Swift Packages.

I used this setup to fuzz an SVG Renderer package that I am building. I was able to find and fix a number of bugs in my SVG parsing code using libfuzzer in basically no time at all.

	#if os(iOS)
	import UIKit
	#else
	import AppKit
	#endif

	let view = UIView(frame: CGRectMake(0, 0, 400, 300))
	view.backgroundColor = UIColor.redColor()

	let button = UIButton(type: .Custom)

	import AppKit

	public extension NSBezierPath {

	public var CGPath: CGPath {
	let path = CGMutablePath()
	var points = [CGPoint](repeating: .zero, count: 3)
	for i in 0 ..< self.elementCount {
	let type = self.element(at: i, associatedPoints: &points)
	switch type {

	a: AM/PM
	A: 0~86399999 (Millisecond of Day)

	c/cc: 1~7 (Day of Week)
	ccc: Sun/Mon/Tue/Wed/Thu/Fri/Sat
	cccc: Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday

	d: 1~31 (0 padded Day of Month)
	D: 1~366 (0 padded Day of Year)

	#!/bin/sh

	defaults read com.apple.finder CreateDesktop > /dev/null 2>&1
	enabled=$?

	if [ "$1" = "off" ]; then
	if [ $enabled -eq 1 ]; then
	defaults write com.apple.finder CreateDesktop false
	osascript -e 'tell application "Finder" to quit'
	open -a Finder

	import Cocoa
	import MetalKit

	@NSApplicationMain
	class AppDelegate: NSObject, NSApplicationDelegate, MTKViewDelegate {
	weak var window: NSWindow!
	weak var metalView: MTKView!
	let device = MTLCreateSystemDefaultDevice()!
	var commandQueue: MTLCommandQueue!
	var pipelineState: MTLRenderPipelineState!