Boxing would have little chance you be honest. Your reach to punch is generally shorter than the range of the knife. Better to use a thrusting kick if you are not training hand defences. Then again, any improvisation such as grabbing a handful of dirt, a stick or a chair, even spitting, may give the distraction you need to escape or enter.
If you have time to grab things then you can probably turn and run. But if you're trapped and must fight bare hands vs. knife, a thrust/front kick usually won't do much damage unless it's a good one to the face. Usually, it just pushes someone back and buys you 1-2 seconds before he comes back. This is from fighting and sparring full power...and getting hit with plenty of Teeps and sidekicks, they rarely hurt, and are just annoying and pushes me back. The ones to the face are just gross and makes people mad.
While getting off multiple jabs to the face will cause disorientation and sets up for the power shots and possible KO. This is more offensive than front kicks in a situation where you must fight bare hands vs. knife. A good Boxer can get multiple jabs off first. Untrained people who comes into train, usually just go crazy with flurries of streetfighting swings at 100% power & speed until they gas and all it takes to stop them is just jabs and footwork. Of course they're wearing gloves and not holding a knife, so no doubt it's a much lower risk. I still train Krav Maga for its weapons defense as knowing as much as possible doesn't hurt. I also train to slice someone's A up with my own blades and Mall Ninja hip shooting, quick draws, etc.