Eval Loophole
This is a hack to enable third-party libraries that depend on a limited subset of eval
semantics to work in Atom with a content security policy that forbids calls to eval
.
{allowUnsafeEval, allowUnsafeNewFunction} = require 'loophole'
allowUnsafeEval ->
crazyLibrary.exploitLoophole() # allows `eval(...)`
allowUnsafeNewFunction ->
crazyLibrary.exploitLoophole() # allows `new Function(...)`
You can also use the exported Function
constructor directly:
{Function} = require 'loophole'
f = new Function("return 1 + 1;")
How?
allowUnsafeEval
replaces eval
with a call to vm.runInThisContext
, which won't perfectly emulate eval
but is good enough in certain circumstances, like compiling PEG.js grammars.
allowUnsafeNewFunction
temporarily replaces global.Function
with loophole.Function
, which passes the source of the desired function to vm.runInThisContext
.
Why?
If there's a loophole, why even enable CSP? It still prevents developers from accidentally invoking eval with legacy libraries. For example, did you know that jQuery runs eval when you pass it content with script tags? If you want eval, you'll need to explicitly ask for it.