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/* eslint-disable no-bitwise -- Convenient */

import jsep from 'jsep';

import jsepRegex from '@jsep-plugin/regex';

import jsepAssignment from '@jsep-plugin/assignment';

// register plugins

jsep.plugins.register(jsepRegex, jsepAssignment);

jsep.addUnaryOp('typeof');

jsep.addUnaryOp('void');

jsep.addLiteral('null', null);

jsep.addLiteral('undefined', undefined);

const BLOCKED_PROTO_PROPERTIES = new Set([

'constructor',

'__proto__',

'__defineGetter__',

'__defineSetter__',

'__lookupGetter__',

'__lookupSetter__'

]);

const SafeEval = {

/**

* @param {jsep.Expression} ast

* @param {Record<string, any>} subs

evalAst (ast, subs) {

switch (ast.type) {

case 'BinaryExpression':

case 'LogicalExpression':

return SafeEval.evalBinaryExpression(ast, subs);

case 'Compound':

return SafeEval.evalCompound(ast, subs);

case 'ConditionalExpression':

return SafeEval.evalConditionalExpression(ast, subs);

case 'Identifier':

return SafeEval.evalIdentifier(ast, subs);

case 'Literal':

return SafeEval.evalLiteral(ast, subs);

case 'MemberExpression':

return SafeEval.evalMemberExpression(ast, subs);

case 'UnaryExpression':

return SafeEval.evalUnaryExpression(ast, subs);

case 'ArrayExpression':

return SafeEval.evalArrayExpression(ast, subs);

case 'CallExpression':

return SafeEval.evalCallExpression(ast, subs);

case 'AssignmentExpression':

return SafeEval.evalAssignmentExpression(ast, subs);

default:

throw SyntaxError('Unexpected expression', ast);

}

evalBinaryExpression (ast, subs) {

const result = {

'||': (a, b) => a || b(),

'&&': (a, b) => a && b(),

'|': (a, b) => a | b(),

'^': (a, b) => a ^ b(),

'&': (a, b) => a & b(),

// eslint-disable-next-line eqeqeq -- API

'==': (a, b) => a == b(),

// eslint-disable-next-line eqeqeq -- API

'!=': (a, b) => a != b(),

'===': (a, b) => a === b(),

'!==': (a, b) => a !== b(),

'<': (a, b) => a < b(),

'>': (a, b) => a > b(),

'<=': (a, b) => a <= b(),

'>=': (a, b) => a >= b(),

'<<': (a, b) => a << b(),

'>>': (a, b) => a >> b(),

'>>>': (a, b) => a >>> b(),

'+': (a, b) => a + b(),

'-': (a, b) => a - b(),

'*': (a, b) => a * b(),

'/': (a, b) => a / b(),

'%': (a, b) => a % b()

}[ast.operator](

SafeEval.evalAst(ast.left, subs),

() => SafeEval.evalAst(ast.right, subs)

);

return result;

evalCompound (ast, subs) {

let last;

for (let i = 0; i < ast.body.length; i++) {

if (

ast.body[i].type === 'Identifier' &&

['var', 'let', 'const'].includes(ast.body[i].name) &&

ast.body[i + 1] &&

ast.body[i + 1].type === 'AssignmentExpression'

) {

// var x=2; is detected as

// [{Identifier var}, {AssignmentExpression x=2}]

// eslint-disable-next-line @stylistic/max-len -- Long

// eslint-disable-next-line sonarjs/updated-loop-counter -- Convenient

i += 1;

}

const expr = ast.body[i];

last = SafeEval.evalAst(expr, subs);

}

return last;

evalConditionalExpression (ast, subs) {

if (SafeEval.evalAst(ast.test, subs)) {

return SafeEval.evalAst(ast.consequent, subs);

}

return SafeEval.evalAst(ast.alternate, subs);

evalIdentifier (ast, subs) {

if (Object.hasOwn(subs, ast.name)) {

return subs[ast.name];

}

throw ReferenceError(`${ast.name} is not defined`);

evalLiteral (ast) {

return ast.value;

evalMemberExpression (ast, subs) {

const prop = String(

// NOTE: `String(value)` throws error when

// value has overwritten the toString method to return non-string

// i.e. `value = {toString: () => []}`

ast.computed

? SafeEval.evalAst(ast.property) // `object[property]`

: ast.property.name // `object.property` property is Identifier

);

const obj = SafeEval.evalAst(ast.object, subs);

if (obj === undefined || obj === null) {

throw TypeError(

`Cannot read properties of ${obj} (reading '${prop}')`

);

}

if (!Object.hasOwn(obj, prop) && BLOCKED_PROTO_PROPERTIES.has(prop)) {

throw TypeError(

`Cannot read properties of ${obj} (reading '${prop}')`

);

}

const result = obj[prop];

if (typeof result === 'function') {

return result.bind(obj); // arrow functions aren't affected by bind.

}

return result;

evalUnaryExpression (ast, subs) {

const result = {

'-': (a) => -SafeEval.evalAst(a, subs),

'!': (a) => !SafeEval.evalAst(a, subs),

'~': (a) => ~SafeEval.evalAst(a, subs),

// eslint-disable-next-line no-implicit-coercion -- API

'+': (a) => +SafeEval.evalAst(a, subs),

typeof: (a) => typeof SafeEval.evalAst(a, subs),

// eslint-disable-next-line no-void, sonarjs/void-use -- feature

void: (a) => void SafeEval.evalAst(a, subs)

}[ast.operator](ast.argument);

return result;

evalArrayExpression (ast, subs) {

return ast.elements.map((el) => SafeEval.evalAst(el, subs));

evalCallExpression (ast, subs) {

const args = ast.arguments.map((arg) => SafeEval.evalAst(arg, subs));

const func = SafeEval.evalAst(ast.callee, subs);

/* c8 ignore start */

if (func === Function) {

// unreachable since BLOCKED_PROTO_PROPERTIES includes 'constructor'

throw new Error('Function constructor is disabled');

}

/* c8 ignore end */

return func(...args);

evalAssignmentExpression (ast, subs) {

if (ast.left.type !== 'Identifier') {

throw SyntaxError('Invalid left-hand side in assignment');

}

const id = ast.left.name;

const value = SafeEval.evalAst(ast.right, subs);

subs[id] = value;

return subs[id];

}

};

/**

* A replacement for NodeJS' VM.Script which is also {@link https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP | Content Security Policy} friendly.

class SafeScript {

/**

* @param {string} expr Expression to evaluate

constructor (expr) {

this.code = expr;

this.ast = jsep(this.code);

}

/**

* @param {object} context Object whose items will be added

* to evaluation

* @returns {EvaluatedResult} Result of evaluated code

runInNewContext (context) {

// `Object.create(null)` creates a prototypeless object

const keyMap = Object.assign(Object.create(null), context);

return SafeEval.evalAst(this.ast, keyMap);

}

export {SafeScript};

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