164 lines
6 KiB
JavaScript
164 lines
6 KiB
JavaScript
/**
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* @fileoverview Rule to flag use of implied eval via setTimeout and setInterval
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* @author James Allardice
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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type: "suggestion",
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docs: {
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description: "disallow the use of `eval()`-like methods",
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category: "Best Practices",
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recommended: false,
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url: "https://eslint.org/docs/rules/no-implied-eval"
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},
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schema: []
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},
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create(context) {
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const CALLEE_RE = /^(setTimeout|setInterval|execScript)$/u;
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/*
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* Figures out if we should inspect a given binary expression. Is a stack
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* of stacks, where the first element in each substack is a CallExpression.
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*/
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const impliedEvalAncestorsStack = [];
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//--------------------------------------------------------------------------
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// Helpers
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//--------------------------------------------------------------------------
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/**
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* Get the last element of an array, without modifying arr, like pop(), but non-destructive.
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* @param {Array} arr What to inspect
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* @returns {*} The last element of arr
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* @private
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*/
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function last(arr) {
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return arr ? arr[arr.length - 1] : null;
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}
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/**
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* Checks if the given MemberExpression node is a potentially implied eval identifier on window.
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* @param {ASTNode} node The MemberExpression node to check.
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* @returns {boolean} Whether or not the given node is potentially an implied eval.
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* @private
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*/
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function isImpliedEvalMemberExpression(node) {
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const object = node.object,
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property = node.property,
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hasImpliedEvalName = CALLEE_RE.test(property.name) || CALLEE_RE.test(property.value);
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return object.name === "window" && hasImpliedEvalName;
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}
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/**
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* Determines if a node represents a call to a potentially implied eval.
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*
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* This checks the callee name and that there's an argument, but not the type of the argument.
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*
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* @param {ASTNode} node The CallExpression to check.
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* @returns {boolean} True if the node matches, false if not.
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* @private
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*/
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function isImpliedEvalCallExpression(node) {
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const isMemberExpression = (node.callee.type === "MemberExpression"),
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isIdentifier = (node.callee.type === "Identifier"),
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isImpliedEvalCallee =
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(isIdentifier && CALLEE_RE.test(node.callee.name)) ||
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(isMemberExpression && isImpliedEvalMemberExpression(node.callee));
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return isImpliedEvalCallee && node.arguments.length;
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}
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/**
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* Checks that the parent is a direct descendent of an potential implied eval CallExpression, and if the parent is a CallExpression, that we're the first argument.
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* @param {ASTNode} node The node to inspect the parent of.
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* @returns {boolean} Was the parent a direct descendent, and is the child therefore potentially part of a dangerous argument?
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* @private
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*/
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function hasImpliedEvalParent(node) {
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// make sure our parent is marked
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return node.parent === last(last(impliedEvalAncestorsStack)) &&
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// if our parent is a CallExpression, make sure we're the first argument
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(node.parent.type !== "CallExpression" || node === node.parent.arguments[0]);
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}
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/**
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* Checks if our parent is marked as part of an implied eval argument. If
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* so, collapses the top of impliedEvalAncestorsStack and reports on the
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* original CallExpression.
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* @param {ASTNode} node The CallExpression to check.
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* @returns {boolean} True if the node matches, false if not.
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* @private
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*/
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function checkString(node) {
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if (hasImpliedEvalParent(node)) {
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// remove the entire substack, to avoid duplicate reports
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const substack = impliedEvalAncestorsStack.pop();
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context.report({ node: substack[0], message: "Implied eval. Consider passing a function instead of a string." });
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}
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}
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//--------------------------------------------------------------------------
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// Public
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//--------------------------------------------------------------------------
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return {
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CallExpression(node) {
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if (isImpliedEvalCallExpression(node)) {
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// call expressions create a new substack
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impliedEvalAncestorsStack.push([node]);
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}
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},
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"CallExpression:exit"(node) {
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if (node === last(last(impliedEvalAncestorsStack))) {
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/*
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* Destroys the entire sub-stack, rather than just using
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* last(impliedEvalAncestorsStack).pop(), as a CallExpression is
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* always the bottom of a impliedEvalAncestorsStack substack.
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*/
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impliedEvalAncestorsStack.pop();
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}
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},
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BinaryExpression(node) {
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if (node.operator === "+" && hasImpliedEvalParent(node)) {
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last(impliedEvalAncestorsStack).push(node);
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}
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},
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"BinaryExpression:exit"(node) {
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if (node === last(last(impliedEvalAncestorsStack))) {
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last(impliedEvalAncestorsStack).pop();
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}
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},
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Literal(node) {
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if (typeof node.value === "string") {
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checkString(node);
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}
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},
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TemplateLiteral(node) {
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checkString(node);
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}
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};
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}
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};
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