1 | /**
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2 | * @fileoverview Rule to flag use of implied eval via setTimeout and setInterval
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3 | * @author James Allardice
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4 | * @copyright 2015 Mathias Schreck. All rights reserved.
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5 | * @copyright 2013 James Allardice. All rights reserved.
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6 | */
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7 |
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8 | ;
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9 |
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10 | //------------------------------------------------------------------------------
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11 | // Rule Definition
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12 | //------------------------------------------------------------------------------
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13 |
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14 | module.exports = function(context) {
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15 | var CALLEE_RE = /set(?:Timeout|Interval)|execScript/;
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16 |
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17 | // Figures out if we should inspect a given binary expression. Is a stack of
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18 | // stacks, where the first element in each substack is a CallExpression.
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19 | var impliedEvalAncestorsStack = [];
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20 |
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21 | //--------------------------------------------------------------------------
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22 | // Helpers
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23 | //--------------------------------------------------------------------------
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24 |
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25 | /**
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26 | * Get the last element of an array, without modifying arr, like pop(), but non-destructive.
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27 | * @param {array} arr What to inspect
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28 | * @returns {*} The last element of arr
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29 | * @private
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30 | */
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31 | function last(arr) {
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32 | return arr ? arr[arr.length - 1] : null;
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33 | }
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34 |
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35 | /**
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36 | * Checks if the given MemberExpression node is a potentially implied eval identifier on window.
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37 | * @param {ASTNode} node The MemberExpression node to check.
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38 | * @returns {boolean} Whether or not the given node is potentially an implied eval.
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39 | * @private
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40 | */
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41 | function isImpliedEvalMemberExpression(node) {
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42 | var object = node.object,
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43 | property = node.property,
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44 | hasImpliedEvalName = CALLEE_RE.test(property.name) || CALLEE_RE.test(property.value);
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45 |
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46 | return object.name === "window" && hasImpliedEvalName;
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47 | }
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48 |
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49 | /**
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50 | * Determines if a node represents a call to a potentially implied eval.
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51 | *
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52 | * This checks the callee name and that there's an argument, but not the type of the argument.
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53 | *
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54 | * @param {ASTNode} node The CallExpression to check.
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55 | * @returns {boolean} True if the node matches, false if not.
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56 | * @private
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57 | */
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58 | function isImpliedEvalCallExpression(node) {
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59 | var isMemberExpression = (node.callee.type === "MemberExpression"),
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60 | isIdentifier = (node.callee.type === "Identifier"),
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61 | isImpliedEvalCallee =
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62 | (isIdentifier && CALLEE_RE.test(node.callee.name)) ||
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63 | (isMemberExpression && isImpliedEvalMemberExpression(node.callee));
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64 |
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65 | return isImpliedEvalCallee && node.arguments.length;
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66 | }
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67 |
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68 | /**
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69 | * 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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70 | * @param {ASTNode} node The node to inspect the parent of.
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71 | * @returns {boolean} Was the parent a direct descendent, and is the child therefore potentially part of a dangerous argument?
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72 | * @private
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73 | */
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74 | function hasImpliedEvalParent(node) {
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75 | // make sure our parent is marked
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76 | return node.parent === last(last(impliedEvalAncestorsStack)) &&
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77 | // if our parent is a CallExpression, make sure we're the first argument
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78 | (node.parent.type !== "CallExpression" || node === node.parent.arguments[0]);
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79 | }
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80 |
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81 | /**
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82 | * Checks if our parent is marked as part of an implied eval argument. If
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83 | * so, collapses the top of impliedEvalAncestorsStack and reports on the
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84 | * original CallExpression.
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85 | * @param {ASTNode} node The CallExpression to check.
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86 | * @returns {boolean} True if the node matches, false if not.
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87 | * @private
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88 | */
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89 | function checkString(node) {
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90 | if (hasImpliedEvalParent(node)) {
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91 | // remove the entire substack, to avoid duplicate reports
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92 | var substack = impliedEvalAncestorsStack.pop();
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93 | context.report(substack[0], "Implied eval. Consider passing a function instead of a string.");
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94 | }
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95 | }
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96 |
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97 | //--------------------------------------------------------------------------
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98 | // Public
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99 | //--------------------------------------------------------------------------
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100 |
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101 | return {
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102 | "CallExpression": function(node) {
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103 | if (isImpliedEvalCallExpression(node)) {
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104 | // call expressions create a new substack
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105 | impliedEvalAncestorsStack.push([node]);
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106 | }
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107 | },
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108 |
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109 | "CallExpression:exit": function(node) {
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110 | if (node === last(last(impliedEvalAncestorsStack))) {
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111 | // destroys the entire sub-stack, rather than just using
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112 | // last(impliedEvalAncestorsStack).pop(), as a CallExpression is
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113 | // always the bottom of a impliedEvalAncestorsStack substack.
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114 | impliedEvalAncestorsStack.pop();
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115 | }
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116 | },
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117 |
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118 | "BinaryExpression": function(node) {
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119 | if (node.operator === "+" && hasImpliedEvalParent(node)) {
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120 | last(impliedEvalAncestorsStack).push(node);
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121 | }
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122 | },
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123 |
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124 | "BinaryExpression:exit": function(node) {
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125 | if (node === last(last(impliedEvalAncestorsStack))) {
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126 | last(impliedEvalAncestorsStack).pop();
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127 | }
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128 | },
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129 |
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130 | "Literal": function(node) {
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131 | if (typeof node.value === "string") {
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132 | checkString(node);
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133 | }
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134 | },
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135 |
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136 | "TemplateLiteral": function(node) {
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137 | checkString(node);
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138 | }
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139 | };
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140 |
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141 | };
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142 |
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143 | module.exports.schema = [];
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