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Merge pull request #60 from amagitechnologies/master
Request to add new rules
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| # detect improper exception handling (detect-improper-exception-handling) | ||
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| Node.js has the process global object, which is an EventEmitter object that in this case emits uncaught exceptions and brought up to the main event loop. In the event that an uncaught exception is thrown while your application is executing, it will result to it crashing. Thus, it is essential to make a listener for uncaught exceptions uwing the process object. There is no need for importing the process core module as it is nautomatically injected with Node.js. | ||
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| It is worth noting that this way of exception handling is intended as a last resort. Moreover, this type of event signals that the application is in an undefined state, and resuming the application is strongly discouraged and can cause greater issues. | ||
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| To not miss any uncaught exception and correctly use it is to do synchronous cleanup of allocated resources such as using handlers, file descriptors, custom loggers and similar before exiting the process with a non-zero exit code. Be aware that in displaying error messages it is recommended to log the necessary details but not as far as leaking detailed information such as stack traces to the user. | ||
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| ### Example | ||
| ```javascript | ||
| process.on("uncaughtException", function(err) { | ||
| // clean up allocated resources | ||
| // log necessary error details to log files | ||
| process.exit(1); // exit the process to avoid unknown state | ||
| }); | ||
| ``` | ||
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| [link 1](https://cheatsheetseries.owasp.org/cheatsheets/Nodejs_Security_Cheat_Sheet.html#handle-uncaughtexception) | ||
| [link 2](https://nodejs.org/dist/latest-v16.x/docs/api/process.html#event-uncaughtexception) | ||
| [link 3](https://nodejs.dev/learn/error-handling-in-nodejs#catching-uncaught-exceptions) |
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| # detect unhandled async errors (detect-unhandled-async-errors) | ||
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| It is impossible to have no errors in your program, even those of the best programmers have one way or another. There are some ways to handle errors in order to find and fix them. | ||
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| ### try-catch method | ||
| ```javascript | ||
| async function userProfile() { | ||
| try { | ||
| let user = await getUser(); | ||
| let friendsOfUser = await getFriendsOfUser(userId); | ||
| let posts = await getUsersPosts(userId); | ||
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| showUserProfilePage(user, friendsOfUser, posts); | ||
| } catch(e) { | ||
| console.log(e); | ||
| } | ||
| } | ||
| ``` | ||
| Your code won't look too good having multiple request handlers each with a try/catch statement. | ||
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| ### .catch method | ||
| The .catch method can be used if we want to know which error comes from which async request. | ||
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| ```javascript | ||
| async function userProfile() { | ||
| let user = await getUser().catch(err => console.error('an error occurred')); | ||
| let friendsOfUser = await getFriendsOfUser(userId).catch(err => console.error('an error occurred')); | ||
| let posts = await getUsersPosts(userId).catch(err => console.error('an error occurred')); | ||
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| showUserProfilePage(user, friendsOfUser, posts); | ||
| } | ||
| ``` | ||
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| ### using a separate error handling function (Recommended) | ||
| With error handler functions. Lessening the need for try-catch blocks and .catch methods. | ||
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| ```javascript | ||
| const handle = (promise) => { | ||
| return promise | ||
| .then(data => ([data, undefined])) | ||
| .catch(error => Promise.resolve([undefined, error])); | ||
| } | ||
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| async function userProfile() { | ||
| let [user, userErr] = await handle(getUser()); | ||
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| if(userErr) throw new Error('Could not fetch user details'); | ||
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| let [friendsOfUser, friendErr] = await handle( | ||
| getFriendsOfUser(userId) | ||
| ); | ||
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| if(friendErr) throw new Error('Could not fetch user\'s friends'); | ||
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| let [posts, postErr] = await handle(getUsersPosts(userId)); | ||
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| if(postErr) throw new Error('Could not fetch user\'s posts'); | ||
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| showUserProfilePage(user, friendsOfUser, posts); | ||
| } | ||
| ``` | ||
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| [link 1](https://cheatsheetseries.owasp.org/cheatsheets/Nodejs_Security_Cheat_Sheet.html#handle-errors-in-asynchronous-calls) | ||
| [link 2](https://dev.to/sobiodarlington/better-error-handling-with-async-await-2e5m) |
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| # detect unhandled error events (detect-unhandled-error-events) | ||
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| When using the EventEmitter, it cannot be denied that errors can occur anywhere in the chain. | ||
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| Given this code below: | ||
| ```javascript | ||
| const EventEmitter = require('events') | ||
| const myEmitter = new EventEmitter() | ||
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| myEmitter.emit('error', new Error('whoops!')) | ||
| // Throws and crashes Node.js | ||
| ``` | ||
| Since there is no error event listener called, the error will be thrown and will be treated as an uncaughtException. Once an error is emitted and unhandled, the Node.js application will crash. | ||
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| There should always be listeners for events at the least. This of course does not count out error events. | ||
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| ```javascript | ||
| const EventEmitter = require('events') | ||
| const myEmitter = new EventEmitter() | ||
| // MUST: include error listener | ||
| myEmitter.on('error', (err) => { | ||
| console.error('An error occurred') | ||
| }) | ||
| myEmitter.emit('error', new Error('whoops!')) | ||
| // Prints: An error occurred | ||
| ``` | ||
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| [link 1](https://nodejs.org/dist/latest-v16.x/docs/api/events.html#error-events) | ||
| [link 2](https://cheatsheetseries.owasp.org/cheatsheets/Nodejs_Security_Cheat_Sheet.html#listen-to-errors-when-using-eventemitter) |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,105 @@ | ||
| /** | ||
| * @fileoverview detect improper exception handling | ||
| * @author PauMacasaet | ||
| */ | ||
| 'use strict' | ||
| const { getDocsUrl } = require('../utils') | ||
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| function isErrCallbackFunc (calleeArg) { | ||
| const functionRegEx = /^(ArrowFunctionExpression|FunctionExpression)$/.test(calleeArg.type) | ||
| return functionRegEx | ||
| } | ||
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| module.exports = { | ||
| meta: { | ||
| type: 'suggestion', | ||
| messages: { | ||
| msg: 'Detect missing callback on unhandled exception', | ||
| msg_no_func_body: 'Detect empty function body', | ||
| msg_no_process_exit: 'Detect missing process.exit()', | ||
| msg_zero_exit_code: 'Detect missing non-zero exit code' | ||
| }, | ||
| docs: { | ||
| description: 'rule that detects improper exception handling', | ||
| category: 'Possible Errors', | ||
| recommended: true, | ||
| url: getDocsUrl('detect-improper-exception-handling') | ||
| }, | ||
| fixable: null | ||
| }, | ||
| create: function (context) { | ||
| return { | ||
| 'CallExpression': function (node) { | ||
| let nodeCallee = node.callee | ||
| if (nodeCallee.hasOwnProperty('object') && | ||
| nodeCallee.hasOwnProperty('property') && | ||
| nodeCallee.type === 'MemberExpression') { | ||
| let objectName = nodeCallee.object.name | ||
| let propertyName = nodeCallee.property.name | ||
| if (objectName === 'process' && propertyName === 'on') { | ||
| if (node.arguments.length > 0) { | ||
| if (node.arguments[0].type === 'Literal' && | ||
| node.arguments[0].value === 'uncaughtException') | ||
| { | ||
| if (node.arguments.length > 1) { | ||
| let calleeArgs = node.arguments | ||
| let callbacks = [] | ||
| for (let arg = 1; arg < calleeArgs.length; arg++) { | ||
| if (calleeArgs[arg].type === 'CallExpression') { | ||
| callbacks.push(calleeArgs[arg].type) | ||
| } | ||
| if (isErrCallbackFunc(calleeArgs[arg])) { | ||
| if (calleeArgs[arg].body.body.length > 0) { | ||
| let functionBody = calleeArgs[arg].body.body | ||
| for (let i in functionBody) { | ||
| if (functionBody[i].type === 'ExpressionStatement') { | ||
| if (functionBody[i].expression.callee.hasOwnProperty('object') | ||
| && functionBody[i].expression.callee.hasOwnProperty('property')) { | ||
| let objectName = functionBody[i].expression.callee.object.name | ||
| let propertyName = functionBody[i].expression.callee.property.name | ||
| let hasArguments = functionBody[i].expression.arguments.length > 0 | ||
| if (objectName === 'process' && propertyName === 'exit' && hasArguments) { | ||
| let exitCode = functionBody[i].expression.arguments[0].value | ||
| if (exitCode === 1) { | ||
| callbacks.push(calleeArgs[arg].type) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| if (callbacks.length === 0) { | ||
| context.report({ | ||
| node: node, | ||
| messageId: 'msg_no_process_exit', | ||
| loc: { | ||
| start: calleeArgs[arg].body.loc.start, | ||
| end: calleeArgs[arg].body.loc.end | ||
| } | ||
| }) | ||
| } | ||
| } else { | ||
| context.report({ | ||
| node: node, | ||
| messageId: 'msg_no_func_body', | ||
| loc: { | ||
| start: calleeArgs[arg].body.loc.start, | ||
| end: calleeArgs[arg].body.loc.end | ||
| } | ||
| }) | ||
| } | ||
| } | ||
| } | ||
| } else { | ||
| context.report({ | ||
| node: node, | ||
| messageId: 'msg' | ||
| }) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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