I would like to know which http method I should use when doing a login request, and why? Since this request creates an object (a user session) on the server, I think it should be POST, what do you think? But since the login request should be idempotent, it could be PUT, couldn't it?
Same question for a logout request, should I use the DELETE method?
If your login request is via a user supplying a username and password then a POST is preferable, as details will be sent in the HTTP messages body rather than the URL. Although it will still be sent plain text, unless you're encrypting via https.
The HTTP DELETE method is a request to delete something on the server. I don't think that DELETING an in memory user session is really what it's intended; more it's for deleting the user record itself. So potentially logout can be just a GET e.g. www.yoursite.com/logout.
I believe that you can translate LOGIN & LOGOUT methods into basic CRUD operations CREATE & DELETE. Since you are creating a new resource called SESSION and destroying it when logging out:
I would never do LOGOUT as GET just because anyone could make an attack just simply by sending an email with IMG tag or link to website where such an IMG tag exists. (<img src="youtsite.com/logout" />)
P.S. Long time I was wondering how would you create a RESTful login/logout and it turned out it's really simple, you do it just like I described: use /session/ endpoint with CREATE and DELETE methods and you are fine. You could also use UPDATE if you want to update session in one way or another...
Here is my solution based on REST guides and recommendations:
LOGIN - create a resource
Request:
POST => https://example.com/sessions/ BODY => {'login': '[email protected]', 'password': '123456'} Response:
http status code 201 (Created) {'token': '761b69db-ace4-49cd-84cb-4550be231e8f'} LOGOUT - delete a resource
Request:
DELETE => https://example.com/sessions/761b69db-ace4-49cd-84cb-4550be231e8f/ Response:
http status code 204 (No Content) 
For login request we should use POST method. Because our login data is secure which needs security. When use POST method the data is sent to server in a bundle. But in GET method data is sent to the server followed by the url like append with url request which will be seen to everyone.
So For secure authentication and authorization process we should use POST method.
I hope this solution will help you.
Thanks
Regarding the method for logging out:
In the Spring (Java Framework) documentation, they state that a POST request is preferred, since a GET makes you vulnerable to CSRF (Cross-Site Request Forgery) and the user could be logged out.
Adding CSRF will update the LogoutFilter to only use HTTP POST. This ensures that log out requires a CSRF token and that a malicious user cannot forcibly log out your users.
Logging in should also use POST (body can be encrypted, see the other answers).
For Login I use POST, below is my code for LOGIN method I used Nodejs with Express and Mongoose
your router.js const express = require("express"); const router = express.Router(); router.post("/login", login); your controller.js export.login = async(req, res) => { //find the user based on email const {email, password} = req.body; try{ const user = awaitUser.findOne({email}); if(user==null) return res.status(400).json({err : "User with email doesnot exists.Please signup"}); } catch(error){ return res.status(500).json({err : error.message}); } //IF EVERYTHING GOES FINE, ASSIGN YOUR TOKEN make sure you have JWT installed const token = jwt.sign({_id: user._id}, YOUR_SECRET_KEY); res.cookie('t'); const {_id, name, email} = user; return res.json({token, user : {_id, email, name}}); } The login request isn't necessarily idempotent. The token that it generates for downstream services can differ for each successive log ins and you'll still be able to access the authenticated resources.
