I have a simple application with Flask and Rest-Plus on backend and VueJS frontend generated by VueCLI 3.
I am trying to set up sessions using Flask-Session but session variables saved in one request are not available in another.
I have tried lots of options but still got nothing.
Here is my vue.config.js:
module.exports = {
devServer: {
public: "localhost:8080",
headers: {
"Access-Control-Allow-Origin": "*",
"Access-Control-Allow-Credentials": "true",
"Access-Control-Allow-Headers": "Content-Type, Authorization, x-id, Content-Length, X-Requested-With",
"Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS"
},
proxy: {
'/api*': {
// Forward frontend dev server request for /api to django dev server
target: 'http://localhost:5000/'
}
}
}
}
In my app.py I have set secret key and cors:
app.secret_key = "super_secret"
CORS(app, automatic_options=True, support_credentials=True)
Also, I have added decorators to my request handlers:
#cross_origin(supports_credentials=True)
def get(self):
And still nothing. In /login i set session['aaa']=1 and in another request i got KeyError.
I run frontend via npm run serve and backend via flask run. Any suggestions?
Solved by adding reverse proxy from flask. I've added it in my app.py so it passes all requests to frontend.
If you will use this solution while development, don't forget to remove this endpoint before deploying to production server.
#app.route('/dev', methods=['GET'])
#app.route('/js/<path:dummy>', methods=['GET'])
def proxy(dummy=None):
if request.method == 'GET':
resp = requests.get(request.base_url.replace('5000', '8080'))
excluded_headers = ['content-encoding', 'content-length', 'transfer-encoding', 'connection']
headers = [(name, value) for (name, value) in resp.raw.headers.items() if name.lower() not in excluded_headers]
response = Response(resp.content, resp.status_code, headers)
return response
Summary
I'm trying to set up an authentication passthrough using Traefik's traefik.frontend.auth.forward.address setting. My main web service has the traefik.frontend.auth.forward.address=login.mydomain.com label on the container. Traefik seems to correctly forward incoming requests intended for mydomain.com to login.mydomain.com, but when the login form is submitted, the POST request gets turned into a GET request before it hits the login service, and the parameters of the original POST request seem to be missing. The user can never log in.
Containers
docker run -d \
-l "traefik.frontend.rule=Host:login.mydomain.com; Method:GET, POST" \
-l "traefik.enable=true" \
login-service
docker run -d \
-l "traefik.frontend.rule=Host:mydomain.com" \
-l "traefik.frontend.auth.forward.address=https://login.mydomain.com" \
-l "traefik.frontend.auth.forward.authResponseHeaders=cookie" \
-l "traefik.enable=true" \
web-service
Question
Using auth.forward.address, should I see the parameters from the original POST request in my login service? Since Traefik turns it into a GET request, where in that request should I be looking for the parameters? Or, perhaps I have misconfigured something? Missing a authResponseHeaders flag maybe?
What Works
Requests to mydomain.com show the login form from login-service, with the URL continuing to show mydomain.com; the redirect to login.mydomain.com is happening behind the scenes, which is correct.
I have also tested the login service by itself, and it seems to work. It hosts a form that submits a POST request to the service, before responding with 200 OK and a Set-Cookie header. In fact, when I go to login.mydomain.com directly, I can login, which sets my cookie, and I can go to mydomain.com and skip the login screen.
What Doesn't Work
When submitting the login form, the POST request hits the login-service (as evidenced by the logs in that service) as a GET request and the data in the POST request appears to be gone. Traefik adds an x-forwarded-method set to POST, but I can't find the data in the original POST request. I need the params from my login form to validate them, and they don't appear to be getting through to the login service.
Traefik Configuration
I don't think anything about my Traefik configuration is relevant here, but I'm including it for completeness.
checkNewVersion = true
logLevel = "DEBUG"
defaultEntryPoints = ["https","http"]
sendAnonymousUsage = true
[api]
dashboard = true
debug = true
[entryPoints]
[entryPoints.http]
address = ":80"
[entryPoints.http.redirect]
entryPoint = "https"
[entryPoints.https]
address = ":443"
[entryPoints.https.tls]
[retry]
[docker]
endpoint = "unix:///var/run/docker.sock"
watch = true
exposedbydefault = false
[acme]
email = "admin#mydomain.com"
storage = "acme.json"
entryPoint = "https"
OnHostRule = true
[acme.httpChallenge]
entryPoint = "http"
I tracked down Traefik's auth forward code. Sure enough, the request body is not passed downstream to the authentication service; only the headers make it that far. So much for default form submit behavior.
To get around this, I reworked my client-side authentication logic to submit a POST request with the credentials in the header instead of the body, set using XMLHttpRequest.setRequestHeader.
There's one more catch needed to make it work. I need to set cookies client-side using the Set-Cookie header returned from the authentication server, but if the server returns a 200 OK when the login is successful, Traefik will immediately pass along the original request to the user's intended destination -- meaning the Set-Cookie header will never make it to the user. What I did to get around this was return a 418 I'm a teapot when the authentication was successful. This allows the Set-Cookie header to make it back to the user's browser so the user's auth token can be set. The client then automatically reloads the intended page, this time with the correct cookie set, and now the auth server returns a 200 OK if it sees a valid cookie for the requested service.
Here's what the client side code looks like:
<form id="form" method="post" action="/">
Username: <input type="text" name="username" />
Password: <input type="password" name="password" />
<input type="submit" value="Submit" />
</form>
<script>
// Override the default form submit behavior.
// Traefik doesn't pass along body as part of proxying to the auth server,
// so the credentials have to be put in the headers instead.
const form = document.getElementById("form");
form.addEventListener('submit', function(event) {
const data = new FormData(form);
var request = new XMLHttpRequest();
request.open("POST", "/", true);
request.setRequestHeader("Auth-Form", new URLSearchParams(data).toString());
request.withCredentials = true;
request.onload = function(e) {
if (request.status == 418) {
window.location = window.location.href;
} else {
alert("Login failed.");
}
};
request.send(data);
event.preventDefault();
}, false);
</script>
I'm leaving this issue open at least until the bounty runs out because I can't imagine that this is the intended way to do this. I'm hoping someone can weigh in on how traefik.frontend.auth.forward.address is supposed to be used. Or, if someone has used another authentication proxy strategy with Traefik, I'm eager to hear about it.
How to share cookies cross origin? More specifically, how to use the Set-Cookie header in combination with the header Access-Control-Allow-Origin?
Here's an explanation of my situation:
I am attempting to set a cookie for an API that is running on localhost:4000 in a web app that is hosted on localhost:3000.
It seems I'm receiving the right response headers in the browser, but unfortunately they have no effect. These are the response headers:
HTTP/1.1 200 OK
Access-Control-Allow-Origin: http://localhost:3000
Vary: Origin, Accept-Encoding
Set-Cookie: token=0d522ba17e130d6d19eb9c25b7ac58387b798639f81ffe75bd449afbc3cc715d6b038e426adeac3316f0511dc7fae3f7; Max-Age=86400; Domain=localhost:4000; Path=/; Expires=Tue, 19 Sep 2017 21:11:36 GMT; HttpOnly
Content-Type: application/json; charset=utf-8
Content-Length: 180
ETag: W/"b4-VNrmF4xNeHGeLrGehNZTQNwAaUQ"
Date: Mon, 18 Sep 2017 21:11:36 GMT
Connection: keep-alive
Furthermore, I can see the cookie under Response Cookies when I inspect the traffic using the Network tab of Chrome's developer tools. Yet, I can't see a cookie being set in in the Application tab under Storage/Cookies. I don't see any CORS errors, so I assume I'm missing something else.
Any suggestions?
Update I:
I'm using the request module in a React-Redux app to issue a request to a /signin endpoint on the server. For the server I use express.
Express server:
res.cookie('token', 'xxx-xxx-xxx', { maxAge: 86400000, httpOnly: true, domain: 'localhost:3000' })
Request in browser:
request.post({ uri: '/signin', json: { userName: 'userOne', password: '123456'}}, (err, response, body) => {
// doing stuff
})
Update II:
I am setting request and response headers now like crazy now, making sure that they are present in both the request and the response. Below is a screenshot. Notice the headers Access-Control-Allow-Credentials, Access-Control-Allow-Headers, Access-Control-Allow-Methods and Access-Control-Allow-Origin. Looking at the issue I found at Axios's github, I'm under the impression that all required headers are now set. Yet, there's still no luck...
Cross site approach
To allow receiving & sending cookies by a CORS request successfully, do the following.
Back-end (server) HTTP header settings:
Set the HTTP header Access-Control-Allow-Credentials value to true.
Make sure the HTTP headers Access-Control-Allow-Origin and Access-Control-Allow-Headers are set. Don't use a wildcard *. When you set the allowed origin make sure to use the entire origin including the scheme, i.e. http is not same as https in CORS.
For more info on setting CORS in express js read the docs here.
Cookie settings:
Cookie settings per Chrome and Firefox update in 2021:
SameSite=None
Secure
When doing SameSite=None, setting Secure is a requirement. See docs on SameSite and on requirement of Secure. Also note that Chrome devtools now have improved filtering and highlighting of problems with cookies in the Network tab and Application tab.
Front-end (client): Set the XMLHttpRequest.withCredentials flag to true, this can be achieved in different ways depending on the request-response library used:
ES6 fetch() This is the preferred method for HTTP. Use credentials: 'include'.
jQuery 1.5.1 Mentioned for legacy purposes. Use xhrFields: { withCredentials: true }.
axios As an example of a popular NPM library. Use withCredentials: true.
Proxy approach
Avoid having to do cross site (CORS) stuff altogether. You can achieve this with a proxy. Simply send all traffic to the same top level domain name and route using DNS (subdomain) and/or load balancing. With Nginx this is relatively little effort.
This approach is a perfect marriage with JAMStack. JAMStack dictates API and Webapp code to be completely decoupled by design. More and more users block 3rd party cookies. If API and Webapp can easily be served on the same host, the 3rd party problem (cross site / CORS) dissolves. Read about JAMStack here or here.
Sidenote
It turned out that Chrome won't set the cookie if the domain contains a port. Setting it for localhost (without port) is not a problem. Many thanks to Erwin for this tip!
Note for Chrome Browser released in 2020.
A future release of Chrome will only deliver cookies with cross-site
requests if they are set with SameSite=None and Secure.
So if your backend server does not set SameSite=None, Chrome will use SameSite=Lax by default and will not use this cookie with { withCredentials: true } requests.
More info https://www.chromium.org/updates/same-site.
Firefox and Edge developers also want to release this feature in the future.
Spec found here: https://datatracker.ietf.org/doc/html/draft-west-cookie-incrementalism-01#page-8
In order for the client to be able to read cookies from cross-origin requests, you need to have:
All responses from the server need to have the following in their header:
Access-Control-Allow-Credentials: true
The client needs to send all requests with withCredentials: true option
In my implementation with Angular 7 and Spring Boot, I achieved that with the following:
Server-side:
#CrossOrigin(origins = "http://my-cross-origin-url.com", allowCredentials = "true")
#Controller
#RequestMapping(path = "/something")
public class SomethingController {
...
}
The origins = "http://my-cross-origin-url.com" part will add Access-Control-Allow-Origin: http://my-cross-origin-url.com to every server's response header
The allowCredentials = "true" part will add Access-Control-Allow-Credentials: true to every server's response header, which is what we need in order for the client to read the cookies
Client-side:
import { HttpInterceptor, HttpXsrfTokenExtractor, HttpRequest, HttpHandler, HttpEvent } from "#angular/common/http";
import { Injectable } from "#angular/core";
import { Observable } from 'rxjs';
#Injectable()
export class CustomHttpInterceptor implements HttpInterceptor {
constructor(private tokenExtractor: HttpXsrfTokenExtractor) {
}
intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
// send request with credential options in order to be able to read cross-origin cookies
req = req.clone({ withCredentials: true });
// return XSRF-TOKEN in each request's header (anti-CSRF security)
const headerName = 'X-XSRF-TOKEN';
let token = this.tokenExtractor.getToken() as string;
if (token !== null && !req.headers.has(headerName)) {
req = req.clone({ headers: req.headers.set(headerName, token) });
}
return next.handle(req);
}
}
With this class you actually inject additional stuff to all your request.
The first part req = req.clone({ withCredentials: true });, is what you need in order to send each request with withCredentials: true option. This practically means that an OPTION request will be send first, so that you get your cookies and the authorization token among them, before sending the actual POST/PUT/DELETE requests, which need this token attached to them (in the header), in order for the server to verify and execute the request.
The second part is the one that specifically handles an anti-CSRF token for all requests. Reads it from the cookie when needed and writes it in the header of every request.
The desired result is something like this:
For express, upgrade your express library to 4.17.1 which is the latest stable version. Then;
In CorsOption: Set origin to your localhost url or your frontend production url and credentials to true
e.g
const corsOptions = {
origin: config.get("origin"),
credentials: true,
};
I set my origin dynamically using config npm module.
Then , in res.cookie:
For localhost: you do not need to set sameSite and secure option at all, you can set httpOnly to true for http cookie to prevent XSS attack and other useful options depending on your use case.
For production environment, you need to set sameSite to none for cross-origin request and secure to true. Remember sameSite works with express latest version only as at now and latest chrome version only set cookie over https, thus the need for secure option.
Here is how I made mine dynamic
res
.cookie("access_token", token, {
httpOnly: true,
sameSite: app.get("env") === "development" ? true : "none",
secure: app.get("env") === "development" ? false : true,
})
Pim's answer is very helpful. In my case, I have to use
Expires / Max-Age: "Session"
If it is a dateTime, even it is not expired, it still won't send the cookie to the backend:
Expires / Max-Age: "Thu, 21 May 2020 09:00:34 GMT"
Hope it is helpful for future people who may meet same issue.
In the latest chrome standard, if CORS requests to bring cookies, it must turn on samesite = none and secure, and the back-end domain name must turn on HTTPS,
frontend
`await axios.post(`your api`, data,{
withCredentials:true,
})
await axios.get(`your api`,{
withCredentials:true,
});`
backend
var corsOptions = {
origin: 'http://localhost:3000', //frontend url
credentials: true}
app.use(cors(corsOptions));
const token=jwt.sign({_id:user_id},process.env.JWT_SECRET,{expiresIn:"7d"});
res.cookie("token",token,{httpOnly:true});
hope it will work.
After more then a day of trying all your suggestions and many more, I surrender.
Chrome just does not accept my cross domain cookies on localhost.
No errors, just silently ignored.
I want to have http only cookies to safer store a token.
So for localhost a proxy sounds like the best way around this. I haven't really tried that.
What I ended up doing, maybe it helps someone.
Backend (node/express/typescript)
set cookie as you normally would
res.status(200).cookie("token", token, cookieOptions)
make a work around for localhost
// if origin localhost
response.setHeader("X-Set-Cookie", response.getHeader("set-cookie") ?? "");
Allow x-set-cookie header in cors
app.use(cors({
//...
exposedHeaders: [
"X-Set-Cookie",
//...
]
}));
Frontend (Axios)
On the Axios response
remove the domain= so it's defaulted.
split multiple cookies and store them locally.
// Localhost cookie work around
const xcookies = response.headers?.["x-set-cookie"];
if(xcookies !== undefined){
xcookies
.replace(/\s+Domain=[^=\s;]+;/g, "")
.split(/,\s+(?=[^=\s]+=[^=\s]+)/)
.forEach((cookie:string) => {
document.cookie = cookie.trim();
});
}
Not ideal, but I can move on with my life again.
In general this is just been made to complicated I think :-(
Update my use case maybe we can resolve it?
It's a heroku server with a custom domain.
According to this article that should be okay
https://devcenter.heroku.com/articles/cookies-and-herokuapp-com
I made an isolated test case but still no joy.
I'm pretty sure I've seen it work in FireFox before but currently nothing seems to work, besides my nasty work around.
Server Side
app.set("trust proxy", 1);
app.get("/cors-cookie", (request: Request, response: Response) => {
// http://localhost:3000
console.log("origin", request.headers?.["origin"]);
const headers = response.getHeaders();
Object.keys(headers).forEach(x => {
response.removeHeader(x);
console.log("remove header ", x, headers[x]);
});
console.log("headers", response.getHeaders());
const expiryOffset = 1*24*60*60*1000; // +1 day
const cookieOptions:CookieOptions = {
path: "/",
httpOnly: true,
sameSite: "none",
secure: true,
domain: "api.xxxx.nl",
expires: new Date(Date.now() + expiryOffset)
}
return response
.status(200)
.header("Access-Control-Allow-Credentials", "true")
.header("Access-Control-Allow-Origin", "http://localhost:3000")
.header("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT")
.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept")
.cookie("test-1", "_1_", cookieOptions)
.cookie("test-2", "_2_", {...cookieOptions, ...{ httpOnly: false }})
.cookie("test-3", "_3_", {...cookieOptions, ...{ domain: undefined }})
.cookie("test-4", "_4_", {...cookieOptions, ...{ domain: undefined, httpOnly: false }})
.cookie("test-5", "_5_", {...cookieOptions, ...{ domain: undefined, sameSite: "lax" }})
.cookie("test-6", "_6_", {...cookieOptions, ...{ domain: undefined, httpOnly: false, sameSite: "lax" }})
.cookie("test-7", "_7_", {...cookieOptions, ...{ domain: "localhost"}}) // Invalid domain
.cookie("test-8", "_8_", {...cookieOptions, ...{ domain: ".localhost"}}) // Invalid domain
.cookie("test-9", "_9_", {...cookieOptions, ...{ domain: "http://localhost:3000"}}) // Invalid domain
.json({
message: "cookie"
});
});
Client side
const response = await axios("https://api.xxxx.nl/cors-cookie", {
method: "get",
withCredentials: true,
headers: {
"Accept": "application/json",
"Content-Type": "application/json",
}
});
Which yields the following reponse
I see the cookies in the Network > request > cookies Tab.
But no cookies under Application > Storage > Cookies nor in document.cookie.
Pim's Answer is very helpful,
But here is an edge case I had gone through,
In my case even though I had set the Access-Control-Allow-Origin to specific origins in BE , In FE I received it as * ; which was not allowed
The problem was, some other person handled the webserver setup,
in that, there was a config to set the Access-Control-* headers which was overriding my headers set from BE application
phew.. took a while to figure it out .
So, if there is mismatches in what you set and what you received, Check your web server configs also.
Hope this would help
for me regarding the sameSite property, after enabling CORS I also add "CookieSameSite = SameSiteMode.None"
to the CookieAuthenticationOptions in the Startup file
app.UseCookieAuthentication(new CookieAuthenticationOptions
{
.....
CookieSameSite = SameSiteMode.None,
.....
}
This is an answer to "Lode Michels" from above regarding CORS cookie with the Heroku server, (and for other cloud providers, like AWS)
The reason your CORS cookie can't be set is because Heroku strip down SSL certificate at Load Balancer, so when you try to set the "secure" cookie at the server, it fails since it's no longer from the secure connection.
You can explicitally specify if the connection is secure, rather than the cookie module examining request.
https://github.com/pillarjs/cookies
with koa, add this:
ctx.cookies.secure = true;
edit: I can't comment on that answer directly due to lower than 50 reputation
This code worked for me
In the backend
Set credentials to true in your corsOptions:
const corsOptions = {
credentials: true,
};
Set cookies before sending requests:
res.cookie('token', 'xxx-xxx-xxx', {
maxAge: 24*60*60*1000, httpOnly: true,
SameSite:"None" })
In the frontend
Request in browser (using axios):
axios.post('uri/signin',
JSON.stringify({ username: 'userOne',
password: '123456'}),.
{withCredentials:true})
.the(result
=>console.log(result?.data))
.catch(err => console.log(err))