Can't reach my Nodejs server anymore / Nginx (Error 502, SSL failed, ...)

Question

I have a ReactJs frontend and NodeJs backend running on DigitalOcean. I changed something (but cant remember what I changed), all was working fine but then I had to restart my server and since then I can’t reach my backend anymore.

I always am getting this error: “Access to fetch at ‘https://nodejs.site.com/apicall’ from origin ‘https:// site.com’ has been blocked by CORS policy: No ‘Access-Control-Allow-Origin’ header is present on the requested resource. If an opaque response serves your needs, set the request’s mode to ‘no-cors’ to fetch the resource with CORS disabled.” Error 502

Nodejs server is running cos I can reach it using ip address (with http).

This is my nginx default config file:

server {
    root /var/www/mysite.com/html/build;
index index.html index.htm index.nginx-debian.html;
server_name mysite.com;
location / {
                            try_files $uri $uri/ /index.html;
    }


listen [::]:443 ssl ipv6only=on; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/mysite.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/mysite.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot}

server {
    server_name nodejs.mysite.com;
    location / {

    proxy_pass https://localhost:8800; #whatever port your app runs on
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection 'upgrade';
    proxy_set_header Host $host;
    proxy_cache_bypass $http_upgrade;}


listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/nodejs.mysite.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/nodejs.mysite.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}

error log from Nginx:

[error] 2034#2034: *146 SSL_do_handshake() failed (SSL: error:0A00010B:SSL routines::wrong version number) while SSL handshaking to upstream, client: 43.224.169.197, server: nodejs.site.com, request: "GET /apicall_id=3 HTTP/1.1", upstream: "https://127.0.0.1:8800/apicall_id=3", host: "nodejs.site.com", referrer: "http://localhost:3000/"

What I have tried already?

adding ‘Access-Control-Allow-Origin …’ to the config file
restarting all services and server …

What is wrong? I hope someone can help me …

edit: status SSH

 Loaded: loaded (/lib/systemd/system/ssh.service; disabled; preset: enabled)
    Drop-In: /etc/systemd/system/ssh.service.d
             └─00-socket.conf
     Active: active (running) since Sun 2023-09-03 10:58:57 UTC; 2h 33min ago
TriggeredBy: ● ssh.socket
       Docs: man:sshd(8)
             man:sshd_config(5)
    Process: 728 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
   Main PID: 739 (sshd)
      Tasks: 1 (limit: 994)
     Memory: 8.7M
        CPU: 612ms
     CGroup: /system.slice/ssh.service
             └─739 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"

Sep 03 13:15:16 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2557]: Invalid user admin from 139.59.78.11 port 42204
Sep 03 13:15:16 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2557]: Connection closed by invalid user admin 139.59.78.11 port 42204 [preauth]
Sep 03 13:24:43 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2664]: Accepted publickey for root from 43.224.169.197 port 22898 ssh2: RSA SHA256:5RBxNOVo/P7toxkvPlA>
Sep 03 13:24:43 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2664]: pam_unix(sshd:session): session opened for user root(uid=0) by (uid=0)
Sep 03 13:24:43 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2664]: pam_env(sshd:session): deprecated reading of user environment enabled
Sep 03 13:26:04 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2661]: fatal: Timeout before authentication for 218.92.0.108 port 40561
Sep 03 13:27:40 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2720]: Received disconnect from 61.177.172.179 port 42231:11:  [preauth]
Sep 03 13:27:40 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2720]: Disconnected from authenticating user root 61.177.172.179 port 42231 [preauth]
Sep 03 13:30:02 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2727]: Invalid user  from 64.62.197.5 port 13793
Sep 03 13:30:06 ubuntu-s-1vcpu-1gb-intel-nyc1-01 sshd[2727]: Connection closed by invalid user  64.62.197.5 port 13793 [preauth]

KFSys · Answer

Heya,

So the SSH is not the issue.

It’s something with the application and nginx.

Your frontend application (ReactJs running on https://site.com) is trying to access your backend server (NodeJs on https://nodejs.site.com), which is a cross-origin request. You must configure your NodeJs backend to allow requests from your frontend domain.

To address the CORS issue in your Node.js backend: If you’re using Express, you can use the cors middleware:

const express = require('express');
const cors = require('cors');

const app = express();

// Add this before your routes
app.use(cors({
  origin: 'https://site.com' // or you can set it to '*' to allow all origins, but it's less secure
}));

// Your routes go here

Ensure that the above configuration is placed before your routes, so it’s applied before processing the routes.

Additionally, add the following into your Nginx config:

add_header 'Access-Control-Allow-Origin' '*'; 
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';

To handle the CORS headers.

Finally, given the error you previously mentioned (SSL_do_handshake() failed), ensure that your Node.js backend is correctly set up to handle SSL, or switch to plain HTTP as suggested.

Question

Can't reach my Nodejs server anymore / Nginx (Error 502, SSL failed, ...)

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