Securely Access & Expose code-server

Usage

Expose code-server
External authentication
HTTPS and self-signed certificates
Accessing web services

This article will walk you through exposing code-server securely once you've completed the installation process.

Expose code-server

Never expose code-server directly to the internet without some form of authentication and encryption, otherwise someone can take over your machine via the terminal.

By default, code-server uses password authentication. As such, you must copy the password from code-server's config file to log in. To avoid exposing itself unnecessarily, code-server listens on localhost; this practice is fine for testing, but it doesn't work if you want to access code-server from a different machine.

Rate limits: code-server rate limits password authentication attempts to two per minute plus an additional twelve per hour.

There are several approaches to operating and exposing code-server securely:

Port forwarding via SSH
Using Let's Encrypt with Caddy
Using Let's Encrypt with NGINX
Using a self-signed certificate

Port forwarding via SSH

We highly recommend using port forwarding via SSH to access code-server. If you have an SSH server on your remote machine, this approach doesn't require any additional setup at all.

The downside to SSH forwarding, however, is that you can't access code-server when using machines without SSH clients (such as iPads). If this applies to you, we recommend using another method, such as Let's Encrypt instead.

To work properly, your environment should have WebSockets enabled, which code-server uses to communicate between the browser and server.

SSH into your instance and edit the code-server config file to disable password authentication:

# Replaces "auth: password" with "auth: none" in the code-server config.
sed -i.bak 's/auth: password/auth: none/' ~/.config/code-server/config.yaml

Restart code-server:

sudo systemctl restart code-server@$USER

Forward local port 8080 to 127.0.0.1:8080 on the remote instance by running the following command on your local machine:
```
# -N disables executing a remote shell
ssh -N -L 8080:127.0.0.1:8080 [user]@<instance-ip>
```
At this point, you can access code-server by pointing your web browser to http://127.0.0.1:8080.

If you'd like to make the port forwarding via SSH persistent, we recommend using mutagen to do so. Once you've installed mutagen, you can port forward as follows:

# This is the same as the above SSH command, but it runs in the background
# continuously. Be sure to add `mutagen daemon start` to your ~/.bashrc to
# start the mutagen daemon when you open a shell.
mutagen forward create --name=code-server tcp:127.0.0.1:8080 < instance-ip > :tcp:127.0.0.1:8080

Optional, but highly recommended: add the following to ~/.ssh/config so that you can detect bricked SSH connections:
```
Host *
ServerAliveInterval 5
ExitOnForwardFailure yes
```

You can forward your SSH and GPG agent to the instance to securely access GitHub and sign commits without having to copy your keys.

Using Let's Encrypt with Caddy

Using Let's Encrypt is an option if you want to access code-server on an iPad or do not want to use SSH port forwarding.

This option requires that the remote machine be exposed to the internet. Make sure that your instance allows HTTP/HTTPS traffic.
You'll need a domain name (if you don't have one, you can purchase one from Google Domains or the domain service of your choice)). Once you have a domain name, add an A record to your domain that contains your instance's IP address.
Install Caddy:

sudo apt install -y debian-keyring debian-archive-keyring apt-transport-https
curl -1sLf 'https://dl.cloudsmith.io/public/caddy/stable/gpg.key' | sudo gpg --dearmor -o /usr/share/keyrings/caddy-stable-archive-keyring.gpg
curl -1sLf 'https://dl.cloudsmith.io/public/caddy/stable/debian.deb.txt' | sudo tee /etc/apt/sources.list.d/caddy-stable.list
sudo apt update
sudo apt install caddy

Replace /etc/caddy/Caddyfile using sudo so that the file looks like this:
```
mydomain.com {
  reverse_proxy 127.0.0.1:8080
}
```
If you want to serve code-server from a sub-path, you can do so as follows:
```
mydomain.com/code/* {
  uri strip_prefix /code
  reverse_proxy 127.0.0.1:8080
}
```
Remember to replace mydomain.com with your domain name!
Reload Caddy:
```
sudo systemctl reload caddy
```

At this point, you should be able to access code-server via https://mydomain.com.

Using Let's Encrypt with NGINX

This option requires that the remote machine be exposed to the internet. Make sure that your instance allows HTTP/HTTPS traffic.
You'll need a domain name (if you don't have one, you can purchase one from Google Domains or the domain service of your choice)). Once you have a domain name, add an A record to your domain that contains your instance's IP address.

Install NGINX:

sudo apt update
sudo apt install -y nginx certbot python3-certbot-nginx

Update /etc/nginx/sites-available/code-server using sudo with the following configuration:

server {
    listen 80;
    listen [::]:80;
    server_name mydomain.com;

    location / {
      proxy_pass http://localhost:8080/;
      proxy_set_header Host $http_host;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection upgrade;
      proxy_set_header Accept-Encoding gzip;
    }
}

Be sure to replace mydomain.com with your domain name!

Enable the config:

sudo ln -s ../sites-available/code-server /etc/nginx/sites-enabled/code-server
sudo certbot --non-interactive --redirect --agree-tos --nginx -d mydomain.com -m [email protected]

Be sure to replace [email protected] with your actual email.

At this point, you should be able to access code-server via https://mydomain.com.

Using a self-signed certificate

Self signed certificates do not work with iPad; see ./ipad.md for more information.

Before proceeding, we recommend familiarizing yourself with the risks of self-signing a certificate for SSL.

We recommend self-signed certificates as a last resort, since self-signed certificates do not work with iPads and may cause unexpected issues with code-server. You should only proceed with this option if:

You do not want to buy a domain or you cannot expose the remote machine to the internet
You do not want to use port forwarding via SSH

To use a self-signed certificate:

This option requires that the remote machine be exposed to the internet. Make sure that your instance allows HTTP/HTTPS traffic.

SSH into your instance and edit your code-server config file to use a randomly generated self-signed certificate:

# Replaces "cert: false" with "cert: true" in the code-server config.
sed -i.bak 's/cert: false/cert: true/' ~/.config/code-server/config.yaml
# Replaces "bind-addr: 127.0.0.1:8080" with "bind-addr: 0.0.0.0:443" in the code-server config.
sed -i.bak 's/bind-addr: 127.0.0.1:8080/bind-addr: 0.0.0.0:443/' ~/.config/code-server/config.yaml
# Allows code-server to listen on port 443.
sudo setcap cap_net_bind_service=+ep /usr/lib/code-server/lib/node

Restart code-server:

sudo systemctl restart code-server@$USER

At this point, you should be able to access code-server via https://<your-instance-ip>.

If you'd like to avoid the warnings displayed by code-server when using a self-signed certificate, you can use mkcert to create a self-signed certificate that's trusted by your operating system, then pass the certificate to code-server via the cert and cert-key config fields.

TLS 1.3 and Safari

If you will be using Safari and your configuration does not allow anything less than TLS 1.3 you will need to add support for TLS 1.2 since Safari does not support TLS 1.3 for web sockets at the time of writing. If this is the case you should see OSSStatus: 9836 in the browser console.

External authentication

If you want to use external authentication mechanism (e.g., Sign in with Google), you can do this with a reverse proxy such as:

HTTPS and self-signed certificates

For HTTPS, you can use a self-signed certificate by:

Passing in --cert
Passing in an existing certificate by providing the path to --cert and the path to the key with --cert-key

The self signed certificate will be generated to ~/.local/share/code-server/self-signed.crt.

If you pass a certificate to code-server, it will respond to HTTPS requests and redirect all HTTP requests to HTTPS.

You can use Let's Encrypt to get a TLS certificate for free.

Note: if you set proxy_set_header Host $host; in your reverse proxy config, it will change the address displayed in the green section of code-server in the bottom left to show the correct address.

Accessing web services

If you're working on web services and want to access them locally, code-server can proxy to any port using either a subdomain or a subpath, allowing you to securely access these services using code-server's built-in authentication.

Using a subdomain

You will need a DNS entry that points to your server for each port you want to access. You can either set up a wildcard DNS entry for *.<domain> if your domain name registrar supports it, or you can create one for every port you want to access (3000.<domain>, 8080.<domain>, etc).

You should also set up TLS certificates for these subdomains, either using a wildcard certificate for *.<domain> or individual certificates for each port.

To set your domain, start code-server with the --proxy-domain flag:

code-server --proxy-domain <domain>

For instance, if you have code-server exposed on domain.tld and a Python server running on port 8080 of the same machine code-server is running on, you could run code-server with --proxy-domain domain.tld and access the Python server via 8080.domain.tld.

Note that this uses the host header, so ensure your reverse proxy (if you're using one) forwards that information.

Using a subpath

Simply browse to /proxy/<port>/. For instance, if you have code-server exposed on domain.tld and a Python server running on port 8080 of the same machine code-server is running on, you could access the Python server via domain.tld/proxy/8000.

Using your own proxy

You can make extensions and the ports panel use your own proxy by setting VSCODE_PROXY_URI. For example if you set VSCODE_PROXY_URI=https://{{port}}.kyle.dev when an application is detected running on port 3000 of the same machine code-server is running on the ports panel will create a link to https://3000.kyle.dev instead of pointing to the built-in subpath-based proxy.

Note: relative paths are also supported i.e. VSCODE_PROXY_URI=./proxy/{{port}}

Stripping `/proxy/<port>` from the request path

You may notice that the code-server proxy strips /proxy/<port> from the request path.

HTTP servers should use relative URLs to avoid the need to be coupled to the absolute path at which they are served. This means you must use trailing slashes on all paths with subpaths.

This reasoning is why the default behavior is to strip /proxy/<port> from the base path. If your application uses relative URLs and does not assume the absolute path at which it is being served, it will just work no matter what port you decide to serve it off or if you put it in behind code-server or any other proxy.

However, some prefer the cleaner aesthetic of no trailing slashes. Omitting the trailing slashes couples you to the base path, since you cannot use relative redirects correctly anymore. If you're okay with this tradeoff, use /absproxy instead and the path will be passed as is (e.g., /absproxy/3000/my-app-path).

Proxying to create a React app

You must use /absproxy/<port> with create-react-app (see #2565 and #2222 for more information). You will need to inform create-react-app of the path at which you are serving via $PUBLIC_URL and webpack via $WDS_SOCKET_PATH:

PUBLIC_URL=/absproxy/3000 \
  WDS_SOCKET_PATH=$PUBLIC_URL/sockjs-node \
  BROWSER=none yarn start

You should then be able to visit https://my-code-server-address.io/absproxy/3000 to see your app exposed through code-server!

We highly recommend using the subdomain approach instead to avoid this class of issue.

Proxying to a Vue app

Similar to the situation with React apps, you have to make a few modifications to proxy a Vue app.

add vue.config.js
update the values to match this (you can use any free port):

module.exports = {
  devServer: {
    port: 3454,
    sockPath: "sockjs-node",
  },
  publicPath: "/absproxy/3454",
}

access app at <code-server-root>/absproxy/3454 e.g. http://localhost:8080/absproxy/3454

Read more about publicPath in the Vue.js docs

Proxying to an Angular app

In order to use code-server's built-in proxy with Angular, you need to make the following changes in your app:

use <base href="./."> in src/index.html
add --serve-path /absproxy/4200 to ng serve in your package.json

For additional context, see this GitHub Discussion.

Proxying to a Svelte app

In order to use code-server's built-in proxy with Svelte, you need to make the following changes in your app:

Add svelte.config.js if you don't already have one
Update the values to match this (you can use any free port):

const config = {
  kit: {
    paths: {
      base: "/absproxy/5173",
    },
  },
}

Access app at <code-server-root>/absproxy/5173/ e.g. `http://localhost:8080/absproxy/5173/

For additional context, see this Github Issue

Prefixing `/absproxy/<port>` with a path

This is a case where you need to serve an application via absproxy as explained above while serving codeserver itself from a path other than the root in your domain.

For example: http://my-code-server.com/user/123/workspace/my-app. To achieve this result:

Start code server with the switch --abs-proxy-base-path=/user/123/workspace
Follow one of the instructions above for your framework.

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