Merge pull request coder#835 from cdr/log-failed-logins

Add failed authentication attempt logger

Author: deansheather

doc/security/code-server.fail2ban.conf

@@ -0,0 +1,15 @@
+# Fail2Ban filter for code-server
+#
+#
+
+[Definition]
+
+
+failregex = ^INFO\s+Failed login attempt\s+{\"password\":\"(\\.|[^"])*\",\"remote_address\":\"<HOST>\"
+
+ignoreregex =
+
+datepattern = "timestamp":{EPOCH}}$
+
+# Author: Dean Sheather
+

doc/security/fail2ban.md

@@ -0,0 +1,42 @@
+# Protecting code-server from bruteforce attempts
+
+code-server outputs all failed login attempts, along with the IP address,
+provided password, user agent and timestamp by default. When using a reverse
+proxy such as Nginx or Apache, the remote address may appear to be `127.0.0.1`
+or a similar address unless the `--trust-proxy` argument is provided to
+code-server.
+
+When used with the `--trust-proxy` argument, code-server will use the last IP in
+`X-Forwarded-For` (if provided) instead of the remote socket address. Ensure
+that you are setting this value in your reverse proxy:
+
+Nginx:
+```
+location / {
+	...
+	proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+	...
+}
+```
+
+Apache:
+```
+<VirtualEnv>
+	...
+	SetEnvIf X-Forwarded-For "^.*\..*\..*\..*" forwarded
+	...
+</VirtualEnv>
+```
+
+It is extremely important that if you enable `--trust-proxy` you ensure your
+code-server instance is not accessible from the internet (block it in your
+firewall).
+
+## Fail2Ban
+
+Fail2Ban allows for automatically banning and logging repeated failed
+authentication attempts for many applications through regex filters. A working
+filter for code-server can be found in `./code-server.fail2ban.conf`. Once this
+is installed and configured correctly, repeated failed login attempts should
+automatically be banned from connecting to your server.
+

doc/self-hosted/index.md

@@ -38,21 +38,24 @@ Usage: code-server [options]
 Run VS Code on a remote server.
 
 Options:
-  -V, --version               output the version number
+  -V, --version                         output the version number
   --cert <value>
   --cert-key <value>
-  -e, --extensions-dir <dir>  Set the root path for extensions.
-  -d, --user-data-dir <dir>   Specifies the directory that user data is kept in, useful when running as root.
-  --data-dir <value>          DEPRECATED: Use '--user-data-dir' instead. Customize where user-data is stored.
-  -h, --host <value>          Customize the hostname. (default: "0.0.0.0")
-  -o, --open                  Open in the browser on startup.
-  -p, --port <number>         Port to bind on. (default: 8443)
-  -N, --no-auth               Start without requiring authentication.
-  -H, --allow-http            Allow http connections.
-  -P, --password <value>      Specify a password for authentication.
-  --disable-telemetry         Disables ALL telemetry.
-  --help                      output usage information
-  ```
+  -e, --extensions-dir <dir>            Override the main default path for user extensions.
+  --extra-extensions-dir [dir]          Path to an extra user extension directory (repeatable). (default: [])
+  --extra-builtin-extensions-dir [dir]  Path to an extra built-in extension directory (repeatable). (default: [])
+  -d, --user-data-dir <dir>             Specifies the directory that user data is kept in, useful when running as root.
+  -h, --host <value>                    Customize the hostname. (default: "0.0.0.0")
+  -o, --open                            Open in the browser on startup.
+  -p, --port <number>                   Port to bind on. (default: 8443)
+  -N, --no-auth                         Start without requiring authentication.
+  -H, --allow-http                      Allow http connections.
+  --disable-telemetry                   Disables ALL telemetry.
+  --socket <value>                      Listen on a UNIX socket. Host and port will be ignored when set.
+  --trust-proxy                         Trust the X-Forwarded-For header, useful when using a reverse proxy.
+  --install-extension <value>           Install an extension by its ID.
+  -h, --help                            output usage information
+```
 
   ### Data Directory
   Use `code-server -d (path/to/directory)` or `code-server --user-data-dir=(path/to/directory)`, excluding the parentheses to specify the root folder that VS Code will start in.
@@ -79,23 +82,23 @@ Options:
 > To ensure the connection between you and your server is encrypted view our guide on [securing your setup](../security/ssl.md)
 
   ### Nginx Reverse Proxy
-  Nginx is for reverse proxy. Below is a virtual host example that works with code-server. Please also pass --allow-http. You can also use certbot by EFF to get a ssl certificates for free.
+  Below is a virtual host example that works with code-server. Please also pass `--allow-http` and `--trust-proxy` to code-server to allow the proxy to connect. You can also use Let's Encrypt to get a SSL certificates for free.
   ```
   server {
     listen 80;
     listen [::]:80;
     server_name code.example.com code.example.org;
-      location / {
-         proxy_pass http://localhost:8443/;
-         proxy_set_header Upgrade $http_upgrade;
-         proxy_set_header Connection upgrade;
-         proxy_set_header Accept-Encoding gzip;
-      }
-   }
+    location / {
+       proxy_pass http://localhost:8443/;
+       proxy_set_header Upgrade $http_upgrade;
+       proxy_set_header Connection upgrade;
+       proxy_set_header Accept-Encoding gzip;
+    }
+  }
   ```
 
   ### Apache Reverse Proxy
-  Example of https virtualhost configuration for Apache as a reverse proxy. Please also pass --allow-http on code-server startup to allow the proxy to connect.
+  Example of a HTTPS virtualhost configuration for Apache as a reverse proxy. Please also pass `--allow-http` and `--trust-proxy` to code-server to allow the proxy to connect. You can also use Let's Encrypt to get a SSL certificates for free.
   ```
   <VirtualHost *:80>
     ServerName code.example.com

packages/server/src/cli.ts

@@ -38,6 +38,7 @@ commander.version(process.env.VERSION || "development")
 	.option("-P, --password <value>", "DEPRECATED: Use the PASSWORD environment variable instead. Specify a password for authentication.")
 	.option("--disable-telemetry", "Disables ALL telemetry.", false)
 	.option("--socket <value>", "Listen on a UNIX socket. Host and port will be ignored when set.")
+	.option("--trust-proxy", "Trust the X-Forwarded-For header, useful when using a reverse proxy.", false)
 	.option("--install-extension <value>", "Install an extension by its ID.")
 	.option("--bootstrap-fork <name>", "Used for development. Never set.")
 	.option("--extra-args <args>", "Used for development. Never set.")
@@ -74,6 +75,7 @@ const bold = (text: string | number): string | number => {
 		readonly cert?: string;
 		readonly certKey?: string;
 		readonly socket?: string;
+		readonly trustProxy?: boolean;
 
 		readonly installExtension?: string;
 
@@ -273,6 +275,7 @@ const bold = (text: string | number): string | number => {
 			},
 		},
 		password,
+		trustProxy: options.trustProxy,
 		httpsOptions: hasCustomHttps ? {
 			key: certKeyData,
 			cert: certData,

packages/server/src/server.ts

@@ -31,6 +31,7 @@ interface CreateAppOptions {
 	httpsOptions?: https.ServerOptions;
 	allowHttp?: boolean;
 	bypassAuth?: boolean;
+	trustProxy?: boolean;
 }
 
 export const createApp = async (options: CreateAppOptions): Promise<{
@@ -62,6 +63,21 @@ export const createApp = async (options: CreateAppOptions): Promise<{
 		return true;
 	};
 
+	const remoteAddress = (req: http.IncomingMessage): string | void => {
+		let xForwardedFor = req.headers["x-forwarded-for"];
+		if (Array.isArray(xForwardedFor)) {
+			xForwardedFor = xForwardedFor.join(", ");
+		}
+
+		if (options.trustProxy && xForwardedFor !== undefined) {
+			const addresses = xForwardedFor.split(",").map(s => s.trim());
+
+			return addresses.pop();
+		}
+
+		return req.socket.remoteAddress;
+	};
+
 	const isAuthed = (req: http.IncomingMessage): boolean => {
 		try {
 			if (!options.password || options.bypassAuth) {
@@ -70,7 +86,22 @@ export const createApp = async (options: CreateAppOptions): Promise<{
 
 			// Try/catch placed here just in case
 			const cookies = parseCookies(req);
-			if (cookies.password && safeCompare(cookies.password, options.password)) {
+			if (cookies.password) {
+				if (!safeCompare(cookies.password, options.password)) {
+					let userAgent = req.headers["user-agent"];
+					let timestamp = Math.floor(new Date().getTime() / 1000);
+					if (Array.isArray(userAgent)) {
+						userAgent = userAgent.join(", ");
+					}
+					logger.info("Failed login attempt",
+						field("password", cookies.password),
+						field("remote_address", remoteAddress(req)),
+						field("user_agent", userAgent),
+						field("timestamp", timestamp));
+
+					return false;
+				}
+
 				return true;
 			}
 		} catch (ex) {
@@ -214,7 +245,9 @@ export const createApp = async (options: CreateAppOptions): Promise<{
 	const staticGzip = expressStaticGzip(path.join(baseDir, "build/web"));
 
 	app.use((req, res, next) => {
-		logger.trace(`\u001B[1m${req.method} ${res.statusCode} \u001B[0m${req.originalUrl}`, field("host", req.hostname), field("ip", req.ip));
+		logger.trace(`\u001B[1m${req.method} ${res.statusCode} \u001B[0m${req.originalUrl}`,
+			field("host", req.hostname),
+			field("remote_address", remoteAddress(req)));
 
 		// Force HTTPS unless allowing HTTP.
 		if (!isEncrypted(req.socket) && !options.allowHttp) {