src: add alpn & sni properties on SocketOptions and SocketInfo

src/index.ts

@@ -73,19 +73,34 @@ export class Socket {
         allowHalfOpen: this.allowHalfOpen,
       };
       if (this.secureTransport === 'on') {
-        this.socket = tls.connect(connectOptions);
+        this.socket = tls.connect({
+          ...connectOptions,
+          ALPNProtocols: options?.alpn,
+          servername: options?.sni,
+        });
       } else {
         this.socket = net.connect(connectOptions);
       }
     } else {
-      this.socket = new tls.TLSSocket(addressOrSocket);
+      this.socket = new tls.TLSSocket(addressOrSocket, {
+        ALPNProtocols: options?.alpn,
+      });
     }
 
     if (this.socket instanceof tls.TLSSocket) {
       this.socket.on('secureConnect', () => {
+        // Typescript doesn't deduce that it can only be TLSSocket in this scope
+        const tlsSocket = this.socket as tls.TLSSocket;
+
+        let alpnProtocol: string | undefined;
+        if (typeof tlsSocket.alpnProtocol === 'string') {
+          alpnProtocol = tlsSocket.alpnProtocol;
+        }
+
         this.openedResolve({
           remoteAddress: this.socket.remoteAddress,
           localAddress: this.socket.localAddress,
+          alpn: alpnProtocol,
         });
       });
     } else {

src/types.ts

@@ -13,6 +13,19 @@ export interface SocketOptions {
    * This option is similar to that offered by the Node.js net module and allows interoperability with code which utilizes it.
    */
   allowHalfOpen?: boolean;
+  /**
+   * The Application-Layer Protocol Negotiation list to send, as an array of strings.
+   * If the server agrees with one of the protocols specified in this list, it will
+   * return the matching protocol in the info property. May be specified if and only
+   * if secureTransport is on or starttls.
+   */
+  alpn?: string[];
+  /**
+   * The Server Name Indication TLS option to send as part of the TLS handshake.
+   * If specified, requests that the server send a certificate with a matching
+   * common name. May be specified if and only if secureTransport is on or starttls.
+   */
+  sni?: string;
 }
 
 export interface SocketAddress {
@@ -25,4 +38,5 @@ export interface SocketAddress {
 export interface SocketInfo {
   remoteAddress?: string;
   localAddress?: string;
+  alpn?: string;
 }

test/tls.test.ts

@@ -5,12 +5,13 @@ import tap from 'tap';
 import { SocketError, connect } from '../src';
 import { listenAndGetSocketAddress, writeAndReadSocket } from './utils';
 
-function getTLSServer(): tls.Server {
+function getTLSServer(alpnProtocols?: string[]): tls.Server {
   const server = tls.createServer({
     key: fs.readFileSync(path.join(__dirname, '/certs/server/server.key')),
     cert: fs.readFileSync(path.join(__dirname, '/certs/server/server.crt')),
     ca: fs.readFileSync(path.join(__dirname, '/certs/ca/ca.crt')),
     rejectUnauthorized: false,
+    ALPNProtocols: alpnProtocols
   });
 
   return server;
@@ -59,6 +60,30 @@ void tap.test('Socket `connect` with TLS', (t) => {
       t.end();
     });
 
+    void t.test('can get correct alpn protocol', async (t) => {
+      const server = getTLSServer(['h2c']);
+      const address = await listenAndGetSocketAddress(server);
+      const socket = connect(
+        address,
+        {
+          secureTransport: 'on',
+          alpn: ['h2c']
+        }
+      );
+      t.throws(
+        () => {
+          socket.startTls();
+        },
+        new SocketError("secureTransport must be set to 'starttls'"),
+        'calling .startTls() throws an error',
+      );
+      const socketInfo = await socket.opened;
+      t.equal(socketInfo.alpn, 'h2c');
+      await socket.close();
+      server.close();
+      t.end();
+    });
+
     t.end();
   });