tls.Server

class tls.Server extends net.Server

Accepts encrypted connections using TLS or SSL.

This event is emitted when a new TCP stream is established, before the TLS handshake begins. socket is typically an object of type net.Socket but will not receive events unlike the socket created from the net.Server 'connection' event. Usually users will not want to access this event.

This event can also be explicitly emitted by users to inject connections into the TLS server. In that case, any Duplex stream can be passed.

The keylog event is emitted when key material is generated or received by a connection to this server (typically before handshake has completed, but not necessarily). This keying material can be stored for debugging, as it allows captured TLS traffic to be decrypted. It may be emitted multiple times for each socket.

A typical use case is to append received lines to a common text file, which is later used by software (such as Wireshark) to decrypt the traffic:

const logFile = fs.createWriteStream('/tmp/ssl-keys.log', { flags: 'a' });
// ...
server.on('keylog', (line, tlsSocket) => {
  if (tlsSocket.remoteAddress !== '...')
    return; // Only log keys for a particular IP
  logFile.write(line);
});

The 'newSession' event is emitted upon creation of a new TLS session. This may be used to store sessions in external storage. The data should be provided to the 'resumeSession' callback.

The listener callback is passed three arguments when called:

Listening for this event will have an effect only on connections established after the addition of the event listener.

The 'OCSPRequest' event is emitted when the client sends a certificate status request. The listener callback is passed three arguments when called:

The server's current certificate can be parsed to obtain the OCSP URL and certificate ID; after obtaining an OCSP response, callback(null, resp) is then invoked, where resp is a Buffer instance containing the OCSP response. Both certificate and issuer are Buffer DER-representations of the primary and issuer's certificates. These can be used to obtain the OCSP certificate ID and OCSP endpoint URL.

Alternatively, callback(null, null) may be called, indicating that there was no OCSP response.

Calling callback(err) will result in a socket.destroy(err) call.

The typical flow of an OCSP request is as follows:

1. Client connects to the server and sends an 'OCSPRequest' (via the status info extension in ClientHello).
2. Server receives the request and emits the 'OCSPRequest' event, calling the listener if registered.
3. Server extracts the OCSP URL from either the certificate or issuer and performs an OCSP request to the CA.
4. Server receives 'OCSPResponse' from the CA and sends it back to the client via the callback argument
5. Client validates the response and either destroys the socket or performs a handshake.

The issuer can be null if the certificate is either self-signed or the issuer is not in the root certificates list. (An issuer may be provided via the ca option when establishing the TLS connection.)

Listening for this event will have an effect only on connections established after the addition of the event listener.

An npm module like asn1.js may be used to parse the certificates.

The 'resumeSession' event is emitted when the client requests to resume a previous TLS session. The listener callback is passed two arguments when called:

The event listener should perform a lookup in external storage for the sessionData saved by the 'newSession' event handler using the given sessionId. If found, call callback(null, sessionData) to resume the session. If not found, the session cannot be resumed. callback() must be called without sessionData so that the handshake can continue and a new session can be created. It is possible to call callback(err) to terminate the incoming connection and destroy the socket.

Listening for this event will have an effect only on connections established after the addition of the event listener.

The following illustrates resuming a TLS session:

const tlsSessionStore = {};
server.on('newSession', (id, data, cb) => {
  tlsSessionStore[id.toString('hex')] = data;
  cb();
});
server.on('resumeSession', (id, cb) => {
  cb(null, tlsSessionStore[id.toString('hex')] || null);
});

The 'secureConnection' event is emitted after the handshaking process for a new connection has successfully completed. The listener callback is passed a single argument when called:

The tlsSocket.authorized property is a boolean indicating whether the client has been verified by one of the supplied Certificate Authorities for the server. If tlsSocket.authorized is false, then socket.authorizationError is set to describe how authorization failed. Depending on the settings of the TLS server, unauthorized connections may still be accepted.

The tls.TLSSocket.servername and tls.TLSSocket.alpnProtocol properties can be used to check which server name was requested, and which protocol was negotiated.

The 'tlsClientError' event is emitted when an error occurs before a secure connection is established. The listener callback is passed two arguments when called:

server.addContext(hostname, context): void

The server.addContext() method adds a secure context that will be used if the client request's SNI name matches the supplied hostname (or wildcard).

When there are multiple matching contexts, the most recently added one is used.

server.address(): Object

Returns the bound address, the address family name, and port of the server as reported by the operating system. See net.Server.address() for more information.

server.close(callback?): tls.Server

The server.close() method stops the server from accepting new connections.

This function operates asynchronously. The 'close' event will be emitted when the server has no more open connections.

server.getTicketKeys(): Buffer

Returns the session ticket keys.

See Session Resumption for more information.

server.listen(): void

Starts the server listening for encrypted connections. This method is identical to server.listen() from net.Server.

server.setSecureContext(options): void

The server.setSecureContext() method replaces the secure context of an existing server. Existing connections to the server are not interrupted.

server.setTicketKeys(keys): void

Sets the session ticket keys.

Changes to the ticket keys are effective only for future server connections. Existing or currently pending server connections will use the previous keys.

See Session Resumption for more information.