nodejs/doc/api/tls.md

TLS (SSL)

Stability: 2 - Stable

Use require('tls') to access this module.

The tls module uses OpenSSL to provide Transport Layer Security and/or Secure Socket Layer: encrypted stream communication.

TLS/SSL is a public/private key infrastructure. Each client and each server must have a private key. A private key is created like this:

openssl genrsa -out ryans-key.pem 2048

All servers and some clients need to have a certificate. Certificates are public keys signed by a Certificate Authority or self-signed. The first step to getting a certificate is to create a "Certificate Signing Request" (CSR) file. This is done with:

openssl req -new -sha256 -key ryans-key.pem -out ryans-csr.pem

To create a self-signed certificate with the CSR, do this:

openssl x509 -req -in ryans-csr.pem -signkey ryans-key.pem -out ryans-cert.pem

Alternatively you can send the CSR to a Certificate Authority for signing.

For Perfect Forward Secrecy, it is required to generate Diffie-Hellman parameters:

openssl dhparam -outform PEM -out dhparam.pem 2048

To create a .pfx or .p12, do this:

openssl pkcs12 -export -in agent5-cert.pem -inkey agent5-key.pem \
      -certfile ca-cert.pem -out agent5.pfx

• in: certificate
• inkey: private key
• certfile: all CA certs concatenated in one file like cat ca1-cert.pem ca2-cert.pem > ca-cert.pem

ALPN, NPN and SNI

ALPN (Application-Layer Protocol Negotiation Extension), NPN (Next Protocol Negotiation) and, SNI (Server Name Indication) are TLS handshake extensions:

• ALPN/NPN - Allows the use of one TLS server for multiple protocols (HTTP, SPDY, HTTP/2)
• SNI - Allows the use of one TLS server for multiple hostnames with different SSL certificates.

Client-initiated renegotiation attack mitigation

The TLS protocol lets the client renegotiate certain aspects of the TLS session. Unfortunately, session renegotiation requires a disproportionate amount of server-side resources, which makes it a potential vector for denial-of-service attacks.

To mitigate this, renegotiation is limited to three times every 10 minutes. An error is emitted on the tls.TLSSocket instance when the threshold is exceeded. These limits are configurable:

• tls.CLIENT_RENEG_LIMIT: renegotiation limit, default is 3.

• tls.CLIENT_RENEG_WINDOW: renegotiation window in seconds, default is 10 minutes.

Do not change the defaults without a full understanding of the implications.

To test the server, connect to it with openssl s_client -connect address:port and tap R<CR> (i.e., the letter R followed by a carriage return) a few times.

Modifying the Default TLS Cipher suite

Node.js is built with a default suite of enabled and disabled TLS ciphers. Currently, the default cipher suite is:

ECDHE-RSA-AES128-GCM-SHA256:
ECDHE-ECDSA-AES128-GCM-SHA256:
ECDHE-RSA-AES256-GCM-SHA384:
ECDHE-ECDSA-AES256-GCM-SHA384:
DHE-RSA-AES128-GCM-SHA256:
ECDHE-RSA-AES128-SHA256:
DHE-RSA-AES128-SHA256:
ECDHE-RSA-AES256-SHA384:
DHE-RSA-AES256-SHA384:
ECDHE-RSA-AES256-SHA256:
DHE-RSA-AES256-SHA256:
HIGH:
!aNULL:
!eNULL:
!EXPORT:
!DES:
!RC4:
!MD5:
!PSK:
!SRP:
!CAMELLIA

This default can be overriden entirely using the --tls-cipher-list command line switch. For instance, the following makes ECDHE-RSA-AES128-GCM-SHA256:!RC4 the default TLS cipher suite:

node --tls-cipher-list="ECDHE-RSA-AES128-GCM-SHA256:!RC4"

Note that the default cipher suite included within Node.js has been carefully selected to reflect current security best practices and risk mitigation. Changing the default cipher suite can have a significant impact on the security of an application. The --tls-cipher-list switch should by used only if absolutely necessary.

Perfect Forward Secrecy

The term "Forward Secrecy" or "Perfect Forward Secrecy" describes a feature of key-agreement (i.e., key-exchange) methods. Practically it means that even if the private key of a server is compromised, communication can only be decrypted by eavesdroppers if they manage to obtain the key-pair specifically generated for each session.

This is achieved by randomly generating a key pair for key-agreement on every handshake (in contrast to using the same key for all sessions). Methods implementing this technique, thus offering Perfect Forward Secrecy, are called "ephemeral".

Currently two methods are commonly used to achieve Perfect Forward Secrecy (note the character "E" appended to the traditional abbreviations):

• DHE - An ephemeral version of the Diffie Hellman key-agreement protocol.
• ECDHE - An ephemeral version of the Elliptic Curve Diffie Hellman key-agreement protocol.

Ephemeral methods may have some performance drawbacks, because key generation is expensive.

Class: CryptoStream

Stability: 0 - Deprecated: Use [`tls.TLSSocket`][] instead.

This is an encrypted stream.

cryptoStream.bytesWritten

A proxy to the underlying socket's bytesWritten accessor, this will return the total bytes written to the socket, including the TLS overhead.

Class: SecurePair

Returned by tls.createSecurePair.

Event: 'secure'

This event is emitted from the SecurePair once the pair has successfully established a secure connection.

As with checking for the server secureConnection event, pair.cleartext.authorized should be inspected to confirm whether the certificate used is properly authorized.

Class: tls.Server

This class is a subclass of net.Server and has the same methods on it. Instead of accepting only raw TCP connections, this accepts encrypted connections using TLS or SSL.

Event: 'tlsClientError'

function (exception, tlsSocket) { }

When a client connection emits an 'error' event before a secure connection is established it will be forwarded here.

tlsSocket is the tls.TLSSocket that the error originated from.

Event: 'newSession'

function (sessionId, sessionData, callback) { }

Emitted on creation of a TLS session. May be used to store sessions in external storage. callback must be invoked eventually, otherwise no data will be sent or received from the secure connection.

NOTE: adding this event listener will only have an effect on connections established after the addition of the event listener.

Event: 'OCSPRequest'

function (certificate, issuer, callback) { }

Emitted when the client sends a certificate status request. 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. Both certificate and issuer are Buffer DER-representations of the primary and issuer's certificates. They can be used to obtain the OCSP certificate ID and OCSP endpoint URL.

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

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

Typical flow:

1. Client connects to the server and sends an 'OCSPRequest' to it (via status info extension in ClientHello).
2. Server receives the request and invokes the 'OCSPRequest' event listener if present.
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.

NOTE: issuer could be null if the certificate is self-signed or if the issuer is not in the root certificates list. (An issuer may be provided via the ca option.)

NOTE: adding this event listener will only have an effect on connections established after the addition of the event listener.

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

Event: 'resumeSession'

function (sessionId, callback) { }

Emitted when the client wants to resume the previous TLS session. The event listener may perform a lookup in external storage using the given sessionId and invoke callback(null, sessionData) once finished. If the session can't be resumed (i.e., doesn't exist in storage) one may call callback(null, null). Calling callback(err) will terminate incoming connection and destroy the socket.

NOTE: adding this event listener will only have an effect on connections established after the addition of the event listener.

Here's an example for using TLS session resumption:

var 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);
});

Event: 'secureConnection'

function (tlsSocket) {}

This event is emitted after the handshaking process for a new connection has successfully completed. The argument is an instance of tls.TLSSocket and has all the common stream methods and events.

socket.authorized is a boolean value which indicates if the client has been verified by one of the supplied certificate authorities for the server. If socket.authorized is false, then socket.authorizationError is set to describe how authorization failed. Implied but worth mentioning: depending on the settings of the TLS server, unauthorized connections may be accepted.

socket.npnProtocol is a string containing the selected NPN protocol and socket.alpnProtocol is a string containing the selected ALPN protocol. When both NPN and ALPN extensions are received, ALPN takes precedence over NPN and the next protocol is selected by ALPN. When ALPN has no selected protocol, this returns false.

socket.servername is a string containing the server name requested with SNI.

server.addContext(hostname, context)

Add secure context that will be used if the client request's SNI hostname matches the supplied hostname (wildcards can be used). context can contain key, cert, ca or any other properties from tls.createSecureContext() options argument.

server.address()

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])

Stops the server from accepting new connections. This function is asynchronous, the server is finally closed when the server emits a 'close' event. Optionally, you can pass a callback to listen for the 'close' event.

server.connections

The number of concurrent connections on the server.

server.getTicketKeys()

Returns a Buffer instance holding the keys currently used for encryption/decryption of the TLS Session Tickets

server.listen(port[, hostname][, callback])

Begin accepting connections on the specified port and hostname. If the hostname is omitted, the server will accept connections on any IPv6 address (::) when IPv6 is available, or any IPv4 address (0.0.0.0) otherwise. A port value of zero will assign a random port.

This function is asynchronous. The last parameter callback will be called when the server has been bound.

See net.Server for more information.

server.setTicketKeys(keys)

Updates the keys for encryption/decryption of the TLS Session Tickets.

NOTE: the buffer should be 48 bytes long. See ticketKeys option in tls.createServer for more information on how it is used.

NOTE: the change is effective only for future server connections. Existing or currently pending server connections will use the previous keys.

server.maxConnections

Set this property to reject connections when the server's connection count exceeds the specified threshold.

Class: tls.TLSSocket

This is a wrapped version of net.Socket that does transparent encryption of written data and all required TLS negotiation.

This instance implements the duplex Stream interface. It has all the common stream methods and events.

Methods that return TLS connection metadata (e.g. tls.TLSSocket.getPeerCertificate() will only return data while the connection is open.

new tls.TLSSocket(socket[, options])

Construct a new TLSSocket object from an existing TCP socket.

socket is an instance of net.Socket

options is an optional object that might contain following properties:

• secureContext: An optional TLS context object from tls.createSecureContext()

• isServer: If true the TLS socket will be instantiated in server-mode. Default: false

• server: An optional net.Server instance

• requestCert: Optional, see tls.createSecurePair()

• rejectUnauthorized: Optional, see tls.createSecurePair()

• NPNProtocols: Optional, see tls.createServer()

• ALPNProtocols: Optional, see tls.createServer()

• SNICallback: Optional, see tls.createServer()

• session: Optional, a Buffer instance, containing a TLS session

• requestOCSP: Optional, if true the OCSP status request extension will be added to the client hello and an 'OCSPResponse' event will be emitted on the socket before establishing a secure communication

Event: 'OCSPResponse'

function (response) { }

This event will be emitted if the requestOCSP option was set. response is a Buffer containing the server's OCSP response.

Traditionally, the response is a signed object from the server's CA that contains information about server's certificate revocation status.

Event: 'secureConnect'

This event is emitted after the handshaking process for a new connection has successfully completed. The listener will be called regardless of whether or not the server's certificate has been authorized. It is the user's responsibility to test tlsSocket.authorized to see if the server certificate was signed by one of the specified CAs. If tlsSocket.authorized === false then the error can be found in tlsSocket.authorizationError. Also, if either ALPN or NPN was used tlsSocket.alpnProtocol or tlsSocket.npnProtocol can be checked for the negotiated protocol.

tlsSocket.address()

Returns the bound address, the address family name, and port of the underlying socket as reported by the operating system. Returns an object with three properties, e.g., { port: 12346, family: 'IPv4', address: '127.0.0.1' }

tlsSocket.authorized

A boolean that is true if the peer certificate was signed by one of the specified CAs, otherwise false.

tlsSocket.authorizationError

The reason why the peer's certificate has not been verified. This property becomes available only when tlsSocket.authorized === false.

tlsSocket.encrypted

Static boolean value, always true. May be used to distinguish TLS sockets from regular ones.

tlsSocket.getCipher()

Returns an object representing the cipher name and the SSL/TLS protocol version that first defined the cipher.

Example: { name: 'AES256-SHA', version: 'TLSv1/SSLv3' }

See SSL_CIPHER_get_name() and SSL_CIPHER_get_version() in https://www.openssl.org/docs/manmaster/ssl/SSL_CIPHER_get_name.html for more information.

tlsSocket.getEphemeralKeyInfo()

Returns an object representing the type, name, and size of parameter of an ephemeral key exchange in Perfect Forward Secrecy on a client connection. It returns an empty object when the key exchange is not ephemeral. As this is only supported on a client socket, it returns null if called on a server socket. The supported types are 'DH' and 'ECDH'. The name property is only available in 'ECDH'.

Example:

{ type: 'ECDH', name: 'prime256v1', size: 256 }

tlsSocket.getPeerCertificate([ detailed ])

Returns an object representing the peer's certificate. The returned object has some properties corresponding to the fields of the certificate. If the detailed argument is true the full chain with the issuer property will be returned, if false only the top certificate without the issuer property.

Example:

{ subject:
   { C: 'UK',
     ST: 'Acknack Ltd',
     L: 'Rhys Jones',
     O: 'node.js',
     OU: 'Test TLS Certificate',
     CN: 'localhost' },
  issuerInfo:
   { C: 'UK',
     ST: 'Acknack Ltd',
     L: 'Rhys Jones',
     O: 'node.js',
     OU: 'Test TLS Certificate',
     CN: 'localhost' },
  issuer:
   { ... another certificate ... },
  raw: < RAW DER buffer >,
  valid_from: 'Nov 11 09:52:22 2009 GMT',
  valid_to: 'Nov  6 09:52:22 2029 GMT',
  fingerprint: '2A:7A:C2:DD:E5:F9:CC:53:72:35:99:7A:02:5A:71:38:52:EC:8A:DF',
  serialNumber: 'B9B0D332A1AA5635' }

If the peer does not provide a certificate, it returns null or an empty object.

tlsSocket.getProtocol()

Returns a string containing the negotiated SSL/TLS protocol version of the current connection. 'unknown' will be returned for connected sockets that have not completed the handshaking process. null will be returned for server sockets or disconnected client sockets.

Examples:

'SSLv3'
'TLSv1'
'TLSv1.1'
'TLSv1.2'
'unknown'

See https://www.openssl.org/docs/manmaster/ssl/SSL_get_version.html for more information.

tlsSocket.getSession()

Returns the ASN.1 encoded TLS session or undefined if none was negotiated. Could be used to speed up handshake establishment when reconnecting to the server.

tlsSocket.getTLSTicket()

NOTE: Works only with client TLS sockets. Useful only for debugging, for session reuse provide session option to tls.connect().

Returns the TLS session ticket or undefined if none was negotiated.

tlsSocket.localAddress

The string representation of the local IP address.

tlsSocket.localPort

The numeric representation of the local port.

tlsSocket.remoteAddress

The string representation of the remote IP address. For example, '74.125.127.100' or '2001:4860:a005::68'.

tlsSocket.remoteFamily

The string representation of the remote IP family. 'IPv4' or 'IPv6'.

tlsSocket.remotePort

The numeric representation of the remote port. For example, 443.

tlsSocket.renegotiate(options, callback)

Initiate TLS renegotiation process. The options object may contain the following fields: rejectUnauthorized, requestCert. (See [tls.createServer ()][] for details.) callback(err) will be executed with null as err, once the renegotiation is successfully completed.

NOTE: Can be used to request peer's certificate after the secure connection has been established.

ANOTHER NOTE: When running as the server, socket will be destroyed with an error after handshakeTimeout timeout.

tlsSocket.setMaxSendFragment(size)

Set maximum TLS fragment size (default and maximum value is: 16384, minimum is: 512). Returns true on success, false otherwise.

Smaller fragment sizes decrease the buffering latency on the client: larger fragments are buffered by the TLS layer until the entire fragment is received and its integrity is verified; large fragments can span multiple roundtrips and their processing can be delayed due to packet loss or reordering. However, smaller fragments add extra TLS framing bytes and CPU overhead, which may decrease overall server throughput.

tls.connect(options[, callback])

tls.connect(port[, host][, options][, callback])

Creates a new client connection to the given port and host (old API) or options.port and options.host. (If host is omitted, it defaults to localhost.) options should be an object which specifies:

• host: Host the client should connect to.

• port: Port the client should connect to.

• socket: Establish secure connection on a given socket rather than creating a new socket. If this option is specified, host and port are ignored.

• path: Creates unix socket connection to path. If this option is specified, host and port are ignored.

• pfx: A string or Buffer containing the private key, certificate, and CA certs of the client in PFX or PKCS12 format.

• key: A string, Buffer, array of strings, or array of Buffers containing the private key of the client in PEM format.

• passphrase: A string containing the passphrase for the private key or pfx.

• cert: A string, Buffer, array of strings, or array of Buffers containing the certificate key of the client in PEM format.

• ca: A string, Buffer, array of strings, or array of Buffers of trusted certificates in PEM format. If this is omitted several well known "root" CAs (like VeriSign) will be used. These are used to authorize connections.

• ciphers: A string describing the ciphers to use or exclude, separated by :. Uses the same default cipher suite as tls.createServer().

• rejectUnauthorized: If true, the server certificate is verified against the list of supplied CAs. An 'error' event is emitted if verification fails; err.code contains the OpenSSL error code. Default: true.

• NPNProtocols: An array of strings or Buffers containing supported NPN protocols. Buffers should have the following format: 0x05hello0x05world, where the first byte is the next protocol name's length. (Passing an array is usually be much simpler: ['hello', 'world'].)

• ALPNProtocols: An array of strings or Buffers containing the supported ALPN protocols. Buffers should have following format: 0x05hello0x05world, where the first byte is the next protocol name's length. (Passing an array is usually be much simpler: ['hello', 'world'].)

• servername: Server name for the SNI (Server Name Indication) TLS extension.

• checkServerIdentity(servername, cert): Provide an override for checking the server's hostname against the certificate. Should return an error if verification fails. Returns undefined if passing.

• secureProtocol: The SSL method to use, e.g., SSLv3_method to force SSL version 3. The possible values depend on the version of OpenSSL installed in the environment and are defined in the constant SSL_METHODS.

• secureContext: An optional TLS context object from tls.createSecureContext( ... ). It can be used for caching client certificates, keys, and CA certificates.

• session: A Buffer instance, containing TLS session.

• minDHSize: Minimum size of the DH parameter in bits to accept a TLS connection. When a server offers a DH parameter with a size less than this, the TLS connection is destroyed and an error is thrown. Default: 1024.

The callback parameter will be added as a listener for the 'secureConnect' event.

tls.connect() returns a tls.TLSSocket object.

Here is an example of a client of echo server as described previously:

const tls = require('tls');
const fs = require('fs');

const options = {
  // These are necessary only if using the client certificate authentication
  key: fs.readFileSync('client-key.pem'),
  cert: fs.readFileSync('client-cert.pem'),

  // This is necessary only if the server uses the self-signed certificate
  ca: [ fs.readFileSync('server-cert.pem') ]
};

var socket = tls.connect(8000, options, () => {
  console.log('client connected',
              socket.authorized ? 'authorized' : 'unauthorized');
  process.stdin.pipe(socket);
  process.stdin.resume();
});
socket.setEncoding('utf8');
socket.on('data', (data) => {
  console.log(data);
});
socket.on('end', () => {
  server.close();
});

Or

const tls = require('tls');
const fs = require('fs');

const options = {
  pfx: fs.readFileSync('client.pfx')
};

var socket = tls.connect(8000, options, () => {
  console.log('client connected',
              socket.authorized ? 'authorized' : 'unauthorized');
  process.stdin.pipe(socket);
  process.stdin.resume();
});
socket.setEncoding('utf8');
socket.on('data', (data) => {
  console.log(data);
});
socket.on('end', () => {
  server.close();
});

tls.createSecureContext(options)

Creates a credentials object; the options object may contain the following fields:

• pfx : A string or Buffer holding the PFX or PKCS12 encoded private key, certificate, and CA certificates.
• key: A string or Buffer containing the private key of the server in PEM format. To support multiple keys using different algorithms, an array can be provided. It can either be a plain array of keys or an array of objects in the format {pem: key, passphrase: passphrase}. (Required)
• passphrase : A string containing the passphrase for the private key or pfx.
• cert : A string containing the PEM encoded certificate
• ca: A string, Buffer, array of strings, or array of Buffers of trusted certificates in PEM format. If this is omitted several well known "root" CAs (like VeriSign) will be used. These are used to authorize connections.
• crl : Either a string or list of strings of PEM encoded CRLs (Certificate Revocation List).
• ciphers: A string describing the ciphers to use or exclude. Consult https://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT for details on the format.
• honorCipherOrder : When choosing a cipher, use the server's preferences instead of the client preferences. For further details see tls module documentation.

If no 'CA' details are given, then Node.js will use the default publicly trusted list of CAs as given in http://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt.

tls.createSecurePair([context][, isServer][, requestCert][, rejectUnauthorized][, options])

Creates a new secure pair object with two streams, one of which reads and writes the encrypted data and the other of which reads and writes the cleartext data. Generally, the encrypted stream is piped to/from an incoming encrypted data stream and the cleartext one is used as a replacement for the initial encrypted stream.

• credentials: A secure context object from tls.createSecureContext( ... ).

• isServer: A boolean indicating whether this TLS connection should be opened as a server or a client.

• requestCert: A boolean indicating whether a server should request a certificate from a connecting client. Only applies to server connections.

• rejectUnauthorized: A boolean indicating whether a server should automatically reject clients with invalid certificates. Only applies to servers with requestCert enabled.

• options: An object with common SSL options. See tls.TLSSocket.

tls.createSecurePair() returns a SecurePair object with cleartext and encrypted stream properties.

NOTE: cleartext has the same API as tls.TLSSocket

tls.createServer(options[, secureConnectionListener])

Creates a new tls.Server. The connectionListener argument is automatically set as a listener for the 'secureConnection' event. The options object may contain the following fields:

• pfx: A string or Buffer containing the private key, certificate and CA certs of the server in PFX or PKCS12 format. (Mutually exclusive with the key, cert, and ca options.)

• key: A string or Buffer containing the private key of the server in PEM format. To support multiple keys using different algorithms an array can be provided. It can either be a plain array of keys or an array of objects in the format {pem: key, passphrase: passphrase}. (Required)

• passphrase: A string containing the passphrase for the private key or pfx.

• cert: A string, Buffer, array of strings, or array of Buffers containing the certificate key of the server in PEM format. (Required)

• ca: A string, Buffer, array of strings, or array of Buffers of trusted certificates in PEM format. If this is omitted several well known "root" CAs (like VeriSign) will be used. These are used to authorize connections.

• crl : Either a string or array of strings of PEM encoded CRLs (Certificate Revocation List).

• ciphers: A string describing the ciphers to use or exclude, separated by :. The default cipher suite is:

  ECDHE-RSA-AES128-GCM-SHA256:
  ECDHE-ECDSA-AES128-GCM-SHA256:
  ECDHE-RSA-AES256-GCM-SHA384:
  ECDHE-ECDSA-AES256-GCM-SHA384:
  DHE-RSA-AES128-GCM-SHA256:
  ECDHE-RSA-AES128-SHA256:
  DHE-RSA-AES128-SHA256:
  ECDHE-RSA-AES256-SHA384:
  DHE-RSA-AES256-SHA384:
  ECDHE-RSA-AES256-SHA256:
  DHE-RSA-AES256-SHA256:
  HIGH:
  !aNULL:
  !eNULL:
  !EXPORT:
  !DES:
  !RC4:
  !MD5:
  !PSK:
  !SRP:
  !CAMELLIA
  

  The default cipher suite prefers GCM ciphers for Chrome's 'modern cryptography' setting and also prefers ECDHE and DHE ciphers for Perfect Forward Secrecy, while offering some backward compatibility.

  128 bit AES is preferred over 192 and 256 bit AES in light of specific attacks affecting larger AES key sizes.

  Old clients that rely on insecure and deprecated RC4 or DES-based ciphers (like Internet Explorer 6) cannot complete the handshaking process with the default configuration. If these clients must be supported, the TLS recommendations may offer a compatible cipher suite. For more details on the format, see the OpenSSL cipher list format documentation.

• ecdhCurve: A string describing a named curve to use for ECDH key agreement or false to disable ECDH.

  Defaults to prime256v1 (NIST P-256). Use crypto.getCurves() to obtain a list of available curve names. On recent releases, openssl ecparam -list_curves will also display the name and description of each available elliptic curve.

• dhparam: A string or Buffer containing Diffie Hellman parameters, required for Perfect Forward Secrecy. Use openssl dhparam to create it. Its key length should be greater than or equal to 1024 bits, otherwise it throws an error. It is strongly recommended to use 2048 bits or larger for stronger security. If omitted or invalid, it is silently discarded and DHE ciphers won't be available.

• handshakeTimeout: Abort the connection if the SSL/TLS handshake does not finish in the specified number of milliseconds. The default is 120 seconds.

  A 'clientError' is emitted on the tls.Server object whenever a handshake times out.

• honorCipherOrder : When choosing a cipher, use the server's preferences instead of the client preferences. Default: true.

• requestCert: If true the server will request a certificate from clients that connect and attempt to verify that certificate. Default: false.

• rejectUnauthorized: If true the server will reject any connection which is not authorized with the list of supplied CAs. This option only has an effect if requestCert is true. Default: false.

• NPNProtocols: An array or Buffer of possible NPN protocols. (Protocols should be ordered by their priority.)

• ALPNProtocols: An array or Buffer of possible ALPN protocols. (Protocols should be ordered by their priority.) When the server receives both NPN and ALPN extensions from the client, ALPN takes precedence over NPN and the server does not send an NPN extension to the client.

• SNICallback(servername, cb): A function that will be called if the client supports SNI TLS extension. Two arguments will be passed to it: servername and cb. SNICallback should invoke cb(null, ctx), where ctx is a SecureContext instance. (tls.createSecureContext(...) can be used to get a proper SecureContext.) If SNICallback wasn't provided the default callback with high-level API will be used (see below).

• sessionTimeout: An integer specifying the number of seconds after which the TLS session identifiers and TLS session tickets created by the server will time out. See SSL_CTX_set_timeout for more details.

• ticketKeys: A 48-byte Buffer instance consisting of a 16-byte prefix, a 16-byte HMAC key, and a 16-byte AES key. This can be used to accept TLS session tickets on multiple instances of the TLS server.

  NOTE: Automatically shared between cluster module workers.

• sessionIdContext: A string containing an opaque identifier for session resumption. If requestCert is true, the default is a 128 bit truncated SHA1 hash value generated from the command-line. Otherwise, a default is not provided.

• secureProtocol: The SSL method to use, e.g., SSLv3_method to force SSL version 3. The possible values depend on the version of OpenSSL installed in the environment and are defined in the constant SSL_METHODS.

Here is a simple example echo server:

const tls = require('tls');
const fs = require('fs');

const options = {
  key: fs.readFileSync('server-key.pem'),
  cert: fs.readFileSync('server-cert.pem'),

  // This is necessary only if using the client certificate authentication.
  requestCert: true,

  // This is necessary only if the client uses the self-signed certificate.
  ca: [ fs.readFileSync('client-cert.pem') ]
};

var server = tls.createServer(options, (socket) => {
  console.log('server connected',
              socket.authorized ? 'authorized' : 'unauthorized');
  socket.write('welcome!\n');
  socket.setEncoding('utf8');
  socket.pipe(socket);
});
server.listen(8000, () => {
  console.log('server bound');
});

Or

const tls = require('tls');
const fs = require('fs');

const options = {
  pfx: fs.readFileSync('server.pfx'),

  // This is necessary only if using the client certificate authentication.
  requestCert: true,

};

var server = tls.createServer(options, (socket) => {
  console.log('server connected',
              socket.authorized ? 'authorized' : 'unauthorized');
  socket.write('welcome!\n');
  socket.setEncoding('utf8');
  socket.pipe(socket);
});
server.listen(8000, () => {
  console.log('server bound');
});

You can test this server by connecting to it with openssl s_client:

openssl s_client -connect 127.0.0.1:8000

tls.getCiphers()

Returns an array with the names of the supported SSL ciphers.

Example:

var ciphers = tls.getCiphers();
console.log(ciphers); // ['AES128-SHA', 'AES256-SHA', ...]