TLS (SSL) | Node.js v7.10.1 Documentation (original) (raw)

TLS (SSL)#

Stability: 2 - Stable

The tls module provides an implementation of the Transport Layer Security (TLS) and Secure Socket Layer (SSL) protocols that is built on top of OpenSSL. The module can be accessed using:

const tls = require('tls');

TLS/SSL Concepts#

The TLS/SSL is a public/private key infrastructure (PKI). For most common cases, each client and server must have a private key.

Private keys can be generated in multiple ways. The example below illustrates use of the OpenSSL command-line interface to generate a 2048-bit RSA private key:

openssl genrsa -out ryans-key.pem 2048

With TLS/SSL, all servers (and some clients) must have a certificate. Certificates are public keys that correspond to a private key, and that are digitally signed either by a Certificate Authority or by the owner of the private key (such certificates are referred to as "self-signed"). The first step to obtaining a certificate is to create a Certificate Signing Request(CSR) file.

The OpenSSL command-line interface can be used to generate a CSR for a private key:

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

Once the CSR file is generated, it can either be sent to a Certificate Authority for signing or used to generate a self-signed certificate.

Creating a self-signed certificate using the OpenSSL command-line interface is illustrated in the example below:

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

Once the certificate is generated, it can be used to generate a .pfx or.p12 file:

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

Where:

Perfect Forward Secrecy#

The term "Forward Secrecy" or "Perfect Forward Secrecy" describes a feature of key-agreement (i.e., key-exchange) methods. That is, the server and client keys are used to negotiate new temporary keys that are used specifically and only for the current communication session. Practically, this means that even if the server's private key is compromised, communication can only be decrypted by eavesdroppers if the attacker manages to obtain the key-pair specifically generated for the session.

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

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

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

To use Perfect Forward Secrecy using DHE with the tls module, it is required to generate Diffie-Hellman parameters and specify them with the dhparamoption to tls.createSecureContext(). The following illustrates the use of the OpenSSL command-line interface to generate such parameters:

openssl dhparam -outform PEM -out dhparam.pem 2048

If using Perfect Forward Secrecy using ECDHE, Diffie-Hellman parameters are not required and a default ECDHE curve will be used. The ecdhCurve property can be used when creating a TLS Server to specify the name of an alternative curve to use, see tls.createServer() for more info.

ALPN, NPN and SNI#

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

Note: Use of ALPN is recommended over NPN. The NPN extension has never been formally defined or documented and generally not recommended for use.

Client-initiated renegotiation attack mitigation#

The TLS protocol allows clients to renegotiate certain aspects of the TLS session. Unfortunately, session renegotiation requires a disproportionate amount of server-side resources, making it a potential vector for denial-of-service attacks.

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

Note: The default renegotiation limits should not be modified without a full understanding of the implications and risks.

To test the renegotiation limits on a server, connect to it using the OpenSSL command-line client (openssl s_client -connect address:port) then inputR<CR> (i.e., the letter R followed by a carriage return) multiple 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 replaced entirely using the --tls-cipher-list command line switch. For instance, the following makesECDHE-RSA-AES128-GCM-SHA256:!RC4 the default TLS cipher suite:

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

The default can also be replaced on a per client or server basis using theciphers option from tls.createSecureContext(), which is also available in tls.createServer(), tls.connect(), and when creating newtls.TLSSockets.

Consult OpenSSL cipher list format documentation for details on the format.

Note: 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 and ciphers option should by used only if absolutely necessary.

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, theTLS recommendations may offer a compatible cipher suite. For more details on the format, see the OpenSSL cipher list format documentation.

Class: tls.Server#

Added in: v0.3.2

The tls.Server class is a subclass of net.Server that accepts encrypted connections using TLS or SSL.

Event: 'newSession'#

Added in: v0.9.2

The 'newSession' event is emitted upon creation of a new TLS session. This may be used to store sessions in external storage. The listener callback is passed three arguments when called:

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

Event: 'OCSPRequest'#

Added in: v0.11.13

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.

Note: 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.)

Note: Listening for this event will have an effect only 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'#

Added in: v0.9.2

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

When called, the event listener may perform a lookup in external storage using the given sessionId and invoke callback(null, sessionData) once finished. If the session cannot be resumed (i.e., doesn't exist in storage) the callback may be invoked as callback(null, null). Calling callback(err) will terminate the incoming connection and destroy the socket.

Note: 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);
});

Event: 'secureConnection'#

Added in: v0.3.2

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.authorizationErroris set to describe how authorization failed. Note that depending on the settings of the TLS server, unauthorized connections may still be accepted.

The tlsSocket.npnProtocol and tlsSocket.alpnProtocol properties are strings that contain the selected NPN and ALPN protocols, respectively. 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, tlsSocket.alpnProtocol returns false.

The tlsSocket.servername property is a string containing the server name requested via SNI.

Event: 'tlsClientError'#

Added in: v6.0.0

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)#

Added in: v0.5.3

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

server.address()#

Added in: v0.6.0

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])#

Added in: v0.3.2

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.connections#

Added in: v0.3.2

Returns the current number of concurrent connections on the server.

server.getTicketKeys()#

Added in: v3.0.0

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

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

Added in: v0.3.2

The server.listen() methods instructs the server to begin accepting connections on the specified port and hostname.

This function operates asynchronously. If the callback is given, it will be called when the server has started listening.

See net.Server for more information.

server.setTicketKeys(keys)#

Added in: v3.0.0

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

Note: The key's Buffer should be 48 bytes long. See ticketKeys option intls.createServer for more information on how it is used.

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

Class: tls.TLSSocket#

Added in: v0.11.4

The tls.TLSSocket is a subclass of net.Socket that performs transparent encryption of written data and all required TLS negotiation.

Instances of tls.TLSSocket implement the duplex Stream interface.

Note: 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 tls.TLSSocket object from an existing TCP socket.

Event: 'OCSPResponse'#

Added in: v0.11.13

The 'OCSPResponse' event is emitted if the requestOCSP option was set when the tls.TLSSocket was created and an OCSP response has been received. The listener callback is passed a single argument when called:

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

Event: 'secureConnect'#

Added in: v0.11.4

The 'secureConnect' event is emitted after the handshaking process for a new connection has successfully completed. The listener callback will be called regardless of whether or not the server's certificate has been authorized. It is the client's responsibility to check the tlsSocket.authorized property to determine if the server certificate was signed by one of the specified CAs. IftlsSocket.authorized === false, then the error can be found by examining thetlsSocket.authorizationError property. If either ALPN or NPN was used, the tlsSocket.alpnProtocol or tlsSocket.npnProtocol properties can be checked to determine the negotiated protocol.

tlsSocket.address()#

Added in: v0.11.4

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.authorizationError

Added in: v0.11.4

Returns the reason why the peer's certificate was not been verified. This property is set only when tlsSocket.authorized === false.

tlsSocket.authorized#

Added in: v0.11.4

Returns true if the peer certificate was signed by one of the CAs specified when creating the tls.TLSSocket instance, otherwise false.

tlsSocket.encrypted#

Added in: v0.11.4

Always returns true. This may be used to distinguish TLS sockets from regularnet.Socket instances.

tlsSocket.getCipher()#

Added in: v0.11.4

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

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

See SSL_CIPHER_get_name() and SSL_CIPHER_get_version() inhttps://www.openssl.org/docs/man1.0.2/ssl/SSL_CIPHER_get_name.html for more information.

tlsSocket.getEphemeralKeyInfo()#

Added in: v5.0.0

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; null is returned if called on a server socket. The supported types are 'DH' and 'ECDH'. Thename property is available only when type is 'ECDH'.

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

tlsSocket.getPeerCertificate([ detailed ])#

Added in: v0.11.4

Returns an object representing the peer's certificate. The returned object has some properties corresponding to the fields of the certificate.

If the full certificate chain was requested, each certificate will include aissuerCertificate property containing an object representing its issuer's certificate.

For example:

{ subject:
   { C: 'UK',
     ST: 'Acknack Ltd',
     L: 'Rhys Jones',
     O: 'node.js',
     OU: 'Test TLS Certificate',
     CN: 'localhost' },
  issuer:
   { C: 'UK',
     ST: 'Acknack Ltd',
     L: 'Rhys Jones',
     O: 'node.js',
     OU: 'Test TLS Certificate',
     CN: 'localhost' },
  issuerCertificate:
   { ... another certificate, possibly with a .issuerCertificate ... },
  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, an empty object will be returned.

tlsSocket.getProtocol()#

Added in: v5.7.0

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

Example responses include:

See https://www.openssl.org/docs/man1.0.2/ssl/SSL_get_version.html for more information.

tlsSocket.getSession()#

Added in: v0.11.4

Returns the ASN.1 encoded TLS session or undefined if no session was negotiated. Can be used to speed up handshake establishment when reconnecting to the server.

tlsSocket.getTLSTicket()#

Added in: v0.11.4

Returns the TLS session ticket or undefined if no session was negotiated.

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

tlsSocket.localAddress#

Added in: v0.11.4

Returns the string representation of the local IP address.

tlsSocket.localPort#

Added in: v0.11.4

Returns the numeric representation of the local port.

tlsSocket.remoteAddress#

Added in: v0.11.4

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

tlsSocket.remoteFamily#

Added in: v0.11.4

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

tlsSocket.remotePort#

Added in: v0.11.4

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

tlsSocket.renegotiate(options, callback)#

Added in: v0.11.8

The tlsSocket.renegotiate() method initiates a TLS renegotiation process. Upon completion, the callback function will be passed a single argument that is either an Error (if the request failed) or null.

Note: This method can be used to request a peer's certificate after the secure connection has been established.

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

tlsSocket.setMaxSendFragment(size)#

Added in: v0.11.11

The tlsSocket.setMaxSendFragment() method sets the maximum TLS fragment size. Returns true if setting the limit succeeded; 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])#

The callback function, if specified, will be added as a listener for the'secureConnect' event.

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

The following implements a simple "echo server" example:

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

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

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

const 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')
};

const 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.connect(path[, options][, callback])#

Added in: v0.11.3

Same as tls.connect() except that path can be provided as an argument instead of an option.

Note: A path option, if specified, will take precedence over the path argument.

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

Added in: v0.11.3

Same as tls.connect() except that port and host can be provided as arguments instead of options.

Note: A port or host option, if specified, will take precedence over any port or host argument.

tls.createSecureContext(options)#

The tls.createSecureContext() method creates a credentials object.

A key is required for ciphers that make use of certificates. Either key orpfx can be used to provide it.

If the 'ca' option is not given, then Node.js will use the default publicly trusted list of CAs as given inhttp://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt.

tls.createServer([options][, secureConnectionListener])#

Creates a new tls.Server. The secureConnectionListener, if provided, is automatically set as a listener for the 'secureConnection' event.

The following illustrates a simple 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') ]
};

const 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,

};

const 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');
});

This server can be tested by connecting to it using openssl s_client:

openssl s_client -connect 127.0.0.1:8000

tls.getCiphers()#

Added in: v0.10.2

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

For example:

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

tls.DEFAULT_ECDH_CURVE#

Added in: v0.11.13

The default curve name to use for ECDH key agreement in a tls server. The default value is 'prime256v1' (NIST P-256). Consult RFC 4492 andFIPS.186-4 for more details.

Deprecated APIs#

Class: CryptoStream#

Added in: v0.3.4Deprecated since: v0.11.3

Stability: 0 - Deprecated: Use tls.TLSSocket instead.

The tls.CryptoStream class represents a stream of encrypted data. This class has been deprecated and should no longer be used.

cryptoStream.bytesWritten#

Added in: v0.3.4Deprecated since: v0.11.3

The cryptoStream.bytesWritten property returns the total number of bytes written to the underlying socket including the bytes required for the implementation of the TLS protocol.

Class: SecurePair#

Added in: v0.3.2Deprecated since: v0.11.3

Stability: 0 - Deprecated: Use tls.TLSSocket instead.

Returned by tls.createSecurePair().

Event: 'secure'#

Added in: v0.3.2Deprecated since: v0.11.3

The 'secure' event is emitted by the SecurePair object once a secure connection has been established.

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

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

Stability: 0 - Deprecated: Use tls.TLSSocket instead.

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.

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

Note: cleartext has the same API as tls.TLSSocket.

Note: The tls.createSecurePair() method is now deprecated in favor oftls.TLSSocket(). For example, the code:

pair = tls.createSecurePair(/* ... */);
pair.encrypted.pipe(socket);
socket.pipe(pair.encrypted);

can be replaced by:

secure_socket = tls.TLSSocket(socket, options);

where secure_socket has the same API as pair.cleartext.