csrc/node-v0.10.24/doc/api/tls.markdown - third_party - Git at Google

 # TLS (SSL)

     Stability: 3 - 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 1024

 All severs 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 -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.

 (TODO: docs on creating a CA, for now interested users should just look at
 `test/fixtures/keys/Makefile` in the Node source code)

 To create .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`


 ## Client-initiated renegotiation attack mitigation

 <!-- type=misc -->

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

 To mitigate this, renegotiations are limited to three times every 10 minutes. An
 error is emitted on the [CleartextStream][] instance when the threshold is
 exceeded. The limits are configurable:

   - `tls.CLIENT_RENEG_LIMIT`: renegotiation limit, default is 3.

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

 Don't change the defaults unless you know what you are doing.

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


 ## NPN and SNI

 <!-- type=misc -->

 NPN (Next Protocol Negotiation) and SNI (Server Name Indication) are TLS
 handshake extensions allowing you:

   * NPN - to use one TLS server for multiple protocols (HTTP, SPDY)
   * SNI - to use one TLS server for multiple hostnames with different SSL
     certificates.


 ## 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', ...]


 ## 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 has these possibilities:

   - `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. (Required)

   - `passphrase`: A string of passphrase for the private key or pfx.

   - `cert`: A string or `Buffer` containing the certificate key of the server in
     PEM format. (Required)

   - `ca`: An array of strings or `Buffer`s of trusted certificates in PEM
     format. If this is omitted several well known "root" CAs will be used,
     like VeriSign. 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.

     To mitigate [BEAST attacks] it is recommended that you use this option in
     conjunction with the `honorCipherOrder` option described below to
     prioritize the non-CBC cipher.

     Defaults to `AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH`.
     Consult the [OpenSSL cipher list format documentation] for details on the
     format. ECDH (Elliptic Curve Diffie-Hellman) ciphers are not yet supported.


     `AES128-GCM-SHA256` is used when node.js is linked against OpenSSL 1.0.1
     or newer and the client speaks TLS 1.2, RC4 is used as a secure fallback.

     **NOTE**: Previous revisions of this section suggested `AES256-SHA` as an
     acceptable cipher. Unfortunately, `AES256-SHA` is a CBC cipher and therefore
     susceptible to BEAST attacks. Do *not* use it.

   - `handshakeTimeout`: Abort the connection if the SSL/TLS handshake does not
     finish in this many 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.

     Note that if SSLv2 is used, the server will send its list of preferences
     to the client, and the client chooses the cipher.

     Although, this option is disabled by default, it is *recommended* that you
     use this option in conjunction with the `ciphers` option to mitigate
     BEAST attacks.

   - `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).

   - `SNICallback`: A function that will be called if client supports SNI TLS
     extension. Only one argument will be passed to it: `servername`. And
     `SNICallback` should return SecureContext instance.
     (You can use `crypto.createCredentials(...).context` to get proper
     SecureContext). If `SNICallback` wasn't provided - default callback with
     high-level API will be used (see below).

   - `sessionIdContext`: A string containing a opaque identifier for session
     resumption. If `requestCert` is `true`, the default is MD5 hash value
     generated from command-line. Otherwise, the default is not provided.

   - `secureProtocol`: The SSL method to use, e.g. `SSLv3_method` to force
     SSL version 3. The possible values depend on your installation of
     OpenSSL and are defined in the constant [SSL_METHODS][].

 Here is a simple example echo server:

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

     var 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, function(cleartextStream) {
       console.log('server connected',
                   cleartextStream.authorized ? 'authorized' : 'unauthorized');
       cleartextStream.write("welcome!\n");
       cleartextStream.setEncoding('utf8');
       cleartextStream.pipe(cleartextStream);
     });
     server.listen(8000, function() {
       console.log('server bound');
     });

 Or

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

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

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

     };

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

 Size of slab buffer used by all tls servers and clients.
 Default: `10 * 1024 * 1024`.


 Don't change the defaults unless you know what you are doing.


 ## 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.

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

   - `key`: A string or `Buffer` containing the private key of the client in
     PEM format.

   - `passphrase`: A string of passphrase for the private key or pfx.

   - `cert`: A string or `Buffer` containing the certificate key of the client in
     PEM format.

   - `ca`: An array of strings or `Buffer`s of trusted certificates in PEM
     format. If this is omitted several well known "root" CAs will be used,
     like VeriSign. These are used to authorize connections.

   - `rejectUnauthorized`: If `true`, the server certificate is verified against
     the list of supplied CAs. An `'error'` event is emitted if verification
     fails. Default: `true`.

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

   - `servername`: Servername for SNI (Server Name Indication) TLS extension.

   - `secureProtocol`: The SSL method to use, e.g. `SSLv3_method` to force
     SSL version 3. The possible values depend on your installation of
     OpenSSL and are defined in the constant [SSL_METHODS][].

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

 `tls.connect()` returns a [CleartextStream][] object.

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

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

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

 Or

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

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

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

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

 Creates a new secure pair object with two streams, one of which reads/writes
 encrypted data, and one reads/writes cleartext data.
 Generally the encrypted one 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 credentials object from crypto.createCredentials( ... )

  - `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.

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

 ## Class: SecurePair

 Returned by tls.createSecurePair.

 ### Event: 'secure'

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

 Similarly to the checking for the server 'secureConnection' event,
 pair.cleartext.authorized should be checked to confirm whether the certificate
 used properly authorized.

 ## Class: tls.Server

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

 ### Event: 'secureConnection'

 `function (cleartextStream) {}`

 This event is emitted after a new connection has been successfully
 handshaked. The argument is a instance of [CleartextStream][]. It has all the
 common stream methods and events.

 `cleartextStream.authorized` is a boolean value which indicates if the
 client has verified by one of the supplied certificate authorities for the
 server. If `cleartextStream.authorized` is false, then
 `cleartextStream.authorizationError` is set to describe how authorization
 failed. Implied but worth mentioning: depending on the settings of the TLS
 server, you unauthorized connections may be accepted.
 `cleartextStream.npnProtocol` is a string containing selected NPN protocol.
 `cleartextStream.servername` is a string containing servername requested with
 SNI.


 ### Event: 'clientError'

 `function (exception, securePair) { }`

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

 `securePair` is the `tls.SecurePair` that the error originated from.


 ### Event: 'newSession'

 `function (sessionId, sessionData) { }`

 Emitted on creation of TLS session. May be used to store sessions in external
 storage.


 ### Event: 'resumeSession'

 `function (sessionId, callback) { }`

 Emitted when client wants to resume previous TLS session. Event listener may
 perform lookup in external storage using given `sessionId`, and invoke
 `callback(null, sessionData)` once finished. If 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 socket.


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

 Begin accepting connections on the specified `port` and `host`.  If the
 `host` is omitted, the server will accept connections directed to any
 IPv4 address (`INADDR_ANY`).

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

 See `net.Server` for more information.


 ### server.close()

 Stops the server from accepting new connections. This function is
 asynchronous, the server is finally closed when the server emits a `'close'`
 event.

 ### 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.addContext(hostname, credentials)

 Add secure context that will be used if client request's SNI hostname is
 matching passed `hostname` (wildcards can be used). `credentials` can contain
 `key`, `cert` and `ca`.

 ### server.maxConnections

 Set this property to reject connections when the server's connection count
 gets high.

 ### server.connections

 The number of concurrent connections on the server.


 ## Class: CryptoStream

 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: tls.CleartextStream

 This is a stream on top of the *Encrypted* stream that makes it possible to
 read/write an encrypted data as a cleartext data.

 This instance implements a duplex [Stream][] interfaces.  It has all the
 common stream methods and events.

 A ClearTextStream is the `clear` member of a SecurePair object.

 ### Event: 'secureConnect'

 This event is emitted after a new connection has been successfully handshaked.
 The listener will be called no matter if the server's certificate was
 authorized or not. It is up to the user to test `cleartextStream.authorized`
 to see if the server certificate was signed by one of the specified CAs.
 If `cleartextStream.authorized === false` then the error can be found in
 `cleartextStream.authorizationError`. Also if NPN was used - you can check
 `cleartextStream.npnProtocol` for negotiated protocol.

 ### cleartextStream.authorized

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

 ### cleartextStream.authorizationError

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

 ### cleartextStream.getPeerCertificate()

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

 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' },
       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' }

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

 ### cleartextStream.getCipher()
 Returns an object representing the cipher name and the SSL/TLS
 protocol version of the current connection.

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

 See SSL_CIPHER_get_name() and SSL_CIPHER_get_version() in
 http://www.openssl.org/docs/ssl/ssl.html#DEALING_WITH_CIPHERS for more
 information.

 ### cleartextStream.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' }`

 ### cleartextStream.remoteAddress

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

 ### cleartextStream.remotePort

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

 [OpenSSL cipher list format documentation]: http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT
 [BEAST attacks]: http://blog.ivanristic.com/2011/10/mitigating-the-beast-attack-on-tls.html
 [CleartextStream]: #tls_class_tls_cleartextstream
 [net.Server.address()]: net.html#net_server_address
 ['secureConnect']: #tls_event_secureconnect
 [secureConnection]: #tls_event_secureconnection
 [Stream]: stream.html#stream_stream
 [SSL_METHODS]: http://www.openssl.org/docs/ssl/ssl.html#DEALING_WITH_PROTOCOL_METHODS
 [tls.Server]: #tls_class_tls_server
	# TLS (SSL)

	Stability: 3 - 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 1024

	All severs 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 -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.

	(TODO: docs on creating a CA, for now interested users should just look at
	`test/fixtures/keys/Makefile` in the Node source code)

	To create .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`


	## Client-initiated renegotiation attack mitigation

	<!-- type=misc -->

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

	To mitigate this, renegotiations are limited to three times every 10 minutes. An
	error is emitted on the [CleartextStream][] instance when the threshold is
	exceeded. The limits are configurable:

	- `tls.CLIENT_RENEG_LIMIT`: renegotiation limit, default is 3.

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

	Don't change the defaults unless you know what you are doing.

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


	## NPN and SNI

	<!-- type=misc -->

	NPN (Next Protocol Negotiation) and SNI (Server Name Indication) are TLS
	handshake extensions allowing you:

	* NPN - to use one TLS server for multiple protocols (HTTP, SPDY)
	* SNI - to use one TLS server for multiple hostnames with different SSL
	certificates.


	## 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', ...]


	## 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 has these possibilities:

	- `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. (Required)

	- `passphrase`: A string of passphrase for the private key or pfx.

	- `cert`: A string or `Buffer` containing the certificate key of the server in
	PEM format. (Required)

	- `ca`: An array of strings or `Buffer`s of trusted certificates in PEM
	format. If this is omitted several well known "root" CAs will be used,
	like VeriSign. 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.

	To mitigate [BEAST attacks] it is recommended that you use this option in
	conjunction with the `honorCipherOrder` option described below to
	prioritize the non-CBC cipher.

	Defaults to `AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH`.
	Consult the [OpenSSL cipher list format documentation] for details on the
	format. ECDH (Elliptic Curve Diffie-Hellman) ciphers are not yet supported.


	`AES128-GCM-SHA256` is used when node.js is linked against OpenSSL 1.0.1
	or newer and the client speaks TLS 1.2, RC4 is used as a secure fallback.

	NOTE: Previous revisions of this section suggested `AES256-SHA` as an
	acceptable cipher. Unfortunately, `AES256-SHA` is a CBC cipher and therefore
	susceptible to BEAST attacks. Do not use it.

	- `handshakeTimeout`: Abort the connection if the SSL/TLS handshake does not
	finish in this many 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.

	Note that if SSLv2 is used, the server will send its list of preferences
	to the client, and the client chooses the cipher.

	Although, this option is disabled by default, it is recommended that you
	use this option in conjunction with the `ciphers` option to mitigate
	BEAST attacks.

	- `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).

	- `SNICallback`: A function that will be called if client supports SNI TLS
	extension. Only one argument will be passed to it: `servername`. And
	`SNICallback` should return SecureContext instance.
	(You can use `crypto.createCredentials(...).context` to get proper
	SecureContext). If `SNICallback` wasn't provided - default callback with
	high-level API will be used (see below).

	- `sessionIdContext`: A string containing a opaque identifier for session
	resumption. If `requestCert` is `true`, the default is MD5 hash value
	generated from command-line. Otherwise, the default is not provided.

	- `secureProtocol`: The SSL method to use, e.g. `SSLv3_method` to force
	SSL version 3. The possible values depend on your installation of
	OpenSSL and are defined in the constant [SSL_METHODS][].

	Here is a simple example echo server:

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

	var 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, function(cleartextStream) {
	console.log('server connected',
	cleartextStream.authorized ? 'authorized' : 'unauthorized');
	cleartextStream.write("welcome!\n");
	cleartextStream.setEncoding('utf8');
	cleartextStream.pipe(cleartextStream);
	});
	server.listen(8000, function() {
	console.log('server bound');
	});

	Or

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

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

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

	};

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

	Size of slab buffer used by all tls servers and clients.
	Default: `10 * 1024 * 1024`.


	Don't change the defaults unless you know what you are doing.


	## 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.

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

	- `key`: A string or `Buffer` containing the private key of the client in
	PEM format.

	- `passphrase`: A string of passphrase for the private key or pfx.

	- `cert`: A string or `Buffer` containing the certificate key of the client in
	PEM format.

	- `ca`: An array of strings or `Buffer`s of trusted certificates in PEM
	format. If this is omitted several well known "root" CAs will be used,
	like VeriSign. These are used to authorize connections.

	- `rejectUnauthorized`: If `true`, the server certificate is verified against
	the list of supplied CAs. An `'error'` event is emitted if verification
	fails. Default: `true`.

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

	- `servername`: Servername for SNI (Server Name Indication) TLS extension.

	- `secureProtocol`: The SSL method to use, e.g. `SSLv3_method` to force
	SSL version 3. The possible values depend on your installation of
	OpenSSL and are defined in the constant [SSL_METHODS][].

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

	`tls.connect()` returns a [CleartextStream][] object.

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

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

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

	Or

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

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

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

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

	Creates a new secure pair object with two streams, one of which reads/writes
	encrypted data, and one reads/writes cleartext data.
	Generally the encrypted one 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 credentials object from crypto.createCredentials( ... )

	- `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.

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

	## Class: SecurePair

	Returned by tls.createSecurePair.

	### Event: 'secure'

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

	Similarly to the checking for the server 'secureConnection' event,
	pair.cleartext.authorized should be checked to confirm whether the certificate
	used properly authorized.

	## Class: tls.Server

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

	### Event: 'secureConnection'

	`function (cleartextStream) {}`

	This event is emitted after a new connection has been successfully
	handshaked. The argument is a instance of [CleartextStream][]. It has all the
	common stream methods and events.

	`cleartextStream.authorized` is a boolean value which indicates if the
	client has verified by one of the supplied certificate authorities for the
	server. If `cleartextStream.authorized` is false, then
	`cleartextStream.authorizationError` is set to describe how authorization
	failed. Implied but worth mentioning: depending on the settings of the TLS
	server, you unauthorized connections may be accepted.
	`cleartextStream.npnProtocol` is a string containing selected NPN protocol.
	`cleartextStream.servername` is a string containing servername requested with
	SNI.


	### Event: 'clientError'

	`function (exception, securePair) { }`

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

	`securePair` is the `tls.SecurePair` that the error originated from.


	### Event: 'newSession'

	`function (sessionId, sessionData) { }`

	Emitted on creation of TLS session. May be used to store sessions in external
	storage.


	### Event: 'resumeSession'

	`function (sessionId, callback) { }`

	Emitted when client wants to resume previous TLS session. Event listener may
	perform lookup in external storage using given `sessionId`, and invoke
	`callback(null, sessionData)` once finished. If 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 socket.


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

	Begin accepting connections on the specified `port` and `host`. If the
	`host` is omitted, the server will accept connections directed to any
	IPv4 address (`INADDR_ANY`).

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

	See `net.Server` for more information.


	### server.close()

	Stops the server from accepting new connections. This function is
	asynchronous, the server is finally closed when the server emits a `'close'`
	event.

	### 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.addContext(hostname, credentials)

	Add secure context that will be used if client request's SNI hostname is
	matching passed `hostname` (wildcards can be used). `credentials` can contain
	`key`, `cert` and `ca`.

	### server.maxConnections

	Set this property to reject connections when the server's connection count
	gets high.

	### server.connections

	The number of concurrent connections on the server.


	## Class: CryptoStream

	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: tls.CleartextStream

	This is a stream on top of the Encrypted stream that makes it possible to
	read/write an encrypted data as a cleartext data.

	This instance implements a duplex [Stream][] interfaces. It has all the
	common stream methods and events.

	A ClearTextStream is the `clear` member of a SecurePair object.

	### Event: 'secureConnect'

	This event is emitted after a new connection has been successfully handshaked.
	The listener will be called no matter if the server's certificate was
	authorized or not. It is up to the user to test `cleartextStream.authorized`
	to see if the server certificate was signed by one of the specified CAs.
	If `cleartextStream.authorized === false` then the error can be found in
	`cleartextStream.authorizationError`. Also if NPN was used - you can check
	`cleartextStream.npnProtocol` for negotiated protocol.

	### cleartextStream.authorized

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

	### cleartextStream.authorizationError

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

	### cleartextStream.getPeerCertificate()

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

	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' },
	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' }

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

	### cleartextStream.getCipher()
	Returns an object representing the cipher name and the SSL/TLS
	protocol version of the current connection.

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

	See SSL_CIPHER_get_name() and SSL_CIPHER_get_version() in
	http://www.openssl.org/docs/ssl/ssl.html#DEALING_WITH_CIPHERS for more
	information.

	### cleartextStream.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' }`

	### cleartextStream.remoteAddress

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

	### cleartextStream.remotePort

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

	[OpenSSL cipher list format documentation]: http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT
	[BEAST attacks]: http://blog.ivanristic.com/2011/10/mitigating-the-beast-attack-on-tls.html
	[CleartextStream]: #tls_class_tls_cleartextstream
	[net.Server.address()]: net.html#net_server_address
	['secureConnect']: #tls_event_secureconnect
	[secureConnection]: #tls_event_secureconnection
	[Stream]: stream.html#stream_stream
	[SSL_METHODS]: http://www.openssl.org/docs/ssl/ssl.html#DEALING_WITH_PROTOCOL_METHODS
	[tls.Server]: #tls_class_tls_server