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# TLS (SSL)
<!--introduced_in=v0.10.0-->
> Stability: 2 - Stable
<!-- source_link=lib/tls.js -->
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:
```js
const tls = require('tls');
```
## TLS/SSL concepts
TLS/SSL is a set of protocols that rely on a public key infrastructure (PKI) to
enable secure communication between a client and a server. For most common
cases, each 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:
```bash
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:
```bash
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:
```bash
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:
```bash
openssl pkcs12 -export -in ryans-cert.pem -inkey ryans-key.pem \
-certfile ca-cert.pem -out ryans.pfx
```
Where:
* `in`: is the signed certificate
* `inkey`: is the associated private key
* `certfile`: is a concatenation of all Certificate Authority (CA) certs into
a single file, e.g. `cat ca1-cert.pem ca2-cert.pem > ca-cert.pem`
### Perfect forward secrecy
<!-- type=misc -->
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):
* [DHE][]: An ephemeral version of the Diffie-Hellman key-agreement protocol.
* [ECDHE][]: An ephemeral version of the Elliptic Curve Diffie-Hellman
key-agreement protocol.
To use perfect forward secrecy using `DHE` with the `tls` module, it is required
to generate Diffie-Hellman parameters and specify them with the `dhparam`
option to [`tls.createSecureContext()`][]. The following illustrates the use of
the OpenSSL command-line interface to generate such parameters:
```bash
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 list of names of supported
curves to use, see [`tls.createServer()`][] for more info.
Perfect forward secrecy was optional up to TLSv1.2, but it is not optional for
TLSv1.3, because all TLSv1.3 cipher suites use ECDHE.
### ALPN and SNI
<!-- type=misc -->
ALPN (Application-Layer Protocol Negotiation Extension) and
SNI (Server Name Indication) are TLS handshake extensions:
* ALPN: Allows the use of one TLS server for multiple protocols (HTTP, HTTP/2)
* SNI: Allows the use of one TLS server for multiple hostnames with different
certificates.
### Pre-shared keys
<!-- type=misc -->
TLS-PSK support is available as an alternative to normal certificate-based
authentication. It uses a pre-shared key instead of certificates to
authenticate a TLS connection, providing mutual authentication.
TLS-PSK and public key infrastructure are not mutually exclusive. Clients and
servers can accommodate both, choosing either of them during the normal cipher
negotiation step.
TLS-PSK is only a good choice where means exist to securely share a
key with every connecting machine, so it does not replace the public key
infrastructure (PKI) for the majority of TLS uses.
The TLS-PSK implementation in OpenSSL has seen many security flaws in
recent years, mostly because it is used only by a minority of applications.
Please consider all alternative solutions before switching to PSK ciphers.
Upon generating PSK it is of critical importance to use sufficient entropy as
discussed in [RFC 4086][]. Deriving a shared secret from a password or other
low-entropy sources is not secure.
PSK ciphers are disabled by default, and using TLS-PSK thus requires explicitly
specifying a cipher suite with the `ciphers` option. The list of available
ciphers can be retrieved via `openssl ciphers -v 'PSK'`. All TLS 1.3
ciphers are eligible for PSK but currently only those that use SHA256 digest are
supported they can be retrieved via `openssl ciphers -v -s -tls1_3 -psk`.
According to the [RFC 4279][], PSK identities up to 128 bytes in length and
PSKs up to 64 bytes in length must be supported. As of OpenSSL 1.1.0
maximum identity size is 128 bytes, and maximum PSK length is 256 bytes.
The current implementation doesn't support asynchronous PSK callbacks due to the
limitations of the underlying OpenSSL API.
### Client-initiated renegotiation attack mitigation
<!-- type=misc -->
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:
* `tls.CLIENT_RENEG_LIMIT` {number} Specifies the number of renegotiation
requests. **Default:** `3`.
* `tls.CLIENT_RENEG_WINDOW` {number} Specifies the time renegotiation window
in seconds. **Default:** `600` (10 minutes).
The default renegotiation limits should not be modified without a full
understanding of the implications and risks.
TLSv1.3 does not support renegotiation.
### Session resumption
Establishing a TLS session can be relatively slow. The process can be sped
up by saving and later reusing the session state. There are several mechanisms
to do so, discussed here from oldest to newest (and preferred).
#### Session identifiers
Servers generate a unique ID for new connections and
send it to the client. Clients and servers save the session state. When
reconnecting, clients send the ID of their saved session state and if the server
also has the state for that ID, it can agree to use it. Otherwise, the server
will create a new session. See [RFC 2246][] for more information, page 23 and
30\.
Resumption using session identifiers is supported by most web browsers when
making HTTPS requests.
For Node.js, clients wait for the [`'session'`][] event to get the session data,
and provide the data to the `session` option of a subsequent [`tls.connect()`][]
to reuse the session. Servers must
implement handlers for the [`'newSession'`][] and [`'resumeSession'`][] events
to save and restore the session data using the session ID as the lookup key to
reuse sessions. To reuse sessions across load balancers or cluster workers,
servers must use a shared session cache (such as Redis) in their session
handlers.
#### Session tickets
The servers encrypt the entire session state and send it
to the client as a "ticket". When reconnecting, the state is sent to the server
in the initial connection. This mechanism avoids the need for server-side
session cache. If the server doesn't use the ticket, for any reason (failure
to decrypt it, it's too old, etc.), it will create a new session and send a new
ticket. See [RFC 5077][] for more information.
Resumption using session tickets is becoming commonly supported by many web
browsers when making HTTPS requests.
For Node.js, clients use the same APIs for resumption with session identifiers
as for resumption with session tickets. For debugging, if
[`tls.TLSSocket.getTLSTicket()`][] returns a value, the session data contains a
ticket, otherwise it contains client-side session state.
With TLSv1.3, be aware that multiple tickets may be sent by the server,
resulting in multiple `'session'` events, see [`'session'`][] for more
information.
Single process servers need no specific implementation to use session tickets.
To use session tickets across server restarts or load balancers, servers must
all have the same ticket keys. There are three 16-byte keys internally, but the
tls API exposes them as a single 48-byte buffer for convenience.
Its possible to get the ticket keys by calling [`server.getTicketKeys()`][] on
one server instance and then distribute them, but it is more reasonable to
securely generate 48 bytes of secure random data and set them with the
`ticketKeys` option of [`tls.createServer()`][]. The keys should be regularly
regenerated and server's keys can be reset with
[`server.setTicketKeys()`][].
Session ticket keys are cryptographic keys, and they _**must be stored
securely**_. With TLS 1.2 and below, if they are compromised all sessions that
used tickets encrypted with them can be decrypted. They should not be stored
on disk, and they should be regenerated regularly.
If clients advertise support for tickets, the server will send them. The
server can disable tickets by supplying
`require('constants').SSL_OP_NO_TICKET` in `secureOptions`.
Both session identifiers and session tickets timeout, causing the server to
create new sessions. The timeout can be configured with the `sessionTimeout`
option of [`tls.createServer()`][].
For all the mechanisms, when resumption fails, servers will create new sessions.
Since failing to resume the session does not cause TLS/HTTPS connection
failures, it is easy to not notice unnecessarily poor TLS performance. The
OpenSSL CLI can be used to verify that servers are resuming sessions. Use the
`-reconnect` option to `openssl s_client`, for example:
```console
$ openssl s_client -connect localhost:443 -reconnect
```
Read through the debug output. The first connection should say "New", for
example:
```text
New, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256
```
Subsequent connections should say "Reused", for example:
```text
Reused, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256
```
## Modifying the default TLS cipher suite
Node.js is built with a default suite of enabled and disabled TLS ciphers. This
default cipher list can be configured when building Node.js to allow
distributions to provide their own default list.
The following command can be used to show the default cipher suite:
```console
node -p crypto.constants.defaultCoreCipherList | tr ':' '\n'
TLS_AES_256_GCM_SHA384
TLS_CHACHA20_POLY1305_SHA256
TLS_AES_128_GCM_SHA256
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 (directly, or via the [`NODE_OPTIONS`][] environment
variable). For instance, the following makes `ECDHE-RSA-AES128-GCM-SHA256:!RC4`
the default TLS cipher suite:
```bash
node --tls-cipher-list='ECDHE-RSA-AES128-GCM-SHA256:!RC4' server.js
export NODE_OPTIONS=--tls-cipher-list='ECDHE-RSA-AES128-GCM-SHA256:!RC4'
node server.js
```
The default can also be replaced on a per client or server basis using the
`ciphers` option from [`tls.createSecureContext()`][], which is also available
in [`tls.createServer()`][], [`tls.connect()`][], and when creating new
[`tls.TLSSocket`][]s.
The ciphers list can contain a mixture of TLSv1.3 cipher suite names, the ones
that start with `'TLS_'`, and specifications for TLSv1.2 and below cipher
suites. The TLSv1.2 ciphers support a legacy specification format, consult
the OpenSSL [cipher list format][] documentation for details, but those
specifications do _not_ apply to TLSv1.3 ciphers. The TLSv1.3 suites can only
be enabled by including their full name in the cipher list. They cannot, for
example, be enabled or disabled by using the legacy TLSv1.2 `'EECDH'` or
`'!EECDH'` specification.
Despite the relative order of TLSv1.3 and TLSv1.2 cipher suites, the TLSv1.3
protocol is significantly more secure than TLSv1.2, and will always be chosen
over TLSv1.2 if the handshake indicates it is supported, and if any TLSv1.3
cipher suites are enabled.
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, the
[TLS recommendations][] may offer a compatible cipher suite. For more details
on the format, see the OpenSSL [cipher list format][] documentation.
There are only five TLSv1.3 cipher suites:
* `'TLS_AES_256_GCM_SHA384'`
* `'TLS_CHACHA20_POLY1305_SHA256'`
* `'TLS_AES_128_GCM_SHA256'`
* `'TLS_AES_128_CCM_SHA256'`
* `'TLS_AES_128_CCM_8_SHA256'`
The first three are enabled by default. The two `CCM`-based suites are supported
by TLSv1.3 because they may be more performant on constrained systems, but they
are not enabled by default since they offer less security.
## X509 certificate error codes
Multiple functions can fail due to certificate errors that are reported by
OpenSSL. In such a case, the function provides an {Error} via its callback that
has the property `code` which can take one of the following values:
<!--
values are taken from src/crypto/crypto_common.cc
description are taken from deps/openssl/openssl/crypto/x509/x509_txt.c
-->
* `'UNABLE_TO_GET_ISSUER_CERT'`: Unable to get issuer certificate.
* `'UNABLE_TO_GET_CRL'`: Unable to get certificate CRL.
* `'UNABLE_TO_DECRYPT_CERT_SIGNATURE'`: Unable to decrypt certificate's
signature.
* `'UNABLE_TO_DECRYPT_CRL_SIGNATURE'`: Unable to decrypt CRL's signature.
* `'UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY'`: Unable to decode issuer public key.
* `'CERT_SIGNATURE_FAILURE'`: Certificate signature failure.
* `'CRL_SIGNATURE_FAILURE'`: CRL signature failure.
* `'CERT_NOT_YET_VALID'`: Certificate is not yet valid.
* `'CERT_HAS_EXPIRED'`: Certificate has expired.
* `'CRL_NOT_YET_VALID'`: CRL is not yet valid.
* `'CRL_HAS_EXPIRED'`: CRL has expired.
* `'ERROR_IN_CERT_NOT_BEFORE_FIELD'`: Format error in certificate's notBefore
field.
* `'ERROR_IN_CERT_NOT_AFTER_FIELD'`: Format error in certificate's notAfter
field.
* `'ERROR_IN_CRL_LAST_UPDATE_FIELD'`: Format error in CRL's lastUpdate field.
* `'ERROR_IN_CRL_NEXT_UPDATE_FIELD'`: Format error in CRL's nextUpdate field.
* `'OUT_OF_MEM'`: Out of memory.
* `'DEPTH_ZERO_SELF_SIGNED_CERT'`: Self signed certificate.
* `'SELF_SIGNED_CERT_IN_CHAIN'`: Self signed certificate in certificate chain.
* `'UNABLE_TO_GET_ISSUER_CERT_LOCALLY'`: Unable to get local issuer certificate.
* `'UNABLE_TO_VERIFY_LEAF_SIGNATURE'`: Unable to verify the first certificate.
* `'CERT_CHAIN_TOO_LONG'`: Certificate chain too long.
* `'CERT_REVOKED'`: Certificate revoked.
* `'INVALID_CA'`: Invalid CA certificate.
* `'PATH_LENGTH_EXCEEDED'`: Path length constraint exceeded.
* `'INVALID_PURPOSE'`: Unsupported certificate purpose.
* `'CERT_UNTRUSTED'`: Certificate not trusted.
* `'CERT_REJECTED'`: Certificate rejected.
* `'HOSTNAME_MISMATCH'`: Hostname mismatch.
## Class: `tls.CryptoStream`
<!-- YAML
added: v0.3.4
deprecated: v0.11.3
-->
> Stability: 0 - Deprecated: Use [`tls.TLSSocket`][] instead.
The `tls.CryptoStream` class represents a stream of encrypted data. This class
is deprecated and should no longer be used.
### `cryptoStream.bytesWritten`
<!-- YAML
added: v0.3.4
deprecated: 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: `tls.SecurePair`
<!-- YAML
added: v0.3.2
deprecated: v0.11.3
-->
> Stability: 0 - Deprecated: Use [`tls.TLSSocket`][] instead.
Returned by [`tls.createSecurePair()`][].
### Event: `'secure'`
<!-- YAML
added: v0.3.2
deprecated: 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
[`'secureConnection'`][]
event, `pair.cleartext.authorized` should be inspected to confirm whether the
certificate used is properly authorized.
## Class: `tls.Server`
<!-- YAML
added: v0.3.2
-->
* Extends: {net.Server}
Accepts encrypted connections using TLS or SSL.
### Event: `'connection'`
<!-- YAML
added: v0.3.2
-->
* `socket` {stream.Duplex}
This event is emitted when a new TCP stream is established, before the TLS
handshake begins. `socket` is typically an object of type [`net.Socket`][] but
will not receive events unlike the socket created from the [`net.Server`][]
`'connection'` event. Usually users will not want to access this event.
This event can also be explicitly emitted by users to inject connections
into the TLS server. In that case, any [`Duplex`][] stream can be passed.
### Event: `'keylog'`
<!-- YAML
added:
- v12.3.0
- v10.20.0
-->
* `line` {Buffer} Line of ASCII text, in NSS `SSLKEYLOGFILE` format.
* `tlsSocket` {tls.TLSSocket} The `tls.TLSSocket` instance on which it was
generated.
The `keylog` event is emitted when key material is generated or received by
a connection to this server (typically before handshake has completed, but not
necessarily). This keying material can be stored for debugging, as it allows
captured TLS traffic to be decrypted. It may be emitted multiple times for
each socket.
A typical use case is to append received lines to a common text file, which
is later used by software (such as Wireshark) to decrypt the traffic:
```js
const logFile = fs.createWriteStream('/tmp/ssl-keys.log', { flags: 'a' });
// ...
server.on('keylog', (line, tlsSocket) => {
if (tlsSocket.remoteAddress !== '...')
return; // Only log keys for a particular IP
logFile.write(line);
});
```
### Event: `'newSession'`
<!-- YAML
added: v0.9.2
changes:
- version: v0.11.12
pr-url: https://github.com/nodejs/node-v0.x-archive/pull/7118
description: The `callback` argument is now supported.
-->
The `'newSession'` event is emitted upon creation of a new TLS session. This may
be used to store sessions in external storage. The data should be provided to
the [`'resumeSession'`][] callback.
The listener callback is passed three arguments when called:
* `sessionId` {Buffer} The TLS session identifier
* `sessionData` {Buffer} The TLS session data
* `callback` {Function} A callback function taking no arguments that must be
invoked in order for data to be sent or received over the secure connection.
Listening for this event will have an effect only on connections established
after the addition of the event listener.
### Event: `'OCSPRequest'`
<!-- YAML
added: 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:
* `certificate` {Buffer} The server certificate
* `issuer` {Buffer} The issuer's certificate
* `callback` {Function} A callback function that must be invoked to provide
the results of the OCSP 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 containing the OCSP response.
Both `certificate` and `issuer` are `Buffer` DER-representations of the
primary and issuer's certificates. These can be used to obtain the OCSP
certificate ID and OCSP endpoint URL.
Alternatively, `callback(null, null)` may be called, indicating that there was
no OCSP response.
Calling `callback(err)` will result in a `socket.destroy(err)` call.
The typical flow of an OCSP Request is as follows:
1. Client connects to the server and sends an `'OCSPRequest'` (via the status
info extension in ClientHello).
2. Server receives the request and emits the `'OCSPRequest'` event, calling the
listener if registered.
3. Server extracts the OCSP URL from either the `certificate` or `issuer` and
performs an [OCSP request][] to the CA.
4. Server receives `'OCSPResponse'` from the CA and sends it back to the client
via the `callback` argument
5. Client validates the response and either destroys the socket or performs a
handshake.
The `issuer` can be `null` if the certificate is either self-signed or the
issuer is not in the root certificates list. (An issuer may be provided
via the `ca` option when establishing the TLS connection.)
Listening for this event will have an effect only on connections established
after the addition of the event listener.
An npm module like [asn1.js][] may be used to parse the certificates.
### Event: `'resumeSession'`
<!-- YAML
added: 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:
* `sessionId` {Buffer} The TLS session identifier
* `callback` {Function} A callback function to be called when the prior session
has been recovered: `callback([err[, sessionData]])`
* `err` {Error}
* `sessionData` {Buffer}
The event listener should perform a lookup in external storage for the
`sessionData` saved by the [`'newSession'`][] event handler using the given
`sessionId`. If found, call `callback(null, sessionData)` to resume the session.
If not found, the session cannot be resumed. `callback()` must be called
without `sessionData` so that the handshake can continue and a new session can
be created. It is possible to call `callback(err)` to terminate the incoming
connection and destroy the socket.
Listening for this event will have an effect only on connections established
after the addition of the event listener.
The following illustrates resuming a TLS session:
```js
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'`
<!-- YAML
added: 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:
* `tlsSocket` {tls.TLSSocket} The established TLS socket.
The `tlsSocket.authorized` property is a `boolean` indicating whether the
client has been verified by one of the supplied Certificate Authorities for the
server. If `tlsSocket.authorized` is `false`, then `socket.authorizationError`
is set to describe how authorization failed. Depending on the settings
of the TLS server, unauthorized connections may still be accepted.
The `tlsSocket.alpnProtocol` property is a string that contains the selected
ALPN protocol. When ALPN has no selected protocol, `tlsSocket.alpnProtocol`
equals `false`.
The `tlsSocket.servername` property is a string containing the server name
requested via SNI.
### Event: `'tlsClientError'`
<!-- YAML
added: 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:
* `exception` {Error} The `Error` object describing the error
* `tlsSocket` {tls.TLSSocket} The `tls.TLSSocket` instance from which the
error originated.
### `server.addContext(hostname, context)`
<!-- YAML
added: v0.5.3
-->
* `hostname` {string} A SNI host name or wildcard (e.g. `'*'`)
* `context` {Object} An object containing any of the possible properties
from the [`tls.createSecureContext()`][] `options` arguments (e.g. `key`,
`cert`, `ca`, etc).
The `server.addContext()` method adds a secure context that will be used if
the client request's SNI name matches the supplied `hostname` (or wildcard).
When there are multiple matching contexts, the most recently added one is
used.
### `server.address()`
<!-- YAML
added: v0.6.0
-->
* Returns: {Object}
Returns the bound address, the address family name, and port of the
server as reported by the operating system. See [`net.Server.address()`][] for
more information.
### `server.close([callback])`
<!-- YAML
added: v0.3.2
-->
* `callback` {Function} A listener callback that will be registered to listen
for the server instance's `'close'` event.
* Returns: {tls.Server}
The `server.close()` method stops the server from accepting new connections.
This function operates asynchronously. The `'close'` event will be emitted
when the server has no more open connections.
### `server.getTicketKeys()`
<!-- YAML
added: v3.0.0
-->
* Returns: {Buffer} A 48-byte buffer containing the session ticket keys.
Returns the session ticket keys.
See [Session Resumption][] for more information.
### `server.listen()`
Starts the server listening for encrypted connections.
This method is identical to [`server.listen()`][] from [`net.Server`][].
### `server.setSecureContext(options)`
<!-- YAML
added: v11.0.0
-->
* `options` {Object} An object containing any of the possible properties from
the [`tls.createSecureContext()`][] `options` arguments (e.g. `key`, `cert`,
`ca`, etc).
The `server.setSecureContext()` method replaces the secure context of an
existing server. Existing connections to the server are not interrupted.
### `server.setTicketKeys(keys)`
<!-- YAML
added: v3.0.0
-->
* `keys` {Buffer|TypedArray|DataView} A 48-byte buffer containing the session
ticket keys.
Sets the session ticket keys.
Changes to the ticket keys are effective only for future server connections.
Existing or currently pending server connections will use the previous keys.
See [Session Resumption][] for more information.
## Class: `tls.TLSSocket`
<!-- YAML
added: v0.11.4
-->
* Extends: {net.Socket}
Performs transparent encryption of written data and all required TLS
negotiation.
Instances of `tls.TLSSocket` implement the duplex [Stream][] interface.
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])`
<!-- YAML
added: v0.11.4
changes:
- version: v12.2.0
pr-url: https://github.com/nodejs/node/pull/27497
description: The `enableTrace` option is now supported.
- version: v5.0.0
pr-url: https://github.com/nodejs/node/pull/2564
description: ALPN options are supported now.
-->
* `socket` {net.Socket|stream.Duplex}
On the server side, any `Duplex` stream. On the client side, any
instance of [`net.Socket`][] (for generic `Duplex` stream support
on the client side, [`tls.connect()`][] must be used).
* `options` {Object}
* `enableTrace`: See [`tls.createServer()`][]
* `isServer`: The SSL/TLS protocol is asymmetrical, TLSSockets must know if
they are to behave as a server or a client. If `true` the TLS socket will be
instantiated as a server. **Default:** `false`.
* `server` {net.Server} A [`net.Server`][] instance.
* `requestCert`: Whether to authenticate the remote peer by requesting a
certificate. Clients always request a server certificate. Servers
(`isServer` is true) may set `requestCert` to true to request a client
certificate.
* `rejectUnauthorized`: See [`tls.createServer()`][]
* `ALPNProtocols`: See [`tls.createServer()`][]
* `SNICallback`: See [`tls.createServer()`][]
* `session` {Buffer} A `Buffer` instance containing a TLS session.
* `requestOCSP` {boolean} If `true`, specifies that 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
* `secureContext`: TLS context object created with
[`tls.createSecureContext()`][]. If a `secureContext` is _not_ provided, one
will be created by passing the entire `options` object to
`tls.createSecureContext()`.
* ...: [`tls.createSecureContext()`][] options that are used if the
`secureContext` option is missing. Otherwise, they are ignored.
Construct a new `tls.TLSSocket` object from an existing TCP socket.
### Event: `'keylog'`
<!-- YAML
added:
- v12.3.0
- v10.20.0
-->
* `line` {Buffer} Line of ASCII text, in NSS `SSLKEYLOGFILE` format.
The `keylog` event is emitted on a `tls.TLSSocket` when key material
is generated or received by the socket. This keying material can be stored
for debugging, as it allows captured TLS traffic to be decrypted. It may
be emitted multiple times, before or after the handshake completes.
A typical use case is to append received lines to a common text file, which
is later used by software (such as Wireshark) to decrypt the traffic:
```js
const logFile = fs.createWriteStream('/tmp/ssl-keys.log', { flags: 'a' });
// ...
tlsSocket.on('keylog', (line) => logFile.write(line));
```
### Event: `'OCSPResponse'`
<!-- YAML
added: 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:
* `response` {Buffer} The server's OCSP response
Typically, the `response` is a digitally signed object from the server's CA that
contains information about server's certificate revocation status.
### Event: `'secureConnect'`
<!-- YAML
added: 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. If
`tlsSocket.authorized === false`, then the error can be found by examining the
`tlsSocket.authorizationError` property. If ALPN was used, the
`tlsSocket.alpnProtocol` property can be checked to determine the negotiated
protocol.
The `'secureConnect'` event is not emitted when a {tls.TLSSocket} is created
using the `new tls.TLSSocket()` constructor.
### Event: `'session'`
<!-- YAML
added: v11.10.0
-->
* `session` {Buffer}
The `'session'` event is emitted on a client `tls.TLSSocket` when a new session
or TLS ticket is available. This may or may not be before the handshake is
complete, depending on the TLS protocol version that was negotiated. The event
is not emitted on the server, or if a new session was not created, for example,
when the connection was resumed. For some TLS protocol versions the event may be
emitted multiple times, in which case all the sessions can be used for
resumption.
On the client, the `session` can be provided to the `session` option of
[`tls.connect()`][] to resume the connection.
See [Session Resumption][] for more information.
For TLSv1.2 and below, [`tls.TLSSocket.getSession()`][] can be called once
the handshake is complete. For TLSv1.3, only ticket-based resumption is allowed
by the protocol, multiple tickets are sent, and the tickets aren't sent until
after the handshake completes. So it is necessary to wait for the
`'session'` event to get a resumable session. Applications
should use the `'session'` event instead of `getSession()` to ensure
they will work for all TLS versions. Applications that only expect to
get or use one session should listen for this event only once:
```js
tlsSocket.once('session', (session) => {
// The session can be used immediately or later.
tls.connect({
session: session,
// Other connect options...
});
});
```
### `tlsSocket.address()`
<!-- YAML
added: v0.11.4
-->
* Returns: {Object}
Returns the bound `address`, the address `family` name, and `port` of the
underlying socket as reported by the operating system:
`{ port: 12346, family: 'IPv4', address: '127.0.0.1' }`.
### `tlsSocket.authorizationError`
<!-- YAML
added: 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`
<!-- YAML
added: v0.11.4
-->
* Returns: {boolean}
Returns `true` if the peer certificate was signed by one of the CAs specified
when creating the `tls.TLSSocket` instance, otherwise `false`.
### `tlsSocket.disableRenegotiation()`
<!-- YAML
added: v8.4.0
-->
Disables TLS renegotiation for this `TLSSocket` instance. Once called, attempts
to renegotiate will trigger an `'error'` event on the `TLSSocket`.
### `tlsSocket.enableTrace()`
<!-- YAML
added: v12.2.0
-->
When enabled, TLS packet trace information is written to `stderr`. This can be
used to debug TLS connection problems.
The format of the output is identical to the output of
`openssl s_client -trace` or `openssl s_server -trace`. While it is produced by
OpenSSL's `SSL_trace()` function, the format is undocumented, can change
without notice, and should not be relied on.
### `tlsSocket.encrypted`
<!-- YAML
added: v0.11.4
-->
Always returns `true`. This may be used to distinguish TLS sockets from regular
`net.Socket` instances.
### `tlsSocket.exportKeyingMaterial(length, label[, context])`
<!-- YAML
added:
- v13.10.0
- v12.17.0
-->
* `length` {number} number of bytes to retrieve from keying material
* `label` {string} an application specific label, typically this will be a
value from the
[IANA Exporter Label Registry](https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#exporter-labels).
* `context` {Buffer} Optionally provide a context.
* Returns: {Buffer} requested bytes of the keying material