Trait Connection 

pub trait Connection:
    Debug
    + Deref<Target = ConnectionOutputs>
    + DerefMut {
    // Required methods
    fn read_tls(&mut self, rd: &mut dyn Read) -> Result<usize, Error>;
    fn write_tls(&mut self, wr: &mut dyn Write) -> Result<usize, Error>;
    fn wants_read(&self) -> bool;
    fn wants_write(&self) -> bool;
    fn reader(&mut self) -> Reader<'_> ;
    fn writer(&mut self) -> Writer<'_> ;
    fn process_new_packets(&mut self) -> Result<IoState, Error>;
    fn exporter(&mut self) -> Result<KeyingMaterialExporter, Error>;
    fn dangerous_extract_secrets(self) -> Result<ExtractedSecrets, Error>;
    fn set_buffer_limit(&mut self, limit: Option<usize>);
    fn set_plaintext_buffer_limit(&mut self, limit: Option<usize>);
    fn refresh_traffic_keys(&mut self) -> Result<(), Error>;
    fn send_close_notify(&mut self);
    fn is_handshaking(&self) -> bool;
    fn fips(&self) -> FipsStatus;
}

A trait generalizing over buffered client or server connections.

Required Methods

fn read_tls(&mut self, rd: &mut dyn Read) -> Result<usize, Error>

Read TLS content from rd into the internal buffer.

Due to the internal buffering, rd can supply TLS messages in arbitrary-sized chunks (like a socket or pipe might).

You should call process_new_packets() each time a call to this function succeeds in order to empty the incoming TLS data buffer.

This function returns Ok(0) when the underlying rd does so. This typically happens when a socket is cleanly closed, or a file is at EOF. Errors may result from the IO done through rd; additionally, errors of ErrorKind::Other are emitted to signal backpressure:

• In order to empty the incoming TLS data buffer, you should call process_new_packets() each time a call to this function succeeds.
• In order to empty the incoming plaintext data buffer, you should empty it through the reader() after the call to process_new_packets().

This function also returns Ok(0) once a close_notify alert has been successfully received. No additional data is ever read in this state.

fn write_tls(&mut self, wr: &mut dyn Write) -> Result<usize, Error>

Writes TLS messages to wr.

On success, this function returns Ok(n) where n is a number of bytes written to wr (after encoding and encryption).

After this function returns, the connection buffer may not yet be fully flushed. The Connection::wants_write() function can be used to check if the output buffer is empty.

fn wants_read(&self) -> bool

Returns true if the caller should call Connection::read_tls as soon as possible.

If there is pending plaintext data to read with Connection::reader, this returns false. If your application respects this mechanism, only one full TLS message will be buffered by rustls.

fn wants_write(&self) -> bool

Returns true if the caller should call Connection::write_tls as soon as possible.

fn reader(&mut self) -> Reader<'_>

Returns an object that allows reading plaintext.

fn writer(&mut self) -> Writer<'_>

Returns an object that allows writing plaintext.

fn process_new_packets(&mut self) -> Result<IoState, Error>

Processes any new packets read by a previous call to Connection::read_tls.

Errors from this function relate to TLS protocol errors, and are fatal to the connection. Future calls after an error will do no new work and will return the same error. After an error is received from process_new_packets(), you should not call read_tls() any more (it will fill up buffers to no purpose). However, you may call the other methods on the connection, including write, send_close_notify, and write_tls. Most likely you will want to call write_tls to send any alerts queued by the error and then close the underlying connection.

Success from this function comes with some sundry state data about the connection.

fn exporter(&mut self) -> Result<KeyingMaterialExporter, Error>

Returns an object that can derive key material from the agreed connection secrets.

See RFC5705 for more details on what this is for.

This function can be called at most once per connection.

This function will error:

• if called prior to the handshake completing; (check with Connection::is_handshaking() first).
• if called more than once per connection.

fn dangerous_extract_secrets(self) -> Result<ExtractedSecrets, Error>

Extract secrets, so they can be used when configuring kTLS, for example.

Should be used with care as it exposes secret key material.

fn set_buffer_limit(&mut self, limit: Option<usize>)

Sets a limit on the internal buffers used to buffer unsent plaintext (prior to completing the TLS handshake) and unsent TLS records. This limit acts only on application data written through Connection::writer.

By default the limit is 64KB. The limit can be set at any time, even if the current buffer use is higher.

None means no limit applies, and will mean that written data is buffered without bound – it is up to the application to appropriately schedule its plaintext and TLS writes to bound memory usage.

For illustration: Some(1) means a limit of one byte applies: Connection::writer will accept only one byte, encrypt it and add a TLS header. Once this is sent via Connection::write_tls, another byte may be sent.

Internal write-direction buffering

rustls has two buffers whose size are bounded by this setting:

Buffering of unsent plaintext data prior to handshake completion

Calls to Connection::writer before or during the handshake are buffered (up to the limit specified here). Once the handshake completes this data is encrypted and the resulting TLS records are added to the outgoing buffer.

Buffering of outgoing TLS records

This buffer is used to store TLS records that rustls needs to send to the peer. It is used in these two circumstances:

• by Connection::process_new_packets when a handshake or alert TLS record needs to be sent.
• by Connection::writer post-handshake: the plaintext is encrypted and the resulting TLS record is buffered.

This buffer is emptied by Connection::write_tls.

fn set_plaintext_buffer_limit(&mut self, limit: Option<usize>)

Sets a limit on the internal buffers used to buffer decoded plaintext.

See Self::set_buffer_limit for more information on how limits are applied.

fn refresh_traffic_keys(&mut self) -> Result<(), Error>

Sends a TLS1.3 key_update message to refresh a connection’s keys.

This call refreshes our encryption keys. Once the peer receives the message, it refreshes its encryption and decryption keys and sends a response. Once we receive that response, we refresh our decryption keys to match. At the end of this process, keys in both directions have been refreshed.

Note that this process does not happen synchronously: this call just arranges that the key_update message will be included in the next write_tls output.

This fails with Error::HandshakeNotComplete if called before the initial handshake is complete, or if a version prior to TLS1.3 is negotiated.

Usage advice

Note that other implementations (including rustls) may enforce limits on the number of key_update messages allowed on a given connection to prevent denial of service. Therefore, this should be called sparingly.

rustls implicitly and automatically refreshes traffic keys when needed according to the selected cipher suite’s cryptographic constraints. There is therefore no need to call this manually to avoid cryptographic keys “wearing out”.

The main reason to call this manually is to roll keys when it is known a connection will be idle for a long period.

fn send_close_notify(&mut self)

Queues a close_notify warning alert to be sent in the next Connection::write_tls call. This informs the peer that the connection is being closed.

Does nothing if any close_notify or fatal alert was already sent.

fn is_handshaking(&self) -> bool

Returns true if the connection is currently performing the TLS handshake.

During this time plaintext written to the connection is buffered in memory. After Connection::process_new_packets() has been called, this might start to return false while the final handshake packets still need to be extracted from the connection’s buffers.

fn fips(&self) -> FipsStatus

Return the FIPS validation status of the connection.

This is different from CryptoProvider::fips(): it is concerned only with cryptography, whereas this also covers TLS-level configuration that NIST recommends, as well as ECH HPKE suites if applicable.

Implementors

impl Connection for ClientConnection

impl Connection for ServerConnection