# `ssl` – SSL/TLS module

This module implements a subset of the corresponding CPython module, as described below. For more information, refer to the original CPython documentation: `ssl`.

This module provides access to Transport Layer Security (previously and widely known as “Secure Sockets Layer”) encryption and peer authentication facilities for network sockets, both client-side and server-side.

## Functions

ssl.wrap_socket(sock, server_side=False, keyfile=None, certfile=None, cert_reqs=CERT_NONE, cadata=None, server_hostname=None, do_handshake=True)

  Takes a `stream` sock (usually socket.socket instance of `SOCK_STREAM` type), and returns an instance of ssl.SSLSocket, which wraps the underlying stream in an SSL context. Returned object has the usual `stream` interface methods like `read()`, `write()`, etc. A server-side SSL socket should be created from a normal socket returned from `accept()` on a non-SSL listening server socket.

  - do_handshake determines whether the handshake is done as part of the `wrap_socket` or whether it is deferred to be done as part of the initial reads or writes (there is no `do_handshake` method as in CPython). For blocking sockets doing the handshake immediately is standard. For non-blocking sockets (i.e. when the sock passed into `wrap_socket` is in non-blocking mode) the handshake should generally be deferred because otherwise `wrap_socket` blocks until it completes. Note that in AXTLS the handshake can be deferred until the first read or write but it then blocks until completion.

  - cert_reqs determines whether the peer (server or client) must present a valid certificate. Note that for mbedtls based ports, `ssl.CERT_NONE` and `ssl.CERT_OPTIONAL` will not validate any certificate, only `ssl.CERT_REQUIRED` will.

  - cadata is a bytes object containing the CA certificate chain (in DER format) that will validate the peer’s certificate. Currently only a single DER-encoded certificate is supported.

  - server_hostname is for use as a client, and sets the hostname to check against the received server certificate. It also sets the name for Server Name Indication (SNI), allowing the server to present the proper certificate.

  Depending on the underlying module implementation in a particular MicroPython port, some or all keyword arguments above may be not supported.

Warning

Some implementations of `ssl` module do NOT validate server certificates, which makes an SSL connection established prone to man-in-the-middle attacks.

CPython’s `wrap_socket` returns an `SSLSocket` object which has methods typical for sockets, such as `send`, `recv`, etc. MicroPython’s `wrap_socket` returns an object more similar to CPython’s `SSLObject` which does not have these socket methods.

## Exceptions

ssl.SSLError

  This exception does NOT exist. Instead its base class, OSError, is used.

## Constants

ssl.CERT_NONE
ssl.CERT_OPTIONAL
ssl.CERT_REQUIRED

  Supported values for cert_reqs parameter.

Language and External Links

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External links
  openmv.io
  forums.openmv.io
  github.com/openmv/openmv
  micropython.org
  forum.micropython.org
  github.com/micropython/micropython