twisted.internet.ssl
module documentationtwisted.internet
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This module implements Transport Layer Security (TLS) support for Twisted. It requires PyOpenSSL.
If you wish to establish a TLS connection, please use one of the following APIs:
servers
and clients
startTLS
connectSSL
listenSSL
These APIs all require a contextFactory
argument that
specifies their security properties, such as certificate, private key,
certificate authorities to verify the peer, allowed TLS protocol versions,
cipher suites, and so on. The recommended value for this argument is a CertificateOptions
instance; see its documentation for an explanation of the available
options.
The contextFactory
name is a bit of an anachronism now, as
context factories have been replaced with "connection creators",
but these objects serve the same role.
Be warned that implementing your own connection creator (i.e.: value for
the contextFactory
) is both difficult and dangerous; the
Twisted team has worked hard to make CertificateOptions
'
API comprehensible and unsurprising, and the Twisted team is actively
maintaining it to ensure that it becomes more secure over time.
If you are really absolutely sure that you want to take on the risk of
implementing your own connection creator based on the pyOpenSSL API, see
the server
connection creator
and client
connection creator
interfaces.
Developers using Twisted, please ignore the Port
, Connector
, and
Client
classes
defined here, as these are details of certain reactors' TLS
implementations, exposed by accident (and remaining here only for
compatibility reasons). If you wish to establish a TLS connection, please
use one of the APIs listed above.
Note | "SSL" (Secure Sockets Layer) is an antiquated synonym for "TLS" (Transport Layer Security). You may see these terms used interchangeably throughout the documentation. |
Class | ContextFactory | A factory for SSL context objects, for server SSL connections. |
Class | DefaultOpenSSLContextFactory | DefaultOpenSSLContextFactory
is a factory for server-side SSL context objects. These objects define
certain parameters related to SSL handshakes and the subsequent
connection. |
Class | ClientContextFactory | A context factory for SSL clients. |
Class | Client | I am an SSL client. |
Class | Server | I am an SSL server. |
Class | Port | I am an SSL port. |
Class | Connector | Undocumented |
Class | KeyPair | No class docstring; 0/2 class methods, 3/10 methods documented |
Class | DistinguishedName | Identify and describe an entity. |
Class | Certificate | An x509 certificate. |
Class | CertificateRequest | An x509 certificate request. |
Class | PrivateCertificate | An x509 certificate and private key. |
Class | AcceptableCiphers | A representation of ciphers that are acceptable for TLS connections. |
Class | CertificateOptions | A CertificateOptions
specifies the security properties for a client or server TLS connection
used with OpenSSL. |
Class | DiffieHellmanParameters | A representation of key generation parameters that are required for Diffie-Hellman key exchange. |
Function | platformTrust | Attempt to discover a set of trusted certificate authority certificates (or, in other words: trust roots, or root certificates) whose trust is managed and updated by tools outside of Twisted. |
Class | OpenSSLDefaultPaths | Trust the set of default verify paths that OpenSSL was built with, as specified by SSL_CTX_set_default_verify_paths. |
Function | optionsForClientTLS | No summary |
Class | ProtocolNegotiationSupport | ProtocolNegotiationSupport
defines flags which are used to indicate the level of NPN/ALPN support
provided by the TLS backend. |
Function | protocolNegotiationMechanisms | Checks whether your versions of PyOpenSSL and OpenSSL are recent enough to support protocol negotiation, and if they are, what kind of protocol negotiation is supported. |
Function | trustRootFromCertificates | Builds an object that trusts multiple root Certificate s. |
Class | TLSVersion | TLS versions that we can negotiate with the client/server. |
Attempt to discover a set of trusted certificate authority certificates (or, in other words: trust roots, or root certificates) whose trust is managed and updated by tools outside of Twisted.
If you are writing any client-side TLS code with Twisted, you should use
this as the trustRoot
argument to CertificateOptions
.
The result of this function should be like the up-to-date list of
certificates in a web browser. When developing code that uses
platformTrust
, you can think of it that way. However, the
choice of which certificate authorities to trust is never Twisted's
responsibility. Unless you're writing a very unusual application or
library, it's not your code's responsibility either. The user may use
platform-specific tools for defining which server certificates should be
trusted by programs using TLS. The purpose of using this API is to respect
that decision as much as possible.
This should be a set of trust settings most appropriate for client TLS connections; i.e. those which need to verify a server's authenticity. You should probably use this by default for any client TLS connection that you create. For servers, however, client certificates are typically not verified; or, if they are, their verification will depend on a custom, application-specific certificate authority.
Returns | an appropriate trust settings object for your platform. (type: IOpenSSLTrustRoot ) | |
Raises | NotImplementedError | if this platform is not yet supported by Twisted. At present, only OpenSSL is supported. |
Present Since | 14.0 | |
Note | Currently, platformTrust
depends entirely upon your OpenSSL build supporting a set of "default verify
paths " which correspond to certificate authority trust
roots. Unfortunately, whether this is true of your system is both outside
of Twisted's control and difficult (if not impossible) for Twisted to
detect automatically.
Nevertheless, this ought to work as desired by default on:
Hopefully soon, this API will be updated to use more sophisticated trust-root discovery mechanisms. Until then, you can follow tickets in the Twisted tracker for progress on this implementation on Microsoft Windows, macOS, and a fallback for other platforms which do not have native trust management tools. |
Create a client
connection creator
for use with APIs such as SSL4ClientEndpoint
,
connectSSL
,
and startTLS
.
Parameters | hostname | The expected name of the remote host. This serves two purposes: first, and
most importantly, it verifies that the certificate received from the server
correctly identifies the specified hostname. The second purpose is to use
the Server Name Indication extension to indicate to the
server which certificate should be used. (type: unicode ) |
trustRoot | Specification of trust requirements of peers. This may be a Certificate
or the result of platformTrust .
By default it is platformTrust
and you probably shouldn't adjust it unless you really know what you're
doing. Be aware that clients using this interface must verify the
server; you cannot explicitly pass None
since that just means to use platformTrust . (type: IOpenSSLTrustRoot ) | |
clientCertificate | The certificate and private key that the client will use to authenticate to
the server. If unspecified, the client will not authenticate. (type: PrivateCertificate ) | |
acceptableProtocols | The protocols this peer is willing to speak after the TLS negotiation has
completed, advertised over both ALPN and NPN. If this argument is
specified, and no overlap can be found with the other peer, the connection
will fail to be established. If the remote peer does not offer NPN or ALPN,
the connection will be established, but no protocol wil be negotiated.
Protocols earlier in the list are preferred over those later in the list. (type: list
of bytes ) | |
extraCertificateOptions | keyword-only argument; this is a dictionary of additional keyword arguments
to be presented to CertificateOptions .
Please avoid using this unless you absolutely need to; any time you need to
pass an option here that is a bug in this interface. (type: dict ) | |
kw | (Backwards compatibility hack to allow keyword-only arguments on Python 2.
Please ignore; arbitrary keyword arguments will be errors.) (type: dict ) | |
Returns | A client connection creator. (type: IOpenSSLClientConnectionCreator ) | |
Present Since | 14.0 |
Checks whether your versions of PyOpenSSL and OpenSSL are recent enough to support protocol negotiation, and if they are, what kind of protocol negotiation is supported.
Returns | A combination of flags from ProtocolNegotiationSupport
that indicate which mechanisms for protocol negotiation are supported. (type: constantly.FlagConstant ) |
Builds an object that trusts multiple root Certificate
s.
When passed to optionsForClientTLS
,
connections using those options will reject any server certificate not
signed by at least one of the certificates in the `certificates` list.
Parameters | certificates | All certificates which will be trusted. (type: iterable of CertBase ) |
Returns | an object suitable for use as the trustRoot= keyword argument to optionsForClientTLS (type: IOpenSSLTrustRoot ) | |
Present Since | 16.0 |