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bpo-28124: deprecate ssl.wrap_socket() (#5888) 

The ssl module function ssl.wrap_socket() has been de-emphasized
and deprecated in favor of the more secure and efficient
SSLContext.wrap_socket() method.

Signed-off-by: Christian Heimes <christian@python.org>
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Doc/library/ssl.rst
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@ -59,6 +59,125 @@ by SSL sockets created through the :meth:`SSLContext.wrap_socket` method.
Functions, Constants, and Exceptions
------------------------------------
Socket creation
^^^^^^^^^^^^^^^
Since Python 3.2 and 2.7.9, it is recommended to use the
:meth:`SSLContext.wrap_socket` of an :class:`SSLContext` instance to wrap
sockets as :class:`SSLSocket` objects. The helper functions
:func:`create_default_context` returns a new context with secure default
settings. The old :func:`wrap_socket` function is deprecated since it is
both inefficient and has no support for server name indication (SNI) and
hostname matching.
Client socket example with default context and IPv4/IPv6 dual stack::
import socket
import ssl
hostname = 'www.python.org'
context = ssl.create_default_context()
with socket.create_connection((hostname, 443)) as sock:
with context.wrap_socket(sock, server_hostname=hostname) as ssock:
print(ssock.version())
Client socket example with custom context and IPv4::
hostname = 'www.python.org'
# PROTOCOL_TLS_CLIENT requires valid cert chain and hostname
context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
context.load_verify_locations('path/to/cabundle.pem')
with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock:
with context.wrap_socket(sock, server_hostname=hostname) as ssock:
print(ssock.version())
Server socket example listening on localhost IPv4::
context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
context.load_cert_chain('/path/to/certchain.pem', '/path/to/private.key')
with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock:
sock.bind(('127.0.0.1', 8443))
sock.listen(5)
with context.wrap_socket(sock, server_side=True) as ssock:
conn, addr = ssock.accept()
...
Context creation
^^^^^^^^^^^^^^^^
A convenience function helps create :class:`SSLContext` objects for common
purposes.
.. function:: create_default_context(purpose=Purpose.SERVER_AUTH, cafile=None, capath=None, cadata=None)
Return a new :class:`SSLContext` object with default settings for
the given *purpose*. The settings are chosen by the :mod:`ssl` module,
and usually represent a higher security level than when calling the
:class:`SSLContext` constructor directly.
*cafile*, *capath*, *cadata* represent optional CA certificates to
trust for certificate verification, as in
:meth:`SSLContext.load_verify_locations`. If all three are
:const:`None`, this function can choose to trust the system's default
CA certificates instead.
The settings are: :data:`PROTOCOL_TLS`, :data:`OP_NO_SSLv2`, and
:data:`OP_NO_SSLv3` with high encryption cipher suites without RC4 and
without unauthenticated cipher suites. Passing :data:`~Purpose.SERVER_AUTH`
as *purpose* sets :data:`~SSLContext.verify_mode` to :data:`CERT_REQUIRED`
and either loads CA certificates (when at least one of *cafile*, *capath* or
*cadata* is given) or uses :meth:`SSLContext.load_default_certs` to load
default CA certificates.
.. note::
The protocol, options, cipher and other settings may change to more
restrictive values anytime without prior deprecation. The values
represent a fair balance between compatibility and security.
If your application needs specific settings, you should create a
:class:`SSLContext` and apply the settings yourself.
.. note::
If you find that when certain older clients or servers attempt to connect
with a :class:`SSLContext` created by this function that they get an error
stating "Protocol or cipher suite mismatch", it may be that they only
support SSL3.0 which this function excludes using the
:data:`OP_NO_SSLv3`. SSL3.0 is widely considered to be `completely broken
<https://en.wikipedia.org/wiki/POODLE>`_. If you still wish to continue to
use this function but still allow SSL 3.0 connections you can re-enable
them using::
ctx = ssl.create_default_context(Purpose.CLIENT_AUTH)
ctx.options &= ~ssl.OP_NO_SSLv3
.. versionadded:: 3.4
.. versionchanged:: 3.4.4
RC4 was dropped from the default cipher string.
.. versionchanged:: 3.6
ChaCha20/Poly1305 was added to the default cipher string.
3DES was dropped from the default cipher string.
.. versionchanged:: 3.7
TLS 1.3 cipher suites TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384,
and TLS_CHACHA20_POLY1305_SHA256 were added to the default cipher string.
Exceptions
^^^^^^^^^^
.. exception:: SSLError
Raised to signal an error from the underlying SSL implementation
@ -152,173 +271,6 @@ Functions, Constants, and Exceptions
The exception is now an alias for :exc:`SSLCertVerificationError`.
Socket creation
^^^^^^^^^^^^^^^
The following function allows for standalone socket creation. Starting from
Python 3.2, it can be more flexible to use :meth:`SSLContext.wrap_socket`
instead.
.. function:: wrap_socket(sock, keyfile=None, certfile=None, server_side=False, cert_reqs=CERT_NONE, ssl_version={see docs}, ca_certs=None, do_handshake_on_connect=True, suppress_ragged_eofs=True, ciphers=None)
Takes an instance ``sock`` of :class:`socket.socket`, and returns an instance
of :class:`ssl.SSLSocket`, a subtype of :class:`socket.socket`, which wraps
the underlying socket in an SSL context. ``sock`` must be a
:data:`~socket.SOCK_STREAM` socket; other socket types are unsupported.
For client-side sockets, the context construction is lazy; if the
underlying socket isn't connected yet, the context construction will be
performed after :meth:`connect` is called on the socket. For
server-side sockets, if the socket has no remote peer, it is assumed
to be a listening socket, and the server-side SSL wrapping is
automatically performed on client connections accepted via the
:meth:`accept` method. :func:`wrap_socket` may raise :exc:`SSLError`.
The ``keyfile`` and ``certfile`` parameters specify optional files which
contain a certificate to be used to identify the local side of the
connection. See the discussion of :ref:`ssl-certificates` for more
information on how the certificate is stored in the ``certfile``.
The parameter ``server_side`` is a boolean which identifies whether
server-side or client-side behavior is desired from this socket.
The parameter ``cert_reqs`` specifies whether a certificate is required from
the other side of the connection, and whether it will be validated if
provided. It must be one of the three values :const:`CERT_NONE`
(certificates ignored), :const:`CERT_OPTIONAL` (not required, but validated
if provided), or :const:`CERT_REQUIRED` (required and validated). If the
value of this parameter is not :const:`CERT_NONE`, then the ``ca_certs``
parameter must point to a file of CA certificates.
The ``ca_certs`` file contains a set of concatenated "certification
authority" certificates, which are used to validate certificates passed from
the other end of the connection. See the discussion of
:ref:`ssl-certificates` for more information about how to arrange the
certificates in this file.
The parameter ``ssl_version`` specifies which version of the SSL protocol to
use. Typically, the server chooses a particular protocol version, and the
client must adapt to the server's choice. Most of the versions are not
interoperable with the other versions. If not specified, the default is
:data:`PROTOCOL_TLS`; it provides the most compatibility with other
versions.
Here's a table showing which versions in a client (down the side) can connect
to which versions in a server (along the top):
.. table::
======================== ============ ============ ============= ========= =========== ===========
*client* / **server** **SSLv2** **SSLv3** **TLS** [3]_ **TLSv1** **TLSv1.1** **TLSv1.2**
------------------------ ------------ ------------ ------------- --------- ----------- -----------
*SSLv2* yes no no [1]_ no no no
*SSLv3* no yes no [2]_ no no no
*TLS* (*SSLv23*) [3]_ no [1]_ no [2]_ yes yes yes yes
*TLSv1* no no yes yes no no
*TLSv1.1* no no yes no yes no
*TLSv1.2* no no yes no no yes
======================== ============ ============ ============= ========= =========== ===========
.. rubric:: Footnotes
.. [1] :class:`SSLContext` disables SSLv2 with :data:`OP_NO_SSLv2` by default.
.. [2] :class:`SSLContext` disables SSLv3 with :data:`OP_NO_SSLv3` by default.
.. [3] TLS 1.3 protocol will be available with :data:`PROTOCOL_TLS` in
OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just
TLS 1.3.
.. note::
Which connections succeed will vary depending on the version of
OpenSSL. For example, before OpenSSL 1.0.0, an SSLv23 client
would always attempt SSLv2 connections.
The *ciphers* parameter sets the available ciphers for this SSL object.
It should be a string in the `OpenSSL cipher list format
<https://wiki.openssl.org/index.php/Manual:Ciphers(1)#CIPHER_LIST_FORMAT>`_.
The parameter ``do_handshake_on_connect`` specifies whether to do the SSL
handshake automatically after doing a :meth:`socket.connect`, or whether the
application program will call it explicitly, by invoking the
:meth:`SSLSocket.do_handshake` method. Calling
:meth:`SSLSocket.do_handshake` explicitly gives the program control over the
blocking behavior of the socket I/O involved in the handshake.
The parameter ``suppress_ragged_eofs`` specifies how the
:meth:`SSLSocket.recv` method should signal unexpected EOF from the other end
of the connection. If specified as :const:`True` (the default), it returns a
normal EOF (an empty bytes object) in response to unexpected EOF errors
raised from the underlying socket; if :const:`False`, it will raise the
exceptions back to the caller.
.. versionchanged:: 3.2
New optional argument *ciphers*.
Context creation
^^^^^^^^^^^^^^^^
A convenience function helps create :class:`SSLContext` objects for common
purposes.
.. function:: create_default_context(purpose=Purpose.SERVER_AUTH, cafile=None, capath=None, cadata=None)
Return a new :class:`SSLContext` object with default settings for
the given *purpose*. The settings are chosen by the :mod:`ssl` module,
and usually represent a higher security level than when calling the
:class:`SSLContext` constructor directly.
*cafile*, *capath*, *cadata* represent optional CA certificates to
trust for certificate verification, as in
:meth:`SSLContext.load_verify_locations`. If all three are
:const:`None`, this function can choose to trust the system's default
CA certificates instead.
The settings are: :data:`PROTOCOL_TLS`, :data:`OP_NO_SSLv2`, and
:data:`OP_NO_SSLv3` with high encryption cipher suites without RC4 and
without unauthenticated cipher suites. Passing :data:`~Purpose.SERVER_AUTH`
as *purpose* sets :data:`~SSLContext.verify_mode` to :data:`CERT_REQUIRED`
and either loads CA certificates (when at least one of *cafile*, *capath* or
*cadata* is given) or uses :meth:`SSLContext.load_default_certs` to load
default CA certificates.
.. note::
The protocol, options, cipher and other settings may change to more
restrictive values anytime without prior deprecation. The values
represent a fair balance between compatibility and security.
If your application needs specific settings, you should create a
:class:`SSLContext` and apply the settings yourself.
.. note::
If you find that when certain older clients or servers attempt to connect
with a :class:`SSLContext` created by this function that they get an error
stating "Protocol or cipher suite mismatch", it may be that they only
support SSL3.0 which this function excludes using the
:data:`OP_NO_SSLv3`. SSL3.0 is widely considered to be `completely broken
<https://en.wikipedia.org/wiki/POODLE>`_. If you still wish to continue to
use this function but still allow SSL 3.0 connections you can re-enable
them using::
ctx = ssl.create_default_context(Purpose.CLIENT_AUTH)
ctx.options &= ~ssl.OP_NO_SSLv3
.. versionadded:: 3.4
.. versionchanged:: 3.4.4
RC4 was dropped from the default cipher string.
.. versionchanged:: 3.6
ChaCha20/Poly1305 was added to the default cipher string.
3DES was dropped from the default cipher string.
.. versionchanged:: 3.7
TLS 1.3 cipher suites TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384,
and TLS_CHACHA20_POLY1305_SHA256 were added to the default cipher string.
Random generation
^^^^^^^^^^^^^^^^^
@ -474,9 +426,10 @@ Certificate handling
PEM-encoded string. If ``ssl_version`` is specified, uses that version of
the SSL protocol to attempt to connect to the server. If ``ca_certs`` is
specified, it should be a file containing a list of root certificates, the
same format as used for the same parameter in :func:`wrap_socket`. The call
will attempt to validate the server certificate against that set of root
certificates, and will fail if the validation attempt fails.
same format as used for the same parameter in
:meth:`SSLContext.wrap_socket`. The call will attempt to validate the
server certificate against that set of root certificates, and will fail
if the validation attempt fails.
.. versionchanged:: 3.3
This function is now IPv6-compatible.
@ -552,6 +505,33 @@ Certificate handling
.. versionadded:: 3.4
.. function:: wrap_socket(sock, keyfile=None, certfile=None, \
server_side=False, cert_reqs=CERT_NONE, ssl_version=PROTOCOL_TLS, \
ca_certs=None, do_handshake_on_connect=True, \
suppress_ragged_eofs=True, ciphers=None)
Takes an instance ``sock`` of :class:`socket.socket`, and returns an instance
of :class:`ssl.SSLSocket`, a subtype of :class:`socket.socket`, which wraps
the underlying socket in an SSL context. ``sock`` must be a
:data:`~socket.SOCK_STREAM` socket; other socket types are unsupported.
Internally, function creates a :class:`SSLContext` with protocol
*ssl_version* and :attr:`SSLContext.options` set to *cert_reqs*. If
parameters *keyfile*, *certfile*, *ca_certs* or *ciphers* are set, then
the values are passed to :meth:`SSLContext.load_cert_chain`,
:meth:`SSLContext.load_verify_locations`, and
:meth:`SSLContext.set_ciphers`.
The arguments *server_side*, *do_handshake_on_connect*, and
*suppress_ragged_eofs* have the same meaning as
:meth:`SSLContext.wrap_socket`.
.. deprecated:: 3.7
Since Python 3.2 and 2.7.9, it is recommended to use the
:meth:`SSLContext.wrap_socket` instead of :func:`wrap_socket`. The
top-level function is limited and creates an insecure client socket
without server name indication or hostname matching.
Constants
^^^^^^^^^
@ -1018,7 +998,7 @@ SSL Sockets
the specification of normal, OS-level sockets. See especially the
:ref:`notes on non-blocking sockets <ssl-nonblocking>`.
Usually, :class:`SSLSocket` are not created directly, but using the
:class:`SSLSocket` are not created directly, but using the
:meth:`SSLContext.wrap_socket` method.
.. versionchanged:: 3.5
@ -1257,7 +1237,7 @@ SSL sockets also have the following additional methods and attributes:
.. attribute:: SSLSocket.context
The :class:`SSLContext` object this SSL socket is tied to. If the SSL
socket was created using the top-level :func:`wrap_socket` function
socket was created using the deprecated :func:`wrap_socket` function
(rather than :meth:`SSLContext.wrap_socket`), this is a custom context
object created for this SSL socket.
@ -1310,9 +1290,36 @@ to speed up repeated connections from the same clients.
.. class:: SSLContext(protocol=PROTOCOL_TLS)
Create a new SSL context. You may pass *protocol* which must be one
of the ``PROTOCOL_*`` constants defined in this module.
:data:`PROTOCOL_TLS` is currently recommended for maximum
interoperability and default value.
of the ``PROTOCOL_*`` constants defined in this module. The parameter
specifies which version of the SSL protocol to use. Typically, the
server chooses a particular protocol version, and the client must adapt
to the server's choice. Most of the versions are not interoperable
with the other versions. If not specified, the default is
:data:`PROTOCOL_TLS`; it provides the most compatibility with other
versions.
Here's a table showing which versions in a client (down the side) can connect
to which versions in a server (along the top):
.. table::
======================== ============ ============ ============= ========= =========== ===========
*client* / **server** **SSLv2** **SSLv3** **TLS** [3]_ **TLSv1** **TLSv1.1** **TLSv1.2**
------------------------ ------------ ------------ ------------- --------- ----------- -----------
*SSLv2* yes no no [1]_ no no no
*SSLv3* no yes no [2]_ no no no
*TLS* (*SSLv23*) [3]_ no [1]_ no [2]_ yes yes yes yes
*TLSv1* no no yes yes no no
*TLSv1.1* no no yes no yes no
*TLSv1.2* no no yes no no yes
======================== ============ ============ ============= ========= =========== ===========
.. rubric:: Footnotes
.. [1] :class:`SSLContext` disables SSLv2 with :data:`OP_NO_SSLv2` by default.
.. [2] :class:`SSLContext` disables SSLv3 with :data:`OP_NO_SSLv3` by default.
.. [3] TLS 1.3 protocol will be available with :data:`PROTOCOL_TLS` in
OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just
TLS 1.3.
.. seealso::
:func:`create_default_context` lets the :mod:`ssl` module choose
@ -1645,14 +1652,21 @@ to speed up repeated connections from the same clients.
server_hostname=None, session=None)
Wrap an existing Python socket *sock* and return an instance of
:attr:`SSLContext.sslsocket_class` (default :class:`SSLSocket`).
*sock* must be a :data:`~socket.SOCK_STREAM` socket; other socket
types are unsupported.
:attr:`SSLContext.sslsocket_class` (default :class:`SSLSocket`). The
returned SSL socket is tied to the context, its settings and certificates.
*sock* must be a :data:`~socket.SOCK_STREAM` socket; other
socket types are unsupported.
The returned SSL socket is tied to the context, its settings and
certificates. The parameters *server_side*, *do_handshake_on_connect*
and *suppress_ragged_eofs* have the same meaning as in the top-level
:func:`wrap_socket` function.
The parameter ``server_side`` is a boolean which identifies whether
server-side or client-side behavior is desired from this socket.
For client-side sockets, the context construction is lazy; if the
underlying socket isn't connected yet, the context construction will be
performed after :meth:`connect` is called on the socket. For
server-side sockets, if the socket has no remote peer, it is assumed
to be a listening socket, and the server-side SSL wrapping is
automatically performed on client connections accepted via the
:meth:`accept` method. The method may raise :exc:`SSLError`.
On client connections, the optional parameter *server_hostname* specifies
the hostname of the service which we are connecting to. This allows a
@ -1660,6 +1674,20 @@ to speed up repeated connections from the same clients.
quite similarly to HTTP virtual hosts. Specifying *server_hostname* will
raise a :exc:`ValueError` if *server_side* is true.
The parameter ``do_handshake_on_connect`` specifies whether to do the SSL
handshake automatically after doing a :meth:`socket.connect`, or whether the
application program will call it explicitly, by invoking the
:meth:`SSLSocket.do_handshake` method. Calling
:meth:`SSLSocket.do_handshake` explicitly gives the program control over the
blocking behavior of the socket I/O involved in the handshake.
The parameter ``suppress_ragged_eofs`` specifies how the
:meth:`SSLSocket.recv` method should signal unexpected EOF from the other end
of the connection. If specified as :const:`True` (the default), it returns a
normal EOF (an empty bytes object) in response to unexpected EOF errors
raised from the underlying socket; if :const:`False`, it will raise the
exceptions back to the caller.
*session*, see :attr:`~SSLSocket.session`.
.. versionchanged:: 3.5

5
Doc/whatsnew/3.7.rst
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@ -673,6 +673,11 @@ The ssl module has preliminary and experimental support for TLS 1.3 and
OpenSSL 1.1.1. (Contributed by Christian Heimes in :issue:`32947`,
:issue:`20995`, :issue:`29136`, and :issue:`30622`)
:func:`~ssl.wrap_socket` is deprecated. Documentation has been updated to
recommend :meth:`~ssl.SSLContext.wrap_socket` instead.
(Contributed by Christian Heimes in :issue:`28124`.)
string
------

3
Misc/NEWS.d/next/Documentation/2018-02-25-16-33-35.bpo-28124._uzkgq.rst Normal file
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@ -0,0 +1,3 @@
The ssl module function ssl.wrap_socket() has been de-emphasized
and deprecated in favor of the more secure and efficient
SSLContext.wrap_socket() method.