PEP: 546 Title: Backport ssl.MemoryBIO and ssl.SSLObject to Python 2.7 Version: $Revision$ Last-Modified: $Date$ Author: Victor Stinner , Status: Draft Type: Standards Track Content-Type: text/x-rst Created: 30-May-2017 Abstract ======== Backport the ssl.MemoryBIO and ssl.SSLObject classes from Python 3 to Python 2.7 to enhance the overall security of Python 2.7. Rationale ========= While Python 2.7 is getting closer to its end-of-support date (scheduled for 2020), it is still used on production systems and the Python community is still responsible for its security. This PEP will help facilitate the future adoption of :pep:`543` across all supported Python versions, which will improve security for both Python 2 and Python 3 users. This PEP does NOT propose a general exception for backporting new features to Python 2.7 - every new feature proposed for backporting will still need to be justified independently. In particular, it will need to be explained why relying on an independently updated backport on the Python Package Index instead is not an acceptable solution. PEP 543 ------- :pep:`543` defines a new TLS API for Python which would enhance Python security by giving Python applications access to the native TLS implementations on Windows and macOS, instead of using OpenSSL. A side effect is that it gives access to the system trust store and certificates installed locally by system administrators, enabling Python applications to use "company certificates" without having to modify each application and so to correctly validate TLS certificates (instead of having to ignore or bypass TLS certificate validation). For practical reasons, Cory Benfield would like to first implement an I/O-less class similar to ssl.MemoryBIO and ssl.SSLObject for :pep:`543`, and to provide a second class based on the first one to use sockets or file descriptors. This design would help to structure the code to support more backends and simplify testing and auditing, as well as implementation. Later, optimized classes using directly sockets or file descriptors may be added for performance. While :pep:`543` defines an API, the PEP would only make sense if it comes with at least one complete and good implementation. The first implementation would ideally be based on the ``ssl`` module of the Python standard library, as this is shipped to all users by default and can be used as a fallback implementation in the absence of anything more targetted. If this backport is not performed, the only baseline implementation that could be used would be pyOpenSSL. This is problematic, however, because of the interaction with pip, which is shipped with CPython on all supported versions. requests, pip and ensurepip --------------------------- There are plans afoot to look at moving Requests to a more event-loop-y model, and doing so basically mandates a MemoryBIO. In the absence of a Python 2.7 backport, Requests is required to basically use the same solution that Twisted currently does: namely, a mandatory dependency on `pyOpenSSL `_. The `pip `_ program has to embed all its dependencies for practical reasons: namely, that it cannot rely on any other installation method being present. Since pip depends on requests, it means that it would have to embed a copy of pyOpenSSL. That would imply substantial usability pain to install pip. Currently, pip doesn't support embedding C extensions which must be compiled on each platform and so require a C compiler. Since Python 2.7.9, Python embeds a copy of pip both for default installation and for use in virtual environments via the new ``ensurepip`` module. If pip ends up bundling PyOpenSSL, then CPython will end up bundling PyOpenSSL. Only backporting ``ssl.MemoryBIO`` and ``ssl.SSLObject`` would avoid the need to embed pyOpenSSL, and would fix the bootstrap issue (python -> ensurepip -> pip -> requests -> MemoryBIO). Changes ======= Add ``MemoryBIO`` and ``SSLObject`` classes to the ``ssl`` module of Python 2.7. The code will be backported and adapted from the master branch (Python 3). The backport also significantly reduced the size of the Python 2/Python 3 difference of the ``_ssl`` module, which make maintenance easier. Links ===== * :pep:`543` * `[backport] ssl.MemoryBIO `_: Implementation of this PEP written by Alex Gaynor (first version written at October 2014) * :pep:`466` Discussions =========== * `[Python-Dev] Backport ssl.MemoryBIO on Python 2.7? `_ (May 2017) Copyright ========= This document has been placed in the public domain. .. Local Variables: mode: indented-text indent-tabs-mode: nil sentence-end-double-space: t fill-column: 70 coding: utf-8 End: