* Prevent low-grade poplib REDOS (CVE-2018-1060)

The regex to test a mail server's timestamp is susceptible to
catastrophic backtracking on long evil responses from the server.

Happily, the maximum length of malicious inputs is 2K thanks
to a limit introduced in the fix for CVE-2013-1752.

A 2KB evil response from the mail server would result in small slowdowns
(milliseconds vs. microseconds) accumulated over many apop calls.
This is a potential DOS vector via accumulated slowdowns.

Replace it with a similar non-vulnerable regex.

The new regex is RFC compliant.
The old regex was non-compliant in edge cases.

* Prevent difflib REDOS (CVE-2018-1061)

The default regex for IS_LINE_JUNK is susceptible to
catastrophic backtracking.
This is a potential DOS vector.

Replace it with an equivalent non-vulnerable regex.

Also introduce unit and REDOS tests for difflib.
Co-authored-by: Tim Peters <tim.peters@gmail.com>
Co-authored-by: Christian Heimes <christian@python.org>

The new code also runs faster.

* Revert "bpo-31961: subprocess now accepts path-like args (GH-4329)"

This reverts commit dd42cb71.

The long build queues that plagued macOS builds on Travis seem to be
a thing of the past now.

* Add What's New entry for addition of datetime.timezone to the C API

Closes bpo-10381

* Add what's new entry for date and datetime optimizations

Closes bpo-32403

OpenSSL 1.1 has introduced a new API to set the minimum and maximum
supported protocol version. The API is easier to use than the old
OP_NO_TLS1 option flags, too.

Since OpenSSL has no call to set minimum version to highest supported,
the implementation emulate maximum_version = MINIMUM_SUPPORTED and
minimum_version = MAXIMUM_SUPPORTED by figuring out the minumum and
maximum supported version at compile time.
Signed-off-by: Christian Heimes <christian@python.org>

Direct instantiation of SSLSocket and SSLObject objects is now prohibited.
The constructors were never documented, tested, or designed as public
constructors. The SSLSocket constructor had limitations. For example it was
not possible to enabled hostname verification except was
ssl_version=PROTOCOL_TLS_CLIENT with cert_reqs=CERT_REQUIRED.

SSLContext.wrap_socket() and SSLContext.wrap_bio are the recommended API
to construct SSLSocket and SSLObject instances. ssl.wrap_socket() is
also deprecated.

The only test case for direct instantiation was added a couple of days
ago for IDNA testing.
Signed-off-by: Christian Heimes <christian@python.org>

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>

* bpo-32947: OpenSSL 1.1.1-pre1 / TLS 1.3 fixes

Misc fixes and workarounds for compatibility with OpenSSL 1.1.1-pre1 and
TLS 1.3 support. With OpenSSL 1.1.1, Python negotiates TLS 1.3 by
default. Some test cases only apply to TLS 1.2. Other tests currently
fail because the threaded or async test servers stop after failure.

I'm going to address these issues when OpenSSL 1.1.1 reaches beta.

OpenSSL 1.1.1 has added a new option OP_ENABLE_MIDDLEBOX_COMPAT for TLS
1.3. The feature is enabled by default for maximum compatibility with
broken middle boxes. Users should be able to disable the hack and CPython's test suite needs
it to verify default options.
Signed-off-by: Christian Heimes <christian@python.org>

bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen classes and vice-versa, (GH-5919)

This restriction will be relaxed at a future date.

When comprehensions switched to using a nested scope, the old
code for generating a temporary name to hold the accumulation
target became redundant, but was never actually removed.

Patch by Nitish Chandra.

unsafe_hash=False is now the default. It is the same behavior as the old hash=None parameter. unsafe_hash=True will try to add __hash__. If it already exists, TypeError is raised.

Fixes https://github.com/python/core-workflow/issues/223

By default `print` adds spaces between its arguments.

* Support sendfile on Windows Proactor event loop naively.

This code never did anything correct or useful. The class attribute will never be affected, and the condition will never be true.

Signed-off-by: Christian Heimes <christian@python.org>

The ctypes module used to depend on indirect linking for dlopen. The shared
extension is now explicitly linked against libdl on platforms with dl.
Signed-off-by: Christian Heimes <christian@python.org>