Add SSL_CTX_set_min_proto_version/SSL_CTX_set_max_proto_version bindings (#985)

* add Context.set_*_proto_version, fix #860

* docs: add new openssl tls methods

* accept the fact that nothing can be taken for granted

* bump minimum required cryptography version to 3.3

* drop support for Python 3.5

* use binary wheels for cryptography

* Revert "use binary wheels for cryptography"

This reverts commit 91a04c612ed1d0dd9fd541dfefe21cac7c25b1c1.

* docker ci: compile cryptography with rust

8 files changed, 115 insertions, 15 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b65b728..2d45c88 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,7 +11,6 @@ jobs:
         PYTHON:
           # Base builds
           - {VERSION: "2.7", TOXENV: "py27"}
-          - {VERSION: "3.5", TOXENV: "py35"}
           - {VERSION: "3.6", TOXENV: "py36"}
           - {VERSION: "3.7", TOXENV: "py37"}
           - {VERSION: "3.8", TOXENV: "py38"}
@@ -26,7 +25,6 @@ jobs:
           - {VERSION: "pypy3", TOXENV: "pypy3-cryptographyMaster"}
           # -cryptographyMinimum
           - {VERSION: "2.7", TOXENV: "py27-cryptographyMinimum"}
-          - {VERSION: "3.5", TOXENV: "py35-cryptographyMinimum"}
           - {VERSION: "3.6", TOXENV: "py36-cryptographyMinimum"}
           - {VERSION: "3.7", TOXENV: "py37-cryptographyMinimum"}
           - {VERSION: "3.8", TOXENV: "py38-cryptographyMinimum"}
@@ -66,13 +64,14 @@ jobs:
       matrix:
         TEST:
           - {CONTAINER: "stretch", TOXENV: "py27"}
-          - {CONTAINER: "stretch", TOXENV: "py35"}
+          - {CONTAINER: "ubuntu-bionic", TOXENV: "py36"}
     name: "${{ matrix.TEST.TOXENV }} on ${{ matrix.TEST.CONTAINER }}"
     steps:
       - uses: actions/checkout@v2
       - run: tox -v
         env:
           TOXENV: ${{ matrix.TEST.TOXENV }}
+          RUSTUP_HOME: /root/.rustup
       - name: Upload coverage
         run: |
           curl -o codecov.sh -f https://codecov.io/bash || curl -o codecov.sh -f https://codecov.io/bash || curl -o codecov.sh -f https://codecov.io/bash
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 220ee00..85fb1c3 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -10,6 +10,9 @@ The third digit is only for regressions.
 Backward-incompatible changes:
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- The minimum ``cryptography`` version is now 3.3.
+- Drop support for Python 3.5
+
 Deprecations:
 ^^^^^^^^^^^^^
 
@@ -18,6 +21,8 @@ Changes:
 
 - Raise an error when an invalid ALPN value is set.
   `#993 <https://github.com/pyca/pyopenssl/pull/993>`_
+- Added ``OpenSSL.SSL.Context.set_min_proto_version`` and ``OpenSSL.SSL.Context.set_max_proto_version``
+  to set the minimum and maximum supported TLS version `#985 <https://github.com/pyca/pyopenssl/pull/985>`_.
 
 20.0.1 (2020-12-15)
 -------------------
diff --git a/doc/api/ssl.rst b/doc/api/ssl.rst
index ead1452..630ebfc 100644
--- a/doc/api/ssl.rst
+++ b/doc/api/ssl.rst
@@ -10,7 +10,10 @@
 This module handles things specific to SSL. There are two objects defined:
 Context, Connection.
 
-.. py:data:: SSLv2_METHOD
+.. py:data:: TLS_METHOD
+             TLS_SERVER_METHOD
+             TLS_CLIENT_METHOD
+             SSLv2_METHOD
              SSLv3_METHOD
              SSLv23_METHOD
              TLSv1_METHOD
@@ -18,11 +21,21 @@ Context, Connection.
              TLSv1_2_METHOD
 
     These constants represent the different SSL methods to use when creating a
-    context object.  If the underlying OpenSSL build is missing support for any
-    of these protocols, constructing a :py:class:`Context` using the
+    context object. New code should only use ``TLS_METHOD``, ``TLS_SERVER_METHOD``,
+    or ``TLS_CLIENT_METHOD``. If the underlying OpenSSL build is missing support
+    for any of these protocols, constructing a :py:class:`Context` using the
     corresponding :py:const:`*_METHOD` will raise an exception.
 
 
+.. py:data:: SSL3_VERSION
+             TLS1_VERSION
+             TLS1_1_VERSION
+             TLS1_2_VERSION
+             TLS1_3_VERSION
+
+    These constants represent the different TLS versions to use when
+    setting the minimum or maximum TLS version.
+
 .. py:data:: VERIFY_NONE
              VERIFY_PEER
              VERIFY_FAIL_IF_NO_PEER_CERT
diff --git a/doc/introduction.rst b/doc/introduction.rst
index a810fbb..2879829 100644
--- a/doc/introduction.rst
+++ b/doc/introduction.rst
@@ -14,7 +14,7 @@ Other OpenSSL wrappers for Python at the time were also limited, though in diffe
 Later it was maintained by `Jean-Paul Calderone`_ who among other things managed to make pyOpenSSL a pure Python project which the current maintainers are *very* grateful for.
 
 Over the time the standard library's ``ssl`` module improved, never reaching the completeness of pyOpenSSL's API coverage.
-Despite `PEP 466`_ many useful features remain Python 3-only and pyOpenSSL remains the only alternative for full-featured TLS code across all noteworthy Python versions from 2.7 through 3.5 and PyPy_.
+Despite `PEP 466`_ many useful features remain Python 3-only and pyOpenSSL remains the only alternative for full-featured TLS code across all noteworthy Python versions from 2.7 through 3.6 and PyPy_.
 
 
 Development
diff --git a/setup.py b/setup.py
index fbd6571..1ca7b11 100755
--- a/setup.py
+++ b/setup.py
@@ -79,7 +79,6 @@ if __name__ == "__main__":
             "Programming Language :: Python :: 2",
             "Programming Language :: Python :: 2.7",
             "Programming Language :: Python :: 3",
-            "Programming Language :: Python :: 3.5",
             "Programming Language :: Python :: 3.6",
             "Programming Language :: Python :: 3.7",
             "Programming Language :: Python :: 3.8",
@@ -90,12 +89,14 @@ if __name__ == "__main__":
             "Topic :: Software Development :: Libraries :: Python Modules",
             "Topic :: System :: Networking",
         ],
-        python_requires=">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*",
+        python_requires=(
+            ">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,!=3.5.*"
+        ),
         packages=find_packages(where="src"),
         package_dir={"": "src"},
         install_requires=[
             # Fix cryptographyMinimum in tox.ini when changing this!
-            "cryptography>=3.2",
+            "cryptography>=3.3",
             "six>=1.5.2",
         ],
         extras_require={
diff --git a/src/OpenSSL/SSL.py b/src/OpenSSL/SSL.py
index cd1e9be..660cd9f 100644
--- a/src/OpenSSL/SSL.py
+++ b/src/OpenSSL/SSL.py
@@ -44,6 +44,14 @@ __all__ = [
     "TLSv1_METHOD",
     "TLSv1_1_METHOD",
     "TLSv1_2_METHOD",
+    "TLS_METHOD",
+    "TLS_SERVER_METHOD",
+    "TLS_CLIENT_METHOD",
+    "SSL3_VERSION",
+    "TLS1_VERSION",
+    "TLS1_1_VERSION",
+    "TLS1_2_VERSION",
+    "TLS1_3_VERSION",
     "OP_NO_SSLv2",
     "OP_NO_SSLv3",
     "OP_NO_TLSv1",
@@ -139,6 +147,24 @@ SSLv23_METHOD = 3
 TLSv1_METHOD = 4
 TLSv1_1_METHOD = 5
 TLSv1_2_METHOD = 6
+TLS_METHOD = 7
+TLS_SERVER_METHOD = 8
+TLS_CLIENT_METHOD = 9
+
+try:
+    SSL3_VERSION = _lib.SSL3_VERSION
+    TLS1_VERSION = _lib.TLS1_VERSION
+    TLS1_1_VERSION = _lib.TLS1_1_VERSION
+    TLS1_2_VERSION = _lib.TLS1_2_VERSION
+    TLS1_3_VERSION = _lib.TLS1_3_VERSION
+except AttributeError:
+    # Hardcode constants for cryptography < 3.4, see
+    # https://github.com/pyca/pyopenssl/pull/985#issuecomment-775186682
+    SSL3_VERSION = 768
+    TLS1_VERSION = 769
+    TLS1_1_VERSION = 770
+    TLS1_2_VERSION = 771
+    TLS1_3_VERSION = 772
 
 OP_NO_SSLv2 = _lib.SSL_OP_NO_SSLv2
 OP_NO_SSLv3 = _lib.SSL_OP_NO_SSLv3
@@ -603,8 +629,9 @@ class Context(object):
     :class:`OpenSSL.SSL.Context` instances define the parameters for setting
     up new SSL connections.
 
-    :param method: One of SSLv2_METHOD, SSLv3_METHOD, SSLv23_METHOD, or
-        TLSv1_METHOD.
+    :param method: One of TLS_METHOD, TLS_CLIENT_METHOD, or TLS_SERVER_METHOD.
+                   SSLv23_METHOD, TLSv1_METHOD, etc. are deprecated and should
+                   not be used.
     """
 
     _methods = {
@@ -614,6 +641,9 @@ class Context(object):
         TLSv1_METHOD: "TLSv1_method",
         TLSv1_1_METHOD: "TLSv1_1_method",
         TLSv1_2_METHOD: "TLSv1_2_method",
+        TLS_METHOD: "TLS_method",
+        TLS_SERVER_METHOD: "TLS_server_method",
+        TLS_CLIENT_METHOD: "TLS_client_method",
     }
     _methods = dict(
         (identifier, getattr(_lib, name))
@@ -661,6 +691,32 @@ class Context(object):
 
         self.set_mode(_lib.SSL_MODE_ENABLE_PARTIAL_WRITE)
 
+    def set_min_proto_version(self, version):
+        """
+        Set the minimum supported protocol version. Setting the minimum
+        version to 0 will enable protocol versions down to the lowest version
+        supported by the library.
+
+        If the underlying OpenSSL build is missing support for the selected
+        version, this method will raise an exception.
+        """
+        _openssl_assert(
+            _lib.SSL_CTX_set_min_proto_version(self._context, version) == 1
+        )
+
+    def set_max_proto_version(self, version):
+        """
+        Set the maximum supported protocol version. Setting the maximum
+        version to 0 will enable protocol versions up to the highest version
+        supported by the library.
+
+        If the underlying OpenSSL build is missing support for the selected
+        version, this method will raise an exception.
+        """
+        _openssl_assert(
+            _lib.SSL_CTX_set_max_proto_version(self._context, version) == 1
+        )
+
     def load_verify_locations(self, cafile, capath=None):
         """
         Let SSL know where we can find trusted certificates for the certificate
diff --git a/tests/test_ssl.py b/tests/test_ssl.py
index 27f2d43..e79d9fa 100644
--- a/tests/test_ssl.py
+++ b/tests/test_ssl.py
@@ -48,7 +48,14 @@ from OpenSSL.crypto import dump_privatekey, load_privatekey
 from OpenSSL.crypto import dump_certificate, load_certificate
 from OpenSSL.crypto import get_elliptic_curves
 
-from OpenSSL.SSL import OPENSSL_VERSION_NUMBER, SSLEAY_VERSION, SSLEAY_CFLAGS
+from OpenSSL.SSL import (
+    OPENSSL_VERSION_NUMBER,
+    SSLEAY_VERSION,
+    SSLEAY_CFLAGS,
+    TLS_METHOD,
+    TLS1_2_VERSION,
+    TLS1_1_VERSION,
+)
 from OpenSSL.SSL import SSLEAY_PLATFORM, SSLEAY_DIR, SSLEAY_BUILT_ON
 from OpenSSL.SSL import SENT_SHUTDOWN, RECEIVED_SHUTDOWN
 from OpenSSL.SSL import (
@@ -1039,6 +1046,25 @@ class TestContext(object):
         assert all(isinstance(conn, Connection) for conn, line in called)
         assert all(b"CLIENT_RANDOM" in line for conn, line in called)
 
+    def test_set_proto_version(self):
+        server_context = Context(TLS_METHOD)
+        server_context.use_certificate(
+            load_certificate(FILETYPE_PEM, root_cert_pem)
+        )
+        server_context.use_privatekey(
+            load_privatekey(FILETYPE_PEM, root_key_pem)
+        )
+        server_context.set_min_proto_version(TLS1_2_VERSION)
+
+        client_context = Context(TLS_METHOD)
+        client_context.set_max_proto_version(TLS1_1_VERSION)
+
+        with pytest.raises(Error, match="unsupported protocol"):
+            self._handshake_test(server_context, client_context)
+
+        client_context.set_max_proto_version(0)
+        self._handshake_test(server_context, client_context)
+
     def _load_verify_locations_test(self, *args):
         """
         Create a client context which will verify the peer certificate and call
diff --git a/tox.ini b/tox.ini
index 90a4c6a..a4662c4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = {pypy,pypy3,py27,py35,py36,py37,py38,py39}{,-cryptographyMaster,-cryptographyMinimum}{,-randomorder},py37-twistedMaster,pypi-readme,check-manifest,flake8,docs,coverage-report
+envlist = {pypy,pypy3,py27,py36,py37,py38,py39}{,-cryptographyMaster,-cryptographyMinimum}{,-randomorder},py37-twistedMaster,pypi-readme,check-manifest,flake8,docs,coverage-report
 
 [testenv]
 whitelist_externals =
@@ -10,7 +10,7 @@ extras =
 deps =
     coverage>=4.2
     cryptographyMaster: git+https://github.com/pyca/cryptography.git
-    cryptographyMinimum: cryptography==3.2
+    cryptographyMinimum: cryptography==3.3
     randomorder: pytest-randomly
 setenv =
     # Do not allow the executing environment to pollute the test environment