| from __future__ import absolute_import |
| import errno |
| import warnings |
| import hmac |
| |
| from binascii import hexlify, unhexlify |
| from hashlib import md5, sha1, sha256 |
| |
| from ..exceptions import SSLError, InsecurePlatformWarning, SNIMissingWarning |
| |
| |
| SSLContext = None |
| HAS_SNI = False |
| create_default_context = None |
| |
| # Maps the length of a digest to a possible hash function producing this digest |
| HASHFUNC_MAP = { |
| 32: md5, |
| 40: sha1, |
| 64: sha256, |
| } |
| |
| |
| def _const_compare_digest_backport(a, b): |
| """ |
| Compare two digests of equal length in constant time. |
| |
| The digests must be of type str/bytes. |
| Returns True if the digests match, and False otherwise. |
| """ |
| result = abs(len(a) - len(b)) |
| for l, r in zip(bytearray(a), bytearray(b)): |
| result |= l ^ r |
| return result == 0 |
| |
| |
| _const_compare_digest = getattr(hmac, 'compare_digest', |
| _const_compare_digest_backport) |
| |
| |
| try: # Test for SSL features |
| import ssl |
| from ssl import wrap_socket, CERT_NONE, PROTOCOL_SSLv23 |
| from ssl import HAS_SNI # Has SNI? |
| except ImportError: |
| pass |
| |
| |
| try: |
| from ssl import OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION |
| except ImportError: |
| OP_NO_SSLv2, OP_NO_SSLv3 = 0x1000000, 0x2000000 |
| OP_NO_COMPRESSION = 0x20000 |
| |
| # A secure default. |
| # Sources for more information on TLS ciphers: |
| # |
| # - https://wiki.mozilla.org/Security/Server_Side_TLS |
| # - https://www.ssllabs.com/projects/best-practices/index.html |
| # - https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/ |
| # |
| # The general intent is: |
| # - Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE), |
| # - prefer ECDHE over DHE for better performance, |
| # - prefer any AES-GCM over any AES-CBC for better performance and security, |
| # - use 3DES as fallback which is secure but slow, |
| # - disable NULL authentication, MD5 MACs and DSS for security reasons. |
| DEFAULT_CIPHERS = ( |
| 'ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+HIGH:' |
| 'DH+HIGH:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+HIGH:RSA+3DES:!aNULL:' |
| '!eNULL:!MD5' |
| ) |
| |
| try: |
| from ssl import SSLContext # Modern SSL? |
| except ImportError: |
| import sys |
| |
| class SSLContext(object): # Platform-specific: Python 2 & 3.1 |
| supports_set_ciphers = ((2, 7) <= sys.version_info < (3,) or |
| (3, 2) <= sys.version_info) |
| |
| def __init__(self, protocol_version): |
| self.protocol = protocol_version |
| # Use default values from a real SSLContext |
| self.check_hostname = False |
| self.verify_mode = ssl.CERT_NONE |
| self.ca_certs = None |
| self.options = 0 |
| self.certfile = None |
| self.keyfile = None |
| self.ciphers = None |
| |
| def load_cert_chain(self, certfile, keyfile): |
| self.certfile = certfile |
| self.keyfile = keyfile |
| |
| def load_verify_locations(self, cafile=None, capath=None): |
| self.ca_certs = cafile |
| |
| if capath is not None: |
| raise SSLError("CA directories not supported in older Pythons") |
| |
| def set_ciphers(self, cipher_suite): |
| if not self.supports_set_ciphers: |
| raise TypeError( |
| 'Your version of Python does not support setting ' |
| 'a custom cipher suite. Please upgrade to Python ' |
| '2.7, 3.2, or later if you need this functionality.' |
| ) |
| self.ciphers = cipher_suite |
| |
| def wrap_socket(self, socket, server_hostname=None): |
| warnings.warn( |
| 'A true SSLContext object is not available. This prevents ' |
| 'urllib3 from configuring SSL appropriately and may cause ' |
| 'certain SSL connections to fail. For more information, see ' |
| 'https://urllib3.readthedocs.org/en/latest/security.html' |
| '#insecureplatformwarning.', |
| InsecurePlatformWarning |
| ) |
| kwargs = { |
| 'keyfile': self.keyfile, |
| 'certfile': self.certfile, |
| 'ca_certs': self.ca_certs, |
| 'cert_reqs': self.verify_mode, |
| 'ssl_version': self.protocol, |
| } |
| if self.supports_set_ciphers: # Platform-specific: Python 2.7+ |
| return wrap_socket(socket, ciphers=self.ciphers, **kwargs) |
| else: # Platform-specific: Python 2.6 |
| return wrap_socket(socket, **kwargs) |
| |
| |
| def assert_fingerprint(cert, fingerprint): |
| """ |
| Checks if given fingerprint matches the supplied certificate. |
| |
| :param cert: |
| Certificate as bytes object. |
| :param fingerprint: |
| Fingerprint as string of hexdigits, can be interspersed by colons. |
| """ |
| |
| fingerprint = fingerprint.replace(':', '').lower() |
| digest_length = len(fingerprint) |
| hashfunc = HASHFUNC_MAP.get(digest_length) |
| if not hashfunc: |
| raise SSLError( |
| 'Fingerprint of invalid length: {0}'.format(fingerprint)) |
| |
| # We need encode() here for py32; works on py2 and p33. |
| fingerprint_bytes = unhexlify(fingerprint.encode()) |
| |
| cert_digest = hashfunc(cert).digest() |
| |
| if not _const_compare_digest(cert_digest, fingerprint_bytes): |
| raise SSLError('Fingerprints did not match. Expected "{0}", got "{1}".' |
| .format(fingerprint, hexlify(cert_digest))) |
| |
| |
| def resolve_cert_reqs(candidate): |
| """ |
| Resolves the argument to a numeric constant, which can be passed to |
| the wrap_socket function/method from the ssl module. |
| Defaults to :data:`ssl.CERT_NONE`. |
| If given a string it is assumed to be the name of the constant in the |
| :mod:`ssl` module or its abbrevation. |
| (So you can specify `REQUIRED` instead of `CERT_REQUIRED`. |
| If it's neither `None` nor a string we assume it is already the numeric |
| constant which can directly be passed to wrap_socket. |
| """ |
| if candidate is None: |
| return CERT_NONE |
| |
| if isinstance(candidate, str): |
| res = getattr(ssl, candidate, None) |
| if res is None: |
| res = getattr(ssl, 'CERT_' + candidate) |
| return res |
| |
| return candidate |
| |
| |
| def resolve_ssl_version(candidate): |
| """ |
| like resolve_cert_reqs |
| """ |
| if candidate is None: |
| return PROTOCOL_SSLv23 |
| |
| if isinstance(candidate, str): |
| res = getattr(ssl, candidate, None) |
| if res is None: |
| res = getattr(ssl, 'PROTOCOL_' + candidate) |
| return res |
| |
| return candidate |
| |
| |
| def create_urllib3_context(ssl_version=None, cert_reqs=None, |
| options=None, ciphers=None): |
| """All arguments have the same meaning as ``ssl_wrap_socket``. |
| |
| By default, this function does a lot of the same work that |
| ``ssl.create_default_context`` does on Python 3.4+. It: |
| |
| - Disables SSLv2, SSLv3, and compression |
| - Sets a restricted set of server ciphers |
| |
| If you wish to enable SSLv3, you can do:: |
| |
| from urllib3.util import ssl_ |
| context = ssl_.create_urllib3_context() |
| context.options &= ~ssl_.OP_NO_SSLv3 |
| |
| You can do the same to enable compression (substituting ``COMPRESSION`` |
| for ``SSLv3`` in the last line above). |
| |
| :param ssl_version: |
| The desired protocol version to use. This will default to |
| PROTOCOL_SSLv23 which will negotiate the highest protocol that both |
| the server and your installation of OpenSSL support. |
| :param cert_reqs: |
| Whether to require the certificate verification. This defaults to |
| ``ssl.CERT_REQUIRED``. |
| :param options: |
| Specific OpenSSL options. These default to ``ssl.OP_NO_SSLv2``, |
| ``ssl.OP_NO_SSLv3``, ``ssl.OP_NO_COMPRESSION``. |
| :param ciphers: |
| Which cipher suites to allow the server to select. |
| :returns: |
| Constructed SSLContext object with specified options |
| :rtype: SSLContext |
| """ |
| context = SSLContext(ssl_version or ssl.PROTOCOL_SSLv23) |
| |
| # Setting the default here, as we may have no ssl module on import |
| cert_reqs = ssl.CERT_REQUIRED if cert_reqs is None else cert_reqs |
| |
| if options is None: |
| options = 0 |
| # SSLv2 is easily broken and is considered harmful and dangerous |
| options |= OP_NO_SSLv2 |
| # SSLv3 has several problems and is now dangerous |
| options |= OP_NO_SSLv3 |
| # Disable compression to prevent CRIME attacks for OpenSSL 1.0+ |
| # (issue #309) |
| options |= OP_NO_COMPRESSION |
| |
| context.options |= options |
| |
| if getattr(context, 'supports_set_ciphers', True): # Platform-specific: Python 2.6 |
| context.set_ciphers(ciphers or DEFAULT_CIPHERS) |
| |
| context.verify_mode = cert_reqs |
| if getattr(context, 'check_hostname', None) is not None: # Platform-specific: Python 3.2 |
| # We do our own verification, including fingerprints and alternative |
| # hostnames. So disable it here |
| context.check_hostname = False |
| return context |
| |
| |
| def ssl_wrap_socket(sock, keyfile=None, certfile=None, cert_reqs=None, |
| ca_certs=None, server_hostname=None, |
| ssl_version=None, ciphers=None, ssl_context=None, |
| ca_cert_dir=None): |
| """ |
| All arguments except for server_hostname, ssl_context, and ca_cert_dir have |
| the same meaning as they do when using :func:`ssl.wrap_socket`. |
| |
| :param server_hostname: |
| When SNI is supported, the expected hostname of the certificate |
| :param ssl_context: |
| A pre-made :class:`SSLContext` object. If none is provided, one will |
| be created using :func:`create_urllib3_context`. |
| :param ciphers: |
| A string of ciphers we wish the client to support. This is not |
| supported on Python 2.6 as the ssl module does not support it. |
| :param ca_cert_dir: |
| A directory containing CA certificates in multiple separate files, as |
| supported by OpenSSL's -CApath flag or the capath argument to |
| SSLContext.load_verify_locations(). |
| """ |
| context = ssl_context |
| if context is None: |
| context = create_urllib3_context(ssl_version, cert_reqs, |
| ciphers=ciphers) |
| |
| if ca_certs or ca_cert_dir: |
| try: |
| context.load_verify_locations(ca_certs, ca_cert_dir) |
| except IOError as e: # Platform-specific: Python 2.6, 2.7, 3.2 |
| raise SSLError(e) |
| # Py33 raises FileNotFoundError which subclasses OSError |
| # These are not equivalent unless we check the errno attribute |
| except OSError as e: # Platform-specific: Python 3.3 and beyond |
| if e.errno == errno.ENOENT: |
| raise SSLError(e) |
| raise |
| |
| if certfile: |
| context.load_cert_chain(certfile, keyfile) |
| if HAS_SNI: # Platform-specific: OpenSSL with enabled SNI |
| return context.wrap_socket(sock, server_hostname=server_hostname) |
| |
| warnings.warn( |
| 'An HTTPS request has been made, but the SNI (Subject Name ' |
| 'Indication) extension to TLS is not available on this platform. ' |
| 'This may cause the server to present an incorrect TLS ' |
| 'certificate, which can cause validation failures. For more ' |
| 'information, see ' |
| 'https://urllib3.readthedocs.org/en/latest/security.html' |
| '#snimissingwarning.', |
| SNIMissingWarning |
| ) |
| return context.wrap_socket(sock) |
