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# -*- test-case-name: twisted.test.test_sslverify -*- # Copyright (c) 2005 Divmod, Inc. # Copyright (c) Twisted Matrix Laboratories. # See LICENSE for details. import warnings from binascii import hexlify from functools import lru_cache from hashlib import md5 from zope.interface import Interface, implementer from OpenSSL import SSL, crypto from OpenSSL._util import lib as pyOpenSSLlib # type: ignore[import] import attr from constantly import FlagConstant, Flags, NamedConstant, Names # type: ignore[import] from incremental import Version from twisted.internet.abstract import isIPAddress, isIPv6Address from twisted.internet.defer import Deferred from twisted.internet.error import CertificateError, VerifyError from twisted.internet.interfaces import ( IAcceptableCiphers, ICipher, IOpenSSLClientConnectionCreator, IOpenSSLContextFactory, ) from twisted.python import log, util from twisted.python.compat import nativeString from twisted.python.deprecate import _mutuallyExclusiveArguments, deprecated from twisted.python.failure import Failure from twisted.python.randbytes import secureRandom from ._idna import _idnaBytes class TLSVersion(Names): """ TLS versions that we can negotiate with the client/server. """ SSLv3 = NamedConstant() TLSv1_0 = NamedConstant() TLSv1_1 = NamedConstant() TLSv1_2 = NamedConstant() TLSv1_3 = NamedConstant() _tlsDisableFlags = { TLSVersion.SSLv3: SSL.OP_NO_SSLv3, TLSVersion.TLSv1_0: SSL.OP_NO_TLSv1, TLSVersion.TLSv1_1: SSL.OP_NO_TLSv1_1, TLSVersion.TLSv1_2: SSL.OP_NO_TLSv1_2, # If we don't have TLS v1.3 yet, we can't disable it -- this is just so # when it makes it into OpenSSL, connections knowingly bracketed to v1.2 # don't end up going to v1.3 TLSVersion.TLSv1_3: getattr(SSL, "OP_NO_TLSv1_3", 0x00), } def _getExcludedTLSProtocols(oldest, newest): """ Given a pair of L{TLSVersion} constants, figure out what versions we want to disable (as OpenSSL is an exclusion based API). @param oldest: The oldest L{TLSVersion} we want to allow. @type oldest: L{TLSVersion} constant @param newest: The newest L{TLSVersion} we want to allow, or L{None} for no upper limit. @type newest: L{TLSVersion} constant or L{None} @return: The versions we want to disable. @rtype: L{list} of L{TLSVersion} constants. """ versions = list(TLSVersion.iterconstants()) excludedVersions = [x for x in versions[: versions.index(oldest)]] if newest: excludedVersions.extend([x for x in versions[versions.index(newest) :]]) return excludedVersions class SimpleVerificationError(Exception): """ Not a very useful verification error. """ def simpleVerifyHostname(connection, hostname): """ Check only the common name in the certificate presented by the peer and only for an exact match. This is to provide I{something} in the way of hostname verification to users who haven't installed C{service_identity}. This check is overly strict, relies on a deprecated TLS feature (you're supposed to ignore the commonName if the subjectAlternativeName extensions are present, I believe), and lots of valid certificates will fail. @param connection: the OpenSSL connection to verify. @type connection: L{OpenSSL.SSL.Connection} @param hostname: The hostname expected by the user. @type hostname: L{unicode} @raise twisted.internet.ssl.VerificationError: if the common name and hostname don't match. """ commonName = connection.get_peer_certificate().get_subject().commonName if commonName != hostname: raise SimpleVerificationError(repr(commonName) + "!=" + repr(hostname)) def simpleVerifyIPAddress(connection, hostname): """ Always fails validation of IP addresses @param connection: the OpenSSL connection to verify. @type connection: L{OpenSSL.SSL.Connection} @param hostname: The hostname expected by the user. @type hostname: L{unicode} @raise twisted.internet.ssl.VerificationError: Always raised """ raise SimpleVerificationError("Cannot verify certificate IP addresses") def _usablePyOpenSSL(version): """ Check pyOpenSSL version string whether we can use it for host verification. @param version: A pyOpenSSL version string. @type version: L{str} @rtype: L{bool} """ major, minor = (int(part) for part in version.split(".")[:2]) return (major, minor) >= (0, 12) def _selectVerifyImplementation(): """ Determine if C{service_identity} is installed. If so, use it. If not, use simplistic and incorrect checking as implemented in L{simpleVerifyHostname}. @return: 2-tuple of (C{verify_hostname}, C{VerificationError}) @rtype: L{tuple} """ whatsWrong = ( "Without the service_identity module, Twisted can perform only " "rudimentary TLS client hostname verification. Many valid " "certificate/hostname mappings may be rejected." ) try: from service_identity import VerificationError # type: ignore[import] from service_identity.pyopenssl import ( # type: ignore[import] verify_hostname, verify_ip_address, ) return verify_hostname, verify_ip_address, VerificationError except ImportError as e: warnings.warn_explicit( "You do not have a working installation of the " "service_identity module: '" + str(e) + "'. " "Please install it from " "<https://pypi.python.org/pypi/service_identity> and make " "sure all of its dependencies are satisfied. " + whatsWrong, # Unfortunately the lineno is required. category=UserWarning, filename="", lineno=0, ) return simpleVerifyHostname, simpleVerifyIPAddress, SimpleVerificationError verifyHostname, verifyIPAddress, VerificationError = _selectVerifyImplementation() class ProtocolNegotiationSupport(Flags): """ L{ProtocolNegotiationSupport} defines flags which are used to indicate the level of NPN/ALPN support provided by the TLS backend. @cvar NOSUPPORT: There is no support for NPN or ALPN. This is exclusive with both L{NPN} and L{ALPN}. @cvar NPN: The implementation supports Next Protocol Negotiation. @cvar ALPN: The implementation supports Application Layer Protocol Negotiation. """ NPN = FlagConstant(0x0001) ALPN = FlagConstant(0x0002) # FIXME: https://twistedmatrix.com/trac/ticket/8074 # Currently flags with literal zero values behave incorrectly. However, # creating a flag by NOTing a flag with itself appears to work totally fine, so # do that instead. ProtocolNegotiationSupport.NOSUPPORT = ( ProtocolNegotiationSupport.NPN ^ ProtocolNegotiationSupport.NPN ) def protocolNegotiationMechanisms(): """ Checks whether your versions of PyOpenSSL and OpenSSL are recent enough to support protocol negotiation, and if they are, what kind of protocol negotiation is supported. @return: A combination of flags from L{ProtocolNegotiationSupport} that indicate which mechanisms for protocol negotiation are supported. @rtype: L{constantly.FlagConstant} """ support = ProtocolNegotiationSupport.NOSUPPORT ctx = SSL.Context(SSL.SSLv23_METHOD) try: ctx.set_npn_advertise_callback(lambda c: None) except (AttributeError, NotImplementedError): pass else: support |= ProtocolNegotiationSupport.NPN try: ctx.set_alpn_select_callback(lambda c: None) except (AttributeError, NotImplementedError): pass else: support |= ProtocolNegotiationSupport.ALPN return support _x509names = { "CN": "commonName", "commonName": "commonName", "O": "organizationName", "organizationName": "organizationName", "OU": "organizationalUnitName", "organizationalUnitName": "organizationalUnitName", "L": "localityName", "localityName": "localityName", "ST": "stateOrProvinceName", "stateOrProvinceName": "stateOrProvinceName", "C": "countryName", "countryName": "countryName", "emailAddress": "emailAddress", } class DistinguishedName(dict): """ Identify and describe an entity. Distinguished names are used to provide a minimal amount of identifying information about a certificate issuer or subject. They are commonly created with one or more of the following fields:: commonName (CN) organizationName (O) organizationalUnitName (OU) localityName (L) stateOrProvinceName (ST) countryName (C) emailAddress A L{DistinguishedName} should be constructed using keyword arguments whose keys can be any of the field names above (as a native string), and the values are either Unicode text which is encodable to ASCII, or L{bytes} limited to the ASCII subset. Any fields passed to the constructor will be set as attributes, accessible using both their extended name and their shortened acronym. The attribute values will be the ASCII-encoded bytes. For example:: >>> dn = DistinguishedName(commonName=b'www.example.com', ... C='US') >>> dn.C b'US' >>> dn.countryName b'US' >>> hasattr(dn, "organizationName") False L{DistinguishedName} instances can also be used as dictionaries; the keys are extended name of the fields:: >>> dn.keys() ['countryName', 'commonName'] >>> dn['countryName'] b'US' """ __slots__ = () def __init__(self, **kw): for k, v in kw.items(): setattr(self, k, v) def _copyFrom(self, x509name): for name in _x509names: value = getattr(x509name, name, None) if value is not None: setattr(self, name, value) def _copyInto(self, x509name): for k, v in self.items(): setattr(x509name, k, nativeString(v)) def __repr__(self) -> str: return "<DN %s>" % (dict.__repr__(self)[1:-1]) def __getattr__(self, attr): try: return self[_x509names[attr]] except KeyError: raise AttributeError(attr) def __setattr__(self, attr, value): if attr not in _x509names: raise AttributeError(f"{attr} is not a valid OpenSSL X509 name field") realAttr = _x509names[attr] if not isinstance(value, bytes): value = value.encode("ascii") self[realAttr] = value def inspect(self): """ Return a multi-line, human-readable representation of this DN. @rtype: L{str} """ l = [] lablen = 0 def uniqueValues(mapping): return set(mapping.values()) for k in sorted(uniqueValues(_x509names)): label = util.nameToLabel(k) lablen = max(len(label), lablen) v = getattr(self, k, None) if v is not None: l.append((label, nativeString(v))) lablen += 2 for n, (label, attrib) in enumerate(l): l[n] = label.rjust(lablen) + ": " + attrib return "\n".join(l) DN = DistinguishedName class CertBase: """ Base class for public (certificate only) and private (certificate + key pair) certificates. @ivar original: The underlying OpenSSL certificate object. @type original: L{OpenSSL.crypto.X509} """ def __init__(self, original): self.original = original def _copyName(self, suffix): dn = DistinguishedName() dn._copyFrom(getattr(self.original, "get_" + suffix)()) return dn def getSubject(self): """ Retrieve the subject of this certificate. @return: A copy of the subject of this certificate. @rtype: L{DistinguishedName} """ return self._copyName("subject") def __conform__(self, interface): """ Convert this L{CertBase} into a provider of the given interface. @param interface: The interface to conform to. @type interface: L{zope.interface.interfaces.IInterface} @return: an L{IOpenSSLTrustRoot} provider or L{NotImplemented} @rtype: L{IOpenSSLTrustRoot} or L{NotImplemented} """ if interface is IOpenSSLTrustRoot: return OpenSSLCertificateAuthorities([self.original]) return NotImplemented def _handleattrhelper(Class, transport, methodName): """ (private) Helper for L{Certificate.peerFromTransport} and L{Certificate.hostFromTransport} which checks for incompatible handle types and null certificates and raises the appropriate exception or returns the appropriate certificate object. """ method = getattr(transport.getHandle(), f"get_{methodName}_certificate", None) if method is None: raise CertificateError( "non-TLS transport {!r} did not have {} certificate".format( transport, methodName ) ) cert = method() if cert is None: raise CertificateError( "TLS transport {!r} did not have {} certificate".format( transport, methodName ) ) return Class(cert) class Certificate(CertBase): """ An x509 certificate. """ def __repr__(self) -> str: return "<{} Subject={} Issuer={}>".format( self.__class__.__name__, self.getSubject().commonName, self.getIssuer().commonName, ) def __eq__(self, other: object) -> bool: if isinstance(other, Certificate): return self.dump() == other.dump() return NotImplemented @classmethod def load(Class, requestData, format=crypto.FILETYPE_ASN1, args=()): """ Load a certificate from an ASN.1- or PEM-format string. @rtype: C{Class} """ return Class(crypto.load_certificate(format, requestData), *args) # We can't use super() because it is old style still, so we have to hack # around things wanting to call the parent function _load = load def dumpPEM(self): """ Dump this certificate to a PEM-format data string. @rtype: L{str} """ return self.dump(crypto.FILETYPE_PEM) @classmethod def loadPEM(Class, data): """ Load a certificate from a PEM-format data string. @rtype: C{Class} """ return Class.load(data, crypto.FILETYPE_PEM) @classmethod def peerFromTransport(Class, transport): """ Get the certificate for the remote end of the given transport. @param transport: an L{ISystemHandle} provider @rtype: C{Class} @raise CertificateError: if the given transport does not have a peer certificate. """ return _handleattrhelper(Class, transport, "peer") @classmethod def hostFromTransport(Class, transport): """ Get the certificate for the local end of the given transport. @param transport: an L{ISystemHandle} provider; the transport we will @rtype: C{Class} @raise CertificateError: if the given transport does not have a host certificate. """ return _handleattrhelper(Class, transport, "host") def getPublicKey(self): """ Get the public key for this certificate. @rtype: L{PublicKey} """ return PublicKey(self.original.get_pubkey()) def dump(self, format=crypto.FILETYPE_ASN1): return crypto.dump_certificate(format, self.original) def serialNumber(self): """ Retrieve the serial number of this certificate. @rtype: L{int} """ return self.original.get_serial_number() def digest(self, method="md5"): """ Return a digest hash of this certificate using the specified hash algorithm. @param method: One of C{'md5'} or C{'sha'}. @return: The digest of the object, formatted as b":"-delimited hex pairs @rtype: L{bytes} """ return self.original.digest(method) def _inspect(self): return "\n".join( [ "Certificate For Subject:", self.getSubject().inspect(), "\nIssuer:", self.getIssuer().inspect(), "\nSerial Number: %d" % self.serialNumber(), "Digest: %s" % nativeString(self.digest()), ] ) def inspect(self): """ Return a multi-line, human-readable representation of this Certificate, including information about the subject, issuer, and public key. """ return "\n".join((self._inspect(), self.getPublicKey().inspect())) def getIssuer(self): """ Retrieve the issuer of this certificate. @rtype: L{DistinguishedName} @return: A copy of the issuer of this certificate. """ return self._copyName("issuer") def options(self, *authorities): raise NotImplementedError("Possible, but doubtful we need this yet") class CertificateRequest(CertBase): """ An x509 certificate request. Certificate requests are given to certificate authorities to be signed and returned resulting in an actual certificate. """ @classmethod def load(Class, requestData, requestFormat=crypto.FILETYPE_ASN1): req = crypto.load_certificate_request(requestFormat, requestData) dn = DistinguishedName() dn._copyFrom(req.get_subject()) if not req.verify(req.get_pubkey()): raise VerifyError(f"Can't verify that request for {dn!r} is self-signed.") return Class(req) def dump(self, format=crypto.FILETYPE_ASN1): return crypto.dump_certificate_request(format, self.original) class PrivateCertificate(Certificate): """ An x509 certificate and private key. """ def __repr__(self) -> str: return Certificate.__repr__(self) + " with " + repr(self.privateKey) def _setPrivateKey(self, privateKey): if not privateKey.matches(self.getPublicKey()): raise VerifyError("Certificate public and private keys do not match.") self.privateKey = privateKey return self def newCertificate(self, newCertData, format=crypto.FILETYPE_ASN1): """ Create a new L{PrivateCertificate} from the given certificate data and this instance's private key. """ return self.load(newCertData, self.privateKey, format) @classmethod def load(Class, data, privateKey, format=crypto.FILETYPE_ASN1): return Class._load(data, format)._setPrivateKey(privateKey) def inspect(self): return "\n".join([Certificate._inspect(self), self.privateKey.inspect()]) def dumpPEM(self): """ Dump both public and private parts of a private certificate to PEM-format data. """ return self.dump(crypto.FILETYPE_PEM) + self.privateKey.dump( crypto.FILETYPE_PEM ) @classmethod def loadPEM(Class, data): """ Load both private and public parts of a private certificate from a chunk of PEM-format data. """ return Class.load( data, KeyPair.load(data, crypto.FILETYPE_PEM), crypto.FILETYPE_PEM ) @classmethod def fromCertificateAndKeyPair(Class, certificateInstance, privateKey): privcert = Class(certificateInstance.original) return privcert._setPrivateKey(privateKey) def options(self, *authorities): """ Create a context factory using this L{PrivateCertificate}'s certificate and private key. @param authorities: A list of L{Certificate} object @return: A context factory. @rtype: L{CertificateOptions <twisted.internet.ssl.CertificateOptions>} """ options = dict(privateKey=self.privateKey.original, certificate=self.original) if authorities: options.update( dict( trustRoot=OpenSSLCertificateAuthorities( [auth.original for auth in authorities] ) ) ) return OpenSSLCertificateOptions(**options) def certificateRequest(self, format=crypto.FILETYPE_ASN1, digestAlgorithm="sha256"): return self.privateKey.certificateRequest( self.getSubject(), format, digestAlgorithm ) def signCertificateRequest( self, requestData, verifyDNCallback, serialNumber, requestFormat=crypto.FILETYPE_ASN1, certificateFormat=crypto.FILETYPE_ASN1, ): issuer = self.getSubject() return self.privateKey.signCertificateRequest( issuer, requestData, verifyDNCallback, serialNumber, requestFormat, certificateFormat, ) def signRequestObject( self, certificateRequest, serialNumber, secondsToExpiry=60 * 60 * 24 * 365, # One year digestAlgorithm="sha256", ): return self.privateKey.signRequestObject( self.getSubject(), certificateRequest, serialNumber, secondsToExpiry, digestAlgorithm, ) class PublicKey: """ A L{PublicKey} is a representation of the public part of a key pair. You can't do a whole lot with it aside from comparing it to other L{PublicKey} objects. @note: If constructing a L{PublicKey} manually, be sure to pass only a L{OpenSSL.crypto.PKey} that does not contain a private key! @ivar original: The original private key. """ def __init__(self, osslpkey): """ @param osslpkey: The underlying pyOpenSSL key object. @type osslpkey: L{OpenSSL.crypto.PKey} """ self.original = osslpkey def matches(self, otherKey): """ Does this L{PublicKey} contain the same value as another L{PublicKey}? @param otherKey: The key to compare C{self} to. @type otherKey: L{PublicKey} @return: L{True} if these keys match, L{False} if not. @rtype: L{bool} """ return self.keyHash() == otherKey.keyHash() def __repr__(self) -> str: return f"<{self.__class__.__name__} {self.keyHash()}>" def keyHash(self): """ Compute a hash of the underlying PKey object. The purpose of this method is to allow you to determine if two certificates share the same public key; it is not really useful for anything else. In versions of Twisted prior to 15.0, C{keyHash} used a technique involving certificate requests for computing the hash that was not stable in the face of changes to the underlying OpenSSL library. @return: Return a 32-character hexadecimal string uniquely identifying this public key, I{for this version of Twisted}. @rtype: native L{str} """ raw = crypto.dump_publickey(crypto.FILETYPE_ASN1, self.original) h = md5() h.update(raw) return h.hexdigest() def inspect(self): return f"Public Key with Hash: {self.keyHash()}" class KeyPair(PublicKey): @classmethod def load(Class, data, format=crypto.FILETYPE_ASN1): return Class(crypto.load_privatekey(format, data)) def dump(self, format=crypto.FILETYPE_ASN1): return crypto.dump_privatekey(format, self.original) @deprecated(Version("Twisted", 15, 0, 0), "a real persistence system") def __getstate__(self): return self.dump() @deprecated(Version("Twisted", 15, 0, 0), "a real persistence system") def __setstate__(self, state): self.__init__(crypto.load_privatekey(crypto.FILETYPE_ASN1, state)) def inspect(self): t = self.original.type() if t == crypto.TYPE_RSA: ts = "RSA" elif t == crypto.TYPE_DSA: ts = "DSA" else: ts = "(Unknown Type!)" L = (self.original.bits(), ts, self.keyHash()) return "%s-bit %s Key Pair with Hash: %s" % L @classmethod def generate(Class, kind=crypto.TYPE_RSA, size=2048): pkey = crypto.PKey() pkey.generate_key(kind, size) return Class(pkey) def newCertificate(self, newCertData, format=crypto.FILETYPE_ASN1): return PrivateCertificate.load(newCertData, self, format) def requestObject(self, distinguishedName, digestAlgorithm="sha256"): req = crypto.X509Req() req.set_pubkey(self.original) distinguishedName._copyInto(req.get_subject()) req.sign(self.original, digestAlgorithm) return CertificateRequest(req) def certificateRequest( self, distinguishedName, format=crypto.FILETYPE_ASN1, digestAlgorithm="sha256" ): """ Create a certificate request signed with this key. @return: a string, formatted according to the 'format' argument. """ return self.requestObject(distinguishedName, digestAlgorithm).dump(format) def signCertificateRequest( self, issuerDistinguishedName, requestData, verifyDNCallback, serialNumber, requestFormat=crypto.FILETYPE_ASN1, certificateFormat=crypto.FILETYPE_ASN1, secondsToExpiry=60 * 60 * 24 * 365, # One year digestAlgorithm="sha256", ): """ Given a blob of certificate request data and a certificate authority's DistinguishedName, return a blob of signed certificate data. If verifyDNCallback returns a Deferred, I will return a Deferred which fires the data when that Deferred has completed. """ hlreq = CertificateRequest.load(requestData, requestFormat) dn = hlreq.getSubject() vval = verifyDNCallback(dn) def verified(value): if not value: raise VerifyError( "DN callback {!r} rejected request DN {!r}".format( verifyDNCallback, dn ) ) return self.signRequestObject( issuerDistinguishedName, hlreq, serialNumber, secondsToExpiry, digestAlgorithm, ).dump(certificateFormat) if isinstance(vval, Deferred): return vval.addCallback(verified) else: return verified(vval) def signRequestObject( self, issuerDistinguishedName, requestObject, serialNumber, secondsToExpiry=60 * 60 * 24 * 365, # One year digestAlgorithm="sha256", ): """ Sign a CertificateRequest instance, returning a Certificate instance. """ req = requestObject.original cert = crypto.X509() issuerDistinguishedName._copyInto(cert.get_issuer()) cert.set_subject(req.get_subject()) cert.set_pubkey(req.get_pubkey()) cert.gmtime_adj_notBefore(0) cert.gmtime_adj_notAfter(secondsToExpiry) cert.set_serial_number(serialNumber) cert.sign(self.original, digestAlgorithm) return Certificate(cert) def selfSignedCert(self, serialNumber, **kw): dn = DN(**kw) return PrivateCertificate.fromCertificateAndKeyPair( self.signRequestObject(dn, self.requestObject(dn), serialNumber), self ) class IOpenSSLTrustRoot(Interface): """ Trust settings for an OpenSSL context. Note that this interface's methods are private, so things outside of Twisted shouldn't implement it. """ def _addCACertsToContext(context): """ Add certificate-authority certificates to an SSL context whose connections should trust those authorities. @param context: An SSL context for a connection which should be verified by some certificate authority. @type context: L{OpenSSL.SSL.Context} @return: L{None} """ @implementer(IOpenSSLTrustRoot) class OpenSSLCertificateAuthorities: """ Trust an explicitly specified set of certificates, represented by a list of L{OpenSSL.crypto.X509} objects. """ def __init__(self, caCerts): """ @param caCerts: The certificate authorities to trust when using this object as a C{trustRoot} for L{OpenSSLCertificateOptions}. @type caCerts: L{list} of L{OpenSSL.crypto.X509} """ self._caCerts = caCerts def _addCACertsToContext(self, context): store = context.get_cert_store() for cert in self._caCerts: store.add_cert(cert) def trustRootFromCertificates(certificates): """ Builds an object that trusts multiple root L{Certificate}s. When passed to L{optionsForClientTLS}, connections using those options will reject any server certificate not signed by at least one of the certificates in the `certificates` list. @since: 16.0 @param certificates: All certificates which will be trusted. @type certificates: C{iterable} of L{CertBase} @rtype: L{IOpenSSLTrustRoot} @return: an object suitable for use as the trustRoot= keyword argument to L{optionsForClientTLS} """ certs = [] for cert in certificates: # PrivateCertificate or Certificate are both okay if isinstance(cert, CertBase): cert = cert.original else: raise TypeError( "certificates items must be twisted.internet.ssl.CertBase" " instances" ) certs.append(cert) return OpenSSLCertificateAuthorities(certs) @implementer(IOpenSSLTrustRoot) class OpenSSLDefaultPaths: """ Trust the set of default verify paths that OpenSSL was built with, as specified by U{SSL_CTX_set_default_verify_paths <https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_load_verify_locations.html>}. """ def _addCACertsToContext(self, context): context.set_default_verify_paths() def platformTrust(): """ Attempt to discover a set of trusted certificate authority certificates (or, in other words: trust roots, or root certificates) whose trust is managed and updated by tools outside of Twisted. If you are writing any client-side TLS code with Twisted, you should use this as the C{trustRoot} argument to L{CertificateOptions <twisted.internet.ssl.CertificateOptions>}. The result of this function should be like the up-to-date list of certificates in a web browser. When developing code that uses C{platformTrust}, you can think of it that way. However, the choice of which certificate authorities to trust is never Twisted's responsibility. Unless you're writing a very unusual application or library, it's not your code's responsibility either. The user may use platform-specific tools for defining which server certificates should be trusted by programs using TLS. The purpose of using this API is to respect that decision as much as possible. This should be a set of trust settings most appropriate for I{client} TLS connections; i.e. those which need to verify a server's authenticity. You should probably use this by default for any client TLS connection that you create. For servers, however, client certificates are typically not verified; or, if they are, their verification will depend on a custom, application-specific certificate authority. @since: 14.0 @note: Currently, L{platformTrust} depends entirely upon your OpenSSL build supporting a set of "L{default verify paths <OpenSSLDefaultPaths>}" which correspond to certificate authority trust roots. Unfortunately, whether this is true of your system is both outside of Twisted's control and difficult (if not impossible) for Twisted to detect automatically. Nevertheless, this ought to work as desired by default on: - Ubuntu Linux machines with the U{ca-certificates <https://launchpad.net/ubuntu/+source/ca-certificates>} package installed, - macOS when using the system-installed version of OpenSSL (i.e. I{not} one installed via MacPorts or Homebrew), - any build of OpenSSL which has had certificate authority certificates installed into its default verify paths (by default, C{/usr/local/ssl/certs} if you've built your own OpenSSL), or - any process where the C{SSL_CERT_FILE} environment variable is set to the path of a file containing your desired CA certificates bundle. Hopefully soon, this API will be updated to use more sophisticated trust-root discovery mechanisms. Until then, you can follow tickets in the Twisted tracker for progress on this implementation on U{Microsoft Windows <https://twistedmatrix.com/trac/ticket/6371>}, U{macOS <https://twistedmatrix.com/trac/ticket/6372>}, and U{a fallback for other platforms which do not have native trust management tools <https://twistedmatrix.com/trac/ticket/6934>}. @return: an appropriate trust settings object for your platform. @rtype: L{IOpenSSLTrustRoot} @raise NotImplementedError: if this platform is not yet supported by Twisted. At present, only OpenSSL is supported. """ return OpenSSLDefaultPaths() def _tolerateErrors(wrapped): """ Wrap up an C{info_callback} for pyOpenSSL so that if something goes wrong the error is immediately logged and the connection is dropped if possible. This wrapper exists because some versions of pyOpenSSL don't handle errors from callbacks at I{all}, and those which do write tracebacks directly to stderr rather than to a supplied logging system. This reports unexpected errors to the Twisted logging system. Also, this terminates the connection immediately if possible because if you've got bugs in your verification logic it's much safer to just give up. @param wrapped: A valid C{info_callback} for pyOpenSSL. @type wrapped: L{callable} @return: A valid C{info_callback} for pyOpenSSL that handles any errors in C{wrapped}. @rtype: L{callable} """ def infoCallback(connection, where, ret): try: return wrapped(connection, where, ret) except BaseException: f = Failure() log.err(f, "Error during info_callback") connection.get_app_data().failVerification(f) return infoCallback @implementer(IOpenSSLClientConnectionCreator) class ClientTLSOptions: """ Client creator for TLS. Private implementation type (not exposed to applications) for public L{optionsForClientTLS} API. @ivar _ctx: The context to use for new connections. @type _ctx: L{OpenSSL.SSL.Context} @ivar _hostname: The hostname to verify, as specified by the application, as some human-readable text. @type _hostname: L{unicode} @ivar _hostnameBytes: The hostname to verify, decoded into IDNA-encoded bytes. This is passed to APIs which think that hostnames are bytes, such as OpenSSL's SNI implementation. @type _hostnameBytes: L{bytes} @ivar _hostnameASCII: The hostname, as transcoded into IDNA ASCII-range unicode code points. This is pre-transcoded because the C{service_identity} package is rather strict about requiring the C{idna} package from PyPI for internationalized domain names, rather than working with Python's built-in (but sometimes broken) IDNA encoding. ASCII values, however, will always work. @type _hostnameASCII: L{unicode} @ivar _hostnameIsDnsName: Whether or not the C{_hostname} is a DNSName. Will be L{False} if C{_hostname} is an IP address or L{True} if C{_hostname} is a DNSName @type _hostnameIsDnsName: L{bool} """ def __init__(self, hostname, ctx): """ Initialize L{ClientTLSOptions}. @param hostname: The hostname to verify as input by a human. @type hostname: L{unicode} @param ctx: an L{OpenSSL.SSL.Context} to use for new connections. @type ctx: L{OpenSSL.SSL.Context}. """ self._ctx = ctx self._hostname = hostname if isIPAddress(hostname) or isIPv6Address(hostname): self._hostnameBytes = hostname.encode("ascii") self._hostnameIsDnsName = False else: self._hostnameBytes = _idnaBytes(hostname) self._hostnameIsDnsName = True self._hostnameASCII = self._hostnameBytes.decode("ascii") ctx.set_info_callback(_tolerateErrors(self._identityVerifyingInfoCallback)) def clientConnectionForTLS(self, tlsProtocol): """ Create a TLS connection for a client. @note: This will call C{set_app_data} on its connection. If you're delegating to this implementation of this method, don't ever call C{set_app_data} or C{set_info_callback} on the returned connection, or you'll break the implementation of various features of this class. @param tlsProtocol: the TLS protocol initiating the connection. @type tlsProtocol: L{twisted.protocols.tls.TLSMemoryBIOProtocol} @return: the configured client connection. @rtype: L{OpenSSL.SSL.Connection} """ context = self._ctx connection = SSL.Connection(context, None) connection.set_app_data(tlsProtocol) return connection def _identityVerifyingInfoCallback(self, connection, where, ret): """ U{info_callback <http://pythonhosted.org/pyOpenSSL/api/ssl.html#OpenSSL.SSL.Context.set_info_callback> } for pyOpenSSL that verifies the hostname in the presented certificate matches the one passed to this L{ClientTLSOptions}. @param connection: the connection which is handshaking. @type connection: L{OpenSSL.SSL.Connection} @param where: flags indicating progress through a TLS handshake. @type where: L{int} @param ret: ignored @type ret: ignored """ # Literal IPv4 and IPv6 addresses are not permitted # as host names according to the RFCs if where & SSL.SSL_CB_HANDSHAKE_START and self._hostnameIsDnsName: connection.set_tlsext_host_name(self._hostnameBytes) elif where & SSL.SSL_CB_HANDSHAKE_DONE: try: if self._hostnameIsDnsName: verifyHostname(connection, self._hostnameASCII) else: verifyIPAddress(connection, self._hostnameASCII) except VerificationError: f = Failure() transport = connection.get_app_data() transport.failVerification(f) def optionsForClientTLS( hostname, trustRoot=None, clientCertificate=None, acceptableProtocols=None, *, extraCertificateOptions=None, ): """ Create a L{client connection creator <IOpenSSLClientConnectionCreator>} for use with APIs such as L{SSL4ClientEndpoint <twisted.internet.endpoints.SSL4ClientEndpoint>}, L{connectSSL <twisted.internet.interfaces.IReactorSSL.connectSSL>}, and L{startTLS <twisted.internet.interfaces.ITLSTransport.startTLS>}. @since: 14.0 @param hostname: The expected name of the remote host. This serves two purposes: first, and most importantly, it verifies that the certificate received from the server correctly identifies the specified hostname. The second purpose is to use the U{Server Name Indication extension <https://en.wikipedia.org/wiki/Server_Name_Indication>} to indicate to the server which certificate should be used. @type hostname: L{unicode} @param trustRoot: Specification of trust requirements of peers. This may be a L{Certificate} or the result of L{platformTrust}. By default it is L{platformTrust} and you probably shouldn't adjust it unless you really know what you're doing. Be aware that clients using this interface I{must} verify the server; you cannot explicitly pass L{None} since that just means to use L{platformTrust}. @type trustRoot: L{IOpenSSLTrustRoot} @param clientCertificate: The certificate and private key that the client will use to authenticate to the server. If unspecified, the client will not authenticate. @type clientCertificate: L{PrivateCertificate} @param acceptableProtocols: The protocols this peer is willing to speak after the TLS negotiation has completed, advertised over both ALPN and NPN. If this argument is specified, and no overlap can be found with the other peer, the connection will fail to be established. If the remote peer does not offer NPN or ALPN, the connection will be established, but no protocol wil be negotiated. Protocols earlier in the list are preferred over those later in the list. @type acceptableProtocols: L{list} of L{bytes} @param extraCertificateOptions: A dictionary of additional keyword arguments to be presented to L{CertificateOptions}. Please avoid using this unless you absolutely need to; any time you need to pass an option here that is a bug in this interface. @type extraCertificateOptions: L{dict} @return: A client connection creator. @rtype: L{IOpenSSLClientConnectionCreator} """ if extraCertificateOptions is None: extraCertificateOptions = {} if trustRoot is None: trustRoot = platformTrust() if not isinstance(hostname, str): raise TypeError( "optionsForClientTLS requires text for host names, not " + hostname.__class__.__name__ ) if clientCertificate: extraCertificateOptions.update( privateKey=clientCertificate.privateKey.original, certificate=clientCertificate.original, ) certificateOptions = OpenSSLCertificateOptions( trustRoot=trustRoot, acceptableProtocols=acceptableProtocols, **extraCertificateOptions, ) return ClientTLSOptions(hostname, certificateOptions.getContext()) @implementer(IOpenSSLContextFactory) class OpenSSLCertificateOptions: """ A L{CertificateOptions <twisted.internet.ssl.CertificateOptions>} specifies the security properties for a client or server TLS connection used with OpenSSL. @ivar _options: Any option flags to set on the L{OpenSSL.SSL.Context} object that will be created. @type _options: L{int} @ivar _cipherString: An OpenSSL-specific cipher string. @type _cipherString: L{unicode} @ivar _defaultMinimumTLSVersion: The default TLS version that will be negotiated. This should be a "safe default", with wide client and server support, vs an optimally secure one that excludes a large number of users. As of late 2016, TLSv1.0 is that safe default. @type _defaultMinimumTLSVersion: L{TLSVersion} constant """ # Factory for creating contexts. Configurable for testability. _contextFactory = SSL.Context _context = None _OP_NO_TLSv1_3 = _tlsDisableFlags[TLSVersion.TLSv1_3] _defaultMinimumTLSVersion = TLSVersion.TLSv1_0 @_mutuallyExclusiveArguments( [ ["trustRoot", "requireCertificate"], ["trustRoot", "verify"], ["trustRoot", "caCerts"], ["method", "insecurelyLowerMinimumTo"], ["method", "raiseMinimumTo"], ["raiseMinimumTo", "insecurelyLowerMinimumTo"], ["method", "lowerMaximumSecurityTo"], ] ) def __init__( self, privateKey=None, certificate=None, method=None, verify=False, caCerts=None, verifyDepth=9, requireCertificate=True, verifyOnce=True, enableSingleUseKeys=True, enableSessions=False, fixBrokenPeers=False, enableSessionTickets=False, extraCertChain=None, acceptableCiphers=None, dhParameters=None, trustRoot=None, acceptableProtocols=None, raiseMinimumTo=None, insecurelyLowerMinimumTo=None, lowerMaximumSecurityTo=None, ): """ Create an OpenSSL context SSL connection context factory. @param privateKey: A PKey object holding the private key. @param certificate: An X509 object holding the certificate. @param method: Deprecated, use a combination of C{insecurelyLowerMinimumTo}, C{raiseMinimumTo}, or C{lowerMaximumSecurityTo} instead. The SSL protocol to use, one of C{SSLv23_METHOD}, C{SSLv2_METHOD}, C{SSLv3_METHOD}, C{TLSv1_METHOD} (or any other method constants provided by pyOpenSSL). By default, a setting will be used which allows TLSv1.0, TLSv1.1, and TLSv1.2. Can not be used with C{insecurelyLowerMinimumTo}, C{raiseMinimumTo}, or C{lowerMaximumSecurityTo} @param verify: Please use a C{trustRoot} keyword argument instead, since it provides the same functionality in a less error-prone way. By default this is L{False}. If L{True}, verify certificates received from the peer and fail the handshake if verification fails. Otherwise, allow anonymous sessions and sessions with certificates which fail validation. @param caCerts: Please use a C{trustRoot} keyword argument instead, since it provides the same functionality in a less error-prone way. List of certificate authority certificate objects to use to verify the peer's certificate. Only used if verify is L{True} and will be ignored otherwise. Since verify is L{False} by default, this is L{None} by default. @type caCerts: L{list} of L{OpenSSL.crypto.X509} @param verifyDepth: Depth in certificate chain down to which to verify. If unspecified, use the underlying default (9). @param requireCertificate: Please use a C{trustRoot} keyword argument instead, since it provides the same functionality in a less error-prone way. If L{True}, do not allow anonymous sessions; defaults to L{True}. @param verifyOnce: If True, do not re-verify the certificate on session resumption. @param enableSingleUseKeys: If L{True}, generate a new key whenever ephemeral DH and ECDH parameters are used to prevent small subgroup attacks and to ensure perfect forward secrecy. @param enableSessions: This allows a shortened handshake to be used when a known client reconnects to the same process. If True, enable OpenSSL's session caching. Note that session caching only works on a single Twisted node at once. Also, it is currently somewhat risky due to U{a crashing bug when using OpenSSL 1.1.1 <https://twistedmatrix.com/trac/ticket/9764>}. @param fixBrokenPeers: If True, enable various non-spec protocol fixes for broken SSL implementations. This should be entirely safe, according to the OpenSSL documentation, but YMMV. This option is now off by default, because it causes problems with connections between peers using OpenSSL 0.9.8a. @param enableSessionTickets: If L{True}, enable session ticket extension for session resumption per RFC 5077. Note there is no support for controlling session tickets. This option is off by default, as some server implementations don't correctly process incoming empty session ticket extensions in the hello. @param extraCertChain: List of certificates that I{complete} your verification chain if the certificate authority that signed your C{certificate} isn't widely supported. Do I{not} add C{certificate} to it. @type extraCertChain: C{list} of L{OpenSSL.crypto.X509} @param acceptableCiphers: Ciphers that are acceptable for connections. Uses a secure default if left L{None}. @type acceptableCiphers: L{IAcceptableCiphers} @param dhParameters: Key generation parameters that are required for Diffie-Hellman key exchange. If this argument is left L{None}, C{EDH} ciphers are I{disabled} regardless of C{acceptableCiphers}. @type dhParameters: L{DiffieHellmanParameters <twisted.internet.ssl.DiffieHellmanParameters>} @param trustRoot: Specification of trust requirements of peers. If this argument is specified, the peer is verified. It requires a certificate, and that certificate must be signed by one of the certificate authorities specified by this object. Note that since this option specifies the same information as C{caCerts}, C{verify}, and C{requireCertificate}, specifying any of those options in combination with this one will raise a L{TypeError}. @type trustRoot: L{IOpenSSLTrustRoot} @param acceptableProtocols: The protocols this peer is willing to speak after the TLS negotiation has completed, advertised over both ALPN and NPN. If this argument is specified, and no overlap can be found with the other peer, the connection will fail to be established. If the remote peer does not offer NPN or ALPN, the connection will be established, but no protocol wil be negotiated. Protocols earlier in the list are preferred over those later in the list. @type acceptableProtocols: L{list} of L{bytes} @param raiseMinimumTo: The minimum TLS version that you want to use, or Twisted's default if it is higher. Use this if you want to make your client/server more secure than Twisted's default, but will accept Twisted's default instead if it moves higher than this value. You probably want to use this over C{insecurelyLowerMinimumTo}. @type raiseMinimumTo: L{TLSVersion} constant @param insecurelyLowerMinimumTo: The minimum TLS version to use, possibly lower than Twisted's default. If not specified, it is a generally considered safe default (TLSv1.0). If you want to raise your minimum TLS version to above that of this default, use C{raiseMinimumTo}. DO NOT use this argument unless you are absolutely sure this is what you want. @type insecurelyLowerMinimumTo: L{TLSVersion} constant @param lowerMaximumSecurityTo: The maximum TLS version to use. If not specified, it is the most recent your OpenSSL supports. You only want to set this if the peer that you are communicating with has problems with more recent TLS versions, it lowers your security when communicating with newer peers. DO NOT use this argument unless you are absolutely sure this is what you want. @type lowerMaximumSecurityTo: L{TLSVersion} constant @raise ValueError: when C{privateKey} or C{certificate} are set without setting the respective other. @raise ValueError: when C{verify} is L{True} but C{caCerts} doesn't specify any CA certificates. @raise ValueError: when C{extraCertChain} is passed without specifying C{privateKey} or C{certificate}. @raise ValueError: when C{acceptableCiphers} doesn't yield any usable ciphers for the current platform. @raise TypeError: if C{trustRoot} is passed in combination with C{caCert}, C{verify}, or C{requireCertificate}. Please prefer C{trustRoot} in new code, as its semantics are less tricky. @raise TypeError: if C{method} is passed in combination with C{tlsProtocols}. Please prefer the more explicit C{tlsProtocols} in new code. @raises NotImplementedError: If acceptableProtocols were provided but no negotiation mechanism is available. """ if (privateKey is None) != (certificate is None): raise ValueError("Specify neither or both of privateKey and certificate") self.privateKey = privateKey self.certificate = certificate # Set basic security options: disallow insecure SSLv2, disallow TLS # compression to avoid CRIME attack, make the server choose the # ciphers. self._options = ( SSL.OP_NO_SSLv2 | SSL.OP_NO_COMPRESSION | SSL.OP_CIPHER_SERVER_PREFERENCE ) # Set the mode to Release Buffers, which demallocs send/recv buffers on # idle TLS connections to save memory self._mode = SSL.MODE_RELEASE_BUFFERS if method is None: self.method = SSL.SSLv23_METHOD if raiseMinimumTo: if lowerMaximumSecurityTo and raiseMinimumTo > lowerMaximumSecurityTo: raise ValueError( "raiseMinimumTo needs to be lower than " "lowerMaximumSecurityTo" ) if raiseMinimumTo > self._defaultMinimumTLSVersion: insecurelyLowerMinimumTo = raiseMinimumTo if insecurelyLowerMinimumTo is None: insecurelyLowerMinimumTo = self._defaultMinimumTLSVersion # If you set the max lower than the default, but don't set the # minimum, pull it down to that if ( lowerMaximumSecurityTo and insecurelyLowerMinimumTo > lowerMaximumSecurityTo ): insecurelyLowerMinimumTo = lowerMaximumSecurityTo if ( lowerMaximumSecurityTo and insecurelyLowerMinimumTo > lowerMaximumSecurityTo ): raise ValueError( "insecurelyLowerMinimumTo needs to be lower than " "lowerMaximumSecurityTo" ) excludedVersions = _getExcludedTLSProtocols( insecurelyLowerMinimumTo, lowerMaximumSecurityTo ) for version in excludedVersions: self._options |= _tlsDisableFlags[version] else: warnings.warn( ( "Passing method to twisted.internet.ssl.CertificateOptions " "was deprecated in Twisted 17.1.0. Please use a combination " "of insecurelyLowerMinimumTo, raiseMinimumTo, and " "lowerMaximumSecurityTo instead, as Twisted will correctly " "configure the method." ), DeprecationWarning, stacklevel=3, ) # Otherwise respect the application decision. self.method = method if verify and not caCerts: raise ValueError( "Specify client CA certificate information if and" " only if enabling certificate verification" ) self.verify = verify if extraCertChain is not None and None in (privateKey, certificate): raise ValueError( "A private key and a certificate are required " "when adding a supplemental certificate chain." ) if extraCertChain is not None: self.extraCertChain = extraCertChain else: self.extraCertChain = [] self.caCerts = caCerts self.verifyDepth = verifyDepth self.requireCertificate = requireCertificate self.verifyOnce = verifyOnce self.enableSingleUseKeys = enableSingleUseKeys if enableSingleUseKeys: self._options |= SSL.OP_SINGLE_DH_USE | SSL.OP_SINGLE_ECDH_USE self.enableSessions = enableSessions self.fixBrokenPeers = fixBrokenPeers if fixBrokenPeers: self._options |= SSL.OP_ALL self.enableSessionTickets = enableSessionTickets if not enableSessionTickets: self._options |= SSL.OP_NO_TICKET self.dhParameters = dhParameters self._ecChooser = _ChooseDiffieHellmanEllipticCurve( SSL.OPENSSL_VERSION_NUMBER, openSSLlib=pyOpenSSLlib, openSSLcrypto=crypto, ) if acceptableCiphers is None: acceptableCiphers = defaultCiphers # This needs to run when method and _options are finalized. self._cipherString = ":".join( c.fullName for c in acceptableCiphers.selectCiphers( _expandCipherString("ALL", self.method, self._options) ) ) if self._cipherString == "": raise ValueError( "Supplied IAcceptableCiphers yielded no usable ciphers " "on this platform." ) if trustRoot is None: if self.verify: trustRoot = OpenSSLCertificateAuthorities(caCerts) else: self.verify = True self.requireCertificate = True trustRoot = IOpenSSLTrustRoot(trustRoot) self.trustRoot = trustRoot if acceptableProtocols is not None and not protocolNegotiationMechanisms(): raise NotImplementedError( "No support for protocol negotiation on this platform." ) self._acceptableProtocols = acceptableProtocols def __getstate__(self): d = self.__dict__.copy() try: del d["_context"] except KeyError: pass return d def __setstate__(self, state): self.__dict__ = state def getContext(self): """ Return an L{OpenSSL.SSL.Context} object. """ if self._context is None: self._context = self._makeContext() return self._context def _makeContext(self): ctx = self._contextFactory(self.method) ctx.set_options(self._options) ctx.set_mode(self._mode) if self.certificate is not None and self.privateKey is not None: ctx.use_certificate(self.certificate) ctx.use_privatekey(self.privateKey) for extraCert in self.extraCertChain: ctx.add_extra_chain_cert(extraCert) # Sanity check ctx.check_privatekey() verifyFlags = SSL.VERIFY_NONE if self.verify: verifyFlags = SSL.VERIFY_PEER if self.requireCertificate: verifyFlags |= SSL.VERIFY_FAIL_IF_NO_PEER_CERT if self.verifyOnce: verifyFlags |= SSL.VERIFY_CLIENT_ONCE self.trustRoot._addCACertsToContext(ctx) # It'd be nice if pyOpenSSL let us pass None here for this behavior (as # the underlying OpenSSL API call allows NULL to be passed). It # doesn't, so we'll supply a function which does the same thing. def _verifyCallback(conn, cert, errno, depth, preverify_ok): return preverify_ok ctx.set_verify(verifyFlags, _verifyCallback) if self.verifyDepth is not None: ctx.set_verify_depth(self.verifyDepth) # Until we know what's going on with # https://twistedmatrix.com/trac/ticket/9764 let's be conservative # in naming this; ASCII-only, short, as the recommended value (a # hostname) might be: sessionIDContext = hexlify(secureRandom(7)) # Note that this doesn't actually set the session ID (which had # better be per-connection anyway!): # https://github.com/pyca/pyopenssl/issues/845 # This is set unconditionally because it's apparently required for # client certificates to work: # https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set_session_id_context.html ctx.set_session_id(sessionIDContext) if self.enableSessions: ctx.set_session_cache_mode(SSL.SESS_CACHE_SERVER) else: ctx.set_session_cache_mode(SSL.SESS_CACHE_OFF) if self.dhParameters: ctx.load_tmp_dh(self.dhParameters._dhFile.path) ctx.set_cipher_list(self._cipherString.encode("ascii")) self._ecChooser.configureECDHCurve(ctx) if self._acceptableProtocols: # Try to set NPN and ALPN. _acceptableProtocols cannot be set by # the constructor unless at least one mechanism is supported. _setAcceptableProtocols(ctx, self._acceptableProtocols) return ctx OpenSSLCertificateOptions.__getstate__ = deprecated( Version("Twisted", 15, 0, 0), "a real persistence system" )(OpenSSLCertificateOptions.__getstate__) OpenSSLCertificateOptions.__setstate__ = deprecated( Version("Twisted", 15, 0, 0), "a real persistence system" )(OpenSSLCertificateOptions.__setstate__) @implementer(ICipher) @attr.s(frozen=True, auto_attribs=True) class OpenSSLCipher: """ A representation of an OpenSSL cipher. @ivar fullName: The full name of the cipher. For example C{u"ECDHE-RSA-AES256-GCM-SHA384"}. @type fullName: L{unicode} """ fullName: str @lru_cache(maxsize=32) def _expandCipherString(cipherString, method, options): """ Expand C{cipherString} according to C{method} and C{options} to a tuple of explicit ciphers that are supported by the current platform. @param cipherString: An OpenSSL cipher string to expand. @type cipherString: L{unicode} @param method: An OpenSSL method like C{SSL.TLSv1_METHOD} used for determining the effective ciphers. @param options: OpenSSL options like C{SSL.OP_NO_SSLv3} ORed together. @type options: L{int} @return: The effective list of explicit ciphers that results from the arguments on the current platform. @rtype: L{tuple} of L{ICipher} """ ctx = SSL.Context(method) ctx.set_options(options) try: ctx.set_cipher_list(cipherString.encode("ascii")) except SSL.Error as e: # OpenSSL 1.1.1 turns an invalid cipher list into TLS 1.3 # ciphers, so pyOpenSSL >= 19.0.0 raises an artificial Error # that lacks a corresponding OpenSSL error if the cipher list # consists only of these after a call to set_cipher_list. if not e.args[0]: return tuple() if e.args[0][0][2] == "no cipher match": return tuple() else: raise conn = SSL.Connection(ctx, None) ciphers = conn.get_cipher_list() if isinstance(ciphers[0], str): return tuple(OpenSSLCipher(cipher) for cipher in ciphers) else: return tuple(OpenSSLCipher(cipher.decode("ascii")) for cipher in ciphers) @lru_cache(maxsize=128) def _selectCiphers(wantedCiphers, availableCiphers): """ Caclulate the acceptable list of ciphers from the ciphers we want and the ciphers we have support for. @param wantedCiphers: The ciphers we want to use. @type wantedCiphers: L{tuple} of L{OpenSSLCipher} @param availableCiphers: The ciphers we have available to use. @type availableCiphers: L{tuple} of L{OpenSSLCipher} @rtype: L{tuple} of L{OpenSSLCipher} """ return tuple(cipher for cipher in wantedCiphers if cipher in availableCiphers) @implementer(IAcceptableCiphers) class OpenSSLAcceptableCiphers: """ A representation of ciphers that are acceptable for TLS connections. """ def __init__(self, ciphers): self._ciphers = tuple(ciphers) def selectCiphers(self, availableCiphers): return _selectCiphers(self._ciphers, tuple(availableCiphers)) @classmethod def fromOpenSSLCipherString(cls, cipherString): """ Create a new instance using an OpenSSL cipher string. @param cipherString: An OpenSSL cipher string that describes what cipher suites are acceptable. See the documentation of U{OpenSSL <http://www.openssl.org/docs/apps/ciphers.html#CIPHER_STRINGS>} or U{Apache <http://httpd.apache.org/docs/2.4/mod/mod_ssl.html#sslciphersuite>} for details. @type cipherString: L{unicode} @return: Instance representing C{cipherString}. @rtype: L{twisted.internet.ssl.AcceptableCiphers} """ return cls( _expandCipherString( nativeString(cipherString), SSL.SSLv23_METHOD, SSL.OP_NO_SSLv2 | SSL.OP_NO_SSLv3, ) ) # 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 and ChaCha20 over any AES-CBC for better performance and # security, # - prefer AES-GCM to ChaCha20 because AES hardware support is common, # - disable NULL authentication, MD5 MACs and DSS for security reasons. # defaultCiphers = OpenSSLAcceptableCiphers.fromOpenSSLCipherString( "TLS13-AES-256-GCM-SHA384:TLS13-CHACHA20-POLY1305-SHA256:" "TLS13-AES-128-GCM-SHA256:" "ECDH+AESGCM:ECDH+CHACHA20:DH+AESGCM:DH+CHACHA20:ECDH+AES256:DH+AES256:" "ECDH+AES128:DH+AES:RSA+AESGCM:RSA+AES:" "!aNULL:!MD5:!DSS" ) _defaultCurveName = "prime256v1" class _ChooseDiffieHellmanEllipticCurve: """ Chooses the best elliptic curve for Elliptic Curve Diffie-Hellman key exchange, and provides a C{configureECDHCurve} method to set the curve, when appropriate, on a new L{OpenSSL.SSL.Context}. The C{configureECDHCurve} method will be set to one of the following based on the provided OpenSSL version and configuration: - L{_configureOpenSSL110} - L{_configureOpenSSL102} - L{_configureOpenSSL101} - L{_configureOpenSSL101NoCurves}. @param openSSLVersion: The OpenSSL version number. @type openSSLVersion: L{int} @see: L{OpenSSL.SSL.OPENSSL_VERSION_NUMBER} @param openSSLlib: The OpenSSL C{cffi} library module. @param openSSLcrypto: The OpenSSL L{crypto} module. @see: L{crypto} """ def __init__(self, openSSLVersion, openSSLlib, openSSLcrypto): self._openSSLlib = openSSLlib self._openSSLcrypto = openSSLcrypto if openSSLVersion >= 0x10100000: self.configureECDHCurve = self._configureOpenSSL110 elif openSSLVersion >= 0x10002000: self.configureECDHCurve = self._configureOpenSSL102 else: try: self._ecCurve = openSSLcrypto.get_elliptic_curve(_defaultCurveName) except ValueError: # The get_elliptic_curve method raises a ValueError # when the curve does not exist. self.configureECDHCurve = self._configureOpenSSL101NoCurves else: self.configureECDHCurve = self._configureOpenSSL101 def _configureOpenSSL110(self, ctx): """ OpenSSL 1.1.0 Contexts are preconfigured with an optimal set of ECDH curves. This method does nothing. @param ctx: L{OpenSSL.SSL.Context} """ def _configureOpenSSL102(self, ctx): """ Have the context automatically choose elliptic curves for ECDH. Run on OpenSSL 1.0.2 and OpenSSL 1.1.0+, but only has an effect on OpenSSL 1.0.2. @param ctx: The context which . @type ctx: L{OpenSSL.SSL.Context} """ ctxPtr = ctx._context try: self._openSSLlib.SSL_CTX_set_ecdh_auto(ctxPtr, True) except BaseException: pass def _configureOpenSSL101(self, ctx): """ Set the default elliptic curve for ECDH on the context. Only run on OpenSSL 1.0.1. @param ctx: The context on which to set the ECDH curve. @type ctx: L{OpenSSL.SSL.Context} """ try: ctx.set_tmp_ecdh(self._ecCurve) except BaseException: pass def _configureOpenSSL101NoCurves(self, ctx): """ No elliptic curves are available on OpenSSL 1.0.1. We can't set anything, so do nothing. @param ctx: The context on which to set the ECDH curve. @type ctx: L{OpenSSL.SSL.Context} """ class OpenSSLDiffieHellmanParameters: """ A representation of key generation parameters that are required for Diffie-Hellman key exchange. """ def __init__(self, parameters): self._dhFile = parameters @classmethod def fromFile(cls, filePath): """ Load parameters from a file. Such a file can be generated using the C{openssl} command line tool as following: C{openssl dhparam -out dh_param_2048.pem -2 2048} Please refer to U{OpenSSL's C{dhparam} documentation <http://www.openssl.org/docs/apps/dhparam.html>} for further details. @param filePath: A file containing parameters for Diffie-Hellman key exchange. @type filePath: L{FilePath <twisted.python.filepath.FilePath>} @return: An instance that loads its parameters from C{filePath}. @rtype: L{DiffieHellmanParameters <twisted.internet.ssl.DiffieHellmanParameters>} """ return cls(filePath) def _setAcceptableProtocols(context, acceptableProtocols): """ Called to set up the L{OpenSSL.SSL.Context} for doing NPN and/or ALPN negotiation. @param context: The context which is set up. @type context: L{OpenSSL.SSL.Context} @param acceptableProtocols: The protocols this peer is willing to speak after the TLS negotiation has completed, advertised over both ALPN and NPN. If this argument is specified, and no overlap can be found with the other peer, the connection will fail to be established. If the remote peer does not offer NPN or ALPN, the connection will be established, but no protocol wil be negotiated. Protocols earlier in the list are preferred over those later in the list. @type acceptableProtocols: L{list} of L{bytes} """ def protoSelectCallback(conn, protocols): """ NPN client-side and ALPN server-side callback used to select the next protocol. Prefers protocols found earlier in C{_acceptableProtocols}. @param conn: The context which is set up. @type conn: L{OpenSSL.SSL.Connection} @param conn: Protocols advertised by the other side. @type conn: L{list} of L{bytes} """ overlap = set(protocols) & set(acceptableProtocols) for p in acceptableProtocols: if p in overlap: return p else: return b"" # If we don't actually have protocols to negotiate, don't set anything up. # Depending on OpenSSL version, failing some of the selection callbacks can # cause the handshake to fail, which is presumably not what was intended # here. if not acceptableProtocols: return supported = protocolNegotiationMechanisms() if supported & ProtocolNegotiationSupport.NPN: def npnAdvertiseCallback(conn): return acceptableProtocols context.set_npn_advertise_callback(npnAdvertiseCallback) context.set_npn_select_callback(protoSelectCallback) if supported & ProtocolNegotiationSupport.ALPN: context.set_alpn_select_callback(protoSelectCallback) context.set_alpn_protos(acceptableProtocols)