Use persistent connections

10 files changed, 2831 insertions, 0 deletions

diff --git a/python/urllib3/contrib/__init__.py b/python/urllib3/contrib/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/python/urllib3/contrib/__init__.py
diff --git a/python/urllib3/contrib/_appengine_environ.py b/python/urllib3/contrib/_appengine_environ.py
new file mode 100644
index 0000000..f3e0094
--- /dev/null
+++ b/python/urllib3/contrib/_appengine_environ.py
@@ -0,0 +1,30 @@
+"""
+This module provides means to detect the App Engine environment.
+"""
+
+import os
+
+
+def is_appengine():
+    return (is_local_appengine() or
+            is_prod_appengine() or
+            is_prod_appengine_mvms())
+
+
+def is_appengine_sandbox():
+    return is_appengine() and not is_prod_appengine_mvms()
+
+
+def is_local_appengine():
+    return ('APPENGINE_RUNTIME' in os.environ and
+            'Development/' in os.environ['SERVER_SOFTWARE'])
+
+
+def is_prod_appengine():
+    return ('APPENGINE_RUNTIME' in os.environ and
+            'Google App Engine/' in os.environ['SERVER_SOFTWARE'] and
+            not is_prod_appengine_mvms())
+
+
+def is_prod_appengine_mvms():
+    return os.environ.get('GAE_VM', False) == 'true'
diff --git a/python/urllib3/contrib/_securetransport/__init__.py b/python/urllib3/contrib/_securetransport/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/python/urllib3/contrib/_securetransport/__init__.py
diff --git a/python/urllib3/contrib/_securetransport/bindings.py b/python/urllib3/contrib/_securetransport/bindings.py
new file mode 100644
index 0000000..bcf41c0
--- /dev/null
+++ b/python/urllib3/contrib/_securetransport/bindings.py
@@ -0,0 +1,593 @@
+"""
+This module uses ctypes to bind a whole bunch of functions and constants from
+SecureTransport. The goal here is to provide the low-level API to
+SecureTransport. These are essentially the C-level functions and constants, and
+they're pretty gross to work with.
+
+This code is a bastardised version of the code found in Will Bond's oscrypto
+library. An enormous debt is owed to him for blazing this trail for us. For
+that reason, this code should be considered to be covered both by urllib3's
+license and by oscrypto's:
+
+    Copyright (c) 2015-2016 Will Bond <will@wbond.net>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+"""
+from __future__ import absolute_import
+
+import platform
+from ctypes.util import find_library
+from ctypes import (
+    c_void_p, c_int32, c_char_p, c_size_t, c_byte, c_uint32, c_ulong, c_long,
+    c_bool
+)
+from ctypes import CDLL, POINTER, CFUNCTYPE
+
+
+security_path = find_library('Security')
+if not security_path:
+    raise ImportError('The library Security could not be found')
+
+
+core_foundation_path = find_library('CoreFoundation')
+if not core_foundation_path:
+    raise ImportError('The library CoreFoundation could not be found')
+
+
+version = platform.mac_ver()[0]
+version_info = tuple(map(int, version.split('.')))
+if version_info < (10, 8):
+    raise OSError(
+        'Only OS X 10.8 and newer are supported, not %s.%s' % (
+            version_info[0], version_info[1]
+        )
+    )
+
+Security = CDLL(security_path, use_errno=True)
+CoreFoundation = CDLL(core_foundation_path, use_errno=True)
+
+Boolean = c_bool
+CFIndex = c_long
+CFStringEncoding = c_uint32
+CFData = c_void_p
+CFString = c_void_p
+CFArray = c_void_p
+CFMutableArray = c_void_p
+CFDictionary = c_void_p
+CFError = c_void_p
+CFType = c_void_p
+CFTypeID = c_ulong
+
+CFTypeRef = POINTER(CFType)
+CFAllocatorRef = c_void_p
+
+OSStatus = c_int32
+
+CFDataRef = POINTER(CFData)
+CFStringRef = POINTER(CFString)
+CFArrayRef = POINTER(CFArray)
+CFMutableArrayRef = POINTER(CFMutableArray)
+CFDictionaryRef = POINTER(CFDictionary)
+CFArrayCallBacks = c_void_p
+CFDictionaryKeyCallBacks = c_void_p
+CFDictionaryValueCallBacks = c_void_p
+
+SecCertificateRef = POINTER(c_void_p)
+SecExternalFormat = c_uint32
+SecExternalItemType = c_uint32
+SecIdentityRef = POINTER(c_void_p)
+SecItemImportExportFlags = c_uint32
+SecItemImportExportKeyParameters = c_void_p
+SecKeychainRef = POINTER(c_void_p)
+SSLProtocol = c_uint32
+SSLCipherSuite = c_uint32
+SSLContextRef = POINTER(c_void_p)
+SecTrustRef = POINTER(c_void_p)
+SSLConnectionRef = c_uint32
+SecTrustResultType = c_uint32
+SecTrustOptionFlags = c_uint32
+SSLProtocolSide = c_uint32
+SSLConnectionType = c_uint32
+SSLSessionOption = c_uint32
+
+
+try:
+    Security.SecItemImport.argtypes = [
+        CFDataRef,
+        CFStringRef,
+        POINTER(SecExternalFormat),
+        POINTER(SecExternalItemType),
+        SecItemImportExportFlags,
+        POINTER(SecItemImportExportKeyParameters),
+        SecKeychainRef,
+        POINTER(CFArrayRef),
+    ]
+    Security.SecItemImport.restype = OSStatus
+
+    Security.SecCertificateGetTypeID.argtypes = []
+    Security.SecCertificateGetTypeID.restype = CFTypeID
+
+    Security.SecIdentityGetTypeID.argtypes = []
+    Security.SecIdentityGetTypeID.restype = CFTypeID
+
+    Security.SecKeyGetTypeID.argtypes = []
+    Security.SecKeyGetTypeID.restype = CFTypeID
+
+    Security.SecCertificateCreateWithData.argtypes = [
+        CFAllocatorRef,
+        CFDataRef
+    ]
+    Security.SecCertificateCreateWithData.restype = SecCertificateRef
+
+    Security.SecCertificateCopyData.argtypes = [
+        SecCertificateRef
+    ]
+    Security.SecCertificateCopyData.restype = CFDataRef
+
+    Security.SecCopyErrorMessageString.argtypes = [
+        OSStatus,
+        c_void_p
+    ]
+    Security.SecCopyErrorMessageString.restype = CFStringRef
+
+    Security.SecIdentityCreateWithCertificate.argtypes = [
+        CFTypeRef,
+        SecCertificateRef,
+        POINTER(SecIdentityRef)
+    ]
+    Security.SecIdentityCreateWithCertificate.restype = OSStatus
+
+    Security.SecKeychainCreate.argtypes = [
+        c_char_p,
+        c_uint32,
+        c_void_p,
+        Boolean,
+        c_void_p,
+        POINTER(SecKeychainRef)
+    ]
+    Security.SecKeychainCreate.restype = OSStatus
+
+    Security.SecKeychainDelete.argtypes = [
+        SecKeychainRef
+    ]
+    Security.SecKeychainDelete.restype = OSStatus
+
+    Security.SecPKCS12Import.argtypes = [
+        CFDataRef,
+        CFDictionaryRef,
+        POINTER(CFArrayRef)
+    ]
+    Security.SecPKCS12Import.restype = OSStatus
+
+    SSLReadFunc = CFUNCTYPE(OSStatus, SSLConnectionRef, c_void_p, POINTER(c_size_t))
+    SSLWriteFunc = CFUNCTYPE(OSStatus, SSLConnectionRef, POINTER(c_byte), POINTER(c_size_t))
+
+    Security.SSLSetIOFuncs.argtypes = [
+        SSLContextRef,
+        SSLReadFunc,
+        SSLWriteFunc
+    ]
+    Security.SSLSetIOFuncs.restype = OSStatus
+
+    Security.SSLSetPeerID.argtypes = [
+        SSLContextRef,
+        c_char_p,
+        c_size_t
+    ]
+    Security.SSLSetPeerID.restype = OSStatus
+
+    Security.SSLSetCertificate.argtypes = [
+        SSLContextRef,
+        CFArrayRef
+    ]
+    Security.SSLSetCertificate.restype = OSStatus
+
+    Security.SSLSetCertificateAuthorities.argtypes = [
+        SSLContextRef,
+        CFTypeRef,
+        Boolean
+    ]
+    Security.SSLSetCertificateAuthorities.restype = OSStatus
+
+    Security.SSLSetConnection.argtypes = [
+        SSLContextRef,
+        SSLConnectionRef
+    ]
+    Security.SSLSetConnection.restype = OSStatus
+
+    Security.SSLSetPeerDomainName.argtypes = [
+        SSLContextRef,
+        c_char_p,
+        c_size_t
+    ]
+    Security.SSLSetPeerDomainName.restype = OSStatus
+
+    Security.SSLHandshake.argtypes = [
+        SSLContextRef
+    ]
+    Security.SSLHandshake.restype = OSStatus
+
+    Security.SSLRead.argtypes = [
+        SSLContextRef,
+        c_char_p,
+        c_size_t,
+        POINTER(c_size_t)
+    ]
+    Security.SSLRead.restype = OSStatus
+
+    Security.SSLWrite.argtypes = [
+        SSLContextRef,
+        c_char_p,
+        c_size_t,
+        POINTER(c_size_t)
+    ]
+    Security.SSLWrite.restype = OSStatus
+
+    Security.SSLClose.argtypes = [
+        SSLContextRef
+    ]
+    Security.SSLClose.restype = OSStatus
+
+    Security.SSLGetNumberSupportedCiphers.argtypes = [
+        SSLContextRef,
+        POINTER(c_size_t)
+    ]
+    Security.SSLGetNumberSupportedCiphers.restype = OSStatus
+
+    Security.SSLGetSupportedCiphers.argtypes = [
+        SSLContextRef,
+        POINTER(SSLCipherSuite),
+        POINTER(c_size_t)
+    ]
+    Security.SSLGetSupportedCiphers.restype = OSStatus
+
+    Security.SSLSetEnabledCiphers.argtypes = [
+        SSLContextRef,
+        POINTER(SSLCipherSuite),
+        c_size_t
+    ]
+    Security.SSLSetEnabledCiphers.restype = OSStatus
+
+    Security.SSLGetNumberEnabledCiphers.argtype = [
+        SSLContextRef,
+        POINTER(c_size_t)
+    ]
+    Security.SSLGetNumberEnabledCiphers.restype = OSStatus
+
+    Security.SSLGetEnabledCiphers.argtypes = [
+        SSLContextRef,
+        POINTER(SSLCipherSuite),
+        POINTER(c_size_t)
+    ]
+    Security.SSLGetEnabledCiphers.restype = OSStatus
+
+    Security.SSLGetNegotiatedCipher.argtypes = [
+        SSLContextRef,
+        POINTER(SSLCipherSuite)
+    ]
+    Security.SSLGetNegotiatedCipher.restype = OSStatus
+
+    Security.SSLGetNegotiatedProtocolVersion.argtypes = [
+        SSLContextRef,
+        POINTER(SSLProtocol)
+    ]
+    Security.SSLGetNegotiatedProtocolVersion.restype = OSStatus
+
+    Security.SSLCopyPeerTrust.argtypes = [
+        SSLContextRef,
+        POINTER(SecTrustRef)
+    ]
+    Security.SSLCopyPeerTrust.restype = OSStatus
+
+    Security.SecTrustSetAnchorCertificates.argtypes = [
+        SecTrustRef,
+        CFArrayRef
+    ]
+    Security.SecTrustSetAnchorCertificates.restype = OSStatus
+
+    Security.SecTrustSetAnchorCertificatesOnly.argstypes = [
+        SecTrustRef,
+        Boolean
+    ]
+    Security.SecTrustSetAnchorCertificatesOnly.restype = OSStatus
+
+    Security.SecTrustEvaluate.argtypes = [
+        SecTrustRef,
+        POINTER(SecTrustResultType)
+    ]
+    Security.SecTrustEvaluate.restype = OSStatus
+
+    Security.SecTrustGetCertificateCount.argtypes = [
+        SecTrustRef
+    ]
+    Security.SecTrustGetCertificateCount.restype = CFIndex
+
+    Security.SecTrustGetCertificateAtIndex.argtypes = [
+        SecTrustRef,
+        CFIndex
+    ]
+    Security.SecTrustGetCertificateAtIndex.restype = SecCertificateRef
+
+    Security.SSLCreateContext.argtypes = [
+        CFAllocatorRef,
+        SSLProtocolSide,
+        SSLConnectionType
+    ]
+    Security.SSLCreateContext.restype = SSLContextRef
+
+    Security.SSLSetSessionOption.argtypes = [
+        SSLContextRef,
+        SSLSessionOption,
+        Boolean
+    ]
+    Security.SSLSetSessionOption.restype = OSStatus
+
+    Security.SSLSetProtocolVersionMin.argtypes = [
+        SSLContextRef,
+        SSLProtocol
+    ]
+    Security.SSLSetProtocolVersionMin.restype = OSStatus
+
+    Security.SSLSetProtocolVersionMax.argtypes = [
+        SSLContextRef,
+        SSLProtocol
+    ]
+    Security.SSLSetProtocolVersionMax.restype = OSStatus
+
+    Security.SecCopyErrorMessageString.argtypes = [
+        OSStatus,
+        c_void_p
+    ]
+    Security.SecCopyErrorMessageString.restype = CFStringRef
+
+    Security.SSLReadFunc = SSLReadFunc
+    Security.SSLWriteFunc = SSLWriteFunc
+    Security.SSLContextRef = SSLContextRef
+    Security.SSLProtocol = SSLProtocol
+    Security.SSLCipherSuite = SSLCipherSuite
+    Security.SecIdentityRef = SecIdentityRef
+    Security.SecKeychainRef = SecKeychainRef
+    Security.SecTrustRef = SecTrustRef
+    Security.SecTrustResultType = SecTrustResultType
+    Security.SecExternalFormat = SecExternalFormat
+    Security.OSStatus = OSStatus
+
+    Security.kSecImportExportPassphrase = CFStringRef.in_dll(
+        Security, 'kSecImportExportPassphrase'
+    )
+    Security.kSecImportItemIdentity = CFStringRef.in_dll(
+        Security, 'kSecImportItemIdentity'
+    )
+
+    # CoreFoundation time!
+    CoreFoundation.CFRetain.argtypes = [
+        CFTypeRef
+    ]
+    CoreFoundation.CFRetain.restype = CFTypeRef
+
+    CoreFoundation.CFRelease.argtypes = [
+        CFTypeRef
+    ]
+    CoreFoundation.CFRelease.restype = None
+
+    CoreFoundation.CFGetTypeID.argtypes = [
+        CFTypeRef
+    ]
+    CoreFoundation.CFGetTypeID.restype = CFTypeID
+
+    CoreFoundation.CFStringCreateWithCString.argtypes = [
+        CFAllocatorRef,
+        c_char_p,
+        CFStringEncoding
+    ]
+    CoreFoundation.CFStringCreateWithCString.restype = CFStringRef
+
+    CoreFoundation.CFStringGetCStringPtr.argtypes = [
+        CFStringRef,
+        CFStringEncoding
+    ]
+    CoreFoundation.CFStringGetCStringPtr.restype = c_char_p
+
+    CoreFoundation.CFStringGetCString.argtypes = [
+        CFStringRef,
+        c_char_p,
+        CFIndex,
+        CFStringEncoding
+    ]
+    CoreFoundation.CFStringGetCString.restype = c_bool
+
+    CoreFoundation.CFDataCreate.argtypes = [
+        CFAllocatorRef,
+        c_char_p,
+        CFIndex
+    ]
+    CoreFoundation.CFDataCreate.restype = CFDataRef
+
+    CoreFoundation.CFDataGetLength.argtypes = [
+        CFDataRef
+    ]
+    CoreFoundation.CFDataGetLength.restype = CFIndex
+
+    CoreFoundation.CFDataGetBytePtr.argtypes = [
+        CFDataRef
+    ]
+    CoreFoundation.CFDataGetBytePtr.restype = c_void_p
+
+    CoreFoundation.CFDictionaryCreate.argtypes = [
+        CFAllocatorRef,
+        POINTER(CFTypeRef),
+        POINTER(CFTypeRef),
+        CFIndex,
+        CFDictionaryKeyCallBacks,
+        CFDictionaryValueCallBacks
+    ]
+    CoreFoundation.CFDictionaryCreate.restype = CFDictionaryRef
+
+    CoreFoundation.CFDictionaryGetValue.argtypes = [
+        CFDictionaryRef,
+        CFTypeRef
+    ]
+    CoreFoundation.CFDictionaryGetValue.restype = CFTypeRef
+
+    CoreFoundation.CFArrayCreate.argtypes = [
+        CFAllocatorRef,
+        POINTER(CFTypeRef),
+        CFIndex,
+        CFArrayCallBacks,
+    ]
+    CoreFoundation.CFArrayCreate.restype = CFArrayRef
+
+    CoreFoundation.CFArrayCreateMutable.argtypes = [
+        CFAllocatorRef,
+        CFIndex,
+        CFArrayCallBacks
+    ]
+    CoreFoundation.CFArrayCreateMutable.restype = CFMutableArrayRef
+
+    CoreFoundation.CFArrayAppendValue.argtypes = [
+        CFMutableArrayRef,
+        c_void_p
+    ]
+    CoreFoundation.CFArrayAppendValue.restype = None
+
+    CoreFoundation.CFArrayGetCount.argtypes = [
+        CFArrayRef
+    ]
+    CoreFoundation.CFArrayGetCount.restype = CFIndex
+
+    CoreFoundation.CFArrayGetValueAtIndex.argtypes = [
+        CFArrayRef,
+        CFIndex
+    ]
+    CoreFoundation.CFArrayGetValueAtIndex.restype = c_void_p
+
+    CoreFoundation.kCFAllocatorDefault = CFAllocatorRef.in_dll(
+        CoreFoundation, 'kCFAllocatorDefault'
+    )
+    CoreFoundation.kCFTypeArrayCallBacks = c_void_p.in_dll(CoreFoundation, 'kCFTypeArrayCallBacks')
+    CoreFoundation.kCFTypeDictionaryKeyCallBacks = c_void_p.in_dll(
+        CoreFoundation, 'kCFTypeDictionaryKeyCallBacks'
+    )
+    CoreFoundation.kCFTypeDictionaryValueCallBacks = c_void_p.in_dll(
+        CoreFoundation, 'kCFTypeDictionaryValueCallBacks'
+    )
+
+    CoreFoundation.CFTypeRef = CFTypeRef
+    CoreFoundation.CFArrayRef = CFArrayRef
+    CoreFoundation.CFStringRef = CFStringRef
+    CoreFoundation.CFDictionaryRef = CFDictionaryRef
+
+except (AttributeError):
+    raise ImportError('Error initializing ctypes')
+
+
+class CFConst(object):
+    """
+    A class object that acts as essentially a namespace for CoreFoundation
+    constants.
+    """
+    kCFStringEncodingUTF8 = CFStringEncoding(0x08000100)
+
+
+class SecurityConst(object):
+    """
+    A class object that acts as essentially a namespace for Security constants.
+    """
+    kSSLSessionOptionBreakOnServerAuth = 0
+
+    kSSLProtocol2 = 1
+    kSSLProtocol3 = 2
+    kTLSProtocol1 = 4
+    kTLSProtocol11 = 7
+    kTLSProtocol12 = 8
+
+    kSSLClientSide = 1
+    kSSLStreamType = 0
+
+    kSecFormatPEMSequence = 10
+
+    kSecTrustResultInvalid = 0
+    kSecTrustResultProceed = 1
+    # This gap is present on purpose: this was kSecTrustResultConfirm, which
+    # is deprecated.
+    kSecTrustResultDeny = 3
+    kSecTrustResultUnspecified = 4
+    kSecTrustResultRecoverableTrustFailure = 5
+    kSecTrustResultFatalTrustFailure = 6
+    kSecTrustResultOtherError = 7
+
+    errSSLProtocol = -9800
+    errSSLWouldBlock = -9803
+    errSSLClosedGraceful = -9805
+    errSSLClosedNoNotify = -9816
+    errSSLClosedAbort = -9806
+
+    errSSLXCertChainInvalid = -9807
+    errSSLCrypto = -9809
+    errSSLInternal = -9810
+    errSSLCertExpired = -9814
+    errSSLCertNotYetValid = -9815
+    errSSLUnknownRootCert = -9812
+    errSSLNoRootCert = -9813
+    errSSLHostNameMismatch = -9843
+    errSSLPeerHandshakeFail = -9824
+    errSSLPeerUserCancelled = -9839
+    errSSLWeakPeerEphemeralDHKey = -9850
+    errSSLServerAuthCompleted = -9841
+    errSSLRecordOverflow = -9847
+
+    errSecVerifyFailed = -67808
+    errSecNoTrustSettings = -25263
+    errSecItemNotFound = -25300
+    errSecInvalidTrustSettings = -25262
+
+    # Cipher suites. We only pick the ones our default cipher string allows.
+    TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 = 0xC02C
+    TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 = 0xC030
+    TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 = 0xC02B
+    TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 = 0xC02F
+    TLS_DHE_DSS_WITH_AES_256_GCM_SHA384 = 0x00A3
+    TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 = 0x009F
+    TLS_DHE_DSS_WITH_AES_128_GCM_SHA256 = 0x00A2
+    TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 = 0x009E
+    TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 = 0xC024
+    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 = 0xC028
+    TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA = 0xC00A
+    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA = 0xC014
+    TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 = 0x006B
+    TLS_DHE_DSS_WITH_AES_256_CBC_SHA256 = 0x006A
+    TLS_DHE_RSA_WITH_AES_256_CBC_SHA = 0x0039
+    TLS_DHE_DSS_WITH_AES_256_CBC_SHA = 0x0038
+    TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 = 0xC023
+    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 = 0xC027
+    TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA = 0xC009
+    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA = 0xC013
+    TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 = 0x0067
+    TLS_DHE_DSS_WITH_AES_128_CBC_SHA256 = 0x0040
+    TLS_DHE_RSA_WITH_AES_128_CBC_SHA = 0x0033
+    TLS_DHE_DSS_WITH_AES_128_CBC_SHA = 0x0032
+    TLS_RSA_WITH_AES_256_GCM_SHA384 = 0x009D
+    TLS_RSA_WITH_AES_128_GCM_SHA256 = 0x009C
+    TLS_RSA_WITH_AES_256_CBC_SHA256 = 0x003D
+    TLS_RSA_WITH_AES_128_CBC_SHA256 = 0x003C
+    TLS_RSA_WITH_AES_256_CBC_SHA = 0x0035
+    TLS_RSA_WITH_AES_128_CBC_SHA = 0x002F
+    TLS_AES_128_GCM_SHA256 = 0x1301
+    TLS_AES_256_GCM_SHA384 = 0x1302
+    TLS_CHACHA20_POLY1305_SHA256 = 0x1303
diff --git a/python/urllib3/contrib/_securetransport/low_level.py b/python/urllib3/contrib/_securetransport/low_level.py
new file mode 100644
index 0000000..b13cd9e
--- /dev/null
+++ b/python/urllib3/contrib/_securetransport/low_level.py
@@ -0,0 +1,346 @@
+"""
+Low-level helpers for the SecureTransport bindings.
+
+These are Python functions that are not directly related to the high-level APIs
+but are necessary to get them to work. They include a whole bunch of low-level
+CoreFoundation messing about and memory management. The concerns in this module
+are almost entirely about trying to avoid memory leaks and providing
+appropriate and useful assistance to the higher-level code.
+"""
+import base64
+import ctypes
+import itertools
+import re
+import os
+import ssl
+import tempfile
+
+from .bindings import Security, CoreFoundation, CFConst
+
+
+# This regular expression is used to grab PEM data out of a PEM bundle.
+_PEM_CERTS_RE = re.compile(
+    b"-----BEGIN CERTIFICATE-----\n(.*?)\n-----END CERTIFICATE-----", re.DOTALL
+)
+
+
+def _cf_data_from_bytes(bytestring):
+    """
+    Given a bytestring, create a CFData object from it. This CFData object must
+    be CFReleased by the caller.
+    """
+    return CoreFoundation.CFDataCreate(
+        CoreFoundation.kCFAllocatorDefault, bytestring, len(bytestring)
+    )
+
+
+def _cf_dictionary_from_tuples(tuples):
+    """
+    Given a list of Python tuples, create an associated CFDictionary.
+    """
+    dictionary_size = len(tuples)
+
+    # We need to get the dictionary keys and values out in the same order.
+    keys = (t[0] for t in tuples)
+    values = (t[1] for t in tuples)
+    cf_keys = (CoreFoundation.CFTypeRef * dictionary_size)(*keys)
+    cf_values = (CoreFoundation.CFTypeRef * dictionary_size)(*values)
+
+    return CoreFoundation.CFDictionaryCreate(
+        CoreFoundation.kCFAllocatorDefault,
+        cf_keys,
+        cf_values,
+        dictionary_size,
+        CoreFoundation.kCFTypeDictionaryKeyCallBacks,
+        CoreFoundation.kCFTypeDictionaryValueCallBacks,
+    )
+
+
+def _cf_string_to_unicode(value):
+    """
+    Creates a Unicode string from a CFString object. Used entirely for error
+    reporting.
+
+    Yes, it annoys me quite a lot that this function is this complex.
+    """
+    value_as_void_p = ctypes.cast(value, ctypes.POINTER(ctypes.c_void_p))
+
+    string = CoreFoundation.CFStringGetCStringPtr(
+        value_as_void_p,
+        CFConst.kCFStringEncodingUTF8
+    )
+    if string is None:
+        buffer = ctypes.create_string_buffer(1024)
+        result = CoreFoundation.CFStringGetCString(
+            value_as_void_p,
+            buffer,
+            1024,
+            CFConst.kCFStringEncodingUTF8
+        )
+        if not result:
+            raise OSError('Error copying C string from CFStringRef')
+        string = buffer.value
+    if string is not None:
+        string = string.decode('utf-8')
+    return string
+
+
+def _assert_no_error(error, exception_class=None):
+    """
+    Checks the return code and throws an exception if there is an error to
+    report
+    """
+    if error == 0:
+        return
+
+    cf_error_string = Security.SecCopyErrorMessageString(error, None)
+    output = _cf_string_to_unicode(cf_error_string)
+    CoreFoundation.CFRelease(cf_error_string)
+
+    if output is None or output == u'':
+        output = u'OSStatus %s' % error
+
+    if exception_class is None:
+        exception_class = ssl.SSLError
+
+    raise exception_class(output)
+
+
+def _cert_array_from_pem(pem_bundle):
+    """
+    Given a bundle of certs in PEM format, turns them into a CFArray of certs
+    that can be used to validate a cert chain.
+    """
+    # Normalize the PEM bundle's line endings.
+    pem_bundle = pem_bundle.replace(b"\r\n", b"\n")
+
+    der_certs = [
+        base64.b64decode(match.group(1))
+        for match in _PEM_CERTS_RE.finditer(pem_bundle)
+    ]
+    if not der_certs:
+        raise ssl.SSLError("No root certificates specified")
+
+    cert_array = CoreFoundation.CFArrayCreateMutable(
+        CoreFoundation.kCFAllocatorDefault,
+        0,
+        ctypes.byref(CoreFoundation.kCFTypeArrayCallBacks)
+    )
+    if not cert_array:
+        raise ssl.SSLError("Unable to allocate memory!")
+
+    try:
+        for der_bytes in der_certs:
+            certdata = _cf_data_from_bytes(der_bytes)
+            if not certdata:
+                raise ssl.SSLError("Unable to allocate memory!")
+            cert = Security.SecCertificateCreateWithData(
+                CoreFoundation.kCFAllocatorDefault, certdata
+            )
+            CoreFoundation.CFRelease(certdata)
+            if not cert:
+                raise ssl.SSLError("Unable to build cert object!")
+
+            CoreFoundation.CFArrayAppendValue(cert_array, cert)
+            CoreFoundation.CFRelease(cert)
+    except Exception:
+        # We need to free the array before the exception bubbles further.
+        # We only want to do that if an error occurs: otherwise, the caller
+        # should free.
+        CoreFoundation.CFRelease(cert_array)
+
+    return cert_array
+
+
+def _is_cert(item):
+    """
+    Returns True if a given CFTypeRef is a certificate.
+    """
+    expected = Security.SecCertificateGetTypeID()
+    return CoreFoundation.CFGetTypeID(item) == expected
+
+
+def _is_identity(item):
+    """
+    Returns True if a given CFTypeRef is an identity.
+    """
+    expected = Security.SecIdentityGetTypeID()
+    return CoreFoundation.CFGetTypeID(item) == expected
+
+
+def _temporary_keychain():
+    """
+    This function creates a temporary Mac keychain that we can use to work with
+    credentials. This keychain uses a one-time password and a temporary file to
+    store the data. We expect to have one keychain per socket. The returned
+    SecKeychainRef must be freed by the caller, including calling
+    SecKeychainDelete.
+
+    Returns a tuple of the SecKeychainRef and the path to the temporary
+    directory that contains it.
+    """
+    # Unfortunately, SecKeychainCreate requires a path to a keychain. This
+    # means we cannot use mkstemp to use a generic temporary file. Instead,
+    # we're going to create a temporary directory and a filename to use there.
+    # This filename will be 8 random bytes expanded into base64. We also need
+    # some random bytes to password-protect the keychain we're creating, so we
+    # ask for 40 random bytes.
+    random_bytes = os.urandom(40)
+    filename = base64.b16encode(random_bytes[:8]).decode('utf-8')
+    password = base64.b16encode(random_bytes[8:])  # Must be valid UTF-8
+    tempdirectory = tempfile.mkdtemp()
+
+    keychain_path = os.path.join(tempdirectory, filename).encode('utf-8')
+
+    # We now want to create the keychain itself.
+    keychain = Security.SecKeychainRef()
+    status = Security.SecKeychainCreate(
+        keychain_path,
+        len(password),
+        password,
+        False,
+        None,
+        ctypes.byref(keychain)
+    )
+    _assert_no_error(status)
+
+    # Having created the keychain, we want to pass it off to the caller.
+    return keychain, tempdirectory
+
+
+def _load_items_from_file(keychain, path):
+    """
+    Given a single file, loads all the trust objects from it into arrays and
+    the keychain.
+    Returns a tuple of lists: the first list is a list of identities, the
+    second a list of certs.
+    """
+    certificates = []
+    identities = []
+    result_array = None
+
+    with open(path, 'rb') as f:
+        raw_filedata = f.read()
+
+    try:
+        filedata = CoreFoundation.CFDataCreate(
+            CoreFoundation.kCFAllocatorDefault,
+            raw_filedata,
+            len(raw_filedata)
+        )
+        result_array = CoreFoundation.CFArrayRef()
+        result = Security.SecItemImport(
+            filedata,  # cert data
+            None,  # Filename, leaving it out for now
+            None,  # What the type of the file is, we don't care
+            None,  # what's in the file, we don't care
+            0,  # import flags
+            None,  # key params, can include passphrase in the future
+            keychain,  # The keychain to insert into
+            ctypes.byref(result_array)  # Results
+        )
+        _assert_no_error(result)
+
+        # A CFArray is not very useful to us as an intermediary
+        # representation, so we are going to extract the objects we want
+        # and then free the array. We don't need to keep hold of keys: the
+        # keychain already has them!
+        result_count = CoreFoundation.CFArrayGetCount(result_array)
+        for index in range(result_count):
+            item = CoreFoundation.CFArrayGetValueAtIndex(
+                result_array, index
+            )
+            item = ctypes.cast(item, CoreFoundation.CFTypeRef)
+
+            if _is_cert(item):
+                CoreFoundation.CFRetain(item)
+                certificates.append(item)
+            elif _is_identity(item):
+                CoreFoundation.CFRetain(item)
+                identities.append(item)
+    finally:
+        if result_array:
+            CoreFoundation.CFRelease(result_array)
+
+        CoreFoundation.CFRelease(filedata)
+
+    return (identities, certificates)
+
+
+def _load_client_cert_chain(keychain, *paths):
+    """
+    Load certificates and maybe keys from a number of files. Has the end goal
+    of returning a CFArray containing one SecIdentityRef, and then zero or more
+    SecCertificateRef objects, suitable for use as a client certificate trust
+    chain.
+    """
+    # Ok, the strategy.
+    #
+    # This relies on knowing that macOS will not give you a SecIdentityRef
+    # unless you have imported a key into a keychain. This is a somewhat
+    # artificial limitation of macOS (for example, it doesn't necessarily
+    # affect iOS), but there is nothing inside Security.framework that lets you
+    # get a SecIdentityRef without having a key in a keychain.
+    #
+    # So the policy here is we take all the files and iterate them in order.
+    # Each one will use SecItemImport to have one or more objects loaded from
+    # it. We will also point at a keychain that macOS can use to work with the
+    # private key.
+    #
+    # Once we have all the objects, we'll check what we actually have. If we
+    # already have a SecIdentityRef in hand, fab: we'll use that. Otherwise,
+    # we'll take the first certificate (which we assume to be our leaf) and
+    # ask the keychain to give us a SecIdentityRef with that cert's associated
+    # key.
+    #
+    # We'll then return a CFArray containing the trust chain: one
+    # SecIdentityRef and then zero-or-more SecCertificateRef objects. The
+    # responsibility for freeing this CFArray will be with the caller. This
+    # CFArray must remain alive for the entire connection, so in practice it
+    # will be stored with a single SSLSocket, along with the reference to the
+    # keychain.
+    certificates = []
+    identities = []
+
+    # Filter out bad paths.
+    paths = (path for path in paths if path)
+
+    try:
+        for file_path in paths:
+            new_identities, new_certs = _load_items_from_file(
+                keychain, file_path
+            )
+            identities.extend(new_identities)
+            certificates.extend(new_certs)
+
+        # Ok, we have everything. The question is: do we have an identity? If
+        # not, we want to grab one from the first cert we have.
+        if not identities:
+            new_identity = Security.SecIdentityRef()
+            status = Security.SecIdentityCreateWithCertificate(
+                keychain,
+                certificates[0],
+                ctypes.byref(new_identity)
+            )
+            _assert_no_error(status)
+            identities.append(new_identity)
+
+            # We now want to release the original certificate, as we no longer
+            # need it.
+            CoreFoundation.CFRelease(certificates.pop(0))
+
+        # We now need to build a new CFArray that holds the trust chain.
+        trust_chain = CoreFoundation.CFArrayCreateMutable(
+            CoreFoundation.kCFAllocatorDefault,
+            0,
+            ctypes.byref(CoreFoundation.kCFTypeArrayCallBacks),
+        )
+        for item in itertools.chain(identities, certificates):
+            # ArrayAppendValue does a CFRetain on the item. That's fine,
+            # because the finally block will release our other refs to them.
+            CoreFoundation.CFArrayAppendValue(trust_chain, item)
+
+        return trust_chain
+    finally:
+        for obj in itertools.chain(identities, certificates):
+            CoreFoundation.CFRelease(obj)
diff --git a/python/urllib3/contrib/appengine.py b/python/urllib3/contrib/appengine.py
new file mode 100644
index 0000000..2952f11
--- /dev/null
+++ b/python/urllib3/contrib/appengine.py
@@ -0,0 +1,289 @@
+"""
+This module provides a pool manager that uses Google App Engine's
+`URLFetch Service <https://cloud.google.com/appengine/docs/python/urlfetch>`_.
+
+Example usage::
+
+    from urllib3 import PoolManager
+    from urllib3.contrib.appengine import AppEngineManager, is_appengine_sandbox
+
+    if is_appengine_sandbox():
+        # AppEngineManager uses AppEngine's URLFetch API behind the scenes
+        http = AppEngineManager()
+    else:
+        # PoolManager uses a socket-level API behind the scenes
+        http = PoolManager()
+
+    r = http.request('GET', 'https://google.com/')
+
+There are `limitations <https://cloud.google.com/appengine/docs/python/\
+urlfetch/#Python_Quotas_and_limits>`_ to the URLFetch service and it may not be
+the best choice for your application. There are three options for using
+urllib3 on Google App Engine:
+
+1. You can use :class:`AppEngineManager` with URLFetch. URLFetch is
+   cost-effective in many circumstances as long as your usage is within the
+   limitations.
+2. You can use a normal :class:`~urllib3.PoolManager` by enabling sockets.
+   Sockets also have `limitations and restrictions
+   <https://cloud.google.com/appengine/docs/python/sockets/\
+   #limitations-and-restrictions>`_ and have a lower free quota than URLFetch.
+   To use sockets, be sure to specify the following in your ``app.yaml``::
+
+        env_variables:
+            GAE_USE_SOCKETS_HTTPLIB : 'true'
+
+3. If you are using `App Engine Flexible
+<https://cloud.google.com/appengine/docs/flexible/>`_, you can use the standard
+:class:`PoolManager` without any configuration or special environment variables.
+"""
+
+from __future__ import absolute_import
+import io
+import logging
+import warnings
+from ..packages.six.moves.urllib.parse import urljoin
+
+from ..exceptions import (
+    HTTPError,
+    HTTPWarning,
+    MaxRetryError,
+    ProtocolError,
+    TimeoutError,
+    SSLError
+)
+
+from ..request import RequestMethods
+from ..response import HTTPResponse
+from ..util.timeout import Timeout
+from ..util.retry import Retry
+from . import _appengine_environ
+
+try:
+    from google.appengine.api import urlfetch
+except ImportError:
+    urlfetch = None
+
+
+log = logging.getLogger(__name__)
+
+
+class AppEnginePlatformWarning(HTTPWarning):
+    pass
+
+
+class AppEnginePlatformError(HTTPError):
+    pass
+
+
+class AppEngineManager(RequestMethods):
+    """
+    Connection manager for Google App Engine sandbox applications.
+
+    This manager uses the URLFetch service directly instead of using the
+    emulated httplib, and is subject to URLFetch limitations as described in
+    the App Engine documentation `here
+    <https://cloud.google.com/appengine/docs/python/urlfetch>`_.
+
+    Notably it will raise an :class:`AppEnginePlatformError` if:
+        * URLFetch is not available.
+        * If you attempt to use this on App Engine Flexible, as full socket
+          support is available.
+        * If a request size is more than 10 megabytes.
+        * If a response size is more than 32 megabtyes.
+        * If you use an unsupported request method such as OPTIONS.
+
+    Beyond those cases, it will raise normal urllib3 errors.
+    """
+
+    def __init__(self, headers=None, retries=None, validate_certificate=True,
+                 urlfetch_retries=True):
+        if not urlfetch:
+            raise AppEnginePlatformError(
+                "URLFetch is not available in this environment.")
+
+        if is_prod_appengine_mvms():
+            raise AppEnginePlatformError(
+                "Use normal urllib3.PoolManager instead of AppEngineManager"
+                "on Managed VMs, as using URLFetch is not necessary in "
+                "this environment.")
+
+        warnings.warn(
+            "urllib3 is using URLFetch on Google App Engine sandbox instead "
+            "of sockets. To use sockets directly instead of URLFetch see "
+            "https://urllib3.readthedocs.io/en/latest/reference/urllib3.contrib.html.",
+            AppEnginePlatformWarning)
+
+        RequestMethods.__init__(self, headers)
+        self.validate_certificate = validate_certificate
+        self.urlfetch_retries = urlfetch_retries
+
+        self.retries = retries or Retry.DEFAULT
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        # Return False to re-raise any potential exceptions
+        return False
+
+    def urlopen(self, method, url, body=None, headers=None,
+                retries=None, redirect=True, timeout=Timeout.DEFAULT_TIMEOUT,
+                **response_kw):
+
+        retries = self._get_retries(retries, redirect)
+
+        try:
+            follow_redirects = (
+                    redirect and
+                    retries.redirect != 0 and
+                    retries.total)
+            response = urlfetch.fetch(
+                url,
+                payload=body,
+                method=method,
+                headers=headers or {},
+                allow_truncated=False,
+                follow_redirects=self.urlfetch_retries and follow_redirects,
+                deadline=self._get_absolute_timeout(timeout),
+                validate_certificate=self.validate_certificate,
+            )
+        except urlfetch.DeadlineExceededError as e:
+            raise TimeoutError(self, e)
+
+        except urlfetch.InvalidURLError as e:
+            if 'too large' in str(e):
+                raise AppEnginePlatformError(
+                    "URLFetch request too large, URLFetch only "
+                    "supports requests up to 10mb in size.", e)
+            raise ProtocolError(e)
+
+        except urlfetch.DownloadError as e:
+            if 'Too many redirects' in str(e):
+                raise MaxRetryError(self, url, reason=e)
+            raise ProtocolError(e)
+
+        except urlfetch.ResponseTooLargeError as e:
+            raise AppEnginePlatformError(
+                "URLFetch response too large, URLFetch only supports"
+                "responses up to 32mb in size.", e)
+
+        except urlfetch.SSLCertificateError as e:
+            raise SSLError(e)
+
+        except urlfetch.InvalidMethodError as e:
+            raise AppEnginePlatformError(
+                "URLFetch does not support method: %s" % method, e)
+
+        http_response = self._urlfetch_response_to_http_response(
+            response, retries=retries, **response_kw)
+
+        # Handle redirect?
+        redirect_location = redirect and http_response.get_redirect_location()
+        if redirect_location:
+            # Check for redirect response
+            if (self.urlfetch_retries and retries.raise_on_redirect):
+                raise MaxRetryError(self, url, "too many redirects")
+            else:
+                if http_response.status == 303:
+                    method = 'GET'
+
+                try:
+                    retries = retries.increment(method, url, response=http_response, _pool=self)
+                except MaxRetryError:
+                    if retries.raise_on_redirect:
+                        raise MaxRetryError(self, url, "too many redirects")
+                    return http_response
+
+                retries.sleep_for_retry(http_response)
+                log.debug("Redirecting %s -> %s", url, redirect_location)
+                redirect_url = urljoin(url, redirect_location)
+                return self.urlopen(
+                    method, redirect_url, body, headers,
+                    retries=retries, redirect=redirect,
+                    timeout=timeout, **response_kw)
+
+        # Check if we should retry the HTTP response.
+        has_retry_after = bool(http_response.getheader('Retry-After'))
+        if retries.is_retry(method, http_response.status, has_retry_after):
+            retries = retries.increment(
+                method, url, response=http_response, _pool=self)
+            log.debug("Retry: %s", url)
+            retries.sleep(http_response)
+            return self.urlopen(
+                method, url,
+                body=body, headers=headers,
+                retries=retries, redirect=redirect,
+                timeout=timeout, **response_kw)
+
+        return http_response
+
+    def _urlfetch_response_to_http_response(self, urlfetch_resp, **response_kw):
+
+        if is_prod_appengine():
+            # Production GAE handles deflate encoding automatically, but does
+            # not remove the encoding header.
+            content_encoding = urlfetch_resp.headers.get('content-encoding')
+
+            if content_encoding == 'deflate':
+                del urlfetch_resp.headers['content-encoding']
+
+        transfer_encoding = urlfetch_resp.headers.get('transfer-encoding')
+        # We have a full response's content,
+        # so let's make sure we don't report ourselves as chunked data.
+        if transfer_encoding == 'chunked':
+            encodings = transfer_encoding.split(",")
+            encodings.remove('chunked')
+            urlfetch_resp.headers['transfer-encoding'] = ','.join(encodings)
+
+        original_response = HTTPResponse(
+            # In order for decoding to work, we must present the content as
+            # a file-like object.
+            body=io.BytesIO(urlfetch_resp.content),
+            msg=urlfetch_resp.header_msg,
+            headers=urlfetch_resp.headers,
+            status=urlfetch_resp.status_code,
+            **response_kw
+        )
+
+        return HTTPResponse(
+            body=io.BytesIO(urlfetch_resp.content),
+            headers=urlfetch_resp.headers,
+            status=urlfetch_resp.status_code,
+            original_response=original_response,
+            **response_kw
+        )
+
+    def _get_absolute_timeout(self, timeout):
+        if timeout is Timeout.DEFAULT_TIMEOUT:
+            return None  # Defer to URLFetch's default.
+        if isinstance(timeout, Timeout):
+            if timeout._read is not None or timeout._connect is not None:
+                warnings.warn(
+                    "URLFetch does not support granular timeout settings, "
+                    "reverting to total or default URLFetch timeout.",
+                    AppEnginePlatformWarning)
+            return timeout.total
+        return timeout
+
+    def _get_retries(self, retries, redirect):
+        if not isinstance(retries, Retry):
+            retries = Retry.from_int(
+                retries, redirect=redirect, default=self.retries)
+
+        if retries.connect or retries.read or retries.redirect:
+            warnings.warn(
+                "URLFetch only supports total retries and does not "
+                "recognize connect, read, or redirect retry parameters.",
+                AppEnginePlatformWarning)
+
+        return retries
+
+
+# Alias methods from _appengine_environ to maintain public API interface.
+
+is_appengine = _appengine_environ.is_appengine
+is_appengine_sandbox = _appengine_environ.is_appengine_sandbox
+is_local_appengine = _appengine_environ.is_local_appengine
+is_prod_appengine = _appengine_environ.is_prod_appengine
+is_prod_appengine_mvms = _appengine_environ.is_prod_appengine_mvms
diff --git a/python/urllib3/contrib/ntlmpool.py b/python/urllib3/contrib/ntlmpool.py
new file mode 100644
index 0000000..8ea127c
--- /dev/null
+++ b/python/urllib3/contrib/ntlmpool.py
@@ -0,0 +1,111 @@
+"""
+NTLM authenticating pool, contributed by erikcederstran
+
+Issue #10, see: http://code.google.com/p/urllib3/issues/detail?id=10
+"""
+from __future__ import absolute_import
+
+from logging import getLogger
+from ntlm import ntlm
+
+from .. import HTTPSConnectionPool
+from ..packages.six.moves.http_client import HTTPSConnection
+
+
+log = getLogger(__name__)
+
+
+class NTLMConnectionPool(HTTPSConnectionPool):
+    """
+    Implements an NTLM authentication version of an urllib3 connection pool
+    """
+
+    scheme = 'https'
+
+    def __init__(self, user, pw, authurl, *args, **kwargs):
+        """
+        authurl is a random URL on the server that is protected by NTLM.
+        user is the Windows user, probably in the DOMAIN\\username format.
+        pw is the password for the user.
+        """
+        super(NTLMConnectionPool, self).__init__(*args, **kwargs)
+        self.authurl = authurl
+        self.rawuser = user
+        user_parts = user.split('\\', 1)
+        self.domain = user_parts[0].upper()
+        self.user = user_parts[1]
+        self.pw = pw
+
+    def _new_conn(self):
+        # Performs the NTLM handshake that secures the connection. The socket
+        # must be kept open while requests are performed.
+        self.num_connections += 1
+        log.debug('Starting NTLM HTTPS connection no. %d: https://%s%s',
+                  self.num_connections, self.host, self.authurl)
+
+        headers = {'Connection': 'Keep-Alive'}
+        req_header = 'Authorization'
+        resp_header = 'www-authenticate'
+
+        conn = HTTPSConnection(host=self.host, port=self.port)
+
+        # Send negotiation message
+        headers[req_header] = (
+            'NTLM %s' % ntlm.create_NTLM_NEGOTIATE_MESSAGE(self.rawuser))
+        log.debug('Request headers: %s', headers)
+        conn.request('GET', self.authurl, None, headers)
+        res = conn.getresponse()
+        reshdr = dict(res.getheaders())
+        log.debug('Response status: %s %s', res.status, res.reason)
+        log.debug('Response headers: %s', reshdr)
+        log.debug('Response data: %s [...]', res.read(100))
+
+        # Remove the reference to the socket, so that it can not be closed by
+        # the response object (we want to keep the socket open)
+        res.fp = None
+
+        # Server should respond with a challenge message
+        auth_header_values = reshdr[resp_header].split(', ')
+        auth_header_value = None
+        for s in auth_header_values:
+            if s[:5] == 'NTLM ':
+                auth_header_value = s[5:]
+        if auth_header_value is None:
+            raise Exception('Unexpected %s response header: %s' %
+                            (resp_header, reshdr[resp_header]))
+
+        # Send authentication message
+        ServerChallenge, NegotiateFlags = \
+            ntlm.parse_NTLM_CHALLENGE_MESSAGE(auth_header_value)
+        auth_msg = ntlm.create_NTLM_AUTHENTICATE_MESSAGE(ServerChallenge,
+                                                         self.user,
+                                                         self.domain,
+                                                         self.pw,
+                                                         NegotiateFlags)
+        headers[req_header] = 'NTLM %s' % auth_msg
+        log.debug('Request headers: %s', headers)
+        conn.request('GET', self.authurl, None, headers)
+        res = conn.getresponse()
+        log.debug('Response status: %s %s', res.status, res.reason)
+        log.debug('Response headers: %s', dict(res.getheaders()))
+        log.debug('Response data: %s [...]', res.read()[:100])
+        if res.status != 200:
+            if res.status == 401:
+                raise Exception('Server rejected request: wrong '
+                                'username or password')
+            raise Exception('Wrong server response: %s %s' %
+                            (res.status, res.reason))
+
+        res.fp = None
+        log.debug('Connection established')
+        return conn
+
+    def urlopen(self, method, url, body=None, headers=None, retries=3,
+                redirect=True, assert_same_host=True):
+        if headers is None:
+            headers = {}
+        headers['Connection'] = 'Keep-Alive'
+        return super(NTLMConnectionPool, self).urlopen(method, url, body,
+                                                       headers, retries,
+                                                       redirect,
+                                                       assert_same_host)
diff --git a/python/urllib3/contrib/pyopenssl.py b/python/urllib3/contrib/pyopenssl.py
new file mode 100644
index 0000000..7c0e946
--- /dev/null
+++ b/python/urllib3/contrib/pyopenssl.py
@@ -0,0 +1,466 @@
+"""
+SSL with SNI_-support for Python 2. Follow these instructions if you would
+like to verify SSL certificates in Python 2. Note, the default libraries do
+*not* do certificate checking; you need to do additional work to validate
+certificates yourself.
+
+This needs the following packages installed:
+
+* pyOpenSSL (tested with 16.0.0)
+* cryptography (minimum 1.3.4, from pyopenssl)
+* idna (minimum 2.0, from cryptography)
+
+However, pyopenssl depends on cryptography, which depends on idna, so while we
+use all three directly here we end up having relatively few packages required.
+
+You can install them with the following command:
+
+    pip install pyopenssl cryptography idna
+
+To activate certificate checking, call
+:func:`~urllib3.contrib.pyopenssl.inject_into_urllib3` from your Python code
+before you begin making HTTP requests. This can be done in a ``sitecustomize``
+module, or at any other time before your application begins using ``urllib3``,
+like this::
+
+    try:
+        import urllib3.contrib.pyopenssl
+        urllib3.contrib.pyopenssl.inject_into_urllib3()
+    except ImportError:
+        pass
+
+Now you can use :mod:`urllib3` as you normally would, and it will support SNI
+when the required modules are installed.
+
+Activating this module also has the positive side effect of disabling SSL/TLS
+compression in Python 2 (see `CRIME attack`_).
+
+If you want to configure the default list of supported cipher suites, you can
+set the ``urllib3.contrib.pyopenssl.DEFAULT_SSL_CIPHER_LIST`` variable.
+
+.. _sni: https://en.wikipedia.org/wiki/Server_Name_Indication
+.. _crime attack: https://en.wikipedia.org/wiki/CRIME_(security_exploit)
+"""
+from __future__ import absolute_import
+
+import OpenSSL.SSL
+from cryptography import x509
+from cryptography.hazmat.backends.openssl import backend as openssl_backend
+from cryptography.hazmat.backends.openssl.x509 import _Certificate
+try:
+    from cryptography.x509 import UnsupportedExtension
+except ImportError:
+    # UnsupportedExtension is gone in cryptography >= 2.1.0
+    class UnsupportedExtension(Exception):
+        pass
+
+from socket import timeout, error as SocketError
+from io import BytesIO
+
+try:  # Platform-specific: Python 2
+    from socket import _fileobject
+except ImportError:  # Platform-specific: Python 3
+    _fileobject = None
+    from ..packages.backports.makefile import backport_makefile
+
+import logging
+import ssl
+from ..packages import six
+import sys
+
+from .. import util
+
+__all__ = ['inject_into_urllib3', 'extract_from_urllib3']
+
+# SNI always works.
+HAS_SNI = True
+
+# Map from urllib3 to PyOpenSSL compatible parameter-values.
+_openssl_versions = {
+    ssl.PROTOCOL_SSLv23: OpenSSL.SSL.SSLv23_METHOD,
+    ssl.PROTOCOL_TLSv1: OpenSSL.SSL.TLSv1_METHOD,
+}
+
+if hasattr(ssl, 'PROTOCOL_TLSv1_1') and hasattr(OpenSSL.SSL, 'TLSv1_1_METHOD'):
+    _openssl_versions[ssl.PROTOCOL_TLSv1_1] = OpenSSL.SSL.TLSv1_1_METHOD
+
+if hasattr(ssl, 'PROTOCOL_TLSv1_2') and hasattr(OpenSSL.SSL, 'TLSv1_2_METHOD'):
+    _openssl_versions[ssl.PROTOCOL_TLSv1_2] = OpenSSL.SSL.TLSv1_2_METHOD
+
+try:
+    _openssl_versions.update({ssl.PROTOCOL_SSLv3: OpenSSL.SSL.SSLv3_METHOD})
+except AttributeError:
+    pass
+
+_stdlib_to_openssl_verify = {
+    ssl.CERT_NONE: OpenSSL.SSL.VERIFY_NONE,
+    ssl.CERT_OPTIONAL: OpenSSL.SSL.VERIFY_PEER,
+    ssl.CERT_REQUIRED:
+        OpenSSL.SSL.VERIFY_PEER + OpenSSL.SSL.VERIFY_FAIL_IF_NO_PEER_CERT,
+}
+_openssl_to_stdlib_verify = dict(
+    (v, k) for k, v in _stdlib_to_openssl_verify.items()
+)
+
+# OpenSSL will only write 16K at a time
+SSL_WRITE_BLOCKSIZE = 16384
+
+orig_util_HAS_SNI = util.HAS_SNI
+orig_util_SSLContext = util.ssl_.SSLContext
+
+
+log = logging.getLogger(__name__)
+
+
+def inject_into_urllib3():
+    'Monkey-patch urllib3 with PyOpenSSL-backed SSL-support.'
+
+    _validate_dependencies_met()
+
+    util.ssl_.SSLContext = PyOpenSSLContext
+    util.HAS_SNI = HAS_SNI
+    util.ssl_.HAS_SNI = HAS_SNI
+    util.IS_PYOPENSSL = True
+    util.ssl_.IS_PYOPENSSL = True
+
+
+def extract_from_urllib3():
+    'Undo monkey-patching by :func:`inject_into_urllib3`.'
+
+    util.ssl_.SSLContext = orig_util_SSLContext
+    util.HAS_SNI = orig_util_HAS_SNI
+    util.ssl_.HAS_SNI = orig_util_HAS_SNI
+    util.IS_PYOPENSSL = False
+    util.ssl_.IS_PYOPENSSL = False
+
+
+def _validate_dependencies_met():
+    """
+    Verifies that PyOpenSSL's package-level dependencies have been met.
+    Throws `ImportError` if they are not met.
+    """
+    # Method added in `cryptography==1.1`; not available in older versions
+    from cryptography.x509.extensions import Extensions
+    if getattr(Extensions, "get_extension_for_class", None) is None:
+        raise ImportError("'cryptography' module missing required functionality.  "
+                          "Try upgrading to v1.3.4 or newer.")
+
+    # pyOpenSSL 0.14 and above use cryptography for OpenSSL bindings. The _x509
+    # attribute is only present on those versions.
+    from OpenSSL.crypto import X509
+    x509 = X509()
+    if getattr(x509, "_x509", None) is None:
+        raise ImportError("'pyOpenSSL' module missing required functionality. "
+                          "Try upgrading to v0.14 or newer.")
+
+
+def _dnsname_to_stdlib(name):
+    """
+    Converts a dNSName SubjectAlternativeName field to the form used by the
+    standard library on the given Python version.
+
+    Cryptography produces a dNSName as a unicode string that was idna-decoded
+    from ASCII bytes. We need to idna-encode that string to get it back, and
+    then on Python 3 we also need to convert to unicode via UTF-8 (the stdlib
+    uses PyUnicode_FromStringAndSize on it, which decodes via UTF-8).
+
+    If the name cannot be idna-encoded then we return None signalling that
+    the name given should be skipped.
+    """
+    def idna_encode(name):
+        """
+        Borrowed wholesale from the Python Cryptography Project. It turns out
+        that we can't just safely call `idna.encode`: it can explode for
+        wildcard names. This avoids that problem.
+        """
+        import idna
+
+        try:
+            for prefix in [u'*.', u'.']:
+                if name.startswith(prefix):
+                    name = name[len(prefix):]
+                    return prefix.encode('ascii') + idna.encode(name)
+            return idna.encode(name)
+        except idna.core.IDNAError:
+            return None
+
+    name = idna_encode(name)
+    if name is None:
+        return None
+    elif sys.version_info >= (3, 0):
+        name = name.decode('utf-8')
+    return name
+
+
+def get_subj_alt_name(peer_cert):
+    """
+    Given an PyOpenSSL certificate, provides all the subject alternative names.
+    """
+    # Pass the cert to cryptography, which has much better APIs for this.
+    if hasattr(peer_cert, "to_cryptography"):
+        cert = peer_cert.to_cryptography()
+    else:
+        # This is technically using private APIs, but should work across all
+        # relevant versions before PyOpenSSL got a proper API for this.
+        cert = _Certificate(openssl_backend, peer_cert._x509)
+
+    # We want to find the SAN extension. Ask Cryptography to locate it (it's
+    # faster than looping in Python)
+    try:
+        ext = cert.extensions.get_extension_for_class(
+            x509.SubjectAlternativeName
+        ).value
+    except x509.ExtensionNotFound:
+        # No such extension, return the empty list.
+        return []
+    except (x509.DuplicateExtension, UnsupportedExtension,
+            x509.UnsupportedGeneralNameType, UnicodeError) as e:
+        # A problem has been found with the quality of the certificate. Assume
+        # no SAN field is present.
+        log.warning(
+            "A problem was encountered with the certificate that prevented "
+            "urllib3 from finding the SubjectAlternativeName field. This can "
+            "affect certificate validation. The error was %s",
+            e,
+        )
+        return []
+
+    # We want to return dNSName and iPAddress fields. We need to cast the IPs
+    # back to strings because the match_hostname function wants them as
+    # strings.
+    # Sadly the DNS names need to be idna encoded and then, on Python 3, UTF-8
+    # decoded. This is pretty frustrating, but that's what the standard library
+    # does with certificates, and so we need to attempt to do the same.
+    # We also want to skip over names which cannot be idna encoded.
+    names = [
+        ('DNS', name) for name in map(_dnsname_to_stdlib, ext.get_values_for_type(x509.DNSName))
+        if name is not None
+    ]
+    names.extend(
+        ('IP Address', str(name))
+        for name in ext.get_values_for_type(x509.IPAddress)
+    )
+
+    return names
+
+
+class WrappedSocket(object):
+    '''API-compatibility wrapper for Python OpenSSL's Connection-class.
+
+    Note: _makefile_refs, _drop() and _reuse() are needed for the garbage
+    collector of pypy.
+    '''
+
+    def __init__(self, connection, socket, suppress_ragged_eofs=True):
+        self.connection = connection
+        self.socket = socket
+        self.suppress_ragged_eofs = suppress_ragged_eofs
+        self._makefile_refs = 0
+        self._closed = False
+
+    def fileno(self):
+        return self.socket.fileno()
+
+    # Copy-pasted from Python 3.5 source code
+    def _decref_socketios(self):
+        if self._makefile_refs > 0:
+            self._makefile_refs -= 1
+        if self._closed:
+            self.close()
+
+    def recv(self, *args, **kwargs):
+        try:
+            data = self.connection.recv(*args, **kwargs)
+        except OpenSSL.SSL.SysCallError as e:
+            if self.suppress_ragged_eofs and e.args == (-1, 'Unexpected EOF'):
+                return b''
+            else:
+                raise SocketError(str(e))
+        except OpenSSL.SSL.ZeroReturnError as e:
+            if self.connection.get_shutdown() == OpenSSL.SSL.RECEIVED_SHUTDOWN:
+                return b''
+            else:
+                raise
+        except OpenSSL.SSL.WantReadError:
+            if not util.wait_for_read(self.socket, self.socket.gettimeout()):
+                raise timeout('The read operation timed out')
+            else:
+                return self.recv(*args, **kwargs)
+        else:
+            return data
+
+    def recv_into(self, *args, **kwargs):
+        try:
+            return self.connection.recv_into(*args, **kwargs)
+        except OpenSSL.SSL.SysCallError as e:
+            if self.suppress_ragged_eofs and e.args == (-1, 'Unexpected EOF'):
+                return 0
+            else:
+                raise SocketError(str(e))
+        except OpenSSL.SSL.ZeroReturnError as e:
+            if self.connection.get_shutdown() == OpenSSL.SSL.RECEIVED_SHUTDOWN:
+                return 0
+            else:
+                raise
+        except OpenSSL.SSL.WantReadError:
+            if not util.wait_for_read(self.socket, self.socket.gettimeout()):
+                raise timeout('The read operation timed out')
+            else:
+                return self.recv_into(*args, **kwargs)
+
+    def settimeout(self, timeout):
+        return self.socket.settimeout(timeout)
+
+    def _send_until_done(self, data):
+        while True:
+            try:
+                return self.connection.send(data)
+            except OpenSSL.SSL.WantWriteError:
+                if not util.wait_for_write(self.socket, self.socket.gettimeout()):
+                    raise timeout()
+                continue
+            except OpenSSL.SSL.SysCallError as e:
+                raise SocketError(str(e))
+
+    def sendall(self, data):
+        total_sent = 0
+        while total_sent < len(data):
+            sent = self._send_until_done(data[total_sent:total_sent + SSL_WRITE_BLOCKSIZE])
+            total_sent += sent
+
+    def shutdown(self):
+        # FIXME rethrow compatible exceptions should we ever use this
+        self.connection.shutdown()
+
+    def close(self):
+        if self._makefile_refs < 1:
+            try:
+                self._closed = True
+                return self.connection.close()
+            except OpenSSL.SSL.Error:
+                return
+        else:
+            self._makefile_refs -= 1
+
+    def getpeercert(self, binary_form=False):
+        x509 = self.connection.get_peer_certificate()
+
+        if not x509:
+            return x509
+
+        if binary_form:
+            return OpenSSL.crypto.dump_certificate(
+                OpenSSL.crypto.FILETYPE_ASN1,
+                x509)
+
+        return {
+            'subject': (
+                (('commonName', x509.get_subject().CN),),
+            ),
+            'subjectAltName': get_subj_alt_name(x509)
+        }
+
+    def _reuse(self):
+        self._makefile_refs += 1
+
+    def _drop(self):
+        if self._makefile_refs < 1:
+            self.close()
+        else:
+            self._makefile_refs -= 1
+
+
+if _fileobject:  # Platform-specific: Python 2
+    def makefile(self, mode, bufsize=-1):
+        self._makefile_refs += 1
+        return _fileobject(self, mode, bufsize, close=True)
+else:  # Platform-specific: Python 3
+    makefile = backport_makefile
+
+WrappedSocket.makefile = makefile
+
+
+class PyOpenSSLContext(object):
+    """
+    I am a wrapper class for the PyOpenSSL ``Context`` object. I am responsible
+    for translating the interface of the standard library ``SSLContext`` object
+    to calls into PyOpenSSL.
+    """
+    def __init__(self, protocol):
+        self.protocol = _openssl_versions[protocol]
+        self._ctx = OpenSSL.SSL.Context(self.protocol)
+        self._options = 0
+        self.check_hostname = False
+
+    @property
+    def options(self):
+        return self._options
+
+    @options.setter
+    def options(self, value):
+        self._options = value
+        self._ctx.set_options(value)
+
+    @property
+    def verify_mode(self):
+        return _openssl_to_stdlib_verify[self._ctx.get_verify_mode()]
+
+    @verify_mode.setter
+    def verify_mode(self, value):
+        self._ctx.set_verify(
+            _stdlib_to_openssl_verify[value],
+            _verify_callback
+        )
+
+    def set_default_verify_paths(self):
+        self._ctx.set_default_verify_paths()
+
+    def set_ciphers(self, ciphers):
+        if isinstance(ciphers, six.text_type):
+            ciphers = ciphers.encode('utf-8')
+        self._ctx.set_cipher_list(ciphers)
+
+    def load_verify_locations(self, cafile=None, capath=None, cadata=None):
+        if cafile is not None:
+            cafile = cafile.encode('utf-8')
+        if capath is not None:
+            capath = capath.encode('utf-8')
+        self._ctx.load_verify_locations(cafile, capath)
+        if cadata is not None:
+            self._ctx.load_verify_locations(BytesIO(cadata))
+
+    def load_cert_chain(self, certfile, keyfile=None, password=None):
+        self._ctx.use_certificate_chain_file(certfile)
+        if password is not None:
+            self._ctx.set_passwd_cb(lambda max_length, prompt_twice, userdata: password)
+        self._ctx.use_privatekey_file(keyfile or certfile)
+
+    def wrap_socket(self, sock, server_side=False,
+                    do_handshake_on_connect=True, suppress_ragged_eofs=True,
+                    server_hostname=None):
+        cnx = OpenSSL.SSL.Connection(self._ctx, sock)
+
+        if isinstance(server_hostname, six.text_type):  # Platform-specific: Python 3
+            server_hostname = server_hostname.encode('utf-8')
+
+        if server_hostname is not None:
+            cnx.set_tlsext_host_name(server_hostname)
+
+        cnx.set_connect_state()
+
+        while True:
+            try:
+                cnx.do_handshake()
+            except OpenSSL.SSL.WantReadError:
+                if not util.wait_for_read(sock, sock.gettimeout()):
+                    raise timeout('select timed out')
+                continue
+            except OpenSSL.SSL.Error as e:
+                raise ssl.SSLError('bad handshake: %r' % e)
+            break
+
+        return WrappedSocket(cnx, sock)
+
+
+def _verify_callback(cnx, x509, err_no, err_depth, return_code):
+    return err_no == 0
diff --git a/python/urllib3/contrib/securetransport.py b/python/urllib3/contrib/securetransport.py
new file mode 100644
index 0000000..77cb59e
--- /dev/null
+++ b/python/urllib3/contrib/securetransport.py
@@ -0,0 +1,804 @@
+"""
+SecureTranport support for urllib3 via ctypes.
+
+This makes platform-native TLS available to urllib3 users on macOS without the
+use of a compiler. This is an important feature because the Python Package
+Index is moving to become a TLSv1.2-or-higher server, and the default OpenSSL
+that ships with macOS is not capable of doing TLSv1.2. The only way to resolve
+this is to give macOS users an alternative solution to the problem, and that
+solution is to use SecureTransport.
+
+We use ctypes here because this solution must not require a compiler. That's
+because pip is not allowed to require a compiler either.
+
+This is not intended to be a seriously long-term solution to this problem.
+The hope is that PEP 543 will eventually solve this issue for us, at which
+point we can retire this contrib module. But in the short term, we need to
+solve the impending tire fire that is Python on Mac without this kind of
+contrib module. So...here we are.
+
+To use this module, simply import and inject it::
+
+    import urllib3.contrib.securetransport
+    urllib3.contrib.securetransport.inject_into_urllib3()
+
+Happy TLSing!
+"""
+from __future__ import absolute_import
+
+import contextlib
+import ctypes
+import errno
+import os.path
+import shutil
+import socket
+import ssl
+import threading
+import weakref
+
+from .. import util
+from ._securetransport.bindings import (
+    Security, SecurityConst, CoreFoundation
+)
+from ._securetransport.low_level import (
+    _assert_no_error, _cert_array_from_pem, _temporary_keychain,
+    _load_client_cert_chain
+)
+
+try:  # Platform-specific: Python 2
+    from socket import _fileobject
+except ImportError:  # Platform-specific: Python 3
+    _fileobject = None
+    from ..packages.backports.makefile import backport_makefile
+
+__all__ = ['inject_into_urllib3', 'extract_from_urllib3']
+
+# SNI always works
+HAS_SNI = True
+
+orig_util_HAS_SNI = util.HAS_SNI
+orig_util_SSLContext = util.ssl_.SSLContext
+
+# This dictionary is used by the read callback to obtain a handle to the
+# calling wrapped socket. This is a pretty silly approach, but for now it'll
+# do. I feel like I should be able to smuggle a handle to the wrapped socket
+# directly in the SSLConnectionRef, but for now this approach will work I
+# guess.
+#
+# We need to lock around this structure for inserts, but we don't do it for
+# reads/writes in the callbacks. The reasoning here goes as follows:
+#
+#    1. It is not possible to call into the callbacks before the dictionary is
+#       populated, so once in the callback the id must be in the dictionary.
+#    2. The callbacks don't mutate the dictionary, they only read from it, and
+#       so cannot conflict with any of the insertions.
+#
+# This is good: if we had to lock in the callbacks we'd drastically slow down
+# the performance of this code.
+_connection_refs = weakref.WeakValueDictionary()
+_connection_ref_lock = threading.Lock()
+
+# Limit writes to 16kB. This is OpenSSL's limit, but we'll cargo-cult it over
+# for no better reason than we need *a* limit, and this one is right there.
+SSL_WRITE_BLOCKSIZE = 16384
+
+# This is our equivalent of util.ssl_.DEFAULT_CIPHERS, but expanded out to
+# individual cipher suites. We need to do this because this is how
+# SecureTransport wants them.
+CIPHER_SUITES = [
+    SecurityConst.TLS_AES_256_GCM_SHA384,
+    SecurityConst.TLS_CHACHA20_POLY1305_SHA256,
+    SecurityConst.TLS_AES_128_GCM_SHA256,
+    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+    SecurityConst.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+    SecurityConst.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+    SecurityConst.TLS_DHE_DSS_WITH_AES_256_GCM_SHA384,
+    SecurityConst.TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,
+    SecurityConst.TLS_DHE_DSS_WITH_AES_128_GCM_SHA256,
+    SecurityConst.TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,
+    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384,
+    SecurityConst.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384,
+    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
+    SecurityConst.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
+    SecurityConst.TLS_DHE_RSA_WITH_AES_256_CBC_SHA256,
+    SecurityConst.TLS_DHE_DSS_WITH_AES_256_CBC_SHA256,
+    SecurityConst.TLS_DHE_RSA_WITH_AES_256_CBC_SHA,
+    SecurityConst.TLS_DHE_DSS_WITH_AES_256_CBC_SHA,
+    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
+    SecurityConst.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
+    SecurityConst.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
+    SecurityConst.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
+    SecurityConst.TLS_DHE_RSA_WITH_AES_128_CBC_SHA256,
+    SecurityConst.TLS_DHE_DSS_WITH_AES_128_CBC_SHA256,
+    SecurityConst.TLS_DHE_RSA_WITH_AES_128_CBC_SHA,
+    SecurityConst.TLS_DHE_DSS_WITH_AES_128_CBC_SHA,
+    SecurityConst.TLS_RSA_WITH_AES_256_GCM_SHA384,
+    SecurityConst.TLS_RSA_WITH_AES_128_GCM_SHA256,
+    SecurityConst.TLS_RSA_WITH_AES_256_CBC_SHA256,
+    SecurityConst.TLS_RSA_WITH_AES_128_CBC_SHA256,
+    SecurityConst.TLS_RSA_WITH_AES_256_CBC_SHA,
+    SecurityConst.TLS_RSA_WITH_AES_128_CBC_SHA,
+]
+
+# Basically this is simple: for PROTOCOL_SSLv23 we turn it into a low of
+# TLSv1 and a high of TLSv1.2. For everything else, we pin to that version.
+_protocol_to_min_max = {
+    ssl.PROTOCOL_SSLv23: (SecurityConst.kTLSProtocol1, SecurityConst.kTLSProtocol12),
+}
+
+if hasattr(ssl, "PROTOCOL_SSLv2"):
+    _protocol_to_min_max[ssl.PROTOCOL_SSLv2] = (
+        SecurityConst.kSSLProtocol2, SecurityConst.kSSLProtocol2
+    )
+if hasattr(ssl, "PROTOCOL_SSLv3"):
+    _protocol_to_min_max[ssl.PROTOCOL_SSLv3] = (
+        SecurityConst.kSSLProtocol3, SecurityConst.kSSLProtocol3
+    )
+if hasattr(ssl, "PROTOCOL_TLSv1"):
+    _protocol_to_min_max[ssl.PROTOCOL_TLSv1] = (
+        SecurityConst.kTLSProtocol1, SecurityConst.kTLSProtocol1
+    )
+if hasattr(ssl, "PROTOCOL_TLSv1_1"):
+    _protocol_to_min_max[ssl.PROTOCOL_TLSv1_1] = (
+        SecurityConst.kTLSProtocol11, SecurityConst.kTLSProtocol11
+    )
+if hasattr(ssl, "PROTOCOL_TLSv1_2"):
+    _protocol_to_min_max[ssl.PROTOCOL_TLSv1_2] = (
+        SecurityConst.kTLSProtocol12, SecurityConst.kTLSProtocol12
+    )
+if hasattr(ssl, "PROTOCOL_TLS"):
+    _protocol_to_min_max[ssl.PROTOCOL_TLS] = _protocol_to_min_max[ssl.PROTOCOL_SSLv23]
+
+
+def inject_into_urllib3():
+    """
+    Monkey-patch urllib3 with SecureTransport-backed SSL-support.
+    """
+    util.ssl_.SSLContext = SecureTransportContext
+    util.HAS_SNI = HAS_SNI
+    util.ssl_.HAS_SNI = HAS_SNI
+    util.IS_SECURETRANSPORT = True
+    util.ssl_.IS_SECURETRANSPORT = True
+
+
+def extract_from_urllib3():
+    """
+    Undo monkey-patching by :func:`inject_into_urllib3`.
+    """
+    util.ssl_.SSLContext = orig_util_SSLContext
+    util.HAS_SNI = orig_util_HAS_SNI
+    util.ssl_.HAS_SNI = orig_util_HAS_SNI
+    util.IS_SECURETRANSPORT = False
+    util.ssl_.IS_SECURETRANSPORT = False
+
+
+def _read_callback(connection_id, data_buffer, data_length_pointer):
+    """
+    SecureTransport read callback. This is called by ST to request that data
+    be returned from the socket.
+    """
+    wrapped_socket = None
+    try:
+        wrapped_socket = _connection_refs.get(connection_id)
+        if wrapped_socket is None:
+            return SecurityConst.errSSLInternal
+        base_socket = wrapped_socket.socket
+
+        requested_length = data_length_pointer[0]
+
+        timeout = wrapped_socket.gettimeout()
+        error = None
+        read_count = 0
+
+        try:
+            while read_count < requested_length:
+                if timeout is None or timeout >= 0:
+                    if not util.wait_for_read(base_socket, timeout):
+                        raise socket.error(errno.EAGAIN, 'timed out')
+
+                remaining = requested_length - read_count
+                buffer = (ctypes.c_char * remaining).from_address(
+                    data_buffer + read_count
+                )
+                chunk_size = base_socket.recv_into(buffer, remaining)
+                read_count += chunk_size
+                if not chunk_size:
+                    if not read_count:
+                        return SecurityConst.errSSLClosedGraceful
+                    break
+        except (socket.error) as e:
+            error = e.errno
+
+            if error is not None and error != errno.EAGAIN:
+                data_length_pointer[0] = read_count
+                if error == errno.ECONNRESET or error == errno.EPIPE:
+                    return SecurityConst.errSSLClosedAbort
+                raise
+
+        data_length_pointer[0] = read_count
+
+        if read_count != requested_length:
+            return SecurityConst.errSSLWouldBlock
+
+        return 0
+    except Exception as e:
+        if wrapped_socket is not None:
+            wrapped_socket._exception = e
+        return SecurityConst.errSSLInternal
+
+
+def _write_callback(connection_id, data_buffer, data_length_pointer):
+    """
+    SecureTransport write callback. This is called by ST to request that data
+    actually be sent on the network.
+    """
+    wrapped_socket = None
+    try:
+        wrapped_socket = _connection_refs.get(connection_id)
+        if wrapped_socket is None:
+            return SecurityConst.errSSLInternal
+        base_socket = wrapped_socket.socket
+
+        bytes_to_write = data_length_pointer[0]
+        data = ctypes.string_at(data_buffer, bytes_to_write)
+
+        timeout = wrapped_socket.gettimeout()
+        error = None
+        sent = 0
+
+        try:
+            while sent < bytes_to_write:
+                if timeout is None or timeout >= 0:
+                    if not util.wait_for_write(base_socket, timeout):
+                        raise socket.error(errno.EAGAIN, 'timed out')
+                chunk_sent = base_socket.send(data)
+                sent += chunk_sent
+
+                # This has some needless copying here, but I'm not sure there's
+                # much value in optimising this data path.
+                data = data[chunk_sent:]
+        except (socket.error) as e:
+            error = e.errno
+
+            if error is not None and error != errno.EAGAIN:
+                data_length_pointer[0] = sent
+                if error == errno.ECONNRESET or error == errno.EPIPE:
+                    return SecurityConst.errSSLClosedAbort
+                raise
+
+        data_length_pointer[0] = sent
+
+        if sent != bytes_to_write:
+            return SecurityConst.errSSLWouldBlock
+
+        return 0
+    except Exception as e:
+        if wrapped_socket is not None:
+            wrapped_socket._exception = e
+        return SecurityConst.errSSLInternal
+
+
+# We need to keep these two objects references alive: if they get GC'd while
+# in use then SecureTransport could attempt to call a function that is in freed
+# memory. That would be...uh...bad. Yeah, that's the word. Bad.
+_read_callback_pointer = Security.SSLReadFunc(_read_callback)
+_write_callback_pointer = Security.SSLWriteFunc(_write_callback)
+
+
+class WrappedSocket(object):
+    """
+    API-compatibility wrapper for Python's OpenSSL wrapped socket object.
+
+    Note: _makefile_refs, _drop(), and _reuse() are needed for the garbage
+    collector of PyPy.
+    """
+    def __init__(self, socket):
+        self.socket = socket
+        self.context = None
+        self._makefile_refs = 0
+        self._closed = False
+        self._exception = None
+        self._keychain = None
+        self._keychain_dir = None
+        self._client_cert_chain = None
+
+        # We save off the previously-configured timeout and then set it to
+        # zero. This is done because we use select and friends to handle the
+        # timeouts, but if we leave the timeout set on the lower socket then
+        # Python will "kindly" call select on that socket again for us. Avoid
+        # that by forcing the timeout to zero.
+        self._timeout = self.socket.gettimeout()
+        self.socket.settimeout(0)
+
+    @contextlib.contextmanager
+    def _raise_on_error(self):
+        """
+        A context manager that can be used to wrap calls that do I/O from
+        SecureTransport. If any of the I/O callbacks hit an exception, this
+        context manager will correctly propagate the exception after the fact.
+        This avoids silently swallowing those exceptions.
+
+        It also correctly forces the socket closed.
+        """
+        self._exception = None
+
+        # We explicitly don't catch around this yield because in the unlikely
+        # event that an exception was hit in the block we don't want to swallow
+        # it.
+        yield
+        if self._exception is not None:
+            exception, self._exception = self._exception, None
+            self.close()
+            raise exception
+
+    def _set_ciphers(self):
+        """
+        Sets up the allowed ciphers. By default this matches the set in
+        util.ssl_.DEFAULT_CIPHERS, at least as supported by macOS. This is done
+        custom and doesn't allow changing at this time, mostly because parsing
+        OpenSSL cipher strings is going to be a freaking nightmare.
+        """
+        ciphers = (Security.SSLCipherSuite * len(CIPHER_SUITES))(*CIPHER_SUITES)
+        result = Security.SSLSetEnabledCiphers(
+            self.context, ciphers, len(CIPHER_SUITES)
+        )
+        _assert_no_error(result)
+
+    def _custom_validate(self, verify, trust_bundle):
+        """
+        Called when we have set custom validation. We do this in two cases:
+        first, when cert validation is entirely disabled; and second, when
+        using a custom trust DB.
+        """
+        # If we disabled cert validation, just say: cool.
+        if not verify:
+            return
+
+        # We want data in memory, so load it up.
+        if os.path.isfile(trust_bundle):
+            with open(trust_bundle, 'rb') as f:
+                trust_bundle = f.read()
+
+        cert_array = None
+        trust = Security.SecTrustRef()
+
+        try:
+            # Get a CFArray that contains the certs we want.
+            cert_array = _cert_array_from_pem(trust_bundle)
+
+            # Ok, now the hard part. We want to get the SecTrustRef that ST has
+            # created for this connection, shove our CAs into it, tell ST to
+            # ignore everything else it knows, and then ask if it can build a
+            # chain. This is a buuuunch of code.
+            result = Security.SSLCopyPeerTrust(
+                self.context, ctypes.byref(trust)
+            )
+            _assert_no_error(result)
+            if not trust:
+                raise ssl.SSLError("Failed to copy trust reference")
+
+            result = Security.SecTrustSetAnchorCertificates(trust, cert_array)
+            _assert_no_error(result)
+
+            result = Security.SecTrustSetAnchorCertificatesOnly(trust, True)
+            _assert_no_error(result)
+
+            trust_result = Security.SecTrustResultType()
+            result = Security.SecTrustEvaluate(
+                trust, ctypes.byref(trust_result)
+            )
+            _assert_no_error(result)
+        finally:
+            if trust:
+                CoreFoundation.CFRelease(trust)
+
+            if cert_array is not None:
+                CoreFoundation.CFRelease(cert_array)
+
+        # Ok, now we can look at what the result was.
+        successes = (
+            SecurityConst.kSecTrustResultUnspecified,
+            SecurityConst.kSecTrustResultProceed
+        )
+        if trust_result.value not in successes:
+            raise ssl.SSLError(
+                "certificate verify failed, error code: %d" %
+                trust_result.value
+            )
+
+    def handshake(self,
+                  server_hostname,
+                  verify,
+                  trust_bundle,
+                  min_version,
+                  max_version,
+                  client_cert,
+                  client_key,
+                  client_key_passphrase):
+        """
+        Actually performs the TLS handshake. This is run automatically by
+        wrapped socket, and shouldn't be needed in user code.
+        """
+        # First, we do the initial bits of connection setup. We need to create
+        # a context, set its I/O funcs, and set the connection reference.
+        self.context = Security.SSLCreateContext(
+            None, SecurityConst.kSSLClientSide, SecurityConst.kSSLStreamType
+        )
+        result = Security.SSLSetIOFuncs(
+            self.context, _read_callback_pointer, _write_callback_pointer
+        )
+        _assert_no_error(result)
+
+        # Here we need to compute the handle to use. We do this by taking the
+        # id of self modulo 2**31 - 1. If this is already in the dictionary, we
+        # just keep incrementing by one until we find a free space.
+        with _connection_ref_lock:
+            handle = id(self) % 2147483647
+            while handle in _connection_refs:
+                handle = (handle + 1) % 2147483647
+            _connection_refs[handle] = self
+
+        result = Security.SSLSetConnection(self.context, handle)
+        _assert_no_error(result)
+
+        # If we have a server hostname, we should set that too.
+        if server_hostname:
+            if not isinstance(server_hostname, bytes):
+                server_hostname = server_hostname.encode('utf-8')
+
+            result = Security.SSLSetPeerDomainName(
+                self.context, server_hostname, len(server_hostname)
+            )
+            _assert_no_error(result)
+
+        # Setup the ciphers.
+        self._set_ciphers()
+
+        # Set the minimum and maximum TLS versions.
+        result = Security.SSLSetProtocolVersionMin(self.context, min_version)
+        _assert_no_error(result)
+        result = Security.SSLSetProtocolVersionMax(self.context, max_version)
+        _assert_no_error(result)
+
+        # If there's a trust DB, we need to use it. We do that by telling
+        # SecureTransport to break on server auth. We also do that if we don't
+        # want to validate the certs at all: we just won't actually do any
+        # authing in that case.
+        if not verify or trust_bundle is not None:
+            result = Security.SSLSetSessionOption(
+                self.context,
+                SecurityConst.kSSLSessionOptionBreakOnServerAuth,
+                True
+            )
+            _assert_no_error(result)
+
+        # If there's a client cert, we need to use it.
+        if client_cert:
+            self._keychain, self._keychain_dir = _temporary_keychain()
+            self._client_cert_chain = _load_client_cert_chain(
+                self._keychain, client_cert, client_key
+            )
+            result = Security.SSLSetCertificate(
+                self.context, self._client_cert_chain
+            )
+            _assert_no_error(result)
+
+        while True:
+            with self._raise_on_error():
+                result = Security.SSLHandshake(self.context)
+
+                if result == SecurityConst.errSSLWouldBlock:
+                    raise socket.timeout("handshake timed out")
+                elif result == SecurityConst.errSSLServerAuthCompleted:
+                    self._custom_validate(verify, trust_bundle)
+                    continue
+                else:
+                    _assert_no_error(result)
+                    break
+
+    def fileno(self):
+        return self.socket.fileno()
+
+    # Copy-pasted from Python 3.5 source code
+    def _decref_socketios(self):
+        if self._makefile_refs > 0:
+            self._makefile_refs -= 1
+        if self._closed:
+            self.close()
+
+    def recv(self, bufsiz):
+        buffer = ctypes.create_string_buffer(bufsiz)
+        bytes_read = self.recv_into(buffer, bufsiz)
+        data = buffer[:bytes_read]
+        return data
+
+    def recv_into(self, buffer, nbytes=None):
+        # Read short on EOF.
+        if self._closed:
+            return 0
+
+        if nbytes is None:
+            nbytes = len(buffer)
+
+        buffer = (ctypes.c_char * nbytes).from_buffer(buffer)
+        processed_bytes = ctypes.c_size_t(0)
+
+        with self._raise_on_error():
+            result = Security.SSLRead(
+                self.context, buffer, nbytes, ctypes.byref(processed_bytes)
+            )
+
+        # There are some result codes that we want to treat as "not always
+        # errors". Specifically, those are errSSLWouldBlock,
+        # errSSLClosedGraceful, and errSSLClosedNoNotify.
+        if (result == SecurityConst.errSSLWouldBlock):
+            # If we didn't process any bytes, then this was just a time out.
+            # However, we can get errSSLWouldBlock in situations when we *did*
+            # read some data, and in those cases we should just read "short"
+            # and return.
+            if processed_bytes.value == 0:
+                # Timed out, no data read.
+                raise socket.timeout("recv timed out")
+        elif result in (SecurityConst.errSSLClosedGraceful, SecurityConst.errSSLClosedNoNotify):
+            # The remote peer has closed this connection. We should do so as
+            # well. Note that we don't actually return here because in
+            # principle this could actually be fired along with return data.
+            # It's unlikely though.
+            self.close()
+        else:
+            _assert_no_error(result)
+
+        # Ok, we read and probably succeeded. We should return whatever data
+        # was actually read.
+        return processed_bytes.value
+
+    def settimeout(self, timeout):
+        self._timeout = timeout
+
+    def gettimeout(self):
+        return self._timeout
+
+    def send(self, data):
+        processed_bytes = ctypes.c_size_t(0)
+
+        with self._raise_on_error():
+            result = Security.SSLWrite(
+                self.context, data, len(data), ctypes.byref(processed_bytes)
+            )
+
+        if result == SecurityConst.errSSLWouldBlock and processed_bytes.value == 0:
+            # Timed out
+            raise socket.timeout("send timed out")
+        else:
+            _assert_no_error(result)
+
+        # We sent, and probably succeeded. Tell them how much we sent.
+        return processed_bytes.value
+
+    def sendall(self, data):
+        total_sent = 0
+        while total_sent < len(data):
+            sent = self.send(data[total_sent:total_sent + SSL_WRITE_BLOCKSIZE])
+            total_sent += sent
+
+    def shutdown(self):
+        with self._raise_on_error():
+            Security.SSLClose(self.context)
+
+    def close(self):
+        # TODO: should I do clean shutdown here? Do I have to?
+        if self._makefile_refs < 1:
+            self._closed = True
+            if self.context:
+                CoreFoundation.CFRelease(self.context)
+                self.context = None
+            if self._client_cert_chain:
+                CoreFoundation.CFRelease(self._client_cert_chain)
+                self._client_cert_chain = None
+            if self._keychain:
+                Security.SecKeychainDelete(self._keychain)
+                CoreFoundation.CFRelease(self._keychain)
+                shutil.rmtree(self._keychain_dir)
+                self._keychain = self._keychain_dir = None
+            return self.socket.close()
+        else:
+            self._makefile_refs -= 1
+
+    def getpeercert(self, binary_form=False):
+        # Urgh, annoying.
+        #
+        # Here's how we do this:
+        #
+        # 1. Call SSLCopyPeerTrust to get hold of the trust object for this
+        #    connection.
+        # 2. Call SecTrustGetCertificateAtIndex for index 0 to get the leaf.
+        # 3. To get the CN, call SecCertificateCopyCommonName and process that
+        #    string so that it's of the appropriate type.
+        # 4. To get the SAN, we need to do something a bit more complex:
+        #    a. Call SecCertificateCopyValues to get the data, requesting
+        #       kSecOIDSubjectAltName.
+        #    b. Mess about with this dictionary to try to get the SANs out.
+        #
+        # This is gross. Really gross. It's going to be a few hundred LoC extra
+        # just to repeat something that SecureTransport can *already do*. So my
+        # operating assumption at this time is that what we want to do is
+        # instead to just flag to urllib3 that it shouldn't do its own hostname
+        # validation when using SecureTransport.
+        if not binary_form:
+            raise ValueError(
+                "SecureTransport only supports dumping binary certs"
+            )
+        trust = Security.SecTrustRef()
+        certdata = None
+        der_bytes = None
+
+        try:
+            # Grab the trust store.
+            result = Security.SSLCopyPeerTrust(
+                self.context, ctypes.byref(trust)
+            )
+            _assert_no_error(result)
+            if not trust:
+                # Probably we haven't done the handshake yet. No biggie.
+                return None
+
+            cert_count = Security.SecTrustGetCertificateCount(trust)
+            if not cert_count:
+                # Also a case that might happen if we haven't handshaked.
+                # Handshook? Handshaken?
+                return None
+
+            leaf = Security.SecTrustGetCertificateAtIndex(trust, 0)
+            assert leaf
+
+            # Ok, now we want the DER bytes.
+            certdata = Security.SecCertificateCopyData(leaf)
+            assert certdata
+
+            data_length = CoreFoundation.CFDataGetLength(certdata)
+            data_buffer = CoreFoundation.CFDataGetBytePtr(certdata)
+            der_bytes = ctypes.string_at(data_buffer, data_length)
+        finally:
+            if certdata:
+                CoreFoundation.CFRelease(certdata)
+            if trust:
+                CoreFoundation.CFRelease(trust)
+
+        return der_bytes
+
+    def _reuse(self):
+        self._makefile_refs += 1
+
+    def _drop(self):
+        if self._makefile_refs < 1:
+            self.close()
+        else:
+            self._makefile_refs -= 1
+
+
+if _fileobject:  # Platform-specific: Python 2
+    def makefile(self, mode, bufsize=-1):
+        self._makefile_refs += 1
+        return _fileobject(self, mode, bufsize, close=True)
+else:  # Platform-specific: Python 3
+    def makefile(self, mode="r", buffering=None, *args, **kwargs):
+        # We disable buffering with SecureTransport because it conflicts with
+        # the buffering that ST does internally (see issue #1153 for more).
+        buffering = 0
+        return backport_makefile(self, mode, buffering, *args, **kwargs)
+
+WrappedSocket.makefile = makefile
+
+
+class SecureTransportContext(object):
+    """
+    I am a wrapper class for the SecureTransport library, to translate the
+    interface of the standard library ``SSLContext`` object to calls into
+    SecureTransport.
+    """
+    def __init__(self, protocol):
+        self._min_version, self._max_version = _protocol_to_min_max[protocol]
+        self._options = 0
+        self._verify = False
+        self._trust_bundle = None
+        self._client_cert = None
+        self._client_key = None
+        self._client_key_passphrase = None
+
+    @property
+    def check_hostname(self):
+        """
+        SecureTransport cannot have its hostname checking disabled. For more,
+        see the comment on getpeercert() in this file.
+        """
+        return True
+
+    @check_hostname.setter
+    def check_hostname(self, value):
+        """
+        SecureTransport cannot have its hostname checking disabled. For more,
+        see the comment on getpeercert() in this file.
+        """
+        pass
+
+    @property
+    def options(self):
+        # TODO: Well, crap.
+        #
+        # So this is the bit of the code that is the most likely to cause us
+        # trouble. Essentially we need to enumerate all of the SSL options that
+        # users might want to use and try to see if we can sensibly translate
+        # them, or whether we should just ignore them.
+        return self._options
+
+    @options.setter
+    def options(self, value):
+        # TODO: Update in line with above.
+        self._options = value
+
+    @property
+    def verify_mode(self):
+        return ssl.CERT_REQUIRED if self._verify else ssl.CERT_NONE
+
+    @verify_mode.setter
+    def verify_mode(self, value):
+        self._verify = True if value == ssl.CERT_REQUIRED else False
+
+    def set_default_verify_paths(self):
+        # So, this has to do something a bit weird. Specifically, what it does
+        # is nothing.
+        #
+        # This means that, if we had previously had load_verify_locations
+        # called, this does not undo that. We need to do that because it turns
+        # out that the rest of the urllib3 code will attempt to load the
+        # default verify paths if it hasn't been told about any paths, even if
+        # the context itself was sometime earlier. We resolve that by just
+        # ignoring it.
+        pass
+
+    def load_default_certs(self):
+        return self.set_default_verify_paths()
+
+    def set_ciphers(self, ciphers):
+        # For now, we just require the default cipher string.
+        if ciphers != util.ssl_.DEFAULT_CIPHERS:
+            raise ValueError(
+                "SecureTransport doesn't support custom cipher strings"
+            )
+
+    def load_verify_locations(self, cafile=None, capath=None, cadata=None):
+        # OK, we only really support cadata and cafile.
+        if capath is not None:
+            raise ValueError(
+                "SecureTransport does not support cert directories"
+            )
+
+        self._trust_bundle = cafile or cadata
+
+    def load_cert_chain(self, certfile, keyfile=None, password=None):
+        self._client_cert = certfile
+        self._client_key = keyfile
+        self._client_cert_passphrase = password
+
+    def wrap_socket(self, sock, server_side=False,
+                    do_handshake_on_connect=True, suppress_ragged_eofs=True,
+                    server_hostname=None):
+        # So, what do we do here? Firstly, we assert some properties. This is a
+        # stripped down shim, so there is some functionality we don't support.
+        # See PEP 543 for the real deal.
+        assert not server_side
+        assert do_handshake_on_connect
+        assert suppress_ragged_eofs
+
+        # Ok, we're good to go. Now we want to create the wrapped socket object
+        # and store it in the appropriate place.
+        wrapped_socket = WrappedSocket(sock)
+
+        # Now we can handshake
+        wrapped_socket.handshake(
+            server_hostname, self._verify, self._trust_bundle,
+            self._min_version, self._max_version, self._client_cert,
+            self._client_key, self._client_key_passphrase
+        )
+        return wrapped_socket
diff --git a/python/urllib3/contrib/socks.py b/python/urllib3/contrib/socks.py
new file mode 100644
index 0000000..811e312
--- /dev/null
+++ b/python/urllib3/contrib/socks.py
@@ -0,0 +1,192 @@
+# -*- coding: utf-8 -*-
+"""
+This module contains provisional support for SOCKS proxies from within
+urllib3. This module supports SOCKS4 (specifically the SOCKS4A variant) and
+SOCKS5. To enable its functionality, either install PySocks or install this
+module with the ``socks`` extra.
+
+The SOCKS implementation supports the full range of urllib3 features. It also
+supports the following SOCKS features:
+
+- SOCKS4
+- SOCKS4a
+- SOCKS5
+- Usernames and passwords for the SOCKS proxy
+
+Known Limitations:
+
+- Currently PySocks does not support contacting remote websites via literal
+  IPv6 addresses. Any such connection attempt will fail. You must use a domain
+  name.
+- Currently PySocks does not support IPv6 connections to the SOCKS proxy. Any
+  such connection attempt will fail.
+"""
+from __future__ import absolute_import
+
+try:
+    import socks
+except ImportError:
+    import warnings
+    from ..exceptions import DependencyWarning
+
+    warnings.warn((
+        'SOCKS support in urllib3 requires the installation of optional '
+        'dependencies: specifically, PySocks.  For more information, see '
+        'https://urllib3.readthedocs.io/en/latest/contrib.html#socks-proxies'
+        ),
+        DependencyWarning
+    )
+    raise
+
+from socket import error as SocketError, timeout as SocketTimeout
+
+from ..connection import (
+    HTTPConnection, HTTPSConnection
+)
+from ..connectionpool import (
+    HTTPConnectionPool, HTTPSConnectionPool
+)
+from ..exceptions import ConnectTimeoutError, NewConnectionError
+from ..poolmanager import PoolManager
+from ..util.url import parse_url
+
+try:
+    import ssl
+except ImportError:
+    ssl = None
+
+
+class SOCKSConnection(HTTPConnection):
+    """
+    A plain-text HTTP connection that connects via a SOCKS proxy.
+    """
+    def __init__(self, *args, **kwargs):
+        self._socks_options = kwargs.pop('_socks_options')
+        super(SOCKSConnection, self).__init__(*args, **kwargs)
+
+    def _new_conn(self):
+        """
+        Establish a new connection via the SOCKS proxy.
+        """
+        extra_kw = {}
+        if self.source_address:
+            extra_kw['source_address'] = self.source_address
+
+        if self.socket_options:
+            extra_kw['socket_options'] = self.socket_options
+
+        try:
+            conn = socks.create_connection(
+                (self.host, self.port),
+                proxy_type=self._socks_options['socks_version'],
+                proxy_addr=self._socks_options['proxy_host'],
+                proxy_port=self._socks_options['proxy_port'],
+                proxy_username=self._socks_options['username'],
+                proxy_password=self._socks_options['password'],
+                proxy_rdns=self._socks_options['rdns'],
+                timeout=self.timeout,
+                **extra_kw
+            )
+
+        except SocketTimeout as e:
+            raise ConnectTimeoutError(
+                self, "Connection to %s timed out. (connect timeout=%s)" %
+                (self.host, self.timeout))
+
+        except socks.ProxyError as e:
+            # This is fragile as hell, but it seems to be the only way to raise
+            # useful errors here.
+            if e.socket_err:
+                error = e.socket_err
+                if isinstance(error, SocketTimeout):
+                    raise ConnectTimeoutError(
+                        self,
+                        "Connection to %s timed out. (connect timeout=%s)" %
+                        (self.host, self.timeout)
+                    )
+                else:
+                    raise NewConnectionError(
+                        self,
+                        "Failed to establish a new connection: %s" % error
+                    )
+            else:
+                raise NewConnectionError(
+                    self,
+                    "Failed to establish a new connection: %s" % e
+                )
+
+        except SocketError as e:  # Defensive: PySocks should catch all these.
+            raise NewConnectionError(
+                self, "Failed to establish a new connection: %s" % e)
+
+        return conn
+
+
+# We don't need to duplicate the Verified/Unverified distinction from
+# urllib3/connection.py here because the HTTPSConnection will already have been
+# correctly set to either the Verified or Unverified form by that module. This
+# means the SOCKSHTTPSConnection will automatically be the correct type.
+class SOCKSHTTPSConnection(SOCKSConnection, HTTPSConnection):
+    pass
+
+
+class SOCKSHTTPConnectionPool(HTTPConnectionPool):
+    ConnectionCls = SOCKSConnection
+
+
+class SOCKSHTTPSConnectionPool(HTTPSConnectionPool):
+    ConnectionCls = SOCKSHTTPSConnection
+
+
+class SOCKSProxyManager(PoolManager):
+    """
+    A version of the urllib3 ProxyManager that routes connections via the
+    defined SOCKS proxy.
+    """
+    pool_classes_by_scheme = {
+        'http': SOCKSHTTPConnectionPool,
+        'https': SOCKSHTTPSConnectionPool,
+    }
+
+    def __init__(self, proxy_url, username=None, password=None,
+                 num_pools=10, headers=None, **connection_pool_kw):
+        parsed = parse_url(proxy_url)
+
+        if username is None and password is None and parsed.auth is not None:
+            split = parsed.auth.split(':')
+            if len(split) == 2:
+                username, password = split
+        if parsed.scheme == 'socks5':
+            socks_version = socks.PROXY_TYPE_SOCKS5
+            rdns = False
+        elif parsed.scheme == 'socks5h':
+            socks_version = socks.PROXY_TYPE_SOCKS5
+            rdns = True
+        elif parsed.scheme == 'socks4':
+            socks_version = socks.PROXY_TYPE_SOCKS4
+            rdns = False
+        elif parsed.scheme == 'socks4a':
+            socks_version = socks.PROXY_TYPE_SOCKS4
+            rdns = True
+        else:
+            raise ValueError(
+                "Unable to determine SOCKS version from %s" % proxy_url
+            )
+
+        self.proxy_url = proxy_url
+
+        socks_options = {
+            'socks_version': socks_version,
+            'proxy_host': parsed.host,
+            'proxy_port': parsed.port,
+            'username': username,
+            'password': password,
+            'rdns': rdns
+        }
+        connection_pool_kw['_socks_options'] = socks_options
+
+        super(SOCKSProxyManager, self).__init__(
+            num_pools, headers, **connection_pool_kw
+        )
+
+        self.pool_classes_by_scheme = SOCKSProxyManager.pool_classes_by_scheme