Imported Upstream version 1.11

14 files changed, 508 insertions, 143 deletions

diff --git a/urllib3/__init__.py b/urllib3/__init__.py
index f48ac4a..747d09a 100644
--- a/urllib3/__init__.py
+++ b/urllib3/__init__.py
@@ -4,7 +4,7 @@ urllib3 - Thread-safe connection pooling and re-using.
 
 __author__ = 'Andrey Petrov (andrey.petrov@shazow.net)'
 __license__ = 'MIT'
-__version__ = '1.10.4'
+__version__ = '1.11'
 
 
 from .connectionpool import (
@@ -58,6 +58,8 @@ del NullHandler
 import warnings
 # SecurityWarning's always go off by default.
 warnings.simplefilter('always', exceptions.SecurityWarning, append=True)
+# SubjectAltNameWarning's should go off once per host
+warnings.simplefilter('default', exceptions.SubjectAltNameWarning)
 # InsecurePlatformWarning's don't vary between requests, so we keep it default.
 warnings.simplefilter('default', exceptions.InsecurePlatformWarning,
                       append=True)
diff --git a/urllib3/_collections.py b/urllib3/_collections.py
index 279416c..b68b9a5 100644
--- a/urllib3/_collections.py
+++ b/urllib3/_collections.py
@@ -97,14 +97,7 @@ class RecentlyUsedContainer(MutableMapping):
             return list(iterkeys(self._container))
 
 
-_dict_setitem = dict.__setitem__
-_dict_getitem = dict.__getitem__
-_dict_delitem = dict.__delitem__
-_dict_contains = dict.__contains__
-_dict_setdefault = dict.setdefault
-
-
-class HTTPHeaderDict(dict):
+class HTTPHeaderDict(MutableMapping):
     """
     :param headers:
         An iterable of field-value pairs. Must not contain multiple field names
@@ -139,7 +132,8 @@ class HTTPHeaderDict(dict):
     """
 
     def __init__(self, headers=None, **kwargs):
-        dict.__init__(self)
+        super(HTTPHeaderDict, self).__init__()
+        self._container = {}
         if headers is not None:
             if isinstance(headers, HTTPHeaderDict):
                 self._copy_from(headers)
@@ -149,38 +143,44 @@ class HTTPHeaderDict(dict):
             self.extend(kwargs)
 
     def __setitem__(self, key, val):
-        return _dict_setitem(self, key.lower(), (key, val))
+        self._container[key.lower()] = (key, val)
+        return self._container[key.lower()]
 
     def __getitem__(self, key):
-        val = _dict_getitem(self, key.lower())
+        val = self._container[key.lower()]
         return ', '.join(val[1:])
 
     def __delitem__(self, key):
-        return _dict_delitem(self, key.lower())
+        del self._container[key.lower()]
 
     def __contains__(self, key):
-        return _dict_contains(self, key.lower())
+        return key.lower() in self._container
 
     def __eq__(self, other):
         if not isinstance(other, Mapping) and not hasattr(other, 'keys'):
             return False
         if not isinstance(other, type(self)):
             other = type(self)(other)
-        return dict((k1, self[k1]) for k1 in self) == dict((k2, other[k2]) for k2 in other)
+        return (dict((k.lower(), v) for k, v in self.itermerged()) ==
+                dict((k.lower(), v) for k, v in other.itermerged()))
 
     def __ne__(self, other):
         return not self.__eq__(other)
 
-    values = MutableMapping.values
-    get = MutableMapping.get
-    update = MutableMapping.update
-    
     if not PY3: # Python 2
         iterkeys = MutableMapping.iterkeys
         itervalues = MutableMapping.itervalues
 
     __marker = object()
 
+    def __len__(self):
+        return len(self._container)
+
+    def __iter__(self):
+        # Only provide the originally cased names
+        for vals in self._container.values():
+            yield vals[0]
+
     def pop(self, key, default=__marker):
         '''D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
           If key is not found, d is returned if given, otherwise KeyError is raised.
@@ -216,7 +216,7 @@ class HTTPHeaderDict(dict):
         key_lower = key.lower()
         new_vals = key, val
         # Keep the common case aka no item present as fast as possible
-        vals = _dict_setdefault(self, key_lower, new_vals)
+        vals = self._container.setdefault(key_lower, new_vals)
         if new_vals is not vals:
             # new_vals was not inserted, as there was a previous one
             if isinstance(vals, list):
@@ -225,7 +225,7 @@ class HTTPHeaderDict(dict):
             else:
                 # vals should be a tuple then, i.e. only one item so far
                 # Need to convert the tuple to list for further extension
-                _dict_setitem(self, key_lower, [vals[0], vals[1], val])
+                self._container[key_lower] = [vals[0], vals[1], val]
 
     def extend(self, *args, **kwargs):
         """Generic import function for any type of header-like object.
@@ -236,7 +236,7 @@ class HTTPHeaderDict(dict):
             raise TypeError("extend() takes at most 1 positional "
                             "arguments ({} given)".format(len(args)))
         other = args[0] if len(args) >= 1 else ()
-        
+
         if isinstance(other, HTTPHeaderDict):
             for key, val in other.iteritems():
                 self.add(key, val)
@@ -257,7 +257,7 @@ class HTTPHeaderDict(dict):
         """Returns a list of all the values for the named field. Returns an
         empty list if the key doesn't exist."""
         try:
-            vals = _dict_getitem(self, key.lower())
+            vals = self._container[key.lower()]
         except KeyError:
             return []
         else:
@@ -276,11 +276,11 @@ class HTTPHeaderDict(dict):
 
     def _copy_from(self, other):
         for key in other:
-            val = _dict_getitem(other, key)
+            val = other.getlist(key)
             if isinstance(val, list):
                 # Don't need to convert tuples
                 val = list(val)
-            _dict_setitem(self, key, val)
+            self._container[key.lower()] = [key] + val
 
     def copy(self):
         clone = type(self)()
@@ -290,14 +290,14 @@ class HTTPHeaderDict(dict):
     def iteritems(self):
         """Iterate over all header lines, including duplicate ones."""
         for key in self:
-            vals = _dict_getitem(self, key)
+            vals = self._container[key.lower()]
             for val in vals[1:]:
                 yield vals[0], val
 
     def itermerged(self):
         """Iterate over all headers, merging duplicate ones together."""
         for key in self:
-            val = _dict_getitem(self, key)
+            val = self._container[key.lower()]
             yield val[0], ', '.join(val[1:])
 
     def items(self):
@@ -307,16 +307,16 @@ class HTTPHeaderDict(dict):
     def from_httplib(cls, message): # Python 2
         """Read headers from a Python 2 httplib message object."""
         # python2.7 does not expose a proper API for exporting multiheaders
-        # efficiently. This function re-reads raw lines from the message 
+        # efficiently. This function re-reads raw lines from the message
         # object and extracts the multiheaders properly.
         headers = []
-         
+
         for line in message.headers:
             if line.startswith((' ', '\t')):
                 key, value = headers[-1]
                 headers[-1] = (key, value + '\r\n' + line.rstrip())
                 continue
-    
+
             key, value = line.split(':', 1)
             headers.append((key, value.strip()))
 
diff --git a/urllib3/connection.py b/urllib3/connection.py
index 2a8c359..f64dd1a 100644
--- a/urllib3/connection.py
+++ b/urllib3/connection.py
@@ -38,7 +38,7 @@ except NameError:  # Python 2:
 from .exceptions import (
     ConnectTimeoutError,
     SystemTimeWarning,
-    SecurityWarning,
+    SubjectAltNameWarning,
 )
 from .packages.ssl_match_hostname import match_hostname
 
@@ -192,6 +192,9 @@ class VerifiedHTTPSConnection(HTTPSConnection):
                  cert_reqs=None, ca_certs=None,
                  assert_hostname=None, assert_fingerprint=None):
 
+        if ca_certs and cert_reqs is None:
+            cert_reqs = 'CERT_REQUIRED'
+
         self.key_file = key_file
         self.cert_file = cert_file
         self.cert_reqs = cert_reqs
@@ -245,10 +248,11 @@ class VerifiedHTTPSConnection(HTTPSConnection):
             cert = self.sock.getpeercert()
             if not cert.get('subjectAltName', ()):
                 warnings.warn((
-                    'Certificate has no `subjectAltName`, falling back to check for a `commonName` for now. '
-                    'This feature is being removed by major browsers and deprecated by RFC 2818. '
-                    '(See https://github.com/shazow/urllib3/issues/497 for details.)'),
-                    SecurityWarning
+                    'Certificate for {0} has no `subjectAltName`, falling back to check for a '
+                    '`commonName` for now. This feature is being removed by major browsers and '
+                    'deprecated by RFC 2818. (See https://github.com/shazow/urllib3/issues/497 '
+                    'for details.)'.format(hostname)),
+                    SubjectAltNameWarning
                 )
             match_hostname(cert, self.assert_hostname or hostname)
 
diff --git a/urllib3/connectionpool.py b/urllib3/connectionpool.py
index 117269a..c958725 100644
--- a/urllib3/connectionpool.py
+++ b/urllib3/connectionpool.py
@@ -17,6 +17,7 @@ from .exceptions import (
     ClosedPoolError,
     ProtocolError,
     EmptyPoolError,
+    HeaderParsingError,
     HostChangedError,
     LocationValueError,
     MaxRetryError,
@@ -38,9 +39,10 @@ from .request import RequestMethods
 from .response import HTTPResponse
 
 from .util.connection import is_connection_dropped
+from .util.response import assert_header_parsing
 from .util.retry import Retry
 from .util.timeout import Timeout
-from .util.url import get_host
+from .util.url import get_host, Url
 
 
 xrange = six.moves.xrange
@@ -120,7 +122,7 @@ class HTTPConnectionPool(ConnectionPool, RequestMethods):
 
     :param maxsize:
         Number of connections to save that can be reused. More than 1 is useful
-        in multithreaded situations. If ``block`` is set to false, more
+        in multithreaded situations. If ``block`` is set to False, more
         connections will be created but they will not be saved once they've
         been used.
 
@@ -381,8 +383,19 @@ class HTTPConnectionPool(ConnectionPool, RequestMethods):
         log.debug("\"%s %s %s\" %s %s" % (method, url, http_version,
                                           httplib_response.status,
                                           httplib_response.length))
+
+        try:
+            assert_header_parsing(httplib_response.msg)
+        except HeaderParsingError as hpe:  # Platform-specific: Python 3
+            log.warning(
+                'Failed to parse headers (url=%s): %s',
+                self._absolute_url(url), hpe, exc_info=True)
+
         return httplib_response
 
+    def _absolute_url(self, path):
+        return Url(scheme=self.scheme, host=self.host, port=self.port, path=path).url
+
     def close(self):
         """
         Close all pooled connections and disable the pool.
@@ -409,7 +422,7 @@ class HTTPConnectionPool(ConnectionPool, RequestMethods):
 
         # TODO: Add optional support for socket.gethostbyname checking.
         scheme, host, port = get_host(url)
-
+ 
         # Use explicit default port for comparison when none is given
         if self.port and not port:
             port = port_by_scheme.get(scheme)
@@ -568,25 +581,22 @@ class HTTPConnectionPool(ConnectionPool, RequestMethods):
             # Close the connection. If a connection is reused on which there
             # was a Certificate error, the next request will certainly raise
             # another Certificate error.
-            if conn:
-                conn.close()
-                conn = None
+            conn = conn and conn.close()
+            release_conn = True
             raise SSLError(e)
 
         except SSLError:
             # Treat SSLError separately from BaseSSLError to preserve
             # traceback.
-            if conn:
-                conn.close()
-                conn = None
+            conn = conn and conn.close()
+            release_conn = True
             raise
 
         except (TimeoutError, HTTPException, SocketError, ConnectionError) as e:
-            if conn:
-                # Discard the connection for these exceptions. It will be
-                # be replaced during the next _get_conn() call.
-                conn.close()
-                conn = None
+            # Discard the connection for these exceptions. It will be
+            # be replaced during the next _get_conn() call.
+            conn = conn and conn.close()
+            release_conn = True
 
             if isinstance(e, SocketError) and self.proxy:
                 e = ProxyError('Cannot connect to proxy.', e)
@@ -626,6 +636,9 @@ class HTTPConnectionPool(ConnectionPool, RequestMethods):
                 retries = retries.increment(method, url, response=response, _pool=self)
             except MaxRetryError:
                 if retries.raise_on_redirect:
+                    # Release the connection for this response, since we're not
+                    # returning it to be released manually.
+                    response.release_conn()
                     raise
                 return response
 
@@ -683,6 +696,10 @@ class HTTPSConnectionPool(HTTPConnectionPool):
         HTTPConnectionPool.__init__(self, host, port, strict, timeout, maxsize,
                                     block, headers, retries, _proxy, _proxy_headers,
                                     **conn_kw)
+
+        if ca_certs and cert_reqs is None:
+            cert_reqs = 'CERT_REQUIRED'
+
         self.key_file = key_file
         self.cert_file = cert_file
         self.cert_reqs = cert_reqs
diff --git a/urllib3/contrib/appengine.py b/urllib3/contrib/appengine.py
new file mode 100644
index 0000000..ed9d8b8
--- /dev/null
+++ b/urllib3/contrib/appengine.py
@@ -0,0 +1,222 @@
+import logging
+import os
+import warnings
+
+from ..exceptions import (
+    HTTPError,
+    HTTPWarning,
+    MaxRetryError,
+    ProtocolError,
+    TimeoutError,
+    SSLError
+)
+
+from ..packages.six import BytesIO
+from ..request import RequestMethods
+from ..response import HTTPResponse
+from ..util.timeout import Timeout
+from ..util.retry import Retry
+
+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 AppEnginePlatformError if:
+        * URLFetch is not available.
+        * If you attempt to use this on GAEv2 (Managed VMs), 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):
+        if not urlfetch:
+            raise AppEnginePlatformError(
+                "URLFetch is not available in this environment.")
+
+        if is_prod_appengine_v2():
+            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.org/en/latest/contrib.html.",
+            AppEnginePlatformWarning)
+
+        RequestMethods.__init__(self, headers)
+        self.validate_certificate = validate_certificate
+
+        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:
+            response = urlfetch.fetch(
+                url,
+                payload=body,
+                method=method,
+                headers=headers or {},
+                allow_truncated=False,
+                follow_redirects=(
+                    redirect and
+                    retries.redirect != 0 and
+                    retries.total),
+                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 e.message:
+                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 e.message:
+                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, **response_kw)
+
+        # Check for redirect response
+        if (http_response.get_redirect_location() and
+                retries.raise_on_redirect and redirect):
+            raise MaxRetryError(self, url, "too many redirects")
+
+        # Check if we should retry the HTTP response.
+        if retries.is_forced_retry(method, status_code=http_response.status):
+            retries = retries.increment(
+                method, url, response=http_response, _pool=self)
+            log.info("Forced retry: %s" % url)
+            retries.sleep()
+            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_v1():
+            # 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']
+
+        return HTTPResponse(
+            # In order for decoding to work, we must present the content as
+            # a file-like object.
+            body=BytesIO(urlfetch_resp.content),
+            headers=urlfetch_resp.headers,
+            status=urlfetch_resp.status_code,
+            **response_kw
+        )
+
+    def _get_absolute_timeout(self, timeout):
+        if timeout is Timeout.DEFAULT_TIMEOUT:
+            return 5  # 5s is the default timeout for URLFetch.
+        if isinstance(timeout, Timeout):
+            if not timeout.read is timeout.connect:
+                warnings.warn(
+                    "URLFetch does not support granular timeout settings, "
+                    "reverting to total 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
+
+
+def is_appengine():
+    return (is_local_appengine() or
+            is_prod_appengine_v1() or
+            is_prod_appengine_v2())
+
+
+def is_appengine_sandbox():
+    return is_appengine() and not is_prod_appengine_v2()
+
+
+def is_local_appengine():
+    return ('APPENGINE_RUNTIME' in os.environ and
+            'Development/' in os.environ['SERVER_SOFTWARE'])
+
+
+def is_prod_appengine_v1():
+    return ('APPENGINE_RUNTIME' in os.environ and
+            'Google App Engine/' in os.environ['SERVER_SOFTWARE'] and
+            not is_prod_appengine_v2())
+
+
+def is_prod_appengine_v2():
+    return os.environ.get('GAE_VM', False) == 'true'
diff --git a/urllib3/contrib/pyopenssl.py b/urllib3/contrib/pyopenssl.py
index b2c34a8..19c5b4e 100644
--- a/urllib3/contrib/pyopenssl.py
+++ b/urllib3/contrib/pyopenssl.py
@@ -85,6 +85,14 @@ _openssl_verify = {
 
 DEFAULT_SSL_CIPHER_LIST = util.ssl_.DEFAULT_CIPHERS
 
+# OpenSSL will only write 16K at a time
+SSL_WRITE_BLOCKSIZE = 16384
+
+try:
+    _ = memoryview
+    has_memoryview = True
+except NameError:
+    has_memoryview = False
 
 orig_util_HAS_SNI = util.HAS_SNI
 orig_connection_ssl_wrap_socket = connection.ssl_wrap_socket
@@ -204,13 +212,21 @@ class WrappedSocket(object):
                 continue
 
     def sendall(self, data):
-        while len(data):
-            sent = self._send_until_done(data)
-            data = data[sent:]
+        if has_memoryview and not isinstance(data, memoryview):
+            data = memoryview(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:
-            return self.connection.shutdown()
+            return self.connection.close()
         else:
             self._makefile_refs -= 1
 
@@ -287,7 +303,7 @@ def ssl_wrap_socket(sock, keyfile=None, certfile=None, cert_reqs=None,
                 raise timeout('select timed out')
             continue
         except OpenSSL.SSL.Error as e:
-            raise ssl.SSLError('bad handshake', e)
+            raise ssl.SSLError('bad handshake: %r' % e)
         break
 
     return WrappedSocket(cnx, sock)
diff --git a/urllib3/exceptions.py b/urllib3/exceptions.py
index 31bda1c..36ce0d1 100644
--- a/urllib3/exceptions.py
+++ b/urllib3/exceptions.py
@@ -149,6 +149,11 @@ class SecurityWarning(HTTPWarning):
     pass
 
 
+class SubjectAltNameWarning(SecurityWarning):
+    "Warned when connecting to a host with a certificate missing a SAN."
+    pass
+
+
 class InsecureRequestWarning(SecurityWarning):
     "Warned when making an unverified HTTPS request."
     pass
@@ -167,3 +172,19 @@ class InsecurePlatformWarning(SecurityWarning):
 class ResponseNotChunked(ProtocolError, ValueError):
     "Response needs to be chunked in order to read it as chunks."
     pass
+
+
+class ProxySchemeUnknown(AssertionError, ValueError):
+    "ProxyManager does not support the supplied scheme"
+    # TODO(t-8ch): Stop inheriting from AssertionError in v2.0.
+
+    def __init__(self, scheme):
+        message = "Not supported proxy scheme %s" % scheme
+        super(ProxySchemeUnknown, self).__init__(message)
+
+
+class HeaderParsingError(HTTPError):
+    "Raised by assert_header_parsing, but we convert it to a log.warning statement."
+    def __init__(self, defects, unparsed_data):
+        message = '%s, unparsed data: %r' % (defects or 'Unknown', unparsed_data)
+        super(HeaderParsingError, self).__init__(message)
diff --git a/urllib3/poolmanager.py b/urllib3/poolmanager.py
index b8d1e74..76b6a12 100644
--- a/urllib3/poolmanager.py
+++ b/urllib3/poolmanager.py
@@ -8,7 +8,7 @@ except ImportError:
 from ._collections import RecentlyUsedContainer
 from .connectionpool import HTTPConnectionPool, HTTPSConnectionPool
 from .connectionpool import port_by_scheme
-from .exceptions import LocationValueError, MaxRetryError
+from .exceptions import LocationValueError, MaxRetryError, ProxySchemeUnknown
 from .request import RequestMethods
 from .util.url import parse_url
 from .util.retry import Retry
@@ -227,8 +227,8 @@ class ProxyManager(PoolManager):
             port = port_by_scheme.get(proxy.scheme, 80)
             proxy = proxy._replace(port=port)
 
-        assert proxy.scheme in ("http", "https"), \
-            'Not supported proxy scheme %s' % proxy.scheme
+        if proxy.scheme not in ("http", "https"):
+            raise ProxySchemeUnknown(proxy.scheme)
 
         self.proxy = proxy
         self.proxy_headers = proxy_headers or {}
diff --git a/urllib3/request.py b/urllib3/request.py
index b08d6c9..a1a12bc 100644
--- a/urllib3/request.py
+++ b/urllib3/request.py
@@ -71,14 +71,22 @@ class RequestMethods(object):
                                             headers=headers,
                                             **urlopen_kw)
 
-    def request_encode_url(self, method, url, fields=None, **urlopen_kw):
+    def request_encode_url(self, method, url, fields=None, headers=None,
+                           **urlopen_kw):
         """
         Make a request using :meth:`urlopen` with the ``fields`` encoded in
         the url. This is useful for request methods like GET, HEAD, DELETE, etc.
         """
+        if headers is None:
+            headers = self.headers
+
+        extra_kw = {'headers': headers}
+        extra_kw.update(urlopen_kw)
+
         if fields:
             url += '?' + urlencode(fields)
-        return self.urlopen(method, url, **urlopen_kw)
+
+        return self.urlopen(method, url, **extra_kw)
 
     def request_encode_body(self, method, url, fields=None, headers=None,
                             encode_multipart=True, multipart_boundary=None,
diff --git a/urllib3/response.py b/urllib3/response.py
index 24140c4..15d4aac 100644
--- a/urllib3/response.py
+++ b/urllib3/response.py
@@ -2,6 +2,7 @@ try:
     import http.client as httplib
 except ImportError:
     import httplib
+from contextlib import contextmanager
 import zlib
 import io
 from socket import timeout as SocketTimeout
@@ -12,7 +13,7 @@ from .exceptions import (
 )
 from .packages.six import string_types as basestring, binary_type, PY3
 from .connection import HTTPException, BaseSSLError
-from .util.response import is_fp_closed
+from .util.response import is_fp_closed, is_response_to_head
 
 
 class DeflateDecoder(object):
@@ -202,6 +203,47 @@ class HTTPResponse(io.IOBase):
 
         return data
 
+    @contextmanager
+    def _error_catcher(self):
+        """
+        Catch low-level python exceptions, instead re-raising urllib3
+        variants, so that low-level exceptions are not leaked in the
+        high-level api.
+
+        On exit, release the connection back to the pool.
+        """
+        try:
+            try:
+                yield
+
+            except SocketTimeout:
+                # FIXME: Ideally we'd like to include the url in the ReadTimeoutError but
+                # there is yet no clean way to get at it from this context.
+                raise ReadTimeoutError(self._pool, None, 'Read timed out.')
+
+            except BaseSSLError as e:
+                # FIXME: Is there a better way to differentiate between SSLErrors?
+                if 'read operation timed out' not in str(e):  # Defensive:
+                    # This shouldn't happen but just in case we're missing an edge
+                    # case, let's avoid swallowing SSL errors.
+                    raise
+
+                raise ReadTimeoutError(self._pool, None, 'Read timed out.')
+
+            except HTTPException as e:
+                # This includes IncompleteRead.
+                raise ProtocolError('Connection broken: %r' % e, e)
+        except Exception:
+            # The response may not be closed but we're not going to use it anymore
+            # so close it now to ensure that the connection is released back to the pool.
+            if self._original_response and not self._original_response.isclosed():
+                self._original_response.close()
+
+            raise
+        finally:
+            if self._original_response and self._original_response.isclosed():
+                self.release_conn()
+
     def read(self, amt=None, decode_content=None, cache_content=False):
         """
         Similar to :meth:`httplib.HTTPResponse.read`, but with two additional
@@ -231,45 +273,28 @@ class HTTPResponse(io.IOBase):
             return
 
         flush_decoder = False
-
-        try:
-            try:
-                if amt is None:
-                    # cStringIO doesn't like amt=None
-                    data = self._fp.read()
+        data = None
+
+        with self._error_catcher():
+            if amt is None:
+                # cStringIO doesn't like amt=None
+                data = self._fp.read()
+                flush_decoder = True
+            else:
+                cache_content = False
+                data = self._fp.read(amt)
+                if amt != 0 and not data:  # Platform-specific: Buggy versions of Python.
+                    # Close the connection when no data is returned
+                    #
+                    # This is redundant to what httplib/http.client _should_
+                    # already do.  However, versions of python released before
+                    # December 15, 2012 (http://bugs.python.org/issue16298) do
+                    # not properly close the connection in all cases. There is
+                    # no harm in redundantly calling close.
+                    self._fp.close()
                     flush_decoder = True
-                else:
-                    cache_content = False
-                    data = self._fp.read(amt)
-                    if amt != 0 and not data:  # Platform-specific: Buggy versions of Python.
-                        # Close the connection when no data is returned
-                        #
-                        # This is redundant to what httplib/http.client _should_
-                        # already do.  However, versions of python released before
-                        # December 15, 2012 (http://bugs.python.org/issue16298) do
-                        # not properly close the connection in all cases. There is
-                        # no harm in redundantly calling close.
-                        self._fp.close()
-                        flush_decoder = True
-
-            except SocketTimeout:
-                # FIXME: Ideally we'd like to include the url in the ReadTimeoutError but
-                # there is yet no clean way to get at it from this context.
-                raise ReadTimeoutError(self._pool, None, 'Read timed out.')
-
-            except BaseSSLError as e:
-                # FIXME: Is there a better way to differentiate between SSLErrors?
-                if 'read operation timed out' not in str(e):  # Defensive:
-                    # This shouldn't happen but just in case we're missing an edge
-                    # case, let's avoid swallowing SSL errors.
-                    raise
-
-                raise ReadTimeoutError(self._pool, None, 'Read timed out.')
-
-            except HTTPException as e:
-                # This includes IncompleteRead.
-                raise ProtocolError('Connection broken: %r' % e, e)
 
+        if data:
             self._fp_bytes_read += len(data)
 
             data = self._decode(data, decode_content, flush_decoder)
@@ -277,11 +302,8 @@ class HTTPResponse(io.IOBase):
             if cache_content:
                 self._body = data
 
-            return data
+        return data
 
-        finally:
-            if self._original_response and self._original_response.isclosed():
-                self.release_conn()
 
     def stream(self, amt=2**16, decode_content=None):
         """
@@ -319,6 +341,7 @@ class HTTPResponse(io.IOBase):
         with ``original_response=r``.
         """
         headers = r.msg
+
         if not isinstance(headers, HTTPHeaderDict):
             if PY3: # Python 3
                 headers = HTTPHeaderDict(headers.items())
@@ -437,30 +460,29 @@ class HTTPResponse(io.IOBase):
             raise ResponseNotChunked("Response is not chunked. "
                 "Header 'transfer-encoding: chunked' is missing.")
 
-        if self._original_response and self._original_response._method.upper() == 'HEAD':
-            # Don't bother reading the body of a HEAD request.
-            # FIXME: Can we do this somehow without accessing private httplib _method?
+        # Don't bother reading the body of a HEAD request.
+        if self._original_response and is_response_to_head(self._original_response):
             self._original_response.close()
             return
 
-        while True:
-            self._update_chunk_length()
-            if self.chunk_left == 0:
-                break
-            chunk = self._handle_chunk(amt)
-            yield self._decode(chunk, decode_content=decode_content,
-                               flush_decoder=True)
-
-        # Chunk content ends with \r\n: discard it.
-        while True:
-            line = self._fp.fp.readline()
-            if not line:
-                # Some sites may not end with '\r\n'.
-                break
-            if line == b'\r\n':
-                break
-
-        # We read everything; close the "file".
-        if self._original_response:
-            self._original_response.close()
-        self.release_conn()
+        with self._error_catcher():
+            while True:
+                self._update_chunk_length()
+                if self.chunk_left == 0:
+                    break
+                chunk = self._handle_chunk(amt)
+                yield self._decode(chunk, decode_content=decode_content,
+                                   flush_decoder=True)
+
+            # Chunk content ends with \r\n: discard it.
+            while True:
+                line = self._fp.fp.readline()
+                if not line:
+                    # Some sites may not end with '\r\n'.
+                    break
+                if line == b'\r\n':
+                    break
+
+            # We read everything; close the "file".
+            if self._original_response:
+                self._original_response.close()
diff --git a/urllib3/util/connection.py b/urllib3/util/connection.py
index 859aec6..9ed5a64 100644
--- a/urllib3/util/connection.py
+++ b/urllib3/util/connection.py
@@ -60,6 +60,8 @@ def create_connection(address, timeout=socket._GLOBAL_DEFAULT_TIMEOUT,
     """
 
     host, port = address
+    if host.startswith('['):
+        host = host.strip('[]')
     err = None
     for res in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
         af, socktype, proto, canonname, sa = res
diff --git a/urllib3/util/response.py b/urllib3/util/response.py
index 45fff55..767ee15 100644
--- a/urllib3/util/response.py
+++ b/urllib3/util/response.py
@@ -1,3 +1,11 @@
+try:
+    import http.client as httplib
+except ImportError:
+    import httplib
+
+from ..exceptions import HeaderParsingError
+
+
 def is_fp_closed(obj):
     """
     Checks whether a given file-like object is closed.
@@ -20,3 +28,49 @@ def is_fp_closed(obj):
         pass
 
     raise ValueError("Unable to determine whether fp is closed.")
+
+
+def assert_header_parsing(headers):
+    """
+    Asserts whether all headers have been successfully parsed.
+    Extracts encountered errors from the result of parsing headers.
+
+    Only works on Python 3.
+
+    :param headers: Headers to verify.
+    :type headers: `httplib.HTTPMessage`.
+
+    :raises urllib3.exceptions.HeaderParsingError:
+        If parsing errors are found.
+    """
+
+    # This will fail silently if we pass in the wrong kind of parameter.
+    # To make debugging easier add an explicit check.
+    if not isinstance(headers, httplib.HTTPMessage):
+        raise TypeError('expected httplib.Message, got {}.'.format(
+            type(headers)))
+
+    defects = getattr(headers, 'defects', None)
+    get_payload = getattr(headers, 'get_payload', None)
+
+    unparsed_data = None
+    if get_payload:  # Platform-specific: Python 3.
+        unparsed_data = get_payload()
+
+    if defects or unparsed_data:
+        raise HeaderParsingError(defects=defects, unparsed_data=unparsed_data)
+
+
+def is_response_to_head(response):
+    """
+    Checks, wether a the request of a response has been a HEAD-request.
+    Handles the quirks of AppEngine.
+
+    :param conn:
+    :type conn: :class:`httplib.HTTPResponse`
+    """
+    # FIXME: Can we do this somehow without accessing private httplib _method?
+    method = response._method
+    if isinstance(method, int):  # Platform-specific: Appengine
+        return method == 3
+    return method.upper() == 'HEAD'
diff --git a/urllib3/util/retry.py b/urllib3/util/retry.py
index 7e0959d..1fb1f23 100644
--- a/urllib3/util/retry.py
+++ b/urllib3/util/retry.py
@@ -94,7 +94,7 @@ class Retry(object):
 
         seconds. If the backoff_factor is 0.1, then :func:`.sleep` will sleep
         for [0.1s, 0.2s, 0.4s, ...] between retries. It will never be longer
-        than :attr:`Retry.MAX_BACKOFF`.
+        than :attr:`Retry.BACKOFF_MAX`.
 
         By default, backoff is disabled (set to 0).
 
diff --git a/urllib3/util/ssl_.py b/urllib3/util/ssl_.py
index b846d42..311378b 100644
--- a/urllib3/util/ssl_.py
+++ b/urllib3/util/ssl_.py
@@ -8,6 +8,13 @@ SSLContext = None
 HAS_SNI = False
 create_default_context = None
 
+# Maps the length of a digest to a possible hash function producing this digest
+HASHFUNC_MAP = {
+    32: md5,
+    40: sha1,
+    64: sha256,
+}
+
 import errno
 import warnings
 
@@ -112,31 +119,21 @@ def assert_fingerprint(cert, fingerprint):
         Fingerprint as string of hexdigits, can be interspersed by colons.
     """
 
-    # Maps the length of a digest to a possible hash function producing
-    # this digest.
-    hashfunc_map = {
-        16: md5,
-        20: sha1,
-        32: sha256,
-    }
-
     fingerprint = fingerprint.replace(':', '').lower()
-    digest_length, odd = divmod(len(fingerprint), 2)
-
-    if odd or digest_length not in hashfunc_map:
-        raise SSLError('Fingerprint is of invalid length.')
+    digest_length = len(fingerprint)
+    hashfunc = HASHFUNC_MAP.get(digest_length)
+    if not hashfunc:
+        raise SSLError(
+            'Fingerprint of invalid length: {0}'.format(fingerprint))
 
     # We need encode() here for py32; works on py2 and p33.
     fingerprint_bytes = unhexlify(fingerprint.encode())
 
-    hashfunc = hashfunc_map[digest_length]
-
     cert_digest = hashfunc(cert).digest()
 
-    if not cert_digest == fingerprint_bytes:
+    if cert_digest != fingerprint_bytes:
         raise SSLError('Fingerprints did not match. Expected "{0}", got "{1}".'
-                       .format(hexlify(fingerprint_bytes),
-                               hexlify(cert_digest)))
+                       .format(fingerprint, hexlify(cert_digest)))
 
 
 def resolve_cert_reqs(candidate):