Merge tag 'upstream/1.16.0'

Upstream version 1.16.0

31 files changed, 760 insertions, 165 deletions

diff --git a/.travis.yml b/.travis.yml
index 45fb172..c2c20a6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,9 +3,9 @@ sudo: false
 python:
   - "2.6"
   - "2.7"
-  - "3.2"
   - "3.3"
   - "3.4"
+  - "3.5"
 install:
   # Self-install for setup.py-driven deps
   - pip install -e .
@@ -19,9 +19,7 @@ script:
   # Run 'docs' first since its objects.inv is referred to by 'www'.
   # Also force warnings to be errors since most of them tend to be actual
   # problems.
-  # Finally, skip them under Python 3.2 due to sphinx shenanigans
-  - "[[ $TRAVIS_PYTHON_VERSION != 3.2 ]] && invoke docs -o -W || true"
-  - "[[ $TRAVIS_PYTHON_VERSION != 3.2 ]] && invoke www -o -W || true"
+  - invoke docs -o -W www -o -W
 notifications:
   irc:
     channels: "irc.freenode.org#paramiko"
diff --git a/dev-requirements.txt b/dev-requirements.txt
index 059572c..9e4564a 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -1,11 +1,11 @@
 # Older junk
 tox>=1.4,<1.5
 # For newer tasks like building Sphinx docs.
-invoke>=0.10
-invocations>=0.9.2
+invoke>=0.11.1
+invocations>=0.11.0
 sphinx>=1.1.3
-alabaster>=0.6.1
-releases>=0.5.2
+alabaster>=0.7.5
+releases>=1.0.0
 semantic_version>=2.4,<2.5
 wheel==0.24
 twine==1.5
diff --git a/paramiko/_version.py b/paramiko/_version.py
index 25aac14..e82b866 100644
--- a/paramiko/_version.py
+++ b/paramiko/_version.py
@@ -1,2 +1,2 @@
-__version_info__ = (1, 15, 3)
+__version_info__ = (1, 16, 0)
 __version__ = '.'.join(map(str, __version_info__))
diff --git a/paramiko/_winapi.py b/paramiko/_winapi.py
index cf4d68e..9a8bded 100644
--- a/paramiko/_winapi.py
+++ b/paramiko/_winapi.py
@@ -1,23 +1,16 @@
 """
 Windows API functions implemented as ctypes functions and classes as found
-in jaraco.windows (2.10).
+in jaraco.windows (3.3).
 
 If you encounter issues with this module, please consider reporting the issues
 in jaraco.windows and asking the author to port the fixes back here.
 """
 
-import ctypes
+import sys
 import ctypes.wintypes
-from paramiko.py3compat import u
-try:
-    import builtins
-except ImportError:
-    import __builtin__ as builtins
 
-try:
-    USHORT = ctypes.wintypes.USHORT
-except AttributeError:
-    USHORT = ctypes.c_ushort
+from paramiko.py3compat import u, builtins
+
 
 ######################
 # jaraco.windows.error
@@ -29,11 +22,7 @@ def format_system_message(errno):
     """
     # first some flags used by FormatMessageW
     ALLOCATE_BUFFER = 0x100
-    ARGUMENT_ARRAY = 0x2000
-    FROM_HMODULE = 0x800
-    FROM_STRING = 0x400
     FROM_SYSTEM = 0x1000
-    IGNORE_INSERTS = 0x200
 
     # Let FormatMessageW allocate the buffer (we'll free it below)
     # Also, let it know we want a system error message.
@@ -44,7 +33,7 @@ def format_system_message(errno):
     result_buffer = ctypes.wintypes.LPWSTR()
     buffer_size = 0
     arguments = None
-    format_bytes = ctypes.windll.kernel32.FormatMessageW(
+    bytes = ctypes.windll.kernel32.FormatMessageW(
         flags,
         source,
         message_id,
@@ -52,11 +41,11 @@ def format_system_message(errno):
         ctypes.byref(result_buffer),
         buffer_size,
         arguments,
-    )
+        )
     # note the following will cause an infinite loop if GetLastError
     #  repeatedly returns an error that cannot be formatted, although
     #  this should not happen.
-    handle_nonzero_success(format_bytes)
+    handle_nonzero_success(bytes)
     message = result_buffer.value
     ctypes.windll.kernel32.LocalFree(result_buffer)
     return message
@@ -69,7 +58,11 @@ class WindowsError(builtins.WindowsError):
         if value is None:
             value = ctypes.windll.kernel32.GetLastError()
         strerror = format_system_message(value)
-        super(WindowsError, self).__init__(value, strerror)
+        if sys.version_info > (3,3):
+            args = 0, strerror, None, value
+        else:
+            args = value, strerror
+        super(WindowsError, self).__init__(*args)
 
     @property
     def message(self):
@@ -90,6 +83,27 @@ def handle_nonzero_success(result):
         raise WindowsError()
 
 
+###########################
+# jaraco.windows.api.memory
+
+GMEM_MOVEABLE = 0x2
+
+GlobalAlloc = ctypes.windll.kernel32.GlobalAlloc
+GlobalAlloc.argtypes = ctypes.wintypes.UINT, ctypes.c_ssize_t
+GlobalAlloc.restype = ctypes.wintypes.HANDLE
+
+GlobalLock = ctypes.windll.kernel32.GlobalLock
+GlobalLock.argtypes = ctypes.wintypes.HGLOBAL,
+GlobalLock.restype = ctypes.wintypes.LPVOID
+
+GlobalUnlock = ctypes.windll.kernel32.GlobalUnlock
+GlobalUnlock.argtypes = ctypes.wintypes.HGLOBAL,
+GlobalUnlock.restype = ctypes.wintypes.BOOL
+
+GlobalSize = ctypes.windll.kernel32.GlobalSize
+GlobalSize.argtypes = ctypes.wintypes.HGLOBAL,
+GlobalSize.restype = ctypes.c_size_t
+
 CreateFileMapping = ctypes.windll.kernel32.CreateFileMappingW
 CreateFileMapping.argtypes = [
     ctypes.wintypes.HANDLE,
@@ -104,6 +118,9 @@ CreateFileMapping.restype = ctypes.wintypes.HANDLE
 MapViewOfFile = ctypes.windll.kernel32.MapViewOfFile
 MapViewOfFile.restype = ctypes.wintypes.HANDLE
 
+#####################
+# jaraco.windows.mmap
+
 class MemoryMap(object):
     """
     A memory map object which can have security attributes overridden.
@@ -136,10 +153,13 @@ class MemoryMap(object):
         self.pos = pos
 
     def write(self, msg):
+        assert isinstance(msg, bytes)
         n = len(msg)
         if self.pos + n >= self.length:  # A little safety.
             raise ValueError("Refusing to write %d bytes" % n)
-        ctypes.windll.kernel32.RtlMoveMemory(self.view + self.pos, msg, n)
+        dest = self.view + self.pos
+        length = ctypes.wintypes.SIZE(n)
+        ctypes.windll.kernel32.RtlMoveMemory(dest, msg, length)
         self.pos += n
 
     def read(self, n):
@@ -147,7 +167,9 @@ class MemoryMap(object):
         Read n bytes from mapped view.
         """
         out = ctypes.create_string_buffer(n)
-        ctypes.windll.kernel32.RtlMoveMemory(out, self.view + self.pos, n)
+        source = self.view + self.pos
+        length = ctypes.wintypes.SIZE(n)
+        ctypes.windll.kernel32.RtlMoveMemory(out, source, length)
         self.pos += n
         return out.raw
 
@@ -155,8 +177,71 @@ class MemoryMap(object):
         ctypes.windll.kernel32.UnmapViewOfFile(self.view)
         ctypes.windll.kernel32.CloseHandle(self.filemap)
 
-#########################
-# jaraco.windows.security
+#############################
+# jaraco.windows.api.security
+
+# from WinNT.h
+READ_CONTROL = 0x00020000
+STANDARD_RIGHTS_REQUIRED = 0x000F0000
+STANDARD_RIGHTS_READ = READ_CONTROL
+STANDARD_RIGHTS_WRITE = READ_CONTROL
+STANDARD_RIGHTS_EXECUTE = READ_CONTROL
+STANDARD_RIGHTS_ALL = 0x001F0000
+
+# from NTSecAPI.h
+POLICY_VIEW_LOCAL_INFORMATION = 0x00000001
+POLICY_VIEW_AUDIT_INFORMATION = 0x00000002
+POLICY_GET_PRIVATE_INFORMATION = 0x00000004
+POLICY_TRUST_ADMIN = 0x00000008
+POLICY_CREATE_ACCOUNT = 0x00000010
+POLICY_CREATE_SECRET = 0x00000020
+POLICY_CREATE_PRIVILEGE = 0x00000040
+POLICY_SET_DEFAULT_QUOTA_LIMITS = 0x00000080
+POLICY_SET_AUDIT_REQUIREMENTS = 0x00000100
+POLICY_AUDIT_LOG_ADMIN = 0x00000200
+POLICY_SERVER_ADMIN = 0x00000400
+POLICY_LOOKUP_NAMES = 0x00000800
+POLICY_NOTIFICATION = 0x00001000
+
+POLICY_ALL_ACCESS = (
+    STANDARD_RIGHTS_REQUIRED |
+    POLICY_VIEW_LOCAL_INFORMATION |
+    POLICY_VIEW_AUDIT_INFORMATION |
+    POLICY_GET_PRIVATE_INFORMATION |
+    POLICY_TRUST_ADMIN |
+    POLICY_CREATE_ACCOUNT |
+    POLICY_CREATE_SECRET |
+    POLICY_CREATE_PRIVILEGE |
+    POLICY_SET_DEFAULT_QUOTA_LIMITS |
+    POLICY_SET_AUDIT_REQUIREMENTS |
+    POLICY_AUDIT_LOG_ADMIN |
+    POLICY_SERVER_ADMIN |
+    POLICY_LOOKUP_NAMES)
+
+
+POLICY_READ = (
+    STANDARD_RIGHTS_READ |
+    POLICY_VIEW_AUDIT_INFORMATION |
+    POLICY_GET_PRIVATE_INFORMATION)
+
+POLICY_WRITE = (
+    STANDARD_RIGHTS_WRITE |
+    POLICY_TRUST_ADMIN |
+    POLICY_CREATE_ACCOUNT |
+    POLICY_CREATE_SECRET |
+    POLICY_CREATE_PRIVILEGE |
+    POLICY_SET_DEFAULT_QUOTA_LIMITS |
+    POLICY_SET_AUDIT_REQUIREMENTS |
+    POLICY_AUDIT_LOG_ADMIN |
+    POLICY_SERVER_ADMIN)
+
+POLICY_EXECUTE = (
+    STANDARD_RIGHTS_EXECUTE |
+    POLICY_VIEW_LOCAL_INFORMATION |
+    POLICY_LOOKUP_NAMES)
+
+class TokenAccess:
+    TOKEN_QUERY = 0x8
 
 class TokenInformationClass:
     TokenUser = 1
@@ -182,7 +267,7 @@ class SECURITY_DESCRIPTOR(ctypes.Structure):
         PACL Dacl;
         }   SECURITY_DESCRIPTOR;
     """
-    SECURITY_DESCRIPTOR_CONTROL = USHORT
+    SECURITY_DESCRIPTOR_CONTROL = ctypes.wintypes.USHORT
     REVISION = 1
 
     _fields_ = [
@@ -222,6 +307,9 @@ class SECURITY_ATTRIBUTES(ctypes.Structure):
         self._descriptor = value
         self.lpSecurityDescriptor = ctypes.addressof(value)
 
+#########################
+# jaraco.windows.security
+
 def GetTokenInformation(token, information_class):
     """
     Given a token, get the token information for it.
@@ -236,9 +324,6 @@ def GetTokenInformation(token, information_class):
         ctypes.byref(data_size)))
     return ctypes.cast(data, ctypes.POINTER(TOKEN_USER)).contents
 
-class TokenAccess:
-    TOKEN_QUERY = 0x8
-
 def OpenProcessToken(proc_handle, access):
     result = ctypes.wintypes.HANDLE()
     proc_handle = ctypes.wintypes.HANDLE(proc_handle)
diff --git a/paramiko/buffered_pipe.py b/paramiko/buffered_pipe.py
index ac35b3e..d5fe164 100644
--- a/paramiko/buffered_pipe.py
+++ b/paramiko/buffered_pipe.py
@@ -81,7 +81,7 @@ class BufferedPipe (object):
         Feed new data into this pipe.  This method is assumed to be called
         from a separate thread, so synchronization is done.
         
-        :param data: the data to add, as a `str`
+        :param data: the data to add, as a `str` or `bytes`
         """
         self._lock.acquire()
         try:
@@ -125,7 +125,7 @@ class BufferedPipe (object):
         :param int nbytes: maximum number of bytes to read
         :param float timeout:
             maximum seconds to wait (or ``None``, the default, to wait forever)
-        :return: the read data, as a `str`
+        :return: the read data, as a `bytes`
         
         :raises PipeTimeout:
             if a timeout was specified and no data was ready before that
diff --git a/paramiko/channel.py b/paramiko/channel.py
index 7e39a15..057b417 100644
--- a/paramiko/channel.py
+++ b/paramiko/channel.py
@@ -587,7 +587,7 @@ class Channel (ClosingContextManager):
         is returned, the channel stream has closed.
 
         :param int nbytes: maximum number of bytes to read.
-        :return: received data, as a `str`
+        :return: received data, as a `bytes`
 
         :raises socket.timeout:
             if no data is ready before the timeout set by `settimeout`.
@@ -975,7 +975,7 @@ class Channel (ClosingContextManager):
             else:
                 ok = server.check_channel_env_request(self, name, value)
         elif key == 'exec':
-            cmd = m.get_text()
+            cmd = m.get_string()
             if server is None:
                 ok = False
             else:
diff --git a/paramiko/client.py b/paramiko/client.py
index 9ee3028..8d899a1 100644
--- a/paramiko/client.py
+++ b/paramiko/client.py
@@ -25,6 +25,7 @@ import getpass
 import os
 import socket
 import warnings
+from errno import ECONNREFUSED, EHOSTUNREACH
 
 from paramiko.agent import Agent
 from paramiko.common import DEBUG
@@ -35,7 +36,9 @@ from paramiko.hostkeys import HostKeys
 from paramiko.py3compat import string_types
 from paramiko.resource import ResourceManager
 from paramiko.rsakey import RSAKey
-from paramiko.ssh_exception import SSHException, BadHostKeyException
+from paramiko.ssh_exception import (
+    SSHException, BadHostKeyException, NoValidConnectionsError
+)
 from paramiko.transport import Transport
 from paramiko.util import retry_on_signal, ClosingContextManager
 
@@ -172,10 +175,46 @@ class SSHClient (ClosingContextManager):
         """
         self._policy = policy
 
-    def connect(self, hostname, port=SSH_PORT, username=None, password=None, pkey=None,
-                key_filename=None, timeout=None, allow_agent=True, look_for_keys=True,
-                compress=False, sock=None, gss_auth=False, gss_kex=False,
-                gss_deleg_creds=True, gss_host=None, banner_timeout=None):
+    def _families_and_addresses(self, hostname, port):
+        """
+        Yield pairs of address families and addresses to try for connecting.
+
+        :param str hostname: the server to connect to
+        :param int port: the server port to connect to
+        :returns: Yields an iterable of ``(family, address)`` tuples
+        """
+        guess = True
+        addrinfos = socket.getaddrinfo(hostname, port, socket.AF_UNSPEC, socket.SOCK_STREAM)
+        for (family, socktype, proto, canonname, sockaddr) in addrinfos:
+            if socktype == socket.SOCK_STREAM:
+                yield family, sockaddr
+                guess = False
+
+        # some OS like AIX don't indicate SOCK_STREAM support, so just guess. :(
+        # We only do this if we did not get a single result marked as socktype == SOCK_STREAM.
+        if guess:
+            for family, _, _, _, sockaddr in addrinfos:
+                yield family, sockaddr
+
+    def connect(
+        self,
+        hostname,
+        port=SSH_PORT,
+        username=None,
+        password=None,
+        pkey=None,
+        key_filename=None,
+        timeout=None,
+        allow_agent=True,
+        look_for_keys=True,
+        compress=False,
+        sock=None,
+        gss_auth=False,
+        gss_kex=False,
+        gss_deleg_creds=True,
+        gss_host=None,
+        banner_timeout=None
+    ):
         """
         Connect to an SSH server and authenticate to it.  The server's host key
         is checked against the system host keys (see `load_system_host_keys`)
@@ -206,8 +245,10 @@ class SSHClient (ClosingContextManager):
         :param str key_filename:
             the filename, or list of filenames, of optional private key(s) to
             try for authentication
-        :param float timeout: an optional timeout (in seconds) for the TCP connect
-        :param bool allow_agent: set to False to disable connecting to the SSH agent
+        :param float timeout:
+            an optional timeout (in seconds) for the TCP connect
+        :param bool allow_agent:
+            set to False to disable connecting to the SSH agent
         :param bool look_for_keys:
             set to False to disable searching for discoverable private key
             files in ``~/.ssh/``
@@ -215,10 +256,13 @@ class SSHClient (ClosingContextManager):
         :param socket sock:
             an open socket or socket-like object (such as a `.Channel`) to use
             for communication to the target host
-        :param bool gss_auth: ``True`` if you want to use GSS-API authentication
-        :param bool gss_kex: Perform GSS-API Key Exchange and user authentication
+        :param bool gss_auth:
+            ``True`` if you want to use GSS-API authentication
+        :param bool gss_kex:
+            Perform GSS-API Key Exchange and user authentication
         :param bool gss_deleg_creds: Delegate GSS-API client credentials or not
-        :param str gss_host: The targets name in the kerberos database. default: hostname
+        :param str gss_host:
+            The targets name in the kerberos database. default: hostname
         :param float banner_timeout: an optional timeout (in seconds) to wait
             for the SSH banner to be presented.
 
@@ -234,21 +278,37 @@ class SSHClient (ClosingContextManager):
             ``gss_deleg_creds`` and ``gss_host`` arguments.
         """
         if not sock:
-            for (family, socktype, proto, canonname, sockaddr) in socket.getaddrinfo(hostname, port, socket.AF_UNSPEC, socket.SOCK_STREAM):
-                if socktype == socket.SOCK_STREAM:
-                    af = family
-                    addr = sockaddr
-                    break
-            else:
-                # some OS like AIX don't indicate SOCK_STREAM support, so just guess. :(
-                af, _, _, _, addr = socket.getaddrinfo(hostname, port, socket.AF_UNSPEC, socket.SOCK_STREAM)
-            sock = socket.socket(af, socket.SOCK_STREAM)
-            if timeout is not None:
+            errors = {}
+            # Try multiple possible address families (e.g. IPv4 vs IPv6)
+            to_try = list(self._families_and_addresses(hostname, port))
+            for af, addr in to_try:
                 try:
-                    sock.settimeout(timeout)
-                except:
-                    pass
-            retry_on_signal(lambda: sock.connect(addr))
+                    sock = socket.socket(af, socket.SOCK_STREAM)
+                    if timeout is not None:
+                        try:
+                            sock.settimeout(timeout)
+                        except:
+                            pass
+                    retry_on_signal(lambda: sock.connect(addr))
+                    # Break out of the loop on success
+                    break
+                except socket.error as e:
+                    # Raise anything that isn't a straight up connection error
+                    # (such as a resolution error)
+                    if e.errno not in (ECONNREFUSED, EHOSTUNREACH):
+                        raise
+                    # Capture anything else so we know how the run looks once
+                    # iteration is complete. Retain info about which attempt
+                    # this was.
+                    errors[addr] = e
+
+            # Make sure we explode usefully if no address family attempts
+            # succeeded. We've no way of knowing which error is the "right"
+            # one, so we construct a hybrid exception containing all the real
+            # ones, of a subclass that client code should still be watching for
+            # (socket.error)
+            if len(errors) == len(to_try):
+                raise NoValidConnectionsError(errors)
 
         t = self._transport = Transport(sock, gss_kex=gss_kex, gss_deleg_creds=gss_deleg_creds)
         t.use_compression(compress=compress)
@@ -404,7 +464,8 @@ class SSHClient (ClosingContextManager):
         """
         saved_exception = None
         two_factor = False
-        allowed_types = []
+        allowed_types = set()
+        two_factor_types = set(['keyboard-interactive','password'])
 
         # If GSS-API support and GSS-PI Key Exchange was performed, we attempt
         # authentication with gssapi-keyex.
@@ -430,8 +491,8 @@ class SSHClient (ClosingContextManager):
         if pkey is not None:
             try:
                 self._log(DEBUG, 'Trying SSH key %s' % hexlify(pkey.get_fingerprint()))
-                allowed_types = self._transport.auth_publickey(username, pkey)
-                two_factor = (allowed_types == ['password'])
+                allowed_types = set(self._transport.auth_publickey(username, pkey))
+                two_factor = (allowed_types & two_factor_types)
                 if not two_factor:
                     return
             except SSHException as e:
@@ -443,8 +504,8 @@ class SSHClient (ClosingContextManager):
                     try:
                         key = pkey_class.from_private_key_file(key_filename, password)
                         self._log(DEBUG, 'Trying key %s from %s' % (hexlify(key.get_fingerprint()), key_filename))
-                        self._transport.auth_publickey(username, key)
-                        two_factor = (allowed_types == ['password'])
+                        allowed_types = set(self._transport.auth_publickey(username, key))
+                        two_factor = (allowed_types & two_factor_types)
                         if not two_factor:
                             return
                         break
@@ -458,9 +519,9 @@ class SSHClient (ClosingContextManager):
             for key in self._agent.get_keys():
                 try:
                     self._log(DEBUG, 'Trying SSH agent key %s' % hexlify(key.get_fingerprint()))
-                    # for 2-factor auth a successfully auth'd key will result in ['password']
-                    allowed_types = self._transport.auth_publickey(username, key)
-                    two_factor = (allowed_types == ['password'])
+                    # for 2-factor auth a successfully auth'd key password will return an allowed 2fac auth method
+                    allowed_types = set(self._transport.auth_publickey(username, key))
+                    two_factor = (allowed_types & two_factor_types)
                     if not two_factor:
                         return
                     break
@@ -497,8 +558,8 @@ class SSHClient (ClosingContextManager):
                     key = pkey_class.from_private_key_file(filename, password)
                     self._log(DEBUG, 'Trying discovered key %s in %s' % (hexlify(key.get_fingerprint()), filename))
                     # for 2-factor auth a successfully auth'd key will result in ['password']
-                    allowed_types = self._transport.auth_publickey(username, key)
-                    two_factor = (allowed_types == ['password'])
+                    allowed_types = set(self._transport.auth_publickey(username, key))
+                    two_factor = (allowed_types & two_factor_types)
                     if not two_factor:
                         return
                     break
@@ -512,7 +573,11 @@ class SSHClient (ClosingContextManager):
             except SSHException as e:
                 saved_exception = e
         elif two_factor:
-            raise SSHException('Two-factor authentication requires a password')
+            try:
+                self._transport.auth_interactive_dumb(username)
+                return
+            except SSHException as e:
+                saved_exception = e
 
         # if we got an auth-failed exception earlier, re-raise it
         if saved_exception is not None:
diff --git a/paramiko/config.py b/paramiko/config.py
index 233a87d..0b1345f 100644
--- a/paramiko/config.py
+++ b/paramiko/config.py
@@ -53,7 +53,7 @@ class SSHConfig (object):
         """
         Read an OpenSSH config from the given file object.
 
-        :param file file_obj: a file-like object to read the config file from
+        :param file_obj: a file-like object to read the config file from
         """
         host = {"host": ['*'], "config": {}}
         for line in file_obj:
@@ -98,7 +98,7 @@ class SSHConfig (object):
 
         The host-matching rules of OpenSSH's ``ssh_config`` man page are used:
         For each parameter, the first obtained value will be used.  The
-        configuration files contain sections separated by ``Host''
+        configuration files contain sections separated by ``Host``
         specifications, and that section is only applied for hosts that match
         one of the patterns given in the specification.
 
diff --git a/paramiko/hostkeys.py b/paramiko/hostkeys.py
index c7e1f72..38ac866 100644
--- a/paramiko/hostkeys.py
+++ b/paramiko/hostkeys.py
@@ -93,7 +93,7 @@ class HostKeys (MutableMapping):
         :raises IOError: if there was an error reading the file
         """
         with open(filename, 'r') as f:
-            for lineno, line in enumerate(f):
+            for lineno, line in enumerate(f, 1):
                 line = line.strip()
                 if (len(line) == 0) or (line[0] == '#'):
                     continue
diff --git a/paramiko/kex_gex.py b/paramiko/kex_gex.py
index cb548f3..c980b69 100644
--- a/paramiko/kex_gex.py
+++ b/paramiko/kex_gex.py
@@ -23,7 +23,7 @@ client side, and a **lot** more on the server side.
 """
 
 import os
-from hashlib import sha1
+from hashlib import sha1, sha256
 
 from paramiko import util
 from paramiko.common import DEBUG
@@ -44,6 +44,7 @@ class KexGex (object):
     min_bits = 1024
     max_bits = 8192
     preferred_bits = 2048
+    hash_algo = sha1
 
     def __init__(self, transport):
         self.transport = transport
@@ -87,7 +88,7 @@ class KexGex (object):
             return self._parse_kexdh_gex_reply(m)
         elif ptype == _MSG_KEXDH_GEX_REQUEST_OLD:
             return self._parse_kexdh_gex_request_old(m)
-        raise SSHException('KexGex asked to handle packet type %d' % ptype)
+        raise SSHException('KexGex %s asked to handle packet type %d' % self.name, ptype)
 
     ###  internals...
 
@@ -204,7 +205,7 @@ class KexGex (object):
         hm.add_mpint(self.e)
         hm.add_mpint(self.f)
         hm.add_mpint(K)
-        H = sha1(hm.asbytes()).digest()
+        H = self.hash_algo(hm.asbytes()).digest()
         self.transport._set_K_H(K, H)
         # sign it
         sig = self.transport.get_server_key().sign_ssh_data(H)
@@ -239,6 +240,10 @@ class KexGex (object):
         hm.add_mpint(self.e)
         hm.add_mpint(self.f)
         hm.add_mpint(K)
-        self.transport._set_K_H(K, sha1(hm.asbytes()).digest())
+        self.transport._set_K_H(K, self.hash_algo(hm.asbytes()).digest())
         self.transport._verify_key(host_key, sig)
         self.transport._activate_outbound()
+
+class KexGexSHA256(KexGex):
+    name = 'diffie-hellman-group-exchange-sha256'
+    hash_algo = sha256
diff --git a/paramiko/kex_group1.py b/paramiko/kex_group1.py
index a88f00d..9eee066 100644
--- a/paramiko/kex_group1.py
+++ b/paramiko/kex_group1.py
@@ -45,6 +45,7 @@ class KexGroup1(object):
     G = 2
 
     name = 'diffie-hellman-group1-sha1'
+    hash_algo = sha1
 
     def __init__(self, transport):
         self.transport = transport
diff --git a/paramiko/kex_group14.py b/paramiko/kex_group14.py
index a914aea..9f7dd21 100644
--- a/paramiko/kex_group14.py
+++ b/paramiko/kex_group14.py
@@ -22,6 +22,7 @@ Standard SSH key exchange ("kex" if you wanna sound cool).  Diffie-Hellman of
 """
 
 from paramiko.kex_group1 import KexGroup1
+from hashlib import sha1
 
 
 class KexGroup14(KexGroup1):
@@ -31,3 +32,4 @@ class KexGroup14(KexGroup1):
     G = 2
 
     name = 'diffie-hellman-group14-sha1'
+    hash_algo = sha1
diff --git a/paramiko/packet.py b/paramiko/packet.py
index b922000..2be2bb2 100644
--- a/paramiko/packet.py
+++ b/paramiko/packet.py
@@ -389,7 +389,8 @@ class Packetizer (object):
         if self.__dump_packets:
             self._log(DEBUG, util.format_binary(header, 'IN: '))
         packet_size = struct.unpack('>I', header[:4])[0]
-        # leftover contains decrypted bytes from the first block (after the length field)
+        # leftover contains decrypted bytes from the first block (after the
+        # length field)
         leftover = header[4:]
         if (packet_size - len(leftover)) % self.__block_size_in != 0:
             raise SSHException('Invalid packet blocking')
diff --git a/paramiko/pkey.py b/paramiko/pkey.py
index 1b4af01..e95d60b 100644
--- a/paramiko/pkey.py
+++ b/paramiko/pkey.py
@@ -171,8 +171,9 @@ class PKey (object):
         is useless on the abstract PKey class.
 
         :param str filename: name of the file to read
-        :param str password: an optional password to use to decrypt the key file,
-            if it's encrypted
+        :param str password:
+            an optional password to use to decrypt the key file, if it's
+            encrypted
         :return: a new `.PKey` based on the given private key
 
         :raises IOError: if there was an error reading the file
@@ -187,18 +188,18 @@ class PKey (object):
     def from_private_key(cls, file_obj, password=None):
         """
         Create a key object by reading a private key from a file (or file-like)
-        object.  If the private key is encrypted and ``password`` is not ``None``,
-        the given password will be used to decrypt the key (otherwise
+        object.  If the private key is encrypted and ``password`` is not
+        ``None``, the given password will be used to decrypt the key (otherwise
         `.PasswordRequiredException` is thrown).
 
-        :param file file_obj: the file to read from
+        :param file_obj: the file-like object to read from
         :param str password:
             an optional password to use to decrypt the key, if it's encrypted
         :return: a new `.PKey` based on the given private key
 
         :raises IOError: if there was an error reading the key
-        :raises PasswordRequiredException: if the private key file is encrypted,
-            and ``password`` is ``None``
+        :raises PasswordRequiredException:
+            if the private key file is encrypted, and ``password`` is ``None``
         :raises SSHException: if the key file is invalid
         """
         key = cls(file_obj=file_obj, password=password)
@@ -223,7 +224,7 @@ class PKey (object):
         Write private key contents into a file (or file-like) object.  If the
         password is not ``None``, the key is encrypted before writing.
 
-        :param file file_obj: the file object to write into
+        :param file_obj: the file-like object to write into
         :param str password: an optional password to use to encrypt the key
 
         :raises IOError: if there was an error writing to the file
@@ -273,7 +274,7 @@ class PKey (object):
             start += 1
         # find end
         end = start
-        while (lines[end].strip() != '-----END ' + tag + ' PRIVATE KEY-----') and (end < len(lines)):
+        while end < len(lines) and lines[end].strip() != '-----END ' + tag + ' PRIVATE KEY-----':
             end += 1
         # if we trudged to the end of the file, just try to cope.
         try:
@@ -309,8 +310,9 @@ class PKey (object):
         a trivially-encoded format (base64) which is completely insecure.  If
         a password is given, DES-EDE3-CBC is used.
 
-        :param str tag: ``"RSA"`` or ``"DSA"``, the tag used to mark the data block.
-        :param file filename: name of the file to write.
+        :param str tag:
+            ``"RSA"`` or ``"DSA"``, the tag used to mark the data block.
+        :param filename: name of the file to write.
         :param str data: data blob that makes up the private key.
         :param str password: an optional password to use to encrypt the file.
 
diff --git a/paramiko/py3compat.py b/paramiko/py3compat.py
index 57c096b..6fafc31 100644
--- a/paramiko/py3compat.py
+++ b/paramiko/py3compat.py
@@ -3,7 +3,7 @@ import base64
 
 __all__ = ['PY2', 'string_types', 'integer_types', 'text_type', 'bytes_types', 'bytes', 'long', 'input',
            'decodebytes', 'encodebytes', 'bytestring', 'byte_ord', 'byte_chr', 'byte_mask',
-           'b', 'u', 'b2s', 'StringIO', 'BytesIO', 'is_callable', 'MAXSIZE', 'next']
+           'b', 'u', 'b2s', 'StringIO', 'BytesIO', 'is_callable', 'MAXSIZE', 'next', 'builtins']
 
 PY2 = sys.version_info[0] < 3
 
@@ -18,6 +18,8 @@ if PY2:
     decodebytes = base64.decodestring
     encodebytes = base64.encodestring
 
+    import __builtin__ as builtins
+
 
     def bytestring(s):  # NOQA
         if isinstance(s, unicode):
@@ -102,6 +104,7 @@ if PY2:
 else:
     import collections
     import struct
+    import builtins
     string_types = str
     text_type = str
     bytes = bytes
diff --git a/paramiko/sftp_attr.py b/paramiko/sftp_attr.py
index cf48f65..0eaca30 100644
--- a/paramiko/sftp_attr.py
+++ b/paramiko/sftp_attr.py
@@ -209,12 +209,15 @@ class SFTPAttributes (object):
         # not all servers support uid/gid
         uid = self.st_uid
         gid = self.st_gid
+        size = self.st_size
         if uid is None:
             uid = 0
         if gid is None:
             gid = 0
+        if size is None:
+            size = 0
 
-        return '%s   1 %-8d %-8d %8d %-12s %s' % (ks, uid, gid, self.st_size, datestr, filename)
+        return '%s   1 %-8d %-8d %8d %-12s %s' % (ks, uid, gid, size, datestr, filename)
 
     def asbytes(self):
         return b(str(self))
diff --git a/paramiko/sftp_client.py b/paramiko/sftp_client.py
index 89840ea..5722555 100644
--- a/paramiko/sftp_client.py
+++ b/paramiko/sftp_client.py
@@ -589,6 +589,7 @@ class SFTPClient(BaseSFTP, ClosingContextManager):
 
         .. versionadded:: 1.4
         """
+        # TODO: make class initialize with self._cwd set to self.normalize('.')
         return self._cwd and u(self._cwd)
 
     def putfo(self, fl, remotepath, file_size=0, callback=None, confirm=True):
@@ -599,7 +600,7 @@ class SFTPClient(BaseSFTP, ClosingContextManager):
 
         The SFTP operations use pipelining for speed.
 
-        :param file fl: opened file or file-like object to copy
+        :param fl: opened file or file-like object to copy
         :param str remotepath: the destination path on the SFTP server
         :param int file_size:
             optional size parameter passed to callback. If none is specified,
@@ -685,9 +686,10 @@ class SFTPClient(BaseSFTP, ClosingContextManager):
 
         .. versionadded:: 1.10
         """
+        file_size = self.stat(remotepath).st_size
         with self.open(remotepath, 'rb') as fr:
-            file_size = self.stat(remotepath).st_size
-            fr.prefetch()
+            fr.prefetch(file_size)
+
             size = 0
             while True:
                 data = fr.read(32768)
@@ -715,7 +717,6 @@ class SFTPClient(BaseSFTP, ClosingContextManager):
         .. versionchanged:: 1.7.4
             Added the ``callback`` param
         """
-        file_size = self.stat(remotepath).st_size
         with open(localpath, 'wb') as fl:
             size = self.getfo(remotepath, fl, callback)
         s = os.stat(localpath)
diff --git a/paramiko/sftp_file.py b/paramiko/sftp_file.py
index d0a37da..c5b6548 100644
--- a/paramiko/sftp_file.py
+++ b/paramiko/sftp_file.py
@@ -379,7 +379,7 @@ class SFTPFile (BufferedFile):
         """
         self.pipelined = pipelined
     
-    def prefetch(self):
+    def prefetch(self, file_size):
         """
         Pre-fetch the remaining contents of this file in anticipation of future
         `.read` calls.  If reading the entire file, pre-fetching can
@@ -393,12 +393,11 @@ class SFTPFile (BufferedFile):
 
         .. versionadded:: 1.5.1
         """
-        size = self.stat().st_size
         # queue up async reads for the rest of the file
         chunks = []
         n = self._realpos
-        while n < size:
-            chunk = min(self.MAX_REQUEST_SIZE, size - n)
+        while n < file_size:
+            chunk = min(self.MAX_REQUEST_SIZE, file_size - n)
             chunks.append((n, chunk))
             n += chunk
         if len(chunks) > 0:
diff --git a/paramiko/ssh_exception.py b/paramiko/ssh_exception.py
index e120a45..02f3e52 100644
--- a/paramiko/ssh_exception.py
+++ b/paramiko/ssh_exception.py
@@ -16,6 +16,8 @@
 # along with Paramiko; if not, write to the Free Software Foundation, Inc.,
 # 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
 
+import socket
+
 
 class SSHException (Exception):
     """
@@ -133,3 +135,39 @@ class ProxyCommandFailure (SSHException):
         self.error = error
         # for unpickling
         self.args = (command, error, )
+
+
+class NoValidConnectionsError(socket.error):
+    """
+    Multiple connection attempts were made and no families succeeded.
+
+    This exception class wraps multiple "real" underlying connection errors,
+    all of which represent failed connection attempts. Because these errors are
+    not guaranteed to all be of the same error type (i.e. different errno,
+    `socket.error` subclass, message, etc) we expose a single unified error
+    message and a ``None`` errno so that instances of this class match most
+    normal handling of `socket.error` objects.
+    
+    To see the wrapped exception objects, access the ``errors`` attribute.
+    ``errors`` is a dict whose keys are address tuples (e.g. ``('127.0.0.1',
+    22)``) and whose values are the exception encountered trying to connect to
+    that address.
+
+    It is implied/assumed that all the errors given to a single instance of
+    this class are from connecting to the same hostname + port (and thus that
+    the differences are in the resolution of the hostname - e.g. IPv4 vs v6).
+    """
+    def __init__(self, errors):
+        """
+        :param dict errors:
+            The errors dict to store, as described by class docstring.
+        """
+        addrs = errors.keys()
+        body = ', '.join([x[0] for x in addrs[:-1]])
+        tail = addrs[-1][0]
+        msg = "Unable to connect to port {0} on {1} or {2}"
+        super(NoValidConnectionsError, self).__init__(
+            None, # stand-in for errno
+            msg.format(addrs[0][1], body, tail)
+        )
+        self.errors = errors
diff --git a/paramiko/transport.py b/paramiko/transport.py
index 31c27a2..18fb103 100644
--- a/paramiko/transport.py
+++ b/paramiko/transport.py
@@ -20,13 +20,14 @@
 Core protocol implementation
 """
 
+from __future__ import print_function
 import os
 import socket
 import sys
 import threading
 import time
 import weakref
-from hashlib import md5, sha1
+from hashlib import md5, sha1, sha256, sha512
 
 import paramiko
 from paramiko import util
@@ -47,7 +48,7 @@ from paramiko.common import xffffffff, cMSG_CHANNEL_OPEN, cMSG_IGNORE, \
     MAX_WINDOW_SIZE, DEFAULT_WINDOW_SIZE, DEFAULT_MAX_PACKET_SIZE
 from paramiko.compress import ZlibCompressor, ZlibDecompressor
 from paramiko.dsskey import DSSKey
-from paramiko.kex_gex import KexGex
+from paramiko.kex_gex import KexGex, KexGexSHA256
 from paramiko.kex_group1 import KexGroup1
 from paramiko.kex_group14 import KexGroup14
 from paramiko.kex_gss import KexGSSGex, KexGSSGroup1, KexGSSGroup14, NullHostKey
@@ -94,27 +95,109 @@ class Transport (threading.Thread, ClosingContextManager):
     _PROTO_ID = '2.0'
     _CLIENT_ID = 'paramiko_%s' % paramiko.__version__
 
-    _preferred_ciphers = ('aes128-ctr', 'aes256-ctr', 'aes128-cbc', 'blowfish-cbc',
-                          'aes256-cbc', '3des-cbc', 'arcfour128', 'arcfour256')
-    _preferred_macs = ('hmac-sha1', 'hmac-md5', 'hmac-sha1-96', 'hmac-md5-96')
-    _preferred_keys = ('ssh-rsa', 'ssh-dss', 'ecdsa-sha2-nistp256')
-    _preferred_kex =  ( 'diffie-hellman-group14-sha1', 'diffie-hellman-group-exchange-sha1' , 'diffie-hellman-group1-sha1')
+    # These tuples of algorithm identifiers are in preference order; do not
+    # reorder without reason!
+    _preferred_ciphers = (
+        'aes128-ctr',
+        'aes192-ctr',
+        'aes256-ctr',
+        'aes128-cbc',
+        'blowfish-cbc',
+        'aes192-cbc',
+        'aes256-cbc',
+        '3des-cbc',
+        'arcfour128',
+        'arcfour256',
+    )
+    _preferred_macs = (
+        'hmac-sha2-256',
+        'hmac-sha2-512',
+        'hmac-md5',
+        'hmac-sha1-96',
+        'hmac-md5-96',
+        'hmac-sha1',
+    )
+    _preferred_keys = (
+        'ssh-rsa',
+        'ssh-dss',
+        'ecdsa-sha2-nistp256',
+    )
+    _preferred_kex =  (
+        'diffie-hellman-group1-sha1',
+        'diffie-hellman-group14-sha1',
+        'diffie-hellman-group-exchange-sha1',
+        'diffie-hellman-group-exchange-sha256',
+    )
     _preferred_compression = ('none',)
 
     _cipher_info = {
-        'aes128-ctr': {'class': AES, 'mode': AES.MODE_CTR, 'block-size': 16, 'key-size': 16},
-        'aes256-ctr': {'class': AES, 'mode': AES.MODE_CTR, 'block-size': 16, 'key-size': 32},
-        'blowfish-cbc': {'class': Blowfish, 'mode': Blowfish.MODE_CBC, 'block-size': 8, 'key-size': 16},
-        'aes128-cbc': {'class': AES, 'mode': AES.MODE_CBC, 'block-size': 16, 'key-size': 16},
-        'aes256-cbc': {'class': AES, 'mode': AES.MODE_CBC, 'block-size': 16, 'key-size': 32},
-        '3des-cbc': {'class': DES3, 'mode': DES3.MODE_CBC, 'block-size': 8, 'key-size': 24},
-        'arcfour128': {'class': ARC4, 'mode': None, 'block-size': 8, 'key-size': 16},
-        'arcfour256': {'class': ARC4, 'mode': None, 'block-size': 8, 'key-size': 32},
+        'aes128-ctr': {
+            'class': AES,
+            'mode': AES.MODE_CTR,
+            'block-size': 16,
+            'key-size': 16
+        },
+        'aes192-ctr': {
+            'class': AES,
+            'mode': AES.MODE_CTR,
+            'block-size': 16,
+            'key-size': 24
+        },
+        'aes256-ctr': {
+            'class': AES,
+            'mode': AES.MODE_CTR,
+            'block-size': 16,
+            'key-size': 32
+        },
+        'blowfish-cbc': {
+            'class': Blowfish,
+            'mode': Blowfish.MODE_CBC,
+            'block-size': 8,
+            'key-size': 16
+        },
+        'aes128-cbc': {
+            'class': AES,
+            'mode': AES.MODE_CBC,
+            'block-size': 16,
+            'key-size': 16
+        },
+        'aes192-cbc': {
+            'class': AES,
+            'mode': AES.MODE_CBC,
+            'block-size': 16,
+            'key-size': 24
+        },
+        'aes256-cbc': {
+            'class': AES,
+            'mode': AES.MODE_CBC,
+            'block-size': 16,
+            'key-size': 32
+        },
+        '3des-cbc': {
+            'class': DES3,
+            'mode': DES3.MODE_CBC,
+            'block-size': 8,
+            'key-size': 24
+        },
+        'arcfour128': {
+            'class': ARC4,
+            'mode': None,
+            'block-size': 8,
+            'key-size': 16
+        },
+        'arcfour256': {
+            'class': ARC4,
+            'mode': None,
+            'block-size': 8,
+            'key-size': 32
+        },
     }
 
     _mac_info = {
         'hmac-sha1': {'class': sha1, 'size': 20},
         'hmac-sha1-96': {'class': sha1, 'size': 12},
+        'hmac-sha2-256': {'class': sha256, 'size': 32},
+        'hmac-sha2-512': {'class': sha512, 'size': 64},
         'hmac-md5': {'class': md5, 'size': 16},
         'hmac-md5-96': {'class': md5, 'size': 12},
     }
@@ -129,6 +212,7 @@ class Transport (threading.Thread, ClosingContextManager):
         'diffie-hellman-group1-sha1': KexGroup1,
         'diffie-hellman-group14-sha1': KexGroup14,
         'diffie-hellman-group-exchange-sha1': KexGex,
+        'diffie-hellman-group-exchange-sha256': KexGexSHA256,
         'gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==': KexGSSGroup1,
         'gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==': KexGSSGroup14,
         'gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==': KexGSSGex
@@ -1294,6 +1378,27 @@ class Transport (threading.Thread, ClosingContextManager):
         self.auth_handler.auth_interactive(username, handler, my_event, submethods)
         return self.auth_handler.wait_for_response(my_event)
 
+    def auth_interactive_dumb(self, username, handler=None, submethods=''):
+        """
+        Autenticate to the server interactively but dumber.
+        Just print the prompt and / or instructions to stdout and send back
+        the response. This is good for situations where partial auth is
+        achieved by key and then the user has to enter a 2fac token.
+        """
+
+        if not handler:
+            def handler(title, instructions, prompt_list):
+                answers = []
+                if title:
+                    print(title.strip())
+                if instructions:
+                    print(instructions.strip())
+                for prompt,show_input in prompt_list:
+                    print(prompt.strip(),end=' ')
+                    answers.append(raw_input())
+                return answers
+        return self.auth_interactive(username, handler, submethods)
+
     def auth_gssapi_with_mic(self, username, gss_host, gss_deleg_creds):
         """
         Authenticate to the Server using GSS-API / SSPI.
@@ -1507,13 +1612,23 @@ class Transport (threading.Thread, ClosingContextManager):
         m.add_bytes(self.H)
         m.add_byte(b(id))
         m.add_bytes(self.session_id)
-        out = sofar = sha1(m.asbytes()).digest()
+        # Fallback to SHA1 for kex engines that fail to specify a hex
+        # algorithm, or for e.g. transport tests that don't run kexinit.
+        hash_algo = getattr(self.kex_engine, 'hash_algo', None)
+        hash_select_msg = "kex engine %s specified hash_algo %r" % (self.kex_engine.__class__.__name__, hash_algo)
+        if hash_algo is None:
+            hash_algo = sha1
+            hash_select_msg += ", falling back to sha1"
+        if not hasattr(self, '_logged_hash_selection'):
+            self._log(DEBUG, hash_select_msg)
+            setattr(self, '_logged_hash_selection', True)
+        out = sofar = hash_algo(m.asbytes()).digest()
         while len(out) < nbytes:
             m = Message()
             m.add_mpint(self.K)
             m.add_bytes(self.H)
             m.add_bytes(sofar)
-            digest = sha1(m.asbytes()).digest()
+            digest = hash_algo(m.asbytes()).digest()
             out += digest
             sofar += digest
         return out[:nbytes]
@@ -1591,10 +1706,13 @@ class Transport (threading.Thread, ClosingContextManager):
         try:
             try:
                 self.packetizer.write_all(b(self.local_version + '\r\n'))
+                self._log(DEBUG, 'Local version/idstring: %s' % self.local_version)
                 self._check_banner()
-                # The above is actually very much part of the handshake, but sometimes the banner can be read
-                # but the machine is not responding, for example when the remote ssh daemon is loaded in to memory
-                # but we can not read from the disk/spawn a new shell.
+                # The above is actually very much part of the handshake, but
+                # sometimes the banner can be read but the machine is not
+                # responding, for example when the remote ssh daemon is loaded
+                # in to memory but we can not read from the disk/spawn a new
+                # shell.
                 # Make sure we can specify a timeout for the initial handshake.
                 # Re-use the banner timeout for now.
                 self.packetizer.start_handshake(self.handshake_timeout)
@@ -1696,6 +1814,18 @@ class Transport (threading.Thread, ClosingContextManager):
             if self.sys.modules is not None:
                 raise
 
+
+    def _log_agreement(self, which, local, remote):
+        # Log useful, non-duplicative line re: an agreed-upon algorithm.
+        # Old code implied algorithms could be asymmetrical (different for
+        # inbound vs outbound) so we preserve that possibility.
+        msg = "{0} agreed: ".format(which)
+        if local == remote:
+            msg += local
+        else:
+            msg += "local={0}, remote={1}".format(local, remote)
+        self._log(DEBUG, msg)
+
     ###  protocol stages
 
     def _negotiate_keys(self, m):
@@ -1733,6 +1863,7 @@ class Transport (threading.Thread, ClosingContextManager):
             raise SSHException('Indecipherable protocol version "' + buf + '"')
         # save this server version string for later
         self.remote_version = buf
+        self._log(DEBUG, 'Remote version/idstring: %s' % buf)
         # pull off any attached comment
         comment = ''
         i = buf.find(' ')
@@ -1761,10 +1892,12 @@ class Transport (threading.Thread, ClosingContextManager):
             self.clear_to_send_lock.release()
         self.in_kex = True
         if self.server_mode:
-            if (self._modulus_pack is None) and ('diffie-hellman-group-exchange-sha1' in self._preferred_kex):
+            mp_required_prefix = 'diffie-hellman-group-exchange-sha'
+            kex_mp = [k for k in self._preferred_kex if k.startswith(mp_required_prefix)]
+            if (self._modulus_pack is None) and (len(kex_mp) > 0):
                 # can't do group-exchange if we don't have a pack of potential primes
-                pkex = list(self.get_security_options().kex)
-                pkex.remove('diffie-hellman-group-exchange-sha1')
+                pkex = [k for k in self.get_security_options().kex
+                                if not k.startswith(mp_required_prefix)]
                 self.get_security_options().kex = pkex
             available_server_keys = list(filter(list(self.server_key_dict.keys()).__contains__,
                                                 self._preferred_keys))
@@ -1816,15 +1949,24 @@ class Transport (threading.Thread, ClosingContextManager):
                   ' server lang:' + str(server_lang_list) +
                   ' kex follows?' + str(kex_follows))
 
-        # as a server, we pick the first item in the client's list that we support.
-        # as a client, we pick the first item in our list that the server supports.
+        # as a server, we pick the first item in the client's list that we
+        # support.
+        # as a client, we pick the first item in our list that the server
+        # supports.
         if self.server_mode:
-            agreed_kex = list(filter(self._preferred_kex.__contains__, kex_algo_list))
+            agreed_kex = list(filter(
+                self._preferred_kex.__contains__,
+                kex_algo_list
+            ))
         else:
-            agreed_kex = list(filter(kex_algo_list.__contains__, self._preferred_kex))
+            agreed_kex = list(filter(
+                kex_algo_list.__contains__,
+                self._preferred_kex
+            ))
         if len(agreed_kex) == 0:
             raise SSHException('Incompatible ssh peer (no acceptable kex algorithm)')
         self.kex_engine = self._kex_info[agreed_kex[0]](self)
+        self._log(DEBUG, "Kex agreed: %s" % agreed_kex[0])
 
         if self.server_mode:
             available_server_keys = list(filter(list(self.server_key_dict.keys()).__contains__,
@@ -1852,7 +1994,9 @@ class Transport (threading.Thread, ClosingContextManager):
             raise SSHException('Incompatible ssh server (no acceptable ciphers)')
         self.local_cipher = agreed_local_ciphers[0]
         self.remote_cipher = agreed_remote_ciphers[0]
-        self._log(DEBUG, 'Ciphers agreed: local=%s, remote=%s' % (self.local_cipher, self.remote_cipher))
+        self._log_agreement(
+            'Cipher', local=self.local_cipher, remote=self.remote_cipher
+        )
 
         if self.server_mode:
             agreed_remote_macs = list(filter(self._preferred_macs.__contains__, client_mac_algo_list))
@@ -1864,6 +2008,9 @@ class Transport (threading.Thread, ClosingContextManager):
             raise SSHException('Incompatible ssh server (no acceptable macs)')
         self.local_mac = agreed_local_macs[0]
         self.remote_mac = agreed_remote_macs[0]
+        self._log_agreement(
+            'MAC', local=self.local_mac, remote=self.remote_mac
+        )
 
         if self.server_mode:
             agreed_remote_compression = list(filter(self._preferred_compression.__contains__, client_compress_algo_list))
@@ -1875,10 +2022,11 @@ class Transport (threading.Thread, ClosingContextManager):
             raise SSHException('Incompatible ssh server (no acceptable compression) %r %r %r' % (agreed_local_compression, agreed_remote_compression, self._preferred_compression))
         self.local_compression = agreed_local_compression[0]
         self.remote_compression = agreed_remote_compression[0]
-
-        self._log(DEBUG, 'using kex %s; server key type %s; cipher: local %s, remote %s; mac: local %s, remote %s; compression: local %s, remote %s' %
-                  (agreed_kex[0], self.host_key_type, self.local_cipher, self.remote_cipher, self.local_mac,
-                   self.remote_mac, self.local_compression, self.remote_compression))
+        self._log_agreement(
+            'Compression',
+            local=self.local_compression,
+            remote=self.remote_compression
+        )
 
         # save for computing hash later...
         # now wait!  openssh has a bug (and others might too) where there are
@@ -1899,8 +2047,8 @@ class Transport (threading.Thread, ClosingContextManager):
         engine = self._get_cipher(self.remote_cipher, key_in, IV_in)
         mac_size = self._mac_info[self.remote_mac]['size']
         mac_engine = self._mac_info[self.remote_mac]['class']
-        # initial mac keys are done in the hash's natural size (not the potentially truncated
-        # transmission size)
+        # initial mac keys are done in the hash's natural size (not the
+        # potentially truncated transmission size)
         if self.server_mode:
             mac_key = self._compute_key('E', mac_engine().digest_size)
         else:
@@ -1926,8 +2074,8 @@ class Transport (threading.Thread, ClosingContextManager):
         engine = self._get_cipher(self.local_cipher, key_out, IV_out)
         mac_size = self._mac_info[self.local_mac]['size']
         mac_engine = self._mac_info[self.local_mac]['class']
-        # initial mac keys are done in the hash's natural size (not the potentially truncated
-        # transmission size)
+        # initial mac keys are done in the hash's natural size (not the
+        # potentially truncated transmission size)
         if self.server_mode:
             mac_key = self._compute_key('F', mac_engine().digest_size)
         else:
diff --git a/paramiko/util.py b/paramiko/util.py
index d9a29d7..855e575 100644
--- a/paramiko/util.py
+++ b/paramiko/util.py
@@ -118,7 +118,7 @@ def safe_string(s):
 
 def bit_length(n):
     try:
-        return n.bitlength()
+        return n.bit_length()
     except AttributeError:
         norm = deflate_long(n, False)
         hbyte = byte_ord(norm[0])
diff --git a/setup.py b/setup.py
index 003a061..629c28f 100644
--- a/setup.py
+++ b/setup.py
@@ -87,6 +87,7 @@ setup(
         'Programming Language :: Python :: 3.2',
         'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
+        'Programming Language :: Python :: 3.5',
     ],
     **kw
 )
diff --git a/setup_helper.py b/setup_helper.py
index ff6b0e1..9e3834b 100644
--- a/setup_helper.py
+++ b/setup_helper.py
@@ -30,9 +30,42 @@ import distutils.archive_util
 from distutils.dir_util import mkpath
 from distutils.spawn import spawn
 
-
-def make_tarball(base_name, base_dir, compress='gzip',
-                 verbose=False, dry_run=False):
+try:
+    from pwd import getpwnam
+except ImportError:
+    getpwnam = None
+
+try:
+    from grp import getgrnam
+except ImportError:
+    getgrnam = None
+
+def _get_gid(name):
+    """Returns a gid, given a group name."""
+    if getgrnam is None or name is None:
+        return None
+    try:
+        result = getgrnam(name)
+    except KeyError:
+        result = None
+    if result is not None:
+        return result[2]
+    return None
+
+def _get_uid(name):
+    """Returns an uid, given a user name."""
+    if getpwnam is None or name is None:
+        return None
+    try:
+        result = getpwnam(name)
+    except KeyError:
+        result = None
+    if result is not None:
+        return result[2]
+    return None
+
+def make_tarball(base_name, base_dir, compress='gzip', verbose=0, dry_run=0,
+                 owner=None, group=None):
     """Create a tar file from all the files under 'base_dir'.
     This file may be compressed.
 
@@ -75,11 +108,30 @@ def make_tarball(base_name, base_dir, compress='gzip',
     mkpath(os.path.dirname(archive_name), dry_run=dry_run)
     log.info('Creating tar file %s with mode %s' % (archive_name, mode))
 
+    uid = _get_uid(owner)
+    gid = _get_gid(group)
+
+    def _set_uid_gid(tarinfo):
+        if gid is not None:
+            tarinfo.gid = gid
+            tarinfo.gname = group
+        if uid is not None:
+            tarinfo.uid = uid
+            tarinfo.uname = owner
+        return tarinfo
+
     if not dry_run:
         tar = tarfile.open(archive_name, mode=mode)
         # This recursively adds everything underneath base_dir
-        tar.add(base_dir)
-        tar.close()
+        try:
+            try:
+                # Support for the `filter' parameter was added in Python 2.7,
+                # earlier versions will raise TypeError.
+                tar.add(base_dir, filter=_set_uid_gid)
+            except TypeError:
+                tar.add(base_dir)
+        finally:
+            tar.close()
 
     if compress and compress not in tarfile_compress_flag:
         spawn([compress] + compress_flags[compress] + [archive_name],
diff --git a/sites/shared_conf.py b/sites/shared_conf.py
index 4a6a5c4..99fab31 100644
--- a/sites/shared_conf.py
+++ b/sites/shared_conf.py
@@ -12,7 +12,6 @@ html_theme_options = {
     'description': "A Python implementation of SSHv2.",
     'github_user': 'paramiko',
     'github_repo': 'paramiko',
-    'gratipay_user': 'bitprophet',
     'analytics_id': 'UA-18486793-2',
     'travis_button': True,
 }
diff --git a/sites/www/changelog.rst b/sites/www/changelog.rst
index d94d5bc..084d13d 100644
--- a/sites/www/changelog.rst
+++ b/sites/www/changelog.rst
@@ -2,6 +2,56 @@
 Changelog
 =========
 
+* :release:`1.16.0 <2015-11-04>`
+* :bug:`194 major` (also :issue:`562`, :issue:`530`, :issue:`576`) Streamline
+  use of ``stat`` when downloading SFTP files via `SFTPClient.get
+  <paramiko.sftp_client.SFTPClient.get>`; this avoids triggering bugs in some
+  off-spec SFTP servers such as IBM Sterling. Thanks to ``@muraleee`` for the
+  initial report and to Torkil Gustavsen for the patch.
+* :feature:`467` (also :issue:`139`, :issue:`412`) Fully enable two-factor
+  authentication (e.g. when a server requires ``AuthenticationMethods
+  pubkey,keyboard-interactive``). Thanks to ``@perryjrandall`` for the patch
+  and to ``@nevins-b`` and Matt Robenolt for additional support.
+* :bug:`502 major` Fix 'exec' requests in server mode to use ``get_string``
+  instead of ``get_text`` to avoid ``UnicodeDecodeError`` on non-UTF-8 input.
+  Thanks to Anselm Kruis for the patch & discussion.
+* :bug:`401` Fix line number reporting in log output regarding invalid
+  ``known_hosts`` line entries. Thanks to Dylan Thacker-Smith for catch &
+  patch.
+* :support:`525 backported` Update the vendored Windows API addon to a more
+  recent edition. Also fixes :issue:`193`, :issue:`488`, :issue:`498`. Thanks
+  to Jason Coombs.
+* :release:`1.15.4 <2015-11-02>`
+* :release:`1.14.3 <2015-11-02>`
+* :release:`1.13.4 <2015-11-02>`
+* :bug:`366` Fix `~paramiko.sftp_attributes.SFTPAttributes` so its string
+  representation doesn't raise exceptions on empty/initialized instances. Patch
+  by Ulrich Petri.
+* :bug:`359` Use correct attribute name when trying to use Python 3's
+  ``int.bit_length`` method; prior to fix, the Python 2 custom fallback
+  implementation was always used, even on Python 3. Thanks to Alex Gaynor.
+* :support:`594 backported` Correct some post-Python3-port docstrings to
+  specify ``bytes`` type instead of ``str``. Credit to ``@redixin``.
+* :bug:`565` Don't explode with ``IndexError`` when reading private key files
+  lacking an ``-----END <type> PRIVATE KEY-----`` footer. Patch courtesy of
+  Prasanna Santhanam.
+* :feature:`604` Add support for the ``aes192-ctr`` and ``aes192-cbc`` ciphers.
+  Thanks to Michiel Tiller for noticing it was as easy as tweaking some key
+  sizes :D
+* :feature:`356` (also :issue:`596`, :issue:`365`, :issue:`341`, :issue:`164`,
+  :issue:`581`, and a bunch of other duplicates besides) Add support for SHA-2
+  based key exchange (kex) algorithm ``diffie-hellman-group-exchange-sha256``
+  and (H)MAC algorithms ``hmac-sha2-256`` and ``hmac-sha2-512``.
+  
+  This change includes tweaks to debug-level logging regarding
+  algorithm-selection handshakes; the old all-in-one log line is now multiple
+  easier-to-read, printed-at-handshake-time log lines.
+
+  Thanks to the many people who submitted patches for this functionality and/or
+  assisted in testing those patches. That list includes but is not limited to,
+  and in no particular order: Matthias Witte, Dag Wieers, Ash Berlin, Etienne
+  Perot, Gert van Dijk, ``@GuyShaanan``, Aaron Bieber, ``@cyphase``, and Eric
+  Brown.
 * :release:`1.15.3 <2015-10-02>`
 * :support:`554 backported` Fix inaccuracies in the docstring for the ECDSA key
   class. Thanks to Jared Hance for the patch.
@@ -29,6 +79,13 @@ Changelog
   which caused ``OverFlowError`` (and other symptoms) in SFTP functionality.
   Thanks to ``@dboreham`` for leading the troubleshooting charge, and to
   Scott Maxwell for the final patch.
+* :support:`582` Fix some old ``setup.py`` related helper code which was
+  breaking ``bdist_dumb`` on Mac OS X. Thanks to Peter Odding for the patch.
+* :bug:`22 major` Try harder to connect to multiple network families (e.g. IPv4
+  vs IPv6) in case of connection issues; this helps with problems such as hosts
+  which resolve both IPv4 and IPv6 addresses but are only listening on IPv4.
+  Thanks to Dries Desmet for original report and Torsten Landschoff for the
+  foundational patchset.
 * :bug:`402` Check to see if an SSH agent is actually present before trying to
   forward it to the remote end. This replaces what was usually a useless
   ``TypeError`` with a human-readable
@@ -57,7 +114,7 @@ Changelog
   use of the ``shlex`` module. Thanks to Yan Kalchevskiy.
 * :support:`422 backported` Clean up some unused imports. Courtesy of Olle
   Lundberg.
-* :support:`421 backported` Modernize threading calls to user newer API. Thanks
+* :support:`421 backported` Modernize threading calls to use newer API. Thanks
   to Olle Lundberg.
 * :support:`419 backported` Modernize a bunch of the codebase internals to
   leverage decorators. Props to ``@beckjake`` for realizing we're no longer on
diff --git a/tasks.py b/tasks.py
index 3d57567..3d55a77 100644
--- a/tasks.py
+++ b/tasks.py
@@ -3,17 +3,18 @@ from os.path import join
 from shutil import rmtree, copytree
 
 from invoke import Collection, ctask as task
-from invocations.docs import docs, www
+from invocations.docs import docs, www, sites
 from invocations.packaging import publish
 
 
 # Until we move to spec-based testing
 @task
-def test(ctx, coverage=False):
+def test(ctx, coverage=False, flags=""):
+    if "--verbose" not in flags.split():
+        flags += " --verbose"
     runner = "python"
     if coverage:
         runner = "coverage run --source=paramiko"
-    flags = "--verbose"
     ctx.run("{0} test.py {1}".format(runner, flags), pty=True)
 
 
@@ -30,11 +31,12 @@ def release(ctx):
     # Move the built docs into where Epydocs used to live
     target = 'docs'
     rmtree(target, ignore_errors=True)
-    copytree(docs_build, target)
+    # TODO: make it easier to yank out this config val from the docs coll
+    copytree('sites/docs/_build', target)
     # Publish
     publish(ctx)
     # Remind
     print("\n\nDon't forget to update RTD's versions page for new minor releases!")
 
 
-ns = Collection(test, coverage, release, docs, www)
+ns = Collection(test, coverage, release, docs, www, sites)
diff --git a/tests/test_client.py b/tests/test_client.py
index 3d2e75c..04cab43 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -75,7 +75,7 @@ class NullServer (paramiko.ServerInterface):
         return paramiko.OPEN_SUCCEEDED
 
     def check_channel_exec_request(self, channel, command):
-        if command != 'yes':
+        if command != b'yes':
             return False
         return True
 
diff --git a/tests/test_kex.py b/tests/test_kex.py
index 56f1b7c..19804fb 100644
--- a/tests/test_kex.py
+++ b/tests/test_kex.py
@@ -26,7 +26,7 @@ import unittest
 
 import paramiko.util
 from paramiko.kex_group1 import KexGroup1
-from paramiko.kex_gex import KexGex
+from paramiko.kex_gex import KexGex, KexGexSHA256
 from paramiko import Message
 from paramiko.common import byte_chr
 
@@ -252,3 +252,121 @@ class KexTest (unittest.TestCase):
         self.assertEqual(H, hexlify(transport._H).upper())
         self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
         self.assertTrue(transport._activated)
+
+    def test_7_gex_sha256_client(self):
+        transport = FakeTransport()
+        transport.server_mode = False
+        kex = KexGexSHA256(transport)
+        kex.start_kex()
+        x = b'22000004000000080000002000'
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_GROUP,), transport._expect)
+
+        msg = Message()
+        msg.add_mpint(FakeModulusPack.P)
+        msg.add_mpint(FakeModulusPack.G)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_GROUP, msg)
+        x = b'20000000807E2DDB1743F3487D6545F04F1C8476092FB912B013626AB5BCEB764257D88BBA64243B9F348DF7B41B8C814A995E00299913503456983FFB9178D3CD79EB6D55522418A8ABF65375872E55938AB99A84A0B5FC8A1ECC66A7C3766E7E0F80B7CE2C9225FC2DD683F4764244B72963BBB383F529DCF0C5D17740B8A2ADBE9208D4'
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_REPLY,), transport._expect)
+
+        msg = Message()
+        msg.add_string('fake-host-key')
+        msg.add_mpint(69)
+        msg.add_string('fake-sig')
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_REPLY, msg)
+        H = b'AD1A9365A67B4496F05594AD1BF656E3CDA0851289A4C1AFF549FEAE50896DF4'
+        self.assertEqual(self.K, transport._K)
+        self.assertEqual(H, hexlify(transport._H).upper())
+        self.assertEqual((b'fake-host-key', b'fake-sig'), transport._verify)
+        self.assertTrue(transport._activated)
+
+    def test_8_gex_sha256_old_client(self):
+        transport = FakeTransport()
+        transport.server_mode = False
+        kex = KexGexSHA256(transport)
+        kex.start_kex(_test_old_style=True)
+        x = b'1E00000800'
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_GROUP,), transport._expect)
+
+        msg = Message()
+        msg.add_mpint(FakeModulusPack.P)
+        msg.add_mpint(FakeModulusPack.G)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_GROUP, msg)
+        x = b'20000000807E2DDB1743F3487D6545F04F1C8476092FB912B013626AB5BCEB764257D88BBA64243B9F348DF7B41B8C814A995E00299913503456983FFB9178D3CD79EB6D55522418A8ABF65375872E55938AB99A84A0B5FC8A1ECC66A7C3766E7E0F80B7CE2C9225FC2DD683F4764244B72963BBB383F529DCF0C5D17740B8A2ADBE9208D4'
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_REPLY,), transport._expect)
+
+        msg = Message()
+        msg.add_string('fake-host-key')
+        msg.add_mpint(69)
+        msg.add_string('fake-sig')
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_REPLY, msg)
+        H = b'518386608B15891AE5237DEE08DCADDE76A0BCEFCE7F6DB3AD66BC41D256DFE5'
+        self.assertEqual(self.K, transport._K)
+        self.assertEqual(H, hexlify(transport._H).upper())
+        self.assertEqual((b'fake-host-key', b'fake-sig'), transport._verify)
+        self.assertTrue(transport._activated)
+
+    def test_9_gex_sha256_server(self):
+        transport = FakeTransport()
+        transport.server_mode = True
+        kex = KexGexSHA256(transport)
+        kex.start_kex()
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_REQUEST, paramiko.kex_gex._MSG_KEXDH_GEX_REQUEST_OLD), transport._expect)
+
+        msg = Message()
+        msg.add_int(1024)
+        msg.add_int(2048)
+        msg.add_int(4096)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_REQUEST, msg)
+        x = b'1F0000008100FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF0000000102'
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_INIT,), transport._expect)
+
+        msg = Message()
+        msg.add_mpint(12345)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_INIT, msg)
+        K = 67592995013596137876033460028393339951879041140378510871612128162185209509220726296697886624612526735888348020498716482757677848959420073720160491114319163078862905400020959196386947926388406687288901564192071077389283980347784184487280885335302632305026248574716290537036069329724382811853044654824945750581
+        H = b'CCAC0497CF0ABA1DBF55E1A3995D17F4CC31824B0E8D95CDF8A06F169D050D80'
+        x = b'210000000866616B652D6B6579000000807E2DDB1743F3487D6545F04F1C8476092FB912B013626AB5BCEB764257D88BBA64243B9F348DF7B41B8C814A995E00299913503456983FFB9178D3CD79EB6D55522418A8ABF65375872E55938AB99A84A0B5FC8A1ECC66A7C3766E7E0F80B7CE2C9225FC2DD683F4764244B72963BBB383F529DCF0C5D17740B8A2ADBE9208D40000000866616B652D736967'
+        self.assertEqual(K, transport._K)
+        self.assertEqual(H, hexlify(transport._H).upper())
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertTrue(transport._activated)
+
+    def test_10_gex_sha256_server_with_old_client(self):
+        transport = FakeTransport()
+        transport.server_mode = True
+        kex = KexGexSHA256(transport)
+        kex.start_kex()
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_REQUEST, paramiko.kex_gex._MSG_KEXDH_GEX_REQUEST_OLD), transport._expect)
+
+        msg = Message()
+        msg.add_int(2048)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_REQUEST_OLD, msg)
+        x = b'1F0000008100FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF0000000102'
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertEqual((paramiko.kex_gex._MSG_KEXDH_GEX_INIT,), transport._expect)
+
+        msg = Message()
+        msg.add_mpint(12345)
+        msg.rewind()
+        kex.parse_next(paramiko.kex_gex._MSG_KEXDH_GEX_INIT, msg)
+        K = 67592995013596137876033460028393339951879041140378510871612128162185209509220726296697886624612526735888348020498716482757677848959420073720160491114319163078862905400020959196386947926388406687288901564192071077389283980347784184487280885335302632305026248574716290537036069329724382811853044654824945750581
+        H = b'3DDD2AD840AD095E397BA4D0573972DC60F6461FD38A187CACA6615A5BC8ADBB'
+        x = b'210000000866616B652D6B6579000000807E2DDB1743F3487D6545F04F1C8476092FB912B013626AB5BCEB764257D88BBA64243B9F348DF7B41B8C814A995E00299913503456983FFB9178D3CD79EB6D55522418A8ABF65375872E55938AB99A84A0B5FC8A1ECC66A7C3766E7E0F80B7CE2C9225FC2DD683F4764244B72963BBB383F529DCF0C5D17740B8A2ADBE9208D40000000866616B652D736967'
+        self.assertEqual(K, transport._K)
+        self.assertEqual(H, hexlify(transport._H).upper())
+        self.assertEqual(x, hexlify(transport._message.asbytes()).upper())
+        self.assertTrue(transport._activated)
+
+
diff --git a/tests/test_sftp.py b/tests/test_sftp.py
index cb8f7f8..131b8ab 100755
--- a/tests/test_sftp.py
+++ b/tests/test_sftp.py
@@ -696,7 +696,8 @@ class SFTPTest (unittest.TestCase):
                 f.readv([(0, 12)])
 
             with sftp.open(FOLDER + '/zero', 'r') as f:
-                f.prefetch()
+                file_size = f.stat().st_size
+                f.prefetch(file_size)
                 f.read(100)
         finally:
             sftp.unlink(FOLDER + '/zero')
@@ -811,6 +812,11 @@ class SFTPTest (unittest.TestCase):
             sftp.remove('%s/nonutf8data' % FOLDER)
 
 
+    def test_sftp_attributes_empty_str(self):
+        sftp_attributes = SFTPAttributes()
+        self.assertEqual(str(sftp_attributes), "?---------   1 0        0               0 (unknown date) ?")
+
+
 if __name__ == '__main__':
     SFTPTest.init_loopback()
     # logging is required by test_N_file_with_percent
diff --git a/tests/test_sftp_big.py b/tests/test_sftp_big.py
index abed27b..cfad568 100644
--- a/tests/test_sftp_big.py
+++ b/tests/test_sftp_big.py
@@ -132,7 +132,8 @@ class BigSFTPTest (unittest.TestCase):
             
             start = time.time()
             with sftp.open('%s/hongry.txt' % FOLDER, 'rb') as f:
-                f.prefetch()
+                file_size = f.stat().st_size
+                f.prefetch(file_size)
 
                 # read on odd boundaries to make sure the bytes aren't getting scrambled
                 n = 0
@@ -171,7 +172,8 @@ class BigSFTPTest (unittest.TestCase):
             chunk = 793
             for i in range(10):
                 with sftp.open('%s/hongry.txt' % FOLDER, 'rb') as f:
-                    f.prefetch()
+                    file_size = f.stat().st_size
+                    f.prefetch(file_size)
                     base_offset = (512 * 1024) + 17 * random.randint(1000, 2000)
                     offsets = [base_offset + j * chunk for j in range(100)]
                     # randomly seek around and read them out
@@ -245,9 +247,11 @@ class BigSFTPTest (unittest.TestCase):
 
             for i in range(10):
                 with sftp.open('%s/hongry.txt' % FOLDER, 'r') as f:
-                    f.prefetch()
+                    file_size = f.stat().st_size
+                    f.prefetch(file_size)
             with sftp.open('%s/hongry.txt' % FOLDER, 'r') as f:
-                f.prefetch()
+                file_size = f.stat().st_size
+                f.prefetch(file_size)
                 for n in range(1024):
                     data = f.read(1024)
                     self.assertEqual(data, kblob)
@@ -275,7 +279,8 @@ class BigSFTPTest (unittest.TestCase):
             self.assertEqual(sftp.stat('%s/hongry.txt' % FOLDER).st_size, 1024 * 1024)
 
             with sftp.open('%s/hongry.txt' % FOLDER, 'rb') as f:
-                f.prefetch()
+                file_size = f.stat().st_size
+                f.prefetch(file_size)
                 data = f.read(1024)
                 self.assertEqual(data, kblob)
 
@@ -353,7 +358,8 @@ class BigSFTPTest (unittest.TestCase):
             
             # try to read it too.
             with sftp.open('%s/hongry.txt' % FOLDER, 'r', 128 * 1024) as f:
-                f.prefetch()
+                file_size = f.stat().st_size
+                f.prefetch(file_size)
                 total = 0
                 while total < 1024 * 1024:
                     total += len(f.read(32 * 1024))
diff --git a/tests/test_transport.py b/tests/test_transport.py
index 3c8ad81..a93d8b6 100644
--- a/tests/test_transport.py
+++ b/tests/test_transport.py
@@ -28,6 +28,7 @@ import socket
 import time
 import threading
 import random
+from hashlib import sha1
 import unittest
 
 from paramiko import Transport, SecurityOptions, ServerInterface, RSAKey, DSSKey, \
@@ -77,7 +78,7 @@ class NullServer (ServerInterface):
         return OPEN_SUCCEEDED
 
     def check_channel_exec_request(self, channel, command):
-        if command != 'yes':
+        if command != b'yes':
             return False
         return True
 
@@ -251,7 +252,7 @@ class TransportTest(unittest.TestCase):
         chan = self.tc.open_session()
         schan = self.ts.accept(1.0)
         try:
-            chan.exec_command('no')
+            chan.exec_command(b'command contains \xfc and is not a valid UTF-8 string')
             self.assertTrue(False)
         except SSHException:
             pass
@@ -447,9 +448,11 @@ class TransportTest(unittest.TestCase):
         bytes = self.tc.packetizer._Packetizer__sent_bytes
         chan.send('x' * 1024)
         bytes2 = self.tc.packetizer._Packetizer__sent_bytes
+        block_size = self.tc._cipher_info[self.tc.local_cipher]['block-size']
+        mac_size = self.tc._mac_info[self.tc.local_mac]['size']
         # tests show this is actually compressed to *52 bytes*!  including packet overhead!  nice!! :)
         self.assertTrue(bytes2 - bytes < 1024)
-        self.assertEqual(52, bytes2 - bytes)
+        self.assertEqual(16 + block_size + mac_size, bytes2 - bytes)
 
         chan.close()
         schan.close()