Allow any buffer type to be sent to Channel

Fixes #968

Changes the behaviour of the underlying asbytes helper to
pass along unknown types. Most callers already handle this
by passing the bytes along to a file or socket-like object
which will raise TypeError anyway.

Adds test coverage through the Transport implementation.

Change against the 1.17 branch.

2 files changed, 79 insertions, 9 deletions

diff --git a/paramiko/common.py b/paramiko/common.py
index 556f046a..3b18858b 100644
--- a/paramiko/common.py
+++ b/paramiko/common.py
@@ -21,7 +21,7 @@ Common constants and global variables.
 """
 import logging
 from paramiko.py3compat import (
-    byte_chr, PY2, bytes_types, string_types, b, long,
+    byte_chr, PY2, bytes_types, text_type, string_types, b, long,
 )
 
 MSG_DISCONNECT, MSG_IGNORE, MSG_UNIMPLEMENTED, MSG_DEBUG, \
@@ -163,14 +163,15 @@ else:
 
 
 def asbytes(s):
-    if not isinstance(s, bytes_types):
-        if isinstance(s, string_types):
-            s = b(s)
-        else:
-            try:
-                s = s.asbytes()
-            except Exception:
-                raise Exception('Unknown type')
+    if isinstance(s, bytes_types):
+        return s
+    if isinstance(s, text_type):
+        # GZ 2017-05-25: Accept text and encode as utf-8 for compatibilty only.
+        return s.encode("utf-8")
+    asbytes = getattr(s, "asbytes", None)
+    if asbytes is not None:
+        return asbytes()
+    # May be an object that implements the buffer api, let callers decide
     return s
 
 
diff --git a/tests/test_transport.py b/tests/test_transport.py
index c426cef1..3e352919 100644
--- a/tests/test_transport.py
+++ b/tests/test_transport.py
@@ -43,6 +43,7 @@ from paramiko.common import (
 )
 from paramiko.py3compat import bytes
 from paramiko.message import Message
+from tests import skipUnlessBuiltin
 from tests.loop import LoopSocket
 from tests.util import test_path
 
@@ -858,3 +859,71 @@ class TransportTest(unittest.TestCase):
         self.assertEqual([chan], r)
         self.assertEqual([], w)
         self.assertEqual([], e)
+
+    def test_channel_send_misc(self):
+        """
+        verify behaviours sending various instances to a channel
+        """
+        self.setup_test_server()
+        text = u"\xa7 slice me nicely"
+        with self.tc.open_session() as chan:
+            schan = self.ts.accept(1.0)
+            if schan is None:
+                self.fail("Test server transport failed to accept")
+            sfile = schan.makefile()
+
+            # TypeError raised on non string or buffer type
+            self.assertRaises(TypeError, chan.send, object())
+            self.assertRaises(TypeError, chan.sendall, object())
+
+            # sendall() accepts a unicode instance
+            chan.sendall(text)
+            expected = text.encode("utf-8")
+            self.assertEqual(sfile.read(len(expected)), expected)
+
+    @skipUnlessBuiltin('buffer')
+    def test_channel_send_buffer(self):
+        """
+        verify sending buffer instances to a channel
+        """
+        self.setup_test_server()
+        data = 3 * b'some test data\n whole'
+        with self.tc.open_session() as chan:
+            schan = self.ts.accept(1.0)
+            if schan is None:
+                self.fail("Test server transport failed to accept")
+            sfile = schan.makefile()
+
+            # send() accepts buffer instances
+            sent = 0
+            while sent < len(data):
+                sent += chan.send(buffer(data, sent, 8))
+            self.assertEqual(sfile.read(len(data)), data)
+
+            # sendall() accepts a buffer instance
+            chan.sendall(buffer(data))
+            self.assertEqual(sfile.read(len(data)), data)
+
+    @skipUnlessBuiltin('memoryview')
+    def test_channel_send_memoryview(self):
+        """
+        verify sending memoryview instances to a channel
+        """
+        self.setup_test_server()
+        data = 3 * b'some test data\n whole'
+        with self.tc.open_session() as chan:
+            schan = self.ts.accept(1.0)
+            if schan is None:
+                self.fail("Test server transport failed to accept")
+            sfile = schan.makefile()
+
+            # send() accepts memoryview slices
+            sent = 0
+            view = memoryview(data)
+            while sent < len(view):
+                sent += chan.send(view[sent:sent+8])
+            self.assertEqual(sfile.read(len(data)), data)
+
+            # sendall() accepts a memoryview instance
+            chan.sendall(memoryview(data))
+            self.assertEqual(sfile.read(len(data)), data)