Prevent data being truncated over persistent connection socket (#43885)

* Change how data is sent to the persistent connection socket.

We can't rely on readline(), so send the size of the data first. We can
then read that many bytes from the stream on the recieving end.

* Set pty to noncanonical mode before sending

* Now that we send data length, we don't need a sentinel anymore

* Copy socket changes to persistent, too

* Use os.write instead of fdopen()ing and using that.

* Follow pickle with sha1sum of pickle

* Swap order of vars and init being passed to ansible-connection

bin/ansible-connection

@@ -12,6 +12,7 @@ except Exception:
     pass
 
 import fcntl
+import hashlib
 import os
 import signal
 import socket
@@ -36,6 +37,23 @@ from ansible.utils.display import Display
 from ansible.utils.jsonrpc import JsonRpcServer
 
 
+def read_stream(byte_stream):
+    size = int(byte_stream.readline().strip())
+
+    data = byte_stream.read(size)
+    if len(data) < size:
+        raise Exception("EOF found before data was complete")
+
+    data_hash = to_text(byte_stream.readline().strip())
+    if data_hash != hashlib.sha1(data).hexdigest():
+        raise Exception("Read {0} bytes, but data did not match checksum".format(size))
+
+    # restore escaped loose \r characters
+    data = data.replace(br'\r', b'\r')
+
+    return data
+
+
 @contextmanager
 def file_lock(lock_path):
     """
@@ -204,25 +222,8 @@ def main():
 
     try:
         # read the play context data via stdin, which means depickling it
-        cur_line = stdin.readline()
-        init_data = b''
-
-        while cur_line.strip() != b'#END_INIT#':
-            if cur_line == b'':
-                raise Exception("EOF found before init data was complete")
-            init_data += cur_line
-            cur_line = stdin.readline()
-
-        cur_line = stdin.readline()
-        vars_data = b''
-
-        while cur_line.strip() != b'#END_VARS#':
-            if cur_line == b'':
-                raise Exception("EOF found before vars data was complete")
-            vars_data += cur_line
-            cur_line = stdin.readline()
-        # restore escaped loose \r characters
-        vars_data = vars_data.replace(br'\r', b'\r')
+        vars_data = read_stream(stdin)
+        init_data = read_stream(stdin)
 
         if PY3:
             pc_data = cPickle.loads(init_data, encoding='bytes')

lib/ansible/executor/task_executor.py

@@ -10,14 +10,15 @@ import time
 import json
 import subprocess
 import sys
+import termios
 import traceback
 
 from ansible import constants as C
 from ansible.errors import AnsibleError, AnsibleParserError, AnsibleUndefinedVariable, AnsibleConnectionFailure, AnsibleActionFail, AnsibleActionSkip
 from ansible.executor.task_result import TaskResult
 from ansible.module_utils.six import iteritems, string_types, binary_type
-from ansible.module_utils.six.moves import cPickle
 from ansible.module_utils._text import to_text, to_native
+from ansible.module_utils.connection import write_to_file_descriptor
 from ansible.playbook.conditional import Conditional
 from ansible.playbook.task import Task
 from ansible.template import Templar
@@ -920,28 +921,24 @@ class TaskExecutor:
             [python, find_file_in_path('ansible-connection'), to_text(os.getppid())],
             stdin=slave, stdout=subprocess.PIPE, stderr=subprocess.PIPE
         )
-        stdin = os.fdopen(master, 'wb', 0)
         os.close(slave)
 
-        # Need to force a protocol that is compatible with both py2 and py3.
-        # That would be protocol=2 or less.
-        # Also need to force a protocol that excludes certain control chars as
-        # stdin in this case is a pty and control chars will cause problems.
-        # that means only protocol=0 will work.
-        src = cPickle.dumps(self._play_context.serialize(), protocol=0)
-        stdin.write(src)
-        stdin.write(b'\n#END_INIT#\n')
+        # We need to set the pty into noncanonical mode. This ensures that we
+        # can receive lines longer than 4095 characters (plus newline) without
+        # truncating.
+        old = termios.tcgetattr(master)
+        new = termios.tcgetattr(master)
+        new[3] = new[3] & ~termios.ICANON
 
-        src = cPickle.dumps(variables, protocol=0)
-        # remaining \r fail to round-trip the socket
-        src = src.replace(b'\r', br'\r')
-        stdin.write(src)
-        stdin.write(b'\n#END_VARS#\n')
+        try:
+            termios.tcsetattr(master, termios.TCSANOW, new)
+            write_to_file_descriptor(master, variables)
+            write_to_file_descriptor(master, self._play_context.serialize())
 
-        stdin.flush()
-
-        (stdout, stderr) = p.communicate()
-        stdin.close()
+            (stdout, stderr) = p.communicate()
+        finally:
+            termios.tcsetattr(master, termios.TCSANOW, old)
+        os.close(master)
 
         if p.returncode == 0:
             result = json.loads(to_text(stdout, errors='surrogate_then_replace'))

lib/ansible/module_utils/connection.py

@@ -27,6 +27,7 @@
 # USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 import os
+import hashlib
 import json
 import socket
 import struct
@@ -36,6 +37,30 @@ import uuid
 from functools import partial
 from ansible.module_utils._text import to_bytes, to_text
 from ansible.module_utils.six import iteritems
+from ansible.module_utils.six.moves import cPickle
+
+
+def write_to_file_descriptor(fd, obj):
+    """Handles making sure all data is properly written to file descriptor fd.
+
+    In particular, that data is encoded in a character stream-friendly way and
+    that all data gets written before returning.
+    """
+    # Need to force a protocol that is compatible with both py2 and py3.
+    # That would be protocol=2 or less.
+    # Also need to force a protocol that excludes certain control chars as
+    # stdin in this case is a pty and control chars will cause problems.
+    # that means only protocol=0 will work.
+    src = cPickle.dumps(obj, protocol=0)
+
+    # raw \r characters will not survive pty round-trip
+    # They should be rehydrated on the receiving end
+    src = src.replace(b'\r', br'\r')
+    data_hash = to_bytes(hashlib.sha1(src).hexdigest())
+
+    os.write(fd, b'%d\n' % len(src))
+    os.write(fd, src)
+    os.write(fd, b'%s\n' % data_hash)
 
 
 def send_data(s, data):

lib/ansible/plugins/connection/persistent.py

@@ -34,12 +34,12 @@ import pty
 import json
 import subprocess
 import sys
+import termios
 
 from ansible import constants as C
 from ansible.plugins.connection import ConnectionBase
 from ansible.module_utils._text import to_text
-from ansible.module_utils.six.moves import cPickle
-from ansible.module_utils.connection import Connection as SocketConnection
+from ansible.module_utils.connection import Connection as SocketConnection, write_to_file_descriptor
 from ansible.errors import AnsibleError
 
 try:
@@ -109,26 +109,24 @@ class Connection(ConnectionBase):
             [python, find_file_in_path('ansible-connection'), to_text(os.getppid())],
             stdin=slave, stdout=subprocess.PIPE, stderr=subprocess.PIPE
         )
-        stdin = os.fdopen(master, 'wb', 0)
         os.close(slave)
 
-        # Need to force a protocol that is compatible with both py2 and py3.
-        # That would be protocol=2 or less.
-        # Also need to force a protocol that excludes certain control chars as
-        # stdin in this case is a pty and control chars will cause problems.
-        # that means only protocol=0 will work.
-        src = cPickle.dumps(self._play_context.serialize(), protocol=0)
-        stdin.write(src)
-        stdin.write(b'\n#END_INIT#\n')
+        # We need to set the pty into noncanonical mode. This ensures that we
+        # can receive lines longer than 4095 characters (plus newline) without
+        # truncating.
+        old = termios.tcgetattr(master)
+        new = termios.tcgetattr(master)
+        new[3] = new[3] & ~termios.ICANON
 
-        src = cPickle.dumps({'ansible_command_timeout': self.get_option('persistent_command_timeout')}, protocol=0)
-        stdin.write(src)
-        stdin.write(b'\n#END_VARS#\n')
+        try:
+            termios.tcsetattr(master, termios.TCSANOW, new)
+            write_to_file_descriptor(master, {'ansible_command_timeout': self.get_option('persistent_command_timeout')})
+            write_to_file_descriptor(master, self._play_context.serialize())
 
-        stdin.flush()
-
-        (stdout, stderr) = p.communicate()
-        stdin.close()
+            (stdout, stderr) = p.communicate()
+        finally:
+            termios.tcsetattr(master, termios.TCSANOW, old)
+        os.close(master)
 
         if p.returncode == 0:
             result = json.loads(to_text(stdout, errors='surrogate_then_replace'))