46 lines
1.9 KiB
Python
Executable File
46 lines
1.9 KiB
Python
Executable File
#!/usr/bin/python
|
|
# Send the command to the remote side, and then transfer stdin from local to
|
|
# remote and stdout from remote to local.
|
|
#
|
|
# The tricky part is delimiting the command from the stdin data. If we were
|
|
# implementing this from scratch, we'd probably use a null byte. However, we'd
|
|
# like to work with the existing qubes.VMShell service, whose implementation is
|
|
# simply "/bin/bash", so users don't have to maintain duplicate RPC policy. We
|
|
# take advantage of the fact that when bash is executing commands from a pipe,
|
|
# it reads one character at a time until it gets a newline that ends a command.
|
|
# So the initial qubes.VMShell bash process, which is executing commands from
|
|
# stdin, consumes exactly the line from the "write" below and then either
|
|
# completes the "exec" or exits. In no event does it touch the stdin data
|
|
# intended for the command.
|
|
|
|
import os
|
|
import subprocess
|
|
import sys
|
|
|
|
cmd = ' '.join(sys.argv[1:])
|
|
sys.stdout.write("exec bash -c '%s' || exit 127\n" % cmd.replace("'", "'\\''"))
|
|
sys.stdout.flush()
|
|
|
|
local_stdin = int(os.environ['SAVED_FD_0'])
|
|
local_stdout = int(os.environ['SAVED_FD_1'])
|
|
stdin_sender = subprocess.Popen(['cat'], stdin=local_stdin)
|
|
stdout_receiver = subprocess.Popen(['cat'], stdout=local_stdout)
|
|
|
|
# sys.std{in,out}.close() do not close the FDs, but they apparently stop Python
|
|
# from trying to close the FDs again on exit and generating an exception.
|
|
sys.stdin.close()
|
|
sys.stdout.close()
|
|
os.close(0)
|
|
# The really important step, so this process doesn't prevent qrexec-client-vm
|
|
# from seeing EOF on input.
|
|
os.close(1)
|
|
os.close(local_stdin)
|
|
os.close(local_stdout)
|
|
|
|
stdout_receiver.wait()
|
|
# With the current Qubes RPC implementation, the stdout receiver doesn't get EOF
|
|
# until the remote process has exited. At that point, we want to finish and not
|
|
# try to send more input. This is the same behavior ssh appears to have.
|
|
stdin_sender.terminate()
|
|
stdin_sender.wait()
|