3b0f80e19f
Both Archlinux and Fedora 29 have guidelines to point explicitly at /usr/bin/python2 where it expect python2. Also, do not use env. Fixes QubesOS/qubes-issues#4027
46 lines
1.9 KiB
Python
Executable File
46 lines
1.9 KiB
Python
Executable File
#!/usr/bin/python2
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# Send the command to the remote side, and then transfer stdin from local to
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# remote and stdout from remote to local.
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#
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# The tricky part is delimiting the command from the stdin data. If we were
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# implementing this from scratch, we'd probably use a null byte. However, we'd
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# like to work with the existing qubes.VMShell service, whose implementation is
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# simply "/bin/bash", so users don't have to maintain duplicate RPC policy. We
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# take advantage of the fact that when bash is executing commands from a pipe,
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# it reads one character at a time until it gets a newline that ends a command.
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# So the initial qubes.VMShell bash process, which is executing commands from
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# stdin, consumes exactly the line from the "write" below and then either
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# completes the "exec" or exits. In no event does it touch the stdin data
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# intended for the command.
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import os
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import subprocess
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import sys
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cmd = ' '.join(sys.argv[1:])
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sys.stdout.write("exec bash -c '%s' || exit 127\n" % cmd.replace("'", "'\\''"))
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sys.stdout.flush()
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local_stdin = int(os.environ['SAVED_FD_0'])
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local_stdout = int(os.environ['SAVED_FD_1'])
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stdin_sender = subprocess.Popen(['cat'], stdin=local_stdin)
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stdout_receiver = subprocess.Popen(['cat'], stdout=local_stdout)
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# sys.std{in,out}.close() do not close the FDs, but they apparently stop Python
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# from trying to close the FDs again on exit and generating an exception.
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sys.stdin.close()
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sys.stdout.close()
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os.close(0)
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# The really important step, so this process doesn't prevent qrexec-client-vm
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# from seeing EOF on input.
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os.close(1)
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os.close(local_stdin)
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os.close(local_stdout)
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stdout_receiver.wait()
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# With the current Qubes RPC implementation, the stdout receiver doesn't get EOF
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# until the remote process has exited. At that point, we want to finish and not
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# try to send more input. This is the same behavior ssh appears to have.
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stdin_sender.terminate()
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stdin_sender.wait()
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