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# coding: utf-8
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# shells.py - functions for validating user shells
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#
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# Copyright (C) 2013 Arthur de Jong
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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import ctypes
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import ctypes.util
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import os
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import sys
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def list_shells():
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"""List the shells from /etc/shells."""
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libc = ctypes.CDLL(ctypes.util.find_library("c"))
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libc.setusershell()
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while True:
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shell = ctypes.c_char_p(libc.getusershell()).value
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if not shell:
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break
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yield shell
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libc.endusershell()
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def shellexists(shell):
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"""Check if the provided shell exists and is executable."""
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return os.path.isfile(shell) and os.access(shell, os.X_OK)
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def check(shell, asroot=False):
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"""Check if the specified shell is valid and exit if it isn't."""
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# if the shell is listed in /etc/shells, everything should be OK
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if shell in list_shells():
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return
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# if we are not root, bail out
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if not asroot:
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if not shell:
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# FIXME: print to stderr
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print('%s: empty shell not allowed' % sys.argv[0])
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else:
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# FIXME: print to stderr
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print('%s: %s is an invalid shell' % (sys.argv[0], shell))
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sys.exit(1)
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# warn if something seems wrong
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if not shell:
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# FIXME: print to stderr
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print('%s: Warning: setting empty shell' % sys.argv[0])
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elif not shellexists(shell):
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print('%s: Warning: %s does not exist' % (sys.argv[0], shell))
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