23 Aug 2005
Tim Newsham
Public Domain.

This code is in the public domain.
Please send any bug reports to tim dot newsham at gmail dot com.

- cl.py is a 9p client that can be run from the command line.
	cl.py [-d] [-a authsrv] [-n] [-p srvport] user srv [cmd ...]

	The client utility accesses files on a 9p server.  The username
	and server address must be specified.  The 'p' option can
	be used to connect to a nonstandard port on the server.  An
	argument to the 'a' option specifies the authentication server
	to access.  If none is given it is assumed that the authentication
	server is running on the same server as the fileserver.  The
	authentication server should serve the domain that the fileserver
	is in.   The 'n' option skips the password prompt.  If it is
	used and a password is required an error is generated.

	If commands are specified on the command line (one per
	argument) they are executed directly, otherwise the user is
	prompted for commands.  The builtin command "help" will list
	out all available commands.

	Using the 'd' option causes the python debugger to be invoked
	on any error conditions.

	Example:
		$ cl.py newsham sources.cs.bell-labs.com 'cd patch' ls
		Password:
		applied isatty runq-keep-lock-alive saved scuzz-big-exabyte sorry

- srv.py is a 9p server that can be run from the command line.
	srv.py [-d] [-m module] [-p port] [-r root] srvuser domain

	The server accepts connections from 9p clients.  It provides
	access to the files on the machine it was run on with the
	privilege of the user who invoked it.  Authentication is
	done against an auth server (not included here) for the
	domain specified on the command line.  A valid user and
	password for that domain must be given to perform authentication.

	The 'r' option specifies the root of the filesystem tree which
	is the local filesystem root if unspecified.  Multiple 'm' options
	may be specified to load extra modules into the server.

	The 'p' option allows a nonstandard port to be specified.
	Using the 'd' option causes the python debugger to be invoked
	on any error conditions.

	Example:
		$ srv.py newsham p9home.dom
		$ srv.py -r /tmp -m sampledev newsham p9home.dom

- P9.py has primitives for dealing with the 9p protocol.
- P9sk1.py has primitives for dealing with the p9sk1 protocol.
- debug.py provides access to the python debugger.

This package requires the Python Cryptography Toolkit
from http://www.amk.ca/python/code/crypto to work.


Notes:
  - The server operates with the full privilege of whoever ran the
    process.  Appropriate steps should be taken to limit access if
    security is a concern.
  - it appears the kernel doesn't necessarily clunk an open handle 
    for a binary after a process stops.  This may cause slightly
    unexpected results on systems that do not allow open files to be
    removed.  As an example, when the server is running under cygwin
    and you execute a file, then remove all files in a directory and
    then try to remove the directory a 'Directory not empty' error
    will be given since there is still an open file in that directory.
  - cl's client features can be imported and used as a library.
  - the put command can take input from stdin by specifying the local
    file '-'.
  - the 'r' option should not be relied on for security.
  - The server operates synchronously.  This means that some file
    operations will affect the performance of other operations
    going to the same server (for example, playing audio).

Flaws:
  - The password and auth server are given before the server requests
    a particular domain.  In fact the domain is never even shown to the
    user.  Ideally the auth server would be looked up based on the domain
    the server asks for.
  - It would be nice to provide an object that is comptabiel with
    the python file() object.
  - The server shows numeric user and group information.
  - Server output is to standard output.
  - In windows the server accepts only a single connection.  
	XXX due to a bug the cygwin version has this limitation as well.
  - The challenges used in authentication are not cryptographically strong.