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78 lines
3.5 KiB
Markdown
78 lines
3.5 KiB
Markdown
HKExSh
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--
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'hkexsh' (HerraduraKEx shell) is a golang implementation of a simple
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remote shell client and server, similar in role to ssh, offering
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encrypted interactive and non-interactive sessions. The client and server
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programs (hkexsh and hkexshd) use a mostly drop-in replacement for golang's
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standard golang/pkg/net facilities (net.Dial(), net.Listen(), net.Accept()
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and the net.Conn type), which automatically negotiate keying material for
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'secure' sockets using the experimental HerraduraKEx key exchange algorithm
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first released at
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[Omar Elejandro Herrera Reyna's HerraduraKEx project](http://github.com/Caume/HerraduraKEx).
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One can simply replace calls to net.Dial() with hkex.Dial(), and likewise
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net.Listen() with hkex.Listen(), to obtain connections (hkex.Conn) conforming
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to the basic net.Conn interface. Upon Dial(), the HerraduraKEx key exchange
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is initiated (whereby client and server independently derive the same
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keying material).
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Above the hkex.Conn layer, the server and client apps in this repository
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(server/hkexshd and client/hkexsh) negotiate session settings (cipher/hmac
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algorithms, interactive/non-interactive, etc.) to be used for further
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communication.
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Packets are subject to random padding, and (optionally) the client and server
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channels can both send _chaff_ packets at random defineable intervals to help
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thwart analysis of session activity (especially for interactive shell sessions).
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NOTE: Due to the experimental nature of the HerraduraKEx algorithm used to
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derive crypto keying material, this algorithm and the demonstration remote
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shell client/server programs should be used with caution and should definitely
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NOT be used for any sensitive applications, or at the very least at one's
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own risk.
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As of this time (Jan 2018) no verdict by acknowledged 'crypto experts' as to
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the level of security of the HerraduraKEx algorithm for purposes of session
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key exchange over an insecure channel has been rendered.
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It is hoped that experts in the field will analyze the algorithm and
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determine if it is indeed a suitable one for use in situations where
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Diffie-Hellman or other key exchange algorithms are currently utilized.
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Finally, within the hkexpasswd/ directory is a password-setting utility
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using its own user/password file distinct from the system /etc/passwd, which
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is used by the hkexshd server to authenticate clients.
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Dependencies:
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--
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* Recent version of go (tested with go-1.9)
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* [github.com/mattn/go-isatty](http://github.com/mattn/go-isatty) //terminal tty detection
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* [github.com/kr/pty](http://github.com/kr/pty) //unix pty control (server pty connections)
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* [github.com/jameskeane/bcrypt](http://github.com/jameskeane/bcrypt) //password storage/auth
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* [blitter.com/go/goutmp](https://blitter.com/gogs/Russtopia/goutmp) // wtmp/lastlog C bindings
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Get source code
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--
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* $ go get -u blitter.com/go/hkexsh
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* $ cd $GOPATH/src/blitter.com/go/hkexsh
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* $ go build ./... # install all dependent go pkgs
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To build
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--
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* $ cd $GOPATH/src/blitter.com/go/hkexsh
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* $ make clean all
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To set accounts & passwords:
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--
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* $ echo "joebloggs:*:*:*" >hkexsh.passwd
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* $ sudo mv hkexsh.passwd /etc
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* $ sudo hkexpasswd/hkexpasswd -u joebloggs
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* $ <enter a password, enter again to confirm>
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Running Clent and Server. In separate shells:
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--
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* [A]$ sudo hkexshd/hkexshd & # add -d for debugging
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* [B]$ hkexsh/hkexsh -u joebloggs # add -d for debugging
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NOTE if running client (hkexsh) with -d, one will likely need to run 'reset' afterwards to fix up the shell tty afterwards as stty echo may not be restored if client crashes or is interrupted.
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