.IR addr ]
.RB [ \-p
.IR port ]
+.RB [ \-n
+.IR tunnel ]
.br
.RB [ \-U
.B "\-u, \-\-usage"
Writes a brief usage summary to standard output and exits with status 0.
.TP
+.B "\-\-tunnels"
+Writes to standard output a list of the configured tunnel drivers, one
+per line, and exits with status 0. This is intended for the use of the
+start-up script, so that it can check that it will actually work.
+.TP
.B "\-D, \-\-daemon"
Dissociates from its terminal and starts running in the background after
completing the initialization procedure described above. If running as
Use the specified UDP port for all communications with peers, rather
than an arbitarary kernel-assigned port.
.TP
+.BI "\-n, \-\-tunnel=" tunnel
+Use the specified tunnel driver for new peers by default.
+.TP
.BI "\-U, \-\-setuid=" user
Set uid to that of
.I user
.hP 7.
Congratulations. The two servers will exchange keys and begin sending
packets almost immediately. You've set up a virtual private network.
+.SS "Using elliptic curve keys"
+The
+.B tripe
+server can use elliptic curve Diffie-Hellman for key exchange, rather
+than traditional integer Diffie-Hellman. Given current public
+knowledge, elliptic curves can provide similar or better security to
+systems based on integer discrete log problems, faster, and with less
+transmitted data. It's a matter of controversy whether this will
+continue to be the case. The author uses elliptic curves.
+.PP
+The server works out which it
+should be doing based on the key type, which is either
+.B tripe\-dh
+for standard Diffie-Hellman, or
+.B tripe\-ec
+for elliptic curves. To create elliptic curve keys, say something like
+.VS
+key add \-aec\-param \-Cnist-p192 \-eforever \e
+ \-tparam tripe\-ec\-param
+.VE
+to construct a parameters key, using your preferred elliptic curve in
+the
+.B \-C
+option (see
+.BR key (1)
+for details); and create the private keys by
+.VS
+key add \-aec \-pparam \-talice \e
+ \-e"now + 1 year" tripe\-ec
+.VE
+Now start
+.B tripe
+with the
+.B \-ttripe\-ec
+option, and all should be well.
+.SS "Using other symmetric algorithms"
+The default symmetric algorithms
+.B tripe
+uses are Blowfish (by Schneier) for symmetric encryption, and RIPEMD-160
+(by Dobbertin, Bosselaers and Preneel) for hashing and as a MAC (in HMAC
+mode, designed by Bellare, Canetti and Krawczyk). These can all be
+overridden by setting attributes on your private key, as follows.
+.TP
+.B cipher
+Names the symmetric encryption scheme to use. The default is
+.BR blowfish\-cbc .
+.TP
+.B hash
+Names the hash function to use. The default is
+.BR rmd160 .
+.TP
+.B mac
+Names the message authentication code to use. The name of the MAC may
+be followed by a
+.RB ` / '
+and the desired tag length in bits. The default is
+.IB hash \-hmac
+at half the underlying hash function's output length.
+.TP
+.B mgf
+A `mask-generation function', used in the key-exchange. The default is
+.IB hash \-mgf
+and there's no good reason to change it.
+.SS "Using SLIP interfaces"
+Though not for the faint of heart, it is possible to get
+.B tripe
+to read and write network packets to a pair of file descriptors using
+SLIP encapsulation. No fancy header compression of any kind is
+supported.
+.PP
+Two usage modes are supported: a preallocation system, whereby SLIP
+interfaces are created and passed to the
+.B tripe
+server at startup; and a dynamic system, where the server runs a script
+to allocate a new SLIP interface when it needs one. It is possible to
+use a mixture of these two modes, starting
+.B tripe
+with a few preallocated interfaces and having it allocate more
+dynamically as it needs them.
+.PP
+The behaviour of
+.BR tripe 's
+SLIP driver is controlled by the
+.B TRIPE_SLIPIF
+environment variable. The server will fail to start if this variable is
+not defined. The variable's value is a colon-delimited list of
+preallocated interfaces, followed optionally by the filename of a script
+to run to dynamically allocate more interfaces.
+.PP
+A static allocation entry has the form
+.IR infd [ \c
+.BI , outfd \c
+.RB ] \c
+.BI = \c
+.IR ifname ,
+If the
+.I outfd
+is omitted, the same file descriptor is used for input and output.
+.PP
+The dynamic allocation script must be named by an absolute or relative
+pathname, beginning with
+.RB ` / '
+or
+.RB ` . '.
+The server will pass the script an argument, which is the name of the
+peer for which the interface is being created. The script should
+allocate a new SLIP interface (presumably by creating a pty pair),
+configure it appropriately, and write the interface's name to its
+standard output, followed by a newline. It should then read and write
+SLIP packets on its stdin and stdout. The script's stdin will be closed
+when the interface is no longer needed, and the server will attempt to
+send it a
+.B SIGTERM
+signal (though this may fail if the script runs with higher privileges
+than the server).
+.PP
+The output file descriptor should not block unless it really needs to:
+the
+.B tripe
+daemon assumes that it won't, and will get wait for it to accept output.
.SS "About the name"
The program's name is
.BR tripe ,
.IR "The Trivial IP Encryption Protocol" ,
.IR "The Wrestlers Protocol" .
.SH "AUTHOR"
-Mark Wooding, <mdw@nsict.org>
+Mark Wooding, <mdw@distorted.org.uk>
~mdw / tripe / blobdiff