.SH "SYNOPSIS"
.B tripe
.RB [ \-D ]
-.RB [ \-p
-.IR port ]
-.RB [ \-T
-.IR trace-opts ]
.RB [ \-d
.IR dir ]
+.RB [ \-b
+.IR addr ]
+.RB [ \-p
+.IR port ]
+.RB [ \-n
+.IR tunnel ]
+.br
+
+.RB [ \-U
+.IR user ]
+.RB [ \-G
+.IR group ]
.RB [ \-a
.IR socket ]
+.RB [ \-T
+.IR trace-opts ]
.br
.RB [ \-k
The
.B tripe
program is a server which can provide strong IP-level encryption and
-authentication between two co-operating hosts. The program and its
-protocol are deliberately very simple, to make analysing them easy and
-to help build trust rapidly in the system.
+authentication between co-operating hosts. The program and its protocol
+are deliberately very simple, to make analysing them easy and to help
+build trust rapidly in the system.
.SS "Overview"
The
.B tripe
If not given any command-line arguments,
.B tripe
will initialize by following these steps:
-.hP \*o
-It changes directory to
-.BR /var/lib/tripe .
-.hP \*o
+.hP 1.
+It sets the directory named by the
+.B TRIPEDIR
+environment variable (or
+.B /var/lib/tripe
+if the variable is unset) as the current directory.
+.hP 2.
It acquires a UDP socket with an arbitrary kernel-selected port number.
It will use this socket to send and receive all communications with its
peer servers. The port chosen may be discovered by means of the
.B PORT
admin command (see
.BR tripe\-admin (5)).
-.hP \*o
+.hP 3.
It loads the private key with the tag or type name
.B tripe\-dh
from the Catacomb-format file
They are maintained using the program
.BR key (1)
provided with the Catacomb distribution.)
-.hP \*o
+.hP 4.
It creates and listens to the Unix-domain socket
.BR tripesock .
.PP
connections and obeying any administrative commands, and communicating
with peers. It also treats its standard input and standard output
streams as an admin connection, reading commands from standard input and
-writing responses and diagnostics messages to standard output.
+writing responses and diagnostics messages to standard output. Finally,
+it will reload keys from its keyring files if it notices that they've
+changed (it checks inode number and modification time) \- there's no
+need to send a signal.
.PP
Much of this behaviour may be altered by giving
.B tripe
.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
.B .
if you don't want it to change directory at all.
.TP
+.BI "\-b, \-\-bind-address="addr
+Bind the UDP socket to IP address
+.I addr
+rather than the default of
+.BR INADDR_ANY .
+This is useful if your main globally-routable IP address is one you want
+to tunnel through the VPN.
+.TP
.BI "\-p, \-\-port=" port
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
+(either a user name or integer uid) after initialization. Also set gid
+to
+.IR user 's
+primary group, unless overridden by a
+.B \-G
+option.
+.TP
+.BI "\-G, \-\-setgid=" group
+Set gid to that of
+.I group
+(either a group name or integer gid) after initialization.
+.TP
.BI "\-k, \-\-priv\-keyring=" file
Reads the private key from
.I file
has the addresses 10.0.1.1 and 200.0.1.1; site B's gateway is
.B bob
and has addresses 10.0.2.1 and 200.0.2.1.
-.PP
-This isn't quite complicated enough. Each of
-.B alice
-and
-.B bob
-needs an extra IP address which we'll use when setting up the
-point-to-point link. These addresses need to be routable, at least
-within the virtual private network: unfortunately, you can't just use
-the same pair everywhere. We'll assign
-.B alice
-the point-to-point address 192.168.0.1, and
-.B bob
-the address 192.168.0.2.
.hP 1.
Install
.B tripe
servers up. Run
.RS
.VS
-tripectl \-slD \-S\-P23169
+tripectl \-slD \-S\-p22003
.VE
on each of
.B alice
and
.BR bob .
(The
-.RB ` \-P23169 '
-forces the server to use UDP port 23169: use some other number if 23169
-is inappropriate for your requirements. I chose it by reducing the
-RIPEMD160 hash of
-.RB ` tripe\-port\-number\e0 '
-modulo 2\*(ss16\*(se.)
+.RB ` \-p22003 '
+forces the server to use UDP port 22003: use some other number if 22003
+is inappropriate for your requirements. I chose it by taking the first
+16 bits of the RIPEMD160 hash of
+.RB ` TrIPE '.
.RE
.hP 6.
To get
.VS
#! /bin/sh
-tripectl add bob 200.0.2.1 23169
+tripectl add bob 200.0.2.1 22003
ifname=`tripectl ifname bob`
-ifconfig $ifname \e
- 192.168.0.1 \e
- pointopoint 192.168.0.2
+ifconfig $ifname 10.0.1.1 pointopoint 10.0.2.1
route add -net \e
10.0.2.0 netmask 255.255.255.0 \e
- gw 192.168.0.2
+ gw 10.0.2.1
.VE
Read
.BR ifconfig (8)
.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 not create SLIP tunnels 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 wedged waiting 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