354 lines
10 KiB
Groff
354 lines
10 KiB
Groff
.\" groff -man -Tascii iodine.8
|
|
.TH IODINE 8 "APR 2012" "User Manuals"
|
|
.SH NAME
|
|
iodine, iodined \- tunnel IPv4 over DNS
|
|
.SH SYNOPSIS
|
|
.B iodine [-v]
|
|
|
|
.B iodine [-h]
|
|
|
|
.B iodine [-f] [-r] [-u
|
|
.I user
|
|
.B ] [-P
|
|
.I password
|
|
.B ] [-m
|
|
.I fragsize
|
|
.B ] [-t
|
|
.I chrootdir
|
|
.B ] [-d
|
|
.I device
|
|
.B ] [-R
|
|
.I rdomain
|
|
.B ] [-m
|
|
.I fragsize
|
|
.B ] [-M
|
|
.I namelen
|
|
.B ] [-z
|
|
.I context
|
|
.B ] [-F
|
|
.I pidfile
|
|
.B ] [-T
|
|
.I dnstype
|
|
.B ] [-O
|
|
.I downenc
|
|
.B ] [-L
|
|
.I 0|1
|
|
.B ] [-I
|
|
.I interval
|
|
.B ]
|
|
.B [
|
|
.I nameserver
|
|
.B ]
|
|
.I topdomain
|
|
|
|
.B iodined [-v]
|
|
|
|
.B iodined [-h]
|
|
|
|
.B iodined [-c] [-s] [-f] [-D] [-u
|
|
.I user
|
|
.B ] [-t
|
|
.I chrootdir
|
|
.B ] [-d
|
|
.I device
|
|
.B ] [-m
|
|
.I mtu
|
|
.B ] [-l
|
|
.I listen_ip
|
|
.B ] [-p
|
|
.I port
|
|
.B ] [-n
|
|
(
|
|
.B auto
|
|
|
|
|
.I external_ip
|
|
)
|
|
.B ] [-b
|
|
.I dnsport
|
|
.B ] [-P
|
|
.I password
|
|
.B ] [-z
|
|
.I context
|
|
.B ] [-F
|
|
.I pidfile
|
|
.B ]
|
|
.I tunnel_ip
|
|
.B [
|
|
.I /netmask
|
|
.B ]
|
|
.I topdomain
|
|
.SH DESCRIPTION
|
|
.B iodine
|
|
lets you tunnel IPv4 data through a DNS
|
|
server. This can be useful in situations where Internet access is firewalled,
|
|
but DNS queries are allowed. It needs a TUN/TAP device to operate. The
|
|
bandwidth is asymmetrical,
|
|
with a measured maximum of 680 kbit/s upstream and 2.3 Mbit/s
|
|
downstream in a wired LAN test network.
|
|
Realistic sustained throughput on a Wifi network using a carrier-grade
|
|
DNS cache has been measured at some 50 kbit/s upstream and over 200 kbit/s
|
|
downstream.
|
|
.B iodine
|
|
is the client application,
|
|
.B iodined
|
|
is the server.
|
|
|
|
Note: server and client are required to speak the exact same protocol. In most
|
|
cases, this means running the same iodine version. Unfortunately, implementing
|
|
backward and forward protocol compatibility is usually not feasible.
|
|
.SH OPTIONS
|
|
.SS Common Options:
|
|
.TP
|
|
.B -v
|
|
Print version info and exit.
|
|
.TP
|
|
.B -h
|
|
Print usage info and exit.
|
|
.TP
|
|
.B -f
|
|
Keep running in foreground.
|
|
.TP
|
|
.B -u user
|
|
Drop privileges and run as user 'user' after setting up tunnel.
|
|
.TP
|
|
.B -t chrootdir
|
|
Chroot to 'chrootdir' after setting up tunnel.
|
|
.TP
|
|
.B -d device
|
|
Use the TUN device 'device' instead of the normal one, which is dnsX on Linux
|
|
and otherwise tunX.
|
|
.TP
|
|
.B -P password
|
|
Use 'password' to authenticate. If not used,
|
|
.B stdin
|
|
will be used as input. Only the first 32 characters will be used.
|
|
.TP
|
|
.B -z context
|
|
Apply SELinux 'context' after initialization.
|
|
.TP
|
|
.B -F pidfile
|
|
Create 'pidfile' and write process id in it.
|
|
.SS Client Options:
|
|
.TP
|
|
.B -r
|
|
Skip raw UDP mode. If not used, iodine will try getting the public IP address
|
|
of the iodined host and test if it is reachable directly. If it is, traffic
|
|
will be sent to the server instead of the DNS relay.
|
|
.TP
|
|
.B -R rdomain
|
|
Use OpenBSD routing domain 'rdomain' for the DNS connection.
|
|
.TP
|
|
.B -m fragsize
|
|
Force maximum downstream fragment size. Not setting this will cause the
|
|
client to automatically probe the maximum accepted downstream fragment size.
|
|
.TP
|
|
.B -M namelen
|
|
Maximum length of upstream hostnames, default 255.
|
|
Usable range ca. 100 to 255.
|
|
Use this option to scale back upstream bandwidth in favor of downstream
|
|
bandwidth.
|
|
Also useful for DNS servers that perform unreliably when using full-length
|
|
hostnames, noticable when fragment size autoprobe returns very
|
|
different results each time.
|
|
.TP
|
|
.B -T dnstype
|
|
DNS request type override.
|
|
By default, autodetection will probe for working DNS request types, and
|
|
will select the request type that is expected to provide the most bandwidth.
|
|
However, it may turn out that a DNS relay imposes limits that skew the
|
|
picture, which may lead to an "unexpected" DNS request type providing
|
|
more bandwidth.
|
|
In that case, use this option to override the autodetection.
|
|
In (expected) decreasing bandwidth order, the supported DNS request types are:
|
|
.IR NULL ,
|
|
.IR TXT ,
|
|
.IR SRV ,
|
|
.IR MX ,
|
|
.I CNAME
|
|
and
|
|
.I A
|
|
(returning CNAME).
|
|
Note that
|
|
.IR SRV ,
|
|
.I MX
|
|
and
|
|
.I A
|
|
may/will cause additional lookups by "smart" caching
|
|
nameservers to get an actual IP address, which may either slow down or fail
|
|
completely.
|
|
.TP
|
|
.B -O downenc
|
|
Force downstream encoding type for all query type responses except NULL.
|
|
Default is autodetected, but may not spot all problems for the more advanced
|
|
codecs.
|
|
Use this option to override the autodetection.
|
|
.I Base32
|
|
is the lowest-grade codec and should always work; this is used when
|
|
autodetection fails.
|
|
.I Base64
|
|
provides more bandwidth, but may not work on all nameservers.
|
|
.I Base64u
|
|
is equal to Base64 except in using underscore ('_')
|
|
instead of plus sign ('+'), possibly working where
|
|
.I Base64
|
|
does not.
|
|
.I Base128
|
|
uses high byte values (mostly accented letters in iso8859-1),
|
|
which might work with some nameservers.
|
|
For TXT queries,
|
|
.I Raw
|
|
will provide maximum performance, but this will only work if the nameserver
|
|
path is fully 8-bit-clean for responses that are assumed to be "legible text".
|
|
.TP
|
|
.B -L 0|1
|
|
Lazy-mode switch.
|
|
\-L1 (default): Use lazy mode for improved performance and decreased latency.
|
|
A very small minority of DNS relays appears to be unable to handle the
|
|
lazy mode traffic pattern, resulting in no or very little data coming through.
|
|
The iodine client will detect this and try to switch back to legacy mode,
|
|
but this may not always work.
|
|
In these situations use \-L0 to force running in legacy mode
|
|
(implies \-I1).
|
|
.TP
|
|
.B -I interval
|
|
Maximum interval between requests (pings) so that intermediate DNS
|
|
servers will not time out. Default is 4 in lazy mode, which will work
|
|
fine in most cases. When too many SERVFAIL errors occur, iodine
|
|
will automatically reduce this to 1.
|
|
To get absolute minimum DNS traffic,
|
|
increase well above 4, but not so high that SERVFAIL errors start to occur.
|
|
There are some DNS relays with very small timeouts,
|
|
notably dnsadvantage.com (ultradns), that will give
|
|
SERVFAIL errors even with \-I1; data will still get trough,
|
|
and these errors can be ignored.
|
|
Maximum useful value is 59, since iodined will close a client's
|
|
connection after 60 seconds of inactivity.
|
|
.SS Server Options:
|
|
.TP
|
|
.B -c
|
|
Disable checking the client IP address on all incoming requests.
|
|
By default, requests originating from non-matching IP adresses will be
|
|
rejected, however this will cause problems when requests are routed
|
|
via a cluster of DNS servers.
|
|
.TP
|
|
.B -s
|
|
Don't try to configure IP address or MTU.
|
|
This should only be used if you have already configured the device that will be
|
|
used.
|
|
.TP
|
|
.B -D
|
|
Increase debug level. Level 1 prints info about each RX/TX packet.
|
|
Implies the
|
|
.B -f
|
|
option.
|
|
On level 2 (-DD) or higher, DNS queries will be printed literally.
|
|
When using Base128 upstream encoding, this is best viewed as
|
|
ISO Latin-1 text instead of (illegal) UTF-8.
|
|
This is easily done with : "LC_ALL=C luit iodined -DD ..."
|
|
(see luit(1)).
|
|
.TP
|
|
.B -m mtu
|
|
Set 'mtu' as mtu size for the tun device.
|
|
This will be sent to the client on login, and the client will use the same mtu
|
|
for its tun device. Default 1130. Note that the DNS traffic will be
|
|
automatically fragmented when needed.
|
|
.TP
|
|
.B -l listen_ip
|
|
Make the server listen only on 'listen_ip' for incoming requests.
|
|
By default, incoming requests are accepted from all interfaces.
|
|
.TP
|
|
.B -p port
|
|
Make the server listen on 'port' instead of 53 for traffic.
|
|
If 'listen_ip' does not include localhost, this 'port' can be the same
|
|
as 'dnsport'.
|
|
.B Note:
|
|
You must make sure the dns requests are forwarded to this port yourself.
|
|
.TP
|
|
.B -n auto|external_ip
|
|
The IP address to return in NS responses. Default is to return the address used
|
|
as destination in the query.
|
|
If external_ip is 'auto', iodined will use externalip.net web service to
|
|
retrieve the external IP of the host and use that for NS responses.
|
|
.TP
|
|
.B -b dnsport
|
|
If this port is specified, all incoming requests not inside the tunnel domain
|
|
will be forwarded to this port on localhost, to be handled by a real dns.
|
|
If 'listen_ip' does not include localhost, this 'dnsport' can be the
|
|
same as 'port'.
|
|
.B Note:
|
|
The forwarding is not fully transparent, and not advised for use
|
|
in production environments.
|
|
.SS Client Arguments:
|
|
.TP
|
|
.B nameserver
|
|
The nameserver to use to relay the dns traffic. This can be any relaying
|
|
nameserver or the server running iodined if reachable. This field can be
|
|
given as an IP address, or as a hostname. This argument is optional, and
|
|
if not specified a nameserver will be read from the
|
|
.I /etc/resolv.conf
|
|
file.
|
|
.TP
|
|
.B topdomain
|
|
The dns traffic will be sent as queries for subdomains under
|
|
\'topdomain'. This is normally a subdomain to a domain you own. Use a short
|
|
domain name to get better throughput. If
|
|
.B nameserver
|
|
is the iodined server, then the topdomain can be chosen freely. This argument
|
|
must be the same on both the client and the server.
|
|
.SS Server Arguments:
|
|
.TP
|
|
.B tunnel_ip[/netmask]
|
|
This is the server's ip address on the tun interface. The client will be
|
|
given the next ip number in the range. It is recommended to use the
|
|
10.0.0.0 or 172.16.0.0 ranges. The default netmask is /27, can be overriden
|
|
by specifying it here. Using a smaller network will limit the number of
|
|
concurrent users.
|
|
.TP
|
|
.B topdomain
|
|
The dns traffic is expected to arrive as queries for
|
|
subdomains under 'topdomain'. This is normally a subdomain to a domain you
|
|
own. Use a short domain name to get better throughput. This argument must be
|
|
the same on both the client and the server. Queries for domains other
|
|
than 'topdomain' will be forwarded when the \-b option is given, otherwise
|
|
they will be dropped.
|
|
.SH EXAMPLES
|
|
See the README file for both a quick test scenario, and a detailed description
|
|
of real-world deployment.
|
|
.SH SECURITY
|
|
Login is a relatively secure challenge-response MD5 hash, with the
|
|
password never passing the wire.
|
|
However, all other data is
|
|
.B NOT
|
|
encrypted in any way. The DNS traffic is also vulnerable to replay,
|
|
injection and man-in-the-middle attacks, especially when iodined is used
|
|
with the \-c option. Use of ssh or vpn tunneling is strongly recommended.
|
|
On both server and client, use
|
|
.IR iptables ,
|
|
.I pf
|
|
or other firewalls to block all traffic coming in from the tun interfaces,
|
|
except to the used ssh or vpn ports.
|
|
.SH ENVIRONMENT
|
|
.SS IODINE_PASS
|
|
If the environment variable
|
|
.B IODINE_PASS
|
|
is set, iodine will use the value it is set to as password instead of asking
|
|
for one. The
|
|
.B -P
|
|
option still has precedence.
|
|
.SS IODINED_PASS
|
|
If the environment variable
|
|
.B IODINED_PASS
|
|
is set, iodined will use the value it is set to as password instead of asking
|
|
for one. The
|
|
.B -P
|
|
option still has precedence.
|
|
.El
|
|
.SH SEE ALSO
|
|
The README file in the source distribution contains some more elaborate
|
|
information.
|
|
.SH BUGS
|
|
File bugs at http://dev.kryo.se/iodine/
|
|
.SH AUTHORS
|
|
Erik Ekman <yarrick@kryo.se> and Bjorn Andersson <flex@kryo.se>. Major
|
|
contributions by Anne Bezemer.
|