.\" Copyright (c) 2023 Joost van Baal-Ilić <joostvb-uruk@mdcc\&.cx>
.TH "uruk-rc" 5 "9 окт 2023" "uruk-rc 20231009" "FILE FORMATS "
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.SH NAME
uruk-rc \- uruk resource file, defining access policy
.SH SYNOPSIS

\fC/etc/uruk/rc\fP
.SH DESCRIPTION
\fIrc\fP is a shell script snippet, sourced in \fBuruk\fP by /bin/sh\&.

\fIrc\fP lists IP addresses, allowed to use services\&.
.SH EXAMPLES

\fBdefault\fP
.br
The simplest valid \fIrc\fP file is the empty file\&. This \fIrc\fP file blocks all TCP
and UDP connection attempts to services on our host: this is the default
behaviour\&.

\fBsimplest\fP
.br
The simplest \fIrc\fP file which does allow traffic to our services looks like e\&.g\&.:

.di ZV
.in 0
.nf \fC
 interfaces=eth0

 ips_eth0=default
 ip_eth0_default=192\&.168\&.26\&.27
 net_eth0_default=192\&.168\&.0\&.0/16

 ip6_eth0_default=2001:db8::1/64
 net6_eth0_default=2001:db8::/32

 services_eth0_default_tcp=local
 ports_eth0_default_tcp_local="0:65535"
 sources_eth0_default_tcp_local="0\&.0\&.0\&.0/0 ::/0"

 services_eth0_default_udp=local
 ports_eth0_default_udp_local="0:65535"
 sources_eth0_default_udp_local="0\&.0\&.0\&.0/0"
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

This \fIrc\fP file allows all IPv4 and IPv6 UDP and TCP traffic from publicly routable IPs to
eth0\&'s IP\&.

\fBrealistic\fP
.br
If you\&'d like to block traffic on wlan0 and allow traffic to ssh on your
wired interface, and don\&'t like to explicitly set your IPs in \fIrc\fP:

.di ZV
.in 0
.nf \fC
 # list of interfaces you\&'d like uruk to protect
 interfaces=eth0 wlan0

 # set variables ip{,6}_eth0_default and net{,6}_eth0_default
 \&. /lib/uruk/init/autodetect-ips
 
 # names for eth0\&'s 2 IPv4 addresses
 ips_eth0="default dhcp"

 # allow access to our sshd on eth0\&'s primary IP on tcp port 443
 # from anywhere
 services_eth0_default_tcp=ssh
 ports_eth0_default_tcp_ssh=443
 sources_eth0_default_tcp_ssh="0\&.0\&.0\&.0/0 ::/0"
 
 # we get a static IPv4 via dhcp
 ip_eth0_dhcp=10\&.0\&.0\&.3
 net_eth0_dhcp=10\&./8

 services_eth0_dhcp_tcp=http
 ports_eth0_dhcp_tcp_http=http
 sources_eth0_dhcp_tcp_http=$net_eth0_dhcp

 # we leave services_wlan0_default_{tcp,udp} unset: don\&'t allow any
 # incoming connections on wlan0\&'s default IP 
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

\fBautodetect-ips\fP
.br
The script autodetect-ips --as used in the previous example-- looks for files
/etc/sysconfig/network-scripts/ifcfg-* (commonly found at e\&.g\&. Red Hat and
Fedora systems) and /etc/network/interfaces (as found at e\&.g\&. Debian and Ubuntu
systems), and, for each interface \fInic\fP, and each found IPv4 and IPv6
address and network, sets variables \fCip_\fP\fInic\fP\fC_default\fP,
\fCip6_\fP\fInic\fP\fC_default\fP, \fCnet_\fP\fInic\fP\fC_default\fP and
\fCnet6_\fP\fInic\fP\fC_default\fP \&. Then it calls ip(8) and adds any other found
\fInic\fP, \fCip\fP and \fCnet\fP triplets (for IPv4 and, for IPv6, only addresses
in scope "global")\&.

The script autodetect-ips is useful if you\&'d like to share your \fIrc\fP file among
different hosts\&.

\fBanother example\fP
.br
For an even more reasonable \fIrc\fP file, look at the well-commented example \fIrc\fP
file in \fC/usr/share/doc/uruk/examples/rc\fP\&.
.SH IPv4 AND IPv6

You can mix IPv4 and IPv6-addresses in sources_*\&. E\&.g\&.:

.di ZV
.in 0
.nf \fC
 ips_eth0=\&'default private\&'
 ip_eth0_default=1\&.2\&.3\&.4
 ip6_eth0_default=

 services_eth0_default_tcp=\&'mail local\&'

 sources_eth0_default_tcp_mail=\&'10\&.0\&.0\&.0/24 192\&.0\&.32\&.0/24 192\&.168\&.6\&.26\&'
 sources_eth0_default_tcp_local=\&'192\&.0\&.32\&.0/24 svejk\&.example\&.com 2001:db8::/32\&'

 ports_eth0_default_tcp_mail=smtp
 ports_eth0_default_tcp_local=\&'ssh ftp\&'
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

If svejk\&.example\&.com has both an IPv4 PTR record in DNS, as well as
an IPv6 PTR record, connection attempts from svejk to the ssh and ftp
TCP ports are allowed, via both IPv4 and IPv6\&.

Uruk used to require variables sources6_* to be set to support ip6tables\&.
Since uruk version 20140319 (The Alfama Release), this is no longer needed;
setting sources_* suffices\&. To be precise, the semantics since uruk version
20140319 is: 1) If both sources_* and sources6_* are defined (even if they\&'re
just empty), each is used for its respective address family\&. (This ensures
backwards compatibility\&.) 2) If sources6_* is undefined, sources_* is used for
both v4 and v6\&. 3) In either case, v4 literals in v6 context and v6 literals
in v4 context are silently (!) ignored\&.
.SH HOOKS
Uruk offers hooks for inserting your own code between iptables invocations\&.
Examples will show the usefulness of these hooks\&.

\fBallowing broadcasts\fP
.br
In \fIrc\fP, there is:

.di ZV
.in 0
.nf \fC
 rc_b=$etcdir/bootp
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

while the file \fCbootp\fP reads

.di ZV
.in 0
.nf \fC
 iptables \-A INPUT \-m state \-\-state NEW \-i eth0 \e
   \-\-protocol udp \-\-destination-port bootps \-j ACCEPT
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

\&.
This enables one to add rules for packets with broadcast addresses in their
destination\&. (Uruk has no support for this in its regular \fIrc\fP\&.)

\fBallowing non-matching returntraffic\fP
.br
In \fIrc\fP there is:

.di ZV
.in 0
.nf \fC
 rc_d=$etcdir/dns
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

while the file \fCdns\fP reads

.di ZV
.in 0
.nf \fC
  for source in 10\&.5\&.0\&.27 10\&.56\&.0\&.40
  do
    $iptables -A INPUT -i eth0 --protocol udp \e
      --source "$source" --source-port domain \e
      --destination "$ip_eth0" \e
      --destination-port 30000: -j ACCEPT
  done
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

This allows one to allow (return)traffic, disregarding the state\&. (Uruk has no
support for this in its regular \fIrc\fP\&.)

\fBallowing NAT\fP
.br
In \fIrc\fP there is:

.di ZV
.in 0
.nf \fC
 rc_a=${etcdir}/nat
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

while the file \fCnat\fP reads

.di ZV
.in 0
.nf \fC
  $iptables -t nat -A POSTROUTING \e
    --out-interface eth0 -j SNAT \e
    --to-source $ip_eth0
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

This allows Network Address Translation\&. However, beware! Like all extensive
use of hooks, this will break the \fBuruk-save\fP script\&. If you make sure your
active iptables rules are wiped, and invoke \fBuruk\fP manually to load new rules,
you\&'re safe\&. Using the init script with its default settings is safe too\&.

\fBallowing IPv6 tunneling\fP
.br
In \fIrc\fP there is:

.di ZV
.in 0
.nf \fC
 rc_b=${etcdir}/proto_41
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

while the file \fCproto_41\fP reads

.di ZV
.in 0
.nf \fC
 $iptables -A INPUT -i ppp0 --protocol 41 --destination $ip_ppp0 -j ACCEPT
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

This allows IP protocol 41, typically used for this kind of tunneling\&.

\fBallowing any traffic on an interface\fP
.br
In \fIrc\fP there is:

.di ZV
.in 0
.nf \fC
 interfaces_unprotect="lo eth2"
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

This allows any traffic on \fCeth2\fP (and on \fClo\fP, the default), including
any ICMP packets and packets from any source address\&.

\fBusing multiple hooks at one entry point in the main uruk process\fP
.br
In case rc_a, rc_b, \&.\&.\&. , or rc_i does not have a file as its value, but a
directory, all files matching "$rc_x"/*\&.rc will get sourced\&. This helps
configuration management in complex situations involving lots of uruk
configuration files for lots of hosts\&.

See the section "THE GORY DETAILS: uruk INTERNALS" in \fBuruk(8)\fP
(or the \fBuruk\fP source) to find out which hook (there are hooks rc_a, rc_b, \&.\&.\&. ,
rc_i) to use\&.
.SH NETWORK INTERFACES WITH MULTIPLE IP ADDRESSES
Uruk supports situations where a network interface has more than one IP address
attached\&. Variables \fCips_\fP\fInic\fP and \fCbcasts_\fP\fInic\fP are used for
this\&.

If \fCips_\fP\fInic\fP is set, e\&.g\&. like

.di ZV
.in 0
.nf \fC
 ips_eth0="ip0 ip1 ip2"
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

we assume multiple (three in this example) IPs are assigned to \fCeth0\fP\&. If
this variable is not set only one IP is supported on \fCeth0\fP\&.

In multiple-IP mode, IP addresses are listed as e\&.g\&.

.di ZV
.in 0
.nf \fC
 ip_eth0_ip0="137\&.56\&.247\&.16"
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

(If you\&'re used to the Linux ifconfig(8) output, you could use the name \fCip\fP
for \fCeth0\fP, and \fCip0\fP for \fCeth0:0\fP\&.)
The \fIports\fP, \fIservices\fP and \fIsources\fP variables look like
e\&.g\&.

.di ZV
.in 0
.nf \fC
 services_eth0_ip2_tcp=local
 ports_eth0_ip2_tcp_local=smtp
 sources_eth0_ip2_tcp_local=$localnet
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

and, similarly,

.di ZV
.in 0
.nf \fC
 net_eth0_ip1=192\&.168\&.0\&.0/16
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

Furthermore, for dropping broadcast packets, specify e\&.g\&.

.di ZV
.in 0
.nf \fC
 bcasts_eth0="ip0 ip2"     # yes, possibly a subset of ips_eth0
 bcast_eth0_ip0="10\&.0\&.0\&.255"
 bcast_eth0_ip2="10\&.0\&.255\&.255"
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

As an additional feature, if you have multiple IP addresses that all need
to get the same rules, you can assign them to a single name:

.di ZV
.in 0
.nf \fC
 ip_eth0_ip0="137\&.56\&.247\&.16 137\&.56\&.247\&.17 137\&.56\&.247\&.18"
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

.SH LOGGING AND DEBUGGING
Uruk has support for logging network packets, and for debugging the uruk
script\&.

\fBLogging\fP
.br
By default, uruk logs denied packets\&. This is adjustable using the
\fIloglevel\fP variable\&. The settings are:

.ZI 2m "\(bu"
\&
.br
"zero": be silent; do not log any packet\&. \fIrc\fP file features \fCloglevel=10\fP\&.
.in -2m
.ZI 2m "\(bu"
\&
.br
"low": log denied packets, which are targeted at one of our IPs\&.
\fIrc\fP file features \fCloglevel=30\fP\&.
.in -2m
.ZI 2m "\(bu"
\&
.br
"medium": log denied non-broadcast packets\&. This is the default:
\fIloglevel\fP is unset or \fIrc\fP file features \fCloglevel=50\fP\&.
.in -2m
.ZI 2m "\(bu"
\&
.br
"fascist": log all packets\&. \fIrc\fP file features \fCloglevel=90\fP\&.
.in -2m

\fBDebugging\fP
.br
To debug the \fBuruk\fP script, invoke uruk as

.di ZV
.in 0
.nf \fC
 sh -x /sbin/uruk
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

this shows what is done, along with executing it\&. (Like an uruk \&'-v\&' option\&.)

If you\&'d rather prefer not to execute, but just watch what would\&'ve been done,
invoke uruk as

.di ZV
.in 0
.nf \fC
 URUK_IPTABLES=\&'echo iptables\&' URUK_IP6TABLES=\&'echo ip6tables\&' uruk
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

(Like an uruk \&'-n\&' option\&.) If you have this statement set, you can run \fBuruk\fP
under a non-priviliged user account\&.

If you\&'d like to test a new \fIrc\fP file before installing it, run something like:

.di ZV
.in 0
.nf \fC

  URUK_CONFIG=/path/to/new/uruk/rc/file uruk
.fi \fR
.in
.di
.ne \n(dnu
.nf \fC
.ZV
.fi \fR

Of course, all these tweaks can be combined\&.
.SH VARIABLES
The uruk script honors the following variables in \fIrc\fP files:

.ZI 2m "\(bu"
\&
.br
"version" Uruk version compatibility of this \fIrc\fP file
.in -2m
.ZI 2m "\(bu"
\&
.br
"loglevel"
.in -2m
.ZI 2m "\(bu"
\&
.br
"iptables" Full pathname of iptables executable\&.
.in -2m
.ZI 2m "\(bu"
\&
.br
"ip6tables" Full pathname of ip6tables executable\&.
.in -2m
.ZI 2m "\(bu"
\&
.br
"interfaces" List of network interfaces\&.
.in -2m
More variables are available\&. For now, you\&'ll have to take a look at the
example \fIrc\fP file in \fC/usr/share/doc/uruk/examples/rc\fP for more details\&.
.SH ENVIRONMENT VARIABLES
See \fBuruk(8)\fP for a list of honored environment variables\&.
.SH FILES
\fC/etc/uruk/rc\fP
.SH SEE ALSO
A well-commented example \fIrc\fP file is in \fC/usr/share/doc/uruk/examples/rc\fP\&.
And see \fBuruk(8)\fP, \fBuruk-save(8)\fP\&.
.SH COPYRIGHT
Copyright (C) 2005, 2007, 2008, 2010, 2011, 2012, 2013 Joost van Baal-Ilić <joostvb-uruk@mdcc\&.cx>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version\&.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE\&. See the
GNU General Public License for more details\&.

You should have received a copy of the GNU General Public License along
with this program\&. If not, see http://www\&.gnu\&.org/licenses/\&.
.SH AUTHOR
Joost van Baal-Ilić <joostvb-uruk@mdcc\&.cx>