DOKK / manpages / debian 10 / uruk / uruk-rc.5.en
uruk-rc(5) FILE FORMATS uruk-rc(5)


uruk-rc - uruk resource file, defining access policy


/etc/uruk/rc


rc is a shell script snippet, sourced in uruk by /bin/sh.

rc lists IP addresses, allowed to use services.


default
The simplest valid rc file is the empty file. This rc file blocks all TCP and UDP connection attempts to services on our host: this is the default behaviour.

simplest
The simplest rc file which does allow traffic to our services looks like e.g.:




 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"



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


realistic
  

  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 rc:



  






 # 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 






autodetect-ips
  

  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 nic, and each found IPv4 and
    IPv6 address and network, sets variables
    ip_nic_default,
    ip6_nic_default,
    net_nic_default and
    net6_nic_default . Then it calls ip(8) and
    adds any other found nic, ip and net
    triplets (for IPv4 and, for IPv6, only addresses in scope
    "global").


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


another example
  

  For an even more reasonable rc file, look at the well-commented example
    rc file in /usr/share/doc/uruk/examples/rc.










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



  






 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'






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.










Uruk offers hooks for inserting your own code between iptables
    invocations. Examples will show the usefulness of these hooks.


allowing broadcasts
  

  In rc, there is:



  






 rc_b=$etcdir/bootp






while the file bootp reads



  






 iptables -A INPUT -m state --state NEW -i eth0 \


   --protocol udp --destination-port bootps -j ACCEPT






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


allowing non-matching returntraffic
  

  In rc there is:



  






 rc_d=$etcdir/dns






while the file dns reads



  






  for source in 10.5.0.27 10.56.0.40


  do


    $iptables -A INPUT -i eth0 --protocol udp \


      --source "$source" --source-port domain \


      --destination "$ip_eth0" \


      --destination-port 30000: -j ACCEPT


  done






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


allowing NAT
  

  In rc there is:



  






 rc_a=${etcdir}/nat






while the file nat reads



  






  $iptables -t nat -A POSTROUTING \


    --out-interface eth0 -j SNAT \


    --to-source $ip_eth0






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


allowing IPv6 tunneling
  

  In rc there is:



  






 rc_b=${etcdir}/proto_41






while the file proto_41 reads



  






 $iptables -A INPUT -i ppp0 --protocol 41 --destination $ip_ppp0 -j ACCEPT






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


allowing any traffic on an interface
  

  In rc there is:



  






 interfaces_unprotect="lo eth2"






This allows any traffic on eth2 (and on lo, the default),
    including any ICMP packets and packets from any source address.


using multiple hooks at one entry point in the main uruk
    process
  

  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
    uruk(8) (or the uruk source) to find out which hook (there are
    hooks rc_a, rc_b, ... , rc_i) to use.










Uruk supports situations where a network interface has more than
    one IP address attached. Variables ips_nic and
    bcasts_nic are used for this.


If ips_nic is set, e.g. like



  






 ips_eth0="ip0 ip1 ip2"






we assume multiple (three in this example) IPs are assigned to
    eth0. If this variable is not set only one IP is supported on
    eth0.


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



  






 ip_eth0_ip0="137.56.247.16"






(If you're used to the Linux ifconfig(8) output, you could use the
    name ip for eth0, and ip0 for eth0:0.) The
    ports, services and sources variables look like
  e.g.



  






 services_eth0_ip2_tcp=local


 ports_eth0_ip2_tcp_local=smtp


 sources_eth0_ip2_tcp_local=$localnet






and, similarly,



  






 net_eth0_ip1=192.168.0.0/16






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



  






 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"






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:



  






 ip_eth0_ip0="137.56.247.16 137.56.247.17 137.56.247.18"
















Uruk has support for logging network packets, and for debugging
    the uruk script.


Logging
  

  By default, uruk logs denied packets. This is adjustable using the
    loglevel variable. The settings are:



  

  •
  

  "zero": be silent; do not log any packet. rc file features
    loglevel=10.
  

  

  

  •
  

  "low": log denied packets, which are targeted at one of our IPs.
    rc file features loglevel=30.
  

  

  

  •
  

  "medium": log denied non-broadcast packets. This is the default:
    loglevel is unset or rc file features loglevel=50.
  

  

  

  •
  

  "fascist": log all packets. rc file features
    loglevel=90.
  




Debugging
  

  To debug the uruk script, invoke uruk as



  






 sh -x /sbin/uruk






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



  






 URUK_IPTABLES='echo iptables' URUK_IP6TABLES='echo ip6tables' uruk






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


If you'd like to test a new rc file before installing it,
    run something like:



  






  URUK_CONFIG=/path/to/new/uruk/rc/file uruk






Of course, all these tweaks can be combined.










The uruk script honors the following variables in rc
  files:



  

  •
  

  "version" Uruk version compatibility of this rc file
  

  

  

  •
  

  "loglevel"
  

  

  

  •
  

  "iptables" Full pathname of iptables executable.
  

  

  

  •
  

  "ip6tables" Full pathname of ip6tables executable.
  

  

  

  •
  

  "interfaces" List of network interfaces.
  

  More variables are available. For now, you'll have to take a look at the
    example rc file in /usr/share/doc/uruk/examples/rc for more
    details.










See uruk(8) for a list of honored environment
  variables.










/etc/uruk/rc










A well-commented example rc file is in
    /usr/share/doc/uruk/examples/rc. And see uruk(8),
    uruk-save(8).










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/.










Joost van Baal-Ilić <joostvb-uruk@mdcc.cx>







  

    21 јан 2019
    uruk-rc 20190121