[Bug 3979] udhcpc should filter out malicious hostnames passed in option 0x0c

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=3979

--- Comment #15 from danny at mellanox.com 2014-04-17 16:20:58 UTC ---
Such dhcpd config (irrelevant lines are skipped):

nis-domain "some"; 
subnet-mask 255.255.0.0; 
broadcast-address 172.*.255; 
domain-name "siteX.sub.domain"; 
domain-search
"siteX.sub.domain","sub.domain","domain","other.sub.domain","other.domain";
domain-name-servers 10.*,10.*,10.*,10.*; 
ntp-servers 10.*; 
routers 172.*;

Generates following leases on different OS:

from CentOS 6.x:

lease {
  interface "eth0";
  fixed-address 172.*;
  filename "pxelinux.0";
  option subnet-mask 255.255.0.0;
  option routers 172.*;
  option dhcp-lease-time 36000;
  option dhcp-message-type 5;
  option domain-name-servers 10.*,10.*,10.*,10.*;
  option dhcp-server-identifier 10.*;
  option domain-search "siteX.sub.domain.", "sub.domain.", "domain.",
"other.sub.domain.", "other.domain.";
  option nis-domain "some";
  option nis-servers 10.*;
  option ntp-servers 10.*;
  option broadcast-address 172.*.255;
  option host-name "some21";
  option domain-name "siteX.sub.domain";
  renew 4 2014/04/17 18:31:38;
  rebind 4 2014/04/17 23:19:29;
  expire 5 2014/04/18 00:34:29;
}


from CentOS 5.x:

lease {
  interface "eth0";
  fixed-address 172.*;
  filename "pxelinux.0";
  option subnet-mask 255.255.0.0;
  option routers 10.*;
  option dhcp-lease-time 1209600;
  option dhcp-message-type 5;
  option domain-name-servers 10.*,10.*,10.*;
  option dhcp-server-identifier 10.*;
  option nis-domain "some";
  option nis-servers 10.*;
  option ntp-servers 10.*;
  option broadcast-address 172.*.255;
  option host-name "some21";
  option domain-name "siteX.sub.domain";
  renew 3 2014/04/23 03:08:45;
  rebind 2 2014/04/29 21:56:57;
  expire 4 2014/05/01 15:56:57;
}

As you can see, 5.x stuff even not asking for domain-search stuff.

Moreover, this command should bring needed, but it won't:

# dhclient -R
subnet-mask,broadcast-address,routers,domain-name,domain-name-servers,host-name,nis-domain,nis-servers,domain-search
eth0

lease {
  interface "eth0";
  fixed-address 172.*;
  filename "pxelinux.0";
  option subnet-mask 255.255.0.0;
  option routers 10.*;
  option dhcp-lease-time 1209600;
  option dhcp-message-type 5;
  option domain-name-servers 10.*,10.*,10.*;
  option dhcp-server-identifier 10.*;
  option domain-search ;    <=========== empty...
  option nis-domain "some";
  option nis-servers 10.*;
  option ntp-servers 10.*;
  option broadcast-address 172.*.255;
  option host-name "some21";
  option domain-name "siteX.sub.domain";
  renew 3 2014/04/23 21:41:26;
  rebind 2 2014/04/29 21:52:11;
  expire 4 2014/05/01 15:52:11;
}

And, even we add following to dhcpd config, it still ignored all together in
5.x:

option domain-forced-list code 119 = string;
domain-forced-list
"siteX.sub.domain","sub.domain","domain","other.sub.domain","other.domain";

So, following advices to use "right options", we hitting even more problems and
incompatibilities in different OS.

-- 
Configure bugmail: https://bugs.busybox.net/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.