Cellular Network Infrastructure » cni-legacy » OpenBSC

PageOutline = Information on the WRTU54G UMA TA =

Getting shell / console access

The easiest part is to flash a modified firmware image that removes the root password from the /etc/passwd file in the squashfs.

You can then access the serial console and log in as root without password.

Changing the SEGW / GANC address

On the shell of the device, change to the /nv directory and edit the two lines in rc.conf for UMA_SGW and UMA_UNC to: {{{
UMA_SGW="my.segw.host.name"
UMA_UNC="my.unc.host.name"
}}}

Then, use the {{{rawaccess -a rc.conf}}} command to store the changes to flash and reboot the system.

Enabling more logging

In /nv/rc.conf: {{{
LOG_ENABLE="1"
UMALOG_ENABLE="on"
UMA_LOG_SIZE="1"
}}}

Then, use the {{{rawaccess -a rc.conf}}} command to store the changes to flash and reboot the system.

Adding a new CA Certificate

While modifying the firmware, add your new CA root certificate in DER format to /ramdisk_copy/etc/kineto/ and then add the filename
and path into a new line in /ramdisk_copy/etc/kineto/init_ike.cfg, like this: {{{
ike ca /etc/kineto/my_new_ca.der
}}}

Furthermore, edit /etc/rc.d/init.d/umaset and /etc/rc.d/init.d/RJ11_recovery to each include a line like this: {{{
echo "ike ca /etc/kineto/my_new_ca.der" >> $IKE_CONF
}}}

Enabling telnet

Using the toolchain included in the Linksys WRTU54G GPL release, you can cross-compile utelnetd for a compatible uclibc: {{{
./utelnetd-0.1.11 $ make CC=mipsel-linux-gcc
mipsel-linux-gcc -I. -pipe -DSHELLPATH=\"/bin/login\" -Wall -fomit-frame-pointer -c -o utelnetd.o utelnetd.c
mipsel-linux-gcc -I. -pipe -DSHELLPATH=\"/bin/login\" -Wall -fomit-frame-pointer utelnetd.o -o utelnetd
strip --remove-section=.comment --remove-section=.note utelnetd
./utelnetd-0.1.11 $
}}}

You can then include this utelnetd binary into the squashfs image to /usr/sbin/utelnted.

Furthermore, you have to edit /etc/rc.d/rc.proprietary and change the line {{{
[ "`uname -ar | grep diag`" ] && /usr/sbin/utelnetd&
}}}
into {{{
usr/sbin/utelnetd&
}}}
to unconditionally start the telnet daemon at every boot. Alternatively, you can set {{{
hostname="diag"
}}}
in /nv/rc.conf.

= Setting up a SEGW =

The SEGW needs to * allocate a virtual IP to the remote end from a local pool * use EAP-SIM to authenticate the peer, using tuples (IMSI/RAND/SRES/Kc) * authenticate itself using a certificate that has been signed by the CA certificate installed on the WRT54U * provide at least one DNS server via IKEv2 attributes to the peer

compiling strongswan

You can use strongswan-4.4.1 and use the following compile-time configure options: {{{
--enable-eap-radius --enable-eap-aka --enable-sqlite --enable-eap-sim --enable-eap-sim-file --enable-eap-simaka-sql
}}}

strongswan configuration files

=== /etc/strongswan.conf ===

{{{
charon {
threads = 16
plugins {
attr {
dns = 213.95.46.69
}
}
}

libhydra {
plugins {
attr-sql {
database = sqlite:///etc/ipsec.d/ipsec.db
}
}
}
}}}

=== /etc/ipsec.conf === {{{
config setup
charonstart=yes
plutostart=no
charondebug="ike 2, knl 2, net 2, cfg 2"

conn %default
ikelifetime=60m
keylife=20m
rekeymargin=3m
keyingtries=1
keyexchange=ikev2

conn uma-segw
left=real.public.ip.of.segw
leftsubnet=10.0.0.0/8
leftcert=segw_cert.pem
leftauth=pubkey
rightauth=eap-sim
right=%any
rightsourceip=%hostpool
rightsendcert=never
auto=add
}}}

=== /etc/ipsec.d/triplets.dat ===

Populate this with SIM authentication triplets like this (identity derived of IMSI, RAND, SRES, Kc): {{{
1901700000000402@uma.mnc700.mcc901.3gppnetwork.org,00000000000000000000000000000000,11111111,2222222222222222
}}}

=== /etc/ipsec.secrets === {{{
: RSA /etc/ipsec.d/private/segw_key_raw.pem
}}}

=== /etc/ipsec.d/certs/segw_cert.pem ===
This is the PEM file of your certificate for the SEGW, using the CN of the FQDN.

=== /etc/ipsec.d/cacerts/my_ca.pem ===
This is the CA root certificate of the CA that has issued your segw_cert.pem

=== /etc/ipesc.d/private/segw_key_raw.pem ===
This is the '''raw''' RSA private key for your segw_cert.pem, and is '''not PKCS8'''.

==== make sure your private key is not PKCS8 ====

The default CA.pl script of opensl generates private keys in PKCS8 format, which is not supported
by charon of OpenSWAN. you have to convert the PKCS8 into raw RSA files like this: {{{
openssl pkcs8 -nocrypt < my_privatekey.pem > my_privatekey_raw.pem
}}}