EapSimAka
NOTE: The described EAP patch will only work on a real Android Smartphone which has an up and running SmartCardAPI with UICC support and PCSC System Service.
EAP-SIM is a mechanism for authentication and session key generation using a GSM authentication algorithm on client and network side. EAP-AKA is like EAP-SIM but uses the authentication algorithms on an USIM.
EAP-SIM is specified in RFC 4186.
EAP-AKA is specified in RFC 4187.
Specifications about EAP can be found here and here.
An overview how a WLAN with EAP authentication may look like is shown below:
To run an EAP-SIM/AKA authentication you will need a client as wpa_supplicant which has access to a (U)SIM. The WLAN access point on the network has to support EAP (which is often transcribed as WPA(2)-RADIUS or WPA(2)-ENTERPRISE). The WLAN AP has to have access to a RADIUS server who handles the authentication and session key generation. The RADIUS server in a productive environment needs for EAP-SIM/AKA access to the home location register (HLR) of the MNO where the (U)SIMs are registered. For testing a file with precreated values for authentication is sufficient.
The next picture shows simplified the data flow during the authentication process.
In order to run EAP-SIM/AKA on an Android smartphone it is necessary to adapt two parts of the sources:
- the wpa_supplicant and
- the Settings.apk
To get access to the (U)SIM it is necessary to enable the PC/SC interface and integrate the SmartCard API with UICC support.
The EAP-SIM/AKA patch was tested against Android 2.3.5_r1, the SmartCard API 2.2.2 and the PCSC System Service 0.9.7.
For the wpa_supplicant the use of the PCSC interface has to be enabled and the functions which encapsulate the PCSC interface have to be adapted so that they can handle the responses from the SmartCardService, since the original sources of the wpa_supplicant expected responses from the (U)SIM according to the T=0 protocol, but the SmartCardService returns response data according to T=1.
To give the user the possibility to enable EAP-SIM or EAP-AKA on his Smartphone it is necessary to extend the WiFi Dialog
where it is possible to select the EAP methods.
The WiFi Dialog is located in the package Settings.apk.
Now the entries SIM and AKA are now available and selectable as EAP-Method.
When selecting SIM or AKA the other fields like Phase 2 Authentication, CA-Cerificate and so on can be left empty
or by their default values.
Download the EAP-SIM/AKA patch and extract the content.
Apply the patch with
patch -p1 -i eap-sim-aka_0.4.1.patch
in the root directory of your Android Sources. Build the system how it is shown in BuildingTheSystem.
The EAP-AKA support for freeradius was introduced by a patch for Version 1.1.4. This patch is not available for Version 2 of freeradius server.
We have merged the old EAP-AKA patch and added some more features to the rlm_sim_files module so that it can provide the EAP-SIM and EAP-AKA module
with the correct data and keys.
The result is a patch was developed with version 2.1.9 of the freeradius server but it might also work for other 2.1.x versions.
NOTE: This patch will only work for EAP-AKA if on the USIM the sequence number check is disabled,
since the AUTN provided by rlm_sim_files is constant. Therefore check EF_AuthAlgo on your USIM.
On a ubuntu machine get freeradius sources via (first change to the directory where you want to store the sources)
apt-get source freeradius
Get the build dependencies
apt-get build-dep freeradius
A freeradius source directory will be created e.g. freeradius-2.1.9-dfsg.
Go to the source directory.
cd freeradius-2.1.9-dfsg
Get the freeradius patch archive
and extract the content.
Apply the patch within the freeradius source directory of freeradius.
You may want to try it first with option --dry-run to check if everything will do fine.
patch -p2 -i freeradius-2.1.9-dfsg_eap-sim-aka-0.1.patch
Build the deb packages:
debian/rules binary
Install the packages
sudo deb -i ../libfreeradius2_2.1.9+dfsg-sch02_i386.deb
sudo deb -i ../freeradius_2.1.9+dfsg-sch02_i386.deb
sudo deb -i ../freeradius-common_2.1.9+dfsg-sch02_all.deb
Since the rlm_sim_files module is not build by the debian packages routines. It has to be built and copied manually.
Change to and run make
cd ./src/modules/rlm_sim_files
make
Copy the libraries and create a symbolic link
sudo cp ./.libs/rlm_sim_files-2.1.9.so /usr/lib/freeradius
sudo ln -s /usr/lib/freeradius/rlm_sim_files-2.1.9.so /usr/lib/freeradius/rlm_sim_files.so
(Re-)Start the freeradius server with:
sudo /etc/init.d/freeradius restart
All configuration files for freeradius are located in /etc/freeradius and below.
Add to or change clients.conf that it contains
client 192.168.0.0/16 {
secret = eap-sim
shortname = eap-sim
}
The secret and shortname can be chosen freely, but you have to setup on your WLAN AP the same secret. e.g. on a LinkSys WRT54GL
In the config directory /etc/freeradius/modules create a file sim_files with following content:
sim_files {
simtriplets = "/etc/freeradius/simtriplets.dat"
}
In the config file eap.conf add at the end but before the closing }
aka {
}
sim {
}
In the config file default add
sim_files
directly before
eap {
ok = return
}
After changes on the configuration files a restart of the server is necessary.
Create the file /etc/freeradius/simtriplets.dat with the content from your (U)SIMs you want to use.
Sample of a simtriplets.dat file
# IMSI RAND SRES Kc
SIM,1262074920549791,64BC736EF7684de1921F9C9C0E0679E2,0B7e4e4b,D2119f41D8840400
SIM,1262074920549791,97D0C531F2A84000ACB5E4F966157908,181c8ac1,E2f6976a226bc800
SIM,1262074920549791,1E4FD2861D0848a499C91162234B255C,211056b1,8Bbdd2385B3a0400
#
SIM,0262074920549791,64BC736EF7684de1921F9C9C0E0679E2,0B7e4e4b,D2119f41D8840400
SIM,0262074920549791,97D0C531F2A84000ACB5E4F966157908,181c8ac1,E2f6976a226bc800
SIM,0262074920549791,1E4FD2861D0848a499C91162234B255C,211056b1,8Bbdd2385B3a0400
# IMSI RAND RES AUTN IK CK
AKA,0262073961704408,9FDDC72092C6AD036B6E464789315B78,F553BBC042452202,478412477BFF61DFD5BE5A85664C0820,359CF653FDC8BD365AD32A264811B7EE,CA31C86C64F1C274565CFA7966E2CE0D
The first triplet block ist for EAP-SIM on a SIM card, the second block is for EAP-SIM on a USIM card and the last line contains the values for EAP-AKA of a USIM card.
It is mandatory to have at least 3 different records for one IMSI when it is used for EAP-SIM.
It is not possible to use a single USIM for EAP-AKA and EAP-SIM at the same time. Only one of the methods may be active, the other method can be disabled by adding a # as prefix.
The EAP-SIM values can be creates using the tool asgm which kann be found here http://agsm.sourceforge.net/download.html
