EAP-TTLS-EAP-MD5-Challenge

What is Expansion of EAP-TTLS-EAP-MD5-Challenge?

Extensible Authentication Protocol - Tunneled Transport Layer Security - Extensible Authentication Protocol - Message Digest 5 Challenge.

What is EAP-TTLS-EAP-MD5-Challenge?

EAP-TTLS-EAP-MD5-Challenge is an authentication method that combines EAP-TTLS to establish a secure TLS tunnel and uses EAP-MD5-Challenge as the inner authentication mechanism to verify user credentials through an MD5 hash challenge-response method inside the encrypted tunnel.

Why is EAP-TTLS-EAP-MD5-Challenge useful?

  • Provides secure transmission of legacy MD5 challenge credentials inside a protected TLS tunnel.

  • Protects password or challenge-response data from eavesdropping.

  • Allows use of older authentication methods in modern secure environments.

  • Useful where client certificates are not deployed but strong encryption is needed.

How it works?

  1. A TLS tunnel is established between the client and authentication server.

  2. Inside the tunnel, the server sends an MD5 challenge to the client.

  3. Client responds with a hash computed over the challenge and its password.

  4. Server validates the hash and authenticates the client.

  5. Upon success, cryptographic keys are generated for the session.

Where is EAP-TTLS-EAP-MD5-Challenge used?

  • Enterprise Wi-Fi networks requiring legacy password-based authentication.

  • VPN environments supporting older EAP methods.

  • Scenarios requiring a balance between legacy compatibility and secure tunneling.

Which OSI layer does this protocol belong to?

  • Application Layer (Layer 7).

IS EAP-TTLS-EAP-MD5-Challenge windows specific?

  • No, it’s platform-independent but requires supplicant support.

IS EAP-TTLS-EAP-MD5-Challenge Linux Specific?

  • No, supported by Linux supplicants like wpa_supplicant.

Which Transport Protocol is used by EAP-TTLS-EAP-MD5-Challenge?

  • EAP over LAN (EAPOL) for client-authenticator communication.

  • RADIUS (UDP) protocol between authenticator and authentication server.

Which Port is used by EAP-TTLS-EAP-MD5-Challenge?

  • UDP port 1812 (RADIUS Authentication).

Is EAP-TTLS-EAP-MD5-Challenge using Client server model?

  • Yes, involves the supplicant (client), authenticator (access point), and authentication server.

Whether EAP-TTLS-EAP-MD5-Challenge protocol uses certificates?

  • Server certificates are mandatory to establish the TLS tunnel.

  • Client certificates are generally not required.

How many frame exchanges are seen during connection for EAP-TTLS-EAP-MD5-Challenge protocol?

  • Multiple EAPOL frames occur due to TLS handshake and inner MD5 challenge/response.

  • Usually several dozen frames during complete authentication.

Whether EAP-TTLS-EAP-MD5-Challenge Protocol uses client certificates?

  • No, client authentication is via MD5 challenge-response inside the TLS tunnel.

Whether EAP-TTLS-EAP-MD5-Challenge Protocol uses Server Certificates?

  • Yes, required for TLS tunnel establishment.

IS EAP-TTLS-EAP-MD5-Challenge Protocol depends on TCP?

  • Not directly; EAP/EAPOL are independent of TCP.

  • TLS handshake runs over EAPOL (Layer 2).

  • RADIUS uses UDP.

IS EAP-TTLS-EAP-MD5-Challenge Protocol depends on UDP?

  • Yes, RADIUS typically operates over UDP.

What are the roles involved when testing EAP-TTLS-EAP-MD5-Challenge Protocol?

  • Client/Supplicant (device connecting).

  • Authenticator (e.g., Access Point).

  • Authentication Server (e.g., FreeRADIUS).

  • Network monitoring tools to capture and analyze frames.

Does EAP-TTLS-EAP-MD5-Challenge Protocol work with free radius server on Linux?

  • Yes, FreeRADIUS supports EAP-TTLS with inner EAP-MD5.

Does EAP-TTLS-EAP-MD5-Challenge Protocol work with Internal radius server of hostapd?

  • Limited support; external RADIUS servers are preferred for EAP-TTLS.

What is the RFC version use for EAP-TTLS-EAP-MD5-Challenge Protocol?

  • EAP-TTLS: RFC 5281.

  • EAP-MD5: RFC 3748.

During Connection Procedure which EPoL Packets are encrypted?

  • The inner EAP-MD5 challenge-response messages are encrypted inside the TLS tunnel.

  • TLS handshake messages are initially unencrypted but establish the secure tunnel.

Can you Explain different stages of Connection Procedure for EAP-TTLS-EAP-MD5-Challenge Protocol?

  1. Client and server perform a TLS handshake to establish a secure tunnel.

  2. Server sends an MD5 challenge inside the tunnel.

  3. Client computes and returns the MD5 hash response.

  4. Server verifies the response and authenticates the client.

  5. Keys (PMK) are derived for subsequent secure communication.

What is the final output of Connection Procedure?

  • Authentication success or failure.

  • Pairwise Master Key (PMK) for encrypting wireless data.

  • Network access granted upon success.

What is the format of the key generate after the connection procedure?

  • 256-bit Pairwise Master Key (PMK).

Where the use of PMK generated by the Connection Procedure?

  • Used in the 4-way handshake to derive temporal encryption keys.

  • Secures data transmission between client and access point.

  • In this section, you are going to learn

  • Terminology

  • Version Info

  • rfc details

  • Run Free RADIUS

FreeRADIUS: Download latest freeradius source code

Note

  • Make sure internet is available in laptop to download freeradius package

test:~$ wget https://github.com/FreeRADIUS/freeradius-server/archive/v3.0.x.tar.gz

FreeRADIUS: Extract freeradius

test:~$ tar -zvf v3.0.x.tar.gz

FreeRADIUS: Change directory to Radius server

test:~$ cd freeradius-server-3.0/

FreeRADIUS: Check the current working directory using pwd command

Note

  • Make sure your current working directory is freeradius-server-3.0

test:~$ pwd
/home/test/freeradius-server-3.0

FreeRADIUS: Open debian/rules and add this line –without-rml_sql_iodbc above –without-rlm_eap_ikev2

test:~$ vim debian/rules
--without-rml_sql_iodbc \
--without-rlm_eap_ikev2 \

FreeRADIUS: Configure for Compilation

test:~$ ./configure

FreeRADIUS: Build the Radius server

test:~$ make

FreeRADIUS: Go to raddb folder (all radius server/client files and certificates and keys will be generated here)

test:~$ cd /usr/local/etc/raddb

FreeRADIUS: Open clients.conf file and verify localhost client is present else add your own client like below

test:~$ sudo vi clients.conf

client 192.168.56.10{
ipaddr = 192.168.56.10
secret = testing123
}  

FreeRADIUS: Open users file and uncomment below two lines or add

test:~$ sudo vi users

bob 	Cleartext-Password := "testing123"
 	Reply-Message := "Hello, %{User-Name}"

FreeRADIUS: Set default_eap_type=tls in eap file located in /usr/local/etc/raddb/mods-enabled

test:~$ sudo vi /usr/local/etc/raddb/mods-enabled/eap

default_eap_type=ttls

FreeRADIUS: Start radius server

test:~$ sudo radiusd -X
  • Run AP mode operation with hostapd

AP : Download hostapd

Note

  • Make sure internet is available in laptop to download hostapd package

test:~$ wget http://w1.fi/releases/hostapd-2.9.tar.gz

AP: Install required packages

test:~$ sudo apt install libnl-genl-3-dev libnl-3-dev libdbus-glib-1-dev

AP : Extract hostapd

test:~$ tar -xzvf hostapd-2.9.tar.gz

AP : Change directory to hostapd

test:~$ cd hostapd-2.9/hostapd/

AP : Check the current working directory using pwd command

Note

  • Make sure your current working directory is hostapd

test:~$ pwd
/home/test/hostapd-2.9/hostapd

AP : Copy the contents of defconfig file to .config file

Note

  • .config file is required for make to start compilation of hostapd

test:~$ sudo cp defconfig .config

AP : Complile hostapd

Note

  • Compile hostapd by running make command

test:~$ make

AP : Check for the binaries created

Note

  • Make sure hostapd and hostapd_cli are present

test:~$ ls
hostapd
hostapd_cli

AP : Create a hostapd.conf file in /etc/hostapd folder with below content

test:~$ sudo vim /etc/hostapd/hostapd.conf

ctrl_interface=/var/run/hostapd
interface=enp0s8
driver=wired
logger_stdout=1
logger_stdout_level=1
debug=2
ieee8021x=1
eap_server=0
eap_user_file=/etc/hostapd/eap_user
eap_reauth_period=3600
use_pae_group_addr=1
auth_algs=1
auth_server_addr=127.0.0.1
auth_server_port=1812
auth_server_shared_secret=testing123
acct_server_addr=127.0.0.1
acct_server_port=1812
acct_server_shared_secret=testing123
macaddr_acl=0
ca_cert=/usr/local/etc/raddb/certs/ca.pem
server_cert=/usr/local/etc/raddb/certs/server.crt
private_key=/usr/local/etc/raddb/certs/server.p12
private_key_passwd=whatever 

AP : Create a file eap_user in /etc/hostapd/ folder with below content

test:~$ sudo vim /etc/hostapd/eap_user

AP : Run hostapd

test:~$ sudo ./hostapd /etc/hostapd/hostapd.conf
enp0s8: interface state UNINITIALIZED->ENABLED
enp0s8: AP-ENABLED

STA : Download wpa_supplicant

Note

  • Make sure internet is available in laptop to download supplicant package

test:~$ wget https://w1.fi/releases/wpa_supplicant-2.9.tar.gz

STA: Install required packages

test:~$ sudo apt install libnl-genl-3-dev libnl-3-dev libdbus-glib-1-dev

STA : Extract wpa_supplicant

test:~$ tar -xvf wpa_supplicant-2.9.tar.gz

STA : Change directory to wpa_supplicant

test:~$ cd wpa_supplicant-2.9/wpa_supplicant/

STA : Check the current working directory using pwd command

Note

  • Make sure your current working directory is wpa_supplicant

test:~$ pwd
/home/test/wpa_supplicant-2.9/wpa_supplicant

STA : Copy the contents of defconfig file to .config file

Note

  • .config file is required for make to start compilation of supplicant

test:~$ cp defconfig .config

STA : Compile wpa_supplicant

Note

  • Compile supplicant by running make command.

test:~$ make

STA: You might get errors while make regarding openssl headers in that case install the openssl headers and then do make clean and then do make again.

test:~$ sudo apt install libssl-dev
test:~$ make clean
test:~$ make

STA : Check for the binaries created

Note

  • Make sure wpa_supplicant and wpa_cli are present

test:~$ ls
wpa_supplicant
wpa_cli

STA: Copy required certificates from hostapd to wpa_supplicant

STA : Create wpa_supplicant.conf

test:~$ sudo vim wpa_supplicant.conf

ctrl_interface=/run/wpa_supplicant
update_config=1
network={
key_mgmt=WPA-EAP
eap=TTLS
phase2="autheap=MD5"
identity="bob"
password="testing123"
}

STA : Run wpa_supplicant

test:~$ sudo ./wpa_supplicant -D wired -i enp0s8 -c wpa_supplicant.conf
enp0s8: CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully

STA: Test

test:sudo ./wpa_cli -i enp0s8
> status
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