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In this post, we will look at WiFi Alliance WPA3-SAE (also known as WPA3-Personal) to replace WPA2-Personal which is susceptible to offline dictionary attack. It is based on  SAE – Simultaneous Authentication of Equals, an password based authentication and key establishment protocol initially introduced in IEEE 802.11s  for mesh networks.

In WPA2-Personal, PMK is derived from the password hence a major weakness of that mechanism (it is very easy to decrypt WPA2-PSK traffic). With WPA3-Personal, PMK is not depend on the password.

WiFi Alliance also introduced WPA3-SAE Transition Mode which we will look at in a later post. Protected Management Frames (PMF) is mandatory in WPA3-SAE mode.

Cisco introduced WPA3 support to its AireOS based controllers from version 8.10.x onward (It is 16.12 onward for IOS-XE based controllers). In this post we use AireOS based WLAN configuration to study WPA3-SAE operation. Pls note that following restriction applies when you configure WPA3-SAE in AireOS 8.10.x version.
IPSK with SAE is not supported
FT with SAE is not supported

Here is the WLAN security configuration on my SSID.

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Here is a packet capture when client is connecting to above SSID. If you look at the frame exchange,you will see it includes 4 Authentication frames, Association Request, Association Response followed by 4-Way Handshake (M1-M4 messages).

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If you look at details of a Beacon frame, you will notice AKM Suite is 00-0F-AC:8 (SAE) under RSNE. Also note that both MFP Required & MFP Capable set to true (In other words management frame protection is mandatory with SAE).

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Cipher Suites
In RSNE, there are three type of cipher suites
1. Group Data Cipher Suite – contain cipher suite selector used by BSS to protect group addressed frames.
2. Pairwise Cipher Suit List– contain series of cipher suite selectors that indicate pairwise cipher suites.
3. Group Management Cipher Suite – cipher suite selector used by BSS to protect group addressed robust management frames.

When management frame protection is negotiated, the negotiated pairwise cipher suite is used to protect individually addressed robust Management frames, and the group management cipher suite is used to protect group addressed robust Management frames.

Cipher Suite Selectors defined in IEEE802.11-2016 standard (table 9.131) shown below. Highlighted Group Data Cipher Suite, Pairwise Cipher Suite (CCMP-128) and Group Management Cipher Suite (BIP-CMAC-128) used in given BSS in my capture.

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AKM Suite
AKM Suite Count field indicate the number of AKM suite selectors in the AKM Suite list field. AKM Suite list field contains a series of AKM suite selectors.

Table below shown AKM suite defined in IEEE 802.11-2016 standard. Highlighted AKM is the one seen in our capture (00-0F-AC:8 which is SAE). Note that 00-0F-AC:9 also for SAE with FT support. WPA3-SAE Certification does not require to have FT support.

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If you look at those Authentication frames, you will notice there are 4 frames in total. Note that Authentication Algorithm number is 3, which is used for SAE. Below shows different Auth Algorithm numbers used in WiFi.

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Prior to exchange SAE auth messages, both side generate a secret element  PWE (Password Element) & two secret values (rand & mask). A group is selected and minimum ECDH-Group 19 support (256 bit) must be there for interoperablity.

First two auth messages are SAE message type  “Commit or 1” (Auth Seq No 1) and other two are SAE message type “Confirm or 2” (Auth Seq No 2). Her is the first Authentication frame details. Commit message contain Grooup ID, a Scalar & an element (FFE) that is produced using PWE (equivalent to public key)

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AP also send an authentication frame that include Group Number & its pubic key (FFE)

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Through “Confirm” messages both side confirm that they have same keys. It includes a hash of the key generated where other party can verify it once received.

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Here is the “Confirm” message goes from AP to STA.

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Once SAE message exchange complete, client send Association Request. Note that AKM 00-0F-AC:8 is used to indicate SAE is in use.

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You will see “successful”status in association response.

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Then AP & STA go through 4 way handshake to derive its encryption keys.  Once encryption keys derive, all data traffic will be encrypted. In this method, there is no way of decrypting that traffic, even if SSID password being compromised.

Here is when AirCheckG2 is trying to connect to this SSID. Since it is not supporting WPA3 (with v4.0 firmware) , it won’t able to connect. Once exchange two open Auth frames, it is sending Association Request with AKM as PSK (00-0F-AC:2).

Note that capture shown below has taken when AG2 connecting to different AP advertising same SSID, CWAP-TEST.

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AP respond with Association Response message with status code unsuccessful (failure code 43 – Invalid AKMP)

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Since most devices still may not support this WPA3-SAE mode of operation, Transition mode implementation is required if you want both WPA3-SAE supported devices and other devices to connect to same SSID. We will look at that mode in next post.

References
1. WPA3, OWE and DPP | Hemant Chaskar | WLPC Phoenix 2019
2.WPA3 support for AireOS 8.10/ IOS-XE 16.12
3. Dragonblood A Security Analysis of WPA3’s SAE Handshake by Mathy Vanhoef
4. https://wificoops.com/2019/07/28/wi-fi-security-enhancements-part-1-wpa3-personal-sae/

Related Posts
1. End of Cisco AireOS?
2. Enhanced Open – Part 1
3. Enhanced Open – Part 2 (Transition Mode)
4. WPA3-SAE Transition Mode
5. WPA3-Enterprise