FIDO2: Phishing-Resistant, But Not Token-Resistant

The ‎article‏ ‎on ‎Silverfort’s ‎blog ‎explores ‎how‏ ‎MITM ‎attacks‏ ‎can‏ ‎bypass ‎FIDO2's ‎phishing-resistant‏ ‎protections. ‎It‏ ‎details ‎the ‎FIDO2 ‎authentication‏ ‎flow,‏ ‎highlights ‎vulnerabilities‏ ‎in ‎session‏ ‎token ‎handling, ‎and ‎provides ‎real-world‏ ‎examples‏ ‎involving ‎Entra‏ ‎ID ‎SSO,‏ ‎PingFederate, ‎and ‎Yubico ‎Playground, ‎concluding‏ ‎with‏ ‎mitigation‏ ‎strategies ‎to‏ ‎enhance ‎security.

FIDO2‏ ‎Background

📌FIDO2 ‎is‏ ‎a‏ ‎modern ‎passwordless‏ ‎authentication ‎standard ‎developed ‎by ‎the‏ ‎FIDO ‎Alliance‏ ‎to‏ ‎replace ‎passwords

📌It ‎aims‏ ‎to ‎protect‏ ‎against ‎phishing, ‎man-in-the-middle ‎(MITM),‏ ‎and‏ ‎session ‎hijacking‏ ‎attacks

📌The ‎authentication‏ ‎flow ‎involves ‎device ‎registration ‎and‏ ‎authentication‏ ‎steps ‎using‏ ‎public ‎key‏ ‎cryptography

FIDO2 ‎Security ‎Features

📌FIDO2 ‎is ‎designed‏ ‎to‏ ‎prevent‏ ‎phishing, ‎MITM,‏ ‎and ‎session‏ ‎hijacking ‎attacks

📌However,‏ ‎the‏ ‎research ‎found‏ ‎that ‎FIDO2 ‎implementations ‎often ‎do‏ ‎not ‎protect‏ ‎session‏ ‎tokens ‎after ‎successful‏ ‎authentication

Attacking ‎FIDO2‏ ‎with ‎MITM

📌The ‎author ‎investigated‏ ‎MITM‏ ‎attacks ‎on‏ ‎identity ‎providers‏ ‎(IdPs) ‎that ‎relay ‎communications ‎between‏ ‎devices

📌While‏ ‎MITM ‎is‏ ‎more ‎difficult‏ ‎with ‎TLS, ‎methods ‎like ‎DNS‏ ‎spoofing,‏ ‎ARP‏ ‎poisoning, ‎and‏ ‎certificate ‎theft‏ ‎can ‎achieve‏ ‎it

📌By‏ ‎performing ‎MITM‏ ‎on ‎the ‎IdP, ‎the ‎attacker‏ ‎can ‎hijack‏ ‎the‏ ‎session ‎token ‎after‏ ‎FIDO2 ‎authentication

Entra‏ ‎ID ‎SSO ‎(Microsoft)

📌Overview: Entra ‎ID‏ ‎SSO‏ ‎is ‎a‏ ‎single ‎sign-on‏ ‎solution ‎that ‎supports ‎various ‎SSO‏ ‎protocols‏ ‎and ‎modern‏ ‎authentication ‎methods,‏ ‎including ‎FIDO2.

📌Vulnerability: The ‎research ‎demonstrated ‎that‏ ‎an‏ ‎attacker‏ ‎could ‎hijack‏ ‎sessions ‎by‏ ‎exploiting ‎the‏ ‎way‏ ‎Entra ‎ID‏ ‎handles ‎session ‎tokens.

📌Attack ‎Method: The ‎attacker‏ ‎does ‎not‏ ‎need‏ ‎to ‎relay ‎the‏ ‎entire ‎authentication‏ ‎process. ‎Instead, ‎they ‎can‏ ‎use‏ ‎a ‎signed‏ ‎token ‎provided‏ ‎by ‎the ‎IdP, ‎which ‎has‏ ‎an‏ ‎expiration ‎time‏ ‎of ‎one‏ ‎hour. ‎This ‎token ‎can ‎be‏ ‎reused‏ ‎within‏ ‎the ‎valid‏ ‎time ‎frame‏ ‎to ‎generate‏ ‎state‏ ‎cookies ‎for‏ ‎a ‎longer ‎period.

📌Example: The ‎native ‎Azure‏ ‎Management ‎portal‏ ‎application‏ ‎does ‎not ‎validate‏ ‎the ‎token‏ ‎granted ‎by ‎the ‎SSO,‏ ‎allowing‏ ‎an ‎attacker‏ ‎to ‎use‏ ‎a ‎stolen ‎token ‎to ‎gain‏ ‎unauthorized‏ ‎access.

PingFederate

📌Overview: PingFederate ‎is‏ ‎an ‎SSO‏ ‎solution ‎that ‎uses ‎third-party ‎adapters‏ ‎to‏ ‎perform‏ ‎authentication. ‎These‏ ‎adapters ‎can‏ ‎be ‎chained‏ ‎into‏ ‎an ‎authentication‏ ‎policy ‎flow.

📌Vulnerability: The ‎research ‎found ‎that‏ ‎if ‎the‏ ‎relying‏ ‎party ‎developer ‎does‏ ‎not ‎validate‏ ‎the ‎OIDC ‎token ‎(or‏ ‎SAML‏ ‎Response), ‎the‏ ‎MITM ‎attack‏ ‎can ‎be ‎successful.

📌Attack ‎Method: The ‎attack‏ ‎exploits‏ ‎the ‎weakest‏ ‎link ‎in‏ ‎the ‎authentication ‎chain. ‎Since ‎the‏ ‎SSO‏ ‎protocols‏ ‎rely ‎on‏ ‎granting ‎tokens‏ ‎that ‎can‏ ‎be‏ ‎reused ‎by‏ ‎different ‎devices, ‎an ‎attacker ‎can‏ ‎hijack ‎the‏ ‎session‏ ‎by ‎stealing ‎these‏ ‎tokens.

📌Example: The ‎PingOne‏ ‎adapter ‎can ‎be ‎used‏ ‎with‏ ‎FIDO2 ‎capabilities.‏ ‎If ‎the‏ ‎OIDC ‎token ‎is ‎not ‎validated,‏ ‎an‏ ‎attacker ‎can‏ ‎bypass ‎FIDO2‏ ‎protections ‎and ‎gain ‎unauthorized ‎access.

Yubico‏ ‎Playground

📌Overview: Yubico‏ ‎Playground‏ ‎is ‎a‏ ‎testing ‎environment‏ ‎for ‎FIDO‏ ‎security‏ ‎features ‎and‏ ‎keys.

📌Vulnerability: The ‎research ‎showed ‎that ‎a‏ ‎simple ‎session‏ ‎cookie‏ ‎generated ‎after ‎FIDO2‏ ‎authentication ‎can‏ ‎be ‎exploited.

📌Attack ‎Method: There ‎is‏ ‎no‏ ‎validation ‎on‏ ‎the ‎device‏ ‎that ‎requested ‎the ‎session ‎cookie.‏ ‎Any‏ ‎device ‎can‏ ‎use ‎this‏ ‎cookie ‎until ‎it ‎expires, ‎allowing‏ ‎an‏ ‎attacker‏ ‎to ‎bypass‏ ‎the ‎authentication‏ ‎step.

📌Example: ‎By‏ ‎acquiring‏ ‎the ‎session‏ ‎cookie, ‎an ‎attacker ‎can ‎access‏ ‎the ‎user’s‏ ‎private‏ ‎area ‎and ‎remove‏ ‎the ‎security‏ ‎key ‎from ‎the ‎user’s‏ ‎profile,‏ ‎demonstrating ‎a‏ ‎straightforward ‎session‏ ‎hijacking ‎scenario