11 comments

  • nl 1 hour ago
    Well at least someone could log in using Entra ID!
  • userbinator 5 hours ago
    failed to properly validate the originating tenant

    One wonders whether those who designed all this ever considered what that field in the token is for.

    The word "tenant" is also very telling --- you're just renting, and the "landlord" always has the keys.

    • nine_k 3 hours ago
      It's even worse: "Because of the nature of these Actor tokens, they are not subject to security policies like Conditional Access". This goes against all principles of good security design. A token that gives root access instead of specifying a particular action allowed just invites misuse, erroneous or malicious.

      I would expect these tokens to be like JWT or macaroons, carrying specific permissions within specific bounds / tenants. Alas.

      • milkshakes 2 hours ago
        well, you're in luck, they are JWTs in fact. JWTs in JWTs, so extra secure.
        • Freak_NL 2 minutes ago
          And of course, because the inner JWT is already signed, why bother signing the outer one? Just validate the inner one!

          I'm feeling sorry for those poor abused JWTs in this vulnerability.

      • Nursie 2 hours ago
        They are!

        But the systems that have been built around them are bad. Firstly in issuing these ‘root’ tokens at all, and secondly in not checking the claims properly.

        A JWT is only as good as the systems it’s used by.

  • darkamaul 1 hour ago
    Impressive work!

    This makes me wonder if Microsoft’s commitment to long-term support is part of the problem: instead of deprecating these ancient APIs they keep them on life-support, but forget some "regression-test" on how they interact with the shiny new surfaces.

    Feels like P0’s Windows Registry talks, most of the vulns weren’t in the new code, they were in the how legacy behaviors interacted with newer features.

    • tonyhart7 10 minutes ago
      Microsoft also forced to keep these legacy code tbh

      You see, most enterprise client with big enough contract can force to do this and MS need to support this customer until they migrate or if they ever be at all

      I may argue for any big legacy enterprise software, its easier to rewrite the damn whole thing than to support the legacy code forever but they cant do that even if they have motivation/resource

  • pcj-github 4 hours ago
    Absolutely insane. Security so weak, it seems like you discovered an intentional backdoor.
    • cookiengineer 4 hours ago
      My NSL detector is off the charts here.
    • otabdeveloper4 2 hours ago
      > impersonation tokens, called “Actor tokens”, that Microsoft uses in their backend for service-to-service (S2S)

      Literally every single "security" framework uses God-mode long-lived tokens for non-human identities.

      (Except for SPIFFE, but that's a niche thing and used only for Kubernetes bullshit.)

      The whole field of "security" is a farce staffed by clowns.

      • cyberax 48 minutes ago
        AWS had switched from using something like this ("injection tokens") to just regular IAM roles, though managed by the AWS.

        The only special permission that services (actually, the AWS accounts that they use) inside the AWS have is access to "service principals". The service roles inside customer accounts then use them to grant access.

        AWS IAM is painful, but it shows that you can design a secure permission system.

  • malnourish 4 hours ago
    I imagine this paid out quote the bounty; exploited, it's hard to think of a more damning security flaw.
  • Sytten 2 hours ago
    I recently had to deal with Entra ID for the first time to setup Microsoft OAuth for our site and my god why is it so badly designed.

    Just creating a tenant is a PITA and you get a default tenant you can't change without paying for Microsoft 365? Then you have subscriptions, Microsoft partners, Enteprise vs individual accounts, etc. All mixed with legacy AD naming and renaming, documentation with outdated screenshots, Microsoft Partners bullshit.

    • Propelloni 1 hour ago
      There ist a whole industry clustered around this FUBAR that makes its living by helping companies navigate this shit. It has small and big players and they have no incentive to tell you that there is anything else you could use. The monthly Service fee is too tasty.
  • TavsiE9s 3 hours ago
    Microsoft, Azure, why am I not surprised?
  • cr125rider 6 hours ago
    Wow the keys to all the enterprise castles! That’s wild!
  • gfody 3 hours ago
    after 36 years kerberos seems pretty stable, secure, and well supported finally. why do we need Entra?
    • EvanAnderson 2 hours ago
      Kerberos doesn't have a good monthly recurring revenue "story".
    • jiggawatts 2 hours ago
      Kerberos doesn't work well on the web.
  • jwpapi 6 hours ago
    Was there a bounty?
  • rootsudo 5 hours ago
    Oh man, I was close with this a few times as I ran powershell in different ISE windows and sometimes copied/pasted things over for different tenants, darn - it really seemed so obvious of an exploit!