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The content of the cookie isn't compromised, but you can trivially sidejack a cookie on an unencrypted connection and access the information through the website

The content of the cookie isn't compromised, but you can trivially sidejack a cookie on an unencrypted connection and access the information through the website itself, in essence stripping any security. Arguably encrypting the cookie is a waste of processor time, but more importantly I think you may be giving people a false sense of security. The proper way to do secure interactions is via SSL, and I'm not sure encrypted cookies vs simply HMACed cookies gives you any true security advantage (as session storage or anything else).

gregwebs 15y ago
SSL is (important as you say but) orthogonal to this issue. If you steal a non-encrypted cookie and take over a user's session the result is the same.
- shadowfiend 15y ago
  Yes, that's precisely what I'm saying. So, let me put it differently: what security advantage does an encrypted session cookie confer? I see two possibilities: - Someone who hijacks a request with the cookie in it cannot see the data in the cookie. But they can access the site as the user, so there is no real world benefit to this fact. - Someone on the same computer cannot see the data in the cookie. But again, they have the cookie value, so they can access the site as the user, so there is again no real world benefit to the fact that they can't see the data in the cookie itself, because they can interact with the site and see the data there. I guess I'm just looking for an example scenario where the cookie being encrypted offers a concrete benefit from a security standpoint.
  - cies 15y ago
    i can think of only one case: that in which the site owners dont want the user (or sidejacker in case of a non-SSL connection) to see some data they wish to put in the cookie. i'd cannot think of a web app i worked on where this was needed. (the hashing is cool though -- tinker prevention is common to be a-good-thing)
    - shadowfiend 15y ago
      Notably, this would only happen if you have data in the user's session that the user themselves cannot get to by using the site. I confess I can't think of any such session data, but I suppose it could exist. And yes, some sort of HMAC is pretty much mandatory if you're going to do client-side session storage securely, no question.
  - santadays 15y ago
    I might be wrong here but I think it prevents against a user tampering their own cookie. Say I store User_Id:5 in a cookie and pass it over an ssl connection. The user can still change from User_Id:5 to User_Id:6 and get user 6's account info. Typically you would have to store a non guessable token instead to avoid this. I think by encrypting the cookie you provide the non-guessable part of the equation without having to think about it. This isn't really a benefit from a security standpoint (as in it doesn't provide more security), but it is convenient. Could be wrong here, I'm not very familiar with Yesod.
    - cies 15y ago
      the hashing prevents tinkering/tampering the encryption prevents reading (and thereby also -- to some extend -- but not specifically tinkering/tampering)
  - gregwebs 15y ago
    As has been said already there is no benefit. It is just a convenient default session storage.
    - shadowfiend 15y ago
      Got it! That makes sense, thanks for following my argument through :)

gregwebs 15y ago

SSL is (important as you say but) orthogonal to this issue. If you steal a non-encrypted cookie and take over a user's session the result is the same.

shadowfiend 15y ago
Yes, that's precisely what I'm saying. So, let me put it differently: what security advantage does an encrypted session cookie confer? I see two possibilities: - Someone who hijacks a request with the cookie in it cannot see the data in the cookie. But they can access the site as the user, so there is no real world benefit to this fact. - Someone on the same computer cannot see the data in the cookie. But again, they have the cookie value, so they can access the site as the user, so there is again no real world benefit to the fact that they can't see the data in the cookie itself, because they can interact with the site and see the data there. I guess I'm just looking for an example scenario where the cookie being encrypted offers a concrete benefit from a security standpoint.
- cies 15y ago
  i can think of only one case: that in which the site owners dont want the user (or sidejacker in case of a non-SSL connection) to see some data they wish to put in the cookie. i'd cannot think of a web app i worked on where this was needed. (the hashing is cool though -- tinker prevention is common to be a-good-thing)
  - shadowfiend 15y ago
    Notably, this would only happen if you have data in the user's session that the user themselves cannot get to by using the site. I confess I can't think of any such session data, but I suppose it could exist. And yes, some sort of HMAC is pretty much mandatory if you're going to do client-side session storage securely, no question.
- santadays 15y ago
  I might be wrong here but I think it prevents against a user tampering their own cookie. Say I store User_Id:5 in a cookie and pass it over an ssl connection. The user can still change from User_Id:5 to User_Id:6 and get user 6's account info. Typically you would have to store a non guessable token instead to avoid this. I think by encrypting the cookie you provide the non-guessable part of the equation without having to think about it. This isn't really a benefit from a security standpoint (as in it doesn't provide more security), but it is convenient. Could be wrong here, I'm not very familiar with Yesod.
  - cies 15y ago
    the hashing prevents tinkering/tampering the encryption prevents reading (and thereby also -- to some extend -- but not specifically tinkering/tampering)
- gregwebs 15y ago
  As has been said already there is no benefit. It is just a convenient default session storage.
  - shadowfiend 15y ago
    Got it! That makes sense, thanks for following my argument through :)