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Re: review/comments of/on draft-ietf-netconf-tls-00.txt

Dear Bert,
The TLS documents don't discuss the storage of the credentials (certificates, PSK, etc.). However, they recommend some documents to particularly generate the PSK as described in section 7.2 of RFC4279.
I can insert a sub-section on that but I think it will create some interoperability issues if we replace the hashed value of the password with the hashed value of the concatenation of the password and the agent identifier.
Personally, I prefer to recommend the use of a different password on each agent. The issues related to the password storage are not related to the TLS itself, and then better to don't discuss them in the document. But adding some hints in the security considerations section may be useful. 

Best regards,
Badra


Bert Wijnen a écrit :

OK, so that explanation/detail/advice that you give below may
be something worthwhile to add to the text, or maybe state such
a thing in security considerations section?

Or is that already covered in the standard TLS documents?

Bert Wijnen


-----Oorspronkelijk bericht-----
Van: Mohamad Badra [mailto:badra@isima.fr]
Verzonden: maandag 28 januari 2008 16:08
Aan: Bert Wijnen
CC: Netconf
Onderwerp: Re: review/comments of/on draft-ietf-netconf-tls-00.txt


Dear Bert,

Thank you for your comments, I will integrate all of them in the future
version.


- In section 3.2 I read:

    The psk_identity_hint is initially defined in section 5.1 of RFC4279
    The psk_identity_hint can do double duty and also provide a form of
    server authentication in the case where the user has the same
    password on a number of NETCONF agents.

  and wonder: would that not be risky in that if an intruder discovers
              the password of one agent, that he then has access to
              all/several other agents as well?


Of course it is risky in having the same password shared with several
agents, not only from intruder (external entity) point of view but also
from any legitimate agent (internal entity) that has the password.

The easier way to minimize this risk is by recommending the use of a
different password for each agent.

However, it is possible to minimize the risk of discovering the password
of one user as follows: 1) the user has to store its password in a
secure way (e.g. on a temper-resistant), and 2) on each agent, the user
stores the hashed value of the concatenation of the password and the
agent_id (the agent_id is the agent identifier, e.g. IP address). The
user computes the hash version of the concatenation of the password and
the agent_id before connecting to the agent. In this way, the intruder
that discovers the password of one agent will not be able to have access
to all other agents, unless he is able to perform a brute-force or
dictionary attack to recover the password in clear text.

Best regards,
Badra






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