[mosh-devel] Persistent Connections

[Carlos Cabanero]

Thanks a lot Keith! I completely understand the implications of reusing a
sequence, so I will make sure states are not resumable more than once :)

On Wed, Nov 9, 2016 at 8:03 PM, Keith Winstein <keithw at cs.stanford.edu>
wrote:

> Hello Carlos,
>
> Sounds cool! I think you will need to save every state newer than the
> "throwaway number," because the other side is allowed to reference that
> state (or any newer state that you have acked) in building a new diff.
>
> My main fear with these saved states is that a user would somehow be able
> to try "resuming" the same session twice, from the same save file. That
> will result in the same sequence number being reused, which would be
> cryptographically catastrophic. So any implementation that allows
> "resuming" from a saved state must ensure that the saved state is destroyed
> as part of the resumption.
>
> -Keith
>
> On Wed, Nov 9, 2016 at 3:14 PM, Carlos Cabanero <carlosecabanero at gmail.com
> > wrote:
>
>> I have started to work on “Persistent Connections” for Blink with great
>> success! For background, these are the related GH issues (
>> https://github.com/mobile-shell/mosh/issues/394) and (
>> https://github.com/blinksh/blink/issues/59).
>>
>>
>> I hacked together - as in I have hardcoded most of the stuff - a simple
>> version that is able to save a session to disk and reconstruct it given the
>> previous key. Turns out it was all a lot easier than I thought, without
>> requiring hardcore object serialisation. States (timestamp, sequence nonce
>> and content) can be dropped to disk as if they were going to be sent over
>> the network, and reconstructing the states to the initial
>> Terminal::Complete and Network::UserStream objects is straightforward with
>> the diff functions.
>>
>>
>> There is the question of how many states should be saved, from reading
>> the code I guess the answer is all of them, from my test only the latest
>> acked one was enough - but again, crappy test.
>>
>>
>> Another obvious security concern as the states contain information from
>> the terminal in a completely readable format. Could that be encrypted again
>> with the key before saving? In the case of iOS I can save the secure key to
>> the keychain. But I think that on top of that, saving the session with a
>> Passphrase might be a good idea.
>>
>>
>> I understand that this might only be useful in Blink, but any guidance
>> would be appreciated. In the same manner, if you change your opinion, I'm
>> more than happy to walk the extra mile and make it work for everyone.
>>
>>
>> Thanks a lot!!
>>
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>>
>>
>
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