[Mailman-Developers] GSOC Project idea: OpenPGP integration

[Abhilash Raj]

On Thu, Apr 25, 2013 at 7:05 PM, Daniel Kahn Gillmor
<dkg at fifthhorseman.net>wrote:

> On 04/25/2013 04:36 PM, Stefan Schlott wrote:
> > On 25.04.2013 00:14, Abhilash Raj wrote:
> >
> >> 1) When a message is decrypted and then passed on between the queues, it
> >> creates a security threat for the cleartext message is being held in
> >> memory, even for a small time in between the runners.
> >
> > The Mailman server holds the key to decrypt _every_ incoming message. So
> > if the server is compromised, a message temporarily held in memory is
> > the least of your problems :-)
>
> abhilash might have meant that there is a concern that a decrypted
> message could be stored *on disk* in one of the queues, not just in
> memory.  This could be a problem if an adversary gets access to the disk
> and can get access to the backing storage, even after the files have
> been unlinked from the filesystem (since unlinking files doesn't
> guarantee removal of all traces from the backing storage).
>
> Of course, if the secret key for the list is kept without a passphrase
> on the same filesystem or on a separate filesystem on the same backing
> storage, then your risk is elevated to begin with.
>
> Abhilash, i don't see any mention in your proposal of how you plan to
> deal with the secret key material.  will there be a way for mailman to
> use a secret key that is stored in a password-protected form?  If so, how?
>
> Well I am not quite proficient in cryptography but I tried to answer how
could it be done and have updated on the same link[1]. Here is a copy of
only that part:

One of the biggest issues of any cryptographic procedure is to secure and
manage the keys. Firstly for the lists, when the list is created by the
owner the keypair is generated by mailman in some time(because when i was
trying to create one using gnupg, it asked me to wait for sometime and keep
doing some work to get threshold entropy. Although in reality I don't have
much idea about how the keys are created, but I am guessing that it
somewhere uses the random bits from the memory of the host where key is
created and thus required a threshold entropy for the proper randomization
of the key. On virtualised Linux systems, this can often be achieved by
installing the rng-tools package.) and is stored in the database against
the name of the list. It will then be available for download to the
subscribers. [python-gnupg][2] also allows one to encrypt/decrypt using the
keys that are protected by a paraphrase. Such paraphrase though would then
be stored in cleartext format in database. Though this poses a security
thread but even if you encrypt and store the paraphrase, you can only slow
the process of decryption once the server is compromised since the
private-paraphrase-encryption key will also be needed to be stored
somewhere on the local disk.

The pub-keys added by the users will be stored in different table(having
many to one relationship with users) and will be used whenever there is a
need to encrypt or verify_signature.


[1]: https://gist.github.com/maxking/5455462#key-management

>         --dkg
>
>
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-- 
Abhilash Raj