[OpenAFS-devel] [GSoC 2010] Encrypted storage

[omalleys@msu.edu]

Just some thoughts, and as always I may be 100% offbase. Feel free to  
send flames my way...

--
If you encrypt the cachemanager, what happens to the cache when you  
use multiple local accounts and a single afs account, or single afs  
account and multiple afs accounts? or mults of each in combinations?  
(I do this a lot..) Do i end up having to recache everything for each  
local and afs account? If so, doesn't this defeat part of the purpose  
of the cachemgr?

---
Tertiary to the thread, but with all the interest in encryption with  
our GSoC...

If I understand this correctly,
I have a single master key, that encrypts all the volumes..
If I want to change this key, I have to unencrypt the volumes with the  
old key and re-encrypt them with the new key. If this is correct, what  
happens when my key gets compromised, or if I just want to change the  
key as part of a standard security measure eg a stronger key? I have  
say a million volumes, and it is an essential part to my  
infrastructure so scheduling downtime is extremely hard.

If my understanding is correct, and we have a ton of interest in  
encryption.. can we make it so we can use multiple master keys? So i  
can migrate from master key A to master key B more transparently? Then  
use some mechanism, like a pthreaded bu to dump the volume with the  
old key and re-encrypt and restore the volume with the new key? It  
does take the individual volumes offline but not the whole cell. (you  
also need something in the vldb that lets you figure out what volume  
is using what key too.)

If so what happens to the data that is already cached out in userland  
with the old key?

---

With all the encryption going on, I worry about filesystem performance  
and the cpu overhead. I like abstraction layers and I agree with Mr.  
Altman's development plan especially about the abstraction. Because  
even if you get it to work, in 3 months, it is probably going to take  
some time to really get it tweaked, and then by the time you do that,  
someone will have broken the encryption algorithm...

Hcrypt may have the algorithm already, but there was one algorithm,  
and it was written for cell phones, and I forgot the name of it, (new  
in the last 7 years..) but it was designed to be less processor  
intensive. It was based on ellipses. (i think it ended up tot be 1  
quadrant of the ellipse or an arc)/ I don't think it has been broken  
yet. Which the concept actually fits especially the client side of  
AFS, where you might be running an older computer or porting to say  
something on the Android platform.

--
Oh, just one more thing...
If you are going to be using the exact same way to encrypt the cache  
as you do your volumes on the fileserver, wouldn't this make it easier  
for an attacker to decrypt your master key? IE I make a change in my  
local cache, and then I can see what changes were made to the cache,  
then I probe for the differences and I can get the master key? (or  
does way refer to the algorithm and not the key?)

I would think you would need to issue a key from the afs cell to each  
individual cachemgr. Or the more I think about it this is what is done..



Quoting Jeffrey Altman <jaltman@secure-endpoints.com>:

> On 3/31/2010 3:56 AM, Sanket Agarwal wrote:
>>
>>
>> On Wed, Mar 31, 2010 at 12:21 PM, Sanket Agarwal
>> <sanket@sanketagarwal.com <mailto:sanket@sanketagarwal.com>> wrote:
>>
>>     Simon would be a better person to what should and what should not be
>>     a part of the GSoC proposal. But, as of now I think it should be
>>     deferred.
>
> If the result of this project is meant to be an architectural change
> to the OpenAFS cache manager then by all means the full membership
> of this list has the right to propose suggestions and discuss their
> concerns.  However, it must be kept in mind that this project proposal
> is for a GSoC project and as such the scope must be reasonable.
>
> Simon, as the person that proposed the project, should be the one
> to explain what his intentions were with regards to the GSoC goals.
>
>>     The first thing for the project would be to integrate HCrypto into
>>     OpenAFS and provide an API for future use at a Kernel Level. As
>>     Simon envisions, it is necessary to put the Crypto API into at the
>>     Kernel level rather than using rich User Mode libraries like OpenSSL
>>     etc, which can be used at the Client[ Cache Manager ] side.
>
> I suspect that this work has already been done by Simon as part of the
> rxgk work.  I do not think this should be in scope for a GSoC project.
>
>>     The second task would be to get the Encryption Layer working.
>>     File encryption would be targeted as of now. In order to encrypt the
>>     Directory Structure, server's support shall be necessary. As I have
>>     to technically complete the stated project within 3 months( I will
>>     obviously continue to contribute :) ), I cannot form astronomical
>>     proposals!
>
> Spenser Olsen replied in another response to this thread that he
> believes that EncFS would provide equivalent functionality to this
> proposed project when overlaid on top of /afs.  In a sense, EncFS is an
> excellent comparison to this project proposal.  The functionality is
> essentially the same.  The difference is that EncFS, being a FUSE file
> system, is only available on a subset of the platforms that OpenAFS
> supports.  One of the strengths of OpenAFS is that once data is stored
> on Linux it can also be accessed or modified on Solaris, Windows, MacOS,
> and many other file systems.  One way of describing this project would
> be to implement EncFS as part of the OpenAFS cache manager.
>
> If the goal of this project was to eventually produce a broader
> cross-platform multi-user key management system, then I think that
> architecture work would have to be developed and agreed to by the
> community before a portion of its implementation can be submitted as a
> GSoC project.  That is of course assuming that the goal of the project
> is code that will be integrated into a future stable OpenAFS release
> within a year.  If the goal is to produce a working prototype so that
> the community can gain some experience developing such a solution, then
> I believe going ahead with this project in GSoC is not a problem.
>
> As with all GSoC projects, we hope the end results of the project will
> be usable code that can be integrated.  My biggest concern is ensuring
> that whatever is implemented as part of the OpenAFS Unix cache manager
> can eventually be implemented on Windows or other platforms that do not
> make the same internal assumptions.  I would also like to ensure that
> the encryption functionality would be optional.  Perhaps loaded at
> run-time.  As a result, I would like to see the design be two components:
>
>  * First, develop an abstraction layer that sits within the Unix
>    cache manager but logically above the cache manager.
>
>  * Second, an implementation of an encryption layer module that
>    plugs into that interface.
>
> There are several benefits to this approach.  First, separating the
> encryption layer from the cache manager layer allows the encryption
> layer's assumptions about block size to be independent from the cache
> manager's assumptions about chunk size.  Second, the abstraction layer
> is something that in theory can be shipped as part of a future OpenAFS
> much sooner than a full encryption layer.  Third, such a layer permits
> different encryption layers to be experimented with without further
> modifications to the cache manager implementation.  Finally, if
> implemented correctly, the encryption layer should be highly portable
> permitting it to be reused in other cache manager implementations.
>
> A beneficial side effect of such a design is that the contents of the
> cache will be encrypted in exactly the same way as on the file server.
> An attacker will not be able to read unencrypted data out of the cache
> files.
>
> Jeffrey Altman
>
>
> Jeffrey Altman
>
>
>