Re: AW: Re: [qubes-users] AW: Idea for (resonable secure) cloud-storage usage with Qubes
Hi again,
On 10/15/2017 08:37 PM, '[799]' via qubes-users wrote:
I think you have some misconceptions here
- the main one being why people tend to use
Qubes OS: Segregation of data to application-
specific domains, i.e. impact of a domain
compromise is limited.
You are right, regarding why people use Qubes.
But depending on specific workflows there is a need to either work with cloud
storage for collaboration or to switch the OS completely for this use case.
Ok, that's something I can understand. So far I was under the impression
that all of your VMs were using that cloud backed storage.
Think about a (cloud based or on premise) storage service which is used by
several people.
My goal is to work 100% in Qubes and I think that splitting access of data and
local storage offers a better security than having the data synced and stored
in one AppVM.
And I tried to build something that makes it easier to access data from various
VMs in an easy way (knowing that it is less secure than using qvm-copy-to-vm).
But using some scripts we can reduce the attack surface on nfs in such a way,
that we only enable NFS/open ports when access is needed.
I can't see how this approach is less secure than using one VM for
syncing/storing/accessing the data?
The point here is that it's not much more secure neither. In fact you
might even introduce unwanted mistakes (mistakenly opening ports to one
of your other VMs e.g.), which ultimately could lead to the compromise
to one of your other VMs.
Attacking a nfs implementation shouldn't be too hard for a dedicated
attacker, i.e. you can bet that a compromise of any of your
nfs-connected VMs would lead to a compromise of _at least_ all of your
nfs connected VMs. Which is equal or worse than what you had without
that idea.
So the standard attack path would be:
other OS --> nfs-client VM --> other nfs VMs
Your idea however makes your Qubes
installation vulnerable to: - Any attacks
originating from that OS ("files should still be
accessible/decryption from other Operating
systems")
True, but wouldn't this mean that the AppVM which is working as NFS Client must
be compromised before NFS is attacked?
Yes, also holds for the standard Qubes OS model though (you running your
nfs client in the same domain where you have your nfs data).
Nfs-based attacks (basically all your AppVMs
using nfs will be vulnerable to all nfs
vulnerabilities
NFS access to the server is allowed on a per VM basis (firewall allow per IP),
shouldn't this be enough to reduce NFS attack surface?
No. Protocol & implementation vulnerabilities exist.
encfs based attacks which people can even
find on wikipedia.
Yes true, it is a shame, that we still don't have a multiplatform open source
encryption standard that could maybe also be adapted by cloud storage providers.
But as mentioned the idea could also be implemented with other encryption
solutions like CryFS, ...
I don't know that one.
Anyway file-based encryption suffers from revealing meta data such as
file access timestamps, number of files, work activity, maybe even
folder structures.
Volume-based encryption doesn't tend to have these issues. The
containers of the truecrypt successor should also be supported by
cryptsetup if I recall correctly.
Assuming the other OS is Qubes OS you could do one encrypted
voloume/container per Qubes domain and do an implementation as follows:
- mount the remote fs in some "distributor" appVM, e.g. using sshfs
- use qvm-block from dom0 to attach the encrypted containers from the
distributor VM to the respective target domains
- decrypt the containers in the respective domains using keys that can
only be found there
That implementation still suffers from parsing attacks on cryptsetup,
but the others should be identical to attacking Qubes OS itself.
It might be possible to mitigate potential cryptsetup issues by writing
an own qrexec service, but that should be left to the pros...
The performance should be roughly as good as reading & writing from a
network backend is in general.
For non-Qubes OS systems I don't see the point of separating domains
though. The other OS doesn't do it neither.
KR
David
--
You received this message because you are subscribed to the Google Groups
"qubes-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to qubes-users+unsubscr...@googlegroups.com.
To post to this group, send email to qubes-users@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/qubes-users/b5758a2c-bcdd-aa2b-ece9-b7031e22d59a%40hackingthe.net.
For more options, visit https://groups.google.com/d/optout.
smime.p7s
Description: S/MIME Cryptographic Signature
AW: Re: [qubes-users] AW: Idea for (resonable secure) cloud-storage usage with Qubes
Hello David,
Thank you for the open feedback.
> I think you have some misconceptions here
> - the main one being why people tend to use
> Qubes OS: Segregation of data to application-
> specific domains, i.e. impact of a domain
> compromise is limited.
You are right, regarding why people use Qubes.
But depending on specific workflows there is a need to either work with cloud
storage for collaboration or to switch the OS completely for this use case.
Think about a (cloud based or on premise) storage service which is used by
several people.
My goal is to work 100% in Qubes and I think that splitting access of data and
local storage offers a better security than having the data synced and stored
in one AppVM.
And I tried to build something that makes it easier to access data from various
VMs in an easy way (knowing that it is less secure than using qvm-copy-to-vm).
But using some scripts we can reduce the attack surface on nfs in such a way,
that we only enable NFS/open ports when access is needed.
I can't see how this approach is less secure than using one VM for
syncing/storing/accessing the data?
> Your idea however makes your Qubes
> installation vulnerable to: - Any attacks
> originating from that OS ("files should still be
> accessible/decryption from other Operating
> systems")
True, but wouldn't this mean that the AppVM which is working as NFS Client must
be compromised before NFS is attacked?
> Nfs-based attacks (basically all your AppVMs
> using nfs will be vulnerable to all nfs
> vulnerabilities
NFS access to the server is allowed on a per VM basis (firewall allow per IP),
shouldn't this be enough to reduce NFS attack surface?
> encfs based attacks which people can even
> find on wikipedia.
Yes true, it is a shame, that we still don't have a multiplatform open source
encryption standard that could maybe also be adapted by cloud storage providers.
But as mentioned the idea could also be implemented with other encryption
solutions like CryFS, ...
> if you don't want to add
> another idea to the security circus
> I'd reconsider either using Qubes OS, your
> other OS or your architecture.
Hmm ..., why should I abandon Qubes and use a much more less secure OS just
because working with cloud/external storage is part of some (!) of my workflows?
Even if all VMs which I use in the described solution are compromised, I can
still have other VMs which are fine.
So basically it's one more reason to use Qubes ;-)
[799]
--
You received this message because you are subscribed to the Google Groups
"qubes-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to qubes-users+unsubscr...@googlegroups.com.
To post to this group, send email to qubes-users@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/qubes-users/oZiNcfSwB33LIJmkEc-H483lwPzzbGTv-Wbwrq9BnvNnuyLKXbc1yshBcPkBf5MeimHjaCULUTr-XgLh70ZV_tMW4IJ68RG220hccF2Pqso%3D%40protonmail.com.
For more options, visit https://groups.google.com/d/optout.
Re: [qubes-users] AW: Idea for (resonable secure) cloud-storage usage with Qubes
Hi,
I think you have some misconceptions here - the main one being why
people tend to use Qubes OS:
Segregation of data to application-specific domains, i.e. impact of a
domain compromise is limited.
Your idea however makes your Qubes installation vulnerable to:
- Any attacks originating from that OS ("files should still be
accessible/decryption from other Operating systems").
- Nfs-based attacks (basically all your AppVMs using nfs will be
vulnerable to all nfs vulnerabilities - and there have been quite a few
in the past).
- encfs based attacks which people can even find on wikipedia.
If you don't want to add another idea to the security circus, I'd
reconsider either using Qubes OS, your other OS or your architecture.
The invisible things blog articles should be a good point to start with.
KR
David
On 10/15/2017 11:01 AM, '[799]' via qubes-users wrote:
Hello,
I'd like to add, that I know that EncFS seems to have some issues, mentioned
here for example:
https://defuse.ca/audits/encfs.htm
While this report is from 2014 and a new version has been issued it seems that
encfs 2.x (which should provide better security) is still on its way - if it
will come at all.
Unfortunately encfs is the only solution which is cross-platform, if someone is
using a Linux only environment, the encryption layer could be replaced with
other solutions:
https://www.cryfs.org/comparison
As such the subject should not be...
"Idea for (resonable secure) cloud-storage usage with Qubes"
... but ...
"Idea for (a slightly more secure) cloud-storage usage with Qubes"
[799]
PS: sorry for Top-Posting ;-)
I have a typo in my initial post, replace my-untrusted with my-work (where I
unmount the encfs uencrypted directory)
Original-Nachricht
An 15. Okt. 2017, 01:54, [799] schrieb:
Hello,
I thought about how to work with cloud storage under Qubes OS and I'd like to
share my idea with you, to provide feedback.
I have already build a prototype that works "reasonable" well, but I am far
away from being a security professional, as such I'd like to hear your opion about it.
Assumptions:
You are using cloud storage like Microsoft OneDrive and you would like to do so
under Qubes in a more secure way.
Goals:
- all files within onedrive should be encrypted
- files should still be accessible/decryption from other Operating systems
- decrypted data storage and cloud storage access should be separated into two
AppVMs
- different AppVMs should have access to data in the cloud storage, but it's
impossible for an AppVM to read the data which should be read by other AppVMs
(meaning you have the option to create individuall encrypted directories)
- solution should be easy to use and relying on scripts to provide good
automation and a good tradeoff between security and user experience.
Idea:
In order to reach the goals, the idea is to work with two AppVMs:
1. "Access+Transfer AppVM" this VM will access the cloud storage provider,
provide synchronisation and will always see encrypted data
2. "Storage-AppVM" this VM will receive the encrypted files from the
Access+Transfer AppVM and store the files. It will also work as a data-hub to provide
access to data to your other AppVMs which you use to manipulate the data within this VM.
As such we have separated:
- Access & Transfer of data from cloud storage provider
- Local data storage
- Data manipulation
Solution Design:
[Access+Transfer AppVM]
Template: fedora-25-minimal
Additional packages:
- OneDrive Freeclient
([https://github.com/skilion/onedrive)](https://github.com/skilion/onedrive)
- sudo dnf -y install nfsutils
Will be configured to mount a NFS-share from the Storage AppVM and to access
OneDrive to synchronize the files
Data will be downloaded and storad in the mounted NFS-Share of the Storage AppVM
[Storage App-VM]
Template: fedora-25-minimal
Additional packages:
- sudo dnf -y nfs-utils encfs
This machine has been setup as a NFS Server.
The /etc/exports file and also the iptables Firewall of this AppVM has been
setup, so that the [Access+Transfer AppVM] kann access a certain location.
Within this location all files ENCFS-encrypted.
As such the Access+Transfer AppVM but also the Cloud Storage provider will only
see encrypted files.
Additional AppVMs can also mount the main NFS Share/directory.
Those AppVMs can access certain subfolders and mount them via ENCFS to get the
unecrypted data.
So the ENCFS decryption are done in those AppVMs.
You could setup various subfolders within your Onedrive directory and each
folder could be encrypted within the different AppVMs.
Example:
onedrive\photos --> NFS Share to --> my-photo-appvm
onedrive\work --> NFS Share to --> my-work-appvm
onedrive\media --> NFS Share to --> my multimedia-appvm
Let's look at one AppVM (example my-work-appvm = 10.137.2.25 // storage-appvm =
10.137.2.20)
On sys-firewall there is a rule, so that the work-appvm can access the
storage-appvm:
[user@sys-firewall ~]$ sudo
[qubes-users] AW: Idea for (resonable secure) cloud-storage usage with Qubes
Hello, I'd like to add, that I know that EncFS seems to have some issues, mentioned here for example: https://defuse.ca/audits/encfs.htm While this report is from 2014 and a new version has been issued it seems that encfs 2.x (which should provide better security) is still on its way - if it will come at all. Unfortunately encfs is the only solution which is cross-platform, if someone is using a Linux only environment, the encryption layer could be replaced with other solutions: https://www.cryfs.org/comparison As such the subject should not be... "Idea for (resonable secure) cloud-storage usage with Qubes" ... but ... "Idea for (a slightly more secure) cloud-storage usage with Qubes" [799] PS: sorry for Top-Posting ;-) I have a typo in my initial post, replace my-untrusted with my-work (where I unmount the encfs uencrypted directory) Original-Nachricht An 15. Okt. 2017, 01:54, [799] schrieb: > Hello, > I thought about how to work with cloud storage under Qubes OS and I'd like to > share my idea with you, to provide feedback. > I have already build a prototype that works "reasonable" well, but I am far > away from being a security professional, as such I'd like to hear your opion > about it. > Assumptions: > You are using cloud storage like Microsoft OneDrive and you would like to do > so under Qubes in a more secure way. > Goals: > - all files within onedrive should be encrypted > - files should still be accessible/decryption from other Operating systems > - decrypted data storage and cloud storage access should be separated into > two AppVMs > - different AppVMs should have access to data in the cloud storage, but it's > impossible for an AppVM to read the data which should be read by other AppVMs > (meaning you have the option to create individuall encrypted directories) > - solution should be easy to use and relying on scripts to provide good > automation and a good tradeoff between security and user experience. > > Idea: > In order to reach the goals, the idea is to work with two AppVMs: > 1. "Access+Transfer AppVM" this VM will access the cloud storage provider, > provide synchronisation and will always see encrypted data > 2. "Storage-AppVM" this VM will receive the encrypted files from the > Access+Transfer AppVM and store the files. It will also work as a data-hub to > provide access to data to your other AppVMs which you use to manipulate the > data within this VM. > > As such we have separated: > - Access & Transfer of data from cloud storage provider > - Local data storage > - Data manipulation > > Solution Design: > [Access+Transfer AppVM] > Template: fedora-25-minimal > Additional packages: > - OneDrive Freeclient > ([https://github.com/skilion/onedrive)](https://github.com/skilion/onedrive) > - sudo dnf -y install nfsutils > Will be configured to mount a NFS-share from the Storage AppVM and to access > OneDrive to synchronize the files > Data will be downloaded and storad in the mounted NFS-Share of the Storage > AppVM > > [Storage App-VM] > Template: fedora-25-minimal > Additional packages: > - sudo dnf -y nfs-utils encfs > This machine has been setup as a NFS Server. > The /etc/exports file and also the iptables Firewall of this AppVM has been > setup, so that the [Access+Transfer AppVM] kann access a certain location. > Within this location all files ENCFS-encrypted. > As such the Access+Transfer AppVM but also the Cloud Storage provider will > only see encrypted files. > Additional AppVMs can also mount the main NFS Share/directory. > Those AppVMs can access certain subfolders and mount them via ENCFS to get > the unecrypted data. > So the ENCFS decryption are done in those AppVMs. > You could setup various subfolders within your Onedrive directory and each > folder could be encrypted within the different AppVMs. > Example: > onedrive\photos --> NFS Share to --> my-photo-appvm > onedrive\work --> NFS Share to --> my-work-appvm > onedrive\media --> NFS Share to --> my multimedia-appvm > > Let's look at one AppVM (example my-work-appvm = 10.137.2.25 // storage-appvm > = 10.137.2.20) > On sys-firewall there is a rule, so that the work-appvm can access the > storage-appvm: > [user@sys-firewall ~]$ sudo iptables -I FORWARD 2 -s 10.137.2.25 -d > 10.137.2.20 -j ACCEPT > > On the storage appvm: > [user@my-storage ~]$ sudo iptables -I INPUT 5 -i eth0 -s 10.137.2.25 -d > 10.137.2.20 -j ACCEPT > The NFS Exports file: > [...] > # 10.137.2.15 = Access+Transfer AppVM > /var/nfs 10.137.2.15(rw,sync,no_subtree_check) > # 10.137.2.25 = Work AppVM > /var/nfs/work 10.137.2.25(rw,sync,no_subtree_check) > [...] > > In the Work AppVM you are mounting the NFS Share from the Storage AppVM: > sudo mount 10.137.2.20:/var/nfs/work /mnt/onedrive-work.encfs > > In Order to access the files, the NFS share is encfs-mounted: > encfs /mnt/onedrive-work.encfs ~/work > > the unencrypted files can be accessed in ~/work. > If saved they will be encfs-encrypted and
