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exclusive flag trouble

dm-crypt Javier Juan Martínez Cabezón 2 participants 2 messages Mar 11, 2012 – Mar 12, 2012

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Hi until now I used a tool to make hidden partitions called scubed (is something like a partition tool that used cryptsetup to create the needed volumes (really old but worked fine)

http://cube.dyndns.org/cgi-bin/viewvc.cgi/trunk/scubed.c?diff_format=l&sortdir=down&logsort=rev&sortby=log&view=markup&root=scubed

- I get realized from this:

http://code.google.com/p/cryptsetup/issues/detail?id=105

With scubed you create five cryptsetup levels in the same device and with all unlocked you assign needed blocks to each of them with scubed)

I haven't get troubles with this is able for example to create read only media (dvd+-r) with multiple ciphered layers.

Here is the readme (with a mini tutorial):
http://cube.dyndns.org/svn/scubed/trunk/README

I think this will not be compatible with --shared flag. If this is correct is there any possibility to make non-exclusive flag available if cryptsetup will not control resizing partitions if not an underlaying tool? (as
this one does that use dm-linear I think?)

If not at least can be enabled the non-exclusive flags to read only media?

Thanks for your time.

#1 lore raw
Quoted 12 lines · Javier Juan Martínez Cabezón

Hi until now I used a tool to make hidden partitions called scubed (is something like a partition tool that used cryptsetup to create the needed volumes (really old but worked fine)

http://cube.dyndns.org/cgi-bin/viewvc.cgi/trunk/scubed.c?diff_format=l&sortdir=down&logsort=rev&sortby=log&view=markup&root=scubed

- I get realized from this:

http://code.google.com/p/cryptsetup/issues/detail?id=105

Quoted 8 lines

With scubed you create five cryptsetup levels in the same device and with all unlocked you assign needed blocks to each of them with scubed)

I haven't get troubles with this is able for example to create read only media (dvd+-r) with multiple ciphered layers.

Here is the readme (with a mini tutorial):
http://cube.dyndns.org/svn/scubed/trunk/README

hm.

# cryptsetup create scubed1 /dev/loop0
Enter passphrase:
# cryptsetup create scubed2 /dev/loop0
Enter passphrase:

This is exactly why exclusive checking is there - it is recipe for data corruption if plaintext devices are wrongly accessed (you write to one device but you will get data from cache for other).

Please can you add a new issue on cryptsetup project page to track that? (I have currently no time to check it now but save it for later.)

I do not think I will reintroduce non-exclusive mode but I would like to check how scubed works and possibly provide some workaround. (IMHO if scubed creates private devices, it is fine, so maybe some patch is the way to go.)

Thanks,
Milan