ecryptfs with an epehemeral key

[Eric Tschetter]

Hello all,

I apologize if this is an easy question, but I've been Googling around
for an answer with no luck and the man pages aren't helping, so I'm
asking here. If this is documented somewhere, feel free to just point
me there.

For context, I want to setup an ecryptfs volume with an ephemeral key.
I do *not* want the key stored anywhere. I want to never, ever be
able to access the data again upon restart. I actually want to be
forced to start over from nothing upon restart.

From looking at the options for starting up ecryptfs, it looks like

they all either require the key to be in a file or available in the
history/ps/etc.:

passphrase_passwd=(passphrase)
passphrase_passwd_file=(filename)
passphrase_passwd_fd=(file descriptor)
passphrase_salt=(hex value)
openssl_keyfile=(filename)
openssl_passwd_file=(filename)
openssl_passwd_fd=(file descriptor)
openssl_passwd=(password)

I'd rather not even store the key in a file and then remove the file,
because technically that file might get persisted to disk and remain
there after the delete. The only thing I can think of is that maybe
there is something magical you can do with file descriptors to get it
to store the key in memory, have a file descriptor point to that
memory location and then destroy the fd and memory.

I'm unfortunately not that well-versed in how this would work though,
so before diving down that potential rabbit hole was hoping to get
some guidance from people on this list.

All help is appreciated.

--Eric

[Michael Chang]

What if you create the key in a file stored on tmpfs? Then it
shouldn't leave RAM, right?

Post by Eric Tschetter
Hello all,
I apologize if this is an easy question, but I've been Googling around
for an answer with no luck and the man pages aren't helping, so I'm
asking here. If this is documented somewhere, feel free to just point
me there.
For context, I want to setup an ecryptfs volume with an ephemeral key.
I do *not* want the key stored anywhere. I want to never, ever be
able to access the data again upon restart. I actually want to be
forced to start over from nothing upon restart.
From looking at the options for starting up ecryptfs, it looks like
they all either require the key to be in a file or available in the
passphrase_passwd=(passphrase)
passphrase_passwd_file=(filename)
passphrase_passwd_fd=(file descriptor)
passphrase_salt=(hex value)
openssl_keyfile=(filename)
openssl_passwd_file=(filename)
openssl_passwd_fd=(file descriptor)
openssl_passwd=(password)
I'd rather not even store the key in a file and then remove the file,
because technically that file might get persisted to disk and remain
there after the delete. The only thing I can think of is that maybe
there is something magical you can do with file descriptors to get it
to store the key in memory, have a file descriptor point to that
memory location and then destroy the fd and memory.
I'm unfortunately not that well-versed in how this would work though,
so before diving down that potential rabbit hole was hoping to get
some guidance from people on this list.
All help is appreciated.
--Eric
--
To unsubscribe from this list: send the line "unsubscribe ecryptfs" in
More majordomo info at http://vger.kernel.org/majordomo-info.html

[Eric Tschetter]

Just to close the loop with the list. I thought the tempfs idea was
good and that took me down learning about that. Which ended up with
me actually running into some docs on using luks and dm-crypt to do an
encrypted volume via /etc/fstab and /etc/crypttab, which seemed like a
plenty good enough solution for what I wanted, so that's what I'm
currently pursuing.

In all the documentation for the cryptsetup stuff, they use
'/dev/urandom' as the "key file" for things like temporary partitions
and swap encryption. I'm not sure if that would work with ecryptfs as
well, but just thought I'd throw it out there.

--Eric

Post by Michael Chang
What if you create the key in a file stored on tmpfs? Then it
shouldn't leave RAM, right?

Post by Eric Tschetter
Hello all,
I apologize if this is an easy question, but I've been Googling around
for an answer with no luck and the man pages aren't helping, so I'm
asking here. If this is documented somewhere, feel free to just point
me there.
For context, I want to setup an ecryptfs volume with an ephemeral key.
I do *not* want the key stored anywhere. I want to never, ever be
able to access the data again upon restart. I actually want to be
forced to start over from nothing upon restart.
From looking at the options for starting up ecryptfs, it looks like
they all either require the key to be in a file or available in the
passphrase_passwd=(passphrase)
passphrase_passwd_file=(filename)
passphrase_passwd_fd=(file descriptor)
passphrase_salt=(hex value)
openssl_keyfile=(filename)
openssl_passwd_file=(filename)
openssl_passwd_fd=(file descriptor)
openssl_passwd=(password)
I'd rather not even store the key in a file and then remove the file,
because technically that file might get persisted to disk and remain
there after the delete. The only thing I can think of is that maybe
there is something magical you can do with file descriptors to get it
to store the key in memory, have a file descriptor point to that
memory location and then destroy the fd and memory.
I'm unfortunately not that well-versed in how this would work though,
so before diving down that potential rabbit hole was hoping to get
some guidance from people on this list.
All help is appreciated.
--Eric
--
To unsubscribe from this list: send the line "unsubscribe ecryptfs" in
More majordomo info at http://vger.kernel.org/majordomo-info.html

--
Thanks,
Michael Chang
4B Software Engineering (Class of 2014)
University of Waterloo