Re: [gentoo-ppc-user] CryptoAPI enabled PPC kernel available

[José Andrés Arias Velichko]

Thanks, it sounds great!!!

I will try it asap.


Regards,
	Andres


Hola Olivier, el 04 de feb de 2003, a las 12:36 +0100, Olivier Reisch decías:
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> Hello,
>
> For those interested in advanced security, I put together a CryptoAPI enabled
> PPC kernel for Gentoo. CryptoAPI allows you to attach a crypted partition or
> virtual volume to a loopback device and then mount it as normal volume into
> your file system. This for instance allows you to have your /home directory
> fully encrypted, so if someone gets access to your box, he won't be able to
> mount or read any data without authenticating first (even using a Boot CD),
> as all the data is stored in encrypted form on your disk as soon as the
> partition or virtual volume gets unmounted. Encryption used is pretty strong,
> ciphers included are AES (aka Rijndael), MARS, RC6, Serpent, Twofish, 3DES,
> Blowfish, CAST5 cipher, GOST, IDEA and some more. Most of them support the
> use of 256 bit keys.
>
> For more information about the benefits of CryptoAPI, you can take a look at
> their site at http://www.kerneli.org
>
> The current kernel in Portage is as follows:
>
> *  sys-kernel/ppc-sources-crypto [ Masked ]
>       Latest version available: 2.4.20
>       Latest version installed: 2.4.20
>       Size of downloaded files: 26,980 kB
>       Homepage:    http://www.kernel.org/ http://www.kerneli.org/
> http://www.gentoo.org/
>       Description: Full cryptoapi enabled sources for the Gentoo Linux PPC
> kernel
>
> It is currently ~ppc masked for further testing. It's basically a 2.4.20-ben5
> kernel with CryptoAPI 0.1.0, cryptoloop 0.0.1-pre1 and the loop-jari patch
> for 2.4.20.
>
> To try it, you can do the following:
>
> emerge rsync
> env ACCEPT_KEYWORDS="~ppc" emerge ppc-sources-crypto
> USE="crypt" emerge linux-utils
>
> The sources for the kernel are still being mirrored to the Gentoo mirrors at
> the moment. In the meantime the ebuild will automatically fetch them from my
> local mirror, which may be a bit slower.
> We have to remerge linux-utils to have mount and losetup patched for CryptoAPI
> support.
>
> Next step is to go compile our new kernel:
>
> cd /usr/src/linux-ppc-crypto-2.4.20
> make oldconfig
> #This will generate a default config which should work fine on most machines,
> #it also already has all the ciphers enabled as modules, so you can load
> #those you'll need into the kernel.
> make menuconfig
> #Only do this if you want to modify any kernel options; for the CryptoAPI
> #settings, i suggest going with the default ones.
> make dep clean vmlinux modules
> make modules_install
> cp vmlinux /boot/vmlinux-2.4.20-ppc-crypto
> cp System.map /boot/System.map-2.4.20-ppc-crypto
>
> Add entry to /etc/yaboot.conf and run "ybin".
>
> Finally, we need to update /etc/modules.conf
> To do so, add a file cryptoapi to /etc/modules.d with the following content:
>
> keep
> path[cciphers]=/lib/modules/`uname -r`/kernel/crypto/ciphers
> keep
> path[cdigests]=/lib/modules/`uname -r`/kernel/crypto/digests
> keep
> path[cdrivers]=/lib/modules/`uname -r`/kernel/crypto/drivers
>
> Run modules-update
>
> Reboot.
>
> Once you are booted into the CryptoAPI kernel, we can start experimenting. As
> an example, we will create a 50MB virtual volume which we will crypt with the
> serpent cipher and mount to /mnt/secret.
>
> 1) Create the virtual volume (replace /home/doctomoe by your homedir of
> course)
>
> cd /home/doctomoe
> dd if=/dev/urandom of=/home/doctomoe/secretvolume bs=1M count=50
>
> This may take a while. We use urandom to better hide the crypted data within
> the volume. If we zeroed it, it would be easy to detect where the encrypted
> data is on the volume.
>
> 2) Mount the volume to a loop device
>
> Make sure everything we need is loaded. If you have used the default kernel
> config, all you need to do is to modprobe the cipher you want to use.
>
> modprobe cipher-serpent
>
> If you compiled cryptoloop as a module (not default), make sure to load it
> too:
>
> modprobe cryptoloop
>
> Ok, now to the serious stuff :)
>
> #Attach volume to a loop device
> losetup -e serpent -k 256 /dev/loop0 /home/doctomoe/secretvolume
>
> You will be asked a password. Type it carefully, as you won't be asked twice
> and the password is not stored within the volume, so if you want to mount it
> again later, you have to carefully type it again to avoid screwing the volume
> up. The argument after -e is the cipher algorithm used and the -k argument is
> the keysize generated for the encryption. It has nothing to do with the size
> of your password.
>
> Now we create a filesystem on it.
>
> mkfs -t ext3 /dev/loop0
>
> Finally, we can mount it.
>
> mount -t ext3 /dev/loop0 /mnt/secret
>
> Voila, you can now access /mnt/secret like any other volume/directory on your
> system. Once you have stored your sensitive data and want to unmount the
> volume again, do as follows:
>
> umount /mnt/secret
> losetup -d /dev/loop0
>
> Do remount again, you do exactly like above, but you don't format the volume
> again of course. If you typed in the wrong password, mount will give you a
> bad filesystem error. Just detach (losetup -d) the loop device and try again.
>
>
> Tips and tricks:
>
> You can add a line to /etc/fstab which will allow you to mount the volume with
> a single command and also as normal user (no need to be root then):
>
> The line should look like:
>
> /home/doctomoe/secretvolume     /mnt/secret  ext3
> user,defaults,noauto,loop,encryption=serpent,keybits=256   0 0
>
> All on one single line of course.
>
> Once you added the line, you can attach and mount the drive by simply doing:
>
> mount /mnt/secret
> #enter password
>
> and unmount and detach it with:
>
> umount /mnt/secret
>
> Finally, you can also write a script that will ask you twice for the password
> and then mount the volume. That way, you will be less prone to enter a wrong
> password. Example:
>
> #!/bin/bash
>
> echo "Mounting crypted volume to /mnt/secret..."
>
> if cat /etc/mtab | grep "/mnt/secret" >/dev/null
> 	then
> 		echo "Volume already mounted..."
> 		exit
> 	else
> 	until [ "$PASS1" = "$PASS2" -a -n "$PASS1" ]; do
>         	# the bash read buitlin has to support the -s option.
>         	# Don't use read without -s!!
>         	read -s -p "Enter Passphrase: " PASS1; echo
>         	read -s -p "Re-enter Passphrase: " PASS2; echo
> done
>
> echo "$PASS1" | mount -p 0 "/mnt/secret"
>
> cd /mnt/secret
>
> fi
>
>
> That's it for now folks. I hope I didn't forget anything. If you want to
> report about your success or failure or have any questions about using the
> kernel, feel free to mail me (see email addy below)
>
> Greetings,
> Olivier Reisch aka DocTomoe
>
> - --
> ________________________________________________
> Olivier Reisch                                 doctomoe@g.o
> Gentoo PPC Developer
> http://www.gentoo.org
>
> For safe mail, get my PGP Key:
> http://perso.wanadoo.fr/olivier.reisch/oreisch_public_key.gpg
> ________________________________________________
>
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José Andrés Arias Velichko      Grupo de Usuarios de Linux
    locke@××××××××.es        Universidad Carlos III de Madrid
 http://gul.uc3m.es/~locke          http://gul.uc3m.es

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