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| -rw-r--r-- | debian/README.opensc | 124 |
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diff --git a/debian/README.opensc b/debian/README.opensc new file mode 100644 index 0000000..b8212b4 --- /dev/null +++ b/debian/README.opensc @@ -0,0 +1,124 @@ +opensc/pcscd with cryptsetup and LUKS on Debian +=============================================== + +This is an overview on how you can make use of cryptsetup with your +smartcard device supported by opensc/pcscd. + +I assume that you already have an initialized smartcard with a RSA key +that has the proper X509 properties for encryption set. To generate such +a key in hardware on the smartcard you should execute the following +command: + + pkcs15-init -G rsa/2048 -a [PIN id] -u sign,decrypt + +If your smart card doesn't support 2048 bit RSA just change the argument +to the largest size possible. + +The decrypt_opensc keyscript decrypts an encrypted key in your boot +partition with the private key on your smartcard. Therefore you have to +create a key for the partition that is to be decrypted using the +smartcard. As pkcs15-crypt does not seem to support PKCS1 padding, the +key is required to have the same size as your RSA key. For a 2048 bit +key use the following (the byte count is 256 as 2048/8 is 256): + + dd if=/dev/random of=/boot/keys/key bs=1 count=256 + +Now the key is added to the LUKS partition: + + cryptsetup luksAddKey /dev/sdXn /boot/keys/key + +Enter an already existing pass phrase and watch cryptsetup doing its +job. As we don't want the key in clear on the hard drive, we are going +to encrypt it with the public key to the key on the smartcard. +Read the public key first: + + pkcs15-tool --read-public-key [key id] -o pubkey + +Then encrypt the random data with the extracted key, destroy the +plain text one and remove your public key from the hard drive (it isn't +necessary to shred it as a potential attacker can't use your public key +for anything). + + openssl rsautl -in /boot/keys/key -inkey pubkey -pubin -raw \ + -encrypt -out /boot/keys/root + shred -u /boot/keys/key + rm -rf pubkey + +Now you'll have to edit `/etc/crypttab`. The format should be familiar but +I'll state it here again: + + name device /boot/keys/root luks,discard,keyscript=decrypt_opensc + +The modules needed by the reader should now be added to +`/etc/initramfs-tools/modules`, so they are loaded on boot time. For +example yenta_socket, pcmcia, pcmcia_core, serial_cs, rsrc_nonstatic for +PCMCIA card readers. + +In a perfect world you would just rebuild the initramfs now and it would +work. Unfortunately there are some additional issues to address. The +most important one is pcscd. Newer versions of pcscd use HAL and dbus to +detect readers. As most people (including me) aren't too enthusiastic +about adding these two daemons to the initramfs, we will rebuild the +daemon to use the traditional polling method with libusb. Again, this +step is only necessary if your reader uses pcscd (for example the +Gemalto PC Card readers). + +To do this, download the ccid and pcsc-lite packages from +https://pcsc-lite.alioth.debian.org/ + +Install the libusb header files, extract the tarballs and build pcscd +with the following commands: + + apt-get install libusb-dev + ./configure --disable-libhal --enable-libusb + make + make install + +Now go to the ccid directory and execute these commands (the option is +only need if you use the libccidtwin.so to access your reader: + + ./configure [--enable-twinserial] + make + make install + +This installs the new pcscd and it's libraries in `/usr/local/`. To +reflect the new situation we have to change the initramfs scripts. +Edit /etc/reader.conf to instruct `pcscd` to use the new libraries (they +should be in `/usr/local/pcsc/drivers/`) instead of the ones from the Debian +package. Replace everything after line 45 in +`/usr/share/initramfs-tools/hooks/cryptopensc` with the following chunk: + + for dir in etc/opensc usr/local/pcsc var/run tmp ; do + if [ ! -d ${DESTDIR}/${dir} ] ; then mkdir -p ${DESTDIR}/${dir} ; fi + done + + # Install pcscd daemon, drivers, conf file + copy_exec /usr/local/sbin/pcscd + cp -r /usr/local/pcsc ${DESTDIR}/usr/local + cp /etc/reader.conf ${DESTDIR}/etc + cp -r /usr/local/lib ${DESTDIR}/usr/local + # Install opensc commands and conf file + copy_exec /usr/bin/opensc-tool + copy_exec /usr/bin/pkcs15-crypt + cp /etc/opensc/opensc.conf ${DESTDIR}/etc/opensc + +Edit `/usr/share/initramfs-tools/scripts/local-bottom/cryptopensc` and +`/usr/share/initramfs-tools/scripts/local-top/cryptopensc` to use the new +binary in `/usr/local/sbin/pcscd` instead of `/usr/sbin/pcscd` and change +the path in the existence test to: + + if [ ! -x /usr/local/sbin/pcscd ]; then + exit 0 + fi + +If you have completed all the steps up to now, you can update your +initramfs image with: + + update-initramfs -u -k `uname -r` + +and reboot your machine. This leaves a backup of your old initramfs in +the boot partition if something doesn't work. If you have to debug your +initramfs during boot just append the `break=mount` option to the kernel +to have a debug shell just before the root partition would be mounted. + + -- Benjamin Kiessling <benjaminkiessling@bttec.org>, Sun, 26 Jul 2009 |