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Auto-unlock ZFS native encrypted root filesystem using TPM2-tools v4.x
Signed-off-by: Garrett Fields <ghfields@gmail.com>
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‎cmd/Makefile.am

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SUBDIRS = zfs zpool zdb zhack zinject zstream zstreamdump ztest
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SUBDIRS += fsck_zfs vdev_id raidz_test zfs_ids_to_path
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SUBDIRS += fsck_zfs vdev_id raidz_test zfs_ids_to_path tpm2_autounlock
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if USING_PYTHON
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SUBDIRS += arcstat arc_summary dbufstat

‎cmd/tpm2_autounlock/Makefile.am

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dist_sbin_SCRIPTS = tpm2_autounlock.sh

‎cmd/tpm2_autounlock/tpm2_autounlock.sh

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#! /bin/bash
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# Default variables
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# If password is stored in "defaultpassword" field, ensure the security of the file.
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defaultpassword=""
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defaulttpmindex="0x1800016"
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defaulttpmpcrs="sha256:0,1,2,3,8,9"
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helpmsg() {
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echo "tpm2_autounlock.sh -- configure the TPM 2.0 chip for zfs autounlock"
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echo ""
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echo "Usage: <-c, -v, or -n> -i <val>, -p <val>, -P <val>, -r <val>"
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echo ""
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echo "Modes: (choose up to one)"
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echo "-c or --clearonly Clear TPM and ZFS properties only"
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echo "-v or --verifyonly Check current contents of TPM"
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echo "-n or --nvlockonly Lock the ability to read password until reboot"
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echo "Not selecting any of the above will initialize the TPM for autounlock"
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echo ""
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echo "Options to override defaults:"
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echo "-i or --index TPM NVRAM index (default: 0x1800016)"
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echo "-p or --password Drive unlock password (default: <none provided>)"
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echo "-P or --pcrs PCRS evaluated at unlock (default: sha256:0,1,2,3)"
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echo "-r or --rootfs Rootfs being processed (default: current booted rootfs)"
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echo "The password can also be piped to tpm2_autounlock.sh, though '-p' takes precedence"
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}
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tpm_session_execute() {
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tpm2_startauthsession -Q ${define_policy} --session=s.dat
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tpm2_policypassword -Q --session=s.dat
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tpm2_policypcr -Q --pcr-list="$tpmpcrs" --session=s.dat --policy=policy.dat
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eval "${cmd}"
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returnval=$?
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tpm2_flushcontext s.dat
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rm s.dat
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rm policy.dat
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unset define_policy
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unset cmd
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return $returnval
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}
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# Check for root permissions
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if [ $(id -u) -ne 0 ]; then
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echo "This script must be run as root"
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helpmsg
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exit 1
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fi
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# Check for presence of needed programs
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command -v zfs >/dev/null 2>&1 &&
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[ $(zfs version | grep zfs-0 | awk -F 'zfs-0' '{print $2}' | awk -F '.' '{print $2}') -ge 8 ] \
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|| { echo >&2 "zfs 0.8 or greater required, but not found. Aborting."; exit 1; }
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for i in tpm2_startauthsession tpm2_policypassword tpm2_policypcr tpm2_flushcontext tpm2_nvdefine tpm2_nvwrite tpm2_nvread; do
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command -v $i >/dev/null 2>&1 &&
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[ $($i -v | awk -F 'version=' '{print $2}' | awk -F '"' '{print $2}' | awk -F '.' '{print $1}') -ge 4 ] \
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|| { echo >&2 "'$i' version 4.0 or greater required, but not found. Aborting."; exit 1; }
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done
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# Check for presence of TPM 2.0 Hardware
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if [ $(cat /sys/module/tpm/version) != "2.0" ]; then
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echo "TPM 2.0 not found on system"
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exit 1
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fi
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# Process user entered arguments
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while [ "$1" != "" ]; do
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case $1 in
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-i | --index ) shift; tpmindex=$1;;
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-P | --pcrs ) shift; tpmpcrs=$1;;
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-r | --rootfs ) shift; rootfs=$1;;
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-p | --password ) shift; password=$1;;
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-v | --verifyonly ) verifyonly=1;;
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-c | --clearonly ) clearonly=1;;
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-n | --nvlockonly ) nvlockonly=1;;
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-h | --help ) helpmsg; exit 0;;
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* ) helpmsg; exit 1;;
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esac
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shift
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done
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# Use -r or --rootfs value if specified, otherwise try to detect running rootfs
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if [ -z "$rootfs" ]; then
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rootfs=$(zfs mount |awk '$2 == "/" { print $1 }')
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if [ -z "$rootfs" ]; then
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echo "Rootfs not specified (-r / --rootfs) and current rootfs could not be determined"
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exit 1
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fi
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fi
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# With rootfs determined, find the encryptionroot and its guid
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ENCRYPTIONROOT=$(zfs get -H -o value encryptionroot "${rootfs}")
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rootguid=$(zfs get guid -o value -H "${ENCRYPTIONROOT}")
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# Use -i or --index value if specified, otherwise look for existing property, and finally fallback to script default
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if [ -z "$tpmindex" ]; then
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tpmindex=$(zfs get -H -o value org.zfsonlinux.tpm2:index "${ENCRYPTIONROOT}")
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if [ "$tpmindex" = "-" ]; then
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tpmindex="$defaulttpmindex"
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fi
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fi
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# Use -P or --pcrs value if specified, otherwise look for existing property, and finally fallback to script default
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if [ -z "$tpmpcrs" ]; then
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tpmpcrs=$(zfs get -H -o value org.zfsonlinux.tpm2:pcrs "${ENCRYPTIONROOT}")
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if [ "$tpmpcrs" = "-" ]; then
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tpmpcrs="$defaulttpmpcrs"
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fi
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fi
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# If password is needed, use argument, piped, "script default" or stdin, in that order
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if [ -z "$password" ] && (( verifyonly+clearonly+nvlockonly == 0)); then
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[[ -p /dev/stdin ]] && { mapfile -t; set -- "${MAPFILE[@]}"; set -- $@; }
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pipepassword="$@"
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if [ -n "$pipepassword" ]; then
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password="$pipepassword"
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elif [ -n "$defaultpassword" ]; then
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password="$defaultpassword"
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else
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while true; do
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read -s -p "Drive unlock password: " password
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echo
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read -s -p "Confirm Password: " password2
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echo
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[ "$password" = "$password2" ] && break
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echo "Please try again"
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done
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fi
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fi
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# Check for invalid arguments
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if (( verifyonly+clearonly+nvlockonly > 1)) ; then
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echo " You can only select only one of the following: verifyonly, clearonly, or nvlockonly"
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exit 1
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fi
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########################################
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# Start execution
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if [ $clearonly ]; then
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tpm2_nvundefine "$tpmindex" >/dev/null 2>&1
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zfs inherit org.zfsonlinux.tpm2:index "${ENCRYPTIONROOT}"
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zfs inherit org.zfsonlinux.tpm2:pcrs "${ENCRYPTIONROOT}"
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elif [ $verifyonly ]; then
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echo "Attempting to read TPM index '$tpmindex' locked with pcrs '$tpmpcrs' and guid '$rootguid'."
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define_policy="--policy"
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cmd="tpm2_nvread ${tpmindex} --auth=session:s.dat+${rootguid}"
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tpm_session_execute
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if [ $? = 0 ]; then
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echo "is the stored password."
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# else
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# The tpm2_nvread stdout messages will be visible to user
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fi
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elif [ $nvlockonly ]; then
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define_policy="--policy"
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cmd="tpm2_nvreadlock ${tpmindex} --auth=session:s.dat+${rootguid}"
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tpm_session_execute
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else
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# Preemptively clear the tpm index
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tpm2_nvundefine "$tpmindex" >/dev/null 2>&1
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# Define NVRAM location and its access rules
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cmd="tpm2_nvdefine ${tpmindex} -Q --hierarchy=o --index-auth=${rootguid} --size=512 --policy=policy.dat --attributes='policyread|policywrite|read_stclear'"
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tpm_session_execute
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# Write password to NVRAM location
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define_policy="--policy"
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cmd="echo $password | tpm2_nvwrite ${tpmindex} -Q --auth=session:s.dat+${rootguid} --input=-"
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tpm_session_execute
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echo "Note: Password storage can be verified with '--verifyonly' until reboot or locked manually with '--nvlockonly'."
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# Store zfs filesystem properties
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zfs set org.zfsonlinux.tpm2:index="$tpmindex" "${ENCRYPTIONROOT}"
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zfs set org.zfsonlinux.tpm2:pcrs="$tpmpcrs" "${ENCRYPTIONROOT}"
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fi

‎configure.ac

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cmd/fsck_zfs/Makefile
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cmd/mount_zfs/Makefile
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cmd/raidz_test/Makefile
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cmd/tpm2_autounlock/Makefile
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cmd/vdev_id/Makefile
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cmd/zdb/Makefile
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cmd/zed/Makefile

‎contrib/initramfs/hooks/zfs.in

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@@ -106,4 +106,15 @@ if [ ! -x "$DESTDIR/usr/bin/net" ]; then
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chmod +x "$DESTDIR/usr/bin/net"
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fi
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#These are optional files to support tpm2-autounlock
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if [ -x /usr/bin/tpm2_startauthsession ]; then
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copy_exec /usr/bin/tpm2_nvread
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copy_exec /usr/bin/tpm2_nvreadlock
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copy_exec /usr/bin/tpm2_startauthsession
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copy_exec /usr/bin/tpm2_policypassword
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copy_exec /usr/bin/tpm2_policypcr
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copy_modules_dir kernel/drivers/char/tpm
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copy_exec /usr/lib/x86_64-linux-gnu/libtss2-tcti-device.so.0
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fi
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exit 0

‎contrib/initramfs/scripts/zfs

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@@ -414,6 +414,26 @@ decrypt_fs()
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[ "$KEYSTATUS" = "unavailable" ] || return 0
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TRY_COUNT=3
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# Attempt to use TPM to auto-unlock
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tpmindex="$(get_fs_value "$ENCRYPTIONROOT" org.zfsonlinux.tpm2:index)"
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tpmpcrs="$(get_fs_value "$ENCRYPTIONROOT" org.zfsonlinux.tpm2:pcrs)"
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if ! [ "$tpmindex" = "-" ] ; then
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rootguid="$(get_fs_value "$ENCRYPTIONROOT" guid)"
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tpm2_startauthsession --policy --session=s.dat
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tpm2_policypassword -Q --session=s.dat
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tpm2_policypcr -Q --pcr-list="$tpmpcrs" --session=s.dat
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tpm2_nvread "$tpmindex" --auth=session:s.dat+"$rootguid" | tr -d '\0' \
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| eval $ZFS load-key "${ENCRYPTIONROOT}"
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if [ $? = 0 ]; then
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#Lock the index from further reading until reboot
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tpm2_startauthsession --policy --session=s.dat
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tpm2_policypassword -Q --session=s.dat
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tpm2_policypcr -Q --pcr-list="$tpmpcrs" --session=s.dat
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tpm2_nvreadlock "$tpmindex" --auth=session:s.dat+"$rootguid" >> /dev/null
433+
return 0
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fi
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fi
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# If key is stored in a file, do not prompt
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if ! [ "${KEYLOCATION}" = "prompt" ]; then
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$ZFS load-key "${ENCRYPTIONROOT}"

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