On Mon, May 06, 2024 at 02:09:12PM -0500, Glenn Washburn wrote:
> On Fri, 3 May 2024 14:48:56 +0800
> Gary Lin <g...@suse.com> wrote:
>
> > For the tpm2 module, the TCG2 command submission function is the only
> > difference between the a QEMU instance and grub-emu. To test TPM key
> > unsealing with a QEMU instance, it requires an extra OS image to invoke
> > grub-protect to seal the LUKS key, rather than a simple grub-shell rescue
> > CD image. On the other hand, grub-emu can share the emulated TPM device
> > with the host, so that we can seal the LUKS key on host and test key
> > unsealing with grub-emu.
> >
> > This test script firstly creates a simple LUKS image to be loaded as a
> > loopback device in grub-emu. Then an emulated TPM device is created by
> > swtpm_cuse and PCR 0 and 1 are extended.
> >
> > There are several test cases in the script to test various settings. Each
> > test case uses grub-protect or tpm2-tools to seal the LUKS password
> > against PCR 0 and PCR 1. Then grub-emu is launched to load the LUKS image,
> > try to mount the image with tpm2_key_protector_init and cryptomount, and
> > verify the result.
> >
> > Based on the idea from Michael Chang.
> >
> > Cc: Michael Chang <mch...@suse.com>
> > Cc: Stefan Berger <stef...@linux.ibm.com>
> > Cc: Glenn Washburn <developm...@efficientek.com>
> > Signed-off-by: Gary Lin <g...@suse.com>
> > ---
> > Makefile.util.def | 6 +
> > tests/tpm2_test.in | 306 +++++++++++++++++++++++++++++++++++++++
> > tests/util/grub-shell.in | 6 +-
> > 3 files changed, 317 insertions(+), 1 deletion(-)
> > create mode 100644 tests/tpm2_test.in
> >
> > diff --git a/Makefile.util.def b/Makefile.util.def
> > index 40bfe713d..8d4c53a03 100644
> > --- a/Makefile.util.def
> > +++ b/Makefile.util.def
> > @@ -1281,6 +1281,12 @@ script = {
> > common = tests/asn1_test.in;
> > };
> >
> > +script = {
> > + testcase = native;
> > + name = tpm2_test;
> > + common = tests/tpm2_test.in;
> > +};
> > +
> > program = {
> > testcase = native;
> > name = example_unit_test;
> > diff --git a/tests/tpm2_test.in b/tests/tpm2_test.in
> > new file mode 100644
> > index 000000000..75c042274
> > --- /dev/null
> > +++ b/tests/tpm2_test.in
> > @@ -0,0 +1,306 @@
> > +#! @BUILD_SHEBANG@ -e
> > +
> > +# Test GRUBs ability to unseal a LUKS key with TPM 2.0
> > +# Copyright (C) 2024 Free Software Foundation, Inc.
> > +#
> > +# GRUB is free software: you can redistribute it and/or modify
> > +# it under the terms of the GNU General Public License as published by
> > +# the Free Software Foundation, either version 3 of the License, or
> > +# (at your option) any later version.
> > +#
> > +# GRUB is distributed in the hope that it will be useful,
> > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > +# GNU General Public License for more details.
> > +#
> > +# You should have received a copy of the GNU General Public License
> > +# along with GRUB. If not, see <http://www.gnu.org/licenses/>.
> > +
> > +grubshell=@builddir@/grub-shell
> > +
> > +. "@builddir@/grub-core/modinfo.sh"
> > +
> > +if [ x${grub_modinfo_platform} != xemu ]; then
> > + exit 77
> > +fi
> > +
> > +builddir="@builddir@"
> > +
> > +# Force build directory components
> > +PATH="${builddir}:${PATH}"
> > +export PATH
> > +
> > +if [ "x${EUID}" = "x" ] ; then
>
> Braces in quoted variables at the end of the quoted string don't need
> braces. But no need to change it back.
>
> > + EUID=`id -u`
> > +fi
> > +
> > +if [ "${EUID}" != 0 ] ; then
> > + echo "not root; cannot test tpm2."
> > + exit 99
> > +fi
> > +
> > +if ! command -v cryptsetup >/dev/null 2>&1; then
> > + echo "cryptsetup not installed; cannot test tpm2."
> > + exit 99
> > +fi
> > +
> > +if ! grep -q tpm_vtpm_proxy /proc/modules && ! modprobe tpm_vtpm_proxy;
> > then
> > + echo "no tpm_vtpm_proxy support; cannot test tpm2."
> > + exit 99
> > +fi
> > +
> > +if ! command -v swtpm >/dev/null 2>&1; then
> > + echo "swtpm not installed; cannot test tpm2."
> > + exit 99
> > +fi
> > +
> > +if ! command -v tpm2_startup >/dev/null 2>&1; then
> > + echo "tpm2-tools not installed; cannot test tpm2."
> > + exit 99
> > +fi
> > +
> > +tpm2testdir="`mktemp -d "${TMPDIR:-/tmp}/$(basename "$0").XXXXXXXXXX"`" ||
> > exit 99
> > +
> > +disksize=20M
> > +
> > +luksfile=${tpm2testdir}/luks.disk
>
> Its a good idea to have variables that can be user provided and thus
> have spaces to be quoted. tpm2testdir and any variable contructed from
> it fall in that category. Note that putting a variable in braces
> unquoted, does not make implicit quoting.
>
Ok, will quote those variables.
> > +lukskeyfile=${tpm2testdir}/password.txt
> > +
> > +# Choose a low iteration number to reduce the time to decrypt the disk
> > +csopt="--type luks2 --pbkdf pbkdf2 --iter-time 1000"
> > +
> > +tpm2statedir=${tpm2testdir}/tpm
> > +tpm2ctrl=${tpm2statedir}/ctrl
> > +tpm2log=${tpm2statedir}/logfile
> > +
> > +sealedkey=${tpm2testdir}/sealed.tpm
> > +
> > +timeout=20
> > +
> > +testoutput=${tpm2testdir}/testoutput
> > +
> > +vtext="TEST VERIFIED"
> > +
> > +ret=0
> > +
> > +# Create the password file
> > +echo -n "top secret" > ${lukskeyfile}
> > +
> > +# Setup LUKS2 image
> > +truncate -s ${disksize} ${luksfile} || exit 21
> > +cryptsetup luksFormat -q ${csopt} ${luksfile} ${lukskeyfile} || exit 22
>
> You should never be exiting with an explicit value other than 77 or 99.
> Everything else indicates a real failure in the test. I think you got
> confused by reading grub-shell-luks-tester and seeing that it does not
> follow that rule. The reason for that is because it is expected that
> scripts using it will convert those exit codes to 99. Take a look at
> grub_cmd_cryptomount and you will see that in the _testcase function.
> So the big difference in this script and grub-shell-luks-tester is that
> this script is run directly by the test harness, but
> grub-shell-luks-tester is not. Please change the rest of the exit
> codes to 99.
>
Thanks for the explanation. I'll change the exit codes to 99.
> > +
> > +# Write vtext into the first block of the LUKS2 image
> > +luksdev=/dev/mapper/`basename ${tpm2testdir}`
> > +cryptsetup open --key-file ${lukskeyfile} ${luksfile} `basename
> > ${luksdev}` || exit 23
> > +echo "${vtext}" | dd of=${luksdev} conv=notrunc status=none
>
> I would think `echo "${vtext}" | cat > "${luksdev}"` would be sufficient
> here. I'm curious if I'm wrong about that. Certainly "conv=notrunc"
> seems superfluous as ${luksdev} is a device so no truncation happens
> anyway. If true, then as is it may be confusing to readers. In general,
> I think its better to use simpler commands when available (in this case
> no need for arg parsing).
>
Oh, I copied the code from my test script which works on a blank file
and forgot to change it. The dd command is certainly unnecessary here.
> > +cryptsetup close ${luksdev}
> > +
> > +# Shutdown the swtpm instance on exit
> > +cleanup() {
> > + RET=$?
> > + if [ -e "${tpm2ctrl}" ]; then
> > + swtpm_ioctl -s --unix ${tpm2ctrl}
> > + fi
> > + if [ "${RET}" -eq 0 ]; then
> > + rm -rf "$tpm2testdir" || :
> > + fi
> > +}
> > +trap cleanup EXIT INT TERM KILL QUIT
> > +
> > +mkdir -p ${tpm2statedir}
> > +
> > +# Create the swtpm chardev instance
> > +swtpm chardev --vtpm-proxy --tpmstate dir=${tpm2statedir} \
> > + --tpm2 --ctrl type=unixio,path=${tpm2ctrl} \
> > + --flags startup-clear --daemon > ${tpm2log} || ret=$?
> > +if [ "${ret}" -ne 0 ]; then
> > + echo "Failed to start swtpm chardev"
> > + exit ${ret}
>
> This should also exit with 99, as this is not an actual failure of the
> test, but a failure to setup the test. You could put the $ret in the
> message echo'd, which would be helpful to someone debugging this
> failure.
>
Copy that.
> > +fi
> > +
> > +# Wait for tpm2 chardev
> > +wait_count=3
> > +for count in `seq 1 ${wait_count}`; do
>
> Considering that this may run in a virtual machine where things will be
> going much slower, perhaps instead use:
>
> `seq 1 ${tpm2timeout}`
>
> And above after setting tpm2log, have a line like:
>
> tpm2timeout=${GRUB_TEST_SWTPM_DEFAULT_TIMEOUT:-3}
>
> This way this timeout can be overridden if needed.
>
Good idea. I'll change the timeout variable.
> > + sleep 1
> > +
> > + tpm2dev=$(grep "New TPM device" ${tpm2log} | cut -d' ' -f 4)
> > + if [ -c "${tpm2dev}" ]; then
> > + wait_count=0
> > + break
> > + fi
> > +done
> > +if [ "${wait_count}" -ne 0 ]; then
>
> I thought we agreed that it would be better to use [ -z "$tmp2log" ]
> here. In which case, the wait_count variable seem unnecessary.
>
Ah, I forgot to mention that I ran into a situation that tpm2dev was
fetched but the char device was actually not ready, so I'd like to make
sure that tpm2dev is really available.
> > + echo "TPM device did not appear."
> > + exit QUIT
>
> I believe this invalid usage of the exit command (I get errors using
> this in both bash and sh). Regardless we should be exiting with 99 here.
>
Will fix it.
> > +fi
> > +
> > +# Export the TCTI variable for tpm2-tools
> > +export TPM2TOOLS_TCTI="device:${tpm2dev}"
> > +
> > +# Extend PCR 0
> > +tpm2_pcrextend 0:sha256=$(echo "test0" | sha256sum | cut -d ' ' -f 1)
> > +
> > +# Extend PCR 1
> > +tpm2_pcrextend 1:sha256=$(echo "test1" | sha256sum | cut -d ' ' -f 1)
>
> Both of the above commands should have " || exit 99" at the end to make
> these hard errors.
>
Got it
> > +
> > +tpm2_seal_unseal() {
> > + srk_alg="$1"
> > + handle_type="$2"
> > + srk_test="$3"
> > +
> > + grub_srk_alg=${srk_alg}
> > +
> > + extra_opt=""
> > + extra_grub_opt=""
> > +
> > + persistent_handle="0x81000000"
> > +
> > + if [ "${handle_type}" = "persistent" ]; then
> > + extra_opt="--tpm2-srk=${persistent_handle}"
> > + fi
> > +
> > + if [ "${srk_alg}" != "default" ]; then
> > + extra_opt="${extra_opt} --tpm2-asymmetric=${srk_alg}"
> > + fi
> > +
> > + # Seal the password with grub-protect
> > + grub-protect ${extra_opt} \
> > + --tpm2-device=${tpm2dev} \
> > + --action=add \
> > + --protector=tpm2 \
> > + --tpm2key \
> > + --tpm2-bank=sha256 \
> > + --tpm2-pcrs=0,1 \
> > + --tpm2-keyfile=${lukskeyfile} \
> > + --tpm2-outfile=${sealedkey} || ret=$?
> > + if [ "${ret}" -ne 0 ]; then
> > + echo "Failed to seal the secret key"
> > + exit 1
>
> The error code should be 99 as this is a hard error (ie a failure in
> the setup). Perhaps this should be a "return" instead of "exit"
> statement. This allows the caller to handle this. Since currently the
> caller does nothing, using either one is effectively the same, but I
> think return is better. Same for other uses of exit in functions.
>
Originally the return status was handled outside this function and it
ended up with several duplicate code. To improve the readability, I
moved the error handling code inside the function and made it exit
directly. I'll flip 'exit' back to 'return' and handle the return status
with a shorter code.
> > + fi
> > +
> > + # Flip the asymmetric algorithm in grub.cfg to trigger fallback SRKs
> > + if [ "${srk_test}" = "fallback_srk" ]; then
> > + if [ -z "${srk_alg##RSA*}" ]; then
> > + grub_srk_alg="ECC"
> > + elif [ -z "${srk_alg##ECC*}" ]; then
> > + grub_srk_alg="RSA"
> > + fi
> > + fi
> > +
> > + if [ "${grub_srk_alg}" != "default" ] && [ "${handle_type}" !=
> > "persistent" ]; then
> > + extra_grub_opt="-a ${grub_srk_alg}"
> > + fi
> > +
> > + # Write the TPM unsealing script
> > + cat > ${tpm2testdir}/testcase.cfg <<EOF
> > +loopback luks (host)${luksfile}
> > +tpm2_key_protector_init -T (host)${sealedkey} ${extra_grub_opt}
> > +if cryptomount -a --protector tpm2; then
> > + cat (crypto0)+1
> > +fi
> > +EOF
> > +
> > + # Test TPM unsealing with the same PCR
> > + ${grubshell} --timeout=${timeout} --emu-opts="-t ${tpm2dev}" <
> > ${tpm2testdir}/testcase.cfg > ${testoutput} || ret=$?
> > +
> > + # Remove the persistent handle
> > + if [ "${handle_type}" = "persistent" ]; then
> > + grub-protect \
> > + --tpm2-device=${tpm2dev} \
> > + --protector=tpm2 \
> > + --action=remove \
> > + --tpm2-srk=${persistent_handle} \
> > + --tpm2-evict
>
> Probably should " || :" here to ignore a potential failure?
>
Got it.
> > + fi
> > +
> > + if [ "${ret}" -eq 0 ]; then
> > + if ! grep -q "^${vtext}$" "${testoutput}"; then
> > + echo "error: test not verified [`cat ${testoutput}`]" >&2
> > + exit 1
>
> return as mentioned above.
>
> > + fi
> > + else
> > + echo "grub-emu exited with error: ${ret}" >&2
> > + exit ${ret}
>
> ditto
>
> > + fi
> > +}
> > +
> > +tpm2_seal_unseal_nv() {
> > + persistent_handle="0x81000000"
> > + primary_file=${tpm2testdir}/primary.ctx
> > + session_file=${tpm2testdir}/session.dat
> > + policy_file=${tpm2testdir}/policy.dat
> > + keypub_file=${tpm2testdir}/key.pub
> > + keypriv_file=${tpm2testdir}/key.priv
> > + name_file=${tpm2testdir}/sealing.name
> > + sealing_ctx_file=${tpm2testdir}/sealing.ctx
> > +
> > + # Since we don't run a resource manager on our swtpm instance, it has
> > + # to flush the transient handles after tpm2_createprimary, tpm2_create
> > + # and tpm2_load to avoid the potential out-of-memory (0x902) errors.
> > + # Ref:
> > https://github.com/tpm2-software/tpm2-tools/issues/1338#issuecomment-469689398
> > +
> > + # Create the primary object
> > + tpm2_createprimary -C o -g sha256 -G ecc -c ${primary_file} -Q
> > + tpm2_flushcontext -t
> > +
> > + # Create the policy object
> > + tpm2_startauthsession -S ${session_file}
> > + tpm2_policypcr -S ${session_file} -l sha256:0,1 -L ${policy_file} -Q
> > + tpm2_flushcontext ${session_file}
> > +
> > + # Seal the key into TPM
> > + tpm2_create -C ${primary_file} -u ${keypub_file} -r ${keypriv_file} -L
> > ${policy_file} -i ${lukskeyfile} -Q
> > + tpm2_flushcontext -t
> > + tpm2_load -C ${primary_file} -u ${keypub_file} -r ${keypriv_file} -n
> > ${name_file} -c ${sealing_ctx_file}
> > + tpm2_flushcontext -t
> > + tpm2_evictcontrol -C o -c ${sealing_ctx_file} ${persistent_handle} -Q
>
> All of these can fail and their failure should cause a 99 error code.
> Perhaps wrap them in a subshell and do " || return 99".
>
Will move them into another shell script.
> > +
> > + # Write the TPM unsealing script
> > + cat > ${tpm2testdir}/testcase.cfg <<EOF
> > +loopback luks (host)${luksfile}
> > +tpm2_key_protector_init --mode=nv --nvindex=${persistent_handle} --pcrs=0,1
> > +if cryptomount -a --protector tpm2; then
> > + cat (crypto0)+1
> > +fi
> > +EOF
> > +
> > + # Test TPM unsealing with the same PCR
> > + ${grubshell} --timeout=${timeout} --emu-opts="-t ${tpm2dev}" <
> > ${tpm2testdir}/testcase.cfg > ${testoutput} || ret=$?
> > +
> > + # Remove the persistent handle
> > + grub-protect \
> > + --tpm2-device=${tpm2dev} \
> > + --protector=tpm2 \
> > + --action=remove \
> > + --tpm2-srk=${persistent_handle} \
> > + --tpm2-evict
>
> ||:, as mentioned above
>
> > +
> > + if [ "${ret}" -eq 0 ]; then
> > + if ! grep -q "^${vtext}$" "${testoutput}"; then
> > + echo "error: test not verified [`cat ${testoutput}`]" >&2
> > + exit 1
>
> return
>
> > + fi
> > + else
> > + echo "grub-emu exited with error: ${ret}" >&2
> > + exit ${ret}
>
> return
>
Will fix the return code.
Gary Lin
> Glenn
>
> > + fi
> > +}
> > +
> > +tpm2_seal_unseal default transient no_fallback_srk
> > +
> > +tpm2_seal_unseal RSA transient no_fallback_srk
> > +
> > +tpm2_seal_unseal ECC transient no_fallback_srk
> > +
> > +tpm2_seal_unseal RSA persistent no_fallback_srk
> > +
> > +tpm2_seal_unseal ECC persistent no_fallback_srk
> > +
> > +tpm2_seal_unseal RSA transient fallback_srk
> > +
> > +tpm2_seal_unseal ECC transient fallback_srk
> > +
> > +tpm2_seal_unseal_nv
> > +
> > +exit 0
> > diff --git a/tests/util/grub-shell.in b/tests/util/grub-shell.in
> > index 496e1bab3..6847d869e 100644
> > --- a/tests/util/grub-shell.in
> > +++ b/tests/util/grub-shell.in
> > @@ -75,6 +75,7 @@ work_directory=${WORKDIR:-`mktemp -d
> > "${TMPDIR:-/tmp}/grub-shell.XXXXXXXXXX"`} |
> >
> > . "${builddir}/grub-core/modinfo.sh"
> > qemuopts=
> > +emuopts=
> > serial_port=com0
> > serial_null=
> > halt_cmd=halt
> > @@ -281,6 +282,9 @@ for option in "$@"; do
> > --qemu-opts=*)
> > qs=`echo "$option" | sed -e 's/--qemu-opts=//'`
> > qemuopts="$qemuopts $qs" ;;
> > + --emu-opts=*)
> > + qs=`echo "$option" | sed -e 's/--emu-opts=//'`
> > + emuopts="$emuopts $qs" ;;
> > --disk=*)
> > dsk=`echo "$option" | sed -e 's/--disk=//'`
> > if [ ${grub_modinfo_platform} = emu ]; then
> > @@ -576,7 +580,7 @@ elif [ x$boot = xemu ]; then
> > cat >"$work_directory/run.sh" <<EOF
> > #! @BUILD_SHEBANG@
> > SDIR=\$(realpath -e \${0%/*})
> > -exec "$(realpath -e "${builddir}")/grub-core/grub-emu" -m
> > "\$SDIR/${device_map##*/}" --memdisk "\$SDIR/${roottar##*/}" -r memdisk -d
> > "/boot/grub"
> > +exec "$(realpath -e "${builddir}")/grub-core/grub-emu" -m
> > "\$SDIR/${device_map##*/}" --memdisk "\$SDIR/${roottar##*/}" -r memdisk -d
> > "/boot/grub" ${emuopts}
> > EOF
> > else
> > cat >"$work_directory/run.sh" <<EOF
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