Re: [PATCH v14 20/20] tests: Add tpm2_test

[Glenn Washburn]

On Tue, 7 May 2024 16:19:19 +0800
Gary Lin <glin@suse.com> wrote:

> On Mon, May 06, 2024 at 02:09:12PM -0500, Glenn Washburn wrote:
> > On Fri,  3 May 2024 14:48:56 +0800
> > Gary Lin <glin@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 <mchang@suse.com>
> > > Cc: Stefan Berger <stefanb@linux.ibm.com>
> > > Cc: Glenn Washburn <development@efficientek.com>
> > > Signed-off-by: Gary Lin <glin@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.

I meant to say '[ -z "$tpm2dev" ]', but I think you understood. But
even that isn't quite right and I should have said '[ -c "$tpm2dev" ]'.
Did you try the "-c" test and it succeeded while the device really
wasn't available? That test should work (because that's what sets
wait_count) and would be preferable to checking wait_count.

> 
> > > +    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.

Since these commands aren't generally useful outside this specific
context, I don't think another shell script would be desirable. Just
wrap them in a subshell, or wrap them in a new function.

Glenn

> 
> > > +
> > > +    # 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