[LTP] [PATCH v5 4/4] ima_tpm.sh: Fix calculating PCR aggregate

Petr Vorel
2020-12-14T22:19:46Z

for TPM 2.0 and support more evmctl versions.

Because exporting PCR registers for TPM 2.0 has not been upstreamed [1],
we use user space code, which requires evmctl >= 1.3.1 and tsspcrread.
Using evmctl allows to test for TPM devices which does not export event
log (/sys/kernel/security/tpm0/binary_bios_measurements).

For TPM 1.2 read tpm0 device's pcrs file from sysfs. (tss1pcrread could
be also used, but it's not yet packaged by distros.)

For old kernels which use SHA1/MD5, any evmctl version is required (evmctl
ima_measurement was introduced in very old v0.7), but
* newer sysctl path /sys/class/tpm/tpm0/device/pcrs requires evmctl 1.1
* using ima_policy=tcb requires 1.3.1 due --ignore-violations

We now support output format of ima_measurement command for various
evmctl versions:
* 1.3: "sha256: TPM PCR-10:" (or other algorithm, e.g. "sha1:")
* 1.1-1.2.1: "HW PCR-10:" (the only previously supported format)
* 0.7-1.0: "PCR-10:"

NOTE: we ignore evmctl failure for evmctl < 1.3.1 (missing --ignore-violations,
also evmctl < 1.1 fails with "PCRAgg does not match PCR-10")

As for previous commit fix testing with TPM 2.0 device which does not
export event log (/sys/kernel/security/tpm0/binary_bios_measurements):
not wrongly assuming TPM-bypass when kernel didn't export other TPM
2.0 files we check in get_tpm_version() but bios boot aggregate is
correct (i.e. not 0x00s). In that case evmctl ima_boot_aggregate can get
boot aggregate even without TPM event log.

[1] https://patchwork.kernel.org/patch/11759729/

Co-developed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
Changes v4->v5:
* improved TPM 2.0 detection (e.g. check for /dev/tpmrm0 and /dev/tpm0)
* test2: if evmctl ima_measurement fails, run again with --ignore-violations
* test2: assume TPM 2, if not detected
* print TPM kernel config
* cleanup

.../security/integrity/ima/tests/ima_setup.sh | 14 +-
.../security/integrity/ima/tests/ima_tpm.sh | 176 +++++++++++++-----
2 files changed, 144 insertions(+), 46 deletions(-)

diff --git a/testcases/kernel/security/integrity/ima/tests/ima_setup.sh b/testcases/kernel/security/integrity/ima/tests/ima_setup.sh
index dbf8a1db4..59a7ffeac 100644
--- a/testcases/kernel/security/integrity/ima/tests/ima_setup.sh
+++ b/testcases/kernel/security/integrity/ima/tests/ima_setup.sh
@@ -93,7 +93,7 @@ require_ima_policy_content()
fi
}

-require_ima_policy_cmdline()
+check_ima_policy_cmdline()
{
local policy="$1"
local i
@@ -101,10 +101,18 @@ require_ima_policy_cmdline()
grep -q "ima_$policy" /proc/cmdline && return
for i in $(cat /proc/cmdline); do
if echo "$i" | grep -q '^ima_policy='; then
- echo "$i" | grep -q -e "|[ ]*$policy" -e "$policy[ ]*|" -e "=$policy" && return
+ echo "$i" | grep -q -e "|[ ]*$policy" -e "$policy[ ]*|" -e "=$policy" && return 0
fi
done
- tst_brk TCONF "IMA measurement tests require builtin IMA $policy policy (e.g. ima_policy=$policy kernel parameter)"
+ return 1
+}
+
+require_ima_policy_cmdline()
+{
+ local policy="$1"
+
+ check_ima_policy_cmdline $policy || \
+ tst_brk TCONF "IMA measurement tests require builtin IMA $policy policy (e.g. ima_policy=$policy kernel parameter)"
}

mount_helper()
diff --git a/testcases/kernel/security/integrity/ima/tests/ima_tpm.sh b/testcases/kernel/security/integrity/ima/tests/ima_tpm.sh
index 195fcb16c..233fdeed8 100755
--- a/testcases/kernel/security/integrity/ima/tests/ima_tpm.sh
+++ b/testcases/kernel/security/integrity/ima/tests/ima_tpm.sh
@@ -7,13 +7,14 @@
# Verify the boot and PCR aggregates.

TST_CNT=2
-TST_NEEDS_CMDS="awk cut"
+TST_NEEDS_CMDS="awk cut tail"
TST_SETUP="setup"

. ima_setup.sh

EVMCTL_REQUIRED='1.3.1'
ERRMSG_EVMCTL="=> install evmctl >= $EVMCTL_REQUIRED"
+ERRMSG_TPM="TPM hardware support not enabled in kernel or no TPM chip found"

setup()
{
@@ -31,7 +32,7 @@ setup()

TPM_VERSION="$(get_tpm_version)"
if [ -z "$TPM_VERSION" ]; then
- tst_res TINFO "TPM hardware support not enabled in kernel or no TPM chip found, testing TPM-bypass"
+ tst_res TINFO "$ERRMSG_TPM, testing TPM-bypass"
else
tst_res TINFO "TMP major version: $TPM_VERSION"
fi
@@ -121,6 +122,93 @@ get_tpm_version()
fi
}

+read_pcr_tpm1()
+{
+ local pcrs_path="/sys/class/tpm/tpm0/device/pcrs"
+ local evmctl_required="1.1"
+ local hash pcr
+
+ if [ ! -f "$pcrs_path" ]; then
+ pcrs_path="/sys/class/misc/tpm0/device/pcrs"
+ elif ! check_evmctl $evmctl_required; then
+ echo "evmctl >= $evmctl_required required"
+ return 32
+ fi
+
+ if [ ! -f "$pcrs_path" ]; then
+ echo "missing PCR file $pcrs_path ($ERRMSG_TPM)"
+ return 32
+ fi
+
+ while read line; do
+ pcr="$(echo $line | cut -d':' -f1)"
+ hash="$(echo $line | cut -d':' -f2 | awk '{ gsub (" ", "", $0); print tolower($0) }')"
+ echo "$pcr: $hash"
+ done < $pcrs_path
+
+ return 0
+}
+
+# NOTE: TPM 1.2 would require to use tss1pcrread which is not fully adopted
+# by distros yet.
+read_pcr_tpm2()
+{
+ local pcrmax=23
+ local pcrread="tsspcrread -halg $ALGORITHM"
+ local i pcr
+
+ tst_check_cmds tsspcrread || return 1
+
+ for i in $(seq 0 $pcrmax); do
+ pcr=$($pcrread -ha "$i" -ns)
+ if [ $? -ne 0 ]; then
+ echo "tsspcrread failed: $pcr"
+ return 1
+ fi
+ printf "PCR-%02d: %s\n" $i "$pcr"
+ done
+
+ return 0
+}
+
+get_pcr10_aggregate()
+{
+ local cmd="evmctl -vv ima_measurement $BINARY_MEASUREMENTS"
+ local msg="$ERRMSG_EVMCTL"
+ local res=TCONF
+ local pcr ret
+
+ if [ -z "$MISSING_EVMCTL" ]; then
+ msg=
+ res=TFAIL
+ fi
+
+ $cmd > hash.txt 2>&1
+ ret=$?
+ if [ $ret -ne 0 -a -z "$MISSING_EVMCTL" ]; then
+ tst_res TFAIL "evmctl failed, trying with --ignore-violations"
+ cmd="$cmd --ignore-violations"
+ $cmd > hash.txt 2>&1
+ ret=$?
+ elif [ $ret -ne 0 -a "$MISSING_EVMCTL" = 1 ]; then
+ tst_brk TFAIL "evmctl failed $msg"
+ fi
+
+ [ $ret -ne 0 ] && tst_res TWARN "evmctl failed, trying to continue $msg"
+
+ pcr=$(grep -E "^($ALGORITHM: )*PCRAgg(.*10)*:" hash.txt | tail -1 \
+ | awk '{print $NF}')
+
+ if [ -z "$pcr" ]; then
+ tst_res $res "failed to find aggregate PCR-10 $msg"
+ tst_res TINFO "hash file:"
+ cat hash.txt >&2
+ return
+ fi
+
+ echo "$pcr"
+}
+
test1_tpm_bypass_mode()
{
local zero=$(echo $DIGEST | awk '{gsub(/./, "0")}; {print}')
@@ -139,8 +227,10 @@ test1_hw_tpm()
local cmd="evmctl ima_boot_aggregate -v"
local boot_aggregate

- [ -z "$TPM_VERSION" ] && \
+ if [ -z "$TPM_VERSION" ]; then
tst_res TWARN "TPM-bypass failed, trying to test TPM device (unknown TPM version)"
+ MAYBE_TPM2=1
+ fi

if [ "$MISSING_EVMCTL" = 1 ]; then
if [ ! -f "$tpm_bios" ]; then
@@ -174,57 +264,57 @@ test1()
[ -z "$TPM_VERSION" ] && test1_tpm_bypass_mode || test1_hw_tpm
}

-# Probably cleaner to programmatically read the PCR values directly
-# from the TPM, but that would require a TPM library. For now, use
-# the PCR values from /sys/devices.
-validate_pcr()
+test2()
{
- tst_res TINFO "verify PCR (Process Control Register)"
+ local hash pcr_aggregate out ret

- local dev_pcrs="$1"
- local pcr hash aggregate_pcr
+ tst_res TINFO "verify PCR values"

- aggregate_pcr="$(evmctl -v ima_measurement $BINARY_MEASUREMENTS 2>&1 | \
- grep 'HW PCR-10:' | awk '{print $3}')"
- if [ -z "$aggregate_pcr" ]; then
- tst_res TFAIL "failed to get PCR-10"
- return 1
+ if [ "$MAYBE_TPM2" = 1 ]; then
+ tst_res TINFO "TMP version not detected ($ERRMSG_TPM), assume TPM 2"
+ TPM_VERSION=2
fi

- while read line; do
- pcr="$(echo $line | cut -d':' -f1)"
- if [ "$pcr" = "PCR-10" ]; then
- hash="$(echo $line | cut -d':' -f2 | awk '{ gsub (" ", "", $0); print tolower($0) }')"
- [ "$hash" = "$aggregate_pcr" ]
- return $?
- fi
- done < $dev_pcrs
- return 1
-}
+ if [ -z "$TPM_VERSION" ]; then
+ tst_brk TCONF "TMP version not detected ($ERRMSG_TPM)"
+ fi

-test2()
-{
- tst_res TINFO "verify PCR values"
- tst_check_cmds evmctl || return
+ if [ "$ALGORITHM" = "sha1" -a "$MISSING_EVMCTL" = 1 ]; then
+ tst_check_cmds evmctl || return 1
+ fi

- tst_res TINFO "evmctl version: $(evmctl --version)"
+ out=$(read_pcr_tpm$TPM_VERSION)
+ ret=$?

- local pcrs_path="/sys/class/tpm/tpm0/device/pcrs"
- if [ -f "$pcrs_path" ]; then
- tst_res TINFO "new PCRS path, evmctl >= 1.1 required"
- else
- pcrs_path="/sys/class/misc/tpm0/device/pcrs"
+ if [ $ret -ne 0 ]; then
+ case "$ret" in
+ 1) tst_res TFAIL "$out";;
+ 32) tst_res TCONF "$out";;
+ *) tst_brk TBROK "unsupported return type '$1'";;
+ esac
+ return
fi

- if [ -f "$pcrs_path" ]; then
- validate_pcr $pcrs_path
- if [ $? -eq 0 ]; then
- tst_res TPASS "aggregate PCR value matches real PCR value"
- else
- tst_res TFAIL "aggregate PCR value does not match real PCR value"
- fi
+ hash=$(echo "$out" | grep "^PCR-10" | cut -d' ' -f2)
+
+ if [ -z "$out" ]; then
+ tst_res TFAIL "PCR-10 hash not found"
+ return
+ fi
+
+ tst_res TINFO "real PCR-10: '$hash'"
+
+ get_pcr10_aggregate > tmp.txt
+ pcr_aggregate="$(cat tmp.txt)"
+ if [ -z "$pcr_aggregate" ]; then
+ return
+ fi
+ tst_res TINFO "aggregate PCR-10: '$pcr_aggregate'"
+
+ if [ "$hash" = "$pcr_aggregate" ]; then
+ tst_res TPASS "aggregate PCR value matches real PCR value"
else
- tst_res TCONF "TPM Hardware Support not enabled in kernel or no TPM chip found"
+ tst_res TFAIL "aggregate PCR value does not match real PCR value"
fi
}

--
2.29.2