Paul Meyer
1bdf2db6f7
Measure the volume key and unlock keyslot through io.systemd.PCRExtend instead of driving the TPM directly via tpm2-util, matching how the verity and imds measurements already work. Bank selection and the TPM context now live entirely in systemd-pcrextend. As a result the tpm2-measure-bank= crypttab option can no longer be honored per volume and is now a deprecated no-op. Signed-off-by: Paul Meyer <katexochen0@gmail.com>
112 lines
4.7 KiB
Bash
Executable File
112 lines
4.7 KiB
Bash
Executable File
#!/usr/bin/env bash
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# SPDX-License-Identifier: LGPL-2.1-or-later
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set -eux
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set -o pipefail
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# Tests that systemd-cryptsetup's tpm2-measure-pcr= option measures the volume key
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# through the io.systemd.PCRExtend Varlink service.
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#
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# Note: the tpm2-measure-keyslot-nvpcr= (NvPCR) path is intentionally not covered here. NvPCRs use a
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# signed PCR policy that must be anchored first (see TEST-70-TPM2.nvpcr.sh), which is heavy setup
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# orthogonal to what this test checks; the NvPCR extend-via-pcrextend path is already covered there.
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# shellcheck source=test/units/util.sh
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. "$(dirname "$0")"/util.sh
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export SYSTEMD_LOG_LEVEL=debug
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if ! command -v systemd-cryptsetup >/dev/null || ! tpm_has_pcr sha256 15; then
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echo "systemd-cryptsetup or PCR 15 (sha256) not available, skipping cryptsetup measurement test"
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exit 0
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fi
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IMAGE=""
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at_exit() {
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if [[ $? -ne 0 ]]; then
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# Dump the event log on failure, to ease debugging
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jq --seq --slurp </run/log/systemd/tpm2-measure.log || :
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fi
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set +e
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systemd-cryptsetup detach test-volume
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rm -rf /run/systemd/system/systemd-pcrextend.socket.d
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systemctl daemon-reload
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systemctl restart systemd-pcrextend.socket
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rm -f "${IMAGE:-}" /tmp/passphrase /tmp/vk /tmp/vk-hmac.bin \
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/tmp/oldpcr15 /tmp/newpcr15 /tmp/measure-bank.log
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}
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trap at_exit EXIT
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# The socket carries ConditionSecurity=measured-os, which does not hold in the
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# test VM, so the Varlink service would never activate. Drop the condition so
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# systemd-cryptsetup can reach it, exactly like TEST-70-TPM2.pcrextend.sh does.
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mkdir -p /run/systemd/system/systemd-pcrextend.socket.d
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cat >/run/systemd/system/systemd-pcrextend.socket.d/50-no-condition.conf <<EOF
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[Unit]
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ConditionSecurity=
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EOF
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systemctl daemon-reload
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systemctl restart systemd-pcrextend.socket
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# Prepare a fresh LUKS2 volume unlocked by a passphrase keyfile
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IMAGE="$(mktemp /tmp/systemd-cryptsetup-measure-XXX.IMAGE)"
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truncate -s 20M "$IMAGE"
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echo -n passphrase >/tmp/passphrase
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chmod 0600 /tmp/passphrase
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cryptsetup luksFormat -q --pbkdf pbkdf2 --pbkdf-force-iterations 1000 --use-urandom "$IMAGE" /tmp/passphrase
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UUID="$(cryptsetup luksUUID "$IMAGE")"
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# Extract the raw volume key so we can recompute the expected HMAC below. The
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# volume key is measured as HMAC(volume_key, prefix) rather than a plain hash
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# (see cryptsetup_get_volume_key_prefix()/cryptsetup_get_volume_key_id()).
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cryptsetup luksDump -q --dump-volume-key --volume-key-file=/tmp/vk --key-file=/tmp/passphrase "$IMAGE"
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VK_HEX="$(od -An -v -tx1 /tmp/vk | tr -d ' \n')"
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# prefix = "cryptsetup:" <escaped volume name> ":" <LUKS UUID>; "test-volume"
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# contains no ':' so it is unescaped.
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PREFIX="cryptsetup:test-volume:$UUID"
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# Expected measured digest for the sha256 bank: HMAC-SHA256(volume_key, prefix)
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printf '%s' "$PREFIX" | openssl dgst -binary -sha256 -mac HMAC -macopt "hexkey:$VK_HEX" >/tmp/vk-hmac.bin
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DIGEST_EXPECTED="$(od -An -v -tx1 /tmp/vk-hmac.bin | tr -d ' \n')"
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# Remember the current event log length so we can index the record we add.
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# (json-seq: each record is RS(0x1e)-prefixed, LF-suffixed.) The log is created
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# lazily on the first measurement, and this subtest may be the first thing to
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# measure (e.g. when run in isolation), so treat an absent log as zero records.
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RECORD_COUNT=0
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if [[ -f /run/log/systemd/tpm2-measure.log ]]; then
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RECORD_COUNT="$(jq --seq --slurp '. | length' </run/log/systemd/tpm2-measure.log | tr -d '\036')"
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fi
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tpm2_pcrread sha256:15 -Q -o /tmp/oldpcr15
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# Activate with measurement enabled. Unlock is via the keyfile (no TPM unlock),
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# to prove measurement is independent of the unlock mechanism.
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SYSTEMD_FORCE_MEASURE=1 systemd-cryptsetup attach test-volume "$IMAGE" /tmp/passphrase \
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tpm2-measure-pcr=15,headless=1
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tpm2_pcrread sha256:15 -Q -o /tmp/newpcr15
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# The TPM PCR 15 must have been extended with the HMAC:
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# new = sha256(old || HMAC(volume_key, prefix))
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diff /tmp/newpcr15 \
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<(cat /tmp/oldpcr15 /tmp/vk-hmac.bin | openssl dgst -binary -sha256)
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# The volume-key measurement is the record we just added (the first one past RECORD_COUNT).
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test "$(jq --seq --slurp ".[$RECORD_COUNT].pcr" </run/log/systemd/tpm2-measure.log)" == "$(printf '\x1e15')"
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DIGEST_CURRENT="$(jq --seq --slurp --raw-output ".[$RECORD_COUNT].digests[] | select(.hashAlg == \"sha256\").digest" </run/log/systemd/tpm2-measure.log)"
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test "$DIGEST_CURRENT" == "$DIGEST_EXPECTED"
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systemd-cryptsetup detach test-volume
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# The deprecated tpm2-measure-bank= option must warn but not fail.
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SYSTEMD_FORCE_MEASURE=1 systemd-cryptsetup attach test-volume "$IMAGE" /tmp/passphrase \
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tpm2-measure-pcr=15,tpm2-measure-bank=sha256,headless=1 |& tee /tmp/measure-bank.log
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systemd-cryptsetup detach test-volume
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grep -i "deprecated" /tmp/measure-bank.log >/dev/null
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