Add measurement reader (#1381)

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

CMakeLists.txt

@@ -16,7 +16,7 @@ set(CLI_BUILD_TAGS "" CACHE STRING "Tags passed to go build of Constellation CLI
 enable_testing()
 
 #
-# core-os disk-mapper
+# disk-mapper
 #
 add_custom_target(disk-mapper ALL
   DOCKER_BUILDKIT=1 docker build -o ${CMAKE_BINARY_DIR} --build-arg PROJECT_VERSION="${PROJECT_VERSION}" -f Dockerfile.build --target disk-mapper .
@@ -24,6 +24,15 @@ add_custom_target(disk-mapper ALL
   BYPRODUCTS disk-mapper
 )
 
+#
+# measurement-reader
+#
+add_custom_target(measurement-reader ALL
+  DOCKER_BUILDKIT=1 docker build -o ${CMAKE_BINARY_DIR} --build-arg PROJECT_VERSION="${PROJECT_VERSION}" -f Dockerfile.build --target measurement-reader .
+  WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+  BYPRODUCTS measurement-reader
+)
+
 #
 # bootstrapper
 #

Dockerfile.build

@@ -42,6 +42,11 @@ WORKDIR /constellation/upgrade-agent/
 ARG PROJECT_VERSION
 RUN --mount=type=cache,target=/root/.cache/go-build go build -o upgrade-agent -ldflags "-s -w -buildid='' -X github.com/edgelesssys/constellation/v2/internal/constants.versionInfo=${PROJECT_VERSION}" ./cmd/
 
+FROM build AS build-measurement-reader
+WORKDIR /constellation/measurement-reader/
+
+RUN --mount=type=cache,target=/root/.cache/go-build go build -o measurement-reader -ldflags "-s -w -buildid=''" ./cmd/
+
 FROM scratch AS bootstrapper
 COPY --from=build-bootstrapper /constellation/bootstrapper/bootstrapper /
 
@@ -50,3 +55,6 @@ COPY --from=build-disk-mapper /constellation/disk-mapper/disk-mapper /
 
 FROM scratch AS upgrade-agent
 COPY --from=build-upgrade-agent /constellation/upgrade-agent/upgrade-agent /
+
+FROM scratch AS measurement-reader
+COPY --from=build-measurement-reader /constellation/measurement-reader/measurement-reader /

image/Makefile

@@ -5,6 +5,7 @@ BOOTSTRAPPER_BINARY              ?= $(BASE_PATH)/../build/bootstrapper
 DISK_MAPPER_BINARY               ?= $(BASE_PATH)/../build/disk-mapper
 UPGRADE_AGENT_BINARY             ?= $(BASE_PATH)/../build/upgrade-agent
 DEBUGD_BINARY                    ?= $(BASE_PATH)/../build/debugd
+MEASUREMENT_READER_BINARY        ?= $(BASE_PATH)/../build/measurement-reader
 PKI                              ?= $(BASE_PATH)/pki
 MKOSI_EXTRA                      ?= $(BASE_PATH)/mkosi.extra
 IMAGE_VERSION                    ?= v0.0.0
@@ -65,9 +66,11 @@ inject-bins: $(PREBUILD_RPMS_SYSTEMD) $(PREBUILT_RPMS_AZURE) $(PREBUILT_RPMS_GCP
 	mkdir -p $(MKOSI_EXTRA)/usr/sbin
 	cp $(UPGRADE_AGENT_BINARY) $(MKOSI_EXTRA)/usr/bin/upgrade-agent
 	cp $(DISK_MAPPER_BINARY) $(MKOSI_EXTRA)/usr/sbin/disk-mapper
+	cp $(MEASUREMENT_READER_BINARY) $(MKOSI_EXTRA)/usr/sbin/measurement-reader
 	if [ "$(DEBUG)" = "true" ]; then \
 		cp $(DEBUGD_BINARY) $(MKOSI_EXTRA)/usr/bin/debugd; \
 		rm -f $(MKOSI_EXTRA)/usr/bin/bootstrapper; \
+		rm -f $(MKOSI_EXTRA)/usr/bin/upgrade-agent; \
 	else \
 		cp $(BOOTSTRAPPER_BINARY) $(MKOSI_EXTRA)/usr/bin/bootstrapper; \
 		rm -f $(MKOSI_EXTRA)/usr/bin/debugd; \

image/mkosi.conf.d/secure-boot-tpm.conf

@@ -5,4 +5,3 @@ Packages=
            sbsigntools,
            efitools,
            mokutil,
-           tpm2-tools,

image/mkosi.skeleton/usr/lib/systemd/system-preset/30-constellation.preset

@@ -4,5 +4,5 @@ enable constellation-bootstrapper.service
 enable containerd.service
 enable kubelet.service
 enable systemd-networkd.service
-enable tpm-pcrs.service
+enable measurements.service
 enable export_constellation_debug.service

image/mkosi.skeleton/usr/lib/systemd/system/measurements.service

@@ -1,10 +1,11 @@
 [Unit]
-Description=Print PCR state on startup
+Description=Print image measurements on startup
 Before=constellation-bootstrapper.service
 
 [Service]
 Type=oneshot
 RemainAfterExit=yes
+EnvironmentFile=/run/constellation.env
 ExecStart=/usr/libexec/constellation-pcrs
 
 [Install]

image/mkosi.skeleton/usr/libexec/constellation-pcrs

@@ -3,12 +3,12 @@
 #
 # SPDX-License-Identifier: AGPL-3.0-only
 
-# This script reads the PCR state of the system
+# This script reads the measurements of the system
 # and prints the message to the serial console
 
 main() {
-  pcr_state="$(tpm2_pcrread sha256)"
+  pcr_state="$(/usr/sbin/measurement-reader)"
-  echo -e "PCR state:\n${pcr_state}\n" > /run/issue.d/35_constellation_pcrs.issue
+  echo -e "${pcr_state}\n" > /run/issue.d/35_constellation_pcrs.issue
 }
 
 main

internal/oid/oid.go

@@ -25,7 +25,7 @@ package oid
 
 import (
 	"encoding/asn1"
-	"errors"
+	"fmt"
 )
 
 // Getter returns an ASN.1 Object Identifier.
@@ -49,7 +49,7 @@ func FromString(oid string) (Getter, error) {
 	case qemuVTPM:
 		return QEMUVTPM{}, nil
 	}
-	return nil, errors.New("unknown OID")
+	return nil, fmt.Errorf("unknown OID: %q", oid)
 }
 
 // Dummy OID for testing.

measurement-reader/cmd/main.go

@@ -0,0 +1,45 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/edgelesssys/constellation/v2/internal/constants"
+	"github.com/edgelesssys/constellation/v2/internal/logger"
+	"github.com/edgelesssys/constellation/v2/internal/oid"
+	"github.com/edgelesssys/constellation/v2/measurement-reader/internal/sorted"
+	"github.com/edgelesssys/constellation/v2/measurement-reader/internal/tpm"
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+func main() {
+	log := logger.New(logger.JSONLog, zapcore.InfoLevel)
+	variant := os.Getenv(constants.AttestationVariant)
+	attestationVariant, err := oid.FromString(variant)
+	if err != nil {
+		log.With(zap.Error(err)).Fatalf("Failed to parse attestation variant")
+	}
+
+	var m []sorted.Measurement
+	switch attestationVariant {
+	case oid.AWSNitroTPM{}, oid.AzureSEVSNP{}, oid.AzureTrustedLaunch{}, oid.GCPSEVES{}, oid.QEMUVTPM{}:
+		m, err = tpm.Measurements()
+		if err != nil {
+			log.With(zap.Error(err)).Fatalf("Failed to read TPM measurements")
+		}
+	default:
+		log.With(zap.String("attestationVariant", variant)).Fatalf("Unsupported attestation variant")
+	}
+
+	fmt.Println("Measurements:")
+	for _, measurement := range m {
+		fmt.Printf("\t%s : 0x%0X\n", measurement.Index, measurement.Value)
+	}
+}

measurement-reader/internal/sorted/sorted.go

@@ -0,0 +1,14 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+// Type definition for sorted measurements.
+package sorted
+
+// Measurement wraps a measurement custom index and value.
+type Measurement struct {
+	Index string
+	Value []byte
+}

measurement-reader/internal/tpm/tpm.go

@@ -0,0 +1,50 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+// Package tpm reads measurements from a TPM.
+package tpm
+
+import (
+	"fmt"
+	"sort"
+
+	"github.com/edgelesssys/constellation/v2/internal/attestation/measurements"
+	"github.com/edgelesssys/constellation/v2/internal/attestation/vtpm"
+	"github.com/edgelesssys/constellation/v2/measurement-reader/internal/sorted"
+	tpmClient "github.com/google/go-tpm-tools/client"
+	"github.com/google/go-tpm/tpm2"
+)
+
+// Measurements returns a sorted list of TPM PCR measurements.
+func Measurements() ([]sorted.Measurement, error) {
+	m, err := vtpm.GetSelectedMeasurements(vtpm.OpenVTPM, tpmClient.FullPcrSel(tpm2.AlgSHA256))
+	if err != nil {
+		return nil, err
+	}
+
+	return sortMeasurements(m), nil
+}
+
+func sortMeasurements(m measurements.M) []sorted.Measurement {
+	keys := make([]uint32, 0, len(m))
+	for idx := range m {
+		keys = append(keys, idx)
+	}
+	sort.Slice(keys, func(i, j int) bool {
+		return keys[i] < keys[j]
+	})
+
+	var measurements []sorted.Measurement
+	for _, idx := range keys {
+		expected := m[idx].Expected
+		measurements = append(measurements, sorted.Measurement{
+			Index: fmt.Sprintf("PCR[%02d]", idx),
+			Value: expected[:],
+		})
+	}
+
+	return measurements
+}

measurement-reader/internal/tpm/tpm_test.go

@@ -0,0 +1,78 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package tpm
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/edgelesssys/constellation/v2/internal/attestation/measurements"
+	"github.com/edgelesssys/constellation/v2/measurement-reader/internal/sorted"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSortMeasurements(t *testing.T) {
+	testCases := map[string]struct {
+		input measurements.M
+		want  []sorted.Measurement
+	}{
+		"pre sorted": {
+			input: measurements.M{
+				0: measurements.WithAllBytes(0x11, false),
+				1: measurements.WithAllBytes(0x22, false),
+				2: measurements.WithAllBytes(0x33, false),
+			},
+			want: []sorted.Measurement{
+				{
+					Index: "PCR[00]",
+					Value: bytes.Repeat([]byte{0x11}, 32),
+				},
+				{
+					Index: "PCR[01]",
+					Value: bytes.Repeat([]byte{0x22}, 32),
+				},
+				{
+					Index: "PCR[02]",
+					Value: bytes.Repeat([]byte{0x33}, 32),
+				},
+			},
+		},
+		"unsorted": {
+			input: measurements.M{
+				1: measurements.WithAllBytes(0x22, false),
+				0: measurements.WithAllBytes(0x11, false),
+				2: measurements.WithAllBytes(0x33, false),
+			},
+			want: []sorted.Measurement{
+				{
+					Index: "PCR[00]",
+					Value: bytes.Repeat([]byte{0x11}, 32),
+				},
+				{
+					Index: "PCR[01]",
+					Value: bytes.Repeat([]byte{0x22}, 32),
+				},
+				{
+					Index: "PCR[02]",
+					Value: bytes.Repeat([]byte{0x33}, 32),
+				},
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			got := sortMeasurements(tc.input)
+			for i := range got {
+				assert.Equal(got[i].Index, tc.want[i].Index)
+				assert.Equal(got[i].Value, tc.want[i].Value)
+			}
+		})
+	}
+}