AB#1770 (semi)automatic PCR updates (#7)

Signed-off-by: Daniel Weiße <dw@edgeless.systems>
2025-01-22 21:31:14 -05:00 · 2022-03-23 14:10:58 +01:00 · 2022-03-23 14:10:58 +01:00 · 1f843d4593
commit 1f843d4593
parent 752571bbf8
5 changed files with 544 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@ -18,6 +18,7 @@ build
 admin.conf
 coordinatorConfig.json
 coordinator-*
+util/pcr-reader/pcrs/

 # VS Code configuration folder
 .vscode
--- a/util/pcr-reader/README.md
+++ b/util/pcr-reader/README.md
@ -0,0 +1,89 @@
+# PCR-updater
+
+New images result in different PCR values for the image.
+This utility program makes it simple to update the expected PCR values of the CLI.
+
+## Usage
+
+### Script
+
+Run `fetch_pcrs.sh` to create Constellations on all supported cloud providers and read their PCR states.
+```shell
+./fetch_pcrs.sh
+```
+
+The result is printed to screen and written as Go code to files in `./pcrs`.
+```bash
+ main
+ command -v constellation
+ command -v go
+ mkdir -p ./pcrs
+ constellation create azure 2 Standard_D4s_v3 --name pcr-fetch -y
+Your Constellation was created successfully.
++ jq '.azurecoordinators | to_entries[] | select(.key|startswith("")) | .value.PublicIP' -rcM constellation-state.json
+ coord_ip=192.0.2.1
+ go run ../main.go -coord-ip 192.0.2.1 -o ./pcrs/azure_pcrs.go
+connecting to Coordinator at 192.0.2.1:9000
+PCRs:
+{
+  "0": "q27iAZeXGAiCPdu1bqRA2gAoyMO2KrXWY4YkTCQowc4=",
+  ...
+  "9": "dEGJtQe3h+SI0z42yO7TklzwPixtM3iMCUeJPGRozvg="
+}
+ constellation terminate
+Your Constellation was terminated successfully.
+ constellation create gcp 2 n2d-standard-2 --name pcr-fetch -y
+Your Constellation was created successfully.
++ jq '.gcpcoordinators | to_entries[] | select(.key|startswith("")) | .value.PublicIP' -rcM constellation-state.json
+ coord_ip=192.0.2.2
+ go run ../main.go -coord-ip 192.0.2.2 -o ./pcrs/gcp_pcrs.go
+connecting to Coordinator at 192.0.2.2:9000
+PCRs:
+{
+  "0": "DzXCFGCNk8em5ornNZtKi+Wg6Z7qkQfs5CfE3qTkOc8=",
+  ...
+  "9": "gse53SjsqREEdOpImJH4KAb0b8PqIgwI+Ps/XSiFnN4="
+}
+ constellation terminate
+Your Constellation was terminated successfully.
+```
+
+### Manual
+
+To read the PCR state of any running Constellation node, run the following:
+```shell
+go run main.go -coord-ip <NODE_IP> -coord-port <COORDINATOR_PORT>
+```
+
+The output is similar to the following:
+```shell
+$ go run main.go -coord-ip 192.0.2.3 -coord-port 12345
+connecting to Coordinator at 192.0.2.3:12345
+PCRs:
+{
+  "0": "DzXCFGCNk8em5ornNZtKi+Wg6Z7qkQfs5CfE3qTkOc8=",
+  "1": "XBoRlWuQx6nIDr5vgUL0DlJHy6H6u1dPU3qK2NyToc8=",
+  "10": "WLmYFRmDft/ajZJ056CAhpheU6Vbt73aR8eIQpLRGq0=",
+  "11": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+  "12": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+  "13": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+  "14": "4tPyJd6A5g09KduV3+nWZQCiEzHAiRT5DulmAqlvpZU=",
+  "15": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+  "16": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+  "17": "//////////////////////////////////////////8=",
+  "18": "//////////////////////////////////////////8=",
+  "19": "//////////////////////////////////////////8=",
+  "2": "PUWM/lXMA+ofRD8VYr7sjfUcdeFKn8+acjShPxmOeWk=",
+  "20": "//////////////////////////////////////////8=",
+  "21": "//////////////////////////////////////////8=",
+  "22": "//////////////////////////////////////////8=",
+  "23": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+  "3": "PUWM/lXMA+ofRD8VYr7sjfUcdeFKn8+acjShPxmOeWk=",
+  "4": "MmkueFj1rP2seH+bjeIRsO4dUnLnMdl7QgtGoAtQH7M=",
+  "5": "ExaiapuIfo0KMBo8wj6kPDORLocgnH1C0G/KY8DcV3A=",
+  "6": "PUWM/lXMA+ofRD8VYr7sjfUcdeFKn8+acjShPxmOeWk=",
+  "7": "UZcW+fhFRMpFkgU+EfKG2s3KdmgEA+TD2quLmthQHbo=",
+  "8": "KLSMootYaHBjysWKq9CAYXkXpeYx9PUBimlSEZGJqUM=",
+  "9": "gse53SjsqREEdOpImJH4KAb0b8PqIgwI+Ps/XSiFnN4="
+}
+```
--- a/util/pcr-reader/fetch_pcrs.sh
+++ b/util/pcr-reader/fetch_pcrs.sh
@ -0,0 +1,41 @@
+#!/bin/bash
+
+set -o xtrace
+trap 'terminate $?' ERR
+
+terminate() {
+    echo "error: $1"
+    constellation terminate
+    popd || exit 1
+    exit 1
+}
+
+main() {
+    if ! command -v constellation &> /dev/null
+    then
+        echo "constellation is not in path"
+        exit 1
+    fi
+    if ! command -v go &> /dev/null
+    then
+        echo "go is not in path"
+        exit 1
+    fi
+
+    mkdir -p ./pcrs
+
+    # Fetch Azure PCRs
+    # TODO: Switch to confidential VMs
+    constellation create azure 2 Standard_D4s_v3 --name pcr-fetch -y
+    coord_ip=$(jq '.azurecoordinators | to_entries[] | select(.key|startswith("")) | .value.PublicIP' -rcM constellation-state.json)
+    go run main.go -coord-ip "${coord_ip}" -o ./pcrs/azure_pcrs.go
+    constellation terminate
+
+    # Fetch GCP PCRs
+    constellation create gcp 2 n2d-standard-2 --name pcr-fetch -y
+    coord_ip=$(jq '.gcpcoordinators | to_entries[] | select(.key|startswith("")) | .value.PublicIP' -rcM constellation-state.json)
+    go run main.go -coord-ip "${coord_ip}" -o ./pcrs/gcp_pcrs.go
+    constellation terminate
+}
+
+main
--- a/util/pcr-reader/main.go
+++ b/util/pcr-reader/main.go
@ -0,0 +1,167 @@
+package main
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"os"
+	"time"
+
+	"github.com/edgelesssys/constellation/cli/status"
+	"github.com/edgelesssys/constellation/coordinator/atls"
+	"github.com/edgelesssys/constellation/coordinator/attestation/vtpm"
+	"github.com/edgelesssys/constellation/coordinator/oid"
+	"github.com/edgelesssys/constellation/coordinator/pubapi/pubproto"
+	coordinatorstate "github.com/edgelesssys/constellation/coordinator/state"
+	"github.com/spf13/afero"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+)
+
+var (
+	coordIP         = flag.String("coord-ip", "", "IP of the VM the Coordinator is running on")
+	coordinatorPort = flag.String("coord-port", "9000", "Port of the Coordinator's pub API")
+	export          = flag.String("o", "", "Write PCRs, formatted as Go code, to file")
+	quiet           = flag.Bool("q", false, "Set to disable output")
+)
+
+func main() {
+	flag.Parse()
+
+	fmt.Printf("connecting to Coordinator at %s:%s\n", *coordIP, *coordinatorPort)
+	addr := net.JoinHostPort(*coordIP, *coordinatorPort)
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	// wait for coordinator to come online
+	waiter := status.NewWaiter(map[uint32][]byte{})
+	if err := waiter.WaitFor(ctx, coordinatorstate.AcceptingInit, addr); err != nil {
+		log.Fatal(err)
+	}
+
+	attDocRaw := &[]byte{}
+	tlsConfig, err := atls.CreateUnverifiedClientTLSConfig()
+	if err != nil {
+		log.Fatal(err)
+	}
+	tlsConfig.VerifyPeerCertificate = getVerifyPeerCertificateFunc(attDocRaw)
+	if err := connectToCoordinator(ctx, addr, tlsConfig); err != nil {
+		log.Fatal(err)
+	}
+
+	pcrs, err := validatePCRAttDoc(*attDocRaw)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if !*quiet {
+		if err := printPCRs(os.Stdout, pcrs); err != nil {
+			log.Fatal(err)
+		}
+	}
+	if *export != "" {
+		if err := exportToFile(*export, pcrs, &afero.Afero{Fs: afero.NewOsFs()}); err != nil {
+			log.Fatal(err)
+		}
+	}
+}
+
+// connectToCoordinator connects to the Constellation Coordinator and returns its attestation document.
+func connectToCoordinator(ctx context.Context, addr string, tlsConfig *tls.Config) error {
+	conn, err := grpc.DialContext(
+		ctx, addr, grpc.WithTransportCredentials(credentials.NewTLS(tlsConfig)),
+	)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	client := pubproto.NewAPIClient(conn)
+	_, err = client.GetState(ctx, &pubproto.GetStateRequest{})
+	return err
+}
+
+// getVerifyPeerCertificateFunc returns a VerifyPeerCertificate function, which writes the attestation document extension to the given byte slice pointer.
+func getVerifyPeerCertificateFunc(attDoc *[]byte) func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
+	return func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
+		if len(rawCerts) == 0 {
+			return errors.New("rawCerts is empty")
+		}
+		cert, err := x509.ParseCertificate(rawCerts[0])
+		if err != nil {
+			return err
+		}
+
+		for _, ex := range cert.Extensions {
+			if ex.Id.Equal(oid.Azure{}.OID()) || ex.Id.Equal(oid.GCP{}.OID()) || ex.Id.Equal(oid.GCPNonCVM{}.OID()) {
+				if err := json.Unmarshal(ex.Value, attDoc); err != nil {
+					*attDoc = ex.Value
+				}
+			}
+		}
+
+		if len(*attDoc) == 0 {
+			return errors.New("did not receive attestation document in certificate extension")
+		}
+		return nil
+	}
+}
+
+// validatePCRAttDoc parses and validates PCRs of an attestation document.
+func validatePCRAttDoc(attDocRaw []byte) (map[uint32][]byte, error) {
+	attDoc := vtpm.AttestationDocument{}
+	if err := json.Unmarshal(attDocRaw, &attDoc); err != nil {
+		return nil, err
+	}
+	if attDoc.Attestation == nil {
+		return nil, errors.New("empty attestation")
+	}
+	qIdx, err := vtpm.GetSHA256QuoteIndex(attDoc.Attestation.Quotes)
+	if err != nil {
+		return nil, err
+	}
+	for idx, pcr := range attDoc.Attestation.Quotes[qIdx].Pcrs.Pcrs {
+		if len(pcr) != 32 {
+			return nil, fmt.Errorf("incomplete PCR at index: %d", idx)
+		}
+	}
+	return attDoc.Attestation.Quotes[qIdx].Pcrs.Pcrs, nil
+}
+
+// printPCRs formates and prints PCRs to the given writer.
+func printPCRs(w io.Writer, pcrs map[uint32][]byte) error {
+	pcrJSON, err := json.MarshalIndent(pcrs, "", "  ")
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(w, "PCRs:\n%s\n", string(pcrJSON))
+	return nil
+}
+
+// exportToFile writes pcrs to a file, formatted to be valid Go code.
+// Validity of the PCR map is not checked, and should be handled by the caller.
+func exportToFile(path string, pcrs map[uint32][]byte, fs *afero.Afero) error {
+	goCode := `package pcrs
+
+var pcrs = map[uint32][]byte{%s
+}
+`
+	pcrsFormatted := ""
+	for i := 0; i < len(pcrs); i++ {
+		pcrHex := fmt.Sprintf("%#02X", pcrs[uint32(i)][0])
+		for j := 1; j < len(pcrs[uint32(i)]); j++ {
+			pcrHex = fmt.Sprintf("%s, %#02X", pcrHex, pcrs[uint32(i)][j])
+		}
+
+		pcrsFormatted = pcrsFormatted + fmt.Sprintf("\n\t%d: {%s},", i, pcrHex)
+	}
+
+	return fs.WriteFile(path, []byte(fmt.Sprintf(goCode, pcrsFormatted)), 0o644)
+}
--- a/util/pcr-reader/main_test.go
+++ b/util/pcr-reader/main_test.go
@ -0,0 +1,246 @@
+package main
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"math/big"
+	"testing"
+
+	"github.com/edgelesssys/constellation/coordinator/attestation/vtpm"
+	"github.com/edgelesssys/constellation/coordinator/oid"
+	"github.com/google/go-tpm-tools/proto/attest"
+	"github.com/google/go-tpm-tools/proto/tpm"
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetVerifyPeerCertificateFunc(t *testing.T) {
+	testCases := map[string]struct {
+		rawCerts    [][]byte
+		errExpected bool
+	}{
+		"no certificates": {
+			rawCerts:    nil,
+			errExpected: true,
+		},
+		"invalid certificate": {
+			rawCerts: [][]byte{
+				{0x1, 0x2, 0x3},
+			},
+			errExpected: true,
+		},
+		"no extension": {
+			rawCerts: [][]byte{
+				mustGenerateTestCert(t, &x509.Certificate{
+					SerialNumber: big.NewInt(123),
+				}),
+			},
+			errExpected: true,
+		},
+		"certificate with attestation": {
+			rawCerts: [][]byte{
+				mustGenerateTestCert(t, &x509.Certificate{
+					SerialNumber: big.NewInt(123),
+					ExtraExtensions: []pkix.Extension{
+						{
+							Id:       oid.GCP{}.OID(),
+							Value:    []byte{0x1, 0x2, 0x3},
+							Critical: true,
+						},
+					},
+				}),
+			},
+			errExpected: false,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			attDoc := &[]byte{}
+			verify := getVerifyPeerCertificateFunc(attDoc)
+
+			err := verify(tc.rawCerts, nil)
+			if tc.errExpected {
+				assert.Error(err)
+			} else {
+				require.NoError(err)
+
+				assert.NotNil(attDoc)
+				cert, err := x509.ParseCertificate(tc.rawCerts[0])
+				require.NoError(err)
+				assert.Equal(cert.Extensions[0].Value, *attDoc)
+			}
+		})
+	}
+}
+
+func mustGenerateTestCert(t *testing.T, template *x509.Certificate) []byte {
+	require := require.New(t)
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	require.NoError(err)
+	cert, err := x509.CreateCertificate(rand.Reader, template, template, priv.Public(), priv)
+	require.NoError(err)
+	return cert
+}
+
+func TestExportToFile(t *testing.T) {
+	testCases := map[string]struct {
+		pcrs        map[uint32][]byte
+		fs          *afero.Afero
+		errExpected bool
+	}{
+		"file not writeable": {
+			pcrs: map[uint32][]byte{
+				0: {0x1, 0x2, 0x3},
+				1: {0x1, 0x2, 0x3},
+				2: {0x1, 0x2, 0x3},
+			},
+			fs:          &afero.Afero{Fs: afero.NewReadOnlyFs(afero.NewMemMapFs())},
+			errExpected: true,
+		},
+		"file writeable": {
+			pcrs: map[uint32][]byte{
+				0: {0x1, 0x2, 0x3},
+				1: {0x1, 0x2, 0x3},
+				2: {0x1, 0x2, 0x3},
+			},
+			fs:          &afero.Afero{Fs: afero.NewMemMapFs()},
+			errExpected: false,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			path := "test-file"
+			err := exportToFile(path, tc.pcrs, tc.fs)
+			if tc.errExpected {
+				assert.Error(err)
+			} else {
+				assert.NoError(err)
+				content, err := tc.fs.ReadFile(path)
+				require.NoError(err)
+
+				for _, pcr := range tc.pcrs {
+					for _, register := range pcr {
+						assert.Contains(string(content), fmt.Sprintf("%#02X", register))
+					}
+				}
+			}
+		})
+	}
+}
+
+func TestValidatePCRAttDoc(t *testing.T) {
+	testCases := map[string]struct {
+		attDocRaw   []byte
+		errExpected bool
+	}{
+		"invalid attestation document": {
+			attDocRaw:   []byte{0x1, 0x2, 0x3},
+			errExpected: true,
+		},
+		"nil attestation": {
+			attDocRaw:   mustMarshalAttDoc(t, vtpm.AttestationDocument{}),
+			errExpected: true,
+		},
+		"nil quotes": {
+			attDocRaw: mustMarshalAttDoc(t, vtpm.AttestationDocument{
+				Attestation: &attest.Attestation{},
+			}),
+			errExpected: true,
+		},
+		"invalid PCRs": {
+			attDocRaw: mustMarshalAttDoc(t, vtpm.AttestationDocument{
+				Attestation: &attest.Attestation{
+					Quotes: []*tpm.Quote{
+						{
+							Pcrs: &tpm.PCRs{
+								Hash: tpm.HashAlgo_SHA256,
+								Pcrs: map[uint32][]byte{
+									0: {0x1, 0x2, 0x3},
+								},
+							},
+						},
+					},
+				},
+			}),
+			errExpected: true,
+		},
+		"valid PCRs": {
+			attDocRaw: mustMarshalAttDoc(t, vtpm.AttestationDocument{
+				Attestation: &attest.Attestation{
+					Quotes: []*tpm.Quote{
+						{
+							Pcrs: &tpm.PCRs{
+								Hash: tpm.HashAlgo_SHA256,
+								Pcrs: map[uint32][]byte{
+									0: []byte("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"),
+								},
+							},
+						},
+					},
+				},
+			}),
+			errExpected: false,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			pcrs, err := validatePCRAttDoc(tc.attDocRaw)
+			if tc.errExpected {
+				assert.Error(err)
+			} else {
+				require.NoError(err)
+
+				attDoc := vtpm.AttestationDocument{}
+				require.NoError(json.Unmarshal(tc.attDocRaw, &attDoc))
+				qIdx, err := vtpm.GetSHA256QuoteIndex(attDoc.Attestation.Quotes)
+				require.NoError(err)
+				assert.EqualValues(attDoc.Attestation.Quotes[qIdx].Pcrs.Pcrs, pcrs)
+			}
+		})
+	}
+}
+
+func mustMarshalAttDoc(t *testing.T, attDoc vtpm.AttestationDocument) []byte {
+	attDocRaw, err := json.Marshal(attDoc)
+	require.NoError(t, err)
+	return attDocRaw
+}
+
+func TestPrintPCRs(t *testing.T) {
+	assert := assert.New(t)
+
+	pcrs := map[uint32][]byte{
+		0: {0x1, 0x2, 0x3},
+		1: {0x1, 0x2, 0x3},
+		2: {0x1, 0x2, 0x3},
+	}
+
+	var out bytes.Buffer
+	err := printPCRs(&out, pcrs)
+	assert.NoError(err)
+
+	for idx, pcr := range pcrs {
+		assert.Contains(out.String(), fmt.Sprintf("\"%d\": ", idx))
+		assert.Contains(out.String(), fmt.Sprintf(": \"%s\"", base64.StdEncoding.EncodeToString(pcr)))
+	}
+}