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cli: print attestation document with constellation verify (#1577)

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* wip: verification output

* wip: Azure cert parsing

* wip: print actual PCRs

* wip: use string builder for output formatting

* compare PCR expected with actual

* tests

* change naming

* update cli reference

* update bazel buildfile

* bazel update

* change loop signature
This commit is contained in:
Moritz Sanft 2023-04-03 15:06:27 +02:00 • committed by GitHub
parent d15968bed7
commit e71c33c88d
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 336 additions and 41 deletions
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227
cli/internal/cmd/verify.go
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@ -9,6 +9,10 @@ package cmd
import (
"bytes"
"context"
"crypto/x509"
"encoding/base64"
"encoding/json"
"encoding/pem"
"errors"
"fmt"
"net"
@ -18,6 +22,7 @@ import (
"github.com/edgelesssys/constellation/v2/cli/internal/cloudcmd"
"github.com/edgelesssys/constellation/v2/cli/internal/clusterid"
"github.com/edgelesssys/constellation/v2/internal/atls"
"github.com/edgelesssys/constellation/v2/internal/attestation/measurements"
"github.com/edgelesssys/constellation/v2/internal/config"
"github.com/edgelesssys/constellation/v2/internal/constants"
"github.com/edgelesssys/constellation/v2/internal/crypto"
@ -34,13 +39,13 @@ func NewVerifyCmd() *cobra.Command {
cmd := &cobra.Command{
Use: "verify",
Short: "Verify the confidential properties of a Constellation cluster",
Long: `Verify the confidential properties of a Constellation cluster.
If arguments aren't specified, values are read from ` + "`" + constants.ClusterIDsFileName + "`.",
Long: `Verify the confidential properties of a Constellation cluster.\n` +
`If arguments aren't specified, values are read from ` + "`" + constants.ClusterIDsFileName + "`.",
Args: cobra.ExactArgs(0),
RunE: runVerify,
}
cmd.Flags().String("cluster-id", "", "expected cluster identifier")
cmd.Flags().Bool("raw", false, "print raw attestation document")
cmd.Flags().StringP("node-endpoint", "e", "", "endpoint of the node to verify, passed as HOST[:PORT]")
return cmd
}
@ -61,85 +66,102 @@ func runVerify(cmd *cobra.Command, _ []string) error {
dialer: dialer.New(nil, nil, &net.Dialer{}),
log: log,
}
formatter := &attestationDocFormatterImpl{
log: log,
}
v := &verifyCmd{log: log}
return v.verify(cmd, fileHandler, verifyClient)
return v.verify(cmd, fileHandler, verifyClient, formatter)
}
func (v *verifyCmd) verify(cmd *cobra.Command, fileHandler file.Handler, verifyClient verifyClient) error {
flags, err := v.parseVerifyFlags(cmd, fileHandler)
func (c *verifyCmd) verify(cmd *cobra.Command, fileHandler file.Handler, verifyClient verifyClient, formatter attestationDocFormatter) error {
flags, err := c.parseVerifyFlags(cmd, fileHandler)
if err != nil {
return err
return fmt.Errorf("parsing flags: %w", err)
}
v.log.Debugf("Using flags: %+v", flags)
c.log.Debugf("Using flags: %+v", flags)
v.log.Debugf("Loading configuration file from %q", flags.configPath)
c.log.Debugf("Loading configuration file from %q", flags.configPath)
conf, err := config.New(fileHandler, flags.configPath, flags.force)
var configValidationErr *config.ValidationError
if errors.As(err, &configValidationErr) {
cmd.PrintErrln(configValidationErr.LongMessage())
}
if err != nil {
return err
return fmt.Errorf("loading config file: %w", err)
}
v.log.Debugf("Creating aTLS Validator for %s", conf.AttestationVariant)
validators, err := cloudcmd.NewValidator(conf, flags.maaURL, v.log)
c.log.Debugf("Creating aTLS Validator for %s", conf.AttestationVariant)
validators, err := cloudcmd.NewValidator(conf, flags.maaURL, c.log)
if err != nil {
return err
return fmt.Errorf("creating aTLS validator: %w", err)
}
v.log.Debugf("Updating expected PCRs")
c.log.Debugf("Updating expected PCRs")
if err := validators.UpdateInitPCRs(flags.ownerID, flags.clusterID); err != nil {
return err
return fmt.Errorf("updating expected PCRs: %w", err)
}
nonce, err := crypto.GenerateRandomBytes(32)
if err != nil {
return err
return fmt.Errorf("generating random nonce: %w", err)
}
v.log.Debugf("Generated random nonce: %x", nonce)
c.log.Debugf("Generated random nonce: %x", nonce)
if err := verifyClient.Verify(
rawAttestationDoc, err := verifyClient.Verify(
cmd.Context(),
flags.endpoint,
&verifyproto.GetAttestationRequest{
Nonce: nonce,
},
validators.V(cmd),
); err != nil {
return err
)
if err != nil {
return fmt.Errorf("verifying: %w", err)
}
cmd.Println("OK")
// certificates are only available for Azure
attDocOutput, err := formatter.format(rawAttestationDoc, conf.Provider.Azure == nil, flags.rawOutput, validators.PCRS())
if err != nil {
return fmt.Errorf("printing attestation document: %w", err)
}
cmd.Println(attDocOutput)
cmd.Println("Verification OK")
return nil
}
func (v *verifyCmd) parseVerifyFlags(cmd *cobra.Command, fileHandler file.Handler) (verifyFlags, error) {
func (c *verifyCmd) parseVerifyFlags(cmd *cobra.Command, fileHandler file.Handler) (verifyFlags, error) {
configPath, err := cmd.Flags().GetString("config")
if err != nil {
return verifyFlags{}, fmt.Errorf("parsing config path argument: %w", err)
}
v.log.Debugf("Flag 'config' set to %q", configPath)
c.log.Debugf("Flag 'config' set to %q", configPath)
ownerID := ""
clusterID, err := cmd.Flags().GetString("cluster-id")
if err != nil {
return verifyFlags{}, fmt.Errorf("parsing cluster-id argument: %w", err)
}
v.log.Debugf("Flag 'cluster-id' set to %q", clusterID)
c.log.Debugf("Flag 'cluster-id' set to %q", clusterID)
endpoint, err := cmd.Flags().GetString("node-endpoint")
if err != nil {
return verifyFlags{}, fmt.Errorf("parsing node-endpoint argument: %w", err)
}
v.log.Debugf("Flag 'node-endpoint' set to %q", endpoint)
c.log.Debugf("Flag 'node-endpoint' set to %q", endpoint)
force, err := cmd.Flags().GetBool("force")
if err != nil {
return verifyFlags{}, fmt.Errorf("parsing force argument: %w", err)
}
v.log.Debugf("Flag 'force' set to %t", force)
c.log.Debugf("Flag 'force' set to %t", force)
raw, err := cmd.Flags().GetBool("raw")
if err != nil {
return verifyFlags{}, fmt.Errorf("parsing raw argument: %w", err)
}
c.log.Debugf("Flag 'raw' set to %t", force)
var idFile clusterid.File
if err := fileHandler.ReadJSON(constants.ClusterIDsFileName, &idFile); err != nil && !errors.Is(err, afero.ErrFileNotFound) {
@ -150,7 +172,7 @@ func (v *verifyCmd) parseVerifyFlags(cmd *cobra.Command, fileHandler file.Handle
emptyEndpoint := endpoint == ""
emptyIDs := ownerID == "" && clusterID == ""
if emptyEndpoint || emptyIDs {
v.log.Debugf("Trying to supplement empty flag values from %q", constants.ClusterIDsFileName)
c.log.Debugf("Trying to supplement empty flag values from %q", constants.ClusterIDsFileName)
if emptyEndpoint {
cmd.Printf("Using endpoint from %q. Specify --node-endpoint to override this.\n", constants.ClusterIDsFileName)
endpoint = idFile.IP
@ -177,6 +199,7 @@ func (v *verifyCmd) parseVerifyFlags(cmd *cobra.Command, fileHandler file.Handle
ownerID: ownerID,
clusterID: clusterID,
maaURL: idFile.AttestationURL,
rawOutput: raw,
force: force,
}, nil
}
@ -187,6 +210,7 @@ type verifyFlags struct {
clusterID string
configPath string
maaURL string
rawOutput bool
force bool
}
@ -207,6 +231,140 @@ func addPortIfMissing(endpoint string, defaultPort int) (string, error) {
return "", err
}
// an attestationDocFormatter formats the attestation document.
type attestationDocFormatter interface {
// format returns the raw or formatted attestation doc depending on the rawOutput argument.
format(docString string, PCRsOnly bool, rawOutput bool, expectedPCRs measurements.M) (string, error)
}
type attestationDocFormatterImpl struct {
log debugLog
}
// format returns the raw or formatted attestation doc depending on the rawOutput argument.
func (f *attestationDocFormatterImpl) format(docString string, PCRsOnly bool, rawOutput bool, expectedPCRs measurements.M) (string, error) {
b := &strings.Builder{}
b.WriteString("Attestation Document:\n")
if rawOutput {
b.WriteString(fmt.Sprintf("%s\n", docString))
return b.String(), nil
}
var doc attestationDoc
if err := json.Unmarshal([]byte(docString), &doc); err != nil {
return "", fmt.Errorf("unmarshal attestation document: %w", err)
}
if err := f.parseQuotes(b, doc.Attestation.Quotes, expectedPCRs); err != nil {
return "", fmt.Errorf("parse quote: %w", err)
}
if PCRsOnly {
return b.String(), nil
}
instanceInfoString, err := base64.StdEncoding.DecodeString(doc.InstanceInfo)
if err != nil {
return "", fmt.Errorf("decode instance info: %w", err)
}
var instanceInfo azureInstanceInfo
if err := json.Unmarshal(instanceInfoString, &instanceInfo); err != nil {
return "", fmt.Errorf("unmarshal instance info: %w", err)
}
if err := f.parseCerts(b, "VCEK certificate", instanceInfo.Vcek); err != nil {
return "", fmt.Errorf("print VCEK certificate: %w", err)
}
if err := f.parseCerts(b, "Certificate chain", instanceInfo.CertChain); err != nil {
return "", fmt.Errorf("print certificate chain: %w", err)
}
return b.String(), nil
}
// parseCerts parses the base64-encoded PEM certificates and writes their details to the output builder.
func (f *attestationDocFormatterImpl) parseCerts(b *strings.Builder, certTypeName string, encCertString string) error {
certBytes, err := base64.StdEncoding.DecodeString(encCertString)
if err != nil {
return fmt.Errorf("decode %s: %w", certTypeName, err)
}
formattedCert := strings.ReplaceAll(string(certBytes[:len(certBytes)-1]), "\n", "\n\t\t") + "\n"
b.WriteString(fmt.Sprintf("\tRaw %s:\n\t\t%s", certTypeName, formattedCert))
f.log.Debugf("Decoding PEM certificate: %s", certTypeName)
i := 1
for block, rest := pem.Decode(certBytes); block != nil; block, rest = pem.Decode(rest) {
f.log.Debugf("Parsing PEM block: %d", i)
if block.Type != "CERTIFICATE" {
return fmt.Errorf("parse %s: expected PEM block type 'CERTIFICATE', got '%s'", certTypeName, block.Type)
}
cert, err := x509.ParseCertificate(block.Bytes)
if err != nil {
return fmt.Errorf("parse %s: %w", certTypeName, err)
}
b.WriteString(fmt.Sprintf("\t%s (%d):\n", certTypeName, i))
b.WriteString(fmt.Sprintf("\t\tSerial Number: %s\n", cert.SerialNumber))
b.WriteString(fmt.Sprintf("\t\tSubject: %s\n", cert.Subject))
b.WriteString(fmt.Sprintf("\t\tIssuer: %s\n", cert.Issuer))
b.WriteString(fmt.Sprintf("\t\tNot Before: %s\n", cert.NotBefore))
b.WriteString(fmt.Sprintf("\t\tNot After: %s\n", cert.NotAfter))
b.WriteString(fmt.Sprintf("\t\tSignature Algorithm: %s\n", cert.SignatureAlgorithm))
b.WriteString(fmt.Sprintf("\t\tPublic Key Algorithm: %s\n", cert.PublicKeyAlgorithm))
i++
}
return nil
}
// parseQuotes parses the base64-encoded quotes and writes their details to the output builder.
func (f *attestationDocFormatterImpl) parseQuotes(b *strings.Builder, quotes []quote, expectedPCRs measurements.M) error {
b.WriteString("\tQuote:\n")
for pcrNum, expectedPCR := range expectedPCRs {
encPCR := quotes[1].Pcrs.Pcrs[fmt.Sprintf("%d", pcrNum)]
actualPCR, err := base64.StdEncoding.DecodeString(encPCR)
if err != nil {
return fmt.Errorf("decode PCR %d: %w", pcrNum, err)
}
b.WriteString(fmt.Sprintf("\t\tPCR %d (Strict: %t):\n", pcrNum, !expectedPCR.ValidationOpt))
b.WriteString(fmt.Sprintf("\t\t\tExpected:\t%x\n", expectedPCR.Expected))
b.WriteString(fmt.Sprintf("\t\t\tActual:\t\t%x\n", actualPCR))
}
return nil
}
// attestationDoc is the attestation document returned by the verifier.
type attestationDoc struct {
Attestation struct {
AkPub string `json:"ak_pub"`
Quotes []quote `json:"quotes"`
EventLog string `json:"event_log"`
TeeAttestation interface{} `json:"TeeAttestation"`
} `json:"Attestation"`
InstanceInfo string `json:"InstanceInfo"`
UserData string `json:"UserData"`
}
type quote struct {
Quote string `json:"quote"`
RawSig string `json:"raw_sig"`
Pcrs struct {
Hash int `json:"hash"`
Pcrs map[string]string `json:"pcrs"`
} `json:"pcrs"`
}
// azureInstanceInfo is the b64-decoded InstanceInfo field of the attestation document.
// as of now (2023-04-03), it only contains interesting data on Azure.
type azureInstanceInfo struct {
Vcek string `json:"Vcek"`
CertChain string `json:"CertChain"`
AttestationReport string `json:"AttestationReport"`
RuntimeData string `json:"RuntimeData"`
}
type constellationVerifier struct {
dialer grpcInsecureDialer
log debugLog
@ -215,11 +373,11 @@ type constellationVerifier struct {
// Verify retrieves an attestation statement from the Constellation and verifies it using the validator.
func (v *constellationVerifier) Verify(
ctx context.Context, endpoint string, req *verifyproto.GetAttestationRequest, validator atls.Validator,
) error {
) (string, error) {
v.log.Debugf("Dialing endpoint: %q", endpoint)
conn, err := v.dialer.DialInsecure(ctx, endpoint)
if err != nil {
return fmt.Errorf("dialing init server: %w", err)
return "", fmt.Errorf("dialing init server: %w", err)
}
defer conn.Close()
@ -228,23 +386,24 @@ func (v *constellationVerifier) Verify(
v.log.Debugf("Sending attestation request")
resp, err := client.GetAttestation(ctx, req)
if err != nil {
return fmt.Errorf("getting attestation: %w", err)
return "", fmt.Errorf("getting attestation: %w", err)
}
v.log.Debugf("Verifying attestation")
signedData, err := validator.Validate(ctx, resp.Attestation, req.Nonce)
if err != nil {
return fmt.Errorf("validating attestation: %w", err)
return "", fmt.Errorf("validating attestation: %w", err)
}
if !bytes.Equal(signedData, []byte(constants.ConstellationVerifyServiceUserData)) {
return errors.New("signed data in attestation does not match expected user data")
return "", errors.New("signed data in attestation does not match expected user data")
}
return nil
return string(resp.Attestation), nil
}
type verifyClient interface {
Verify(ctx context.Context, endpoint string, req *verifyproto.GetAttestationRequest, validator atls.Validator) error
Verify(ctx context.Context, endpoint string, req *verifyproto.GetAttestationRequest, validator atls.Validator) (string, error)
}
type grpcInsecureDialer interface {