constellation/internal/attestation/azure/snp/issuer.go
Daniel Weiße dd2da25ebe attestation: tdx issuer/validator (#1265)
* Add TDX validator

* Add TDX issuer

---------

Signed-off-by: Daniel Weiße <dw@edgeless.systems>
2023-05-17 11:37:26 +02:00

101 lines
2.4 KiB
Go

/*
Copyright (c) Edgeless Systems GmbH
SPDX-License-Identifier: AGPL-3.0-only
*/
package snp
import (
"context"
"encoding/json"
"fmt"
"io"
"github.com/edgelesssys/constellation/v2/internal/attestation"
"github.com/edgelesssys/constellation/v2/internal/attestation/vtpm"
"github.com/edgelesssys/constellation/v2/internal/variant"
"github.com/edgelesssys/go-azguestattestation/maa"
tpmclient "github.com/google/go-tpm-tools/client"
)
const tpmAkIdx = 0x81000003
// Issuer for Azure TPM attestation.
type Issuer struct {
variant.AzureSEVSNP
*vtpm.Issuer
imds imdsAPI
maa maaTokenCreator
}
// NewIssuer initializes a new Azure Issuer.
func NewIssuer(log attestation.Logger) *Issuer {
i := &Issuer{
imds: newIMDSClient(),
maa: newMAAClient(),
}
i.Issuer = vtpm.NewIssuer(
vtpm.OpenVTPM,
getAttestationKey,
i.getInstanceInfo,
log,
)
return i
}
func (i *Issuer) getInstanceInfo(ctx context.Context, tpm io.ReadWriteCloser, userData []byte) ([]byte, error) {
params, err := i.maa.newParameters(ctx, userData, tpm)
if err != nil {
return nil, fmt.Errorf("getting system parameters: %w", err)
}
var maaToken string
maaURL, err := i.imds.getMAAURL(ctx)
if err != nil {
return nil, fmt.Errorf("retrieving MAA URL from IMDS API: %w", err)
}
if maaURL != "" {
maaToken, err = i.maa.createToken(ctx, tpm, maaURL, userData, params)
if err != nil {
return nil, fmt.Errorf("creating MAA token: %w", err)
}
}
instanceInfo := azureInstanceInfo{
Vcek: params.VcekCert,
CertChain: params.VcekChain,
AttestationReport: params.SNPReport,
RuntimeData: params.RuntimeData,
MAAToken: maaToken,
}
statement, err := json.Marshal(instanceInfo)
if err != nil {
return nil, fmt.Errorf("marshalling AzureInstanceInfo: %w", err)
}
return statement, nil
}
// getAttestationKey reads the attestation key put into the TPM during early boot.
func getAttestationKey(tpm io.ReadWriter) (*tpmclient.Key, error) {
ak, err := tpmclient.LoadCachedKey(tpm, tpmAkIdx)
if err != nil {
return nil, fmt.Errorf("reading HCL attestation key from TPM: %w", err)
}
return ak, nil
}
type imdsAPI interface {
getMAAURL(ctx context.Context) (string, error)
}
type maaTokenCreator interface {
newParameters(context.Context, []byte, io.ReadWriter) (maa.Parameters, error)
createToken(context.Context, io.ReadWriter, string, []byte, maa.Parameters) (string, error)
}