/* Copyright (c) Edgeless Systems GmbH SPDX-License-Identifier: AGPL-3.0-only */ package trustedlaunch import ( "context" "crypto/x509" "encoding/json" "errors" "fmt" "io" "net/http" "github.com/edgelesssys/constellation/v2/internal/attestation" "github.com/edgelesssys/constellation/v2/internal/attestation/variant" "github.com/edgelesssys/constellation/v2/internal/attestation/vtpm" tpmclient "github.com/google/go-tpm-tools/client" "github.com/google/go-tpm/tpm2" ) const ( tpmAkIdx = 0x81000003 tpmAkCertIdx = 0x1C101D0 ) // Issuer for Azure trusted launch TPM attestation. type Issuer struct { variant.AzureTrustedLaunch *vtpm.Issuer hClient httpClient } // NewIssuer initializes a new Azure Issuer. func NewIssuer(log attestation.Logger) *Issuer { i := &Issuer{ hClient: &http.Client{}, } i.Issuer = vtpm.NewIssuer( vtpm.OpenVTPM, getAttestationKey, i.getAttestationCert, log, ) return i } // akSigner holds the attestation key certificate and the corresponding CA certificate. type akSigner struct { AkCert []byte CA []byte } // getAttestationCert returns the DER encoded certificate of the TPM's attestation key and it's CA. func (i *Issuer) getAttestationCert(ctx context.Context, tpm io.ReadWriteCloser, _ []byte) ([]byte, error) { certDER, err := tpm2.NVReadEx(tpm, tpmAkCertIdx, tpm2.HandleOwner, "", 0) if err != nil { return nil, fmt.Errorf("reading attestation key certificate from TPM: %w", err) } cert, err := x509.ParseCertificate(certDER) if err != nil { return nil, fmt.Errorf("parsing attestation key certificate: %w", err) } // try to load the CA certificate from the issuing certificate URL // any error is ignored and the next URL is tried // if no CA certificate can be loaded, an error is returned var caCert *x509.Certificate for _, caCertURL := range cert.IssuingCertificateURL { req, err := http.NewRequestWithContext(ctx, http.MethodGet, caCertURL, nil) if err != nil { continue } resp, err := i.hClient.Do(req) if err != nil { continue } defer resp.Body.Close() if resp.StatusCode != http.StatusOK { continue } caCertDER, err := io.ReadAll(resp.Body) if err != nil { continue } caCert, err = x509.ParseCertificate(caCertDER) if err != nil { continue } break } if caCert == nil { return nil, errors.New("failed to load CA certificate") } signerInfo := akSigner{ AkCert: certDER, CA: caCert.Raw, } return json.Marshal(signerInfo) } // getAttestationKey reads the Azure trusted launch attesation key. func getAttestationKey(tpm io.ReadWriter) (*tpmclient.Key, error) { ak, err := tpmclient.LoadCachedKey(tpm, tpmAkIdx) if err != nil { return nil, fmt.Errorf("reading attestation key from TPM: %w", err) } return ak, nil } type httpClient interface { Do(req *http.Request) (*http.Response, error) }