feat(sev): pin cert chain and fetch VCEK from proxy

attestation/genoa_cert_chain.pem

@@ -0,0 +1,74 @@
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
+MIIGYzCCBBKgAwIBAgIDAgAAMEYGCSqGSIb3DQEBCjA5oA8wDQYJYIZIAWUDBAIC
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+/wMz1R1BHg==
+-----END CERTIFICATE-----

attestation/sev.go

@@ -1,28 +1,62 @@
 package attestation
 
 import (
+	_ "embed"
 	"encoding/base64"
 	"encoding/hex"
 	"fmt"
+	"net/url"
+	"strings"
 
 	"github.com/google/go-sev-guest/abi"
-	sevpb "github.com/google/go-sev-guest/proto/sevsnp"
+	"github.com/google/go-sev-guest/proto/sevsnp"
 	"github.com/google/go-sev-guest/verify"
+	"github.com/google/go-sev-guest/verify/trust"
 	"google.golang.org/protobuf/types/known/wrapperspb"
 
 	"github.com/tinfoilanalytics/verifier/util"
 )
 
+// https://kdsintf.amd.com/vcek/v1/Genoa/cert_chain
+//
+//go:embed genoa_cert_chain.pem
+var vcekGenoaCertChain []byte
+
+type getter struct{}
+
+func (_ *getter) Get(targetURL string) ([]byte, error) {
+	u, err := url.Parse(targetURL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse URL: %v", err)
+	}
+
+	if strings.HasSuffix(u.Path, "/cert_chain") {
+		if u.Path == "/vcek/v1/Genoa/cert_chain" {
+			return vcekGenoaCertChain, nil
+		} else {
+			return nil, fmt.Errorf("cert_chain is not supported")
+		}
+	}
+
+	u.Host = "kds-proxy.tinfoil.sh"
+	fmt.Println("Fetching URL:", u.String())
+	return util.Get(u.String())
+}
+
+var (
+	_ trust.HTTPSGetter = &getter{}
+)
+
 func verifySevAttestation(attestationDoc string) (*Measurement, []byte, error) {
 	attDocBytes, err := base64.StdEncoding.DecodeString(attestationDoc)
 	if err != nil {
 		return nil, nil, err
 	}
 
 	opts := verify.DefaultOptions()
-	opts.Getter = util.NewFetcher()
-	opts.Product = &sevpb.SevProduct{
-		Name:            sevpb.SevProduct_SEV_PRODUCT_GENOA,
+	opts.Getter = &getter{}
+	opts.Product = &sevsnp.SevProduct{
+		Name:            sevsnp.SevProduct_SEV_PRODUCT_GENOA,
 		MachineStepping: &wrapperspb.UInt32Value{Value: uint32(0)},
 	}
 

util/fetch.go

@@ -3,23 +3,17 @@ package util
 import (
 	"time"
 
-	"github.com/google/go-sev-guest/verify/trust"
 	"github.com/theupdateframework/go-tuf/v2/metadata/fetcher"
 )
 
 type Fetcher struct{}
 
-func (_ *Fetcher) Get(url string) ([]byte, error) {
-	return get(url)
-}
-
 func (_ *Fetcher) DownloadFile(urlPath string, maxLength int64, timeout time.Duration) ([]byte, error) {
-	return get(urlPath)
+	return Get(urlPath)
 }
 
 var (
-	_ trust.HTTPSGetter = &Fetcher{}
-	_ fetcher.Fetcher   = &Fetcher{}
+	_ fetcher.Fetcher = &Fetcher{}
 )
 
 func NewFetcher() *Fetcher {

util/fetch_other.go

@@ -9,7 +9,7 @@ import (
 	"net/http"
 )
 
-func get(url string) ([]byte, error) {
+func Get(url string) ([]byte, error) {
 	resp, err := http.Get(url)
 	if err != nil {
 		return nil, err

util/fetch_wasm.go

@@ -10,7 +10,7 @@ import (
 	fetch "marwan.io/wasm-fetch"
 )
 
-func get(url string) ([]byte, error) {
+func Get(url string) ([]byte, error) {
 	resp, err := fetch.Fetch(url, &fetch.Opts{
 		Method: fetch.MethodGet,
 		Signal: context.Background(),