AB#2413: Add workflow for snp-report-verify

* Extend azure-snp-report-verify to also report fw SVNs.
* Add workflow based on azure-cvm to get maa-jwt and
verify it on a second runner.

hack/azure-snp-report-verify/verify.go

@@ -0,0 +1,134 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+// Verify verifies an MAA JWT and prints the SNP ID key digest on success.
+package main
+
+import (
+	"context"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"time"
+
+	"gopkg.in/square/go-jose.v2"
+	"gopkg.in/square/go-jose.v2/jwt"
+)
+
+type IsolationTEE struct {
+	IDKeyDigest   string `json:"x-ms-sevsnpvm-idkeydigest"`
+	TEESvn        int    `json:"x-ms-sevsnpvm-tee-svn"`
+	SNPFwSvn      int    `json:"x-ms-sevsnpvm-snpfw-svn"`
+	MicrocodeSvn  int    `json:"x-ms-sevsnpvm-microcode-svn"`
+	BootloaderSvn int    `json:"x-ms-sevsnpvm-bootloader-svn"`
+	GuestSvn      int    `json:"x-ms-sevsnpvm-guestsvn"`
+}
+
+func (i *IsolationTEE) PrintSVNs() {
+	fmt.Println("\tTEE SVN:", i.TEESvn)
+	fmt.Println("\tSNP FW SVN:", i.SNPFwSvn)
+	fmt.Println("\tMicrocode SVN:", i.MicrocodeSvn)
+	fmt.Println("\tBootloader SVN:", i.BootloaderSvn)
+	fmt.Println("\tGuest SVN:", i.GuestSvn)
+}
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Println("Usage:", os.Args[0], "<maa-jwt>")
+		return
+	}
+	report, err := getTEEReport(os.Args[1])
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println("Successfully validated ID key digest:", report.IDKeyDigest)
+	fmt.Println("Currently reported SVNs:")
+	report.PrintSVNs()
+}
+
+func getTEEReport(rawToken string) (IsolationTEE, error) {
+	// Parse token.
+	token, err := jwt.ParseSigned(rawToken)
+	if err != nil {
+		return IsolationTEE{}, err
+	}
+
+	// Get JSON Web Key set.
+	keySetBytes, err := httpGet(context.Background(), "https://sharedeus.eus.attest.azure.net/certs")
+	if err != nil {
+		return IsolationTEE{}, err
+	}
+	keySet, err := parseKeySet(keySetBytes)
+	if err != nil {
+		return IsolationTEE{}, err
+	}
+
+	// Get claims. Private claims contain ID Key digest.
+
+	var publicClaims jwt.Claims
+
+	var privateClaims struct {
+		IsolationTEE IsolationTEE `json:"x-ms-isolation-tee"`
+	}
+
+	if err := token.Claims(&keySet, &publicClaims, &privateClaims); err != nil {
+		return IsolationTEE{}, err
+	}
+	if err := publicClaims.Validate(jwt.Expected{Time: time.Now()}); err != nil {
+		return IsolationTEE{}, err
+	}
+
+	return privateClaims.IsolationTEE, nil
+}
+
+func parseKeySet(keySetBytes []byte) (jose.JSONWebKeySet, error) {
+	var rawKeySet struct {
+		Keys []struct {
+			X5c []string
+			Kid string
+		}
+	}
+	if err := json.Unmarshal(keySetBytes, &rawKeySet); err != nil {
+		return jose.JSONWebKeySet{}, err
+	}
+
+	var keySet jose.JSONWebKeySet
+	for _, key := range rawKeySet.Keys {
+		rawCert, _ := base64.StdEncoding.DecodeString(key.X5c[0])
+		cert, err := x509.ParseCertificate(rawCert)
+		if err != nil {
+			return jose.JSONWebKeySet{}, err
+		}
+		keySet.Keys = append(keySet.Keys, jose.JSONWebKey{KeyID: key.Kid, Key: cert.PublicKey})
+	}
+
+	return keySet, nil
+}
+
+func httpGet(ctx context.Context, url string) ([]byte, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, http.NoBody)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, errors.New(resp.Status)
+	}
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	return body, nil
+}