[major] add X-Admin-Token to vault requests (#9)

Author: joecorall

main.go

@@ -76,6 +76,10 @@ type UnsealResponse struct {
 	Progress int  `json:"progress"`
 }
 
+type metadataAccessTokenResponse struct {
+	AccessToken string `json:"access_token"`
+}
+
 func main() {
 	log.Println("Starting the vault-init service...")
 
@@ -166,7 +170,14 @@ func main() {
 			stop()
 		default:
 		}
-		response, err := httpClient.Head(vaultAddr + "/v1/sys/health")
+		request, err := newVaultRequest(http.MethodHead, vaultAddr+"/v1/sys/health", nil)
+		if err != nil {
+			log.Println(err)
+			time.Sleep(checkInterval)
+			continue
+		}
+
+		response, err := httpClient.Do(request)
 
 		if response != nil && response.Body != nil {
 			response.Body.Close()
@@ -238,7 +249,7 @@ func initialize() {
 	}
 
 	r := bytes.NewReader(initRequestData)
-	request, err := http.NewRequest("PUT", vaultAddr+"/v1/sys/init", r)
+	request, err := newVaultRequest(http.MethodPut, vaultAddr+"/v1/sys/init", r)
 	if err != nil {
 		log.Println(err)
 		return
@@ -384,7 +395,7 @@ func unsealOne(key string) (bool, error) {
 	}
 
 	r := bytes.NewReader(unsealRequestData)
-	request, err := http.NewRequest(http.MethodPut, vaultAddr+"/v1/sys/unseal", r)
+	request, err := newVaultRequest(http.MethodPut, vaultAddr+"/v1/sys/unseal", r)
 	if err != nil {
 		return false, err
 	}
@@ -461,6 +472,58 @@ func processTLSConfig(cfg *tls.Config, serverName, caCert, caPath string) error
 	return nil
 }
 
+func newVaultRequest(method, url string, body io.Reader) (*http.Request, error) {
+	request, err := http.NewRequest(method, url, body)
+	if err != nil {
+		return nil, err
+	}
+
+	accessToken, err := accessTokenFromMetadata()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get access token from metadata server: %w", err)
+	}
+
+	request.Header.Set("X-Admin-Token", accessToken)
+	request.Header.Set("Accept", "application/json")
+	if method == http.MethodPut {
+		request.Header.Set("Content-Type", "application/json")
+	}
+
+	return request, nil
+}
+
+func accessTokenFromMetadata() (string, error) {
+	const metadataTokenURL = "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token"
+
+	request, err := http.NewRequest(http.MethodGet, metadataTokenURL, nil)
+	if err != nil {
+		return "", err
+	}
+	request.Header.Set("Metadata-Flavor", "Google")
+
+	client := &http.Client{Timeout: 5 * time.Second}
+	response, err := client.Do(request)
+	if err != nil {
+		return "", err
+	}
+	defer response.Body.Close()
+
+	if response.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("unexpected status code: %d", response.StatusCode)
+	}
+
+	var tokenResponse metadataAccessTokenResponse
+	if err := json.NewDecoder(response.Body).Decode(&tokenResponse); err != nil {
+		return "", err
+	}
+
+	if tokenResponse.AccessToken == "" {
+		return "", fmt.Errorf("metadata server returned empty access token")
+	}
+
+	return tokenResponse.AccessToken, nil
+}
+
 func boolFromEnv(env string, def bool) bool {
 	val := os.Getenv(env)
 	if val == "" {