Merge pull request #4701 from daniel-beck/JENKINS-62133

core/src/main/java/jenkins/security/ResourceDomainConfiguration.java

@@ -33,6 +33,7 @@ import jenkins.model.Jenkins;
 import jenkins.model.JenkinsLocationConfiguration;
 import jenkins.model.identity.InstanceIdentityProvider;
 import jenkins.util.UrlHelper;
+import org.apache.commons.io.IOUtils;
 import org.jenkinsci.Symbol;
 import org.kohsuke.accmod.Restricted;
 import org.kohsuke.accmod.restrictions.Beta;
@@ -48,6 +49,7 @@ import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;
+import java.nio.charset.StandardCharsets;
 import java.security.interfaces.RSAPublicKey;
 import java.util.Base64;
 import java.util.logging.Level;
@@ -168,8 +170,11 @@ public final class ResourceDomainConfiguration extends GlobalConfiguration {
                 }
                 // response is error
                 String responseMessage = httpURLConnection.getResponseMessage();
-                if (responseCode == 404 && responseMessage.equals(ERROR_RESPONSE)) {
-                    return FormValidation.ok(Messages.ResourceDomainConfiguration_ResourceResponse());
+                if (responseCode == 404) {
+                    String responseBody = String.join("", IOUtils.readLines(httpURLConnection.getErrorStream(), StandardCharsets.UTF_8));
+                    if (responseMessage.contains(ERROR_RESPONSE) || responseBody.contains(ERROR_RESPONSE)) {
+                        return FormValidation.ok(Messages.ResourceDomainConfiguration_ResourceResponse());
+                    }
                 }
                 return FormValidation.error(Messages.ResourceDomainConfiguration_FailedIdentityCheck(responseCode, responseMessage));
             }