Adding a warning header when a license is about to expire (#64948)

* This change adds a warning header when a license is about to expire

Resolves #60562

* This change adds realm name of the realm used to perform authentication to the responses of _security/oidc/authenticate and _security/oidc/authenticate APIs

Resolves #53161

* Adding doc for the new API introduced by #64517 - /_security/saml/metadata/{realm}

Related to #49018

* Adding a warning header when a license is about to expire

Resolves #60562

* Addressing the PR feedback

* Switching back to adding the header during featureCheck to allow
warnings when authentication is disabled as well. Adding filterHeader
implementation to SecurityRestFilter exception handling to remove all
the warnings if authentication fails.

* Changing the wording for "expired" message to be consistent with the log
 messages; changing "today" calculation; adding a test case for failing
 authN to make sure we remove the warning header

* Small changes in the way we verify header in tests

* Nit changes

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

server/src/main/java/org/elasticsearch/http/DefaultRestChannel.java

@@ -123,7 +123,7 @@ public void sendResponse(RestResponse restResponse) {
 
             // Add all custom headers
             addCustomHeaders(httpResponse, restResponse.getHeaders());
-            addCustomHeaders(httpResponse, threadContext.getResponseHeaders());
+            addCustomHeaders(httpResponse, restResponse.filterHeaders(threadContext.getResponseHeaders()));
 
             // If our response doesn't specify a content-type header, set one
             setHeaderField(httpResponse, CONTENT_TYPE, restResponse.contentType(), false);

server/src/main/java/org/elasticsearch/rest/RestResponse.java

@@ -89,4 +89,8 @@ public Map<String, List<String>> getHeaders() {
             return customHeaders;
         }
     }
+
+    public Map<String, List<String>> filterHeaders(Map<String, List<String>> headers) {
+        return headers;
+    }
 }

x-pack/plugin/core/src/main/java/org/elasticsearch/license/LicenseService.java

@@ -81,6 +81,11 @@ public class LicenseService extends AbstractLifecycleComponent implements Cluste
      */
     static final TimeValue GRACE_PERIOD_DURATION = days(7);
 
+    /**
+     * Period before the license expires when warning starts being added to the response header
+     */
+    static final TimeValue LICENSE_EXPIRATION_WARNING_PERIOD = days(7);
+
     public static final long BASIC_SELF_GENERATED_LICENSE_EXPIRATION_MILLIS =
         XPackInfoResponse.BASIC_SELF_GENERATED_LICENSE_EXPIRATION_MILLIS;
 
@@ -124,7 +129,7 @@ public class LicenseService extends AbstractLifecycleComponent implements Cluste
 
     public static final String LICENSE_JOB = "licenseJob";
 
-    private static final DateFormatter DATE_FORMATTER = DateFormatter.forPattern("EEEE, MMMM dd, yyyy");
+    public static final DateFormatter DATE_FORMATTER = DateFormatter.forPattern("EEEE, MMMM dd, yyyy");
 
     private static final String ACKNOWLEDGEMENT_HEADER = "This license update requires acknowledgement. To acknowledge the license, " +
         "please read the following messages and update the license again, this time with the \"acknowledge=true\" parameter:";
@@ -475,7 +480,7 @@ private void updateLicenseState(LicensesMetadata licensesMetadata) {
     protected void updateLicenseState(final License license, Version mostRecentTrialVersion) {
         if (license == LicensesMetadata.LICENSE_TOMBSTONE) {
             // implies license has been explicitly deleted
-            licenseState.update(License.OperationMode.MISSING, false, mostRecentTrialVersion);
+            licenseState.update(License.OperationMode.MISSING, false, license.expiryDate(), mostRecentTrialVersion);
             return;
         }
         if (license != null) {
@@ -488,7 +493,7 @@ protected void updateLicenseState(final License license, Version mostRecentTrial
                 // date that is near Long.MAX_VALUE
                 active = time >= license.issueDate() && time - GRACE_PERIOD_DURATION.getMillis() < license.expiryDate();
             }
-            licenseState.update(license.operationMode(), active, mostRecentTrialVersion);
+            licenseState.update(license.operationMode(), active, license.expiryDate(), mostRecentTrialVersion);
 
             if (active) {
                 if (time < license.expiryDate()) {

x-pack/plugin/core/src/main/java/org/elasticsearch/license/LicenseStateListener.java

@@ -15,7 +15,7 @@
 public interface LicenseStateListener {
 
     /**
-     * Callback when the license state changes. See {@link XPackLicenseState#update(License.OperationMode, boolean, Version)}.
+     * Callback when the license state changes. See {@link XPackLicenseState#update(License.OperationMode, boolean, long, Version)}.
      */
     void licenseStateChanged();
 

x-pack/plugin/core/src/main/java/org/elasticsearch/license/XPackLicenseState.java

@@ -8,6 +8,8 @@
 import org.elasticsearch.Version;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.SuppressForbidden;
+import org.elasticsearch.common.logging.HeaderWarning;
 import org.elasticsearch.common.logging.LoggerMessageFormat;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.license.License.OperationMode;
@@ -19,17 +21,21 @@
 import java.util.EnumMap;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.LongAccumulator;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.LongSupplier;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
+import static org.elasticsearch.license.LicenseService.LICENSE_EXPIRATION_WARNING_PERIOD;
+
 /**
  * A holder for the current state of the license for all xpack features.
  */
@@ -395,7 +401,7 @@ private static boolean isBasic(OperationMode mode) {
         return mode == OperationMode.BASIC;
     }
 
-    /** A wrapper for the license mode and state, to allow atomically swapping. */
+    /** A wrapper for the license mode, state, and expiration date, to allow atomically swapping. */
     private static class Status {
 
         /** The current "mode" of the license (ie license type). */
@@ -404,9 +410,13 @@ private static class Status {
         /** True if the license is active, or false if it is expired. */
         final boolean active;
 
-        Status(OperationMode mode, boolean active) {
+        /** The current expiration date of the license; Long.MAX_VALUE if not available yet. */
+        final long licenseExpiryDate;
+
+        Status(OperationMode mode, boolean active, long licenseExpiryDate) {
             this.mode = mode;
             this.active = active;
+            this.licenseExpiryDate = licenseExpiryDate;
         }
     }
 
@@ -420,7 +430,7 @@ private static class Status {
     // XPackLicenseState. However, if status is read multiple times in a method, it can change in between
     // reads. Methods should use `executeAgainstStatus` and `checkAgainstStatus` to ensure that the status
     // is only read once.
-    private volatile Status status = new Status(OperationMode.TRIAL, true);
+    private volatile Status status = new Status(OperationMode.TRIAL, true, Long.MAX_VALUE);
 
     public XPackLicenseState(Settings settings, LongSupplier epochMillisProvider) {
         this.listeners = new CopyOnWriteArrayList<>();
@@ -468,12 +478,13 @@ private boolean checkAgainstStatus(Predicate<Status> statusPredicate) {
      *
      * @param mode   The mode (type) of the current license.
      * @param active True if the current license exists and is within its allowed usage period; false if it is expired or missing.
+     * @param expirationDate Expiration date of the current license.
      * @param mostRecentTrialVersion If this cluster has, at some point commenced a trial, the most recent version on which they did that.
      *                               May be {@code null} if they have never generated a trial license on this cluster, or the most recent
      *                               trial was prior to this metadata being tracked (6.1)
      */
-    void update(OperationMode mode, boolean active, @Nullable Version mostRecentTrialVersion) {
-        status = new Status(mode, active);
+    void update(OperationMode mode, boolean active, long expirationDate, @Nullable Version mostRecentTrialVersion) {
+        status = new Status(mode, active, expirationDate);
         listeners.forEach(LicenseStateListener::licenseStateChanged);
     }
 
@@ -509,12 +520,26 @@ public boolean isActive() {
     /**
      * Checks whether the given feature is allowed, tracking the last usage time.
      */
+    @SuppressForbidden(reason = "Argument to Math.abs() is definitely not Long.MIN_VALUE")
     public boolean checkFeature(Feature feature) {
         boolean allowed = isAllowed(feature);
         LongAccumulator maxEpochAccumulator = lastUsed.get(feature);
+        final long licenseExpiryDate = getLicenseExpiryDate();
+        final long diff = licenseExpiryDate - System.currentTimeMillis();
         if (maxEpochAccumulator != null) {
             maxEpochAccumulator.accumulate(epochMillisProvider.getAsLong());
         }
+
+        if (feature.minimumOperationMode.compareTo(OperationMode.BASIC) > 0 &&
+            LICENSE_EXPIRATION_WARNING_PERIOD.getMillis() > diff) {
+            final long days = TimeUnit.MILLISECONDS.toDays(diff);
+            final String expiryMessage = (days == 0 && diff > 0)? "expires today":
+                (diff > 0? String.format(Locale.ROOT, "will expire in [%d] days", days):
+                    String.format(Locale.ROOT, "expired on [%s]", LicenseService.DATE_FORMATTER.formatMillis(licenseExpiryDate)));
+            HeaderWarning.addWarning("Your license {}. " +
+                "Contact your administrator or update your license for continued use of features", expiryMessage);
+        }
+
         return allowed;
     }
 
@@ -631,6 +656,11 @@ public boolean isAllowedByLicense(OperationMode minimumMode, boolean needActive)
         });
     }
 
+    /** Return the current license expiration date. */
+    public long getLicenseExpiryDate() {
+        return executeAgainstStatus(status -> status.licenseExpiryDate);
+    }
+
     /**
      * A convenient method to test whether a feature is by license status.
      * @see #isAllowedByLicense(OperationMode, boolean)

x-pack/plugin/core/src/test/java/org/elasticsearch/license/TestUtils.java

@@ -360,21 +360,23 @@ public static class AssertingLicenseState extends XPackLicenseState {
         public final List<License.OperationMode> modeUpdates = new ArrayList<>();
         public final List<Boolean> activeUpdates = new ArrayList<>();
         public final List<Version> trialVersionUpdates = new ArrayList<>();
+        public final List<Long> expirationDateUpdates = new ArrayList<>();
 
         public AssertingLicenseState() {
             super(Settings.EMPTY, () -> 0);
         }
 
         @Override
-        void update(License.OperationMode mode, boolean active, Version mostRecentTrialVersion) {
+        void update(License.OperationMode mode, boolean active, long expirationDate, Version mostRecentTrialVersion) {
             modeUpdates.add(mode);
             activeUpdates.add(active);
+            expirationDateUpdates.add(expirationDate);
             trialVersionUpdates.add(mostRecentTrialVersion);
         }
     }
 
     /**
-     * A license state that makes the {@link #update(License.OperationMode, boolean, Version)}
+     * A license state that makes the {@link #update(License.OperationMode, boolean, long, Version)}
      * method public for use in tests.
      */
     public static class UpdatableLicenseState extends XPackLicenseState {
@@ -387,8 +389,8 @@ public UpdatableLicenseState(Settings settings) {
         }
 
         @Override
-        public void update(License.OperationMode mode, boolean active, Version mostRecentTrialVersion) {
-            super.update(mode, active, mostRecentTrialVersion);
+        public void update(License.OperationMode mode, boolean active, long expirationDate, Version mostRecentTrialVersion) {
+            super.update(mode, active, expirationDate, mostRecentTrialVersion);
         }
     }