Preserve ApiKey credentials for async verification (#51389)

The ApiKeyService would aggressively "close" ApiKeyCredentials objects
during processing. However, under rare circumstances, the verfication
of the secret key would be performed asychronously and may need access
to the SecureString after it had been closed by the caller.

The trigger for this would be if the cache already held a Future for
that ApiKey, but the future was not yet complete. In this case the
verification of the secret key would take place asynchronously on the
generic thread pool.

This commit moves the "close" of the credentials to the body of the
listener so that it only occurs after key verification is complete.

Backport of: #51244

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/ApiKeyService.java

@@ -302,27 +302,16 @@ public class ApiKeyService {
             }
 
             if (credentials != null) {
-                final String docId = credentials.getId();
+                loadApiKeyAndValidateCredentials(ctx, credentials, ActionListener.wrap(
-                final GetRequest getRequest = client
+                    response -> {
-                        .prepareGet(SECURITY_MAIN_ALIAS, SINGLE_MAPPING_NAME, docId)
-                        .setFetchSource(true)
-                        .request();
-                executeAsyncWithOrigin(ctx, SECURITY_ORIGIN, getRequest, ActionListener.<GetResponse>wrap(response -> {
-                    if (response.isExists()) {
-                        try (ApiKeyCredentials ignore = credentials) {
-                            final Map<String, Object> source = response.getSource();
-                            validateApiKeyCredentials(docId, source, credentials, clock, listener);
-                        }
-                    } else {
                         credentials.close();
-                        listener.onResponse(
+                        listener.onResponse(response);
-                            AuthenticationResult.unsuccessful("unable to find apikey with id " + credentials.getId(), null));
+                    },
+                    e -> {
+                        credentials.close();
+                        listener.onFailure(e);
                     }
-                }, e -> {
+                ));
-                    credentials.close();
-                    listener.onResponse(AuthenticationResult.unsuccessful("apikey authentication for id " + credentials.getId() +
-                        " encountered a failure", e));
-                }), client::get);
             } else {
                 listener.onResponse(AuthenticationResult.notHandled());
             }
@@ -331,6 +320,27 @@ public class ApiKeyService {
         }
     }
 
+    private void loadApiKeyAndValidateCredentials(ThreadContext ctx, ApiKeyCredentials credentials,
+                                                  ActionListener<AuthenticationResult> listener) {
+        final String docId = credentials.getId();
+        final GetRequest getRequest = client
+            .prepareGet(SECURITY_MAIN_ALIAS, SINGLE_MAPPING_NAME, docId)
+            .setFetchSource(true)
+            .request();
+        executeAsyncWithOrigin(ctx, SECURITY_ORIGIN, getRequest, ActionListener.<GetResponse>wrap(response -> {
+                if (response.isExists()) {
+                    final Map<String, Object> source = response.getSource();
+                    validateApiKeyCredentials(docId, source, credentials, clock, listener);
+                } else {
+                    listener.onResponse(
+                        AuthenticationResult.unsuccessful("unable to find apikey with id " + credentials.getId(), null));
+                }
+            },
+            e -> listener.onResponse(AuthenticationResult.unsuccessful(
+                "apikey authentication for id " + credentials.getId() + " encountered a failure", e))),
+            client::get);
+    }
+
     /**
      * The current request has been authenticated by an API key and this method enables the
      * retrieval of role descriptors that are associated with the api key
@@ -543,7 +553,8 @@ public class ApiKeyService {
         return null;
     }
 
-    private static boolean verifyKeyAgainstHash(String apiKeyHash, ApiKeyCredentials credentials) {
+    // Protected instance method so this can be mocked
+    protected boolean verifyKeyAgainstHash(String apiKeyHash, ApiKeyCredentials credentials) {
         final char[] apiKeyHashChars = apiKeyHash.toCharArray();
         try {
             Hasher hasher = Hasher.resolveFromHash(apiKeyHash.toCharArray());

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/ApiKeyServiceTests.java

@@ -13,6 +13,7 @@ import org.elasticsearch.client.Client;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.common.xcontent.ToXContent;
 import org.elasticsearch.common.xcontent.XContentBuilder;
@@ -41,6 +42,7 @@ import org.elasticsearch.xpack.security.support.SecurityIndexManager;
 import org.elasticsearch.xpack.security.test.SecurityMocks;
 import org.junit.After;
 import org.junit.Before;
+import org.mockito.Mockito;
 
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
@@ -54,6 +56,8 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.elasticsearch.xpack.core.security.authz.store.ReservedRolesStore.SUPERUSER_ROLE_DESCRIPTOR;
 import static org.hamcrest.Matchers.arrayContaining;
@@ -431,16 +435,7 @@ public class ApiKeyServiceTests extends ESTestCase {
         Hasher hasher = randomFrom(Hasher.PBKDF2, Hasher.BCRYPT4, Hasher.BCRYPT);
         final char[] hash = hasher.hash(new SecureString(apiKey.toCharArray()));
 
-        Map<String, Object> sourceMap = new HashMap<>();
+        Map<String, Object> sourceMap = buildApiKeySourceDoc(hash);
-        sourceMap.put("doc_type", "api_key");
-        sourceMap.put("api_key_hash", new String(hash));
-        sourceMap.put("role_descriptors", Collections.singletonMap("a role", Collections.singletonMap("cluster", "all")));
-        sourceMap.put("limited_by_role_descriptors", Collections.singletonMap("limited role", Collections.singletonMap("cluster", "all")));
-        Map<String, Object> creatorMap = new HashMap<>();
-        creatorMap.put("principal", "test_user");
-        creatorMap.put("metadata", Collections.emptyMap());
-        sourceMap.put("creator", creatorMap);
-        sourceMap.put("api_key_invalidated", false);
 
         ApiKeyService service = createApiKeyService(Settings.EMPTY);
         ApiKeyCredentials creds = new ApiKeyCredentials(randomAlphaOfLength(12), new SecureString(apiKey.toCharArray()));
@@ -488,6 +483,64 @@ public class ApiKeyServiceTests extends ESTestCase {
         assertThat(service.getFromCache(creds.getId()).success, is(true));
     }
 
+    public void testAuthenticateWhileCacheBeingPopulated() throws Exception {
+        final String apiKey = randomAlphaOfLength(16);
+        Hasher hasher = randomFrom(Hasher.PBKDF2, Hasher.BCRYPT4, Hasher.BCRYPT);
+        final char[] hash = hasher.hash(new SecureString(apiKey.toCharArray()));
+
+        Map<String, Object> sourceMap = buildApiKeySourceDoc(hash);
+
+        ApiKeyService realService = createApiKeyService(Settings.EMPTY);
+        ApiKeyService service  = Mockito.spy(realService);
+
+        // Used to block the hashing of the first api-key secret so that we can guarantee
+        // that a second api key authentication takes place while hashing is "in progress".
+        final Semaphore hashWait = new Semaphore(0);
+        final AtomicInteger hashCounter = new AtomicInteger(0);
+        doAnswer(invocationOnMock -> {
+            hashCounter.incrementAndGet();
+            hashWait.acquire();
+            return invocationOnMock.callRealMethod();
+        }).when(service).verifyKeyAgainstHash(any(String.class), any(ApiKeyCredentials.class));
+
+        final ApiKeyCredentials creds = new ApiKeyCredentials(randomAlphaOfLength(12), new SecureString(apiKey.toCharArray()));
+        final PlainActionFuture<AuthenticationResult> future1 = new PlainActionFuture<>();
+
+        // Call the top level authenticate... method because it has been known to be buggy in async situations
+        writeCredentialsToThreadContext(creds);
+        mockSourceDocument(creds.getId(), sourceMap);
+
+        // This needs to be done in another thread, because we need it to not complete until we say so, but it should not block this test
+        this.threadPool.generic().execute(() -> service.authenticateWithApiKeyIfPresent(threadPool.getThreadContext(), future1));
+
+        // Wait for the first credential validation to get to the blocked state
+        assertBusy(() -> assertThat(hashCounter.get(), equalTo(1)));
+        if (future1.isDone()) {
+            // We do this [ rather than assertFalse(isDone) ] so we can get a reasonable failure message
+            fail("Expected authentication to be blocked, but was " + future1.actionGet());
+        }
+
+        // The second authentication should pass (but not immediately, but will not block)
+        PlainActionFuture<AuthenticationResult> future2 = new PlainActionFuture<>();
+
+        service.authenticateWithApiKeyIfPresent(threadPool.getThreadContext(), future2);
+
+        assertThat(hashCounter.get(), equalTo(1));
+        if (future2.isDone()) {
+            // We do this [ rather than assertFalse(isDone) ] so we can get a reasonable failure message
+            fail("Expected authentication to be blocked, but was " + future2.actionGet());
+        }
+
+        hashWait.release();
+
+        assertThat(future1.actionGet(TimeValue.timeValueSeconds(2)).isAuthenticated(), is(true));
+        assertThat(future2.actionGet(TimeValue.timeValueMillis(100)).isAuthenticated(), is(true));
+
+        CachedApiKeyHashResult cachedApiKeyHashResult = service.getFromCache(creds.getId());
+        assertNotNull(cachedApiKeyHashResult);
+        assertThat(cachedApiKeyHashResult.success, is(true));
+    }
+
     public void testApiKeyCacheDisabled() {
         final String apiKey = randomAlphaOfLength(16);
         Hasher hasher = randomFrom(Hasher.PBKDF2, Hasher.BCRYPT4, Hasher.BCRYPT);
@@ -496,16 +549,7 @@ public class ApiKeyServiceTests extends ESTestCase {
             .put(ApiKeyService.CACHE_TTL_SETTING.getKey(), "0s")
             .build();
 
-        Map<String, Object> sourceMap = new HashMap<>();
+        Map<String, Object> sourceMap = buildApiKeySourceDoc(hash);
-        sourceMap.put("doc_type", "api_key");
-        sourceMap.put("api_key_hash", new String(hash));
-        sourceMap.put("role_descriptors", Collections.singletonMap("a role", Collections.singletonMap("cluster", "all")));
-        sourceMap.put("limited_by_role_descriptors", Collections.singletonMap("limited role", Collections.singletonMap("cluster", "all")));
-        Map<String, Object> creatorMap = new HashMap<>();
-        creatorMap.put("principal", "test_user");
-        creatorMap.put("metadata", Collections.emptyMap());
-        sourceMap.put("creator", creatorMap);
-        sourceMap.put("api_key_invalidated", false);
 
         ApiKeyService service = createApiKeyService(settings);
         ApiKeyCredentials creds = new ApiKeyCredentials(randomAlphaOfLength(12), new SecureString(apiKey.toCharArray()));
@@ -517,10 +561,40 @@ public class ApiKeyServiceTests extends ESTestCase {
         assertNull(cachedApiKeyHashResult);
     }
 
-    private ApiKeyService createApiKeyService(Settings settings) {
+    private ApiKeyService createApiKeyService(Settings baseSettings) {
+        final Settings settings = Settings.builder()
+            .put(XPackSettings.API_KEY_SERVICE_ENABLED_SETTING.getKey(), true)
+            .put(baseSettings)
+            .build();
         return new ApiKeyService(settings, Clock.systemUTC(), client, licenseState, securityIndex,
             ClusterServiceUtils.createClusterService(threadPool), threadPool);
     }
 
+    private Map<String, Object> buildApiKeySourceDoc(char[] hash) {
+        Map<String, Object> sourceMap = new HashMap<>();
+        sourceMap.put("doc_type", "api_key");
+        sourceMap.put("api_key_hash", new String(hash));
+        sourceMap.put("role_descriptors", Collections.singletonMap("a role", Collections.singletonMap("cluster", "all")));
+        sourceMap.put("limited_by_role_descriptors", Collections.singletonMap("limited role", Collections.singletonMap("cluster", "all")));
+        Map<String, Object> creatorMap = new HashMap<>();
+        creatorMap.put("principal", "test_user");
+        creatorMap.put("metadata", Collections.emptyMap());
+        sourceMap.put("creator", creatorMap);
+        sourceMap.put("api_key_invalidated", false);
+        return sourceMap;
+    }
+
+    private void writeCredentialsToThreadContext(ApiKeyCredentials creds) {
+        final String credentialString = creds.getId() + ":" + creds.getKey();
+        this.threadPool.getThreadContext().putHeader("Authorization",
+            "ApiKey " + Base64.getEncoder().encodeToString(credentialString.getBytes(StandardCharsets.US_ASCII)));
+    }
+
+    private void mockSourceDocument(String id, Map<String, Object> sourceMap) throws IOException {
+        try (XContentBuilder builder = JsonXContent.contentBuilder()) {
+            builder.map(sourceMap);
+            SecurityMocks.mockGetRequest(client, id, BytesReference.bytes(builder));
+        }
+    }
 
 }