Add permission checks before reading from HDFS stream (#26716)

Add checks for special permissions before reading hdfs stream data. Also adds test from 
readonly repository fix. MiniHDFS will now start with an existing repository with a single snapshot 
contained within. Readonly Repository is created in tests and attempts to list the snapshots 
within this repo.

plugins/repository-hdfs/src/main/java/org/elasticsearch/repositories/hdfs/HdfsBlobContainer.java

@@ -23,6 +23,7 @@ import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.Options.CreateOpts;
 import org.apache.hadoop.fs.Path;
+import org.elasticsearch.SpecialPermission;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.blobstore.BlobMetaData;
 import org.elasticsearch.common.blobstore.BlobPath;
@@ -45,12 +46,14 @@ import java.util.Map;
 
 final class HdfsBlobContainer extends AbstractBlobContainer {
     private final HdfsBlobStore store;
+    private final HdfsSecurityContext securityContext;
     private final Path path;
     private final int bufferSize;
 
-    HdfsBlobContainer(BlobPath blobPath, HdfsBlobStore store, Path path, int bufferSize) {
+    HdfsBlobContainer(BlobPath blobPath, HdfsBlobStore store, Path path, int bufferSize, HdfsSecurityContext hdfsSecurityContext) {
         super(blobPath);
         this.store = store;
+        this.securityContext = hdfsSecurityContext;
         this.path = path;
         this.bufferSize = bufferSize;
     }
@@ -90,7 +93,9 @@ final class HdfsBlobContainer extends AbstractBlobContainer {
         // FSDataInputStream can open connections on read() or skip() so we wrap in
         // HDFSPrivilegedInputSteam which will ensure that underlying methods will
         // be called with the proper privileges.
-        return store.execute(fileContext -> new HDFSPrivilegedInputSteam(fileContext.open(new Path(path, blobName), bufferSize)));
+        return store.execute(fileContext ->
+            new HDFSPrivilegedInputSteam(fileContext.open(new Path(path, blobName), bufferSize), securityContext)
+        );
     }
 
     @Override
@@ -144,8 +149,11 @@ final class HdfsBlobContainer extends AbstractBlobContainer {
      */
     private static class HDFSPrivilegedInputSteam extends FilterInputStream {
 
-        HDFSPrivilegedInputSteam(InputStream in) {
+        private final HdfsSecurityContext securityContext;
+
+        HDFSPrivilegedInputSteam(InputStream in, HdfsSecurityContext hdfsSecurityContext) {
             super(in);
+            this.securityContext = hdfsSecurityContext;
         }
 
         public int read() throws IOException {
@@ -175,9 +183,10 @@ final class HdfsBlobContainer extends AbstractBlobContainer {
             });
         }
 
-        private static  <T> T doPrivilegedOrThrow(PrivilegedExceptionAction<T> action) throws IOException {
+        private <T> T doPrivilegedOrThrow(PrivilegedExceptionAction<T> action) throws IOException {
+            SpecialPermission.check();
             try {
-                return AccessController.doPrivileged(action);
+                return AccessController.doPrivileged(action, null, securityContext.getRestrictedExecutionPermissions());
             } catch (PrivilegedActionException e) {
                 throw (IOException) e.getCause();
             }

plugins/repository-hdfs/src/main/java/org/elasticsearch/repositories/hdfs/HdfsBlobStore.java

@@ -75,7 +75,7 @@ final class HdfsBlobStore implements BlobStore {
 
     @Override
     public BlobContainer blobContainer(BlobPath path) {
-        return new HdfsBlobContainer(path, this, buildHdfsPath(path), bufferSize);
+        return new HdfsBlobContainer(path, this, buildHdfsPath(path), bufferSize, securityContext);
     }
 
     private Path buildHdfsPath(BlobPath blobPath) {

plugins/repository-hdfs/src/main/java/org/elasticsearch/repositories/hdfs/HdfsRepository.java

@@ -132,7 +132,7 @@ public final class HdfsRepository extends BlobStoreRepository {
         hadoopConfiguration.setBoolean("fs.hdfs.impl.disable.cache", true);
 
         // Create the filecontext with our user information
-        // This will correctly configure the filecontext to have our UGI as it's internal user.
+        // This will correctly configure the filecontext to have our UGI as its internal user.
         return ugi.doAs((PrivilegedAction<FileContext>) () -> {
             try {
                 AbstractFileSystem fs = AbstractFileSystem.get(uri, hadoopConfiguration);

plugins/repository-hdfs/src/main/java/org/elasticsearch/repositories/hdfs/HdfsSecurityContext.java

@@ -56,7 +56,9 @@ class HdfsSecurityContext {
             // 1) hadoop dynamic proxy is messy with access rules
             new ReflectPermission("suppressAccessChecks"),
             // 2) allow hadoop to add credentials to our Subject
-            new AuthPermission("modifyPrivateCredentials")
+            new AuthPermission("modifyPrivateCredentials"),
+            // 3) RPC Engine requires this for re-establishing pooled connections over the lifetime of the client
+            new PrivateCredentialPermission("org.apache.hadoop.security.Credentials * \"*\"", "read")
         };
 
         // If Security is enabled, we need all the following elevated permissions:

plugins/repository-hdfs/src/test/resources/rest-api-spec/test/hdfs_repository/30_snapshot_readonly.yml

@@ -0,0 +1,29 @@
+# Integration tests for HDFS Repository plugin
+#
+# Tests retrieving information about snapshot
+#
+---
+"Get a snapshot - readonly":
+  # Create repository
+  - do:
+      snapshot.create_repository:
+        repository: test_snapshot_repository_ro
+        body:
+          type: hdfs
+          settings:
+            uri: "hdfs://localhost:9999"
+            path: "/user/elasticsearch/existing/readonly-repository"
+            readonly: true
+
+  # List snapshot info
+  - do:
+      snapshot.get:
+        repository: test_snapshot_repository_ro
+        snapshot: "_all"
+
+  - length: { snapshots: 1 }
+
+  # Remove our repository
+  - do:
+     snapshot.delete_repository:
+       repository: test_snapshot_repository_ro

plugins/repository-hdfs/src/test/resources/rest-api-spec/test/secure_hdfs_repository/30_snapshot_readonly.yml

@@ -0,0 +1,31 @@
+# Integration tests for HDFS Repository plugin
+#
+# Tests retrieving information about snapshot
+#
+---
+"Get a snapshot - readonly":
+  # Create repository
+  - do:
+      snapshot.create_repository:
+        repository: test_snapshot_repository_ro
+        body:
+          type: hdfs
+          settings:
+            uri: "hdfs://localhost:9998"
+            path: "/user/elasticsearch/existing/readonly-repository"
+            security:
+              principal: "elasticsearch@BUILD.ELASTIC.CO"
+            readonly: true
+
+  # List snapshot info
+  - do:
+      snapshot.get:
+        repository: test_snapshot_repository_ro
+        snapshot: "_all"
+
+  - length: { snapshots: 1 }
+
+  # Remove our repository
+  - do:
+     snapshot.delete_repository:
+       repository: test_snapshot_repository_ro

test/fixtures/hdfs-fixture/src/main/java/hdfs/MiniHDFS.java

@@ -19,7 +19,9 @@
 
 package hdfs;
 
+import java.io.File;
 import java.lang.management.ManagementFactory;
+import java.net.URL;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -29,9 +31,11 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
+import org.apache.commons.io.FileUtils;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
 import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.fs.permission.AclEntry;
 import org.apache.hadoop.fs.permission.AclEntryType;
 import org.apache.hadoop.fs.permission.FsAction;
@@ -100,15 +104,35 @@ public class MiniHDFS {
         }
         MiniDFSCluster dfs = builder.build();
 
-        // Set the elasticsearch user directory up
-        if (UserGroupInformation.isSecurityEnabled()) {
-            FileSystem fs = dfs.getFileSystem();
-            org.apache.hadoop.fs.Path esUserPath = new org.apache.hadoop.fs.Path("/user/elasticsearch");
+        // Configure contents of the filesystem
+        org.apache.hadoop.fs.Path esUserPath = new org.apache.hadoop.fs.Path("/user/elasticsearch");
+        try (FileSystem fs = dfs.getFileSystem()) {
+
+            // Set the elasticsearch user directory up
             fs.mkdirs(esUserPath);
-            List<AclEntry> acls = new ArrayList<>();
-            acls.add(new AclEntry.Builder().setType(AclEntryType.USER).setName("elasticsearch").setPermission(FsAction.ALL).build());
-            fs.modifyAclEntries(esUserPath, acls);
-            fs.close();
+            if (UserGroupInformation.isSecurityEnabled()) {
+                List<AclEntry> acls = new ArrayList<>();
+                acls.add(new AclEntry.Builder().setType(AclEntryType.USER).setName("elasticsearch").setPermission(FsAction.ALL).build());
+                fs.modifyAclEntries(esUserPath, acls);
+            }
+
+            // Install a pre-existing repository into HDFS
+            String directoryName = "readonly-repository";
+            String archiveName = directoryName + ".tar.gz";
+            URL readOnlyRepositoryArchiveURL = MiniHDFS.class.getClassLoader().getResource(archiveName);
+            if (readOnlyRepositoryArchiveURL != null) {
+                Path tempDirectory = Files.createTempDirectory(MiniHDFS.class.getName());
+                File readOnlyRepositoryArchive = tempDirectory.resolve(archiveName).toFile();
+                FileUtils.copyURLToFile(readOnlyRepositoryArchiveURL, readOnlyRepositoryArchive);
+                FileUtil.unTar(readOnlyRepositoryArchive, tempDirectory.toFile());
+
+                fs.copyFromLocalFile(true, true,
+                    new org.apache.hadoop.fs.Path(tempDirectory.resolve(directoryName).toAbsolutePath().toUri()),
+                    esUserPath.suffix("/existing/" + directoryName)
+                );
+
+                FileUtils.deleteDirectory(tempDirectory.toFile());
+            }
         }
 
         // write our PID file