Lockdown parsers with minimal privileges

There have been security issues with tika's parsers in the past...
let's take away the network, filesystem, everything we can.

In some way, parsing these docs is a lot like executing untrusted code.

I know its not pretty, but I think its worth it.

src/main/java/org/elasticsearch/mapper/attachments/TikaImpl.java

@@ -1,9 +1,42 @@
 package org.elasticsearch.mapper.attachments;
 
+import java.io.ByteArrayInputStream;
+
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.FilePermission;
 import java.io.IOException;
+import java.lang.reflect.ReflectPermission;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Path;
+import java.security.AccessControlContext;
 import java.security.AccessController;
+import java.security.PermissionCollection;
+import java.security.Permissions;
 import java.security.PrivilegedActionException;
 import java.security.PrivilegedExceptionAction;
+import java.security.ProtectionDomain;
+import java.security.SecurityPermission;
+import java.util.PropertyPermission;
 
 import org.apache.tika.Tika;
 import org.apache.tika.exception.TikaException;
@@ -11,9 +44,15 @@ import org.apache.tika.metadata.Metadata;
 import org.apache.tika.parser.AutoDetectParser;
 import org.apache.tika.parser.Parser;
 import org.elasticsearch.SpecialPermission;
-import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.bootstrap.JarHell;
+import org.elasticsearch.common.SuppressForbidden;
+import org.elasticsearch.common.io.PathUtils;
 
-/** do NOT make public */
+/**
+ * Runs tika with limited parsers and limited permissions.
+ * <p>
+ * Do NOT make public
+ */
 final class TikaImpl {
 
     /** subset of parsers for types we support */
@@ -52,9 +91,9 @@ final class TikaImpl {
             return AccessController.doPrivileged(new PrivilegedExceptionAction<String>() {
                 @Override
                 public String run() throws TikaException, IOException {
-                    return TIKA_INSTANCE.parseToString(StreamInput.wrap(content), metadata, limit);
+                    return TIKA_INSTANCE.parseToString(new ByteArrayInputStream(content), metadata, limit);
                 }
-            });
+            }, RESTRICTED_CONTEXT);
         } catch (PrivilegedActionException e) {
             // checked exception from tika: unbox it
             Throwable cause = e.getCause();
@@ -67,4 +106,54 @@ final class TikaImpl {
             }
         }
     }
+
+    // apply additional containment for parsers, this is intersected with the current permissions
+    // its hairy, but worth it so we don't have some XML flaw reading random crap from the FS
+    private static final AccessControlContext RESTRICTED_CONTEXT = new AccessControlContext(
+        new ProtectionDomain[] {
+            new ProtectionDomain(null, getRestrictedPermissions())
+        }
+    );
+
+    // compute some minimal permissions for parsers. they only get r/w access to the java temp directory,
+    // the ability to load some resources from JARs, and read sysprops
+    static PermissionCollection getRestrictedPermissions() {
+        Permissions perms = new Permissions();
+        // property/env access needed for parsing
+        perms.add(new PropertyPermission("*", "read"));
+        perms.add(new RuntimePermission("getenv.TIKA_CONFIG"));
+
+        // add permissions for resource access:
+        // classpath
+        addReadPermissions(perms, JarHell.parseClassPath());
+        // plugin jars
+        if (TikaImpl.class.getClassLoader() instanceof URLClassLoader) {
+            addReadPermissions(perms, ((URLClassLoader)TikaImpl.class.getClassLoader()).getURLs());
+        }
+        // jvm's java.io.tmpdir (needs read/write)
+        perms.add(new FilePermission(System.getProperty("java.io.tmpdir") + System.getProperty("file.separator") + "-",
+                                     "read,readlink,write,delete"));
+        // current hacks needed for POI/PDFbox issues:
+        perms.add(new SecurityPermission("putProviderProperty.BC"));
+        perms.add(new SecurityPermission("insertProvider"));
+        perms.add(new ReflectPermission("suppressAccessChecks"));
+        perms.setReadOnly();
+        return perms;
+    }
+
+    // add resources to (what is typically) a jar, but might not be (e.g. in tests/IDE)
+    @SuppressForbidden(reason = "adds access to jar resources")
+    static void addReadPermissions(Permissions perms, URL resources[]) {
+        try {
+            for (URL url : resources) {
+                Path path = PathUtils.get(url.toURI());
+                // resource itself
+                perms.add(new FilePermission(path.toString(), "read,readlink"));
+                // classes underneath
+                perms.add(new FilePermission(path.toString() + System.getProperty("file.separator") + "-", "read,readlink"));
+            }
+        } catch (URISyntaxException bogus) {
+            throw new RuntimeException(bogus);
+        }
+    }
 }

src/main/plugin-metadata/plugin-security.policy

@@ -17,8 +17,12 @@
  * under the License.
  */
 
+// NOTE: when modifying this file, look at restrictions in TikaImpl too
 grant {
-  // TODO: fix tika not to actually install bouncy castle like this
+  // needed to apply additional sandboxing to tika parsing
+  permission java.security.SecurityPermission "createAccessControlContext";
+
+  // TODO: fix PDFBox not to actually install bouncy castle like this
   permission java.security.SecurityPermission "putProviderProperty.BC";
   permission java.security.SecurityPermission "insertProvider";
   // TODO: fix POI XWPF to not do this: https://bz.apache.org/bugzilla/show_bug.cgi?id=58597