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From mattf-horton <...@git.apache.org>
Subject [GitHub] incubator-metron pull request #439: add stellar external functions feature (...
Date Sun, 05 Feb 2017 01:57:05 GMT
Github user mattf-horton commented on a diff in the pull request:

    https://github.com/apache/incubator-metron/pull/439#discussion_r99479068
  
    --- 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 --
    
    What is the intent of this check?  The given regex only checks that there is *at least*
one alphanumeric character in the name argument, which doesn't say much. And you said it is
okay to use "_".  So perhaps you meant "^[\w.]+$".  This checks that the string, from beginning
to end, contains only "word" characters (A-Za-z_0-9) and period.  But this excludes unicode
strings for script names.
    
    Again, though, what is the intent?  The name of the script is rather irrelevant, unless
you actually have a true "white list", that is a dictionary of allowed names.  I don't know
how we would manage such a list in Metron.
    
    The only reliable security is restricted write permissions on the hard-coded /script directory.
 That needs to be documented, since violations open a really big trapdoor.


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