[SOLR-13181] NullPointerException in org.apache.solr.request.macro.MacroExpander

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 9.0
• Fix Version/s: 8.7
• Labels: diffblue newdev

Environment

Steps to reproduce

• Use a Linux machine.
• Build commit ea2c8ba of Solr as described in the section below.
• Build the films collection as described below.
• Start the server using the command ./bin/solr start -f -p 8983 -s /tmp/home
• Request the URL given in the bug description.

Compiling the server

git clone https://github.com/apache/lucene-solr
cd lucene-solr
git checkout ea2c8ba
ant compile
cd solr
ant server

Building the collection

We followed Exercise 2 from the Solr Tutorial. The attached file (home.zip) gives the contents of folder /tmp/home that you will obtain by following the steps below:

mkdir -p /tmp/home
echo '<?xml version="1.0" encoding="UTF-8" ?><solr></solr>' > /tmp/home/solr.xml

In one terminal start a Solr instance in foreground:

./bin/solr start -f -p 8983 -s /tmp/home

In another terminal, create a collection of movies, with no shards and no replication, and initialize it:

bin/solr create -c films
curl -X POST -H 'Content-type:application/json' --data-binary '{"add-field": {"name":"name", "type":"text_general", "multiValued":false, "stored":true}}' http://localhost:8983/solr/films/schema
curl -X POST -H 'Content-type:application/json' --data-binary '{"add-copy-field" : {"source":"*","dest":"_text_"}}' http://localhost:8983/solr/films/schema
./bin/post -c films example/films/films.json

• Assignee: David Smiley
• Reporter: Cesar Rodriguez
• Created: 29/Jan/19 16:08
• Updated: 04/Nov/20 15:22
• Resolved: 22/Sep/20 20:26

Description

Requesting the following URL causes Solr to return an HTTP 500 error response:

http://localhost:8983/solr/films/select?a=${${b}}

The error response seems to be caused by the following uncaught exception:

java.lang.StringIndexOutOfBoundsException: String index out of range: -4
	at java.lang.String.substring(String.java:1967)
	at org.apache.solr.request.macro.MacroExpander._expand(MacroExpander.java:150)
	at org.apache.solr.request.macro.MacroExpander.expand(MacroExpander.java:101)
	at org.apache.solr.request.macro.MacroExpander.expand(MacroExpander.java:65)
	at org.apache.solr.request.macro.MacroExpander.expand(MacroExpander.java:51)
	at org.apache.solr.request.json.RequestUtil.processParams(RequestUtil.java:159)
	at org.apache.solr.util.SolrPluginUtils.setDefaults(SolrPluginUtils.java:167)
	at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:196)
[...]

Parameter macro expansion seems to take place in org.apache.solr.request.macro.MacroExpander._expand(String val). From reading the code of the function it seems that macros are not expanded inside curly brackets ${...}, and so the ${b} inside

${${b}}

should not be expanded. But the function seems to fail to detect this specific case and graciously refuse to expand it.

A possible fix could be updating the idx variable when the StrParser detects that no valid identifier can be found inside the brackets. See attached file 0001-Macro-expander-fail-gracefully-on-unsupported-syntax.patch.

We found this bug using Diffblue Microservices Testing. Find more information on this fuzz testing campaign.

Issue Links

• links to: GitHub Pull Request #1877