Druid javascript security

Skill cxcscmu/SkillLearnBench/skills/b1-one-shot-claude-haiku-4-5/fix-security-bug/druid-javascript-security

Securing Apache Druid's JavaScript execution engine against code injection and security bypass attacks.From its SKILL.md

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npx -y skills add cxcscmu/SkillLearnBench --skill druid-javascript-security

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SKILL.md

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Apache Druid JavaScript Security

Vulnerability Context

Apache Druid versions up to 0.20.0 have a critical vulnerability in JavaScript expression handling where an empty key ("") can bypass security settings, allowing arbitrary code execution through the java.lang.Runtime API.

Key Components

1. JavaScript Transform Spec

Located in indexing service modules
Handles JavaScript expressions for data transformation
Uses GraalVM or Nashorn engine for JavaScript execution

2. Security Filter Structure

The vulnerable structure looks like:

{
  "filter": {
    "type": "javascript",
    "function": "function(){...}",
    "": {
      "enabled": true
    }
  }
}

The empty key "" is the bypass vector.

Patching Strategy

1. Input Validation

Reject filter/transform specs with empty string keys
Validate all keys in security configuration objects
Enforce strict schema validation before passing to JavaScript engine

2. Security Configuration Enforcement

Ensure enabled flag is only checked for known, valid keys
Implement whitelist of allowed configuration keys
Reject any configuration with unexpected keys

3. Code Changes Needed

Typically in classes handling JavaScript filter/transform deserialization
Common classes: JavaScriptFilter, JavaScriptExpressionValidator, JavaScript spec handlers
May need to add validation in both request parsing and execution phases

Testing the Fix

Exploit Request (should fail)

POST /druid/indexer/v1/sampler
{
  "type": "index",
  "spec": {
    "dataSchema": {
      "transformSpec": {
        "filter": {
          "type": "javascript",
          "function": "function(){java.lang.Runtime.getRuntime().exec('malicious_command');}",
          "": {
            "enabled": true
          }
        }
      }
    }
  }
}

Legitimate Request (should work)

POST /druid/indexer/v1/sampler
{
  "type": "index",
  "spec": {
    "dataSchema": {
      "transformSpec": {
        "filter": {
          "type": "javascript",
          "function": "function(row){return true;}"
        }
      }
    }
  }
}

Common Druid File Locations

JavaScript filter implementation: processing/src/main/java/org/apache/druid/query/filter/JavaScriptFilter.java
Indexing service: indexing-service/src/main/java/org/apache/druid/indexing/
Transform specs: Related to dataSchema handling

Jackson Deserialization Considerations

The vulnerability likely involves improper validation during Jackson deserialization. Use raw @JsonAnySetter or similar mechanisms to catch unexpected properties and validate them strictly before further processing.

What ships with it

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