Status

Current state: Accepted, being implemented

Discussion thread: https://lists.apache.org/thread/7qqknryoh4hxv2s7291j8g5shlcbock3

JIRA:

Released: Solr 10.x (TBD)

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Motivation

Java Security Manager (JSM) was permanently removed in Java 24 (JEP 486). Solr previously relied on JSM to sandbox plugin code at runtime — restricting unauthorized file access, outbound network connections, System.exit() calls, and child process spawning. Without a replacement, Solr running on Java 24+ provides no runtime enforcement of these protections, leaving the JVM and any loaded plugin code unconstrained.

The OpenSearch project faced the same problem and solved it for OpenSearch 3.0 using a Java agent based on ByteBuddy instrumentation. See their write-up and the agent-sm source (Apache 2.0). This SIP proposes to use and adapt this approach.

Public Interfaces

The following new operator-facing interfaces are introduced:

• Agent JAR — server/lib/ext/solr-agent-sm-*.jar, loaded automatically via -javaagent: by the startup scripts when present.
• Default policy file — server/etc/agent-security.policy (JDK-style .policy syntax; ships with Solr; not intended for operator editing).
• Operator extension file — server/etc/agent-security-extra.policy (optional; absent is non-fatal; entries tagged source=OPERATOR in violation logs).
• Environment variables — SOLR_SECURITY_AGENT_MODE=warn|enforce (default: warn) and SOLR_SECURITY_AGENT_SKIP=true to disable.
• Violation metrics — per-type counters at /admin/metrics under security.agent.violations.file, .network, .exit, .exec.
• Deprecations — SolrPaths.assertPathAllowed() deprecated for new callers; existing JSM security.policy and solr-tests.policy files marked deprecated.

Proposed Changes

A new Gradle subproject solr/agent-sm/ will be created, producing a standalone Java agent JAR adapted from the Apache 2.0-licensed OpenSearch libs/agent-sm. The agent uses ByteBuddy @Advice instrumentation and StackWalker (Java 9+) to intercept JDK APIs at the bytecode level — applying to all code in the JVM including plugins, without requiring any code changes. It is virtual-thread safe (no thread-identity assumptions).

Four protection categories:

• File access — reads and writes restricted to configured Solr directories. Windows UNC paths (\\host\share) unconditionally blocked. Symlinks resolved to real path before policy check.
• Network access — outbound connections restricted to a permitted endpoint list. The default policy permits loopback addresses and all intra-cluster Solr and ZooKeeper traffic using port-based wildcards (*:<solr.port>, *:<zk-port>), covering all cluster nodes regardless of join order.
• JVM shutdown — System.exit() and Runtime.halt() restricted to an approved call-site list (SolrCLI, SolrDispatchFilter by default).
• Process execution — ProcessBuilder.start() and Runtime.exec() restricted to an approved call-site list (empty by default in production).

The initial release will use warn-only mode — violations are logged but operations are not blocked. Operators opt into enforce mode via SOLR_SECURITY_AGENT_MODE=enforce. A future release will flip the default.

Policy files use standard JDK .policy syntax extended with Solr variable substitution (${solr.home}, ${solr.port}, ${solr.zk.port}, etc.). The operator extension file ships with commented-out examples for all known modules that require external network access (jwt-auth, extraction/Tika, opentelemetry, s3-repository, gcs-repository, cross-dc-manager).

For a detailed specification and implementation plan - generated by Github's SpecKit, see http://cominvent.com/pub/jsm-spec.html.

Compatibility, Deprecation, and Migration Plan

• JSM removal in Java 24 is mandatory and outside Solr's control (see — startup scripts disable the security manager flag on Java ≥ 24).
• The default policy covers standard Solr directory layouts and intra-cluster traffic. Most deployments will require no configuration changes.
• Warn-only default ensures zero disruption on upgrade. Operators can review violation logs before enabling enforce mode.
• Modules that connect to external services (OIDC, OTLP, S3, GCS, Kafka, remote Tika) may require operator-added policy entries in enforce mode. Consider each one. Perhaps only those with a user-injected URL must be manually added?
• The existing server/etc/security.policy and solr-tests.policy JSM files are deprecated and retained as migration reference only; they are not enforced by the JVM on Java 24+.
• SolrPaths.assertPathAllowed() is deprecated for new callers; existing call sites are retained as defense-in-depth.

Security Considerations

This SIP restores runtime sandboxing for Solr on Java 24+ after JSM removal. Key points:

• All code in the JVM — including third-party plugins — is subject to enforcement without any plugin-side changes required.
• The agent runs in the JVM bootstrap classloader; it cannot be bypassed by application-level classloader manipulation.
• Intra-cluster network policy uses port-based wildcards rather than a host list, which is intentional: inter-node Solr HTTP is already PKI-authenticated, and a host list derived at startup would always be incomplete as nodes join incrementally.
• Warn-only default is a deliberate trade-off to avoid regressions in the plugin ecosystem; it does not reduce security versus the current state (no enforcement at all on Java 24+).

Test Plan

• Unit tests for PolicyLoader — variable substitution, merging, error handling.
• Interceptor unit tests for each protection category — permitted operations succeed, violations blocked/logged, counters increment.
• Full-stack integration test (SolrAgentIntegrationTest) running in enforce mode — all four protection categories exercised.
• Existing JSM-related tests repurposed where applicable.
• Virtual thread compatibility test suite — no false positives or negatives under Project Loom.
• Broader Solr integration suite run in warn mode to detect unexpected violations before the enforce-mode flip in a future release.

Rejected Alternatives

• Staying on Java < 24 — not viable long-term; Solr must support current Java LTS releases.
• Removing JSM protections without any replacement — unacceptable security regression.
• OS-level hardening only (systemd, seccomp) — not cross-platform; does not cover Windows or macOS.
• Dynamic ZK-watcher-based network policy — correct but significantly more complex; adds ZK client dependency to the agent JAR. Superseded by port-based wildcards for intra-cluster traffic.
• Building a Java agent from scratch — higher effort with no functional advantage over adapting the Apache 2.0-licensed OpenSearch implementation.