Add Jazzer coverage-guided fuzzing for untrusted-input parsers

[seonghobae]

Summary

Adds Jazzer (Apache-2.0) coverage-guided fuzzing, integrated with JUnit 5, for the viewer's highest-value untrusted-input surfaces. Targets were chosen using CodeGraph to find the boundaries where attacker-controlled bytes are parsed.

Each harness asserts that arbitrary input only ever yields the documented failure mode, never an unhandled runtime exception.

Harness	Surface	Invariant
ArtifactTokenParserFuzzTest	ArtifactLinkService.verifyReadToken — splits + HMAC-verifies + Base64URL-decodes + parses 10 token fields (UUID, epoch Instants). Forges valid signatures to reach the deep parse path.	Only ArtifactTokenException (4xx) escapes
DocumentValidationFuzzTest	DefaultDocumentValidationService.validateOrThrow — filename/extension + policy-override headers	Only IllegalArgumentException escapes
TenantClaimsFuzzTest	TenantContext.fromHeaders + TenantAccessService.require — tenant/subject/permission + signed-claims timestamp/signature	fromHeaders never throws; require only throws ResponseStatusException

Bug found and fixed

Fuzzing immediately surfaced an unhandled java.time.DateTimeException in the artifact-token parser. Instant.ofEpochSecond(Long.parseLong(...)) throws DateTimeException (which is not an IllegalArgumentException) on an out-of-range but syntactically valid epoch second, escaping the catch (IllegalArgumentException) block in ArtifactLinkService.parseAndVerify and turning a would-be 401 into a 500. Fixed by also catching DateTimeException; the triggering input is committed as a regression seed (regression-datetime-epoch-overflow).

How it runs

• mvn test (default): @FuzzTest methods run in regression mode, replaying the committed seed corpus as fast unit tests — no libFuzzer driver, cross-platform. 348 tests green (was 336).
• JAZZER_FUZZ=1 mvn test -Dtest=<Harness>: libFuzzer drives each target for its bounded @FuzzTest(maxDuration = "60s") budget.

CI

.github/workflows/fuzz.yml fuzzes each target for 60s on PRs/pushes and 10min/target nightly (bounded to keep cost low). New crashers fail the job and upload the reproducer as an artifact.

Notes

• Permissive deps only (Jazzer = Apache-2.0). No new runtime deps, no secrets from env, no DB/object changes.
• Included a foundational coverage-guided fuzzing paper in docs/papers/ (Böhme et al., Coverage-based Greybox Fuzzing as Markov Chain, CCS 2016 — the AFLFast paper) and docs/fuzzing.md.
• CodeGraph was used to locate the target surfaces (codegraph init + codegraph explore).

🤖 Generated with Claude Code

https://claude.ai/code/session_01RTAMs4bpSZS77Xe3RQjv9P

[seonghobae]

Current-head salvage is now pushed as 722afde after merging main into the existing branch.

Verification evidence:

• CodeGraph re-index/exploration confirms the three Jazzer targets exercise artifact-token/date parsing, tenant claims, and document validation call paths.
• Fuzz regression suite: 13 tests, 0 failures/errors/skips.
• Full Maven suite: 416 tests, 0 failures/errors/skips.
• Maven Javadoc completed and generated target/reports/apidocs/index.html.
• actionlint and git diff --check pass.
• Trivy filesystem scan at Medium/High/Critical: 0 vulnerabilities, 0 secrets, 0 misconfigurations.
• OSV Scanner: no issues found. Maven Central returned transient HTTP 429 for several BOM enrichment requests, and the scanner logged each exact URL/reason before completing; the repository OSV policy also logs its documented CVE-2026-54515 false-positive filter for fixed Jackson 2.22.1.
• jazzer-junit 0.30.0 is explicitly present so @FuzzTest works both as regression replay and active fuzzing.
• Preserved original paper: Böhme, Pham, Roychoudhury, CCS 2016, DOI 10.1145/2976749.2978428; PDF SHA-256 fb3a7a74280659f86f83a934cae7bd35660e4c699dbd1dbd6825834bfe132151.
• The repo-local CodeQL workflow was removed; CodeQL remains centrally governed by ContextualWisdomLab/.github, eliminating duplicate runs and addressing the outstanding token-permission finding.

All previously reported mutable Action references are pinned to immutable SHAs on the current head.

[seonghobae]

Current-head 7f9ef32 fixes the actual Jazzer finding from job 86649790273.

Finding and fix:

• The uploaded crash reached DefaultDocumentValidationService.extensionOf with a filesystem-root filename. Path.getFileName() returned null and the subsequent toString() raised an undocumented NullPointerException.
• A focused regression first reproduced the exact failure with filename slash and a non-empty payload. The validator now treats a null leaf name as a missing extension and returns the documented IllegalArgumentException reason: File extension is required.
• A follow-up local fuzz run exposed a harness configuration error: the validator had no policy-override secret, so a legitimate server configuration IllegalStateException was incorrectly classified as an untrusted-input invariant failure. The fuzz fixture now uses a deterministic test-only secret, keeping the campaign scoped to attacker-controlled fields.
• The follow-up crash input is preserved in the Jazzer regression corpus.

Verification:

• Focused regression: red as NullPointerException before the fix, green after it.
• Jazzer: 7,290,470 executions in 61 seconds, 0 findings.
• Full Maven suite: 418 tests, 0 failures, 0 errors, 0 skipped.
• Javadoc generation: pass.
• CodeGraph synchronized current validation, fuzz, and conversion call paths.

Please evaluate only current SHA 7f9ef32.