feat: add Insecure Deserialization vulnerability module - #781
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Adds a new vulnerability module (CWE-502) with 4 levels, built with Challenge Mode annotations from the start: - LEVEL_1: basic unsafe deserialization, no type or integrity checks - LEVEL_2: arbitrary code execution via a custom readObject() hook - LEVEL_3: authentication bypass / privilege escalation via a forged isAdmin flag on a deserialized session token - LEVEL_4 (secure): HMAC-signed payload verified before a single byte is deserialized, plus a class allowlist via ObjectInputFilter No external gadget-chain library is used; the "arbitrary code execution" level demonstrates the mechanism with a self-contained readObject() hook instead of shipping a real RCE gadget. Every level was exercised against a running instance (both via the unit tests and by forging real serialized payloads with a separate javac/java script and hitting the endpoints over HTTP) to confirm the exploits work end-to-end and that LEVEL_4 correctly rejects the same forgery that succeeds against LEVEL_3.
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Included review availability: Your plan provides up to 2 included reviews per hour; 1 remains after this review. 📝 WalkthroughWalkthroughAdds an insecure deserialization module with four REST levels, serializable payloads, unsafe and HMAC-protected deserialization utilities, cookie-based challenge flows, UI resources, localization, and tests. ChangesInsecure Deserialization Module
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~60 minutes Change: Feature Sequence Diagram(s)sequenceDiagram
participant Client
participant InsecureDeserializationLoginController
participant InsecureDeserializationVulnerability
participant DeserializationUtils
Client->>InsecureDeserializationLoginController: Save settings or log in
InsecureDeserializationLoginController-->>Client: Set serialized cookie
Client->>InsecureDeserializationVulnerability: Submit cookie
InsecureDeserializationVulnerability->>DeserializationUtils: Deserialize or verify payload
DeserializationUtils-->>InsecureDeserializationVulnerability: Return object or failure
InsecureDeserializationVulnerability-->>Client: Return challenge response
Merge Risk: ⚪ Minimal · up to No concrete merge-blocking risk remains from the reviewed change. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 10.45% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 67 functions across 11 files. (1 skipped: 1 unsupported.)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## master #781 +/- ##
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+ Coverage 57.25% 58.89% +1.63%
- Complexity 791 867 +76
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Files 105 114 +9
Lines 4258 4530 +272
Branches 455 468 +13
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+ Hits 2438 2668 +230
- Misses 1617 1647 +30
- Partials 203 215 +12 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Codecov flagged low patch coverage on the error-handling branches. Adds cases for: deserializing a payload of an unexpected class on levels 1-3, a correctly-signed payload of a class outside LEVEL_4's allowlist getting rejected by the ObjectInputFilter, a too-short signed payload, and the default constructors/getters on the model classes.
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| try { | ||
| Object result = DeserializationUtils.deserializeUnsafe(payload); | ||
| if (result instanceof UserPreferences preferences) { |
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I think it would be worth thinking a bit more about the concrete use case here before implementation. I think is use case is importnatn that UI has options and that stores the serialized data but user should not be putting serialized data as that is really difficult for scanners and students to learn on why serialization is even needed.
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added a real theme/notifications form for level 1 that calls the endpoint to get an actual serialized preferences token, same as the app would issue for a real feature. the exploit is now tampering with that real token (change theme to a value the dropdown never offers) instead of hand-building a UserPreferences payload from nothing. pushed in cdf1e20, let me know if this matches what you had in mind or if you want a different concrete use case.
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@pereiravp I think there is some misunderstanding. My thought is that we should make the serialized object part of a normal application flow for all the levels.
My thought is to use a cookie-based flow consistently across the deserialization levels.
For example, we could have a normal Preferences UI:
- User selects a theme (e.g. Dark or Choosing larger font size)
- User clicks Save
- React sends the normal JSON preference to the backend
- Backend creates/stores the serialized Preferences object in a cookie
- On subsequent requests, the browser automatically sends the cookie back
- Backend deserializes the cookie and uses the resulting preferences when generating the response
- React reads the response and changes UI behaviour like making the theme as dark etc.
The important part is that the React UI does not need to read or manipulate the cookie. The browser handles that automatically. The cookie can also be HttpOnly, so the serialized value is not exposed to application JavaScript.
So we will not give any option to put Base64 encoded preferences in UI. It is part of cookie and user can manipulate it in the browser dev tools.
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that's clearer, thanks. rebuilt it that way: added InsecureDeserializationLoginController (same shape as IDORLoginController) with a normal save/login action per level (save preferences, visit a section, log in with a username) that sets an HttpOnly cookie carrying the serialized object. The vulnerable GET endpoints now read that cookie via @CookieValue and deserialize it, same as before. No Base64 box in the UI any more for any level, the exploit is editing the cookie in dev tools. Level 4 uses the same shape but with the signed cookie. Verified end to end against the packaged jar (save -> cookie set -> tamper -> resubmit -> accepted). pushed in 4a58060.
…yload Adds a theme/notifications form that calls the same endpoint to get a genuine serialized token, matching how the app would actually issue one. The exploit is now tampering with that real token instead of building a UserPreferences payload from scratch.
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Inline comments:
In
`@src/main/java/org/sasanlabs/service/vulnerability/deserialization/AuditLogGadget.java`:
- Line 42: Replace the unbounded AUDIT_TRAIL append in AuditLogGadget with a
bounded, synchronized FIFO or capped diagnostic store that retains only the
required recent events, while preserving the existing audit message and
challenge behavior.
In
`@src/main/java/org/sasanlabs/service/vulnerability/deserialization/InsecureDeserializationVulnerability.java`:
- Line 284: Update the deserialization flow around
DeserializationUtils.verifyAndDeserialize to reject oversized encoded payloads
before Base64 decoding or authentication, then configure ObjectInputFilter with
maxbytes, maxdepth, maxrefs, and maxarray limits before deserialization.
Preserve the SessionToken class restriction and existing valid-payload behavior.
In `@src/main/resources/i18n/messages.properties`:
- Line 1375: Update the insecure deserialization payload placeholder values,
including the entries at the referenced neighboring keys, to encode their
literal angle-bracket markers as < and > so they render as text
through innerHTML.
In
`@src/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.js`:
- Line 70: Update the result rendering around the innerHTML assignments to treat
data.content as untrusted text: preserve trusted challenge markup while
inserting the deserialized content via a text node or equivalent safe text API,
and apply the same protection to both affected assignments.
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src/main/java/org/sasanlabs/internal/utility/exception/DeserializationException.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/AuditLogGadget.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/DeserializationUtils.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/InsecureDeserializationVulnerability.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/SessionToken.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/UserPreferences.javasrc/main/java/org/sasanlabs/vulnerability/types/VulnerabilityType.javasrc/main/resources/i18n/messages.propertiessrc/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.csssrc/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.htmlsrc/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.jssrc/test/java/org/sasanlabs/service/vulnerability/deserialization/InsecureDeserializationVulnerabilityTest.java
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…ed content - AuditLogGadget.AUDIT_TRAIL now evicts old entries past 50 so repeated level 2 submissions can't grow it unbounded. - verifyAndDeserialize rejects oversized encoded input before decoding and configures ObjectInputFilter with maxdepth/maxarray/maxrefs/maxbytes, not just the class allowlist. - messages.properties payload placeholders escape angle brackets so they render as text instead of being parsed as HTML. - level 1's JS builds the challenge/result DOM instead of using innerHTML on server content, since a tampered payload can put arbitrary text (including markup) into that response.
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Inline comments:
In
`@src/main/java/org/sasanlabs/service/vulnerability/deserialization/DeserializationUtils.java`:
- Around line 96-98: Update verifyAndDeserialize to validate base64Payload for
null before calling length(), and throw DeserializationException for null input
while preserving the existing maximum-length check and behavior for valid
payloads.
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src/main/java/org/sasanlabs/service/vulnerability/deserialization/AuditLogGadget.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/DeserializationUtils.javasrc/main/resources/i18n/messages.propertiessrc/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.js
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- src/main/resources/i18n/messages.properties
- src/main/java/org/sasanlabs/service/vulnerability/deserialization/AuditLogGadget.java
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…sted payload Adds InsecureDeserializationLoginController, mirroring IDORLoginController's shape: a normal save/login action per level (preferences, section visit, username) that hands the browser an HttpOnly cookie carrying the serialized object. The vulnerable GET endpoints now read that cookie via @CookieValue and deserialize it exactly as before; nothing in the UI accepts a raw Base64 payload any more. The exploit for every level is editing the cookie in the browser's dev tools, matching how a real app would actually issue this kind of token.
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Inline comments:
In `@src/main/resources/i18n/messages.properties`:
- Line 1375: Update the three INSECURE_DESERIALIZATION_LEVEL_1_PAYLOAD_VALUE
payload examples, including the entries at the referenced neighboring keys, to
use literal angle brackets instead of encoded < and > entities so
textContent renders the intended placeholders.
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src/main/java/org/sasanlabs/service/vulnerability/deserialization/DeserializationUtils.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/InsecureDeserializationLoginController.javasrc/main/java/org/sasanlabs/service/vulnerability/deserialization/InsecureDeserializationVulnerability.javasrc/main/resources/i18n/messages.propertiessrc/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.csssrc/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.htmlsrc/main/resources/static/templates/InsecureDeserialization/LEVEL_1/InsecureDeserialization.jssrc/test/java/org/sasanlabs/service/vulnerability/deserialization/InsecureDeserializationLoginControllerTest.javasrc/test/java/org/sasanlabs/service/vulnerability/deserialization/InsecureDeserializationVulnerabilityTest.java
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…entities The challenge card and the level's own displayChallenge() both render this text with textContent, so HTML entities show up literally instead of being decoded.
3 participants
Summary
Closes #528.
New vulnerability module (CWE-502: Deserialization of Untrusted Data), built with Challenge Mode annotations from the start, following the module's proposed levels:
UserPreferencesand the server rebuilds it as-is.readObject()hook onAuditLogGadgetruns attacker-controlled logic the instant the bytes are deserialized, before the app ever sees the result. No external gadget-chain library is used — the effect (appending to an in-memory audit trail) is observable without granting real code execution, but demonstrates exactly the mechanism real gadget chains (Commons Collections, etc.) exploit.isAdminflag read straight off a deserializedSessionToken, no signature. Forge one withisAdmin=trueand get admin access.SessionTokenflow, but the payload is HMAC-signed server-side and the signature is verified before a single byte is deserialized; a class allowlist viaObjectInputFilteradds defense in depth. The exact forgery that works on LEVEL_3 is rejected here.Verification
Every level was exercised end-to-end against a running instance (
./gradlew bootRun), not just unit tests: forged real Java-serialized payloads with a standalonejavac/javascript (matching class names/fields) and hit each endpoint over HTTP with curl, confirming levels 1-3 are exploitable as designed and level 4 correctly rejects the level-3 forgery via signature mismatch.Test plan
./gradlew compileJava./gradlew spotlessCheckInsecureDeserializationVulnerabilityTest, 10 cases) passMessageBundleDuplicateKeyTestandVulnerableAppRestControllerTestpassSummary by CodeRabbit
New Features
Tests