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JavaScript: preserve sanitizer barriers on guarded phi inputs - #23005
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nikhilred2619 wants to merge 3 commits into
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| nd = DataFlow::valueNode(use) | ||
| ) | ||
| or | ||
| exists(BarrierGuard guard, DataFlowPrivate::SsaPhiInputNode input | |
| override Location getLocation() { result = expr.getLocation() } | ||
| } | ||
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| /** One incoming edge of an SSA phi, represented as a node so guards can block it. */ |
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🟡 Changes recommended
Captured-variable phi inputs are assigned to the wrong callable, breaking local flow and discarding call context, while the regression test lacks a recognized remote-input source.
3 open issues
What changed in this PR
Addresses #22848 by preserving branch-specific sanitizer guards when JavaScript and TypeScript values merge after fallback assignments, reducing false-positive security alerts.
Changes:
- Introduces guarded phi-input nodes while retaining direct flow for unguarded inputs.
- Adds fixtures for safe fallbacks, loops, incorrect guards, reflected XSS, and resource exhaustion.
- Refreshes expected results, removes an existing spurious shell-command alert, and adds a change note.
| File | Description |
|---|---|
javascript/ql/test/query-tests/Security/CWE-770/ResourceExhaustion/resource-exhaustion.js |
Adds a clamped-allocation scenario. |
javascript/ql/test/query-tests/Security/CWE-079/ReflectedXss/ReflectedXssGood.js |
Adds allowlist and regular-expression fallback scenarios. |
javascript/ql/test/query-tests/Security/CWE-078/UnsafeShellCommandConstruction/UnsafeShellCommandConstruction.expected |
Removes the spurious alert and related path output. |
javascript/ql/test/query-tests/Security/CWE-078/UnsafeShellCommandConstruction/lib/lib.js |
Changes the expectation comment to mark the sanitized command as safe. |
javascript/ql/test/library-tests/TaintTracking/sanitizer-guards.js |
Adds guarded-merge regression fixtures. |
javascript/ql/test/library-tests/TaintTracking/DataFlowTracking.expected |
Refreshes data-flow results and removes a resolved legacy mismatch. |
javascript/ql/test/library-tests/TaintTracking/BasicTaintTracking.expected |
Refreshes taint-flow results for the guard fixtures. |
javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowPrivate.qll |
Defines synthetic phi-input data-flow nodes. |
javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowNode.qll |
Creates phi-input nodes for guarded predecessors. |
javascript/ql/lib/semmle/javascript/dataflow/internal/BarrierGuards.qll |
Applies sanitizer barriers to individual phi inputs. |
javascript/ql/lib/semmle/javascript/dataflow/DataFlow.qll |
Splits guarded phi edges while retaining direct unguarded flow. |
javascript/ql/lib/semmle/javascript/dataflow/Configuration.qll |
Adapts legacy edge barriers to phi-input nodes. |
javascript/ql/lib/change-notes/2026-11-03-sanitizer-guard-phi-inputs.md |
Documents the sanitizer-guard improvement. |
Review effort: Max (auto)
| override string toString() { result = "[ssa-phi-input] " + phi.toString() } | ||
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| cached | ||
| override StmtContainer getContainer() { result = phi.getSourceVariable().getDeclaringContainer() } |
Comment on lines
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| function clampedAllocation(req) { | ||
| let n = parseInt(req.query.n); | ||
| if (n > 1024) { | ||
| n = 1024; | ||
| } | ||
| Buffer.alloc(n); // OK - n is at most 1024 (or an invalid allocation size) | ||
| } |
Comment on lines
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| exists(SsaPhiNode phi, BasicBlock bb | | ||
| pred = TSsaDefNode(phi.getInputFromBlock(bb).getDefinition()) and | ||
| succ = TSsaPhiInputNode(phi, bb) |
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Fixes #22848.
This change fixes false positives caused by sanitizer guards being lost across SSA phi inputs.
The fix preserves branch-specific barriers while keeping direct flow edges for inputs without a dominating condition.
I also added regression tests covering safe fallbacks, guarded loops, incorrect guard conditions, reflected XSS, and resource exhaustion. The existing spurious alert in
UnsafeShellCommandConstructionis removed.Testing: All 21 affected tests passed locally.
Related PR: #22873 addresses the same underlying issue. This version additionally limits synthetic phi-input nodes to guarded predecessor blocks and includes broader regression coverage.
Happy to make any adjustments based on feedback.