feat(code-injection): replace RCE detector

Use an owned canary to distinguish heuristic reads from confirmed
execution and avoid substring-only reports that confuse string
literals with code execution.

Author: oetr

docs/bug-detectors.md

@@ -98,17 +98,58 @@ using Jest in `.jazzerjsrc.json`:
 { "disableBugDetectors": ["prototype-pollution"] }
 ```
 
-## Remote Code Execution
+## Code Injection
 
-Hooks the `eval` and `Function` functions and reports a finding if the fuzzer
-was able to pass a special string to `eval` and to the function body of
-`Function`.
+Installs a canary on `globalThis` and hooks the `eval` and `Function` functions.
+The before-hooks guide the fuzzer toward injecting the active canary identifier
+into code strings. The detector reports two fatal stages by default:
 
-_Disable with:_ `--disableBugDetectors=remote-code-execution` in CLI mode; or
-when using Jest in `.jazzerjsrc.json`:
+- `Potential Code Injection (Canary Accessed)` - some code resolved the canary.
+  This high-recall heuristic catches cases where dynamically produced code reads
+  or stores the canary before executing it later.
+- `Confirmed Code Injection (Canary Invoked)` - the callable canary returned by
+  the getter was invoked.
+
+The detector can be configured in the
+[custom hooks](./fuzz-settings.md#customhooks--arraystring) file.
+
+- `disableAccessReporting` - disables the stage-1 access finding while keeping
+  invocation reporting active.
+- `disableInvocationReporting` - disables the stage-2 invocation finding.
+- `ignoreAccess(rule)` - suppresses stage-1 findings matching the shown stack
+  excerpt.
+- `ignoreInvocation(rule)` - suppresses stage-2 findings matching the shown
+  stack excerpt.
+- `stackPattern` accepts either a string or a `RegExp` and is matched against
+  the shown stack excerpt after removing the leading `Error` line and Jazzer.js
+  frames. The remaining stack text is matched as shown, including path
+  separators and column numbers.
+
+The detector must be able to install a canary on at least one active global
+object. Locked-down environments that forbid this should disable the detector
+explicitly.
+
+Here is an example configuration in the
+[custom hooks](./fuzz-settings.md#customhooks--arraystring) file:
+
+```javascript
+const { getBugDetectorConfiguration } = require("@jazzer.js/bug-detectors");
+
+getBugDetectorConfiguration("code-injection")
+	?.ignoreAccess({
+		stackPattern: "handlebars/runtime.js:87",
+	})
+	?.disableInvocationReporting();
+```
+
+Findings print a generic example suppression snippet. Copy/paste it and adapt
+`stackPattern` to a stable substring or `RegExp` from the shown stack above.
+
+_Disable with:_ `--disableBugDetectors=code-injection` in CLI mode; or when
+using Jest in `.jazzerjsrc.json`:
 
 ```json
-{ "disableBugDetectors": ["remote-code-execution"] }
+{ "disableBugDetectors": ["code-injection"] }
 ```
 
 ## Server-Side Request Forgery (SSRF)

packages/bug-detectors/internal/code-injection.ts

@@ -0,0 +1,258 @@
+/*
+ * Copyright 2026 Code Intelligence GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import type { Context } from "vm";
+
+import {
+	getJazzerJsGlobal,
+	guideTowardsContainment,
+	registerAfterEachCallback,
+	reportAndThrowFinding,
+	reportFinding,
+} from "@jazzer.js/core";
+import { registerBeforeHook } from "@jazzer.js/hooking";
+
+import { bugDetectorConfigurations } from "../configuration";
+import { ensureCanary } from "../shared/code-injection-canary";
+import {
+	buildGenericSuppressionSnippet,
+	captureStack,
+	getUserFacingStackLines,
+	IgnoreList,
+	type IgnoreRule,
+} from "../shared/finding-suppression";
+
+export type { IgnoreRule } from "../shared/finding-suppression";
+
+type PendingAccess = {
+	canaryName: string;
+	stack: string;
+	invoked: boolean;
+};
+
+/**
+ * Configuration for the Code Injection bug detector.
+ * Controls the reporting and suppression of dynamic code evaluation findings.
+ */
+export interface CodeInjectionConfig {
+	/**
+	 * Disables Stage 1 (Access) reporting entirely.
+	 * The detector will no longer report when the canary is merely read.
+	 */
+	disableAccessReporting(): this;
+	/**
+	 * Disables Stage 2 (Invocation) reporting entirely.
+	 * The detector will no longer report when the canary is actually executed.
+	 */
+	disableInvocationReporting(): this;
+	/**
+	 * Suppresses Stage 1 (Access) findings that match the provided rule.
+	 * Use this to silence safe heuristic reads such as template lookups.
+	 */
+	ignoreAccess(rule: IgnoreRule): this;
+	/**
+	 * Suppresses Stage 2 (Invocation) findings that match the provided rule.
+	 * Use this only for known-safe execution sinks in test environments.
+	 */
+	ignoreInvocation(rule: IgnoreRule): this;
+}
+
+class CodeInjectionConfigImpl implements CodeInjectionConfig {
+	private _reportAccess = true;
+	private _reportInvocation = true;
+	private readonly _ignoredAccessRules = new IgnoreList();
+	private readonly _ignoredInvocationRules = new IgnoreList();
+
+	disableAccessReporting(): this {
+		this._reportAccess = false;
+		return this;
+	}
+
+	disableInvocationReporting(): this {
+		this._reportInvocation = false;
+		return this;
+	}
+
+	ignoreAccess(rule: IgnoreRule): this {
+		this._ignoredAccessRules.add(rule);
+		return this;
+	}
+
+	ignoreInvocation(rule: IgnoreRule): this {
+		this._ignoredInvocationRules.add(rule);
+		return this;
+	}
+
+	shouldReportAccess(stack: string): boolean {
+		return this._reportAccess && !this._ignoredAccessRules.matches(stack);
+	}
+
+	shouldReportInvocation(stack: string): boolean {
+		return (
+			this._reportInvocation && !this._ignoredInvocationRules.matches(stack)
+		);
+	}
+}
+
+const config = new CodeInjectionConfigImpl();
+bugDetectorConfigurations.set("code-injection", config);
+
+const canaryCache = new WeakMap<object, string>();
+const pendingAccesses: PendingAccess[] = [];
+
+ensureActiveCanary();
+registerAfterEachCallback(flushPendingAccesses);
+
+registerBeforeHook(
+	"eval",
+	"",
+	false,
+	function beforeEvalHook(
+		_thisPtr: unknown,
+		params: unknown[],
+		hookId: number,
+	) {
+		const canaryName = ensureActiveCanary();
+
+		const code = params[0];
+		if (typeof code === "string") {
+			guideTowardsContainment(code, canaryName, hookId);
+		}
+	},
+);
+
+registerBeforeHook(
+	"Function",
+	"",
+	false,
+	function beforeFunctionHook(
+		_thisPtr: unknown,
+		params: unknown[],
+		hookId: number,
+	) {
+		const canaryName = ensureActiveCanary();
+		if (params.length === 0) return;
+
+		const functionBody = params[params.length - 1];
+		if (functionBody == null) return;
+
+		let functionBodySource: string;
+		try {
+			functionBodySource = String(functionBody);
+		} catch {
+			return;
+		}
+		// The hook has already performed Function's body coercion; reuse it so
+		// user-provided toString methods are not invoked a second time.
+		params[params.length - 1] = functionBodySource;
+
+		guideTowardsContainment(functionBodySource, canaryName, hookId);
+	},
+);
+
+function getVmContext(): Context | undefined {
+	return getJazzerJsGlobal<Context>("vmContext");
+}
+
+function ensureActiveCanary(): string {
+	return ensureCanary(
+		[
+			{ label: "vmContext", object: getVmContext() },
+			{ label: "globalThis", object: globalThis },
+		],
+		canaryCache,
+		createCanaryDescriptor,
+	);
+}
+
+function createCanaryDescriptor(canaryName: string): PropertyDescriptor {
+	return {
+		get() {
+			const accessStack = captureStack();
+			const pendingAccess = config.shouldReportAccess(accessStack)
+				? {
+						canaryName,
+						stack: accessStack,
+						invoked: false,
+					}
+				: undefined;
+			if (pendingAccess) {
+				pendingAccesses.push(pendingAccess);
+			}
+
+			return function canaryCall() {
+				const invocationStack = captureStack();
+				if (config.shouldReportInvocation(invocationStack)) {
+					if (pendingAccess) {
+						pendingAccess.invoked = true;
+					}
+					reportAndThrowFinding(
+						buildFindingMessage(
+							"Confirmed Code Injection (Canary Invoked)",
+							`invoked canary: ${canaryName}`,
+							invocationStack,
+							"ignoreInvocation",
+							"If this execution sink is expected in your test environment, suppress it:",
+						),
+						false,
+					);
+				}
+			};
+		},
+		enumerable: false,
+		configurable: false,
+	};
+}
+
+function flushPendingAccesses(): void {
+	for (const pendingAccess of pendingAccesses.splice(0)) {
+		if (pendingAccess.invoked) {
+			continue;
+		}
+		reportFinding(
+			buildFindingMessage(
+				"Potential Code Injection (Canary Accessed)",
+				`accessed canary: ${pendingAccess.canaryName}`,
+				pendingAccess.stack,
+				"ignoreAccess",
+				"If this is a safe heuristic read, suppress it to continue fuzzing for code execution. Add this to your custom hooks:",
+			),
+			false,
+		);
+	}
+}
+
+function buildFindingMessage(
+	title: string,
+	action: string,
+	stack: string,
+	suppressionMethod: "ignoreAccess" | "ignoreInvocation",
+	hint: string,
+): string {
+	const relevantStackLines = getUserFacingStackLines(stack);
+	const message = [`${title} -- ${action}`];
+	if (relevantStackLines.length > 0) {
+		message.push(...relevantStackLines);
+	}
+	message.push(
+		"",
+		`[!] ${hint}`,
+		"    Example only: copy/paste it and adapt `stackPattern` to your needs.",
+		"",
+		buildGenericSuppressionSnippet("code-injection", suppressionMethod),
+	);
+	return message.join("\n");
+}