🛡️ Sentinel: [security improvement] Refactor toolExists to use direct Process execution

.jules/sentinel.md

@@ -0,0 +1,4 @@
+## 2024-04-15 - Command injection in CacheCategory probes
+**Vulnerability:** `CacheCategory.toolExists` passes user-supplied input to a shell via `/usr/bin/which \(tool)`, introducing command injection if the category allows dynamic inputs.
+**Learning:** Shell evaluation with string interpolation `\()` is unsafe. Passing dynamic inputs through `/bin/bash -c` risks evaluating shell operators.
+**Prevention:** Avoid shell evaluations where direct execution of `Process` with structured `arguments` is possible.

Sources/Cacheout/Models/CacheCategory.swift

@@ -186,8 +186,23 @@ struct CacheCategory: Identifiable, Hashable {
     }
 
     private func toolExists(_ tool: String) -> Bool {
-        let result = shell("/usr/bin/which \(tool)")
-        return result != nil && !result!.isEmpty
+        let process = Process()
+        process.executableURL = URL(fileURLWithPath: "/usr/bin/which")
+        process.arguments = [tool]
+        process.standardOutput = FileHandle.nullDevice
+        process.standardError = FileHandle.nullDevice
+        process.environment = [
+            "PATH": "/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin",
+            "HOME": FileManager.default.homeDirectoryForCurrentUser.path
+        ]
+
+        do {
+            try process.run()
+            process.waitUntilExit()
+            return process.terminationStatus == 0
+        } catch {
+            return false
+        }
     }
 
     private func runProbe(_ command: String) -> String? {