crossmate

commit 7bb71f25ea102117aa53ccbeafbb70abbea810fd
parent 85509e32c9d7703346dd45e607972f5f7de3d33c
Author: Michael Camilleri <[email protected]>
Date:   Thu,  2 Jul 2026 02:33:35 +0900

Reject malformed puzzle geometry

This commit makes the JSON to XD converter fail closed before malformed
puzzle metadata can reach unchecked grid operations. Non-positive
dimensions are rejected before grid ranges are built, and the expected
cell count now uses overflow-aware multiplication instead of trusting
`width * height` to be representable.

Clue cell references are also validated before answers are read. A clue
that points outside the parsed grid now throws ConversionError rather
than trapping while building the clue answer, while valid block cells
still contribute no answer text as before.

Co-Authored-By: Codex GPT 5.5 <[email protected]>

Diffstat:
M
Crossmate/Services/NYTToXDConverter.swift
 | 
19
+++++++++++++++++--
M
Tests/Unit/NYTToXDConverterTests.swift
 | 
46
++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 63 insertions(+), 2 deletions(-)
diff --git a/Crossmate/Services/NYTToXDConverter.swift b/Crossmate/Services/NYTToXDConverter.swift
@@ -52,11 +52,16 @@ enum NYTToXDConverter {
             throw ConversionError(message: "Missing dimensions.")
         }
 
+        guard width > 0, height > 0 else {
+            throw ConversionError(message: "Invalid dimensions (\(width)x\(height)).")
+        }
+
         guard let cells = body["cells"] as? [Any] else {
             throw ConversionError(message: "Missing cells.")
         }
 
-        guard cells.count == width * height else {
+        let (expectedCellCount, overflowed) = width.multipliedReportingOverflow(by: height)
+        guard !overflowed, cells.count == expectedCellCount else {
             throw ConversionError(message: "Cell count (\(cells.count)) does not match dimensions (\(width)x\(height)).")
         }
 
@@ -216,7 +221,17 @@ enum NYTToXDConverter {
 
             // Build answer from cell indices
             let cellIndices = clue["cells"] as? [Int] ?? []
-            let answerStr = cellIndices.compactMap { answers[$0] }.joined()
+            var answerStr = ""
+            for cellIndex in cellIndices {
+                guard answers.indices.contains(cellIndex) else {
+                    throw ConversionError(
+                        message: "Clue \(label) \(direction) references invalid cell index \(cellIndex)."
+                    )
+                }
+                if let answer = answers[cellIndex] {
+                    answerStr += answer
+                }
+            }
 
             let prefix = direction == "Across" ? "A" : "D"
             let line = "\(prefix)\(label). \(clueText) ~ \(answerStr)"
diff --git a/Tests/Unit/NYTToXDConverterTests.swift b/Tests/Unit/NYTToXDConverterTests.swift
@@ -122,6 +122,52 @@ struct NYTToXDConverterTests {
         return values
     }
 
+    // MARK: - Malformed input
+
+    @Test("Invalid dimensions are rejected before grid ranges are built")
+    func invalidDimensionsRejected() throws {
+        let root: [String: Any] = [
+            "publicationDate": "2025-04-04",
+            "body": [[
+                "dimensions": ["width": -1, "height": -1],
+                "cells": [["answer": "A"]],
+                "clues": [[
+                    "label": "1",
+                    "direction": "Across",
+                    "cells": [0],
+                    "text": [["plain": "malformed"]]
+                ]]
+            ]]
+        ]
+        let data = try JSONSerialization.data(withJSONObject: root)
+
+        #expect(throws: NYTToXDConverter.ConversionError.self) {
+            try NYTToXDConverter.convert(jsonData: data)
+        }
+    }
+
+    @Test("Clue cell indices outside the grid are rejected")
+    func invalidClueCellIndicesRejected() throws {
+        let root: [String: Any] = [
+            "publicationDate": "2025-04-05",
+            "body": [[
+                "dimensions": ["width": 1, "height": 1],
+                "cells": [["answer": "A"]],
+                "clues": [[
+                    "label": "1",
+                    "direction": "Across",
+                    "cells": [0, 1],
+                    "text": [["plain": "malformed"]]
+                ]]
+            ]]
+        ]
+        let data = try JSONSerialization.data(withJSONObject: root)
+
+        #expect(throws: NYTToXDConverter.ConversionError.self) {
+            try NYTToXDConverter.convert(jsonData: data)
+        }
+    }
+
     // MARK: - Header emission
 
     @Test("NYT metadata uses weekday title and publisher")