fix(cbor): incorrect decoding with subarrays

denoland · Jan 12, 2025 · 2ebfa11 · 2ebfa11
1 parent 2604b37
commit 2ebfa11
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Showing 2 changed files with 39 additions and 7 deletions.
diff --git a/cbor/_common_decode.ts b/cbor/_common_decode.ts
@@ -13,13 +13,13 @@ function calcLength(
   const view = new DataView(input.buffer);
   switch (aI) {
     case 24:
-      return [view.getUint8(offset), offset + 1];
+      return [view.getUint8(offset + input.byteOffset), offset + 1];
     case 25:
-      return [view.getUint16(offset), offset + 2];
+      return [view.getUint16(offset + input.byteOffset), offset + 2];
     case 26:
-      return [view.getUint32(offset), offset + 4];
+      return [view.getUint32(offset + input.byteOffset), offset + 4];
     default: // Only possible for it to be 27
-      return [view.getBigUint64(offset), offset + 8];
+      return [view.getBigUint64(offset + input.byteOffset), offset + 8];
   }
 }
 
@@ -315,11 +315,11 @@ function decodeSeven(
   const view = new DataView(input.buffer);
   switch (aI) {
     case 25:
-      return [view.getFloat16(offset), offset + 2];
+      return [view.getFloat16(offset + input.byteOffset), offset + 2];
     case 26:
-      return [view.getFloat32(offset), offset + 4];
+      return [view.getFloat32(offset + input.byteOffset), offset + 4];
     case 27:
-      return [view.getFloat64(offset), offset + 8];
+      return [view.getFloat64(offset + input.byteOffset), offset + 8];
     default:
       throw new RangeError(
         `Cannot decode value (0b111_${aI.toString(2).padStart(5, "0")})`,

diff --git a/cbor/decode_cbor_test.ts b/cbor/decode_cbor_test.ts
@@ -814,3 +814,35 @@ Deno.test("decodeCbor() rejecting tagNumber 259 due to invalid indefinite length
     "More bytes were expected",
   );
 });
+
+Deno.test("decodeCbor() correctly decoding with subarrays", () => {
+  let encodedData = encodeCbor(0);
+  let buffer = new Uint8Array(encodedData.length + 7);
+  buffer.set(encodedData, 7);
+  assertEquals(decodeCbor(buffer.subarray(7)), 0);
+
+  encodedData = encodeCbor(24);
+  buffer = new Uint8Array(encodedData.length + 7);
+  buffer.set(encodedData, 7);
+  assertEquals(decodeCbor(buffer.subarray(7)), 24);
+
+  encodedData = encodeCbor(2 ** 8);
+  buffer = new Uint8Array(encodedData.length + 7);
+  buffer.set(encodedData, 7);
+  assertEquals(decodeCbor(buffer.subarray(7)), 2 ** 8);
+
+  encodedData = encodeCbor(2 ** 16);
+  buffer = new Uint8Array(encodedData.length + 7);
+  buffer.set(encodedData, 7);
+  assertEquals(decodeCbor(buffer.subarray(7)), 2 ** 16);
+
+  encodedData = encodeCbor(2 ** 32);
+  buffer = new Uint8Array(encodedData.length + 7);
+  buffer.set(encodedData, 7);
+  assertEquals(decodeCbor(buffer.subarray(7)), 2n ** 32n);
+
+  encodedData = encodeCbor(3.14);
+  buffer = new Uint8Array(encodedData.length + 7);
+  buffer.set(encodedData, 7);
+  assertEquals(decodeCbor(buffer.subarray(7)), 3.14);
+});