Reject v24.0 metadata instead of silently decoding wrong offsets

doc/future.md

@@ -119,12 +119,16 @@ if (version < 24 || version > 31)  return NULL;
 if (version < 27)       header_size = sizeof (v24);
 else if (version < 29)  header_size = sizeof (v27);
 else                    header_size = sizeof (v29);   /* 29, 30, 31 */
+/* After normalizing header fields, reject v24.0 via image-stride probe. */
+if (version == 24 && is_v24_0 (meta))  return NULL;
 ```
 
 | Wire version | Status                            | Reality                                                                                    |
 |--------------|-----------------------------------|--------------------------------------------------------------------------------------------|
 | 16, 19, 20   | Rejected                          | Pre-Unity-5.5 builds, effectively extinct.                                                 |
 | 21, 22, 23   | Rejected                          | Unity 5.3 – 5.5 IPAs exist but are rare.                                                   |
+| 24.0         | Rejected after sub-version probe  | On-disk `version` is 24 for both v24.0 and v24.1+. The parser probes image-row stride (32 B vs 40 B) and rejects v24.0 with an explicit error; TypeDefinition/MethodDefinition/ImageDefinition rows would otherwise decode at wrong offsets. |
+| 24.1 – 24.5  | Accepted via `_v24` header struct | Row decoders target the v24.1+ strides.                                                    |
 | 27           | Accepted via `_v27` header struct | Header correct. Row decoders still assume the v24.1+ layout; v27.2 RGCTX widening not handled (only affects RGCTX which is unused). |
 | 29           | Accepted via `_v29` header struct | Header correct. Method rows decoded as 32 B. Reverse-P/Invoke BLOB path is the only v29-specific code. |
 | 30           | Accepted                          | Never shipped on disk; dead slot, safe.                                                    |

doc/r2unity.md

@@ -917,9 +917,13 @@ Unity-release → wire-version → sub-version mapping.
 	`Il2CppMethodDefinition`, aligning with ECMA-335's return-value
 	param-row model.
 
-r2unity's current acceptance band is **v24..v31**, with dedicated
+r2unity's current acceptance band is **v24.1..v31**, with dedicated
 handling only for the v24.1+ table strides and the v31
-`returnParameterToken` insertion.
+`returnParameterToken` insertion. Since the on-disk `version` field is
+`24` for both v24.0 and v24.1+, the parser probes the image-row stride
+(32 B on v24.0, 40 B on v24.1+) and rejects v24.0 explicitly to avoid
+silent mis-decoding of TypeDefinition/MethodDefinition/ImageDefinition
+rows.
 
 ## 5. How the parser is wired in r2unity
 

src/lib/lib.c

@@ -14,6 +14,43 @@ R_API bool r2unity_is_debug (void) {
 }
 
 
+/* Detect v24.0 vs v24.1+ (both land on disk as version==24).
+ *
+ * At v24.1 the ImageDefinition row grew by 8 bytes (added
+ * customAttributeStart/Count), so imagesSize is a multiple of 40 on v24.1+
+ * and 32 on v24.0. When imagesSize is divisible by both (a multiple of 160),
+ * probe the 4 bytes at offset 40: under v24.1+ that is row 1's nameIndex
+ * (a valid string-pool offset); under v24.0 it is mid-row.
+ *
+ * Fixing row layouts for v24.0 (larger TypeDefinition, MethodDefinition,
+ * ImageDefinition) is tracked separately; reject for now so decoders don't
+ * silently return wrong offsets. */
+static bool is_v24_0 (R2UnityMetadata *meta) {
+	ut64 ioff = meta->header.v24.imagesOffset;
+	ut64 isize = meta->header.v24.imagesSize;
+	if (!isize) {
+		return false;
+	}
+	bool div40 = (isize % 40) == 0;
+	bool div32 = (isize % 32) == 0;
+	if (div40 && !div32) {
+		return false;
+	}
+	if (div32 && !div40) {
+		return true;
+	}
+	if (isize >= 44) {
+		ut8 probe[4];
+		if (r_buf_read_at (meta->buf, ioff + 40, probe, 4) == 4) {
+			uint32_t name_idx = r_read_le32 (probe);
+			if (name_idx < (uint32_t) meta->stringSize) {
+				return false;
+			}
+		}
+	}
+	return true;
+}
+
 R_API R2UnityMetadata *r2unity_parse_metadata (RBuffer *buf) {
 	if (!buf) {
 		return NULL;
@@ -97,6 +134,13 @@ R_API R2UnityMetadata *r2unity_parse_metadata (RBuffer *buf) {
 		meta->typeDefinitionsOffset = meta->header.v29.typeDefinitionsOffset;
 		meta->typeDefinitionsSize = meta->header.v29.typeDefinitionsSize;
 	}
+	if (meta->version == 24 && is_v24_0 (meta)) {
+		R_LOG_ERROR ("v24.0 metadata (Unity 5.6..2018.2) not supported: "
+			"TypeDefinition/MethodDefinition/ImageDefinition row layouts "
+			"differ from v24.1+ and would silently decode wrong offsets");
+		r2unity_free_metadata (meta);
+		return NULL;
+	}
 	meta->strings = r_buf_new_slice (buf, meta->stringOffset, meta->stringSize);
 	meta->string_literals = r_buf_new_slice (buf, meta->stringLiteralOffset, meta->stringLiteralSize);
 	if (g_debug) {