Implement Metadata-Based OTA Release Compatibility Checking System

wled00/data/update.htm

@@ -17,7 +17,27 @@
 			}
 			window.open(getURL("/update?revert"),"_self");
 		}
-		function GetV() {/*injected values here*/}
+		function GetV() {
+			// Fetch device info via JSON API instead of compiling it in
+			fetch('/json/info')
+				.then(response => response.json())
+				.then(data => {
+					if (data.release) {
+						var releaseSpan = document.querySelector('.release-name');
+						if (releaseSpan) {
+							releaseSpan.textContent = data.release;
+						}
+					}
+				})
+				.catch(error => {
+					console.log('Could not fetch device info:', error);
+					// Fallback to compiled-in value if API call fails
+					var releaseSpan = document.querySelector('.release-name');
+					if (releaseSpan && releaseSpan.textContent === 'Loading...') {
+						releaseSpan.textContent = 'Unknown';
+					}
+				});
+		}
 	</script>
 	<style>
 		@import url("style.css");
@@ -28,10 +48,13 @@
 	<h2>WLED Software Update</h2>
 	<form method='POST' action='./update' id='upd' enctype='multipart/form-data' onsubmit="toggle('upd')">
 		Installed version: <span class="sip">WLED ##VERSION##</span><br>
+		Release: <span class="sip release-name">Loading...</span><br>
 		Download the latest binary: <a href="https://github.com/wled-dev/WLED/releases" target="_blank" 
 		style="vertical-align: text-bottom; display: inline-flex;">
 		<img src="https://img.shields.io/github/release/wled-dev/WLED.svg?style=flat-square"></a><br>
 		<input type='file' name='update' required><br> <!--should have accept='.bin', but it prevents file upload from android app-->
+		<input type='checkbox' name='skipValidation' id='skipValidation'>
+		<label for='skipValidation'>Ignore firmware validation</label><br>
 		<button type="submit">Update!</button><br>
 		<hr class="sml">
 		<button id="rev" type="button" onclick="cR()">Revert update</button><br>

wled00/ota_release_check.cpp

@@ -0,0 +1,111 @@
+#include "ota_release_check.h"
+#include "wled.h"
+
+#ifdef ESP32
+#include <esp_app_format.h>
+#include <esp_ota_ops.h>
+#endif
+
+bool extractWledCustomDesc(const uint8_t* binaryData, size_t dataSize, wled_custom_desc_t* extractedDesc) {
+    if (!binaryData || !extractedDesc || dataSize < 64) {
+        return false;
+    }
+
+    // Search in first 8KB only. This range was chosen because:
+    // - ESP32 .rodata.wled_desc sections appear early in the binary (typically within first 2-4KB)
+    // - ESP8266 .ver_number sections also appear early (typically within first 1-2KB)  
+    // - 8KB provides ample coverage for metadata discovery while minimizing processing time
+    // - Larger firmware files (>1MB) would take significantly longer to process with full search
+    // - Analysis of typical WLED binary layouts shows metadata appears well within this range
+    const size_t search_limit = min(dataSize, (size_t)8192);
+
+    for (size_t offset = 0; offset <= search_limit - sizeof(wled_custom_desc_t); offset++) {
+        const wled_custom_desc_t* custom_desc = (const wled_custom_desc_t*)(binaryData + offset);
+
+        // Check for magic number
+        if (custom_desc->magic == WLED_CUSTOM_DESC_MAGIC) {
+            // Found potential match, validate version
+            if (custom_desc->version != WLED_CUSTOM_DESC_VERSION) {
+                DEBUG_PRINTF_P(PSTR("Found WLED structure at offset %u but version mismatch: %u\n"), 
+                              offset, custom_desc->version);
+                continue;
+            }
+
+            // Validate hash using runtime function
+            uint32_t expected_hash = djb2_hash_runtime(custom_desc->release_name);
+            if (custom_desc->crc32 != expected_hash) {
+                DEBUG_PRINTF_P(PSTR("Found WLED structure at offset %u but hash mismatch\n"), offset);
+                continue;
+            }
+
+            // Valid structure found - copy entire structure
+            memcpy(extractedDesc, custom_desc, sizeof(wled_custom_desc_t));
+
+            DEBUG_PRINTF_P(PSTR("Extracted WLED structure at offset %u: '%s'\n"), 
+                          offset, extractedDesc->release_name);
+            return true;
+        }
+    }
+
+    DEBUG_PRINTLN(F("No WLED custom description found in binary"));
+    return false;
+}
+
+bool validateReleaseCompatibility(const char* extractedRelease) {
+  if (!extractedRelease) {
+    return false;
+  }
+
+  // Ensure extractedRelease is properly null terminated (guard against fixed-length buffer issues)
+  char safeRelease[WLED_RELEASE_NAME_MAX_LEN];
+  strncpy(safeRelease, extractedRelease, WLED_RELEASE_NAME_MAX_LEN - 1);
+  safeRelease[WLED_RELEASE_NAME_MAX_LEN - 1] = '\0';
+
+  if (strlen(safeRelease) == 0) {
+    return false;
+  }
+
+  // Simple string comparison - releases must match exactly
+  bool match = strcmp(releaseString, safeRelease) == 0;
+
+  DEBUG_PRINTF_P(PSTR("Release compatibility check: current='%s', uploaded='%s', match=%s\n"), 
+                 releaseString, safeRelease, match ? "YES" : "NO");
+
+  return match;
+}
+
+bool shouldAllowOTA(const uint8_t* binaryData, size_t dataSize, char* errorMessage, size_t errorMessageLen) {
+  // Clear error message
+  if (errorMessage && errorMessageLen > 0) {
+    errorMessage[0] = '\0';
+  }
+
+  // Ensure our custom description structure is referenced (prevents optimization)
+  const wled_custom_desc_t* local_desc = getWledCustomDesc();
+  (void)local_desc; // Suppress unused variable warning
+
+  // Try to extract WLED structure directly from binary data
+  wled_custom_desc_t extractedDesc;
+  bool hasCustomDesc = extractWledCustomDesc(binaryData, dataSize, &extractedDesc);
+
+  if (!hasCustomDesc) {
+    // No custom description - this could be a legacy binary
+    if (errorMessage && errorMessageLen > 0) {
+      strncpy_P(errorMessage, PSTR("This firmware file is missing compatibility metadata. Enable 'Ignore firmware validation' to proceed anyway."), errorMessageLen - 1);
+      errorMessage[errorMessageLen - 1] = '\0';
+    }
+    return false;
+  }
+
+  // Validate compatibility using extracted release name
+  if (!validateReleaseCompatibility(extractedDesc.release_name)) {
+    if (errorMessage && errorMessageLen > 0) {
+      snprintf_P(errorMessage, errorMessageLen, PSTR("Firmware compatibility mismatch: current='%s', uploaded='%s'. Enable 'Ignore firmware validation' to proceed anyway."), 
+               releaseString, extractedDesc.release_name);
+      errorMessage[errorMessageLen - 1] = '\0'; // Ensure null termination
+    }
+    return false;
+  }
+
+  return true;
+}

wled00/ota_release_check.h

@@ -0,0 +1,90 @@
+#ifndef WLED_OTA_RELEASE_CHECK_H
+#define WLED_OTA_RELEASE_CHECK_H
+
+/*
+ * OTA Release Compatibility Checking using ESP-IDF Custom Description Section
+ * Functions to extract and validate release names from uploaded binary files using embedded metadata
+ */
+
+#include <Arduino.h>
+
+#ifdef ESP32
+#include <esp_app_format.h>
+#endif
+
+#define WLED_CUSTOM_DESC_MAGIC 0x57535453  // "WSTS" (WLED System Tag Structure)
+#define WLED_CUSTOM_DESC_VERSION 1
+#define WLED_RELEASE_NAME_MAX_LEN 48
+
+// Platform-specific metadata offset in binary file
+#ifdef ESP32
+#define METADATA_OFFSET 0          // ESP32: metadata appears at beginning
+#elif defined(ESP8266)
+#define METADATA_OFFSET 0x1000     // ESP8266: metadata appears at 4KB offset
+#endif
+
+/**
+ * DJB2 hash function (C++11 compatible constexpr)
+ * Used for compile-time hash computation of release names
+ */
+constexpr uint32_t djb2_hash_constexpr(const char* str, uint32_t hash = 5381) {
+    return (*str == '\0') ? hash : djb2_hash_constexpr(str + 1, ((hash << 5) + hash) + *str);
+}
+
+/**
+ * Runtime DJB2 hash function for validation
+ */
+inline uint32_t djb2_hash_runtime(const char* str) {
+    uint32_t hash = 5381;
+    while (*str) {
+        hash = ((hash << 5) + hash) + *str++;
+    }
+    return hash;
+}
+
+/**
+ * WLED Custom Description Structure
+ * This structure is embedded in platform-specific sections at a fixed offset
+ * in ESP32/ESP8266 binaries, allowing extraction without modifying the binary format
+ */
+typedef struct {
+    uint32_t magic;               // Magic number to identify WLED custom description
+    uint32_t version;             // Structure version for future compatibility
+    char release_name[WLED_RELEASE_NAME_MAX_LEN]; // Release name (null-terminated)
+    uint32_t crc32;              // CRC32 of the above fields for integrity check
+} __attribute__((packed)) wled_custom_desc_t;
+
+/**
+ * Extract WLED custom description structure from binary
+ * @param binaryData Pointer to binary file data
+ * @param dataSize Size of binary data in bytes
+ * @param extractedDesc Buffer to store extracted custom description structure
+ * @return true if structure was found and extracted, false otherwise
+ */
+bool extractWledCustomDesc(const uint8_t* binaryData, size_t dataSize, wled_custom_desc_t* extractedDesc);
+
+/**
+ * Validate if extracted release name matches current release
+ * @param extractedRelease Release name from uploaded binary
+ * @return true if releases match (OTA should proceed), false if they don't match
+ */
+bool validateReleaseCompatibility(const char* extractedRelease);
+
+/**
+ * Check if OTA should be allowed based on release compatibility using custom description
+ * @param binaryData Pointer to binary file data (not modified)
+ * @param dataSize Size of binary data in bytes
+ * @param errorMessage Buffer to store error message if validation fails 
+ * @param errorMessageLen Maximum length of error message buffer
+ * @return true if OTA should proceed, false if it should be blocked
+ */
+bool shouldAllowOTA(const uint8_t* binaryData, size_t dataSize, char* errorMessage, size_t errorMessageLen);
+
+/**
+ * Get pointer to the embedded custom description structure
+ * This ensures the structure is referenced and not optimized out
+ * @return pointer to the custom description structure
+ */
+const wled_custom_desc_t* getWledCustomDesc();
+
+#endif // WLED_OTA_RELEASE_CHECK_H

wled00/wled_custom_desc.cpp

@@ -0,0 +1,29 @@
+#include "ota_release_check.h"
+#include "wled.h"
+
+// Platform-specific section definition
+#ifdef ESP32
+#define WLED_CUSTOM_DESC_SECTION ".rodata.wled_desc"
+#elif defined(ESP8266)
+#define WLED_CUSTOM_DESC_SECTION ".ver_number"
+#endif
+
+// Single structure definition for both platforms
+const wled_custom_desc_t __attribute__((section(WLED_CUSTOM_DESC_SECTION))) wled_custom_description = {
+    WLED_CUSTOM_DESC_MAGIC,                   // magic
+    WLED_CUSTOM_DESC_VERSION,                 // version  
+    WLED_RELEASE_NAME,                        // release_name
+    djb2_hash_constexpr(WLED_RELEASE_NAME)   // crc32 - computed at compile time
+};
+
+// Compile-time validation that release name doesn't exceed maximum length
+static_assert(sizeof(WLED_RELEASE_NAME) <= WLED_RELEASE_NAME_MAX_LEN, 
+              "WLED_RELEASE_NAME exceeds maximum length of WLED_RELEASE_NAME_MAX_LEN characters");
+
+// Single reference to ensure it's not optimized away
+const wled_custom_desc_t* __attribute__((used)) wled_custom_desc_ref = &wled_custom_description;
+
+// Function to ensure the structure is referenced by code
+const wled_custom_desc_t* getWledCustomDesc() {
+    return &wled_custom_description;
+}