Safe uid generation

wled00/util.cpp

@@ -1159,60 +1159,61 @@ String computeSHA1(const String& input) {
 }
 
 #ifdef ESP32
-static String dump_raw_block(esp_efuse_block_t block)
-{
-  const int WORDS = 8; // ESP32: 8×32-bit words per block i.e. 256bits
-  uint32_t buf[WORDS] = {0};
-
-  const esp_efuse_desc_t d = {
-    .efuse_block = block,
-    .bit_start = 0,
-    .bit_count = WORDS * 32
-  };
-  const esp_efuse_desc_t* field[2] = { &d, NULL };
-
-  esp_err_t err = esp_efuse_read_field_blob(field, buf, WORDS * 32);
-  if (err != ESP_OK) {
-    return "";
+#include "esp_adc_cal.h"
+String generateDeviceFingerprint() {
+  uint32_t fp[2]; // create 64 bit fingerprint
+  esp_chip_info_t chip_info;
+  esp_chip_info(&chip_info);
+  esp_efuse_mac_get_default((uint8_t*)fp);
+  fp[1] ^= ESP.getFlashChipSize();
+  fp[0] ^= chip_info.full_revision | (chip_info.model << 16);
+  // mix in ADC calibration data:
+  esp_adc_cal_characteristics_t ch;
+  #if SOC_ADC_MAX_BITWIDTH == 13 // S2 has 13 bit ADC
+  #define BIT_WIDTH ADC_WIDTH_BIT_13
+  #else
+  #define BIT_WIDTH ADC_WIDTH_BIT_12
+  #endif
+  esp_adc_cal_characterize(ADC_UNIT_1, ADC_ATTEN_DB_11, BIT_WIDTH, 1100, &ch);
+  fp[0] ^= ch.coeff_a;
+  fp[1] ^= ch.coeff_b;
+  if (ch.low_curve) {
+    for (int i = 0; i < 8; i++) {
+      fp[0] ^= ch.low_curve[i];
+    }
   }
-
-  String result = "";
-  for (const unsigned int i : buf) {
-    char line[32];
-    sprintf(line, "0x%08X", i);
-    result += line;
+  if (ch.high_curve) {
+    for (int i = 0; i < 8; i++) {
+      fp[1] ^= ch.high_curve[i];
+    }
   }
-  return result;
+  char fp_string[17];  // 16 hex chars + null terminator
+  sprintf(fp_string, "%08X%08X", fp[1], fp[0]);
+  return String(fp_string);
+}
+#else // ESP8266
+String generateDeviceFingerprint() {
+  static uint32_t fp[2]; // create 64 bit fingerprint
+  WiFi.macAddress((uint8_t*)&fp); // use MAC address as fingerprint base
+  fp[0] ^= ESP.getFlashChipId();
+  fp[1] ^= ESP.getFlashChipSize() | ESP.getFlashChipVendorId() << 16;
+  char fp_string[17];  // 16 hex chars + null terminator
+  sprintf(fp_string, "%08X%08X", fp[1], fp[0]);
+  return String(fp_string);
 }
 #endif
 
-
-// Generate a device ID based on SHA1 hash of MAC address salted with "WLED"
+// Generate a device ID based on SHA1 hash of MAC address salted with other unique device info
 // Returns: original SHA1 + last 2 chars of double-hashed SHA1 (42 chars total)
 String getDeviceId() {
   static String cachedDeviceId = "";
-  if (cachedDeviceId.length() > 0) return cachedDeviceId;
-
-  uint8_t mac[6];
-  WiFi.macAddress(mac);
-  char macStr[18];
-  sprintf(macStr, "%02x:%02x:%02x:%02x:%02x:%02x", mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
-
   // The device string is deterministic as it needs to be consistent for the same device, even after a full flash erase
   // MAC is salted with other consistent device info to avoid rainbow table attacks.
   // If the MAC address is known by malicious actors, they could precompute SHA1 hashes to impersonate devices,
   // but as WLED developers are just looking at statistics and not authenticating devices, this is acceptable.
   // If the usage data was exfiltrated, you could not easily determine the MAC from the device ID without brute forcing SHA1
-#ifdef ESP8266
-  String deviceString = String(macStr) + "WLED" + ESP.getFlashChipId();
-#else
-  String deviceString = String(macStr) + "WLED" + ESP.getChipModel() + ESP.getChipRevision();
-  deviceString += dump_raw_block(EFUSE_BLK0);
-  deviceString += dump_raw_block(EFUSE_BLK1);
-  deviceString += dump_raw_block(EFUSE_BLK2);
-  deviceString += dump_raw_block(EFUSE_BLK3);
-#endif
-  String firstHash = computeSHA1(deviceString);
+
+  String firstHash = computeSHA1(generateDeviceFingerprint());
 
   // Second hash: SHA1 of the first hash
   String secondHash = computeSHA1(firstHash);