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[esp32] Validate eFuse MAC reads and reject garbage MACs (#15049)

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This commit is contained in:
J. Nick Koston
2026-03-22 12:41:01 -10:00
committed by GitHub
parent aef987dccf
commit 84727b1f71
2 changed files with 46 additions and 11 deletions
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46
esphome/components/esp32/helpers.cpp
View File

@@ -9,11 +9,14 @@
#include <freertos/FreeRTOS.h>
#include <freertos/portmacro.h>
#include "esphome/core/log.h"
#include "esp_random.h"
#include "esp_system.h"
namespace esphome {
static const char *const TAG = "esp32";
bool random_bytes(uint8_t *data, size_t len) {
esp_fill_random(data, len);
return true;
@@ -63,22 +66,43 @@ LwIPLock::~LwIPLock() {
#endif
}
/// Read MAC and validate both the return code and content.
static bool read_valid_mac(uint8_t *mac, esp_err_t err) { return err == ESP_OK && mac_address_is_valid(mac); }
static constexpr size_t MAC_ADDRESS_SIZE_BITS = MAC_ADDRESS_SIZE * 8; // 48 bits
void get_mac_address_raw(uint8_t *mac) { // NOLINT(readability-non-const-parameter)
#if defined(CONFIG_SOC_IEEE802154_SUPPORTED)
// When CONFIG_SOC_IEEE802154_SUPPORTED is defined, esp_efuse_mac_get_default
// returns the 802.15.4 EUI-64 address, so we read directly from eFuse instead.
if (has_custom_mac_address()) {
esp_efuse_read_field_blob(ESP_EFUSE_MAC_CUSTOM, mac, 48);
} else {
esp_efuse_read_field_blob(ESP_EFUSE_MAC_FACTORY, mac, 48);
// Both paths already read raw eFuse bytes, so there is no CRC-bypass fallback
// (unlike the non-IEEE802154 path where esp_efuse_mac_get_default does CRC checks).
if (has_custom_mac_address() &&
read_valid_mac(mac, esp_efuse_read_field_blob(ESP_EFUSE_MAC_CUSTOM, mac, MAC_ADDRESS_SIZE_BITS))) {
return;
}
if (read_valid_mac(mac, esp_efuse_read_field_blob(ESP_EFUSE_MAC_FACTORY, mac, MAC_ADDRESS_SIZE_BITS))) {
return;
}
#else
if (has_custom_mac_address()) {
esp_efuse_mac_get_custom(mac);
} else {
esp_efuse_mac_get_default(mac);
if (has_custom_mac_address() && read_valid_mac(mac, esp_efuse_mac_get_custom(mac))) {
return;
}
if (read_valid_mac(mac, esp_efuse_mac_get_default(mac))) {
return;
}
// Default MAC read failed (e.g., eFuse CRC error) - try reading raw eFuse bytes
// directly, bypassing CRC validation. A MAC that passes mac_address_is_valid()
// (non-zero, non-broadcast, unicast) is almost certainly the real factory MAC
// with a corrupted CRC byte, which is far better than returning garbage or zeros.
if (read_valid_mac(mac, esp_efuse_read_field_blob(ESP_EFUSE_MAC_FACTORY, mac, MAC_ADDRESS_SIZE_BITS))) {
ESP_LOGW(TAG, "eFuse MAC CRC failed but raw bytes appear valid - using raw eFuse MAC");
return;
}
#endif
// All methods failed - zero the MAC rather than returning garbage
ESP_LOGE(TAG, "Failed to read a valid MAC address from eFuse");
memset(mac, 0, MAC_ADDRESS_SIZE);
}
void set_mac_address(uint8_t *mac) { esp_base_mac_addr_set(mac); }
@@ -88,9 +112,11 @@ bool has_custom_mac_address() {
uint8_t mac[6];
// do not use 'esp_efuse_mac_get_custom(mac)' because it drops an error in the logs whenever it fails
#ifndef USE_ESP32_VARIANT_ESP32
return (esp_efuse_read_field_blob(ESP_EFUSE_USER_DATA_MAC_CUSTOM, mac, 48) == ESP_OK) && mac_address_is_valid(mac);
return (esp_efuse_read_field_blob(ESP_EFUSE_USER_DATA_MAC_CUSTOM, mac, MAC_ADDRESS_SIZE_BITS) == ESP_OK) &&
mac_address_is_valid(mac);
#else
return (esp_efuse_read_field_blob(ESP_EFUSE_MAC_CUSTOM, mac, 48) == ESP_OK) && mac_address_is_valid(mac);
return (esp_efuse_read_field_blob(ESP_EFUSE_MAC_CUSTOM, mac, MAC_ADDRESS_SIZE_BITS) == ESP_OK) &&
mac_address_is_valid(mac);
#endif
#else
return false;

11
esphome/core/helpers.cpp
View File

@@ -863,7 +863,16 @@ bool mac_address_is_valid(const uint8_t *mac) {
is_all_ones = false;
}
}
return !(is_all_zeros || is_all_ones);
if (is_all_zeros || is_all_ones) {
return false;
}
// Reject multicast MACs (bit 0 of first byte set) - device MACs must be unicast.
// This catches garbage data from corrupted eFuse custom MAC areas, which often
// has random values that would otherwise pass the all-zeros/all-ones check.
if (mac[0] & 0x01) {
return false;
}
return true;
}
void IRAM_ATTR HOT delay_microseconds_safe(uint32_t us) {