Secure Boot & Flash encryption: Support 3/4 Coding Scheme

Includes esptool update to v2.6-beta1

components/bootloader_support/src/efuse.c

@@ -13,6 +13,8 @@
 // limitations under the License.
 #include "esp_efuse.h"
 #include "esp_log.h"
+#include <string.h>
+#include "bootloader_random.h"
 
 #define EFUSE_CONF_WRITE 0x5A5A /* efuse_pgm_op_ena, force no rd/wr disable */
 #define EFUSE_CONF_READ 0x5AA5 /* efuse_read_op_ena, release force */
@@ -58,3 +60,55 @@ void esp_efuse_disable_basic_rom_console(void)
         esp_efuse_burn_new_values();
     }
 }
+
+esp_err_t esp_efuse_apply_34_encoding(const uint8_t *in_bytes, uint32_t *out_words, size_t in_bytes_len)
+{
+    if (in_bytes == NULL || out_words == NULL || in_bytes_len % 6 != 0) {
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    while (in_bytes_len > 0) {
+        uint8_t out[8];
+        uint8_t xor = 0;
+        uint8_t mul = 0;
+        for (int i = 0; i < 6; i++) {
+            xor ^= in_bytes[i];
+            mul += (i + 1) * __builtin_popcount(in_bytes[i]);
+        }
+
+        memcpy(out, in_bytes, 6); // Data bytes
+        out[6] = xor;
+        out[7] = mul;
+
+        memcpy(out_words, out, 8);
+
+        in_bytes_len -= 6;
+        in_bytes += 6;
+        out_words += 2;
+    }
+
+    return ESP_OK;
+}
+
+void esp_efuse_write_random_key(uint32_t blk_wdata0_reg)
+{
+    uint32_t buf[8];
+    uint8_t raw[24];
+    uint32_t coding_scheme = REG_READ(EFUSE_BLK0_RDATA6_REG) & EFUSE_CODING_SCHEME_M;
+
+    if (coding_scheme == EFUSE_CODING_SCHEME_VAL_NONE) {
+        bootloader_fill_random(buf, sizeof(buf));
+    } else { // 3/4 Coding Scheme
+        bootloader_fill_random(raw, sizeof(raw));
+        esp_err_t r = esp_efuse_apply_34_encoding(raw, buf, sizeof(raw));
+        assert(r == ESP_OK);
+    }
+
+    ESP_LOGV(TAG, "Writing random values to address 0x%08x", blk_wdata0_reg);
+    for (int i = 0; i < 8; i++) {
+        ESP_LOGV(TAG, "EFUSE_BLKx_WDATA%d_REG = 0x%08x", i, buf[i]);
+        REG_WRITE(blk_wdata0_reg + 4*i, buf[i]);
+    }
+    bzero(buf, sizeof(buf));
+    bzero(raw, sizeof(raw));
+}