esp-idf/components/mbedtls/port/esp_hardware.c

#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#include <sys/types.h>
#include <stdlib.h>
#include <stdio.h>
#include <esp_system.h>

#ifndef MBEDTLS_ENTROPY_HARDWARE_ALT
#error "MBEDTLS_ENTROPY_HARDWARE_ALT should always be set in ESP-IDF"
#endif

int mbedtls_hardware_poll( void *data,
                           unsigned char *output, size_t len, size_t *olen )
{
    esp_fill_random(output, len);
    *olen = len;
    return 0;
}