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esp32: Add esp_fill_random() function

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Convenience function to fill a buffer with random bytes.

Add some unit tests (only sanity checks, really.)
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Angus Gratton
2018-08-15 18:20:16 +10:00
committed by bot
parent 767ec27350
commit 83a179abb0
12 changed files with 124 additions and 71 deletions
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23
components/esp32/include/esp_system.h
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@@ -151,18 +151,31 @@ uint32_t esp_get_minimum_free_heap_size( void );
/**
* @brief Get one random 32-bit word from hardware RNG
*
* The hardware RNG is fully functional whenever an RF subsystem is running (ie Bluetooth or WiFi is enabled). For secure
* The hardware RNG is fully functional whenever an RF subsystem is running (ie Bluetooth or WiFi is enabled). For
* random values, call this function after WiFi or Bluetooth are started.
*
* When the app is running without an RF subsystem enabled, it should be considered a PRNG. To help improve this
* situation, the RNG is pre-seeded with entropy while the IDF bootloader is running. However no new entropy is
* available during the window of time between when the bootloader exits and an RF subsystem starts. It may be possible
* to discern a non-random pattern in a very large amount of output captured during this window of time.
* If the RF subsystem is not used by the program, the function bootloader_random_enable() can be called to enable an
* entropy source. bootloader_random_disable() must be called before RF subsystem or I2S peripheral are used. See these functions'
* documentation for more details.
*
* Any time the app is running without an RF subsystem (or bootloader_random) enabled, RNG hardware should be
* considered a PRNG. A very small amount of entropy is available due to pre-seeding while the IDF
* bootloader is running, but this should not be relied upon for any use.
*
* @return Random value between 0 and UINT32_MAX
*/
uint32_t esp_random(void);
/**
* @brief Fill a buffer with random bytes from hardware RNG
*
* @note This function has the same restrictions regarding available entropy as esp_random()
*
* @param buf Pointer to buffer to fill with random numbers.
* @param len Length of buffer in bytes
*/
void esp_fill_random(void *buf, size_t len);
/**
* @brief Set base MAC address with the MAC address which is stored in BLK3 of EFUSE or
* external storage e.g. flash and EEPROM.