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https://github.com/zephyrproject-rtos/zephyr
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db6ff4da60
The random number generator from ESP32 uses noise from Wi-Fi and Bluetooth radios. If these are off, a pseudo-random number is generated instead; this is currently the case, but even though it's a black box, it's arguably better than returning a timestamp as a pseudo-random number generator. According to the ESP32 Technical Reference manual, the RNG passed the Dieharder Random Number Test suite (version 3.31.1)[1], but nothing has been said about the quality of the PRNG. The RNG register is read directly; no effort is made to use its contents to feed an entropy pool in a way that's similar to /dev/random on POSIX systems, as no such subsystem exists on Zephyr at the moment. [1] http://webhome.phy.duke.edu/~rgb/General/dieharder.php Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
65 lines
1.5 KiB
C
65 lines
1.5 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <string.h>
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#include <random.h>
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static inline u32_t random_esp32_get_u32(void)
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{
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/* The documentation specifies the random number generator at the
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* following address, which is at odds with the SDK, that specifies
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* it at 0x60035144. The fact that they're 0x200c0000 bytes apart
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* (lower 16 bits are the same) suggests this might be the same
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* register, just mirrored somewhere else in the address space.
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* Confirmation is required.
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*/
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volatile u32_t *rng_data_reg = (u32_t *)0x3ff75144;
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/* Read just once. This is not optimal as the generator has
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* limited throughput due to scarce sources of entropy, specially
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* with the radios turned off. Might want to revisit this.
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*/
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return *rng_data_reg;
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}
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static int random_esp32_get_entropy(struct device *device, u8_t *buf, u16_t len)
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{
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while (len) {
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u32_t v = random_esp32_get_u32();
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if (len >= sizeof(v)) {
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memcpy(buf, &v, sizeof(v));
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buf += sizeof(v);
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len -= sizeof(v);
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} else {
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memcpy(buf, &v, len);
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break;
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}
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}
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return 0;
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}
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static int random_esp32_init(struct device *device)
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{
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return 0;
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}
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static struct random_driver_api random_esp32_api_funcs = {
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.get_entropy = random_esp32_get_entropy
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};
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DEVICE_AND_API_INIT(random_esp32, CONFIG_RANDOM_NAME,
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random_esp32_init, NULL, NULL,
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PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
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&random_esp32_api_funcs);
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u32_t sys_rand32_get(void)
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{
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return random_esp32_get_u32();
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}
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