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| 1 | +#include "HardwareRNG.h" |
| 2 | + |
| 3 | +#include <algorithm> |
| 4 | +#include <cstring> |
| 5 | +#include <random> |
| 6 | + |
| 7 | +#include "configuration.h" |
| 8 | + |
| 9 | +#if HAS_RADIO |
| 10 | +#include "RadioLibInterface.h" |
| 11 | +#endif |
| 12 | + |
| 13 | +#if defined(ARCH_NRF52) |
| 14 | +#include <Adafruit_nRFCrypto.h> |
| 15 | +extern Adafruit_nRFCrypto nRFCrypto; |
| 16 | +#elif defined(ARCH_ESP32) |
| 17 | +#include <esp_system.h> |
| 18 | +#elif defined(ARCH_RP2040) |
| 19 | +#include <Arduino.h> |
| 20 | +#elif defined(ARCH_PORTDUINO) |
| 21 | +#include <random> |
| 22 | +#include <sys/random.h> |
| 23 | +#include <unistd.h> |
| 24 | +#endif |
| 25 | + |
| 26 | +namespace HardwareRNG |
| 27 | +{ |
| 28 | + |
| 29 | +namespace |
| 30 | +{ |
| 31 | +void fillWithRandomDevice(uint8_t *buffer, size_t length) |
| 32 | +{ |
| 33 | + std::random_device rd; |
| 34 | + size_t offset = 0; |
| 35 | + while (offset < length) { |
| 36 | + uint32_t value = rd(); |
| 37 | + size_t toCopy = std::min(length - offset, sizeof(value)); |
| 38 | + memcpy(buffer + offset, &value, toCopy); |
| 39 | + offset += toCopy; |
| 40 | + } |
| 41 | +} |
| 42 | + |
| 43 | +#if HAS_RADIO |
| 44 | +bool mixWithLoRaEntropy(uint8_t *buffer, size_t length) |
| 45 | +{ |
| 46 | + // Only attempt to pull entropy from the modem if it is initialized and exposes the helper. |
| 47 | + // When the radio stack is disabled or has not yet been configured, we simply skip this step |
| 48 | + // and return false so callers know no extra mixing occurred. |
| 49 | + RadioLibInterface *radio = RadioLibInterface::instance; |
| 50 | + if (!radio) { |
| 51 | + LOG_ERROR("No radio instance available to provide entropy"); |
| 52 | + return false; |
| 53 | + } |
| 54 | + |
| 55 | + constexpr size_t chunkSize = 16; |
| 56 | + uint8_t scratch[chunkSize]; |
| 57 | + size_t offset = 0; |
| 58 | + bool mixed = false; |
| 59 | + |
| 60 | + while (offset < length) { |
| 61 | + size_t toCopy = std::min(length - offset, chunkSize); |
| 62 | + |
| 63 | + // randomBytes() returns false if the modem does not support it or is not ready |
| 64 | + // (for instance, when the radio is powered down). We break immediately to avoid |
| 65 | + // blocking or returning partially-filled entropy and simply report failure. |
| 66 | + if (!radio->randomBytes(scratch, toCopy)) { |
| 67 | + break; |
| 68 | + } |
| 69 | + |
| 70 | + for (size_t i = 0; i < toCopy; ++i) { |
| 71 | + buffer[offset + i] ^= scratch[i]; |
| 72 | + } |
| 73 | + |
| 74 | + mixed = true; |
| 75 | + offset += toCopy; |
| 76 | + } |
| 77 | + |
| 78 | + // Avoid leaving the modem-sourced bytes sitting on the stack longer than needed. |
| 79 | + if (mixed) { |
| 80 | + memset(scratch, 0, sizeof(scratch)); |
| 81 | + } |
| 82 | + |
| 83 | + return mixed; |
| 84 | +} |
| 85 | +#endif |
| 86 | +} // namespace |
| 87 | + |
| 88 | +bool fill(uint8_t *buffer, size_t length, bool useRadioEntropy) |
| 89 | +{ |
| 90 | + if (!buffer || length == 0) { |
| 91 | + return false; |
| 92 | + } |
| 93 | + |
| 94 | + bool filled = false; |
| 95 | + |
| 96 | +#if defined(ARCH_NRF52) |
| 97 | + // The Nordic SDK RNG provides cryptographic-quality randomness backed by hardware. |
| 98 | + nRFCrypto.begin(); |
| 99 | + auto result = nRFCrypto.Random.generate(buffer, length); |
| 100 | + nRFCrypto.end(); |
| 101 | + filled = result; |
| 102 | +#elif defined(ARCH_ESP32) |
| 103 | + // ESP32 exposes a true RNG via esp_fill_random(). |
| 104 | + esp_fill_random(buffer, length); |
| 105 | + filled = true; |
| 106 | +#elif defined(ARCH_RP2040) |
| 107 | + // RP2040 has a hardware random number generator accessible through the Arduino core. |
| 108 | + size_t offset = 0; |
| 109 | + while (offset < length) { |
| 110 | + uint32_t value = rp2040.hwrand32(); |
| 111 | + size_t toCopy = std::min(length - offset, sizeof(value)); |
| 112 | + memcpy(buffer + offset, &value, toCopy); |
| 113 | + offset += toCopy; |
| 114 | + } |
| 115 | + filled = true; |
| 116 | +#elif defined(ARCH_PORTDUINO) |
| 117 | + // Prefer the host OS RNG first when running under Portduino. |
| 118 | + ssize_t generated = ::getrandom(buffer, length, 0); |
| 119 | + if (generated == static_cast<ssize_t>(length)) { |
| 120 | + filled = true; |
| 121 | + } |
| 122 | + |
| 123 | + if (!filled) { |
| 124 | + fillWithRandomDevice(buffer, length); |
| 125 | + filled = true; |
| 126 | + } |
| 127 | +#endif |
| 128 | + |
| 129 | + if (!filled) { |
| 130 | + // As a last resort, fall back to std::random_device. This should only be reached |
| 131 | + // if a platform-specific source was unavailable. |
| 132 | + fillWithRandomDevice(buffer, length); |
| 133 | + filled = true; |
| 134 | + } |
| 135 | + |
| 136 | +#if HAS_RADIO |
| 137 | + if (useRadioEntropy) { |
| 138 | + // Best-effort: if the radio is active and can provide modem entropy, XOR it over the |
| 139 | + // buffer to improve overall quality. We consider the filling a success if either a |
| 140 | + // good platform RNG or the modem RNG provided data, so we return true as long as at |
| 141 | + // least one of those steps succeeded. |
| 142 | + filled = mixWithLoRaEntropy(buffer, length) || filled; |
| 143 | + } |
| 144 | +#endif |
| 145 | + |
| 146 | + return filled; |
| 147 | +} |
| 148 | + |
| 149 | +bool seed(uint32_t &seedOut) |
| 150 | +{ |
| 151 | + uint32_t candidate = 0; |
| 152 | + if (!fill(reinterpret_cast<uint8_t *>(&candidate), sizeof(candidate), true)) { |
| 153 | + return false; |
| 154 | + } |
| 155 | + seedOut = candidate; |
| 156 | + return true; |
| 157 | +} |
| 158 | + |
| 159 | +} // namespace HardwareRNG |
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