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random: cleanup order, comments, static
This commit is contained in:
Pieter Wuille
parent
8e31cf9c9b
commit
2c91330dd6
3 changed files with 109 additions and 83 deletions
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@ -45,13 +45,23 @@
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#include <sys/auxv.h>
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#endif
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[[noreturn]] static void RandFailure()
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namespace {
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/* Number of random bytes returned by GetOSRand.
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* When changing this constant make sure to change all call sites, and make
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* sure that the underlying OS APIs for all platforms support the number.
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* (many cap out at 256 bytes).
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*/
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static const int NUM_OS_RANDOM_BYTES = 32;
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[[noreturn]] void RandFailure()
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{
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LogPrintf("Failed to read randomness, aborting\n");
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std::abort();
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}
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static inline int64_t GetPerformanceCounter() noexcept
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inline int64_t GetPerformanceCounter() noexcept
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{
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// Read the hardware time stamp counter when available.
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// See https://en.wikipedia.org/wiki/Time_Stamp_Counter for more information.
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@ -72,10 +82,10 @@ static inline int64_t GetPerformanceCounter() noexcept
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}
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#ifdef HAVE_GETCPUID
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static bool g_rdrand_supported = false;
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static bool g_rdseed_supported = false;
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static constexpr uint32_t CPUID_F1_ECX_RDRAND = 0x40000000;
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static constexpr uint32_t CPUID_F7_EBX_RDSEED = 0x00040000;
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bool g_rdrand_supported = false;
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bool g_rdseed_supported = false;
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constexpr uint32_t CPUID_F1_ECX_RDRAND = 0x40000000;
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constexpr uint32_t CPUID_F7_EBX_RDSEED = 0x00040000;
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#ifdef bit_RDRND
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static_assert(CPUID_F1_ECX_RDRAND == bit_RDRND, "Unexpected value for bit_RDRND");
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#endif
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@ -83,7 +93,7 @@ static_assert(CPUID_F1_ECX_RDRAND == bit_RDRND, "Unexpected value for bit_RDRND"
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static_assert(CPUID_F7_EBX_RDSEED == bit_RDSEED, "Unexpected value for bit_RDSEED");
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#endif
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static void InitHardwareRand()
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void InitHardwareRand()
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{
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uint32_t eax, ebx, ecx, edx;
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GetCPUID(1, 0, eax, ebx, ecx, edx);
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@ -96,7 +106,7 @@ static void InitHardwareRand()
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}
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}
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static void ReportHardwareRand()
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void ReportHardwareRand()
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{
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// This must be done in a separate function, as InitHardwareRand() may be indirectly called
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// from global constructors, before logging is initialized.
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@ -112,7 +122,7 @@ static void ReportHardwareRand()
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*
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* Must only be called when RdRand is supported.
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*/
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static uint64_t GetRdRand() noexcept
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uint64_t GetRdRand() noexcept
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{
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// RdRand may very rarely fail. Invoke it up to 10 times in a loop to reduce this risk.
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#ifdef __i386__
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@ -147,7 +157,7 @@ static uint64_t GetRdRand() noexcept
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*
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* Must only be called when RdSeed is supported.
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*/
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static uint64_t GetRdSeed() noexcept
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uint64_t GetRdSeed() noexcept
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{
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// RdSeed may fail when the HW RNG is overloaded. Loop indefinitely until enough entropy is gathered,
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// but pause after every failure.
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@ -181,16 +191,16 @@ static uint64_t GetRdSeed() noexcept
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#elif defined(__aarch64__) && defined(HWCAP2_RNG)
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static bool g_rndr_supported = false;
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bool g_rndr_supported = false;
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static void InitHardwareRand()
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void InitHardwareRand()
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{
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if (getauxval(AT_HWCAP2) & HWCAP2_RNG) {
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g_rndr_supported = true;
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}
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}
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static void ReportHardwareRand()
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void ReportHardwareRand()
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{
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// This must be done in a separate function, as InitHardwareRand() may be indirectly called
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// from global constructors, before logging is initialized.
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@ -203,7 +213,7 @@ static void ReportHardwareRand()
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*
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* Must only be called when RNDR is supported.
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*/
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static uint64_t GetRNDR() noexcept
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uint64_t GetRNDR() noexcept
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{
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uint8_t ok;
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uint64_t r1;
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@ -221,7 +231,7 @@ static uint64_t GetRNDR() noexcept
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*
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* Must only be called when RNDRRS is supported.
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*/
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static uint64_t GetRNDRRS() noexcept
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uint64_t GetRNDRRS() noexcept
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{
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uint8_t ok;
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uint64_t r1;
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@ -241,12 +251,12 @@ static uint64_t GetRNDRRS() noexcept
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* Slower sources should probably be invoked separately, and/or only from
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* RandAddPeriodic (which is called once a minute).
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*/
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static void InitHardwareRand() {}
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static void ReportHardwareRand() {}
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void InitHardwareRand() {}
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void ReportHardwareRand() {}
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#endif
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/** Add 64 bits of entropy gathered from hardware to hasher. Do nothing if not supported. */
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static void SeedHardwareFast(CSHA512& hasher) noexcept {
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void SeedHardwareFast(CSHA512& hasher) noexcept {
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#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
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if (g_rdrand_supported) {
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uint64_t out = GetRdRand();
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@ -263,7 +273,7 @@ static void SeedHardwareFast(CSHA512& hasher) noexcept {
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}
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/** Add 256 bits of entropy gathered from hardware to hasher. Do nothing if not supported. */
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static void SeedHardwareSlow(CSHA512& hasher) noexcept {
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void SeedHardwareSlow(CSHA512& hasher) noexcept {
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#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
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// When we want 256 bits of entropy, prefer RdSeed over RdRand, as it's
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// guaranteed to produce independent randomness on every call.
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@ -296,7 +306,7 @@ static void SeedHardwareSlow(CSHA512& hasher) noexcept {
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}
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/** Use repeated SHA512 to strengthen the randomness in seed32, and feed into hasher. */
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static void Strengthen(const unsigned char (&seed)[32], SteadyClock::duration dur, CSHA512& hasher) noexcept
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void Strengthen(const unsigned char (&seed)[32], SteadyClock::duration dur, CSHA512& hasher) noexcept
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{
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CSHA512 inner_hasher;
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inner_hasher.Write(seed, sizeof(seed));
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@ -327,7 +337,7 @@ static void Strengthen(const unsigned char (&seed)[32], SteadyClock::duration du
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/** Fallback: get 32 bytes of system entropy from /dev/urandom. The most
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* compatible way to get cryptographic randomness on UNIX-ish platforms.
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*/
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[[maybe_unused]] static void GetDevURandom(unsigned char *ent32)
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[[maybe_unused]] void GetDevURandom(unsigned char *ent32)
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{
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int f = open("/dev/urandom", O_RDONLY);
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if (f == -1) {
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@ -402,8 +412,6 @@ void GetOSRand(unsigned char *ent32)
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#endif
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}
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namespace {
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class RNGState {
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Mutex m_mutex;
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/* The RNG state consists of 256 bits of entropy, taken from the output of
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@ -521,20 +529,19 @@ RNGState& GetRNGState() noexcept
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static std::vector<RNGState, secure_allocator<RNGState>> g_rng(1);
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return g_rng[0];
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}
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}
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/* A note on the use of noexcept in the seeding functions below:
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*
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* None of the RNG code should ever throw any exception.
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*/
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static void SeedTimestamp(CSHA512& hasher) noexcept
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void SeedTimestamp(CSHA512& hasher) noexcept
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{
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int64_t perfcounter = GetPerformanceCounter();
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hasher.Write((const unsigned char*)&perfcounter, sizeof(perfcounter));
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}
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static void SeedFast(CSHA512& hasher) noexcept
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void SeedFast(CSHA512& hasher) noexcept
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{
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unsigned char buffer[32];
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@ -549,7 +556,7 @@ static void SeedFast(CSHA512& hasher) noexcept
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SeedTimestamp(hasher);
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}
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static void SeedSlow(CSHA512& hasher, RNGState& rng) noexcept
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void SeedSlow(CSHA512& hasher, RNGState& rng) noexcept
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{
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unsigned char buffer[32];
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@ -571,7 +578,7 @@ static void SeedSlow(CSHA512& hasher, RNGState& rng) noexcept
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}
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/** Extract entropy from rng, strengthen it, and feed it into hasher. */
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static void SeedStrengthen(CSHA512& hasher, RNGState& rng, SteadyClock::duration dur) noexcept
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void SeedStrengthen(CSHA512& hasher, RNGState& rng, SteadyClock::duration dur) noexcept
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{
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// Generate 32 bytes of entropy from the RNG, and a copy of the entropy already in hasher.
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// Never use the deterministic PRNG for this, as the result is only used internally.
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@ -581,7 +588,7 @@ static void SeedStrengthen(CSHA512& hasher, RNGState& rng, SteadyClock::duration
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Strengthen(strengthen_seed, dur, hasher);
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}
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static void SeedPeriodic(CSHA512& hasher, RNGState& rng) noexcept
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void SeedPeriodic(CSHA512& hasher, RNGState& rng) noexcept
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{
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// Everything that the 'fast' seeder includes
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SeedFast(hasher);
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@ -601,7 +608,7 @@ static void SeedPeriodic(CSHA512& hasher, RNGState& rng) noexcept
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SeedStrengthen(hasher, rng, 10ms);
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}
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static void SeedStartup(CSHA512& hasher, RNGState& rng) noexcept
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void SeedStartup(CSHA512& hasher, RNGState& rng) noexcept
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{
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// Gather 256 bits of hardware randomness, if available
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SeedHardwareSlow(hasher);
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@ -627,7 +634,7 @@ enum class RNGLevel {
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PERIODIC, //!< Called by RandAddPeriodic()
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};
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static void ProcRand(unsigned char* out, int num, RNGLevel level, bool always_use_real_rng) noexcept
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void ProcRand(unsigned char* out, int num, RNGLevel level, bool always_use_real_rng) noexcept
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{
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// Make sure the RNG is initialized first (as all Seed* function possibly need hwrand to be available).
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RNGState& rng = GetRNGState();
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@ -656,6 +663,9 @@ static void ProcRand(unsigned char* out, int num, RNGLevel level, bool always_us
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}
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}
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} // namespace
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/** Internal function to set g_determinstic_rng. Only accessed from tests. */
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void MakeRandDeterministicDANGEROUS(const uint256& seed) noexcept
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{
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@ -679,13 +689,6 @@ void RandAddPeriodic() noexcept
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void RandAddEvent(const uint32_t event_info) noexcept { GetRNGState().AddEvent(event_info); }
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uint256 GetRandHash() noexcept
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{
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uint256 hash;
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GetRandBytes(hash);
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return hash;
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}
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void FastRandomContext::RandomSeed() noexcept
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{
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uint256 seed = GetRandHash();
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101
src/random.h
101
src/random.h
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@ -28,8 +28,8 @@
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* The following (classes of) functions interact with that state by mixing in new
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* entropy, and optionally extracting random output from it:
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*
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* - The GetRand*() class of functions, as well as construction of FastRandomContext objects,
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* perform 'fast' seeding, consisting of mixing in:
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* - GetRandBytes, GetRandHash, GetRandDur, as well as construction of FastRandomContext
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* objects, perform 'fast' seeding, consisting of mixing in:
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* - A stack pointer (indirectly committing to calling thread and call stack)
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* - A high-precision timestamp (rdtsc when available, c++ high_resolution_clock otherwise)
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* - 64 bits from the hardware RNG (rdrand) when available.
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@ -38,7 +38,7 @@
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* FastRandomContext on the other hand does not protect against this once created, but
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* is even faster (and acceptable to use inside tight loops).
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*
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* - The GetStrongRand*() class of function perform 'slow' seeding, including everything
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* - The GetStrongRandBytes() function performs 'slow' seeding, including everything
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* that fast seeding includes, but additionally:
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* - OS entropy (/dev/urandom, getrandom(), ...). The application will terminate if
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* this entropy source fails.
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@ -53,7 +53,7 @@
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* - Strengthen the entropy for 10 ms using repeated SHA512.
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* This is run once every minute.
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*
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* On first use of the RNG (regardless of what function is called first), all entropy
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* - On first use of the RNG (regardless of what function is called first), all entropy
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* sources used in the 'slow' seeder are included, but also:
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* - 256 bits from the hardware RNG (rdseed or rdrand) when available.
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* - Dynamic environment data (performance monitoring, ...)
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@ -71,27 +71,16 @@
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* only depends on the seed it was initialized with, possibly until it is reinitialized.
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*/
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/**
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* Generate random data via the internal PRNG.
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*
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* These functions are designed to be fast (sub microsecond), but do not necessarily
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* meaningfully add entropy to the PRNG state.
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*
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* Thread-safe.
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*/
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void GetRandBytes(Span<unsigned char> bytes) noexcept;
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uint256 GetRandHash() noexcept;
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/* ============================= INITIALIZATION AND ADDING ENTROPY ============================= */
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/**
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* Gather entropy from various sources, feed it into the internal PRNG, and
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* generate random data using it.
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* Initialize global RNG state and log any CPU features that are used.
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*
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* This function will cause failure whenever the OS RNG fails.
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*
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* Thread-safe.
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* Calling this function is optional. RNG state will be initialized when first
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* needed if it is not called.
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*/
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void GetStrongRandBytes(Span<unsigned char> bytes) noexcept;
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void RandomInit();
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/**
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* Gather entropy from various expensive sources, and feed them to the PRNG state.
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@ -108,6 +97,47 @@ void RandAddPeriodic() noexcept;
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*/
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void RandAddEvent(const uint32_t event_info) noexcept;
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/* =========================== BASE RANDOMNESS GENERATION FUNCTIONS ===========================
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*
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* All produced randomness is eventually generated by one of these functions.
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*/
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/**
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* Generate random data via the internal PRNG.
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*
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* These functions are designed to be fast (sub microsecond), but do not necessarily
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* meaningfully add entropy to the PRNG state.
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*
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* In test mode (see SeedRandomForTest in src/test/util/random.h), the normal PRNG state is
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* bypassed, and a deterministic, seeded, PRNG is used instead.
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*
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* Thread-safe.
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*/
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void GetRandBytes(Span<unsigned char> bytes) noexcept;
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/**
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* Gather entropy from various sources, feed it into the internal PRNG, and
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* generate random data using it.
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*
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* This function will cause failure whenever the OS RNG fails.
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*
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* The normal PRNG is never bypassed here, even in test mode.
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*
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* Thread-safe.
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*/
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void GetStrongRandBytes(Span<unsigned char> bytes) noexcept;
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/* ============================= RANDOM NUMBER GENERATION CLASSES =============================
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*
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* In this section, 3 classes are defined:
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* - RandomMixin: a base class that adds functionality to all RNG classes.
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* - FastRandomContext: a cryptographic RNG (seeded through GetRandBytes in its default
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* constructor).
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* - InsecureRandomContext: a non-cryptographic, very fast, RNG.
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*/
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// Forward declaration of RandomMixin, used in RandomNumberGenerator concept.
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template<typename T>
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class RandomMixin;
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@ -430,6 +460,17 @@ public:
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}
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};
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/* ==================== CONVENIENCE FUNCTIONS FOR COMMONLY USED RANDOMNESS ==================== */
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/** Generate a random uint256. */
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inline uint256 GetRandHash() noexcept
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{
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uint256 hash;
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GetRandBytes(hash);
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return hash;
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}
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/** More efficient than using std::shuffle on a FastRandomContext.
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*
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* This is more efficient as std::shuffle will consume entropy in groups of
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@ -453,29 +494,11 @@ void Shuffle(I first, I last, R&& rng)
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}
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}
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/* Number of random bytes returned by GetOSRand.
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* When changing this constant make sure to change all call sites, and make
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* sure that the underlying OS APIs for all platforms support the number.
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* (many cap out at 256 bytes).
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*/
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static const int NUM_OS_RANDOM_BYTES = 32;
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/** Get 32 bytes of system entropy. Do not use this in application code: use
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* GetStrongRandBytes instead.
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*/
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void GetOSRand(unsigned char* ent32);
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/* ============================= MISCELLANEOUS TEST-ONLY FUNCTIONS ============================= */
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/** Check that OS randomness is available and returning the requested number
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* of bytes.
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*/
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bool Random_SanityCheck();
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/**
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* Initialize global RNG state and log any CPU features that are used.
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*
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* Calling this function is optional. RNG state will be initialized when first
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* needed if it is not called.
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*/
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void RandomInit();
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#endif // BITCOIN_RANDOM_H
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@ -33,7 +33,7 @@ BOOST_AUTO_TEST_SUITE(cuckoocache_tests);
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/* Test that no values not inserted into the cache are read out of it.
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*
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* There are no repeats in the first 200000 insecure_GetRandHash calls
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* There are no repeats in the first 200000 InsecureRand256() calls
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*/
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BOOST_AUTO_TEST_CASE(test_cuckoocache_no_fakes)
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{
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