Botan
1.11.15
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#include <rdrand.h>
Public Member Functions | |
std::string | name () const |
void | poll (Entropy_Accumulator &accum) |
Static Public Member Functions | |
static void | poll_available_sources (class Entropy_Accumulator &accum) |
Entropy source using the rdrand instruction first introduced on Intel's Ivy Bridge architecture.
std::string Botan::Intel_Rdrand::name | ( | ) | const [inline, virtual] |
Implements Botan::EntropySource.
Definition at line 22 of file rdrand.h.
{ return "Intel Rdrand"; }
void Botan::Intel_Rdrand::poll | ( | Entropy_Accumulator & | accum | ) | [virtual] |
Perform an entropy gathering poll
accum | is an accumulator object that will be given entropy |
Implements Botan::EntropySource.
Definition at line 20 of file rdrand.cpp.
References Botan::Entropy_Accumulator::add(), and Botan::CPUID::has_rdrand().
{ if(!CPUID::has_rdrand()) return; /* * Put an upper bound on the total entropy we're willing to claim * for any one polling of rdrand to prevent it from swamping our * poll. Internally, the rdrand system is a DRGB that reseeds at a * somewhat unpredictable rate (the current conditions are * documented, but that might not be true for different * implementations, eg on Haswell or a future AMD chip, so I don't * want to assume). This limit ensures we're going to poll at least * one other source so we have some diversity in our inputs. */ const size_t POLL_UPPER_BOUND = 96; const size_t RDRAND_POLLS = 32; const double ENTROPY_PER_POLL = static_cast<double>(POLL_UPPER_BOUND) / (RDRAND_POLLS * 4); for(size_t i = 0; i != RDRAND_POLLS; ++i) { unsigned int r = 0; #if BOTAN_USE_GCC_INLINE_ASM int cf = 0; // Encoding of rdrand %eax asm(".byte 0x0F, 0xC7, 0xF0; adcl $0,%1" : "=a" (r), "=r" (cf) : "0" (r), "1" (cf) : "cc"); #else int cf = _rdrand32_step(&r); #endif if(cf == 1) accum.add(r, ENTROPY_PER_POLL); } }
void Botan::EntropySource::poll_available_sources | ( | class Entropy_Accumulator & | accum | ) | [static, inherited] |
Definition at line 108 of file entropy_srcs.cpp.
References Botan::Entropy_Accumulator::polling_goal_achieved().
Referenced by Botan::HMAC_RNG::reseed().
{ static std::vector<std::unique_ptr<EntropySource>> g_sources(get_default_entropy_sources()); if(g_sources.empty()) throw std::runtime_error("No entropy sources enabled at build time, poll failed"); size_t poll_attempt = 0; while(!accum.polling_goal_achieved() && poll_attempt < 16) { const size_t src_idx = poll_attempt % g_sources.size(); g_sources[src_idx]->poll(accum); ++poll_attempt; } }