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/*
* RDRAND RNG
* (C) 2016,2019 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/rdrand_rng.h>
#include <botan/loadstor.h>
#include <botan/cpuid.h>
#if !defined(BOTAN_USE_GCC_INLINE_ASM)
#include <immintrin.h>
#endif
namespace Botan {
namespace {
#if defined(BOTAN_TARGET_ARCH_IS_X86_64)
typedef uint64_t rdrand_output;
#else
typedef uint32_t rdrand_output;
#endif
#if !defined(BOTAN_USE_GCC_INLINE_ASM)
BOTAN_FUNC_ISA("rdrnd")
#endif
rdrand_output read_rdrand()
{
/*
* According to Intel, RDRAND is guaranteed to generate a random
* number within 10 retries on a working CPU
*/
const size_t RDRAND_RETRIES = 10;
for(size_t i = 0; i < RDRAND_RETRIES; ++i)
{
rdrand_output r = 0;
int cf = 0;
#if defined(BOTAN_USE_GCC_INLINE_ASM)
// same asm seq works for 32 and 64 bit
asm("rdrand %0; adcl $0,%1" :
"=r" (r), "=r" (cf) : "0" (r), "1" (cf) : "cc");
#elif defined(BOTAN_TARGET_ARCH_IS_X86_64)
cf = _rdrand64_step(&r);
#else
cf = _rdrand32_step(&r);
#endif
if(1 == cf)
{
return r;
}
}
throw PRNG_Unseeded("RDRAND read failed");
}
}
void RDRAND_RNG::randomize(uint8_t out[], size_t out_len)
{
while(out_len >= sizeof(rdrand_output))
{
const rdrand_output r = read_rdrand();
store_le(r, out);
out += sizeof(rdrand_output);
out_len -= sizeof(rdrand_output);
}
if(out_len > 0) // at most sizeof(rdrand_output)-1
{
const rdrand_output r = read_rdrand();
for(size_t i = 0; i != out_len; ++i)
out[i] = get_byte(i, r);
}
}
RDRAND_RNG::RDRAND_RNG()
{
if(!RDRAND_RNG::available())
throw Invalid_State("Current CPU does not support RDRAND instruction");
}
//static
bool RDRAND_RNG::available()
{
return CPUID::has_rdrand();
}
//static
uint32_t RDRAND_RNG::rdrand()
{
return static_cast<uint32_t>(read_rdrand());
}
//static
BOTAN_FUNC_ISA("rdrnd")
uint32_t RDRAND_RNG::rdrand_status(bool& ok)
{
ok = false;
try
{
const uint32_t r = static_cast<uint32_t>(read_rdrand());
ok = true;
return r;
}
catch(PRNG_Unseeded&) {}
return 0;
}
}
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