padlkrng.cpp

// via-rng.cpp - written and placed in public domain by Jeffrey Walton and Uri Blumenthal.

#include "pch.h"
#include "config.h"
#include "cryptlib.h"
#include "secblock.h"
#include "padlkrng.h"
#include "cpu.h"

// The Padlock Security Engine RNG has a few items to be aware of. You can
// find copies  of the Programmer's manual, Cryptography Research Inc audit
// report, and other goodies at http://www.cryptopp.com/wiki/VIA_Padlock.

#if CRYPTOPP_MSC_VERSION
# pragma warning(disable: 4702)
#endif

NAMESPACE_BEGIN(CryptoPP)

std::string PadlockRNG::AlgorithmProvider() const
{
    return "Padlock";
}

PadlockRNG::PadlockRNG(word32 divisor)
    : m_divisor(DivisorHelper(divisor)), m_msr(0)
{
#if defined(CRYPTOPP_X86_ASM_AVAILABLE)
    if (!HasPadlockRNG())
#endif
        throw PadlockRNG_Err("PadlockRNG", "PadlockRNG generator not available");
}

void PadlockRNG::GenerateBlock(byte *output, size_t size)
{
    CRYPTOPP_UNUSED(output); CRYPTOPP_UNUSED(size);
#if defined(CRYPTOPP_X86_ASM_AVAILABLE) && defined(__GNUC__)
    while (size)
    {
        __asm__ __volatile__
        (
#if (CRYPTOPP_BOOL_X32 || CRYPTOPP_BOOL_X64)
            "mov  %1, %%rdi          ;\n"
            "movl %2, %%edx          ;\n"
#else
            "mov  %1, %%edi          ;\n"
            "movl %2, %%edx          ;\n"
#endif

            ".byte 0x0f, 0xa7, 0xc0  ;\n"
            "movl %%eax, %0          ;\n"

            : "=g" (m_msr) : "g" (m_buffer.data()), "g" (m_divisor)
#if (CRYPTOPP_BOOL_X32 || CRYPTOPP_BOOL_X64)
            : "rax", "rdx", "rdi", "cc"
#else
            : "eax", "edx", "edi", "cc"
#endif
        );

        const size_t ret = m_msr & 0x1f;
        const size_t rem = STDMIN<size_t>(ret, STDMIN<size_t>(size, 16U /*buffer size*/));
        std::memcpy(output, m_buffer, rem);
        size -= rem; output += rem;
    }
#elif defined(CRYPTOPP_X86_ASM_AVAILABLE) && defined(_MSC_VER) && defined(_M_IX86)
    while (size)
    {
        word32 result, divisor = m_divisor;
        byte *buffer = reinterpret_cast<byte*>(m_buffer.data());
        __asm {
            mov edi, buffer
            mov edx, divisor
            _emit 0x0f
            _emit 0xa7
            _emit 0xc0
            mov result, eax
        }

        const size_t ret = (m_msr = result) & 0x1f;
        const size_t rem = STDMIN<size_t>(ret, STDMIN<size_t>(size, 16U /*buffer size*/));
        std::memcpy(output, buffer, rem);
        size -= rem; output += rem;
    }
#else
    throw PadlockRNG_Err("GenerateBlock", "PadlockRNG generator not available");
#endif  // CRYPTOPP_X86_ASM_AVAILABLE
}

void PadlockRNG::DiscardBytes(size_t n)
{
    FixedSizeSecBlock<word32, 4> discard;
    n = RoundUpToMultipleOf(n, sizeof(word32));

    size_t count = STDMIN(n, discard.SizeInBytes());
    while (count)
    {
        GenerateBlock(discard.BytePtr(), count);
        n -= count;
        count = STDMIN(n, discard.SizeInBytes());
    }
}

NAMESPACE_END