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139 lines
5.5 KiB
139 lines
5.5 KiB
![]()
4 years ago
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// via-rng.h - written and placed in public domain by Jeffrey Walton
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/// \file padlkrng.h
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/// \brief Classes for VIA Padlock RNG
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/// \since Crypto++ 6.0
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/// \sa <A HREF="http://www.cryptopp.com/wiki/VIA_Padlock">VIA
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/// Padlock</A> on the Crypto++ wiki
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#ifndef CRYPTOPP_PADLOCK_RNG_H
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#define CRYPTOPP_PADLOCK_RNG_H
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#include "cryptlib.h"
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#include "secblock.h"
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NAMESPACE_BEGIN(CryptoPP)
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/// \brief Exception thrown when a PadlockRNG generator encounters
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/// a generator related error.
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/// \since Crypto++ 6.0
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class PadlockRNG_Err : public Exception
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{
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public:
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PadlockRNG_Err(const std::string &operation)
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: Exception(OTHER_ERROR, "PadlockRNG: " + operation + " operation failed") {}
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PadlockRNG_Err(const std::string &component, const std::string &message)
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: Exception(OTHER_ERROR, component + ": " + message) {}
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};
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/// \brief Hardware generated random numbers using VIA XSTORE
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/// \details Some VIA processors provide a Security Engine called Padlock. The Padlock
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/// Security Engine provides AES, SHA and a RNG. The PadlockRNG class provides access
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/// to the RNG.
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/// \details The VIA generator uses an 8 byte FIFO buffer for random numbers. The
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/// generator can be configured to discard bits from the buffer to resist analysis.
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/// The <tt>divisor</tt> controls the number of bytes discarded. The formula for
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/// the discard amount is <tt>2**divisor - 1</tt>. When <tt>divisor=0</tt> no bits
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/// are discarded and the entire 8 byte buffer is read. If <tt>divisor=3</tt> then
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/// 7 bytes are discarded and 1 byte is read. TheVIA SDK samples use <tt>divisor=1</tt>.
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/// \details Cryptography Research, Inc (CRI) audited the Padlock Security Engine
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/// in 2003. CRI provided recommendations to operate the generator for secure and
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/// non-secure applications. Additionally, the Programmers Guide and SDK provided a
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/// different configuration in the sample code.
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/// \details You can operate the generator according to CRI recommendations by setting
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/// <tt>divisor</tt>, reading one word (or partial word) at a time from the FIFO, and
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/// then inspecting the MSR after each read.
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/// \details The audit report with recommendations is available on the Crypto++ wiki
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/// at <A HREF="http://www.cryptopp.com/wiki/VIA_Padlock">VIA Padlock</A>.
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/// \sa MaurerRandomnessTest() for random bit generators
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/// \since Crypto++ 6.0
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class PadlockRNG : public RandomNumberGenerator
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{
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public:
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CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() { return "PadlockRNG"; }
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virtual ~PadlockRNG() {}
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/// \brief Construct a PadlockRNG generator
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/// \param divisor the XSTORE divisor
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/// \details Some VIA processors provide a Security Engine called Padlock. The Padlock
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/// Security Engine provides AES, SHA and a RNG. The PadlockRNG class provides access
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/// to the RNG.
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/// \details The VIA generator uses an 8 byte FIFO buffer for random numbers. The
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/// generator can be configured to discard bits from the buffer to resist analysis.
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/// The <tt>divisor</tt> controls the number of bytes discarded. The formula for
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/// the discard amount is <tt>2**divisor - 1</tt>. When <tt>divisor=0</tt> no bits
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/// are discarded and the entire 8 byte buffer is read. If <tt>divisor=3</tt> then
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/// 7 bytes are discarded and 1 byte is read. VIA SDK samples use <tt>divisor=1</tt>.
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/// \details Cryptography Research, Inc (CRI) audited the Padlock Security Engine
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/// in 2003. CRI provided recommendations to operate the generator for secure and
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/// non-secure applications. Additionally, the Programmers SDK provided a different
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/// configuration in the sample code.
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/// \details The audit report with recommendations is available on the Crypto++ wiki
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/// at <A HREF="http://www.cryptopp.com/wiki/VIA_Padlock">VIA Padlock</A>.
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/// \sa SetDivisor, GetDivisor
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PadlockRNG(word32 divisor=1);
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/// \brief Generate random array of bytes
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/// \param output the byte buffer
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/// \param size the length of the buffer, in bytes
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virtual void GenerateBlock(byte *output, size_t size);
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/// \brief Generate and discard n bytes
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/// \param n the number of bytes to generate and discard
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/// \details the Padlock generator discards words, not bytes. If n is
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/// not a multiple of a 32-bit word, then it is rounded up to
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/// that size.
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virtual void DiscardBytes(size_t n);
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/// \brief Update RNG state with additional unpredictable values
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/// \param input unused
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/// \param length unused
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/// \details The operation is a nop for this generator.
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virtual void IncorporateEntropy(const byte *input, size_t length)
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{
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// Override to avoid the base class' throw.
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CRYPTOPP_UNUSED(input); CRYPTOPP_UNUSED(length);
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}
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std::string AlgorithmProvider() const;
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/// \brief Set the XSTORE divisor
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/// \param divisor the XSTORE divisor
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/// \returns the old XSTORE divisor
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word32 SetDivisor(word32 divisor)
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{
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word32 old = m_divisor;
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m_divisor = DivisorHelper(divisor);
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return old;
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}
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/// \brief Get the XSTORE divisor
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/// \returns the current XSTORE divisor
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word32 GetDivisor() const
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{
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return m_divisor;
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}
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/// \brief Get the MSR for the last operation
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/// \returns the MSR for the last read operation
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word32 GetMSR() const
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{
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return m_msr;
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}
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protected:
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inline word32 DivisorHelper(word32 divisor)
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{
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return divisor > 3 ? 3 : divisor;
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}
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private:
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FixedSizeAlignedSecBlock<word32, 4, true> m_buffer;
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word32 m_divisor, m_msr;
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};
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NAMESPACE_END
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#endif // CRYPTOPP_PADLOCK_RNG_H
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