osrng.cpp

// osrng.cpp - written and placed in the public domain by Wei Dai

// Thanks to Leonard Janke for the suggestion for AutoSeededRandomPool.

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "osrng.h"

#ifdef OS_RNG_AVAILABLE

#include "rng.h"

#ifdef CRYPTOPP_WIN32_AVAILABLE
#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0400
#endif
#include <windows.h>
#include <wincrypt.h>
#endif

#ifdef CRYPTOPP_UNIX_AVAILABLE
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#endif

NAMESPACE_BEGIN(CryptoPP)

#if defined(NONBLOCKING_RNG_AVAILABLE) || defined(BLOCKING_RNG_AVAILABLE)
OS_RNG_Err::OS_RNG_Err(const std::string &operation)
        : Exception(OTHER_ERROR, "OS_Rng: " + operation + " operation failed with error " + 
#ifdef CRYPTOPP_WIN32_AVAILABLE
                "0x" + IntToString(GetLastError(), 16)
#else
                IntToString(errno)
#endif
                )
{
}
#endif

#ifdef NONBLOCKING_RNG_AVAILABLE

#ifdef CRYPTOPP_WIN32_AVAILABLE

MicrosoftCryptoProvider::MicrosoftCryptoProvider()
{
        if(!CryptAcquireContext(&m_hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
                throw OS_RNG_Err("CryptAcquireContext");
}

MicrosoftCryptoProvider::~MicrosoftCryptoProvider()
{
        CryptReleaseContext(m_hProvider, 0);
}

#endif

NonblockingRng::NonblockingRng()
{
#ifndef CRYPTOPP_WIN32_AVAILABLE
        m_fd = open("/dev/urandom",O_RDONLY);
        if (m_fd == -1)
                throw OS_RNG_Err("open /dev/urandom");
#endif
}

NonblockingRng::~NonblockingRng()
{
#ifndef CRYPTOPP_WIN32_AVAILABLE
        close(m_fd);
#endif
}

byte NonblockingRng::GenerateByte()
{
        byte b;
        GenerateBlock(&b, 1);
        return b;
}

void NonblockingRng::GenerateBlock(byte *output, size_t size)
{
#ifdef CRYPTOPP_WIN32_AVAILABLE
#       ifdef WORKAROUND_MS_BUG_Q258000
                static MicrosoftCryptoProvider m_Provider;
#       endif
        if (!CryptGenRandom(m_Provider.GetProviderHandle(), (DWORD)size, output))
                throw OS_RNG_Err("CryptGenRandom");
#else
        if (read(m_fd, output, size) != size)
                throw OS_RNG_Err("read /dev/urandom");
#endif
}

#endif

// *************************************************************

#ifdef BLOCKING_RNG_AVAILABLE

#ifndef CRYPTOPP_BLOCKING_RNG_FILENAME
#ifdef __OpenBSD__
#define CRYPTOPP_BLOCKING_RNG_FILENAME "/dev/srandom"
#else
#define CRYPTOPP_BLOCKING_RNG_FILENAME "/dev/random"
#endif
#endif

BlockingRng::BlockingRng()
{
        m_fd = open(CRYPTOPP_BLOCKING_RNG_FILENAME,O_RDONLY);
        if (m_fd == -1)
                throw OS_RNG_Err("open " CRYPTOPP_BLOCKING_RNG_FILENAME);
}

BlockingRng::~BlockingRng()
{
        close(m_fd);
}

byte BlockingRng::GenerateByte()
{
        byte b;
        GenerateBlock(&b, 1);
        return b;
}

void BlockingRng::GenerateBlock(byte *output, size_t size)
{
        while (size)
        {
                // on some systems /dev/random will block until all bytes
                // are available, on others it will returns immediately
                ssize_t len = read(m_fd, output, size);
                if (len < 0)
                        throw OS_RNG_Err("read " CRYPTOPP_BLOCKING_RNG_FILENAME);
                size -= len;
                output += len;
                if (size)
                        sleep(1);
        }
}

#endif

// *************************************************************

void OS_GenerateRandomBlock(bool blocking, byte *output, size_t size)
{
#ifdef NONBLOCKING_RNG_AVAILABLE
        if (blocking)
#endif
        {
#ifdef BLOCKING_RNG_AVAILABLE
                BlockingRng rng;
                rng.GenerateBlock(output, size);
#endif
        }

#ifdef BLOCKING_RNG_AVAILABLE
        if (!blocking)
#endif
        {
#ifdef NONBLOCKING_RNG_AVAILABLE
                NonblockingRng rng;
                rng.GenerateBlock(output, size);
#endif
        }
}

void AutoSeededRandomPool::Reseed(bool blocking, unsigned int seedSize)
{
        SecByteBlock seed(seedSize);
        OS_GenerateRandomBlock(blocking, seed, seedSize);
        Put(seed, seedSize);
}

NAMESPACE_END

#endif

#endif

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