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/*
* System RNG
* (C) 2014,2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/system_rng.h>
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
#include <windows.h>
#include <wincrypt.h>
#undef min
#undef max
#else
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#endif
namespace Botan {
namespace {
class System_RNG_Impl : public RandomNumberGenerator
{
public:
System_RNG_Impl();
~System_RNG_Impl();
void randomize(byte buf[], size_t len) override;
bool is_seeded() const override { return true; }
void clear() override {}
std::string name() const override { return "system"; }
size_t reseed_with_sources(Entropy_Sources&,
size_t /*poll_bits*/,
std::chrono::milliseconds /*timeout*/) override
{
// We ignore it and assert the PRNG is seeded.
// TODO: could poll and write it to /dev/urandom to help seed it
return 0;
}
void add_entropy(const byte[], size_t) override
{
}
private:
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
HCRYPTPROV m_prov;
#else
int m_fd;
#endif
};
System_RNG_Impl::System_RNG_Impl()
{
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
if(!CryptAcquireContext(&m_prov, 0, 0, BOTAN_SYSTEM_RNG_CRYPTOAPI_PROV_TYPE, CRYPT_VERIFYCONTEXT))
throw std::runtime_error("System_RNG failed to acquire crypto provider");
#else
#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif
m_fd = ::open(BOTAN_SYSTEM_RNG_DEVICE, O_RDONLY | O_NOCTTY);
if(m_fd < 0)
throw std::runtime_error("System_RNG failed to open RNG device");
#endif
}
System_RNG_Impl::~System_RNG_Impl()
{
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
::CryptReleaseContext(m_prov, 0);
#else
::close(m_fd);
m_fd = -1;
#endif
}
void System_RNG_Impl::randomize(byte buf[], size_t len)
{
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
::CryptGenRandom(m_prov, static_cast<DWORD>(len), buf);
#else
while(len)
{
ssize_t got = ::read(m_fd, buf, len);
if(got < 0)
{
if(errno == EINTR)
continue;
throw std::runtime_error("System_RNG read failed error " + std::to_string(errno));
}
if(got == 0)
throw std::runtime_error("System_RNG EOF on device"); // ?!?
buf += got;
len -= got;
}
#endif
}
}
RandomNumberGenerator& system_rng()
{
static System_RNG_Impl g_system_rng;
return g_system_rng;
}
}
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