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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>
#include <botan/build.h>
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
#include <windows.h>
#define NOMINMAX 1
#include <wincrypt.h>
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
#include <stdlib.h>
#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 final : public RandomNumberGenerator
{
public:
System_RNG_Impl();
~System_RNG_Impl();
bool is_seeded() const override { return true; }
void clear() override {}
void randomize(uint8_t out[], size_t len) override;
void add_entropy(const uint8_t in[], size_t length) override;
std::string name() const override;
private:
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
HCRYPTPROV m_prov;
#else
int m_fd;
#endif
};
std::string System_RNG_Impl::name() const
{
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
return "cryptoapi";
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
return "arc4random";
#else
return BOTAN_SYSTEM_RNG_DEVICE;
#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 Exception("System_RNG failed to acquire crypto provider");
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
// Nothing to do, arc4random(3) works from the beginning.
#else
#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif
m_fd = ::open(BOTAN_SYSTEM_RNG_DEVICE, O_RDWR | O_NOCTTY);
// Cannot open in read-write mode. Fall back to read-only
// Calls to add_entropy will fail, but randomize will work
if(m_fd < 0)
m_fd = ::open(BOTAN_SYSTEM_RNG_DEVICE, O_RDONLY | O_NOCTTY);
if(m_fd < 0)
throw Exception("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);
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
// Nothing to do.
#else
::close(m_fd);
m_fd = -1;
#endif
}
void System_RNG_Impl::add_entropy(const uint8_t input[], size_t len)
{
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
/*
There is no explicit ConsumeRandom, but all values provided in
the call are incorporated into the state.
TODO: figure out a way to avoid this copy. Byte at a time updating
seems worse than the allocation.
for(size_t i = 0; i != len; ++i)
{
uint8_t b = input[i];
::CryptGenRandom(m_prov, 1, &b);
}
*/
if(len > 0)
{
secure_vector<uint8_t> buf(input, input + len);
::CryptGenRandom(m_prov, static_cast<DWORD>(buf.size()), buf.data());
}
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
// arc4random(3) reseeds itself from the OpenBSD kernel, not from user land.
#else
while(len)
{
ssize_t got = ::write(m_fd, input, len);
if(got < 0)
{
if(errno == EINTR)
continue;
/*
* This is seen on OS X CI, despite the fact that the man page
* for Darwin urandom explicitly states that writing to it is
* supported, and write(2) does not document EPERM at all.
* But in any case EPERM seems indicative of a policy decision
* by the OS or sysadmin that additional entropy is not wanted
* in the system pool, so we accept that and return here,
* since there is no corrective action possible.
*
* In Linux EBADF or EPERM is returned if m_fd is not opened for
* writing.
*/
if(errno == EPERM || errno == EBADF)
return;
// maybe just ignore any failure here and return?
throw Exception("System_RNG write failed error " + std::to_string(errno));
}
input += got;
len -= got;
}
#endif
}
void System_RNG_Impl::randomize(uint8_t buf[], size_t len)
{
#if defined(BOTAN_TARGET_OS_HAS_CRYPTGENRANDOM)
::CryptGenRandom(m_prov, static_cast<DWORD>(len), buf);
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
::arc4random_buf(buf, len);
#else
while(len)
{
ssize_t got = ::read(m_fd, buf, len);
if(got < 0)
{
if(errno == EINTR)
continue;
throw Exception("System_RNG read failed error " + std::to_string(errno));
}
if(got == 0)
throw Exception("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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