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/*
* System RNG
* (C) 2014,2015,2017,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/system_rng.h>
#if defined(BOTAN_TARGET_OS_HAS_RTLGENRANDOM)
#include <botan/dyn_load.h>
#define NOMINMAX 1
#define _WINSOCKAPI_ // stop windows.h including winsock.h
#include <windows.h>
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
#include <stdlib.h>
#elif defined(BOTAN_TARGET_OS_HAS_DEV_RANDOM)
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#endif
namespace Botan {
namespace {
#if defined(BOTAN_TARGET_OS_HAS_RTLGENRANDOM)
class System_RNG_Impl final : public RandomNumberGenerator
{
public:
System_RNG_Impl() : m_advapi("advapi32.dll")
{
// This throws if the function is not found
m_rtlgenrandom = m_advapi.resolve<RtlGenRandom_f>("SystemFunction036");
}
void randomize(uint8_t buf[], size_t len) override
{
if(m_rtlgenrandom(buf, len) == false)
throw Exception("RtlGenRandom failed");
}
void add_entropy(const uint8_t[], size_t) override { /* ignored */ }
bool is_seeded() const override { return true; }
void clear() override { /* not possible */ }
std::string name() const override { return "RtlGenRandom"; }
private:
typedef BOOL (NTAPI *RtlGenRandom_f)(PVOID, ULONG);
Dynamically_Loaded_Library m_advapi;
RtlGenRandom_f m_rtlgenrandom;
};
#elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
class System_RNG_Impl final : public RandomNumberGenerator
{
public:
// No constructor or destructor needed as no userland state maintained
void randomize(uint8_t buf[], size_t len) override
{
::arc4random_buf(buf, len);
}
void add_entropy(const uint8_t[], size_t) override { /* ignored */ }
bool is_seeded() const override { return true; }
void clear() override { /* not possible */ }
std::string name() const override { return "arc4random"; }
};
#elif defined(BOTAN_TARGET_OS_HAS_DEV_RANDOM)
// Read a random device
class System_RNG_Impl final : public RandomNumberGenerator
{
public:
System_RNG_Impl()
{
#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");
}
~System_RNG_Impl()
{
::close(m_fd);
m_fd = -1;
}
void randomize(uint8_t buf[], size_t len) override;
void add_entropy(const uint8_t in[], size_t length) override;
bool is_seeded() const override { return true; }
void clear() override { /* not possible */ }
std::string name() const override { return BOTAN_SYSTEM_RNG_DEVICE; }
private:
int m_fd;
};
void System_RNG_Impl::randomize(uint8_t buf[], size_t len)
{
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;
}
}
void System_RNG_Impl::add_entropy(const uint8_t input[], size_t len)
{
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
}
RandomNumberGenerator& system_rng()
{
static System_RNG_Impl g_system_rng;
return g_system_rng;
}
}
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