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// **********************************************************************
//
// Copyright (c) 2003-2009 ZeroC, Inc. All rights reserved.
//
// This copy of Ice is licensed to you under the terms described in the
// ICE_LICENSE file included in this distribution.
//
// **********************************************************************
#include <IceUtil/Random.h>
#include <IceUtil/StaticMutex.h>
#ifdef _WIN32
# include <Wincrypt.h>
#else
# include <unistd.h>
# include <fcntl.h>
#endif
using namespace std;
using namespace IceUtil;
//
// The static mutex is required to lazy initialize the file
// descriptor for /dev/urandom (Unix) or the cryptographic
// context (Windows).
//
// Also, unfortunately on Linux (at least up to 2.6.9), concurrent
// access to /dev/urandom can return the same value. Search for
// "Concurrent access to /dev/urandom" in the linux-kernel mailing
// list archive for additional details. Since /dev/urandom on other
// platforms is usually a port from Linux, this problem could be
// widespread. Therefore, we serialize access to /dev/urandom using a
// static mutex.
//
static StaticMutex staticMutex = ICE_STATIC_MUTEX_INITIALIZER;
#ifdef _WIN32
static HCRYPTPROV context = NULL;
#else
static int fd = -1;
#endif
namespace
{
//
// Close fd at exit
//
class RandomCleanup
{
public:
~RandomCleanup()
{
#ifdef _WIN32
if(context != NULL)
{
CryptReleaseContext(context, 0);
context = NULL;
}
#else
if(fd != -1)
{
close(fd);
fd = -1;
}
#endif
}
};
static RandomCleanup uuidCleanup;
}
void
IceUtilInternal::generateRandom(char* buffer, int size)
{
#ifdef _WIN32
//
// It's not clear from the Microsoft documentation if CryptGenRandom
// can be called concurrently from several threads. To be on the safe
// side, we also serialize calls to to CryptGenRandom with the static
// mutex.
//
IceUtil::StaticMutex::Lock lock(staticMutex);
if(context == NULL)
{
if(!CryptAcquireContext(&context, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
{
throw SyscallException(__FILE__, __LINE__, GetLastError());
}
}
if(!CryptGenRandom(context, size, reinterpret_cast<unsigned char*>(buffer)))
{
throw SyscallException(__FILE__, __LINE__, GetLastError());
}
#else
//
// Serialize access to /dev/urandom; see comment above.
//
StaticMutex::Lock lock(staticMutex);
if(fd == -1)
{
fd = open("/dev/urandom", O_RDONLY);
if(fd == -1)
{
assert(0);
throw SyscallException(__FILE__, __LINE__, errno);
}
}
//
// Limit the number of attempts to 20 reads to avoid
// a potential "for ever" loop
//
int reads = 0;
size_t index = 0;
while(reads <= 20 && index != static_cast<size_t>(size))
{
ssize_t bytesRead = read(fd, buffer + index, static_cast<size_t>(size) - index);
if(bytesRead == -1 && errno != EINTR)
{
SyscallException ex(__FILE__, __LINE__, errno);
cerr << "Reading /dev/urandom failed:\n" << ex << endl;
assert(0);
throw ex;
}
else
{
index += bytesRead;
reads++;
}
}
if(index != static_cast<size_t>(size))
{
assert(0);
throw SyscallException(__FILE__, __LINE__, 0);
}
#endif
}
int
IceUtilInternal::random(int limit)
{
int r;
generateRandom(reinterpret_cast<char*>(&r), static_cast<int>(sizeof(int)));
if(limit > 0)
{
r = r % limit;
}
if(r < 0)
{
r = -r;
}
return r;
}
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