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/*
* ZeroTier One - Network Virtualization Everywhere
* Copyright (C) 2011-2019 ZeroTier, Inc. https://www.zerotier.com/
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* --
*
* You can be released from the requirements of the license by purchasing
* a commercial license. Buying such a license is mandatory as soon as you
* develop commercial closed-source software that incorporates or links
* directly against ZeroTier software without disclosing the source code
* of your own application.
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <time.h>
#include <sys/stat.h>
#include "Constants.hpp"
#ifdef __UNIX_LIKE__
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <dirent.h>
#endif
#ifdef __WINDOWS__
#include <wincrypt.h>
#endif
#include "Utils.hpp"
#include "Mutex.hpp"
#include "Salsa20.hpp"
namespace ZeroTier {
const char Utils::HEXCHARS[16] = { '0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f' };
// Crazy hack to force memory to be securely zeroed in spite of the best efforts of optimizing compilers.
static void _Utils_doBurn(volatile uint8_t *ptr,unsigned int len)
{
volatile uint8_t *const end = ptr + len;
while (ptr != end) *(ptr++) = (uint8_t)0;
}
static void (*volatile _Utils_doBurn_ptr)(volatile uint8_t *,unsigned int) = _Utils_doBurn;
void Utils::burn(void *ptr,unsigned int len) { (_Utils_doBurn_ptr)((volatile uint8_t *)ptr,len); }
static unsigned long _Utils_itoa(unsigned long n,char *s)
{
if (n == 0)
return 0;
unsigned long pos = _Utils_itoa(n / 10,s);
if (pos >= 22) // sanity check, should be impossible
pos = 22;
s[pos] = '0' + (char)(n % 10);
return pos + 1;
}
char *Utils::decimal(unsigned long n,char s[24])
{
if (n == 0) {
s[0] = '0';
s[1] = (char)0;
return s;
}
s[_Utils_itoa(n,s)] = (char)0;
return s;
}
void Utils::getSecureRandom(void *buf,unsigned int bytes)
{
static Mutex globalLock;
static Salsa20 s20;
static bool s20Initialized = false;
static uint8_t randomBuf[65536];
static unsigned int randomPtr = sizeof(randomBuf);
Mutex::Lock _l(globalLock);
/* Just for posterity we Salsa20 encrypt the result of whatever system
* CSPRNG we use. There have been several bugs at the OS or OS distribution
* level in the past that resulted in systematically weak or predictable
* keys due to random seeding problems. This mitigates that by grabbing
* a bit of extra entropy and further randomizing the result, and comes
* at almost no cost and with no real downside if the random source is
* good. */
if (!s20Initialized) {
s20Initialized = true;
uint64_t s20Key[4];
s20Key[0] = (uint64_t)time(0); // system clock
s20Key[1] = (uint64_t)buf; // address of buf
s20Key[2] = (uint64_t)s20Key; // address of s20Key[]
s20Key[3] = (uint64_t)&s20; // address of s20
s20.init(s20Key,s20Key);
}
#ifdef __WINDOWS__
static HCRYPTPROV cryptProvider = NULL;
for(unsigned int i=0;i<bytes;++i) {
if (randomPtr >= sizeof(randomBuf)) {
if (cryptProvider == NULL) {
if (!CryptAcquireContextA(&cryptProvider,NULL,NULL,PROV_RSA_FULL,CRYPT_VERIFYCONTEXT|CRYPT_SILENT)) {
fprintf(stderr,"FATAL ERROR: Utils::getSecureRandom() unable to obtain WinCrypt context!\r\n");
exit(1);
}
}
if (!CryptGenRandom(cryptProvider,(DWORD)sizeof(randomBuf),(BYTE *)randomBuf)) {
fprintf(stderr,"FATAL ERROR: Utils::getSecureRandom() CryptGenRandom failed!\r\n");
exit(1);
}
randomPtr = 0;
s20.crypt12(randomBuf,randomBuf,sizeof(randomBuf));
s20.init(randomBuf,randomBuf);
}
((uint8_t *)buf)[i] = randomBuf[randomPtr++];
}
#else // not __WINDOWS__
static int devURandomFd = -1;
if (devURandomFd < 0) {
devURandomFd = ::open("/dev/urandom",O_RDONLY);
if (devURandomFd < 0) {
fprintf(stderr,"FATAL ERROR: Utils::getSecureRandom() unable to open /dev/urandom\n");
exit(1);
return;
}
}
for(unsigned int i=0;i<bytes;++i) {
if (randomPtr >= sizeof(randomBuf)) {
for(;;) {
if ((int)::read(devURandomFd,randomBuf,sizeof(randomBuf)) != (int)sizeof(randomBuf)) {
::close(devURandomFd);
devURandomFd = ::open("/dev/urandom",O_RDONLY);
if (devURandomFd < 0) {
fprintf(stderr,"FATAL ERROR: Utils::getSecureRandom() unable to open /dev/urandom\n");
exit(1);
return;
}
} else break;
}
randomPtr = 0;
s20.crypt12(randomBuf,randomBuf,sizeof(randomBuf));
s20.init(randomBuf,randomBuf);
}
((uint8_t *)buf)[i] = randomBuf[randomPtr++];
}
#endif // __WINDOWS__ or not
}
} // namespace ZeroTier
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