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diff --git a/zto/node/Utils.cpp b/zto/node/Utils.cpp
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+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2016 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/>.
+ */
+
+#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); }
+
+std::string Utils::hex(const void *data,unsigned int len)
+{
+ std::string r;
+ r.reserve(len * 2);
+ for(unsigned int i=0;i<len;++i) {
+ r.push_back(HEXCHARS[(((const unsigned char *)data)[i] & 0xf0) >> 4]);
+ r.push_back(HEXCHARS[((const unsigned char *)data)[i] & 0x0f]);
+ }
+ return r;
+}
+
+std::string Utils::unhex(const char *hex,unsigned int maxlen)
+{
+ int n = 1;
+ unsigned char c,b = 0;
+ const char *eof = hex + maxlen;
+ std::string r;
+
+ if (!maxlen)
+ return r;
+
+ while ((c = (unsigned char)*(hex++))) {
+ if ((c >= 48)&&(c <= 57)) { // 0..9
+ if ((n ^= 1))
+ r.push_back((char)(b | (c - 48)));
+ else b = (c - 48) << 4;
+ } else if ((c >= 65)&&(c <= 70)) { // A..F
+ if ((n ^= 1))
+ r.push_back((char)(b | (c - (65 - 10))));
+ else b = (c - (65 - 10)) << 4;
+ } else if ((c >= 97)&&(c <= 102)) { // a..f
+ if ((n ^= 1))
+ r.push_back((char)(b | (c - (97 - 10))));
+ else b = (c - (97 - 10)) << 4;
+ }
+ if (hex == eof)
+ break;
+ }
+
+ return r;
+}
+
+unsigned int Utils::unhex(const char *hex,unsigned int maxlen,void *buf,unsigned int len)
+{
+ int n = 1;
+ unsigned char c,b = 0;
+ unsigned int l = 0;
+ const char *eof = hex + maxlen;
+
+ if (!maxlen)
+ return 0;
+
+ while ((c = (unsigned char)*(hex++))) {
+ if ((c >= 48)&&(c <= 57)) { // 0..9
+ if ((n ^= 1)) {
+ if (l >= len) break;
+ ((unsigned char *)buf)[l++] = (b | (c - 48));
+ } else b = (c - 48) << 4;
+ } else if ((c >= 65)&&(c <= 70)) { // A..F
+ if ((n ^= 1)) {
+ if (l >= len) break;
+ ((unsigned char *)buf)[l++] = (b | (c - (65 - 10)));
+ } else b = (c - (65 - 10)) << 4;
+ } else if ((c >= 97)&&(c <= 102)) { // a..f
+ if ((n ^= 1)) {
+ if (l >= len) break;
+ ((unsigned char *)buf)[l++] = (b | (c - (97 - 10)));
+ } else b = (c - (97 - 10)) << 4;
+ }
+ if (hex == eof)
+ break;
+ }
+
+ return l;
+}
+
+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,256,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));
+ }
+ ((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));
+ }
+ ((uint8_t *)buf)[i] = randomBuf[randomPtr++];
+ }
+
+#endif // __WINDOWS__ or not
+}
+
+bool Utils::scopy(char *dest,unsigned int len,const char *src)
+{
+ if (!len)
+ return false; // sanity check
+ if (!src) {
+ *dest = (char)0;
+ return true;
+ }
+ char *end = dest + len;
+ while ((*dest++ = *src++)) {
+ if (dest == end) {
+ *(--dest) = (char)0;
+ return false;
+ }
+ }
+ return true;
+}
+
+unsigned int Utils::snprintf(char *buf,unsigned int len,const char *fmt,...)
+ throw(std::length_error)
+{
+ va_list ap;
+
+ va_start(ap,fmt);
+ int n = (int)vsnprintf(buf,len,fmt,ap);
+ va_end(ap);
+
+ if ((n >= (int)len)||(n < 0)) {
+ if (len)
+ buf[len - 1] = (char)0;
+ throw std::length_error("buf[] overflow in Utils::snprintf");
+ }
+
+ return (unsigned int)n;
+}
+
+} // namespace ZeroTier
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