Add LuaSecureRandom

src/porting.cpp

@@ -29,6 +29,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 	#include <sys/types.h>
 	#include <sys/sysctl.h>
 #elif defined(_WIN32)
+	#include <windows.h>
+	#include <wincrypt.h>
 	#include <algorithm>
 #endif
 #if !defined(_WIN32)
@@ -701,5 +703,44 @@ v2u32 getDisplaySize()
 #	endif // __ANDROID__
 #endif // SERVER
 
-} //namespace porting
 
+////
+//// OS-specific Secure Random
+////
+
+#ifdef WIN32
+
+bool secure_rand_fill_buf(void *buf, size_t len)
+{
+	HCRYPTPROV wctx;
+
+	if (!CryptAcquireContext(&wctx, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
+		return false;
+
+	CryptGenRandom(wctx, len, (BYTE *)buf);
+	CryptReleaseContext(wctx, 0);
+	return true;
+}
+
+#else
+
+bool secure_rand_fill_buf(void *buf, size_t len)
+{
+	// N.B.  This function checks *only* for /dev/urandom, because on most
+	// common OSes it is non-blocking, whereas /dev/random is blocking, and it
+	// is exceptionally uncommon for there to be a situation where /dev/random
+	// exists but /dev/urandom does not.  This guesswork is necessary since
+	// random devices are not covered by any POSIX standard...
+	FILE *fp = fopen("/dev/urandom", "rb");
+	if (!fp)
+		return false;
+
+	bool success = fread(buf, len, 1, fp) == 1;
+
+	fclose(fp);
+	return success;
+}
+
+#endif
+
+} //namespace porting