Core/Shared: Add thread-safe access to BigNumber::AsByteArray()

fixes #5469

src/server/shared/Cryptography/BigNumber.cpp

@@ -169,6 +169,8 @@ uint8 *BigNumber::AsByteArray(int minSize, bool reverse)
 {
     int length = (minSize >= GetNumBytes()) ? minSize : GetNumBytes();
 
+    ACE_GUARD_RETURN(ACE_Mutex, g, _lock, 0);
+
     if (_array)
     {
         delete[] _array;

src/server/shared/Cryptography/BigNumber.h

@@ -20,6 +20,7 @@
 #define _AUTH_BIGNUMBER_H
 
 #include "Define.h"
+#include <ace/Mutex.h>
 
 struct bignum_st;
 
@@ -89,6 +90,10 @@ class BigNumber
     private:
         struct bignum_st *_bn;
         uint8 *_array;
+
+        // This mutex only controls thread-safe access to AsByteArray() and should be replaced with a thread-safe implementation of BigNumber
+        ACE_Mutex _lock;
+
 };
 #endif