don't use memset() in privacy/security relevant code parts

As memset() can be optimized out by a compiler it should not be used in
privacy/security relevant code parts. OpenSSL provides the safe
OPENSSL_cleanse() function in crypto.h, which perfectly does the job of
clean and overwrite data.

For details see: http://www.viva64.com/en/b/0178/

- change memset() to OPENSSL_cleanse() where appropriate
- change a hard-coded number from netbase.cpp into a sizeof()

src/allocators.h

@@ -9,6 +9,7 @@
 #include <string>
 #include <boost/thread/mutex.hpp>
 #include <map>
+#include <openssl/crypto.h> // for OPENSSL_cleanse()
 
 #ifdef WIN32
 #ifdef _WIN32_WINNT
@@ -212,7 +213,7 @@ struct secure_allocator : public std::allocator<T>
     {
         if (p != NULL)
         {
-            memset(p, 0, sizeof(T) * n);
+            OPENSSL_cleanse(p, sizeof(T) * n);
             LockedPageManager::instance.UnlockRange(p, sizeof(T) * n);
         }
         std::allocator<T>::deallocate(p, n);
@@ -246,7 +247,7 @@ struct zero_after_free_allocator : public std::allocator<T>
     void deallocate(T* p, std::size_t n)
     {
         if (p != NULL)
-            memset(p, 0, sizeof(T) * n);
+            OPENSSL_cleanse(p, sizeof(T) * n);
         std::allocator<T>::deallocate(p, n);
     }
 };

src/base58.h

@@ -17,6 +17,8 @@
 
 #include <string>
 #include <vector>
+#include <openssl/crypto.h> // for OPENSSL_cleanse()
+
 #include "bignum.h"
 #include "key.h"
 #include "script.h"
@@ -190,7 +192,7 @@ protected:
     {
         // zero the memory, as it may contain sensitive data
         if (!vchData.empty())
-            memset(&vchData[0], 0, vchData.size());
+            OPENSSL_cleanse(&vchData[0], vchData.size());
     }
 
     void SetData(int nVersionIn, const void* pdata, size_t nSize)
@@ -221,7 +223,7 @@ public:
         vchData.resize(vchTemp.size() - 1);
         if (!vchData.empty())
             memcpy(&vchData[0], &vchTemp[1], vchData.size());
-        memset(&vchTemp[0], 0, vchTemp.size());
+        OPENSSL_cleanse(&vchTemp[0], vchData.size());
         return true;
     }
 

src/crypter.cpp

@@ -24,8 +24,8 @@ bool CCrypter::SetKeyFromPassphrase(const SecureString& strKeyData, const std::v
 
     if (i != (int)WALLET_CRYPTO_KEY_SIZE)
     {
-        memset(&chKey, 0, sizeof chKey);
-        memset(&chIV, 0, sizeof chIV);
+        OPENSSL_cleanse(chKey, sizeof(chKey));
+        OPENSSL_cleanse(chIV, sizeof(chIV));
         return false;
     }
 

src/crypter.h

@@ -76,8 +76,8 @@ public:
 
     void CleanKey()
     {
-        memset(&chKey, 0, sizeof chKey);
-        memset(&chIV, 0, sizeof chIV);
+        OPENSSL_cleanse(chKey, sizeof(chKey));
+        OPENSSL_cleanse(chIV, sizeof(chIV));
         fKeySet = false;
     }
 

src/netbase.cpp

@@ -545,7 +545,7 @@ bool ConnectSocketByName(CService &addr, SOCKET& hSocketRet, const char *pszDest
 
 void CNetAddr::Init()
 {
-    memset(ip, 0, 16);
+    memset(ip, 0, sizeof(ip));
 }
 
 void CNetAddr::SetIP(const CNetAddr& ipIn)

src/util.cpp

@@ -156,7 +156,7 @@ void RandAddSeedPerfmon()
     if (ret == ERROR_SUCCESS)
     {
         RAND_add(pdata, nSize, nSize/100.0);
-        memset(pdata, 0, nSize);
+        OPENSSL_cleanse(pdata, nSize);
         printf("RandAddSeed() %lu bytes\n", nSize);
     }
 #endif