Fix of CVE-2017-18350

Adapted from bitcoin/bitcoin#11397 by Wladimir J. van der Laan.

Co-Authored-By: Jack Grigg <jack@electriccoin.co>
Co-Authored-By: Daira Hopwood <daira@electriccoin.co>

src/netbase.cpp

@@ -267,7 +267,7 @@ struct timeval MillisToTimeval(int64_t nTimeout)
  *
  * @note This function requires that hSocket is in non-blocking mode.
  */
-bool static InterruptibleRecv(char* data, size_t len, int timeout, SOCKET& hSocket)
+bool static InterruptibleRecv(uint8_t* data, size_t len, int timeout, SOCKET& hSocket)
 {
     int64_t curTime = GetTimeMillis();
     int64_t endTime = curTime + timeout;
@@ -335,7 +335,7 @@ static bool Socks5(const std::string& strDest, int port, const ProxyCredentials
         CloseSocket(hSocket);
         return error("Error sending to proxy");
     }
-    char pchRet1[2];
+    uint8_t pchRet1[2];
     if (!InterruptibleRecv(pchRet1, 2, SOCKS5_RECV_TIMEOUT, hSocket)) {
         CloseSocket(hSocket);
         return error("Error reading proxy response");
@@ -360,7 +360,7 @@ static bool Socks5(const std::string& strDest, int port, const ProxyCredentials
             return error("Error sending authentication to proxy");
         }
         LogPrint("proxy", "SOCKS5 sending proxy authentication %s:%s\n", auth->username, auth->password);
-        char pchRetA[2];
+        uint8_t pchRetA[2];
         if (!InterruptibleRecv(pchRetA, 2, SOCKS5_RECV_TIMEOUT, hSocket)) {
             CloseSocket(hSocket);
             return error("Error reading proxy authentication response");
@@ -389,7 +389,7 @@ static bool Socks5(const std::string& strDest, int port, const ProxyCredentials
         CloseSocket(hSocket);
         return error("Error sending to proxy");
     }
-    char pchRet2[4];
+    uint8_t pchRet2[4];
     if (!InterruptibleRecv(pchRet2, 4, SOCKS5_RECV_TIMEOUT, hSocket)) {
         CloseSocket(hSocket);
         return error("Error reading proxy response");
@@ -417,7 +417,7 @@ static bool Socks5(const std::string& strDest, int port, const ProxyCredentials
         CloseSocket(hSocket);
         return error("Error: malformed proxy response");
     }
-    char pchRet3[256];
+    uint8_t pchRet3[256];
     switch (pchRet2[3])
     {
         case 0x01: ret = InterruptibleRecv(pchRet3, 4, SOCKS5_RECV_TIMEOUT, hSocket); break;
@@ -429,7 +429,7 @@ static bool Socks5(const std::string& strDest, int port, const ProxyCredentials
                 CloseSocket(hSocket);
                 return error("Error reading from proxy");
             }
-            int nRecv = pchRet3[0];
+            size_t nRecv = pchRet3[0];
             ret = InterruptibleRecv(pchRet3, nRecv, SOCKS5_RECV_TIMEOUT, hSocket);
             break;
         }