privacy: Stream isolation for Tor

According to Tor's extensions to the SOCKS protocol
(https://gitweb.torproject.org/torspec.git/tree/socks-extensions.txt)
it is possible to perform stream isolation by providing authentication
to the proxy. Each set of credentials will create a new circuit,
which makes it harder to correlate connections.

This patch adds an option, `-proxyrandomize` (on by default) that randomizes
credentials for every outgoing connection, thus creating a new circuit.

    2015-03-16 15:29:59 SOCKS5 Sending proxy authentication 3842137544:3256031132

1 files changed, 13 insertions, 3 deletions

diff --git a/src/netbase.h b/src/netbase.h
index b42c2dffa4..6d2ca4afb2 100644
--- a/src/netbase.h
+++ b/src/netbase.h
@@ -168,15 +168,25 @@ class CService : public CNetAddr
         }
 };
 
-typedef CService proxyType;
+class proxyType
+{
+public:
+    proxyType(): randomize_credentials(false) {}
+    proxyType(const CService &proxy, bool randomize_credentials=false): proxy(proxy), randomize_credentials(randomize_credentials) {}
+
+    bool IsValid() const { return proxy.IsValid(); }
+
+    CService proxy;
+    bool randomize_credentials;
+};
 
 enum Network ParseNetwork(std::string net);
 std::string GetNetworkName(enum Network net);
 void SplitHostPort(std::string in, int &portOut, std::string &hostOut);
-bool SetProxy(enum Network net, CService addrProxy);
+bool SetProxy(enum Network net, const proxyType &addrProxy);
 bool GetProxy(enum Network net, proxyType &proxyInfoOut);
 bool IsProxy(const CNetAddr &addr);
-bool SetNameProxy(CService addrProxy);
+bool SetNameProxy(const proxyType &addrProxy);
 bool HaveNameProxy();
 bool LookupHost(const char *pszName, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions = 0, bool fAllowLookup = true);
 bool Lookup(const char *pszName, CService& addr, int portDefault = 0, bool fAllowLookup = true);