http: auto-configure for local Tor proxy if called as 'tor'

With apts http transport supporting socks5h proxies and all the work
in terms of configuration of methods based on the name it is called with
it becomes surprisingly easy to implement Tor support equally (and
perhaps even a bit exceeding) what is available currently in
apt-transport-tor.

How this will turn out to be handled packaging wise we will see in
https://lists.debian.org/deity/2016/08/msg00012.html , but until this is
resolved we can add the needed support without actively enabling it for
now, so that this can be tested better.

methods/http.cc

@@ -357,6 +357,9 @@ bool HttpServerState::Open()
 	 Proxy = "";
    }
 
+   if (Proxy.empty() == false)
+      Owner->AddProxyAuth(Proxy, ServerName);
+
    if (Proxy.Access == "socks5h")
    {
       if (Connect(Proxy.Host, Proxy.Port, "socks", 1080, ServerFd, TimeOut, Owner) == false)

methods/https.cc

@@ -213,6 +213,8 @@ bool HttpsMethod::SetupProxy()						/*{{{*/
    if (UseProxy.empty() == false)
    {
       Proxy = UseProxy;
+      AddProxyAuth(Proxy, ServerName);
+
       if (Proxy.Access == "socks5h")
 	 curl_easy_setopt(curl, CURLOPT_PROXYTYPE, CURLPROXY_SOCKS5_HOSTNAME);
       else if (Proxy.Access == "socks5")

methods/server.cc

@@ -794,3 +794,29 @@ ServerMethod::ServerMethod(std::string &&Binary, char const * const Ver,unsigned
 {
 }
 									/*}}}*/
+bool ServerMethod::Configuration(std::string Message)			/*{{{*/
+{
+   if (aptMethod::Configuration(Message) == false)
+      return false;
+
+   _config->CndSet("Acquire::tor::Proxy",
+	 "socks5h://apt-transport-tor@localhost:9050");
+   return true;
+}
+									/*}}}*/
+bool ServerMethod::AddProxyAuth(URI &Proxy, URI const &Server) const	/*{{{*/
+{
+   if (std::find(methodNames.begin(), methodNames.end(), "tor") != methodNames.end() &&
+	 Proxy.User == "apt-transport-tor" && Proxy.Password.empty())
+   {
+      std::string pass = Server.Host;
+      pass.erase(std::remove_if(pass.begin(), pass.end(), [](char const c) { return std::isalnum(c) == 0; }), pass.end());
+      if (pass.length() > 255)
+	 Proxy.Password = pass.substr(0, 255);
+      else
+	 Proxy.Password = std::move(pass);
+   }
+   // FIXME: should we support auth.conf for proxies?
+   return true;
+}
+									/*}}}*/

methods/server.h

@@ -156,6 +156,9 @@ class ServerMethod : public aptMethod
    virtual void SendReq(FetchItem *Itm) = 0;
    virtual std::unique_ptr<ServerState> CreateServerState(URI const &uri) = 0;
    virtual void RotateDNS() = 0;
+   virtual bool Configuration(std::string Message) APT_OVERRIDE;
+
+   bool AddProxyAuth(URI &Proxy, URI const &Server) const;
 
    ServerMethod(std::string &&Binary, char const * const Ver,unsigned long const Flags);
    virtual ~ServerMethod() {};