Implement CONNECT pass-through for HTTPS proxy

* When using a proxy, HTTPS connexion must still go directly to the
  target website. The proxy can then act as a TCP stream relay and just
  transmit the raw SSL stream between the client and website.
* For this, we ask the proxy sending an HTTP request with the CONNECT
  method. If the proxy supports this, we can then send anything as the
  payload and it will be forwarded.
* Untested, as the network here in Dusseldorf doesn't let me use a
  proxy.

ticket : #10973

headers/os/net/HttpRequest.h

@@ -16,6 +16,12 @@
 #include <NetworkRequest.h>
 
 
+namespace BPrivate {
+	class CheckedSecureSocket;
+	class CheckedProxySecureSocket;
+};
+
+
 class BHttpRequest : public BNetworkRequest {
 public:
 								BHttpRequest(const BUrl& url,
@@ -76,7 +82,8 @@ private:
 			BString&			_ResultStatusText();
 
 	// SSL failure management
-	friend	class				CheckedSecureSocket;
+	friend	class				BPrivate::CheckedSecureSocket;
+	friend	class				BPrivate::CheckedProxySecureSocket;
 			bool				_CertificateVerificationFailed(
 									BCertificate& certificate,
 									const char* message);

headers/os/net/ProxySecureSocket.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2015, Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _PROXY_SECURE_SOCKET_H
+#define _PROXY_SECURE_SOCKET_H
+
+
+#include <SecureSocket.h>
+
+
+class BProxySecureSocket : public BSecureSocket {
+public:
+								BProxySecureSocket(const BNetworkAddress& proxy);
+								BProxySecureSocket(const BNetworkAddress& proxy,
+									const BNetworkAddress& peer,
+									bigtime_t timeout = B_INFINITE_TIMEOUT);
+								BProxySecureSocket(const BProxySecureSocket& other);
+	virtual						~BProxySecureSocket();
+
+	// BSocket implementation
+
+	virtual	status_t			Connect(const BNetworkAddress& peer,
+									bigtime_t timeout = B_INFINITE_TIMEOUT);
+
+private:
+	const BNetworkAddress		fProxyAddress;
+};
+
+
+#endif	// _PROXY_SECURE_SOCKET_H
+

headers/os/net/SecureSocket.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011, Haiku, Inc. All Rights Reserved.
+ * Copyright 2011-2015, Haiku, Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
  */
 #ifndef _SECURE_SOCKET_H
@@ -23,6 +23,8 @@ public:
 	virtual bool				CertificateVerificationFailed(BCertificate&
 									certificate, const char* message);
 
+			status_t			InitCheck();
+
 	// BSocket implementation
 
 	virtual	status_t			Connect(const BNetworkAddress& peer,
@@ -37,6 +39,9 @@ public:
 	virtual ssize_t				Read(void* buffer, size_t size);
 	virtual ssize_t				Write(const void* buffer, size_t size);
 
+protected:
+			status_t			_Setup();
+
 private:
 	friend class BCertificate;
 			class Private;