Add feature to Socket so that it can send digests of data it has sent

and check those digests on receive.

4 files changed, 159 insertions, 1 deletions

diff --git a/src/lib/dcpomatic_socket.cc b/src/lib/dcpomatic_socket.cc
index ca910bb79..a0a7a1cf3 100644
--- a/src/lib/dcpomatic_socket.cc
+++ b/src/lib/dcpomatic_socket.cc
@@ -1,5 +1,5 @@
 /*
-    Copyright (C) 2012-2015 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2020 Carl Hetherington <cth@carlh.net>
 
     This file is part of DCP-o-matic.
 
@@ -21,12 +21,16 @@
 #include "dcpomatic_socket.h"
 #include "compose.hpp"
 #include "exceptions.h"
+#include "dcpomatic_assert.h"
 #include <boost/bind.hpp>
 #include <boost/lambda/lambda.hpp>
 #include <iostream>
 
 #include "i18n.h"
 
+using boost::shared_ptr;
+using boost::weak_ptr;
+
 /** @param timeout Timeout in seconds */
 Socket::Socket (int timeout)
 	: _deadline (_io_service)
@@ -89,6 +93,10 @@ Socket::write (uint8_t const * data, int size)
 	if (ec) {
 		throw NetworkError (String::compose (_("error during async_write (%1)"), ec.value ()));
 	}
+
+	if (_write_digester) {
+		_write_digester->add (data, static_cast<size_t>(size));
+	}
 }
 
 void
@@ -117,6 +125,10 @@ Socket::read (uint8_t* data, int size)
 	if (ec) {
 		throw NetworkError (String::compose (_("error during async_read (%1)"), ec.value ()));
 	}
+
+	if (_read_digester) {
+		_read_digester->add (data, static_cast<size_t>(size));
+	}
 }
 
 uint32_t
@@ -126,3 +138,98 @@ Socket::read_uint32 ()
 	read (reinterpret_cast<uint8_t *> (&v), 4);
 	return ntohl (v);
 }
+
+
+void
+Socket::start_read_digest ()
+{
+	DCPOMATIC_ASSERT (!_read_digester);
+	_read_digester.reset (new Digester());
+}
+
+void
+Socket::start_write_digest ()
+{
+	DCPOMATIC_ASSERT (!_write_digester);
+	_write_digester.reset (new Digester());
+}
+
+
+Socket::ReadDigestScope::ReadDigestScope (shared_ptr<Socket> socket)
+	: _socket (socket)
+{
+	socket->start_read_digest ();
+}
+
+
+bool
+Socket::ReadDigestScope::check ()
+{
+	shared_ptr<Socket> sp = _socket.lock ();
+	if (!sp) {
+		return false;
+	}
+
+	return sp->check_read_digest ();
+}
+
+
+Socket::WriteDigestScope::WriteDigestScope (shared_ptr<Socket> socket)
+	: _socket (socket)
+{
+	socket->start_write_digest ();
+}
+
+
+Socket::WriteDigestScope::~WriteDigestScope ()
+{
+	shared_ptr<Socket> sp = _socket.lock ();
+	if (sp) {
+		try {
+			sp->finish_write_digest ();
+		} catch (...) {
+			/* If we can't write our digest, something bad has happened
+			 * so let's just let it happen.
+			 */
+		}
+	}
+}
+
+
+bool
+Socket::check_read_digest ()
+{
+	DCPOMATIC_ASSERT (_read_digester);
+	int const size = _read_digester->size ();
+
+	uint8_t ref[size];
+	_read_digester->get (ref);
+
+	/* Make sure _read_digester is gone before we call read() so that the digest
+	 * isn't itself digested.
+	 */
+	_read_digester.reset ();
+
+	uint8_t actual[size];
+	read (actual, size);
+
+	return memcmp(ref, actual, size) == 0;
+}
+
+void
+Socket::finish_write_digest ()
+{
+	DCPOMATIC_ASSERT (_write_digester);
+	int const size = _write_digester->size();
+
+	uint8_t buffer[size];
+	_write_digester->get (buffer);
+
+	/* Make sure _write_digester is gone before we call write() so that the digest
+	 * isn't itself digested.
+	 */
+	_write_digester.reset ();
+
+	write (buffer, size);
+}
+
diff --git a/src/lib/dcpomatic_socket.h b/src/lib/dcpomatic_socket.h
index 870e7315c..1fa0b046f 100644
--- a/src/lib/dcpomatic_socket.h
+++ b/src/lib/dcpomatic_socket.h
@@ -18,8 +18,11 @@
 
 */
 
+#include "digester.h"
 #include <boost/asio.hpp>
 #include <boost/noncopyable.hpp>
+#include <boost/scoped_ptr.hpp>
+#include <boost/weak_ptr.hpp>
 
 /** @class Socket
  *  @brief A class to wrap a boost::asio::ip::tcp::socket with some things
@@ -46,8 +49,36 @@ public:
 	void read (uint8_t* data, int size);
 	uint32_t read_uint32 ();
 
+	class ReadDigestScope
+	{
+	public:
+		ReadDigestScope (boost::shared_ptr<Socket> socket);
+		bool check ();
+	private:
+		boost::weak_ptr<Socket> _socket;
+	};
+
+	/** After one of these is created everything that is sent from the socket will be
+	 *  added to a digest.  When the DigestScope is destroyed the digest will be sent
+	 *  from the socket.
+	 */
+	class WriteDigestScope
+	{
+	public:
+		WriteDigestScope (boost::shared_ptr<Socket> socket);
+		~WriteDigestScope ();
+	private:
+		boost::weak_ptr<Socket> _socket;
+	};
+
 private:
+	friend class DigestScope;
+
 	void check ();
+	void start_read_digest ();
+	bool check_read_digest ();
+	void start_write_digest ();
+	void finish_write_digest ();
 
 	Socket (Socket const &);
 
@@ -55,4 +86,6 @@ private:
 	boost::asio::deadline_timer _deadline;
 	boost::asio::ip::tcp::socket _socket;
 	int _timeout;
+	boost::scoped_ptr<Digester> _read_digester;
+	boost::scoped_ptr<Digester> _write_digester;
 };
diff --git a/src/lib/digester.cc b/src/lib/digester.cc
index 7bcc77646..452452ba4 100644
--- a/src/lib/digester.cc
+++ b/src/lib/digester.cc
@@ -19,6 +19,7 @@
 */
 
 #include "digester.h"
+#include "dcpomatic_assert.h"
 #include <nettle/md5.h>
 #include <iomanip>
 #include <cstdio>
@@ -67,3 +68,16 @@ Digester::get () const
 
 	return _digest.get ();
 }
+
+void
+Digester::get (uint8_t* buffer) const
+{
+	md5_digest (&_context, MD5_DIGEST_SIZE, buffer);
+}
+
+
+int
+Digester::size () const
+{
+	return MD5_DIGEST_SIZE;
+}
diff --git a/src/lib/digester.h b/src/lib/digester.h
index bec1f6416..6cdaf2331 100644
--- a/src/lib/digester.h
+++ b/src/lib/digester.h
@@ -40,6 +40,10 @@ public:
 
 	std::string get () const;
 
+	void get (uint8_t* buffer) const;
+
+	int size () const;
+
 private:
 	mutable md5_ctx _context;
 	mutable boost::optional<std::string> _digest;