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+//=============================================================================
+//
+//   File : kvi_crypt.cpp
+//   Creation date : Fri Nov 03 2000 02:34:43 CEST by Szymon Stefanek
+//
+//   This file is part of the KVirc irc client distribution
+//   Copyright (C) 1999-2007 Szymon Stefanek (pragma at kvirc dot net)
+//
+//   This program is FREE software. You can redistribute it and/or
+//   modify it under the terms of the GNU General Public License
+//   as published by the Free Software Foundation; either version 2
+//   of the License, or (at your opinion) any later version.
+//
+//   This program is distributed in the HOPE that it will be USEFUL,
+//   but WITHOUT ANY WARRANTY; without even the implied warranty of
+//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//   See the GNU General Public License for more details.
+//
+//   You should have received a copy of the GNU General Public License
+//   along with this program. If not, write to the Free Software Foundation,
+//   Inc. ,51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+//
+//=============================================================================
+
+#define __KVILIB__
+
+#include "kvi_crypt.h"
+#include "kvi_locale.h"
+
+#ifdef COMPILE_ON_WINDOWS
+	#include "kvi_malloc.h"
+#endif
+
+/*
+	@doc: crypt_engines
+	@type:
+		generic
+	@keyterms:
+		cryptography, privacy, private key, text transformation
+	@title:
+		Cryptography and text transformation
+	@short:
+		Crypt/text transformation engines and how to use them
+	@body:
+		[big]Introduction[/big][br]
+		Well , there is a concrete background noise about security around the net.
+		And I've thought that adding a little cryptography support to KVIrc wasn't
+		a bad idea. So I've first comed out with the "crypt engines", that
+		allowed to have secure conversations on channels, queries and dcc chats;
+		then found out that the realized structure was perfect to be "generalized"
+		into "text transformation" support.[br]
+		[big]The concept[/big][br]
+		In few words, the "text transformation" engine is a layer between the user and the
+		IRC connection. You type some text in the input line of a query window (for example),
+		the engine transforms the text in some way and then sends it to the remote target.
+		The trick works also in the reverse way: some data come from the remote target,
+		the engine retransforms the text in some other way and displays it to the local user.[br]
+		The "incoming" transformation is usually the inverse of the "outgoing" one, but it
+		is not mandatory. It will become clear in few sentences that some engines will do no "incoming"
+		transformation at all. The original use of the transformation engines was to crypt the
+		outgoing data and to decrypt the incoming data; anyway, the engines can perform
+		other funky tasks. One of them is remapping the local charset to a "standardized" one
+		when sending text to a channel (or some other target) and doing the inverse map on
+		the way back. A totally "fantastic" usage of this concept could be an "on-the-fly translator";
+		it could translate for example Italian to English while sending to a channel
+		and English to Italian on the way back...the implementation of a such engine is left
+		to the reader as exercise :) Another (maybe less interesting) usage is to
+		colorize the outgoing text, or transform it
+		in a way that it is still readable but has a different look. This engine
+		would not require a back transformation (so no "decrypt stage"). A "symmetric"
+		idea could be an engine that strips the color codes from the incoming text: this
+		engine would not require a "crypting" stage.[br]
+
+		[big]The name of this stuf[/big][br]
+		Initially all this stuff was named "cryptography support".
+		Then the "cryptography" comed out to be not "enough" to describe
+		the framework, so "text transformation" is a more generic term.
+		Anyway, both terms were used in the documentation and the source.
+		Just as example, the "text transformation engine" is called
+		KviCryptEngine in the sources. So actually the terms "crypt"
+		and "text transformations" refer to the "same thing".
+		You will often find the term "encrypt" standing for "outgoing text
+		transformation" and "decrypt" standing for "incoming text transformation".[br]
+
+		[big]Yes, but why cryptography (on IRC) ?[/big][br]
+		Because it MAY be useful. More than once people have asked me to add some
+		crypting support to the dcc chats. Yes , I know that there are other
+		"secure communication" tools , but actually I can't find one that is able to
+		implement a "secure real time conversation". And what about a MULTIPLE real
+		time secure conversation ? This can be done on an IRC channel now.[br]
+
+		[big]The working things[/big][br]
+		KVIrc can use a text transformation engine on irc channels, in the queries
+		and the dcc chats. At the time I am writing, only the [module:rijndael]Rijndael[/module] crypt engine
+		is available: this is a private key encryption algorithm that assures
+		a "pretty good" security level. More engines will be surely available
+		at the time of the 3.0.0 release of KVIrc. The engines
+		can be activated by the dedicated dialog that can be accessed from the "button bar"
+		of the window. Once an engine has been enabled all the text that you type
+		in the input line (that is not a command obviously) is encrypted
+		and sent to the remote endpoint. If you want to sent a non crypted message
+		while an engine is working you can use the CTRL+P escape: by placing
+		that character as the FIRST CHARACTER of the line you will avoid crypting.
+		Every engine has different capabilities: some can both encrypt
+		and decrypt, other perform only half of the operations. Some engines
+		need a key (the crypt engines obviously), or two keys (you can specify
+		one for the outgoing data and one for the incoming). You can specify
+		all these options in the crypt/text transformation dialog.[br]
+		Obviously (with the current implementations) all the conversation endpoints
+		must agree on the engine (or better algorithm) used and on the key(s).
+		The key is user specified, so you have to find a secure way to negotiate
+		it with your communication engpoints. If you can meet the persons in the "real life",
+		this is the best way to exchange the keys, otherwise you can use mail & pgp.
+		Yes, this is a "miss" of the crypt protocol: it is missing a public key handshake.[br]
+
+		[big]The first test[/big][br]
+		A cool way to test a crypting engine is to use a "self query": connect to
+		any irc server, and execute [cmd]query[/cmd] <yournickname>; a query window
+		with you both as source and target will popup; activate a crypt engine
+		and enable both encryption and decryption; specify the same key for
+		bot directions and then type some text in the input line: you will see
+		the message twice: one is "your local text" and the other is the server routed one.
+		Then you can try to activate encryption only and leaving decryption disabled:
+		you will see how the text would appear to a possible "man in the middle".
+		You can also try to use different keys for encrypting and decrypting,
+		and play with the CTRL+P escape.[br]
+
+		[big]The protocol[/big][br]
+		Well, there is no protocol actually , only the existing implementations , that
+		can be accessed by anyone that want to reproduce them. There are only some
+		points relating to the crypting engines that need to be cleared:[br]
+		The crypted text must be suitable to be sent thru an IRC connection;
+		this means that some characters can not appear in the crypted text (e.g. CR,LF,NULL....).
+		KVIrc solves it in a simple way: the crypted binary data is encoded,
+		either as hexadecimal numeric string or in base64.[br]
+		An escape character has been defined to identify messages that are "crypted" from the
+		ones that are not: this character has ascii code 30 (decimal).[br]
+		The encoding is used in private messages only and has the following format:[br]
+		PRIVMSG <target> :<escape_char_ascii_30><encrypted message>[br]
+		ASCII 30 does not correspond to any widely used escape sequence and allows
+		mixing encrypted and plain text messages in a conversation...Well, this is not
+		so pretty but you can exchange crypted messages with one or two friends while
+		talking on a normal IRC channel: nobody else than your friends will be able
+		to understand the message; others will see senseless sequences of characters.
+		You will be still able to read the unencrypted messages of the other people
+		on the channel.[br] The escape character is not needed if the engine
+		performs non-crypting tasks: a charset mapper will produce text that
+		is meant to be readed by anyone on the channel, a text colorizer will
+		act in a similar way too. So the escape character is used for the "crypting"
+		engines only.
+
+		[big]An idea for the future implementations[/big][br]
+		A "public key" handshake protocol could be implemented.
+*/
+
+
+	KviCryptEngine::KviCryptEngine()
+	{
+#ifdef COMPILE_CRYPT_SUPPORT
+		setLastError(__tr2qs("Invalid crypt engine"));
+		m_iMaxEncryptLen = -1; // unlimited
+		m_deallocFunc = 0;
+#endif //COMPILE_CRYPT_SUPPORT
+	}
+
+	KviCryptEngine::~KviCryptEngine()
+	{
+	}
+
+#ifdef COMPILE_CRYPT_SUPPORT
+
+	bool KviCryptEngine::init(const char *,int,const char *,int)
+	{
+		return false;
+	}
+
+	KviCryptEngine::EncryptResult KviCryptEngine::encrypt(const char *,KviStr &)
+	{
+//		debug("Pure virtual KviCryptEngine::encrypt() called");
+		return EncryptError;
+	}
+
+	KviCryptEngine::DecryptResult KviCryptEngine::decrypt(const char *,KviStr &)
+	{
+//		debug("Pure virtual KviCryptEngine::decrypt() called");
+		return DecryptError;
+	}
+
+
+	KviCryptEngineManager::KviCryptEngineManager()
+	{
+		m_pEngineDict = new KviPointerHashTable<QString,KviCryptEngineDescription>;
+		m_pEngineDict->setAutoDelete(true);
+	}
+
+	KviCryptEngineManager::~KviCryptEngineManager()
+	{
+		delete m_pEngineDict;
+	}
+
+	void KviCryptEngineManager::registerEngine(KviCryptEngineDescription * d)
+	{
+		m_pEngineDict->replace(d->szName,d);
+	}
+
+	void KviCryptEngineManager::unregisterEngine(const QString &szName)
+	{
+		m_pEngineDict->remove(szName);
+	}
+
+	void KviCryptEngineManager::unregisterEngines(void * providerHandle)
+	{
+		KviPointerHashTableIterator<QString,KviCryptEngineDescription> it(*m_pEngineDict);
+		while(it.current())
+		{
+			if(it.current()->providerHandle == providerHandle)
+				m_pEngineDict->remove(it.currentKey());
+			else
+				++it;
+		}
+	}
+
+	KviCryptEngine * KviCryptEngineManager::allocateEngine(const QString &szName)
+	{
+		KviCryptEngineDescription * d =  m_pEngineDict->find(szName);
+		if(!d)return 0;
+		KviCryptEngine * e = d->allocFunc();
+		if(!e)return 0;
+		e->m_deallocFunc = d->deallocFunc; // remember the dealloc func from now on
+		return e;
+	}
+
+	void KviCryptEngineManager::deallocateEngine(KviCryptEngine * e)
+	{
+		if(!e)return;
+		crypt_engine_deallocator_func deallocFunc = e->m_deallocFunc;
+		deallocFunc(e);
+	}
+
+#endif //COMPILE_CRYPT_SUPPORT