/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2021 Dominic Hamon
 *   Copyright (C) 2018-2023 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2018 linuxdaemon <linuxdaemon.irc@gmail.com>
 *   Copyright (C) 2014, 2020 Daniel Vassdal <shutter@canternet.org>
 *   Copyright (C) 2014, 2016 Attila Molnar <attilamolnar@hush.com>
 *
 * This file is part of InspIRCd.  InspIRCd 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, version 2.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */


#include <cmath>

#include "inspircd.h"
#include "modules/hash.h"

// Format:
// Iterations:B64(Hash):B64(Salt)
// E.g.
// 10200:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA:BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
class PBKDF2Hash final
{
public:
	unsigned long iterations;
	size_t length;
	std::string salt;
	std::string hash;

	PBKDF2Hash(unsigned long itr, size_t dkl, const std::string& slt, const std::string& hsh = "")
		: iterations(itr)
		, length(dkl)
		, salt(slt)
		, hash(hsh)
	{
	}

	PBKDF2Hash(const std::string& data)
	{
		irc::sepstream ss(data, ':');
		std::string tok;

		ss.GetToken(tok);
		this->iterations = ConvToNum<unsigned int>(tok);

		ss.GetToken(tok);
		this->hash = Base64::Decode(tok);

		ss.GetToken(tok);
		this->salt = Base64::Decode(tok);

		this->length = this->hash.length();
	}

	std::string ToString() const
	{
		if (!IsValid())
			return "";
		return ConvToStr(this->iterations) + ":" + Base64::Encode(this->hash) + ":" + Base64::Encode(this->salt);
	}

	bool IsValid() const
	{
		return this->iterations && this->length && !this->salt.empty() && !this->hash.empty();
	}
};

class PBKDF2Provider final
	: public HashProvider
{
public:
	HashProvider* provider;
	unsigned long iterations;
	size_t dkey_length;

	std::string PBKDF2(const std::string& pass, const std::string& salt, unsigned long itr = 0, size_t dkl = 0) const
	{
		size_t blocks = std::ceil((double)dkl / provider->out_size);

		std::string output;
		std::string tmphash;
		std::string salt_block = salt;
		for (size_t block = 1; block <= blocks; block++)
		{
			char salt_data[4];
			for (size_t i = 0; i < sizeof(salt_data); i++)
				salt_data[i] = block >> (24 - i * 8) & 0x0F;

			salt_block.erase(salt.length());
			salt_block.append(salt_data, sizeof(salt_data));

			std::string blockdata = provider->hmac(pass, salt_block);
			std::string lasthash = blockdata;
			for (size_t iter = 1; iter < itr; iter++)
			{
				tmphash = provider->hmac(pass, lasthash);
				for (size_t i = 0; i < provider->out_size; i++)
					blockdata[i] ^= tmphash[i];

				lasthash.swap(tmphash);
			}
			output += blockdata;
		}

		output.erase(dkl);
		return output;
	}

	std::string GenerateRaw(const std::string& data) override
	{
		PBKDF2Hash hs(this->iterations, this->dkey_length, ServerInstance->GenRandomStr(dkey_length, false));
		hs.hash = PBKDF2(data, hs.salt, this->iterations, this->dkey_length);
		return hs.ToString();
	}

	bool Compare(const std::string& input, const std::string& hash) override
	{
		PBKDF2Hash hs(hash);
		if (!hs.IsValid())
			return false;

		std::string cmp = PBKDF2(input, hs.salt, hs.iterations, hs.length);
		return InspIRCd::TimingSafeCompare(cmp, hs.hash);
	}

	std::string ToPrintable(const std::string& raw) override
	{
		return raw;
	}

	PBKDF2Provider(Module* mod, HashProvider* hp)
		: HashProvider(mod, "pbkdf2-hmac-" + hp->name.substr(hp->name.find('/') + 1))
		, provider(hp)
	{
		DisableAutoRegister();
	}
};

struct ProviderConfig final
{
	unsigned long dkey_length;
	unsigned long iterations;
};

typedef std::map<std::string, ProviderConfig> ProviderConfigMap;

class ModulePBKDF2 final
	: public Module
{
	std::vector<PBKDF2Provider*> providers;
	ProviderConfig globalconfig;
	ProviderConfigMap providerconfigs;

	ProviderConfig GetConfigForProvider(const std::string& name) const
	{
		ProviderConfigMap::const_iterator it = providerconfigs.find(name);
		if (it == providerconfigs.end())
			return globalconfig;

		return it->second;
	}

	void ConfigureProviders()
	{
		for (auto* pi : providers)
		{
			ProviderConfig config = GetConfigForProvider(pi->name);
			pi->iterations = config.iterations;
			pi->dkey_length = config.dkey_length;
		}
	}

	void ReadConfig(ConfigStatus& status) override
	{
		// First set the common values
		const auto& tag = ServerInstance->Config->ConfValue("pbkdf2");
		ProviderConfig newglobal;
		newglobal.iterations = tag->getNum<unsigned long>("iterations", 12288, 1);
		newglobal.dkey_length = tag->getNum<size_t>("length", 32, 1, 1024);

		// Then the specific values
		ProviderConfigMap newconfigs;
		for (const auto& [_, ptag] : ServerInstance->Config->ConfTags("pbkdf2prov"))
		{
			std::string hash_name = "hash/" + ptag->getString("hash");
			ProviderConfig& config = newconfigs[hash_name];

			config.iterations = ptag->getNum<unsigned long>("iterations", newglobal.iterations, 1);
			config.dkey_length = ptag->getNum<size_t>("length", newglobal.dkey_length, 1, 1024);
		}

		// Config is valid, apply it
		providerconfigs.swap(newconfigs);
		std::swap(globalconfig, newglobal);
		ConfigureProviders();
	}

public:
	ModulePBKDF2()
		: Module(VF_VENDOR, "Allows other modules to generate PBKDF2 hashes.")
	{
	}

	~ModulePBKDF2() override
	{
		stdalgo::delete_all(providers);
	}

	void init() override
	{
		// Let ourself know about any existing services.
		for (const auto& [_, service] : ServerInstance->Modules.DataProviders)
			OnServiceAdd(*service);
	}

	void OnServiceAdd(ServiceProvider& provider) override
	{
		// Check if it's a hash provider
		if (provider.name.compare(0, 5, "hash/"))
			return;

		HashProvider* hp = static_cast<HashProvider*>(&provider);
		if (hp->IsKDF())
			return;

		auto* prov = new PBKDF2Provider(this, hp);
		providers.push_back(prov);
		ServerInstance->Modules.AddService(*prov);

		ConfigureProviders();
	}

	void OnServiceDel(ServiceProvider& prov) override
	{
		for (std::vector<PBKDF2Provider*>::iterator i = providers.begin(); i != providers.end(); ++i)
		{
			PBKDF2Provider* item = *i;
			if (item->provider != &prov)
				continue;

			ServerInstance->Modules.DelService(*item);
			delete item;
			providers.erase(i);
			break;
		}
	}
};

MODULE_INIT(ModulePBKDF2)