path: root/modules/ircv3_sts.cpp

/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2017, 2019-2023 Sadie Powell <sadie@sadiepowell.dev>
 *
 * 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 "inspircd.h"
#include "modules/cap.h"
#include "modules/tls.h"

class STSCap final
	: public Cap::Capability
{
private:
	std::string host;
	std::string plaintextpolicy;
	std::string plaintextwspolicy;
	std::string securepolicy;
	TLS::API tlsapi;

	bool OnList(LocalUser* user) override
	{
		// Don't send the cap to clients that only support cap-3.1.
		if (GetProtocol(user) == Cap::CAP_LEGACY)
			return false;

		// Don't send the cap to clients in a class which has STS disabled.
		if (!user->GetClass()->config->getBool("usests", true))
			return false;

		// Check whether we have a value for this hook type.
		auto* value = GetValue(user);
		if (!value || value->empty())
			return false; // No sts for this (probably websocket) hook.

		// Plaintext listeners have their own policy.
		const auto* tlshook = TLS::GetHook(user->io->GetSocket());
		if (!tlshook)
			return true;

		// If no hostname has been provided for the connection, an STS persistence policy SHOULD NOT be advertised.
		std::string snihost;
		if (!tlshook->GetServerName(snihost))
			return false;

		// Before advertising an STS persistence policy over a secure connection, servers SHOULD verify whether the
		// hostname provided by clients, for example, via TLS Server Name Indication (SNI), has been whitelisted by
		// administrators in the server configuration.
		return InspIRCd::Match(snihost, host, ascii_case_insensitive_map);
	}

	bool OnRequest(LocalUser* user, bool adding) override
	{
		// Clients MUST NOT request this capability with CAP REQ. Servers MAY reply with a CAP NAK message if a
		// client requests this capability.
		return false;
	}

	const std::string* GetValue(LocalUser* user) const override
	{
		auto* ios = user->io->GetSocket();
		if (TLS::GetHook(ios))
			return &securepolicy; // Normal SSL connection.

		if (tlsapi && tlsapi->GetCertificate(user))
			return &securepolicy; // Proxied SSL connection.

		auto* ioh = ios->GetIOHook();
		return ioh && insp::casemapped_equals(ioh->GetHookProvider()->service_name, "websocket")
			? &plaintextwspolicy // Plain text websocket connection.
			: &plaintextpolicy;  // Plain text connection.
	}

public:
	STSCap(const WeakModulePtr& mod)
		: Cap::Capability(mod, "sts")
		, tlsapi(mod)
	{
		DisableAutoRegister();
	}

	~STSCap() override
	{
		// TODO: Send duration=0 when STS vanishes.
	}

	void SetPolicy(const std::string& newhost, unsigned long duration, in_port_t port, in_port_t wsport, bool preload)
	{
		// To enforce an STS upgrade policy, servers MUST send this key to insecurely connected clients. Servers
		// MAY send this key to securely connected clients, but it will be ignored.
		std::string newplaintextpolicy("port=");
		newplaintextpolicy.append(ConvToStr(port));

		std::string newplaintextwspolicy;
		if (wsport)
			newplaintextwspolicy.append("port=").append(ConvToStr(wsport));

		// To enforce an STS persistence policy, servers MUST send this key to securely connected clients. Servers
		// MAY send this key to all clients, but insecurely connected clients MUST ignore it.
		std::string newsecurepolicy("duration=");
		newsecurepolicy.append(ConvToStr(duration));

		// Servers MAY send this key to all clients, but insecurely connected clients MUST ignore it.
		if (preload)
			newsecurepolicy.append(",preload");

		// Apply the new policy.
		bool changed = false;
		if (!insp::casemapped_equals(host, newhost))
		{
			ServerInstance->Logs.Debug(MODNAME, "Changing STS SNI hostname from \"{}\" to \"{}\"", host, newhost);
			host = newhost;
			changed = true;
		}

		if (plaintextpolicy != newplaintextpolicy)
		{
			ServerInstance->Logs.Debug(MODNAME, "Changing plaintext STS policy from \"{}\" to \"{}\"", plaintextpolicy, newplaintextpolicy);
			plaintextpolicy.swap(newplaintextpolicy);
			changed = true;
		}

		if (plaintextwspolicy != newplaintextwspolicy)
		{
			ServerInstance->Logs.Debug(MODNAME, "Changing plaintext WebSocket STS policy from \"{}\" to \"{}\"", plaintextwspolicy, newplaintextwspolicy);
			plaintextwspolicy.swap(newplaintextwspolicy);
			changed = true;
		}

		if (securepolicy != newsecurepolicy)
		{
			ServerInstance->Logs.Debug(MODNAME, "Changing secure STS policy from \"{}\" to \"{}\"", securepolicy, newsecurepolicy);
			securepolicy.swap(newsecurepolicy);
			changed = true;
		}

		// If the policy has changed then notify all clients via cap-notify.
		if (changed)
			NotifyValueChange();
	}
};

class ModuleIRCv3STS final
	: public Module
{
private:
	STSCap cap;

	// The IRCv3 STS specification requires that the server is listening using TLS using a valid certificate.
	static bool HasValidSSLPort(in_port_t port, bool websocket)
	{
		for (const auto* ls : ServerInstance->Ports)
		{
			ServerInstance->Logs.Debug(MODNAME, "HasValidSSLPort({}, {}): checking {} at {}",
				port, websocket, ls->bind_sa.str(), ls->bind_tag->source.str());

			// Is this listener on the right port?
			const auto saport = ls->bind_sa.port();
			if (saport != port)
			{
				ServerInstance->Logs.Debug(MODNAME, "BAD: wrong port.");
				continue;
			}

			const auto bindhook = ls->bind_tag->getString("hook");
			if (insp::casemapped_equals(bindhook, "websocket"))
			{
				if (!websocket)
				{
					ServerInstance->Logs.Debug(MODNAME, "BAD: websocket hook when we want a non-websocket hook.");
					continue; // Not a websocket connection.
				}

				// Port has a websocket hook and we want a websocket hook.
			}
			else if (websocket)
			{
				ServerInstance->Logs.Debug(MODNAME, "BAD: non-websocket hook when we want a websocket hook.");
				continue;
			}
			else if (!bindhook.empty())
			{
				if (!ls->bind_tag->getBool("sslhook"))
				{
					ServerInstance->Logs.Debug(MODNAME, "BAD: {} hook and sslhook is not set.", bindhook);
					continue; // Not explicitly marked as a SSL hook.
				}

				ServerInstance->Logs.Debug(MODNAME, "GOOD: {} hook and sslhook is set.", bindhook);
				return true; // Listener is marked as providing SSL via a proxy like HAProxy.
			}

			// Is this listener using TLS?
			if (ls->bind_tag->getString("sslprofile").empty())
			{
				ServerInstance->Logs.Debug(MODNAME, "BAD: no sslprofile.");
				continue;
			}

			// TODO: Add a way to check if a listener's TLS cert is CA-verified.
			ServerInstance->Logs.Debug(MODNAME, "GOOD: passed all checks.");
			return true;
		}

		ServerInstance->Logs.Debug(MODNAME, "BAD: nothing passed checks.");
		return false;
	}

public:
	ModuleIRCv3STS()
		: Module(VF_VENDOR | VF_OPTCOMMON, "Adds support for the IRCv3 Strict Transport Security specification.")
		, cap(weak_from_this())
	{
	}

	void ReadConfig(ConfigStatus& status) override
	{
		// TODO: Multiple SNI profiles
		const auto& tag = ServerInstance->Config->ConfValue("sts");
		if (tag == ServerInstance->Config->EmptyTag)
			throw ModuleException(weak_from_this(), "You must define a STS policy!");

		const std::string host = tag->getString("host");
		if (host.empty())
			throw ModuleException(weak_from_this(), "<sts:host> must contain a hostname, at " + tag->source.str());

		const auto port = tag->getNum<in_port_t>("port", 6697, 1);
		if (!HasValidSSLPort(port, false))
			throw ModuleException(weak_from_this(), "<sts:port> must be a TLS port, at " + tag->source.str());

		const auto wsport = tag->getNum<in_port_t>("wsport", 0);
		if (wsport && !HasValidSSLPort(wsport, true))
			throw ModuleException(weak_from_this(), "<sts:wsport> must be a TLS WebSocket port, at " + tag->source.str());

		unsigned long duration = tag->getDuration("duration", 5*60, 60);
		bool preload = tag->getBool("preload");
		cap.SetPolicy(host, duration, port, wsport, preload);

		if (!cap.IsRegistered())
			ServerInstance->Modules.AddService(cap);
	}
};

MODULE_INIT(ModuleIRCv3STS)