src/transport/PairingSession.h

/*
 *
 *    Copyright (c) 2021 Project CHIP Authors
 *    All rights reserved.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

/**
 *    @file
 *      This file defines a common interface to access various types of secure
 *      pairing sessions (e.g. PASE, CASE)
 *
 */

#pragma once

#include <lib/core/CHIPError.h>
#include <messaging/ExchangeContext.h>
#include <protocols/secure_channel/Constants.h>
#include <protocols/secure_channel/StatusReport.h>
#include <transport/CryptoContext.h>

namespace chip {

class DLL_EXPORT PairingSession
{
public:
    PairingSession() {}
    virtual ~PairingSession() {}

    // TODO: the session should know which peer we are trying to connect to at start
    // mPeerNodeId should be const and assigned at the construction, such that GetPeerNodeId will never return kUndefinedNodeId, and
    // SetPeerNodeId is not necessary.
    NodeId GetPeerNodeId() const { return mPeerNodeId; }

    // TODO: the local key id should be allocateed at start
    // mLocalSessionId should be const and assigned at the construction, such that GetLocalSessionId will always return a valid key
    // id , and SetLocalSessionId is not necessary.
    uint16_t GetLocalSessionId() const { return mLocalSessionId; }
    bool IsValidLocalSessionId() const { return mLocalSessionId != kInvalidKeyId; }

    uint16_t GetPeerSessionId() const
    {
        VerifyOrDie(mPeerSessionId.HasValue());
        return mPeerSessionId.Value();
    }
    bool IsValidPeerSessionId() const { return mPeerSessionId.HasValue(); }

    // TODO: decouple peer address into transport, such that pairing session do not need to handle peer address
    const Transport::PeerAddress & GetPeerAddress() const { return mPeerAddress; }
    Transport::PeerAddress & GetPeerAddress() { return mPeerAddress; }

    /**
     * @brief
     *   Derive a secure session from the paired session. The API will return error
     *   if called before pairing is established.
     *
     * @param session     Referene to the secure session that will be
     *                    initialized once pairing is complete
     * @param role        Role of the new session (initiator or responder)
     * @return CHIP_ERROR The result of session derivation
     */
    virtual CHIP_ERROR DeriveSecureSession(CryptoContext & session, CryptoContext::SessionRole role) = 0;

    /**
     * @brief
     *   Get the value of peer session counter which is synced during session establishment
     */
    virtual uint32_t GetPeerCounter()
    {
        // TODO(#6652): This is a stub implementation, should be replaced by the real one when CASE and PASE is completed
        return LocalSessionMessageCounter::kInitialValue;
    }

    virtual const char * GetI2RSessionInfo() const = 0;

    virtual const char * GetR2ISessionInfo() const = 0;

protected:
    // TODO - Move EstimateTLVStructOverhead to CHIPTLV header file
    static constexpr size_t EstimateTLVStructOverhead()
    {
        // The struct itself has a control byte and an end-of-struct marker.
        return 2;
    }

    template <typename... FieldSizes>
    static constexpr size_t EstimateTLVStructOverhead(size_t firstFieldSize, FieldSizes... otherFields)
    {
        // Estimate 4 bytes of overhead per field.  This can happen for a large
        // octet string field: 1 byte control, 1 byte context tag, 2 bytes
        // length.
        return firstFieldSize + 4 + EstimateTLVStructOverhead(otherFields...);
    }

    void SetPeerNodeId(NodeId peerNodeId) { mPeerNodeId = peerNodeId; }
    void SetPeerSessionId(uint16_t id) { mPeerSessionId.SetValue(id); }
    void SetLocalSessionId(uint16_t id) { mLocalSessionId = id; }
    void SetPeerAddress(const Transport::PeerAddress & address) { mPeerAddress = address; }
    virtual void OnSuccessStatusReport() {}
    virtual CHIP_ERROR OnFailureStatusReport(Protocols::SecureChannel::GeneralStatusCode generalCode, uint16_t protocolCode)
    {
        return CHIP_ERROR_INTERNAL;
    }

    void SendStatusReport(Messaging::ExchangeContext * exchangeCtxt, uint16_t protocolCode)
    {
        Protocols::SecureChannel::GeneralStatusCode generalCode = (protocolCode == Protocols::SecureChannel::kProtocolCodeSuccess)
            ? Protocols::SecureChannel::GeneralStatusCode::kSuccess
            : Protocols::SecureChannel::GeneralStatusCode::kFailure;
        uint32_t protocolId = Protocols::SecureChannel::Id.ToFullyQualifiedSpecForm();

        ChipLogDetail(SecureChannel, "Sending status report. Protocol code %d, exchange %d", protocolCode,
                      exchangeCtxt->GetExchangeId());

        Protocols::SecureChannel::StatusReport statusReport(generalCode, protocolId, protocolCode);

        Encoding::LittleEndian::PacketBufferWriter bbuf(System::PacketBufferHandle::New(statusReport.Size()));
        statusReport.WriteToBuffer(bbuf);

        System::PacketBufferHandle msg = bbuf.Finalize();
        VerifyOrReturn(!msg.IsNull(), ChipLogError(SecureChannel, "Failed to allocate status report message"));

        CHIP_ERROR err = exchangeCtxt->SendMessage(Protocols::SecureChannel::MsgType::StatusReport, std::move(msg));
        if (err != CHIP_NO_ERROR)
        {
            ChipLogError(SecureChannel, "Failed to send status report message. %s", ErrorStr(err));
        }
    }

    CHIP_ERROR HandleStatusReport(System::PacketBufferHandle && msg, bool successExpected)
    {
        Protocols::SecureChannel::StatusReport report;
        CHIP_ERROR err = report.Parse(std::move(msg));
        ReturnErrorOnFailure(err);
        VerifyOrReturnError(report.GetProtocolId() == Protocols::SecureChannel::Id.ToFullyQualifiedSpecForm(),
                            CHIP_ERROR_INVALID_ARGUMENT);

        if (report.GetGeneralCode() == Protocols::SecureChannel::GeneralStatusCode::kSuccess &&
            report.GetProtocolCode() == Protocols::SecureChannel::kProtocolCodeSuccess && successExpected)
        {
            OnSuccessStatusReport();
        }
        else
        {
            err = OnFailureStatusReport(report.GetGeneralCode(), report.GetProtocolCode());
        }

        return err;
    }

    // TODO: remove Clear, we should create a new instance instead reset the old instance.
    void Clear()
    {
        mPeerNodeId  = kUndefinedNodeId;
        mPeerAddress = Transport::PeerAddress::Uninitialized();
        mPeerSessionId.ClearValue();
        mLocalSessionId = kInvalidKeyId;
    }

private:
    NodeId mPeerNodeId = kUndefinedNodeId;

    // TODO: the local key id should be allocateed at start
    // then we can remove kInvalidKeyId
    static constexpr uint16_t kInvalidKeyId = UINT16_MAX;
    uint16_t mLocalSessionId                = kInvalidKeyId;

    // TODO: decouple peer address into transport, such that pairing session do not need to handle peer address
    Transport::PeerAddress mPeerAddress = Transport::PeerAddress::Uninitialized();

    Optional<uint16_t> mPeerSessionId;
};

} // namespace chip