i2pd/core/Garlic.cpp

#include <inttypes.h>
#include "util/I2PEndian.h"
#include <map>
#include <string>
#include "RouterContext.h"
#include "I2NPProtocol.h"
#include "tunnel/Tunnel.h"
#include "tunnel/TunnelPool.h"
#include "util/Timestamp.h"
#include "Destination.h"
#include "Garlic.h"

namespace i2p
{
namespace garlic
{
    GarlicRoutingSession::GarlicRoutingSession (GarlicDestination * owner, 
        std::shared_ptr<const i2p::data::RoutingDestination> destination, int numTags, bool attachLeaseSet):
        m_Owner (owner), m_Destination (destination), m_NumTags (numTags), 
        m_LeaseSetUpdateStatus (attachLeaseSet ? eLeaseSetUpdated : eLeaseSetDoNotSend)
    {
        // create new session tags and session key
        m_Rnd.GenerateBlock (m_SessionKey, 32);
        m_Encryption.SetKey (m_SessionKey);
    }   

    GarlicRoutingSession::GarlicRoutingSession (const uint8_t * sessionKey, const SessionTag& sessionTag):
        m_Owner (nullptr), m_Destination (nullptr), m_NumTags (1), m_LeaseSetUpdateStatus (eLeaseSetDoNotSend)
    {
        memcpy (m_SessionKey, sessionKey, 32);
        m_Encryption.SetKey (m_SessionKey);
        m_SessionTags.push_back (sessionTag);
        m_SessionTags.back ().creationTime = i2p::util::GetSecondsSinceEpoch ();
    }   

    GarlicRoutingSession::~GarlicRoutingSession ()
    {   
        for (auto it: m_UnconfirmedTagsMsgs)    
            delete it.second;
        m_UnconfirmedTagsMsgs.clear ();
    }
    
    GarlicRoutingSession::UnconfirmedTags * GarlicRoutingSession::GenerateSessionTags ()
    {
        auto tags = new UnconfirmedTags (m_NumTags);
        tags->tagsCreationTime = i2p::util::GetSecondsSinceEpoch ();        
        for (int i = 0; i < m_NumTags; i++)
        {
            m_Rnd.GenerateBlock (tags->sessionTags[i], 32);
            tags->sessionTags[i].creationTime = tags->tagsCreationTime;
        }           
        return tags;    
    }

    void GarlicRoutingSession::MessageConfirmed (uint32_t msgID)
    {
        TagsConfirmed (msgID);
        if (msgID == m_LeaseSetUpdateMsgID)
        {   
            m_LeaseSetUpdateStatus = eLeaseSetUpToDate;
            LogPrint (eLogInfo, "LeaseSet update confirmed");
        }   
        else
            CleanupExpiredTags ();
    }   
        
    void GarlicRoutingSession::TagsConfirmed (uint32_t msgID) 
    { 
        auto it = m_UnconfirmedTagsMsgs.find (msgID);   
        if (it != m_UnconfirmedTagsMsgs.end ())
        {
            uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
            UnconfirmedTags * tags = it->second;
            if (ts < tags->tagsCreationTime + OUTGOING_TAGS_EXPIRATION_TIMEOUT)
            {   
                for (int i = 0; i < tags->numTags; i++)
                    m_SessionTags.push_back (tags->sessionTags[i]);
            }   
            m_UnconfirmedTagsMsgs.erase (it);
            delete tags;
        }
    }

    bool GarlicRoutingSession::CleanupExpiredTags ()
    {
        uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
        for (auto it = m_SessionTags.begin (); it != m_SessionTags.end ();)
        {
            if (ts >= it->creationTime + OUTGOING_TAGS_EXPIRATION_TIMEOUT)
                it = m_SessionTags.erase (it);
            else 
                it++;
        }
        // delete expired unconfirmed tags
        for (auto it = m_UnconfirmedTagsMsgs.begin (); it != m_UnconfirmedTagsMsgs.end ();)
        {
            if (ts >= it->second->tagsCreationTime + OUTGOING_TAGS_EXPIRATION_TIMEOUT)
            {
                if (m_Owner)
                    m_Owner->RemoveCreatedSession (it->first);
                delete it->second;
                it = m_UnconfirmedTagsMsgs.erase (it);
            }   
            else
                it++;
        }   
        return !m_SessionTags.empty () || m_UnconfirmedTagsMsgs.empty ();
    }

    std::shared_ptr<I2NPMessage> GarlicRoutingSession::WrapSingleMessage (std::shared_ptr<const I2NPMessage> msg)
    {
        auto m = ToSharedI2NPMessage(NewI2NPMessage ());
        m->Align (12); // in order to get buf aligned to 16 (12 + 4)
        size_t len = 0;
        uint8_t * buf = m->GetPayload () + 4; // 4 bytes for length

        // find non-expired tag
        bool tagFound = false;  
        SessionTag tag; 
        if (m_NumTags > 0)
        {   
            uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
            while (!m_SessionTags.empty ())
            {
                if (ts < m_SessionTags.front ().creationTime + OUTGOING_TAGS_EXPIRATION_TIMEOUT)
                {
                    tag = m_SessionTags.front ();
                    m_SessionTags.pop_front (); // use same tag only once
                    tagFound = true;
                    break;
                }   
                else
                    m_SessionTags.pop_front (); // remove expired tag
            }
        }   
        // create message
        if (!tagFound) // new session
        {
            LogPrint ("No garlic tags available. Use ElGamal");
            if (!m_Destination)
            {
                LogPrint ("Can't use ElGamal for unknown destination");
                return nullptr;
            }
            // create ElGamal block
            ElGamalBlock elGamal;
            memcpy (elGamal.sessionKey, m_SessionKey, 32); 
            m_Rnd.GenerateBlock (elGamal.preIV, 32); // Pre-IV
            uint8_t iv[32]; // IV is first 16 bytes
            CryptoPP::SHA256().CalculateDigest(iv, elGamal.preIV, 32); 
            m_Destination->GetElGamalEncryption ()->Encrypt ((uint8_t *)&elGamal, sizeof(elGamal), buf, true);          
            m_Encryption.SetIV (iv);
            buf += 514;
            len += 514; 
        }
        else // existing session
        {   
            // session tag
            memcpy (buf, tag, 32);  
            uint8_t iv[32]; // IV is first 16 bytes
            CryptoPP::SHA256().CalculateDigest(iv, tag, 32);
            m_Encryption.SetIV (iv);
            buf += 32;
            len += 32;      
        }   
        // AES block
        len += CreateAESBlock (buf, msg);
        htobe32buf (m->GetPayload (), len);
        m->len += len + 4;
        m->FillI2NPMessageHeader (eI2NPGarlic);
        return m;
    }   

    size_t GarlicRoutingSession::CreateAESBlock (uint8_t * buf, std::shared_ptr<const I2NPMessage> msg)
    {
        size_t blockSize = 0;
        bool createNewTags = m_Owner && m_NumTags && ((int)m_SessionTags.size () <= m_NumTags*2/3);
        UnconfirmedTags * newTags = createNewTags ? GenerateSessionTags () : nullptr;
        htobuf16 (buf, newTags ? htobe16 (newTags->numTags) : 0); // tag count
        blockSize += 2;
        if (newTags) // session tags recreated
        {   
            for (int i = 0; i < newTags->numTags; i++)
            {
                memcpy (buf + blockSize, newTags->sessionTags[i], 32); // tags
                blockSize += 32;
            }
        }   
        uint32_t * payloadSize = (uint32_t *)(buf + blockSize);
        blockSize += 4;
        uint8_t * payloadHash = buf + blockSize;
        blockSize += 32;
        buf[blockSize] = 0; // flag
        blockSize++;
        size_t len = CreateGarlicPayload (buf + blockSize, msg, newTags);
        htobe32buf (payloadSize, len);
        CryptoPP::SHA256().CalculateDigest(payloadHash, buf + blockSize, len);
        blockSize += len;
        size_t rem = blockSize % 16;
        if (rem)
            blockSize += (16-rem); //padding
        m_Encryption.Encrypt(buf, blockSize, buf);
        return blockSize;
    }   

    size_t GarlicRoutingSession::CreateGarlicPayload (uint8_t * payload, std::shared_ptr<const I2NPMessage> msg, UnconfirmedTags * newTags)
    {
        uint64_t ts = i2p::util::GetMillisecondsSinceEpoch () + 5000; // 5 sec
        uint32_t msgID = m_Rnd.GenerateWord32 ();   
        size_t size = 0;
        uint8_t * numCloves = payload + size;
        *numCloves = 0;
        size++;

        if (m_Owner)
        {   
            // resubmit non-confirmed LeaseSet
            if (m_LeaseSetUpdateStatus == eLeaseSetSubmitted && 
                i2p::util::GetMillisecondsSinceEpoch () > m_LeaseSetSubmissionTime + LEASET_CONFIRMATION_TIMEOUT)
                    m_LeaseSetUpdateStatus = eLeaseSetUpdated;

            // attach DeviveryStatus if necessary
            if (newTags || m_LeaseSetUpdateStatus == eLeaseSetUpdated) // new tags created or leaseset updated
            {
                // clove is DeliveryStatus 
                auto cloveSize = CreateDeliveryStatusClove (payload + size, msgID);
                if (cloveSize > 0) // successive?
                {
                    size += cloveSize;
                    (*numCloves)++;
                    if (newTags) // new tags created
                        m_UnconfirmedTagsMsgs[msgID] = newTags;
                    m_Owner->DeliveryStatusSent (shared_from_this (), msgID);
                }
                else
                    LogPrint ("DeliveryStatus clove was not created");
            }   
            // attach LeaseSet
            if (m_LeaseSetUpdateStatus == eLeaseSetUpdated) 
            {
                m_LeaseSetUpdateStatus = eLeaseSetSubmitted;
                m_LeaseSetUpdateMsgID = msgID;
                m_LeaseSetSubmissionTime = i2p::util::GetMillisecondsSinceEpoch ();
                // clove if our leaseSet must be attached
                auto leaseSet = CreateDatabaseStoreMsg (m_Owner->GetLeaseSet ());
                size += CreateGarlicClove (payload + size, leaseSet, false); 
                (*numCloves)++;
            }
        }   
        if (msg) // clove message ifself if presented
        {   
            size += CreateGarlicClove (payload + size, msg, m_Destination ? m_Destination->IsDestination () : false);
            (*numCloves)++;
        }   
        
        memset (payload + size, 0, 3); // certificate of message
        size += 3;
        htobe32buf (payload + size, msgID); // MessageID
        size += 4;
        htobe64buf (payload + size, ts); // Expiration of message
        size += 8;
        return size;
    }   

    size_t GarlicRoutingSession::CreateGarlicClove (uint8_t * buf, std::shared_ptr<const I2NPMessage> msg, bool isDestination)
    {
        uint64_t ts = i2p::util::GetMillisecondsSinceEpoch () + 5000; // 5 sec
        size_t size = 0;
        if (isDestination && m_Destination)
        {
            buf[size] = eGarlicDeliveryTypeDestination << 5;//  delivery instructions flag destination
            size++;
            memcpy (buf + size, m_Destination->GetIdentHash (), 32);
            size += 32;
        }   
        else    
        {   
            buf[size] = 0;//  delivery instructions flag local
            size++;
        }
        
        memcpy (buf + size, msg->GetBuffer (), msg->GetLength ());
        size += msg->GetLength ();
        htobe32buf (buf + size, m_Rnd.GenerateWord32 ()); // CloveID
        size += 4;
        htobe64buf (buf + size, ts); // Expiration of clove
        size += 8;
        memset (buf + size, 0, 3); // certificate of clove
        size += 3;
        return size;
    }   

    size_t GarlicRoutingSession::CreateDeliveryStatusClove (uint8_t * buf, uint32_t msgID)
    {       
        size_t size = 0;
        if (m_Owner)
        {
            auto inboundTunnel = m_Owner->GetTunnelPool ()->GetNextInboundTunnel ();
            if (inboundTunnel)
            {   
                buf[size] = eGarlicDeliveryTypeTunnel << 5; // delivery instructions flag tunnel
                size++;
                // hash and tunnelID sequence is reversed for Garlic 
                memcpy (buf + size, inboundTunnel->GetNextIdentHash (), 32); // To Hash
                size += 32;
                htobe32buf (buf + size, inboundTunnel->GetNextTunnelID ()); // tunnelID
                size += 4;  
                // create msg 
                auto msg = CreateDeliveryStatusMsg (msgID);
                if (m_Owner)
                {
                    //encrypt 
                    uint8_t key[32], tag[32];
                    m_Rnd.GenerateBlock (key, 32); // random session key 
                    m_Rnd.GenerateBlock (tag, 32); // random session tag
                    m_Owner->SubmitSessionKey (key, tag);
                    GarlicRoutingSession garlic (key, tag);
                    msg = garlic.WrapSingleMessage (msg);       
                }
                memcpy (buf + size, msg->GetBuffer (), msg->GetLength ());
                size += msg->GetLength ();
                // fill clove
                uint64_t ts = i2p::util::GetMillisecondsSinceEpoch () + 5000; // 5 sec
                htobe32buf (buf + size, m_Rnd.GenerateWord32 ()); // CloveID
                size += 4;
                htobe64buf (buf + size, ts); // Expiration of clove
                size += 8;
                memset (buf + size, 0, 3); // certificate of clove
                size += 3;
            }
            else    
                LogPrint (eLogError, "No inbound tunnels in the pool for DeliveryStatus");  
        }
        else
            LogPrint ("Missing local LeaseSet");

        return size;
    }
    
    GarlicDestination::~GarlicDestination ()
    {
    }

    void GarlicDestination::AddSessionKey (const uint8_t * key, const uint8_t * tag)
    {
        if (key)
        {
            uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
            auto decryption = std::make_shared<i2p::crypto::CBCDecryption>();
            decryption->SetKey (key);
            m_Tags[SessionTag(tag, ts)] = decryption;
        }
    }

    bool GarlicDestination::SubmitSessionKey (const uint8_t * key, const uint8_t * tag) 
    {
        AddSessionKey (key, tag);
        return true;
    }

    void GarlicDestination::HandleGarlicMessage (std::shared_ptr<I2NPMessage> msg)
    {
        uint8_t * buf = msg->GetPayload ();
        uint32_t length = bufbe32toh (buf);
        if (length > msg->GetLength ())
        {
            LogPrint (eLogError, "Garlic message length ", length, " exceeds I2NP message length ", msg->GetLength ());
            return;
        }   
        buf += 4; // length
        auto it = m_Tags.find (SessionTag(buf));
        if (it != m_Tags.end ())
        {
            // tag found. Use AES
            if (length >= 32)
            {   
                uint8_t iv[32]; // IV is first 16 bytes
                CryptoPP::SHA256().CalculateDigest(iv, buf, 32);
                it->second->SetIV (iv);
                it->second->Decrypt (buf + 32, length - 32, buf + 32);
                HandleAESBlock (buf + 32, length - 32, it->second, msg->from);
            }   
            else
                LogPrint (eLogError, "Garlic message length ", length, " is less than 32 bytes");
            m_Tags.erase (it); // tag might be used only once   
        }
        else
        {
            // tag not found. Use ElGamal
            ElGamalBlock elGamal;
            if (length >= 514 && i2p::crypto::ElGamalDecrypt (GetEncryptionPrivateKey (), buf, (uint8_t *)&elGamal, true))
            {   
                auto decryption = std::make_shared<i2p::crypto::CBCDecryption>();
                decryption->SetKey (elGamal.sessionKey);
                uint8_t iv[32]; // IV is first 16 bytes
                CryptoPP::SHA256().CalculateDigest(iv, elGamal.preIV, 32); 
                decryption->SetIV (iv);
                decryption->Decrypt(buf + 514, length - 514, buf + 514);
                HandleAESBlock (buf + 514, length - 514, decryption, msg->from);
            }   
            else
                LogPrint (eLogError, "Failed to decrypt garlic");
        }

        // cleanup expired tags
        uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
        if (ts > m_LastTagsCleanupTime + INCOMING_TAGS_EXPIRATION_TIMEOUT)
        {
            if (m_LastTagsCleanupTime)
            {
                int numExpiredTags = 0;
                for (auto it = m_Tags.begin (); it != m_Tags.end ();)
                {
                    if (ts > it->first.creationTime + INCOMING_TAGS_EXPIRATION_TIMEOUT)
                    {
                        numExpiredTags++;
                        it = m_Tags.erase (it);
                    }   
                    else
                        it++;
                }
                LogPrint (numExpiredTags, " tags expired for ", GetIdentHash().ToBase64 ());
            }   
            m_LastTagsCleanupTime = ts;
        }   
    }   

    void GarlicDestination::HandleAESBlock (uint8_t * buf, size_t len, std::shared_ptr<i2p::crypto::CBCDecryption> decryption,
        std::shared_ptr<i2p::tunnel::InboundTunnel> from)
    {
        uint16_t tagCount = bufbe16toh (buf);
        buf += 2; len -= 2; 
        if (tagCount > 0)
        {   
            if (tagCount*32 > len) 
            {
                LogPrint (eLogError, "Tag count ", tagCount, " exceeds length ", len);
                return ;
            }   
            uint32_t ts = i2p::util::GetSecondsSinceEpoch ();
            for (int i = 0; i < tagCount; i++)
                m_Tags[SessionTag(buf + i*32, ts)] = decryption;    
        }   
        buf += tagCount*32;
        len -= tagCount*32;
        uint32_t payloadSize = bufbe32toh (buf);
        if (payloadSize > len)
        {
            LogPrint (eLogError, "Unexpected payload size ", payloadSize);
            return;
        }   
        buf += 4;
        uint8_t * payloadHash = buf;
        buf += 32;// payload hash. 
        if (*buf) // session key?
            buf += 32; // new session key
        buf++; // flag

        // payload
        if (!CryptoPP::SHA256().VerifyDigest (payloadHash, buf, payloadSize)) // payload hash doesn't match
        {
            LogPrint ("Wrong payload hash");
            return;
        }           
        HandleGarlicPayload (buf, payloadSize, from);
    }   

    void GarlicDestination::HandleGarlicPayload (uint8_t * buf, size_t len, std::shared_ptr<i2p::tunnel::InboundTunnel> from)
    {
        const uint8_t * buf1 = buf;
        int numCloves = buf[0];
        LogPrint (numCloves," cloves");
        buf++;
        for (int i = 0; i < numCloves; i++)
        {
            // delivery instructions
            uint8_t flag = buf[0];
            buf++; // flag
            if (flag & 0x80) // encrypted?
            {
                // TODO: implement
                LogPrint ("Clove encrypted");
                buf += 32; 
            }   
            GarlicDeliveryType deliveryType = (GarlicDeliveryType)((flag >> 5) & 0x03);
            switch (deliveryType)
            {
                case eGarlicDeliveryTypeLocal:
                    LogPrint ("Garlic type local");
                    HandleI2NPMessage (buf, len, from);
                break;  
                case eGarlicDeliveryTypeDestination:    
                    LogPrint ("Garlic type destination");
                    buf += 32; // destination. check it later or for multiple destinations
                    HandleI2NPMessage (buf, len, from);
                break;
                case eGarlicDeliveryTypeTunnel:
                {   
                    LogPrint ("Garlic type tunnel");
                    // gwHash and gwTunnel sequence is reverted
                    uint8_t * gwHash = buf;
                    buf += 32;
                    uint32_t gwTunnel = bufbe32toh (buf);
                    buf += 4;
                    std::shared_ptr<i2p::tunnel::OutboundTunnel> tunnel;
                    if (from && from->GetTunnelPool ())
                        tunnel = from->GetTunnelPool ()->GetNextOutboundTunnel ();
                    if (tunnel) // we have send it through an outbound tunnel
                    {   
                        auto msg = CreateI2NPMessage (buf, GetI2NPMessageLength (buf), from);
                        tunnel->SendTunnelDataMsg (gwHash, gwTunnel, msg);
                    }   
                    else
                        LogPrint ("No outbound tunnels available for garlic clove");
                    break;
                }
                case eGarlicDeliveryTypeRouter:
                    LogPrint ("Garlic type router not supported");
                    buf += 32;
                break;  
                default:
                    LogPrint ("Unknow garlic delivery type ", (int)deliveryType);
            }
            buf += GetI2NPMessageLength (buf); //  I2NP
            buf += 4; // CloveID
            buf += 8; // Date
            buf += 3; // Certificate
            if (buf - buf1  > (int)len)
            {
                LogPrint (eLogError, "Garlic clove is too long");
                break;
            }   
        }   
    }   
    
    std::shared_ptr<I2NPMessage> GarlicDestination::WrapMessage (std::shared_ptr<const i2p::data::RoutingDestination> destination, 
        std::shared_ptr<I2NPMessage> msg, bool attachLeaseSet)  
    {
        auto session = GetRoutingSession (destination, attachLeaseSet);  // 32 tags by default
        return session->WrapSingleMessage (msg);    
    }

    std::shared_ptr<GarlicRoutingSession> GarlicDestination::GetRoutingSession (
        std::shared_ptr<const i2p::data::RoutingDestination> destination, bool attachLeaseSet)
    {
        auto it = m_Sessions.find (destination->GetIdentHash ());
        std::shared_ptr<GarlicRoutingSession> session;
        if (it != m_Sessions.end ())
            session = it->second;
        if (!session)
        {
            session = std::make_shared<GarlicRoutingSession> (this, destination, 
                attachLeaseSet ? 40 : 4, attachLeaseSet); // 40 tags for connections and 4 for LS requests
            std::unique_lock<std::mutex> l(m_SessionsMutex);
            m_Sessions[destination->GetIdentHash ()] = session;
        }   
        return session;
    }   
    
    void GarlicDestination::CleanupRoutingSessions ()
    {
        std::unique_lock<std::mutex> l(m_SessionsMutex);
        for (auto it = m_Sessions.begin (); it != m_Sessions.end ();)
        {
            if (!it->second->CleanupExpiredTags ())
            {
                LogPrint (eLogInfo, "Routing session to ", it->first.ToBase32 (), " deleted");
                it = m_Sessions.erase (it);
            }
            else
                it++;
        }
    }
    
    void GarlicDestination::RemoveCreatedSession (uint32_t msgID)
    {
        m_CreatedSessions.erase (msgID);
    }

    void GarlicDestination::DeliveryStatusSent (std::shared_ptr<GarlicRoutingSession> session, uint32_t msgID)
    {
        m_CreatedSessions[msgID] = session;
    }       

    void GarlicDestination::HandleDeliveryStatusMessage (std::shared_ptr<I2NPMessage> msg)
    {
        uint32_t msgID = bufbe32toh (msg->GetPayload ());
        {
            auto it = m_CreatedSessions.find (msgID);
            if (it != m_CreatedSessions.end ())         
            {
                it->second->MessageConfirmed (msgID);
                m_CreatedSessions.erase (it);
                LogPrint (eLogInfo, "Garlic message ", msgID, " acknowledged");
            }   
        }
    }

    void GarlicDestination::SetLeaseSetUpdated ()
    {
        std::unique_lock<std::mutex> l(m_SessionsMutex);    
        for (auto it: m_Sessions)
            it.second->SetLeaseSetUpdated ();
    }

    void GarlicDestination::ProcessGarlicMessage (std::shared_ptr<I2NPMessage> msg)
    {
        HandleGarlicMessage (msg);
    }

    void GarlicDestination::ProcessDeliveryStatusMessage (std::shared_ptr<I2NPMessage> msg)
    {
        HandleDeliveryStatusMessage (msg);
    }

}   
}