path: root/swarm/pss/keystore.go

// Copyright 2019 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package pss

import (
    "crypto/ecdsa"
    "errors"
    "fmt"
    "sync"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/metrics"
    "github.com/ethereum/go-ethereum/swarm/log"
    whisper "github.com/ethereum/go-ethereum/whisper/whisperv6"
)

type KeyStore struct {
    w *whisper.Whisper // key and encryption backend

    mx                       sync.RWMutex
    pubKeyPool               map[string]map[Topic]*pssPeer // mapping of hex public keys to peer address by topic.
    symKeyPool               map[string]map[Topic]*pssPeer // mapping of symkeyids to peer address by topic.
    symKeyDecryptCache       []*string                     // fast lookup of symkeys recently used for decryption; last used is on top of stack
    symKeyDecryptCacheCursor int                           // modular cursor pointing to last used, wraps on symKeyDecryptCache array
}

func loadKeyStore() *KeyStore {
    return &KeyStore{
        w: whisper.New(&whisper.DefaultConfig),

        pubKeyPool:         make(map[string]map[Topic]*pssPeer),
        symKeyPool:         make(map[string]map[Topic]*pssPeer),
        symKeyDecryptCache: make([]*string, defaultSymKeyCacheCapacity),
    }
}

func (ks *KeyStore) isSymKeyStored(key string) bool {
    ks.mx.RLock()
    defer ks.mx.RUnlock()
    var ok bool
    _, ok = ks.symKeyPool[key]
    return ok
}

func (ks *KeyStore) isPubKeyStored(key string) bool {
    ks.mx.RLock()
    defer ks.mx.RUnlock()
    var ok bool
    _, ok = ks.pubKeyPool[key]
    return ok
}

func (ks *KeyStore) getPeerSym(symkeyid string, topic Topic) (*pssPeer, bool) {
    ks.mx.RLock()
    defer ks.mx.RUnlock()
    psp, ok := ks.symKeyPool[symkeyid][topic]
    return psp, ok
}

func (ks *KeyStore) getPeerPub(pubkeyid string, topic Topic) (*pssPeer, bool) {
    ks.mx.RLock()
    defer ks.mx.RUnlock()
    psp, ok := ks.pubKeyPool[pubkeyid][topic]
    return psp, ok
}

// Links a peer ECDSA public key to a topic.
// This is required for asymmetric message exchange on the given topic.
// The value in `address` will be used as a routing hint for the public key / topic association.
func (ks *KeyStore) SetPeerPublicKey(pubkey *ecdsa.PublicKey, topic Topic, address PssAddress) error {
    if err := validateAddress(address); err != nil {
        return err
    }
    pubkeybytes := crypto.FromECDSAPub(pubkey)
    if len(pubkeybytes) == 0 {
        return fmt.Errorf("invalid public key: %v", pubkey)
    }
    pubkeyid := common.ToHex(pubkeybytes)
    psp := &pssPeer{
        address: address,
    }
    ks.mx.Lock()
    if _, ok := ks.pubKeyPool[pubkeyid]; !ok {
        ks.pubKeyPool[pubkeyid] = make(map[Topic]*pssPeer)
    }
    ks.pubKeyPool[pubkeyid][topic] = psp
    ks.mx.Unlock()
    log.Trace("added pubkey", "pubkeyid", pubkeyid, "topic", topic, "address", address)
    return nil
}

// adds a symmetric key to the pss key pool, and optionally adds the key to the
// collection of keys used to attempt symmetric decryption of incoming messages
func (ks *KeyStore) addSymmetricKeyToPool(keyid string, topic Topic, address PssAddress, addtocache bool, protected bool) {
    psp := &pssPeer{
        address:   address,
        protected: protected,
    }
    ks.mx.Lock()
    if _, ok := ks.symKeyPool[keyid]; !ok {
        ks.symKeyPool[keyid] = make(map[Topic]*pssPeer)
    }
    ks.symKeyPool[keyid][topic] = psp
    ks.mx.Unlock()
    if addtocache {
        ks.symKeyDecryptCacheCursor++
        ks.symKeyDecryptCache[ks.symKeyDecryptCacheCursor%cap(ks.symKeyDecryptCache)] = &keyid
    }
}

// Returns all recorded topic and address combination for a specific public key
func (ks *KeyStore) GetPublickeyPeers(keyid string) (topic []Topic, address []PssAddress, err error) {
    ks.mx.RLock()
    defer ks.mx.RUnlock()
    for t, peer := range ks.pubKeyPool[keyid] {
        topic = append(topic, t)
        address = append(address, peer.address)
    }
    return topic, address, nil
}

func (ks *KeyStore) getPeerAddress(keyid string, topic Topic) (PssAddress, error) {
    ks.mx.RLock()
    defer ks.mx.RUnlock()
    if peers, ok := ks.pubKeyPool[keyid]; ok {
        if t, ok := peers[topic]; ok {
            return t.address, nil
        }
    }
    return nil, fmt.Errorf("peer with pubkey %s, topic %x not found", keyid, topic)
}

// Attempt to decrypt, validate and unpack a symmetrically encrypted message.
// If successful, returns the unpacked whisper ReceivedMessage struct
// encapsulating the decrypted message, and the whisper backend id
// of the symmetric key used to decrypt the message.
// It fails if decryption of the message fails or if the message is corrupted.
func (ks *KeyStore) processSym(envelope *whisper.Envelope) (*whisper.ReceivedMessage, string, PssAddress, error) {
    metrics.GetOrRegisterCounter("pss.process.sym", nil).Inc(1)

    for i := ks.symKeyDecryptCacheCursor; i > ks.symKeyDecryptCacheCursor-cap(ks.symKeyDecryptCache) && i > 0; i-- {
        symkeyid := ks.symKeyDecryptCache[i%cap(ks.symKeyDecryptCache)]
        symkey, err := ks.w.GetSymKey(*symkeyid)
        if err != nil {
            continue
        }
        recvmsg, err := envelope.OpenSymmetric(symkey)
        if err != nil {
            continue
        }
        if !recvmsg.ValidateAndParse() {
            return nil, "", nil, errors.New("symmetrically encrypted message has invalid signature or is corrupt")
        }
        var from PssAddress
        ks.mx.RLock()
        if ks.symKeyPool[*symkeyid][Topic(envelope.Topic)] != nil {
            from = ks.symKeyPool[*symkeyid][Topic(envelope.Topic)].address
        }
        ks.mx.RUnlock()
        ks.symKeyDecryptCacheCursor++
        ks.symKeyDecryptCache[ks.symKeyDecryptCacheCursor%cap(ks.symKeyDecryptCache)] = symkeyid
        return recvmsg, *symkeyid, from, nil
    }
    return nil, "", nil, errors.New("could not decrypt message")
}

// Attempt to decrypt, validate and unpack an asymmetrically encrypted message.
// If successful, returns the unpacked whisper ReceivedMessage struct
// encapsulating the decrypted message, and the byte representation of
// the public key used to decrypt the message.
// It fails if decryption of message fails, or if the message is corrupted.
func (ks *Pss) processAsym(envelope *whisper.Envelope) (*whisper.ReceivedMessage, string, PssAddress, error) {
    metrics.GetOrRegisterCounter("pss.process.asym", nil).Inc(1)

    recvmsg, err := envelope.OpenAsymmetric(ks.privateKey)
    if err != nil {
        return nil, "", nil, fmt.Errorf("could not decrypt message: %s", err)
    }
    // check signature (if signed), strip padding
    if !recvmsg.ValidateAndParse() {
        return nil, "", nil, errors.New("invalid message")
    }
    pubkeyid := common.ToHex(crypto.FromECDSAPub(recvmsg.Src))
    var from PssAddress
    ks.mx.RLock()
    if ks.pubKeyPool[pubkeyid][Topic(envelope.Topic)] != nil {
        from = ks.pubKeyPool[pubkeyid][Topic(envelope.Topic)].address
    }
    ks.mx.RUnlock()
    return recvmsg, pubkeyid, from, nil
}

// Symkey garbage collection
// a key is removed if:
// - it is not marked as protected
// - it is not in the incoming decryption cache
func (ks *Pss) cleanKeys() (count int) {
    for keyid, peertopics := range ks.symKeyPool {
        var expiredtopics []Topic
        for topic, psp := range peertopics {
            if psp.protected {
                continue
            }

            var match bool
            for i := ks.symKeyDecryptCacheCursor; i > ks.symKeyDecryptCacheCursor-cap(ks.symKeyDecryptCache) && i > 0; i-- {
                cacheid := ks.symKeyDecryptCache[i%cap(ks.symKeyDecryptCache)]
                if *cacheid == keyid {
                    match = true
                }
            }
            if !match {
                expiredtopics = append(expiredtopics, topic)
            }
        }
        for _, topic := range expiredtopics {
            ks.mx.Lock()
            delete(ks.symKeyPool[keyid], topic)
            log.Trace("symkey cleanup deletion", "symkeyid", keyid, "topic", topic, "val", ks.symKeyPool[keyid])
            ks.mx.Unlock()
            count++
        }
    }
    return count
}

// Automatically generate a new symkey for a topic and address hint
func (ks *KeyStore) GenerateSymmetricKey(topic Topic, address PssAddress, addToCache bool) (string, error) {
    keyid, err := ks.w.GenerateSymKey()
    if err == nil {
        ks.addSymmetricKeyToPool(keyid, topic, address, addToCache, false)
    }
    return keyid, err
}

// Returns a symmetric key byte sequence stored in the whisper backend by its unique id.
// Passes on the error value from the whisper backend.
func (ks *KeyStore) GetSymmetricKey(symkeyid string) ([]byte, error) {
    return ks.w.GetSymKey(symkeyid)
}

// Links a peer symmetric key (arbitrary byte sequence) to a topic.
//
// This is required for symmetrically encrypted message exchange on the given topic.
//
// The key is stored in the whisper backend.
//
// If addtocache is set to true, the key will be added to the cache of keys
// used to attempt symmetric decryption of incoming messages.
//
// Returns a string id that can be used to retrieve the key bytes
// from the whisper backend (see pss.GetSymmetricKey())
func (ks *KeyStore) SetSymmetricKey(key []byte, topic Topic, address PssAddress, addtocache bool) (string, error) {
    if err := validateAddress(address); err != nil {
        return "", err
    }
    return ks.setSymmetricKey(key, topic, address, addtocache, true)
}

func (ks *KeyStore) setSymmetricKey(key []byte, topic Topic, address PssAddress, addtocache bool, protected bool) (string, error) {
    keyid, err := ks.w.AddSymKeyDirect(key)
    if err == nil {
        ks.addSymmetricKeyToPool(keyid, topic, address, addtocache, protected)
    }
    return keyid, err
}