path: root/swarm/storage/feeds/request.go

// Copyright 2018 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 feeds

import (
    "bytes"
    "encoding/json"
    "hash"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/hexutil"
    "github.com/ethereum/go-ethereum/swarm/storage"
    "github.com/ethereum/go-ethereum/swarm/storage/feeds/lookup"
)

// Request represents a request to sign or signed Feed Update message
type Request struct {
    Update     // actual content that will be put on the chunk, less signature
    Signature  *Signature
    idAddr     storage.Address // cached chunk address for the update (not serialized, for internal use)
    binaryData []byte          // cached serialized data (does not get serialized again!, for efficiency/internal use)
}

// updateRequestJSON represents a JSON-serialized UpdateRequest
type updateRequestJSON struct {
    ID
    ProtocolVersion uint8  `json:"protocolVersion"`
    Data            string `json:"data,omitempty"`
    Signature       string `json:"signature,omitempty"`
}

// Request layout
// Update bytes
// SignatureLength bytes
const minimumSignedUpdateLength = minimumUpdateDataLength + signatureLength

// NewFirstRequest returns a ready to sign request to publish a first feed update
func NewFirstRequest(topic Topic) *Request {

    request := new(Request)

    // get the current time
    now := TimestampProvider.Now().Time
    request.Epoch = lookup.GetFirstEpoch(now)
    request.Feed.Topic = topic
    request.Header.Version = ProtocolVersion

    return request
}

// SetData stores the payload data the feed update will be updated with
func (r *Request) SetData(data []byte) {
    r.data = data
    r.Signature = nil
}

// IsUpdate returns true if this request models a signed update or otherwise it is a signature request
func (r *Request) IsUpdate() bool {
    return r.Signature != nil
}

// Verify checks that signatures are valid
func (r *Request) Verify() (err error) {
    if len(r.data) == 0 {
        return NewError(ErrInvalidValue, "Update does not contain data")
    }
    if r.Signature == nil {
        return NewError(ErrInvalidSignature, "Missing signature field")
    }

    digest, err := r.GetDigest()
    if err != nil {
        return err
    }

    // get the address of the signer (which also checks that it's a valid signature)
    r.Feed.User, err = getUserAddr(digest, *r.Signature)
    if err != nil {
        return err
    }

    // check that the lookup information contained in the chunk matches the updateAddr (chunk search key)
    // that was used to retrieve this chunk
    // if this validation fails, someone forged a chunk.
    if !bytes.Equal(r.idAddr, r.Addr()) {
        return NewError(ErrInvalidSignature, "Signature address does not match with update user address")
    }

    return nil
}

// Sign executes the signature to validate the update message
func (r *Request) Sign(signer Signer) error {
    r.Feed.User = signer.Address()
    r.binaryData = nil           //invalidate serialized data
    digest, err := r.GetDigest() // computes digest and serializes into .binaryData
    if err != nil {
        return err
    }

    signature, err := signer.Sign(digest)
    if err != nil {
        return err
    }

    // Although the Signer interface returns the public address of the signer,
    // recover it from the signature to see if they match
    userAddr, err := getUserAddr(digest, signature)
    if err != nil {
        return NewError(ErrInvalidSignature, "Error verifying signature")
    }

    if userAddr != signer.Address() { // sanity check to make sure the Signer is declaring the same address used to sign!
        return NewError(ErrInvalidSignature, "Signer address does not match update user address")
    }

    r.Signature = &signature
    r.idAddr = r.Addr()
    return nil
}

// GetDigest creates the feed update digest used in signatures
// the serialized payload is cached in .binaryData
func (r *Request) GetDigest() (result common.Hash, err error) {
    hasher := hashPool.Get().(hash.Hash)
    defer hashPool.Put(hasher)
    hasher.Reset()
    dataLength := r.Update.binaryLength()
    if r.binaryData == nil {
        r.binaryData = make([]byte, dataLength+signatureLength)
        if err := r.Update.binaryPut(r.binaryData[:dataLength]); err != nil {
            return result, err
        }
    }
    hasher.Write(r.binaryData[:dataLength]) //everything except the signature.

    return common.BytesToHash(hasher.Sum(nil)), nil
}

// create an update chunk.
func (r *Request) toChunk() (storage.Chunk, error) {

    // Check that the update is signed and serialized
    // For efficiency, data is serialized during signature and cached in
    // the binaryData field when computing the signature digest in .getDigest()
    if r.Signature == nil || r.binaryData == nil {
        return nil, NewError(ErrInvalidSignature, "toChunk called without a valid signature or payload data. Call .Sign() first.")
    }

    updateLength := r.Update.binaryLength()

    // signature is the last item in the chunk data
    copy(r.binaryData[updateLength:], r.Signature[:])

    chunk := storage.NewChunk(r.idAddr, r.binaryData)
    return chunk, nil
}

// fromChunk populates this structure from chunk data. It does not verify the signature is valid.
func (r *Request) fromChunk(updateAddr storage.Address, chunkdata []byte) error {
    // for update chunk layout see Request definition

    //deserialize the feed update portion
    if err := r.Update.binaryGet(chunkdata[:len(chunkdata)-signatureLength]); err != nil {
        return err
    }

    // Extract the signature
    var signature *Signature
    cursor := r.Update.binaryLength()
    sigdata := chunkdata[cursor : cursor+signatureLength]
    if len(sigdata) > 0 {
        signature = &Signature{}
        copy(signature[:], sigdata)
    }

    r.Signature = signature
    r.idAddr = updateAddr
    r.binaryData = chunkdata

    return nil

}

// FromValues deserializes this instance from a string key-value store
// useful to parse query strings
func (r *Request) FromValues(values Values, data []byte) error {
    signatureBytes, err := hexutil.Decode(values.Get("signature"))
    if err != nil {
        r.Signature = nil
    } else {
        if len(signatureBytes) != signatureLength {
            return NewError(ErrInvalidSignature, "Incorrect signature length")
        }
        r.Signature = new(Signature)
        copy(r.Signature[:], signatureBytes)
    }
    err = r.Update.FromValues(values, data)
    if err != nil {
        return err
    }
    r.idAddr = r.Addr()
    return err
}

// AppendValues serializes this structure into the provided string key-value store
// useful to build query strings
func (r *Request) AppendValues(values Values) []byte {
    if r.Signature != nil {
        values.Set("signature", hexutil.Encode(r.Signature[:]))
    }
    return r.Update.AppendValues(values)
}

// fromJSON takes an update request JSON and populates an UpdateRequest
func (r *Request) fromJSON(j *updateRequestJSON) error {

    r.ID = j.ID
    r.Header.Version = j.ProtocolVersion

    var err error
    if j.Data != "" {
        r.data, err = hexutil.Decode(j.Data)
        if err != nil {
            return NewError(ErrInvalidValue, "Cannot decode data")
        }
    }

    if j.Signature != "" {
        sigBytes, err := hexutil.Decode(j.Signature)
        if err != nil || len(sigBytes) != signatureLength {
            return NewError(ErrInvalidSignature, "Cannot decode signature")
        }
        r.Signature = new(Signature)
        r.idAddr = r.Addr()
        copy(r.Signature[:], sigBytes)
    }
    return nil
}

// UnmarshalJSON takes a JSON structure stored in a byte array and populates the Request object
// Implements json.Unmarshaler interface
func (r *Request) UnmarshalJSON(rawData []byte) error {
    var requestJSON updateRequestJSON
    if err := json.Unmarshal(rawData, &requestJSON); err != nil {
        return err
    }
    return r.fromJSON(&requestJSON)
}

// MarshalJSON takes an update request and encodes it as a JSON structure into a byte array
// Implements json.Marshaler interface
func (r *Request) MarshalJSON() (rawData []byte, err error) {
    var signatureString, dataString string
    if r.Signature != nil {
        signatureString = hexutil.Encode(r.Signature[:])
    }
    if r.data != nil {
        dataString = hexutil.Encode(r.data)
    }

    requestJSON := &updateRequestJSON{
        ID:              r.ID,
        ProtocolVersion: r.Header.Version,
        Data:            dataString,
        Signature:       signatureString,
    }

    return json.Marshal(requestJSON)
}