// Copyright 2016 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/>.
// Contains the Whisper protocol Message element.
package whisperv6
import (
"crypto/aes"
"crypto/cipher"
"crypto/ecdsa"
crand "crypto/rand"
"encoding/binary"
"errors"
mrand "math/rand"
"strconv"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/crypto/ecies"
"github.com/ethereum/go-ethereum/log"
)
// MessageParams specifies the exact way a message should be wrapped
// into an Envelope.
type MessageParams struct {
TTL uint32
Src *ecdsa.PrivateKey
Dst *ecdsa.PublicKey
KeySym []byte
Topic TopicType
WorkTime uint32
PoW float64
Payload []byte
Padding []byte
}
// SentMessage represents an end-user data packet to transmit through the
// Whisper protocol. These are wrapped into Envelopes that need not be
// understood by intermediate nodes, just forwarded.
type sentMessage struct {
Raw []byte
}
// ReceivedMessage represents a data packet to be received through the
// Whisper protocol and successfully decrypted.
type ReceivedMessage struct {
Raw []byte
Payload []byte
Padding []byte
Signature []byte
Salt []byte
PoW float64 // Proof of work as described in the Whisper spec
Sent uint32 // Time when the message was posted into the network
TTL uint32 // Maximum time to live allowed for the message
Src *ecdsa.PublicKey // Message recipient (identity used to decode the message)
Dst *ecdsa.PublicKey // Message recipient (identity used to decode the message)
Topic TopicType
SymKeyHash common.Hash // The Keccak256Hash of the key
EnvelopeHash common.Hash // Message envelope hash to act as a unique id
}
func isMessageSigned(flags byte) bool {
return (flags & signatureFlag) != 0
}
func (msg *ReceivedMessage) isSymmetricEncryption() bool {
return msg.SymKeyHash != common.Hash{}
}
func (msg *ReceivedMessage) isAsymmetricEncryption() bool {
return msg.Dst != nil
}
// NewSentMessage creates and initializes a non-signed, non-encrypted Whisper message.
func NewSentMessage(params *MessageParams) (*sentMessage, error) {
const payloadSizeFieldMaxSize = 4
msg := sentMessage{}
msg.Raw = make([]byte, 1,
flagsLength+payloadSizeFieldMaxSize+len(params.Payload)+len(params.Padding)+signatureLength+padSizeLimit)
msg.Raw[0] = 0 // set all the flags to zero
msg.addPayloadSizeField(params.Payload)
msg.Raw = append(msg.Raw, params.Payload...)
err := msg.appendPadding(params)
return &msg, err
}
// addPayloadSizeField appends the auxiliary field containing the size of payload
func (msg *sentMessage) addPayloadSizeField(payload []byte) {
fieldSize := getSizeOfPayloadSizeField(payload)
field := make([]byte, 4)
binary.LittleEndian.PutUint32(field, uint32(len(payload)))
field = field[:fieldSize]
msg.Raw = append(msg.Raw, field...)
msg.Raw[0] |= byte(fieldSize)
}
// getSizeOfPayloadSizeField returns the number of bytes necessary to encode the size of payload
func getSizeOfPayloadSizeField(payload []byte) int {
s := 1
for i := len(payload); i >= 256; i /= 256 {
s++
}
return s
}
// appendPadding appends the padding specified in params.
// If no padding is provided in params, then random padding is generated.
func (msg *sentMessage) appendPadding(params *MessageParams) error {
if len(params.Padding) != 0 {
// padding data was provided by the Dapp, just use it as is
msg.Raw = append(msg.Raw, params.Padding...)
return nil
}
rawSize := flagsLength + getSizeOfPayloadSizeField(params.Payload) + len(params.Payload)
if params.Src != nil {
rawSize += signatureLength
}
odd := rawSize % padSizeLimit
paddingSize := padSizeLimit - odd
pad := make([]byte, paddingSize)
_, err := crand.Read(pad)
if err != nil {
return err
}
if !validateDataIntegrity(pad, paddingSize) {
return errors.New("failed to generate random padding of size " + strconv.Itoa(paddingSize))
}
msg.Raw = append(msg.Raw, pad...)
return nil
}
// sign calculates and sets the cryptographic signature for the message,
// also setting the sign flag.
func (msg *sentMessage) sign(key *ecdsa.PrivateKey) error {
if isMessageSigned(msg.Raw[0]) {
// this should not happen, but no reason to panic
log.Error("failed to sign the message: already signed")
return nil
}
msg.Raw[0] |= signatureFlag // it is important to set this flag before signing
hash := crypto.Keccak256(msg.Raw)
signature, err := crypto.Sign(hash, key)
if err != nil {
msg.Raw[0] &= (0xFF ^ signatureFlag) // clear the flag
return err
}
msg.Raw = append(msg.Raw, signature...)
return nil
}
// encryptAsymmetric encrypts a message with a public key.
func (msg *sentMessage) encryptAsymmetric(key *ecdsa.PublicKey) error {
if !ValidatePublicKey(key) {
return errors.New("invalid public key provided for asymmetric encryption")
}
encrypted, err := ecies.Encrypt(crand.Reader, ecies.ImportECDSAPublic(key), msg.Raw, nil, nil)
if err == nil {
msg.Raw = encrypted
}
return err
}
// encryptSymmetric encrypts a message with a topic key, using AES-GCM-256.
// nonce size should be 12 bytes (see cipher.gcmStandardNonceSize).
func (msg *sentMessage) encryptSymmetric(key []byte) (err error) {
if !validateDataIntegrity(key, aesKeyLength) {
return errors.New("invalid key provided for symmetric encryption, size: " + strconv.Itoa(len(key)))
}
block, err := aes.NewCipher(key)
if err != nil {
return err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return err
}
salt, err := generateSecureRandomData(aesNonceLength) // never use more than 2^32 random nonces with a given key
if err != nil {
return err
}
encrypted := aesgcm.Seal(nil, salt, msg.Raw, nil)
msg.Raw = append(encrypted, salt...)
return nil
}
// generateSecureRandomData generates random data where extra security is required.
// The purpose of this function is to prevent some bugs in software or in hardware
// from delivering not-very-random data. This is especially useful for AES nonce,
// where true randomness does not really matter, but it is very important to have
// a unique nonce for every message.
func generateSecureRandomData(length int) ([]byte, error) {
x := make([]byte, length)
y := make([]byte, length)
res := make([]byte, length)
_, err := crand.Read(x)
if err != nil {
return nil, err
} else if !validateDataIntegrity(x, length) {
return nil, errors.New("crypto/rand failed to generate secure random data")
}
_, err = mrand.Read(y)
if err != nil {
return nil, err
} else if !validateDataIntegrity(y, length) {
return nil, errors.New("math/rand failed to generate secure random data")
}
for i := 0; i < length; i++ {
res[i] = x[i] ^ y[i]
}
if !validateDataIntegrity(res, length) {
return nil, errors.New("failed to generate secure random data")
}
return res, nil
}
// Wrap bundles the message into an Envelope to transmit over the network.
func (msg *sentMessage) Wrap(options *MessageParams) (envelope *Envelope, err error) {
if options.TTL == 0 {
options.TTL = DefaultTTL
}
if options.Src != nil {
if err = msg.sign(options.Src); err != nil {
return nil, err
}
}
if options.Dst != nil {
err = msg.encryptAsymmetric(options.Dst)
} else if options.KeySym != nil {
err = msg.encryptSymmetric(options.KeySym)
} else {
err = errors.New("unable to encrypt the message: neither symmetric nor assymmetric key provided")
}
if err != nil {
return nil, err
}
envelope = NewEnvelope(options.TTL, options.Topic, msg)
if err = envelope.Seal(options); err != nil {
return nil, err
}
return envelope, nil
}
// decryptSymmetric decrypts a message with a topic key, using AES-GCM-256.
// nonce size should be 12 bytes (see cipher.gcmStandardNonceSize).
func (msg *ReceivedMessage) decryptSymmetric(key []byte) error {
// symmetric messages are expected to contain the 12-byte nonce at the end of the payload
if len(msg.Raw) < aesNonceLength {
return errors.New("missing salt or invalid payload in symmetric message")
}
salt := msg.Raw[len(msg.Raw)-aesNonceLength:]
block, err := aes.NewCipher(key)
if err != nil {
return err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return err
}
decrypted, err := aesgcm.Open(nil, salt, msg.Raw[:len(msg.Raw)-aesNonceLength], nil)
if err != nil {
return err
}
msg.Raw = decrypted
msg.Salt = salt
return nil
}
// decryptAsymmetric decrypts an encrypted payload with a private key.
func (msg *ReceivedMessage) decryptAsymmetric(key *ecdsa.PrivateKey) error {
decrypted, err := ecies.ImportECDSA(key).Decrypt(crand.Reader, msg.Raw, nil, nil)
if err == nil {
msg.Raw = decrypted
}
return err
}
// ValidateAndParse checks the message validity and extracts the fields in case of success.
func (msg *ReceivedMessage) ValidateAndParse() bool {
end := len(msg.Raw)
if end < 1 {
return false
}
if isMessageSigned(msg.Raw[0]) {
end -= signatureLength
if end <= 1 {
return false
}
msg.Signature = msg.Raw[end : end+signatureLength]
msg.Src = msg.SigToPubKey()
if msg.Src == nil {
return false
}
}
beg := 1
payloadSize := 0
sizeOfPayloadSizeField := int(msg.Raw[0] & SizeMask) // number of bytes indicating the size of payload
if sizeOfPayloadSizeField != 0 {
payloadSize = int(bytesToUintLittleEndian(msg.Raw[beg : beg+sizeOfPayloadSizeField]))
if payloadSize+1 > end {
return false
}
beg += sizeOfPayloadSizeField
msg.Payload = msg.Raw[beg : beg+payloadSize]
}
beg += payloadSize
msg.Padding = msg.Raw[beg:end]
return true
}
// SigToPubKey returns the public key associated to the message's
// signature.
func (msg *ReceivedMessage) SigToPubKey() *ecdsa.PublicKey {
defer func() { recover() }() // in case of invalid signature
pub, err := crypto.SigToPub(msg.hash(), msg.Signature)
if err != nil {
log.Error("failed to recover public key from signature", "err", err)
return nil
}
return pub
}
// hash calculates the SHA3 checksum of the message flags, payload size field, payload and padding.
func (msg *ReceivedMessage) hash() []byte {
if isMessageSigned(msg.Raw[0]) {
sz := len(msg.Raw) - signatureLength
return crypto.Keccak256(msg.Raw[:sz])
}
return crypto.Keccak256(msg.Raw)
}
