// 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 whisperv5
import (
"crypto/aes"
"crypto/cipher"
"crypto/ecdsa"
crand "crypto/rand"
"crypto/sha256"
"errors"
"fmt"
mrand "math/rand"
"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"
"golang.org/x/crypto/pbkdf2"
)
// Options 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.
type ReceivedMessage struct {
Raw []byte
Payload []byte
Padding []byte
Signature []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, associated with the Topic
EnvelopeHash common.Hash // Message envelope hash to act as a unique id
EnvelopeVersion uint64
}
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
}
func DeriveOneTimeKey(key []byte, salt []byte, version uint64) ([]byte, error) {
if version == 0 {
derivedKey := pbkdf2.Key(key, salt, 8, aesKeyLength, sha256.New)
return derivedKey, nil
} else {
return nil, unknownVersionError(version)
}
}
// NewMessage creates and initializes a non-signed, non-encrypted Whisper message.
func NewSentMessage(params *MessageParams) *SentMessage {
msg := SentMessage{}
msg.Raw = make([]byte, 1, len(params.Payload)+len(params.Payload)+signatureLength+padSizeLimitUpper)
msg.Raw[0] = 0 // set all the flags to zero
msg.appendPadding(params)
msg.Raw = append(msg.Raw, params.Payload...)
return &msg
}
// appendPadding appends the pseudorandom padding bytes and sets the padding flag.
// The last byte contains the size of padding (thus, its size must not exceed 256).
func (msg *SentMessage) appendPadding(params *MessageParams) {
total := len(params.Payload) + 1
if params.Src != nil {
total += signatureLength
}
padChunk := padSizeLimitUpper
if total <= padSizeLimitLower {
padChunk = padSizeLimitLower
}
odd := total % padChunk
if odd > 0 {
padSize := padChunk - odd
if padSize > 255 {
// this algorithm is only valid if padSizeLimitUpper <= 256.
// if padSizeLimitUpper will ever change, please fix the algorithm
// (for more information see ReceivedMessage.extractPadding() function).
panic("please fix the padding algorithm before releasing new version")
}
buf := make([]byte, padSize)
mrand.Read(buf[1:])
buf[0] = byte(padSize)
if params.Padding != nil {
copy(buf[1:], params.Padding)
}
msg.Raw = append(msg.Raw, buf...)
msg.Raw[0] |= byte(0x1) // number of bytes indicating the padding size
}
}
// 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(fmt.Sprintf("Trying to sign a message which was already signed"))
return nil
}
msg.Raw[0] |= signatureFlag
hash := crypto.Keccak256(msg.Raw)
signature, err := crypto.Sign(hash, key)
if err != nil {
msg.Raw[0] &= ^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 fmt.Errorf("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) (salt []byte, nonce []byte, err error) {
if !validateSymmetricKey(key) {
return nil, nil, errors.New("invalid key provided for symmetric encryption")
}
salt = make([]byte, saltLength)
_, err = crand.Read(salt)
if err != nil {
return nil, nil, err
} else if !validateSymmetricKey(salt) {
return nil, nil, errors.New("crypto/rand failed to generate salt")
}
derivedKey, err := DeriveOneTimeKey(key, salt, EnvelopeVersion)
if err != nil {
return nil, nil, err
}
if !validateSymmetricKey(derivedKey) {
return nil, nil, errors.New("failed to derive one-time key")
}
block, err := aes.NewCipher(derivedKey)
if err != nil {
return nil, nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, nil, err
}
// never use more than 2^32 random nonces with a given key
nonce = make([]byte, aesgcm.NonceSize())
_, err = crand.Read(nonce)
if err != nil {
return nil, nil, err
} else if !validateSymmetricKey(nonce) {
return nil, nil, errors.New("crypto/rand failed to generate nonce")
}
msg.Raw = aesgcm.Seal(nil, nonce, msg.Raw, nil)
return salt, nonce, nil
}
// Wrap bundles the message into an Envelope to transmit over the network.
//
// pow (Proof Of Work) controls how much time to spend on hashing the message,
// inherently controlling its priority through the network (smaller hash, bigger
// priority).
//
// The user can control the amount of identity, privacy and encryption through
// the options parameter as follows:
// - options.From == nil && options.To == nil: anonymous broadcast
// - options.From != nil && options.To == nil: signed broadcast (known sender)
// - options.From == nil && options.To != nil: encrypted anonymous message
// - options.From != nil && options.To != nil: encrypted signed message
func (msg *SentMessage) Wrap(options *MessageParams) (envelope *Envelope, err error) {
if options.TTL == 0 {
options.TTL = DefaultTTL
}
if options.Src != nil {
err = msg.sign(options.Src)
if err != nil {
return nil, err
}
}
if len(msg.Raw) > MaxMessageLength {
log.Error(fmt.Sprintf("Message size must not exceed %d bytes", MaxMessageLength))
return nil, errors.New("Oversized message")
}
var salt, nonce []byte
if options.Dst != nil {
err = msg.encryptAsymmetric(options.Dst)
} else if options.KeySym != nil {
salt, nonce, err = msg.encryptSymmetric(options.KeySym)
} else {
err = errors.New("Unable to encrypt the message: neither Dst nor Key")
}
if err != nil {
return nil, err
}
envelope = NewEnvelope(options.TTL, options.Topic, salt, nonce, msg)
err = envelope.Seal(options)
if 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, salt []byte, nonce []byte) error {
derivedKey, err := DeriveOneTimeKey(key, salt, msg.EnvelopeVersion)
if err != nil {
return err
}
block, err := aes.NewCipher(derivedKey)
if err != nil {
return err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return err
}
if len(nonce) != aesgcm.NonceSize() {
info := fmt.Sprintf("Wrong AES nonce size - want: %d, got: %d", len(nonce), aesgcm.NonceSize())
log.Error(fmt.Sprintf(info))
return errors.New(info)
}
decrypted, err := aesgcm.Open(nil, nonce, msg.Raw, nil)
if err != nil {
return err
}
msg.Raw = decrypted
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
}
// Validate checks the validity and extracts the fields in case of success
func (msg *ReceivedMessage) Validate() 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:]
msg.Src = msg.SigToPubKey()
if msg.Src == nil {
return false
}
}
padSize, ok := msg.extractPadding(end)
if !ok {
return false
}
msg.Payload = msg.Raw[1+padSize : end]
return true
}
// extractPadding extracts the padding from raw message.
// although we don't support sending messages with padding size
// exceeding 255 bytes, such messages are perfectly valid, and
// can be successfully decrypted.
func (msg *ReceivedMessage) extractPadding(end int) (int, bool) {
paddingSize := 0
sz := int(msg.Raw[0] & paddingMask) // number of bytes containing the entire size of padding, could be zero
if sz != 0 {
paddingSize = int(bytesToIntLittleEndian(msg.Raw[1 : 1+sz]))
if paddingSize < sz || paddingSize+1 > end {
return 0, false
}
msg.Padding = msg.Raw[1+sz : 1+paddingSize]
}
return paddingSize, true
}
// Recover retrieves the public key of the message signer.
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(fmt.Sprintf("Could not get public key from signature: %v", err))
return nil
}
return pub
}
// hash calculates the SHA3 checksum of the message flags, 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)
}
