wakuv1 envelope format

waku/v2/node/waku_payload.go

@@ -5,11 +5,14 @@ import (
 	"crypto/cipher"
 	"crypto/ecdsa"
 	crand "crypto/rand"
+	"encoding/binary"
+	"fmt"
 	mrand "math/rand"
 
 	"errors"
 	"strconv"
 
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/ecies"
 	"github.com/status-im/go-waku/waku/v2/protocol"
 )
@@ -22,16 +25,122 @@ const (
 	None       KeyKind = "None"
 )
 
-type KeyInfo struct {
+// The message to encode
-	Kind    KeyKind
+type Payload struct {
-	SymKey  []byte
+	Data    []byte   // Raw message payload
-	PrivKey ecdsa.PrivateKey
+	Padding []byte   // Used to align data size, since data size alone might reveal important metainformation.
+	Key     *KeyInfo // Contains the type of encryption to apply and the private key to use for signing the message
 }
 
-// NOTICE: Extracted from status-go
+// The decoded payload of a received message.
+type DecodedPayload struct {
+	Data      []byte           // Decoded message payload
+	Padding   []byte           // Used to align data size, since data size alone might reveal important metainformation.
+	PubKey    *ecdsa.PublicKey // The public key that signed the payload
+	Signature []byte
+}
+
+type KeyInfo struct {
+	Kind    KeyKind           // Indicates the type of encryption to use
+	SymKey  []byte            // If the encryption is Symmetric, a Symmetric key must be specified
+	PubKey  ecdsa.PublicKey   // If the encryption is Asymmetric, the public key of the message receptor must be specified
+	PrivKey *ecdsa.PrivateKey // Set a privkey if the message requires a signature
+
+}
+
+func (payload Payload) Encode(version uint32) ([]byte, error) {
+	switch version {
+	case 0:
+		return payload.Data, nil
+	case 1:
+		data, err := payload.v1Data()
+		if err != nil {
+			return nil, err
+		}
+
+		if payload.Key.PrivKey != nil {
+			data, err = sign(data, *payload.Key.PrivKey)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		switch payload.Key.Kind {
+		case Symmetric:
+			encoded, err := encryptSymmetric(data, payload.Key.SymKey)
+			if err != nil {
+				return nil, errors.New("Couldn't encrypt using symmetric key")
+			} else {
+				return encoded, nil
+			}
+		case Asymmetric:
+			encoded, err := encryptAsymmetric(data, &payload.Key.PubKey)
+			if err != nil {
+				return nil, errors.New("Couldn't encrypt using asymmetric key")
+			} else {
+				return encoded, nil
+			}
+		case None:
+			return nil, errors.New("Non supported KeyKind")
+		}
+	}
+	return nil, errors.New("Unsupported WakuMessage version")
+}
+
+func DecodePayload(message *protocol.WakuMessage, keyInfo *KeyInfo) (*DecodedPayload, error) {
+	switch *message.Version {
+	case uint32(0):
+		return &DecodedPayload{Data: message.Payload}, nil
+	case uint32(1):
+		switch keyInfo.Kind {
+		case Symmetric:
+			if keyInfo.SymKey == nil {
+				return nil, errors.New("Symmetric key is required")
+			}
+			fmt.Println("AAA")
+
+			decodedData, err := decryptSymmetric(message.Payload, keyInfo.SymKey)
+			if err != nil {
+				return nil, errors.New("Couldn't decrypt using symmetric key")
+			}
+
+			decodedPayload, err := validateAndParse(decodedData)
+			if err != nil {
+				return nil, err
+			}
+			fmt.Println("AAA")
+
+			return decodedPayload, nil
+		case Asymmetric:
+			if keyInfo.PrivKey == nil {
+				return nil, errors.New("Private key is required")
+			}
+
+			decodedData, err := decryptAsymmetric(message.Payload, keyInfo.PrivKey)
+			if err != nil {
+				return nil, errors.New("Couldn't decrypt using asymmetric key")
+			}
+
+			decodedPayload, err := validateAndParse(decodedData)
+			if err != nil {
+				return nil, err
+			}
+
+			return decodedPayload, nil
+		case None:
+			return nil, errors.New("Non supported KeyKind")
+		}
+	}
+	return nil, errors.New("Unsupported WakuMessage version")
+}
 
 const aesNonceLength = 12
 const aesKeyLength = 32
+const signatureFlag = byte(4)
+const flagsLength = 1
+const padSizeLimit = 256 // just an arbitrary number, could be changed without breaking the protocol
+const signatureLength = 65
+const sizeMask = byte(3)
 
 // Decrypts a message with a topic key, using AES-GCM-256.
 // nonce size should be 12 bytes (see cipher.gcmStandardNonceSize).
@@ -62,49 +171,23 @@ func decryptSymmetric(payload []byte, key []byte) ([]byte, error) {
 // Decrypts an encrypted payload with a private key.
 func decryptAsymmetric(payload []byte, key *ecdsa.PrivateKey) ([]byte, error) {
 	decrypted, err := ecies.ImportECDSA(key).Decrypt(payload, nil, nil)
-	if err == nil {
+	if err != nil {
 		return nil, err
 	}
 	return decrypted, err
 }
 
-func DecodePayload(message *protocol.WakuMessage, keyInfo *KeyInfo) ([]byte, error) {
-	switch *message.Version {
-	case uint32(0):
-		return message.Payload, nil
-	case uint32(1):
-		switch keyInfo.Kind {
-		case Symmetric:
-			decoded, err := decryptSymmetric(message.Payload, keyInfo.SymKey)
-			if err != nil {
-				return nil, errors.New("Couldn't decrypt using symmetric key")
-			} else {
-				return decoded, nil
-			}
-		case Asymmetric:
-			decoded, err := decryptAsymmetric(message.Payload, &keyInfo.PrivKey)
-			if err != nil {
-				return nil, errors.New("Couldn't decrypt using asymmetric key")
-			} else {
-				return decoded, nil
-			}
-		case None:
-			return nil, errors.New("Non supported KeyKind")
-		}
-	}
-	return nil, errors.New("Unsupported WakuMessage version")
-}
-
 // ValidatePublicKey checks the format of the given public key.
-func ValidatePublicKey(k *ecdsa.PublicKey) bool {
+func validatePublicKey(k *ecdsa.PublicKey) bool {
 	return k != nil && k.X != nil && k.Y != nil && k.X.Sign() != 0 && k.Y.Sign() != 0
 }
 
 // Encrypts and returns with a public key.
 func encryptAsymmetric(rawPayload []byte, key *ecdsa.PublicKey) ([]byte, error) {
-	if !ValidatePublicKey(key) {
+	if !validatePublicKey(key) {
 		return nil, errors.New("invalid public key provided for asymmetric encryption")
 	}
+
 	encrypted, err := ecies.Encrypt(crand.Reader, ecies.ImportECDSAPublic(key), rawPayload, nil, nil)
 	if err == nil {
 		return encrypted, nil
@@ -187,29 +270,154 @@ func generateSecureRandomData(length int) ([]byte, error) {
 	return res, nil
 }
 
-func Encode(rawPayload []byte, keyInfo *KeyInfo, version uint32) ([]byte, error) {
+func isMessageSigned(flags byte) bool {
-	switch version {
+	return (flags & signatureFlag) != 0
-	case 0:
+}
-		return rawPayload, nil
+
-	case 1:
+// sign calculates the cryptographic signature for the message,
-		switch keyInfo.Kind {
+// also setting the sign flag.
-		case Symmetric:
+func sign(data []byte, privKey ecdsa.PrivateKey) ([]byte, error) {
-			encoded, err := encryptSymmetric(rawPayload, keyInfo.SymKey)
+	result := make([]byte, len(data))
-			if err != nil {
+	copy(result, data)
-				return nil, errors.New("Couldn't encrypt using symmetric key")
+
-			} else {
+	if isMessageSigned(result[0]) {
-				return encoded, nil
+		// this should not happen, but no reason to panic
-			}
+		return result, nil
-		case Asymmetric:
+	}
-			encoded, err := encryptAsymmetric(rawPayload, &keyInfo.PrivKey.PublicKey)
+
-			if err != nil {
+	result[0] |= signatureFlag // it is important to set this flag before signing
-				return nil, errors.New("Couldn't encrypt using asymmetric key")
+	hash := crypto.Keccak256(result)
-			} else {
+	signature, err := crypto.Sign(hash, &privKey)
-				return encoded, nil
+
-			}
+	if err != nil {
-		case None:
+		result[0] &= (0xFF ^ signatureFlag) // clear the flag
-			return nil, errors.New("Non supported KeyKind")
+		return nil, err
-		}
+	}
-	}
+	result = append(result, signature...)
-	return nil, errors.New("Unsupported WakuMessage version")
+
+	return result, nil
+}
+
+func (payload Payload) v1Data() ([]byte, error) {
+	const payloadSizeFieldMaxSize = 4
+	result := make([]byte, 1, flagsLength+payloadSizeFieldMaxSize+len(payload.Data)+len(payload.Padding)+signatureLength+padSizeLimit)
+	result[0] = 0 // set all the flags to zero
+	result = payload.addPayloadSizeField(result)
+	result = append(result, payload.Data...)
+	result, err := payload.appendPadding(result)
+	return result, err
+}
+
+// addPayloadSizeField appends the auxiliary field containing the size of payload
+func (payload Payload) addPayloadSizeField(input []byte) []byte {
+	fieldSize := getSizeOfPayloadSizeField(payload.Data)
+	field := make([]byte, 4)
+	binary.LittleEndian.PutUint32(field, uint32(len(payload.Data)))
+	field = field[:fieldSize]
+	result := append(input, field...)
+	result[0] |= byte(fieldSize)
+	return result
+}
+
+// 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 (payload Payload) appendPadding(input []byte) ([]byte, error) {
+	if len(payload.Padding) != 0 {
+		// padding data was provided by the Dapp, just use it as is
+		result := append(input, payload.Padding...)
+		return result, nil
+	}
+
+	rawSize := flagsLength + getSizeOfPayloadSizeField(payload.Data) + len(payload.Data)
+	if payload.Key.PrivKey != nil {
+		rawSize += signatureLength
+	}
+	odd := rawSize % padSizeLimit
+	paddingSize := padSizeLimit - odd
+	pad := make([]byte, paddingSize)
+	_, err := crand.Read(pad)
+	if err != nil {
+		return nil, err
+	}
+	if !validateDataIntegrity(pad, paddingSize) {
+		return nil, errors.New("failed to generate random padding of size " + strconv.Itoa(paddingSize))
+	}
+	result := append(input, pad...)
+	return result, nil
+}
+
+func validateAndParse(input []byte) (*DecodedPayload, error) {
+	end := len(input)
+	if end < 1 {
+		return nil, errors.New("invalid message length")
+	}
+
+	msg := new(DecodedPayload)
+
+	if isMessageSigned(input[0]) {
+		end -= signatureLength
+		if end <= 1 {
+			return nil, errors.New("invalid message length")
+		}
+		msg.Signature = input[end : end+signatureLength]
+
+		var err error
+		msg.PubKey, err = msg.sigToPubKey(input)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	beg := 1
+	payloadSize := 0
+	sizeOfPayloadSizeField := int(input[0] & sizeMask) // number of bytes indicating the size of payload
+
+	if sizeOfPayloadSizeField != 0 {
+		if end < beg+sizeOfPayloadSizeField {
+			return nil, errors.New("invalid message length")
+		}
+		payloadSize = int(bytesToUintLittleEndian(input[beg : beg+sizeOfPayloadSizeField]))
+		beg += sizeOfPayloadSizeField
+		if beg+payloadSize > end {
+			return nil, errors.New("invalid message length")
+		}
+		msg.Data = input[beg : beg+payloadSize]
+	}
+
+	beg += payloadSize
+	msg.Padding = input[beg:end]
+
+	return msg, nil
+}
+
+// SigToPubKey returns the public key associated to the message's
+// signature.
+func (p *DecodedPayload) sigToPubKey(input []byte) (*ecdsa.PublicKey, error) {
+	defer func() { _ = recover() }() // in case of invalid signature
+	hash := crypto.Keccak256(input[0 : len(input)-signatureLength])
+	pub, err := crypto.SigToPub(hash, p.Signature)
+	if err != nil {
+		return nil, err
+	}
+
+	return pub, nil
+}
+
+// bytesToUintLittleEndian converts the slice to 64-bit unsigned integer.
+func bytesToUintLittleEndian(b []byte) (res uint64) {
+	mul := uint64(1)
+	for i := 0; i < len(b); i++ {
+		res += uint64(b[i]) * mul
+		mul *= 256
+	}
+	return res
 }