diff options
Diffstat (limited to 'whisper/whisperv6/message.go')
| -rw-r--r-- | whisper/whisperv6/message.go | 206 |
1 files changed, 98 insertions, 108 deletions
diff --git a/whisper/whisperv6/message.go b/whisper/whisperv6/message.go index b5c8279b1..7def35f14 100644 --- a/whisper/whisperv6/message.go +++ b/whisper/whisperv6/message.go @@ -25,6 +25,7 @@ import ( crand "crypto/rand" "encoding/binary" "errors" + mrand "math/rand" "strconv" "github.com/ethereum/go-ethereum/common" @@ -55,7 +56,7 @@ type sentMessage struct { } // ReceivedMessage represents a data packet to be received through the -// Whisper protocol. +// Whisper protocol and successfully decrypted. type ReceivedMessage struct { Raw []byte @@ -71,7 +72,7 @@ type ReceivedMessage struct { 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 + SymKeyHash common.Hash // The Keccak256Hash of the key EnvelopeHash common.Hash // Message envelope hash to act as a unique id } @@ -89,81 +90,60 @@ func (msg *ReceivedMessage) isAsymmetricEncryption() bool { // 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, len(params.Payload)+len(params.Padding)+signatureLength+padSizeLimit) + 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 - err := msg.appendPadding(params) - if err != nil { - return nil, err - } + msg.addPayloadSizeField(params.Payload) msg.Raw = append(msg.Raw, params.Payload...) - return &msg, nil + err := msg.appendPadding(params) + return &msg, err } -// getSizeOfLength returns the number of bytes necessary to encode the entire size padding (including these bytes) -func getSizeOfLength(b []byte) (sz int, err error) { - sz = intSize(len(b)) // first iteration - sz = intSize(len(b) + sz) // second iteration - if sz > 3 { - err = errors.New("oversized padding parameter") - } - return sz, 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) } -// sizeOfIntSize returns minimal number of bytes necessary to encode an integer value -func intSize(i int) (s int) { - for s = 1; i >= 256; s++ { - i /= 256 +// 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 pseudorandom padding bytes and sets the padding flag. -// The last byte contains the size of padding (thus, its size must not exceed 256). +// 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 { - rawSize := len(params.Payload) + 1 - if params.Src != nil { - rawSize += signatureLength + 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 } - if params.KeySym != nil { - rawSize += AESNonceLength + rawSize := flagsLength + getSizeOfPayloadSizeField(params.Payload) + len(params.Payload) + if params.Src != nil { + rawSize += signatureLength } odd := rawSize % padSizeLimit - - if len(params.Padding) != 0 { - padSize := len(params.Padding) - padLengthSize, err := getSizeOfLength(params.Padding) - if err != nil { - return err - } - totalPadSize := padSize + padLengthSize - buf := make([]byte, 8) - binary.LittleEndian.PutUint32(buf, uint32(totalPadSize)) - buf = buf[:padLengthSize] - msg.Raw = append(msg.Raw, buf...) - msg.Raw = append(msg.Raw, params.Padding...) - msg.Raw[0] |= byte(padLengthSize) // number of bytes indicating the padding size - } else if odd != 0 { - totalPadSize := padSizeLimit - odd - if totalPadSize > 255 { - // this algorithm is only valid if padSizeLimit < 256. - // if padSizeLimit will ever change, please fix the algorithm - // (please see also ReceivedMessage.extractPadding() function). - panic("please fix the padding algorithm before releasing new version") - } - buf := make([]byte, totalPadSize) - _, err := crand.Read(buf[1:]) - if err != nil { - return err - } - if totalPadSize > 6 && !validateSymmetricKey(buf) { - return errors.New("failed to generate random padding of size " + strconv.Itoa(totalPadSize)) - } - buf[0] = byte(totalPadSize) - msg.Raw = append(msg.Raw, buf...) - msg.Raw[0] |= byte(0x1) // number of bytes indicating the padding size + 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 } @@ -176,11 +156,11 @@ func (msg *sentMessage) sign(key *ecdsa.PrivateKey) error { return nil } - msg.Raw[0] |= signatureFlag + 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] &= ^signatureFlag // clear the flag + msg.Raw[0] &= (0xFF ^ signatureFlag) // clear the flag return err } msg.Raw = append(msg.Raw, signature...) @@ -202,10 +182,9 @@ func (msg *sentMessage) encryptAsymmetric(key *ecdsa.PublicKey) error { // 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 !validateSymmetricKey(key) { - return errors.New("invalid key provided for symmetric encryption") + 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 @@ -214,20 +193,46 @@ func (msg *sentMessage) encryptSymmetric(key []byte) (err error) { if err != nil { return err } - - // never use more than 2^32 random nonces with a given key - salt := make([]byte, aesgcm.NonceSize()) - _, err = crand.Read(salt) + salt, err := generateSecureRandomData(aesNonceLength) // never use more than 2^32 random nonces with a given key if err != nil { return err - } else if !validateSymmetricKey(salt) { - return errors.New("crypto/rand failed to generate salt") } - - msg.Raw = append(aesgcm.Seal(nil, salt, msg.Raw, nil), salt...) + 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 { @@ -259,12 +264,11 @@ func (msg *sentMessage) Wrap(options *MessageParams) (envelope *Envelope, err er // 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 { - // In v6, symmetric messages are expected to contain the 12-byte - // "salt" at the end of the payload. - if len(msg.Raw) < AESNonceLength { + // 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:] + salt := msg.Raw[len(msg.Raw)-aesNonceLength:] block, err := aes.NewCipher(key) if err != nil { @@ -274,11 +278,7 @@ func (msg *ReceivedMessage) decryptSymmetric(key []byte) error { if err != nil { return err } - if len(salt) != aesgcm.NonceSize() { - log.Error("decrypting the message", "AES salt size", len(salt)) - return errors.New("wrong AES salt size") - } - decrypted, err := aesgcm.Open(nil, salt, msg.Raw[:len(msg.Raw)-AESNonceLength], nil) + decrypted, err := aesgcm.Open(nil, salt, msg.Raw[:len(msg.Raw)-aesNonceLength], nil) if err != nil { return err } @@ -296,8 +296,8 @@ func (msg *ReceivedMessage) decryptAsymmetric(key *ecdsa.PrivateKey) error { return err } -// Validate checks the validity and extracts the fields in case of success -func (msg *ReceivedMessage) Validate() bool { +// 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 @@ -308,40 +308,30 @@ func (msg *ReceivedMessage) Validate() bool { if end <= 1 { return false } - msg.Signature = msg.Raw[end:] + msg.Signature = msg.Raw[end : end+signatureLength] msg.Src = msg.SigToPubKey() if msg.Src == nil { return false } } - padSize, ok := msg.extractPadding(end) - if !ok { - 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] } - msg.Payload = msg.Raw[1+padSize : end] + beg += payloadSize + msg.Padding = msg.Raw[beg: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 indicating the entire size of padding (including these bytes) - // could be zero -- it means no padding - if sz != 0 { - paddingSize = int(bytesToUintLittleEndian(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 -} - // SigToPubKey returns the public key associated to the message's // signature. func (msg *ReceivedMessage) SigToPubKey() *ecdsa.PublicKey { @@ -355,7 +345,7 @@ func (msg *ReceivedMessage) SigToPubKey() *ecdsa.PublicKey { return pub } -// hash calculates the SHA3 checksum of the message flags, payload and padding. +// 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 |