132 lines
4.0 KiB
Go
132 lines
4.0 KiB
Go
// Contains the Whisper protocol Message element. For formal details please see
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// the specs at https://github.com/ethereum/wiki/wiki/Whisper-PoC-1-Protocol-Spec#messages.
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package whisper
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import (
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"crypto/ecdsa"
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"math/rand"
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"time"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/logger"
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"github.com/ethereum/go-ethereum/logger/glog"
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)
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// Message represents an end-user data packet to trasmit through the Whisper
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// protocol. These are wrapped into Envelopes that need not be understood by
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// intermediate nodes, just forwarded.
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type Message struct {
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Flags byte // First bit is signature presence, rest reserved and should be random
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Signature []byte
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Payload []byte
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Sent int64
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To *ecdsa.PublicKey
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}
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// Options specifies the exact way a message should be wrapped into an Envelope.
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type Options struct {
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From *ecdsa.PrivateKey
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To *ecdsa.PublicKey
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TTL time.Duration
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Topics []Topic
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}
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// NewMessage creates and initializes a non-signed, non-encrypted Whisper message.
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func NewMessage(payload []byte) *Message {
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// Construct an initial flag set: no signature, rest random
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flags := byte(rand.Intn(256))
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flags &= ^signatureFlag
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// Assemble and return the message
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return &Message{
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Flags: flags,
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Payload: payload,
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Sent: time.Now().Unix(),
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}
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}
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// Wrap bundles the message into an Envelope to transmit over the network.
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//
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// pow (Proof Of Work) controls how much time to spend on hashing the message,
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// inherently controlling its priority through the network (smaller hash, bigger
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// priority).
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//
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// The user can control the amount of identity, privacy and encryption through
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// the options parameter as follows:
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// - options.From == nil && options.To == nil: anonymous broadcast
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// - options.From != nil && options.To == nil: signed broadcast (known sender)
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// - options.From == nil && options.To != nil: encrypted anonymous message
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// - options.From != nil && options.To != nil: encrypted signed message
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func (self *Message) Wrap(pow time.Duration, options Options) (*Envelope, error) {
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// Use the default TTL if non was specified
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if options.TTL == 0 {
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options.TTL = DefaultTTL
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}
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// Sign and encrypt the message if requested
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if options.From != nil {
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if err := self.sign(options.From); err != nil {
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return nil, err
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}
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}
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if options.To != nil {
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if err := self.encrypt(options.To); err != nil {
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return nil, err
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}
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}
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// Wrap the processed message, seal it and return
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envelope := NewEnvelope(options.TTL, options.Topics, self)
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envelope.Seal(pow)
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return envelope, nil
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}
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// sign calculates and sets the cryptographic signature for the message , also
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// setting the sign flag.
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func (self *Message) sign(key *ecdsa.PrivateKey) (err error) {
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self.Flags |= signatureFlag
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self.Signature, err = crypto.Sign(self.hash(), key)
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return
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}
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// Recover retrieves the public key of the message signer.
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func (self *Message) Recover() *ecdsa.PublicKey {
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defer func() { recover() }() // in case of invalid signature
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// Short circuit if no signature is present
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if self.Signature == nil {
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return nil
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}
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// Otherwise try and recover the signature
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pub, err := crypto.SigToPub(self.hash(), self.Signature)
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if err != nil {
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glog.V(logger.Error).Infof("Could not get public key from signature: %v", err)
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return nil
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}
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return pub
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}
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// encrypt encrypts a message payload with a public key.
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func (self *Message) encrypt(key *ecdsa.PublicKey) (err error) {
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self.Payload, err = crypto.Encrypt(key, self.Payload)
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return
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}
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// decrypt decrypts an encrypted payload with a private key.
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func (self *Message) decrypt(key *ecdsa.PrivateKey) (err error) {
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self.Payload, err = crypto.Decrypt(key, self.Payload)
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return
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}
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// hash calculates the SHA3 checksum of the message flags and payload.
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func (self *Message) hash() []byte {
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return crypto.Sha3(append([]byte{self.Flags}, self.Payload...))
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}
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// bytes flattens the message contents (flags, signature and payload) into a
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// single binary blob.
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func (self *Message) bytes() []byte {
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return append([]byte{self.Flags}, append(self.Signature, self.Payload...)...)
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}
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