github.com/ylsgit/go-ethereum@v1.6.5/whisper/whisperv2/envelope.go (about)

     1  // Copyright 2014 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  // Contains the Whisper protocol Envelope element. For formal details please see
    18  // the specs at https://github.com/ethereum/wiki/wiki/Whisper-PoC-1-Protocol-Spec#envelopes.
    19  
    20  package whisperv2
    21  
    22  import (
    23  	"crypto/ecdsa"
    24  	"encoding/binary"
    25  	"fmt"
    26  	"math/big"
    27  	"time"
    28  
    29  	"github.com/ethereum/go-ethereum/common"
    30  	"github.com/ethereum/go-ethereum/common/math"
    31  	"github.com/ethereum/go-ethereum/crypto"
    32  	"github.com/ethereum/go-ethereum/crypto/ecies"
    33  	"github.com/ethereum/go-ethereum/rlp"
    34  )
    35  
    36  // Envelope represents a clear-text data packet to transmit through the Whisper
    37  // network. Its contents may or may not be encrypted and signed.
    38  type Envelope struct {
    39  	Expiry uint32 // Whisper protocol specifies int32, really should be int64
    40  	TTL    uint32 // ^^^^^^
    41  	Topics []Topic
    42  	Data   []byte
    43  	Nonce  uint32
    44  
    45  	hash common.Hash // Cached hash of the envelope to avoid rehashing every time
    46  }
    47  
    48  // NewEnvelope wraps a Whisper message with expiration and destination data
    49  // included into an envelope for network forwarding.
    50  func NewEnvelope(ttl time.Duration, topics []Topic, msg *Message) *Envelope {
    51  	return &Envelope{
    52  		Expiry: uint32(time.Now().Add(ttl).Unix()),
    53  		TTL:    uint32(ttl.Seconds()),
    54  		Topics: topics,
    55  		Data:   msg.bytes(),
    56  		Nonce:  0,
    57  	}
    58  }
    59  
    60  // Seal closes the envelope by spending the requested amount of time as a proof
    61  // of work on hashing the data.
    62  func (self *Envelope) Seal(pow time.Duration) {
    63  	d := make([]byte, 64)
    64  	copy(d[:32], self.rlpWithoutNonce())
    65  
    66  	finish, bestBit := time.Now().Add(pow).UnixNano(), 0
    67  	for nonce := uint32(0); time.Now().UnixNano() < finish; {
    68  		for i := 0; i < 1024; i++ {
    69  			binary.BigEndian.PutUint32(d[60:], nonce)
    70  
    71  			d := new(big.Int).SetBytes(crypto.Keccak256(d))
    72  			firstBit := math.FirstBitSet(d)
    73  			if firstBit > bestBit {
    74  				self.Nonce, bestBit = nonce, firstBit
    75  			}
    76  			nonce++
    77  		}
    78  	}
    79  }
    80  
    81  // rlpWithoutNonce returns the RLP encoded envelope contents, except the nonce.
    82  func (self *Envelope) rlpWithoutNonce() []byte {
    83  	enc, _ := rlp.EncodeToBytes([]interface{}{self.Expiry, self.TTL, self.Topics, self.Data})
    84  	return enc
    85  }
    86  
    87  // Open extracts the message contained within a potentially encrypted envelope.
    88  func (self *Envelope) Open(key *ecdsa.PrivateKey) (msg *Message, err error) {
    89  	// Split open the payload into a message construct
    90  	data := self.Data
    91  
    92  	message := &Message{
    93  		Flags: data[0],
    94  		Sent:  time.Unix(int64(self.Expiry-self.TTL), 0),
    95  		TTL:   time.Duration(self.TTL) * time.Second,
    96  		Hash:  self.Hash(),
    97  	}
    98  	data = data[1:]
    99  
   100  	if message.Flags&signatureFlag == signatureFlag {
   101  		if len(data) < signatureLength {
   102  			return nil, fmt.Errorf("unable to open envelope. First bit set but len(data) < len(signature)")
   103  		}
   104  		message.Signature, data = data[:signatureLength], data[signatureLength:]
   105  	}
   106  	message.Payload = data
   107  
   108  	// Decrypt the message, if requested
   109  	if key == nil {
   110  		return message, nil
   111  	}
   112  	err = message.decrypt(key)
   113  	switch err {
   114  	case nil:
   115  		return message, nil
   116  
   117  	case ecies.ErrInvalidPublicKey: // Payload isn't encrypted
   118  		return message, err
   119  
   120  	default:
   121  		return nil, fmt.Errorf("unable to open envelope, decrypt failed: %v", err)
   122  	}
   123  }
   124  
   125  // Hash returns the SHA3 hash of the envelope, calculating it if not yet done.
   126  func (self *Envelope) Hash() common.Hash {
   127  	if (self.hash == common.Hash{}) {
   128  		enc, _ := rlp.EncodeToBytes(self)
   129  		self.hash = crypto.Keccak256Hash(enc)
   130  	}
   131  	return self.hash
   132  }
   133  
   134  // DecodeRLP decodes an Envelope from an RLP data stream.
   135  func (self *Envelope) DecodeRLP(s *rlp.Stream) error {
   136  	raw, err := s.Raw()
   137  	if err != nil {
   138  		return err
   139  	}
   140  	// The decoding of Envelope uses the struct fields but also needs
   141  	// to compute the hash of the whole RLP-encoded envelope. This
   142  	// type has the same structure as Envelope but is not an
   143  	// rlp.Decoder so we can reuse the Envelope struct definition.
   144  	type rlpenv Envelope
   145  	if err := rlp.DecodeBytes(raw, (*rlpenv)(self)); err != nil {
   146  		return err
   147  	}
   148  	self.hash = crypto.Keccak256Hash(raw)
   149  	return nil
   150  }