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// This file is part of gnunet-go, a GNUnet-implementation in Golang.
// Copyright (C) 2019-2022 Bernd Fix >Y<
//
// gnunet-go is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// gnunet-go 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
// Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// SPDX-License-Identifier: AGPL3.0-or-later
package message
import (
"bytes"
"crypto/sha512"
"encoding/binary"
"fmt"
"gnunet/enums"
"gnunet/util"
"time"
"github.com/bfix/gospel/crypto/ed25519"
"github.com/bfix/gospel/logger"
)
//----------------------------------------------------------------------
// HELLO-DHT
//
// A HELLO message is used to exchange information about transports with
// other DHT nodes. This struct is always followed by the actual network
// addresses of type "HelloAddress"
//----------------------------------------------------------------------
// HelloDHTMsg is a message send by peers to announce their presence
type HelloDHTMsg struct {
MsgSize uint16 `order:"big"` // total size of message
MsgType uint16 `order:"big"` // DHT_P2P_HELLO (157)
Reserved uint16 `order:"big"` // Reserved for further use
NumAddr uint16 `order:"big"` // Number of addresses in list
Signature []byte `size:"64"` // Signature
Expires util.AbsoluteTime `` // expiration time
AddrList []byte `size:"*"` // List of end-point addresses (HelloAddress)
}
// NewHelloMsgDHT creates an empty DHT_P2P_HELLO message.
func NewHelloDHTMsg() *HelloDHTMsg {
// return empty HelloMessage
exp := time.Now().Add(HelloAddressExpiration)
return &HelloDHTMsg{
MsgSize: 80, // size without 'AddrList'
MsgType: DHT_P2P_HELLO, // DHT_P2P_HELLO (157)
Reserved: 0, // not used here
NumAddr: 0, // start with empty address list
Signature: make([]byte, 64), // signature
Expires: util.NewAbsoluteTime(exp), // default expiration
AddrList: make([]byte, 0), // list of addresses
}
}
// Addresses returns the list of HelloAddress
func (m *HelloDHTMsg) Addresses() (list []*util.Address, err error) {
var addr *util.Address
var as string
num, pos := 0, 0
for {
// parse address string from stream
if as, pos = util.ReadCString(m.AddrList, pos); pos == -1 {
break
}
if addr, err = util.ParseAddress(as); err != nil {
return
}
addr.Expires = m.Expires
list = append(list, addr)
num++
}
// check numbers
if num != int(m.NumAddr) {
logger.Printf(logger.WARN, "[HelloDHTMsg] Number of addresses does not match (got %d, expected %d)", num, m.NumAddr)
}
return
}
// SetAddresses adds addresses to the HELLO message.
func (m *HelloDHTMsg) SetAddresses(list []*util.Address) {
// write addresses as blob and track earliest expiration
exp := util.NewAbsoluteTime(time.Now().Add(HelloAddressExpiration))
wrt := new(bytes.Buffer)
for _, addr := range list {
// check if address expires before current expire
if exp.Compare(addr.Expires) > 0 {
exp = addr.Expires
}
n, _ := wrt.Write([]byte(addr.URI()))
wrt.WriteByte(0)
m.MsgSize += uint16(n + 1)
}
m.AddrList = wrt.Bytes()
m.Expires = exp
m.NumAddr = uint16(len(list))
}
// String returns a human-readable representation of the message.
func (m *HelloDHTMsg) String() string {
addrs, _ := m.Addresses()
aList := ""
for i, a := range addrs {
if i > 0 {
aList += ","
}
aList += a.URI()
}
return fmt.Sprintf("HelloDHTMsg{expire:%s,addrs=%d:[%s]}", m.Expires, m.NumAddr, aList)
}
// Header returns the message header in a separate instance.
func (m *HelloDHTMsg) Header() *Header {
return &Header{m.MsgSize, m.MsgType}
}
// Verify the message signature
func (m *HelloDHTMsg) Verify(peer *util.PeerID) (bool, error) {
// assemble signed data and public key
sd := m.signedData()
pub := peer.PublicKey()
sig, err := ed25519.NewEdSignatureFromBytes(m.Signature)
if err != nil {
return false, err
}
return pub.EdVerify(sd, sig)
}
// Sign the HELLO data with private key
func (m *HelloDHTMsg) Sign(prv *ed25519.PrivateKey) error {
// assemble signed data
sd := m.signedData()
sig, err := prv.EdSign(sd)
if err != nil {
return err
}
m.Signature = sig.Bytes()
return nil
}
// signedData assembles a data block for sign and verify operations.
func (m *HelloDHTMsg) signedData() []byte {
// hash address block
hAddr := sha512.Sum512(m.AddrList)
var size uint32 = 80
purpose := uint32(enums.SIG_HELLO)
// assemble signed data
buf := new(bytes.Buffer)
binary.Write(buf, binary.BigEndian, size)
binary.Write(buf, binary.BigEndian, purpose)
binary.Write(buf, binary.BigEndian, m.Expires.Epoch()*1000000)
buf.Write(hAddr[:])
return buf.Bytes()
}
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