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package obfsvpn
import (
"context"
"encoding/base64"
"errors"
"fmt"
"net"
"strconv"
pt "git.torproject.org/pluggable-transports/goptlib.git"
"gitlab.com/yawning/obfs4.git/common/ntor"
"gitlab.com/yawning/obfs4.git/transports/base"
"gitlab.com/yawning/obfs4.git/transports/obfs4"
)
const (
ptArgNode = "node-id"
ptArgKey = "public-key"
ptArgMode = "iat-mode"
ptArgCert = "cert"
)
const (
certLength = ntor.NodeIDLength + ntor.PublicKeyLength
)
var (
ErrCannotDial = errors.New("cannot dial")
)
// IATMode determines the amount of time sent between packets.
type IATMode int
// Valid IAT modes.
const (
IATNone IATMode = iota
IATEnabled
IATParanoid
)
// Dialer contains options for connecting to an address and obfuscating traffic
// with the obfs4 protocol.
// It performs the ntor handshake on all dialed connections.
type Dialer struct {
Dialer net.Dialer
NodeID *ntor.NodeID
PublicKey *ntor.PublicKey
IATMode IATMode
DialFunc func(string, string) (net.Conn, error)
ptArgs pt.Args
clientFactory base.ClientFactory
}
func packCert(node *ntor.NodeID, public *ntor.PublicKey) string {
cert := make([]byte, 0, certLength)
cert = append(cert, node[:]...)
cert = append(cert, public[:]...)
return base64.RawStdEncoding.EncodeToString(cert)
}
func unpackCert(cert string) (*ntor.NodeID, *ntor.PublicKey, error) {
if l := base64.RawStdEncoding.DecodedLen(len(cert)); l != certLength {
return nil, nil, fmt.Errorf("cert length %d is invalid", l)
}
decoded, err := base64.RawStdEncoding.DecodeString(cert)
if err != nil {
return nil, nil, err
}
nodeID, err := ntor.NewNodeID(decoded[:ntor.NodeIDLength])
if err != nil {
return nil, nil, err
}
pubKey, err := ntor.NewPublicKey(decoded[ntor.NodeIDLength:])
if err != nil {
return nil, nil, err
}
return nodeID, pubKey, nil
}
// NewDialerFromCert creates a dialer from a node certificate.
func NewDialerFromCert(cert string) (*Dialer, error) {
nodeID, publicKey, err := unpackCert(cert)
if err != nil {
return nil, err
}
d := &Dialer{
NodeID: nodeID,
PublicKey: publicKey,
}
return d, nil
}
// NewDialerFromArgs creates a dialer from existing pluggable transport arguments.
func NewDialerFromArgs(args pt.Args) (*Dialer, error) {
clientFactory, err := (&obfs4.Transport{}).ClientFactory("")
if err != nil {
return nil, err
}
nodeHex, _ := args.Get(ptArgNode)
node, err := ntor.NodeIDFromHex(nodeHex)
if err != nil {
return nil, err
}
keyHex, _ := args.Get(ptArgKey)
pub, err := ntor.PublicKeyFromHex(keyHex)
if err != nil {
return nil, err
}
iatModeStr, _ := args.Get(ptArgMode)
iatMode, err := strconv.Atoi(iatModeStr)
if err != nil {
return nil, fmt.Errorf("error parsing IAT mode to integer: %w", err)
}
return &Dialer{
NodeID: node,
PublicKey: pub,
IATMode: IATMode(iatMode),
ptArgs: args,
clientFactory: clientFactory,
}, nil
}
/* what is this for? ----
// Wrap performs the ntor handshake over an existing conection.
// Wrap ignores the underlying Dialer config.
func (d *Dialer) Wrap(ctx context.Context, conn net.Conn) (net.Conn, error) {
return d.dial(ctx, "", "", func(network, address string) (net.Conn, error) {
return conn, nil
})
}
*/
// Dial creates an outbound net.Conn and performs the ntor handshake.
func (d *Dialer) Dial(network, address string) (net.Conn, error) {
ctx := context.Background()
return d.dial(ctx, network, address, func(network, address string) (net.Conn, error) {
conn, err := d.Dialer.DialContext(ctx, network, address)
if err != nil {
return nil, fmt.Errorf("%w: %s", ErrCannotDial, err)
}
return conn.(*net.TCPConn), err
})
}
// DialContext creates an outbound net.Conn and performs the ntor handshake.
func (d *Dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
return d.dial(ctx, network, address, func(network, address string) (net.Conn, error) {
return d.Dialer.DialContext(ctx, network, address)
})
}
func (d *Dialer) dial(ctx context.Context, network, address string, f func(network, address string) (net.Conn, error)) (net.Conn, error) {
if d.clientFactory == nil {
clientFactory, err := (&obfs4.Transport{}).ClientFactory("")
if err != nil {
return nil, err
}
d.clientFactory = clientFactory
}
ptArgs := d.Args()
args, err := d.clientFactory.ParseArgs(&ptArgs)
if err != nil {
return nil, err
}
if d.DialFunc != nil {
f = d.DialFunc
}
return d.clientFactory.Dial(network, address, f, args)
}
// Args returns the dialers options as pluggable transport arguments.
// The args include valid args for the "new" (version >= 0.0.3) bridge lines
// that use a unified "cert" argument as well as the legacy lines that use a
// separate Node ID and Public Key.
func (d *Dialer) Args() pt.Args {
if d.ptArgs == nil {
d.ptArgs = make(pt.Args)
d.ptArgs.Add(ptArgNode, d.NodeID.Hex())
d.ptArgs.Add(ptArgKey, d.PublicKey.Hex())
d.ptArgs.Add(ptArgMode, strconv.Itoa(int(d.IATMode)))
d.ptArgs.Add(ptArgCert, packCert(d.NodeID, d.PublicKey))
}
return d.ptArgs
}
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