Can correctly accept faketls messages

mtglib/internal/faketls/clienthello/clienthello.go

@@ -0,0 +1,67 @@
+package clienthello
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/binary"
+	"fmt"
+	"time"
+
+	"github.com/9seconds/mtg/v2/mtglib/internal/faketls/record"
+)
+
+type ClientHello struct {
+	Time      time.Time
+	Digest    [RandomLen]byte
+	SessionID []byte
+}
+
+func ParseHandshake(secret, handshake []byte) (ClientHello, error) {
+	hello := ClientHello{}
+
+	if len(handshake) < MinLen {
+		return hello, fmt.Errorf("lengh of handshake is too small: %d", len(handshake))
+	}
+
+	if handshake[0] != HandshakeTypeClient {
+		return hello, fmt.Errorf("unknown handshake type %#x", handshake[0])
+	}
+
+	copy(hello.Digest[:], handshake[RandomOffset:])
+
+	for i := RandomOffset; i < RandomOffset+RandomLen; i++ {
+		handshake[i] = 0
+	}
+
+	rec := record.AcquireRecord()
+	defer record.ReleaseRecord(rec)
+
+	rec.Type = record.TypeHandshake
+	rec.Version = record.Version10
+	rec.Payload.Write(handshake)
+
+	// mac is calculated for the whole record, not only
+	// for the payload part
+	mac := hmac.New(sha256.New, secret)
+	rec.Dump(mac)
+
+	computedDigest := mac.Sum(nil)
+
+	for i := 0; i < RandomLen; i++ {
+		computedDigest[i] ^= hello.Digest[i]
+	}
+
+	for i := 0; i < RandomLen-4; i++ {
+		if computedDigest[i] != 0 {
+			return hello, ErrBadDigest
+		}
+	}
+
+	timestamp := int64(binary.LittleEndian.Uint32(computedDigest[RandomLen-4:]))
+	hello.Time = time.Unix(timestamp, 0)
+
+	hello.SessionID = make([]byte, handshake[SessionIDOffset])
+	copy(hello.SessionID, handshake[SessionIDOffset+1:])
+
+	return hello, nil
+}

mtglib/internal/faketls/clienthello/init.go

@@ -0,0 +1,17 @@
+package clienthello
+
+import "errors"
+
+const (
+	RandomLen       = 32
+	RandomOffset    = 6
+	SessionIDOffset = RandomOffset + RandomLen
+	MinLen          = SessionIDOffset + 1
+
+	HandshakeTypeClient = 0x01
+)
+
+var (
+	ErrBadDigest        = errors.New("bad digest")
+	ErrAntiReplayAttack = errors.New("antireplay attack was detected")
+)

mtglib/internal/faketls/record/init.go

@@ -0,0 +1,66 @@
+package record
+
+import "fmt"
+
+type Type uint8
+
+const (
+	TypeChangeCipherSpec Type = 0x14
+	TypeHandshake        Type = 0x16
+	TypeApplicationData  Type = 0x17
+)
+
+func (t Type) String() string {
+	switch t {
+	case TypeChangeCipherSpec:
+		return "changeCipher(0x14)"
+	case TypeHandshake:
+		return "handshake(0x16)"
+	case TypeApplicationData:
+		return "applicationData(0x17)"
+	}
+
+	return fmt.Sprintf("unknown(%#x)", byte(t))
+}
+
+func (t Type) Valid() error {
+	switch t {
+	case TypeChangeCipherSpec, TypeHandshake, TypeApplicationData:
+		return nil
+	}
+
+	return fmt.Errorf("unknown type %#x", byte(t))
+}
+
+type Version uint16
+
+const (
+	Version10 Version = 769 // 0x03 0x01
+	Version11 Version = 770 // 0x03 0x02
+	Version12 Version = 771 // 0x03 0x03
+	Version13 Version = 772 // 0x03 0x04
+)
+
+func (v Version) String() string {
+	switch v {
+	case Version10:
+		return "tls1.0"
+	case Version11:
+		return "tls1.1"
+	case Version12:
+		return "tls1.2"
+	case Version13:
+		return "tls1.3"
+	}
+
+	return fmt.Sprintf("tls(%d)", uint16(v))
+}
+
+func (v Version) Valid() error {
+	switch v {
+	case Version10, Version11, Version12, Version13:
+		return nil
+	}
+
+	return fmt.Errorf("unknown version %d", uint16(v))
+}

mtglib/internal/faketls/record/pools.go

@@ -0,0 +1,18 @@
+package record
+
+import "sync"
+
+var recordPool = sync.Pool{
+	New: func() interface{} {
+		return &Record{}
+	},
+}
+
+func AcquireRecord() *Record {
+	return recordPool.Get().(*Record)
+}
+
+func ReleaseRecord(r *Record) {
+	r.Reset()
+	recordPool.Put(r)
+}

mtglib/internal/faketls/record/record.go

@@ -0,0 +1,87 @@
+package record
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+type Record struct {
+	Type    Type
+	Version Version
+	Payload bytes.Buffer
+}
+
+func (r *Record) String() string {
+	return fmt.Sprintf("<tlsRecord(type=%v, version=%v, payload=%s)>",
+		r.Type,
+		r.Version,
+		base64.StdEncoding.EncodeToString(r.Payload.Bytes()))
+}
+
+func (r *Record) Reset() {
+	r.Payload.Reset()
+}
+
+func (r *Record) Read(reader io.Reader) error {
+	r.Reset()
+
+	buf := [2]byte{}
+
+	if _, err := io.ReadFull(reader, buf[:1]); err != nil {
+		return fmt.Errorf("cannot read type: %w", err)
+	}
+
+	r.Type = Type(buf[0])
+	if err := r.Type.Valid(); err != nil {
+		return fmt.Errorf("invalid type: %w", err)
+	}
+
+	if _, err := io.ReadFull(reader, buf[:]); err != nil {
+		return fmt.Errorf("cannot read version: %w", err)
+	}
+
+	r.Version = Version(binary.BigEndian.Uint16(buf[:]))
+	if err := r.Version.Valid(); err != nil {
+		return fmt.Errorf("invalid version: %w", err)
+	}
+
+	if _, err := io.ReadFull(reader, buf[:]); err != nil {
+		return fmt.Errorf("cannot read payload length: %w", err)
+	}
+
+	length := int64(binary.BigEndian.Uint16(buf[:]))
+	if _, err := io.CopyN(&r.Payload, reader, length); err != nil {
+		return fmt.Errorf("cannot read payload: %w", err)
+	}
+
+	return nil
+}
+
+func (r *Record) Dump(writer io.Writer) error {
+	buf := [2]byte{byte(r.Type), 0}
+
+	if _, err := writer.Write(buf[:1]); err != nil {
+		return fmt.Errorf("cannot dump type: %w", err)
+	}
+
+	binary.BigEndian.PutUint16(buf[:], uint16(r.Version))
+
+	if _, err := writer.Write(buf[:]); err != nil {
+		return fmt.Errorf("cannot dump version: %w", err)
+	}
+
+	binary.BigEndian.PutUint16(buf[:], uint16(r.Payload.Len()))
+
+	if _, err := writer.Write(buf[:]); err != nil {
+		return fmt.Errorf("cannot dump payload length: %w", err)
+	}
+
+	if _, err := writer.Write(r.Payload.Bytes()); err != nil {
+		return fmt.Errorf("cannot dump payload: %w", err)
+	}
+
+	return nil
+}