449 lines
9.4 KiB
Go
449 lines
9.4 KiB
Go
// Copyright (c) 2013-2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package btcwire
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import (
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"crypto/rand"
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"encoding/binary"
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"fmt"
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"github.com/conformal/fastsha256"
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"io"
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"math"
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)
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// Maximum payload size for a variable length integer.
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const MaxVarIntPayload = 9
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// readElement reads the next sequence of bytes from r using little endian
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// depending on the concrete type of element pointed to.
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func readElement(r io.Reader, element interface{}) error {
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var scratch [8]byte
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// Attempt to read the element based on the concrete type via fast
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// type assertions first.
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switch e := element.(type) {
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case *int32:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = int32(binary.LittleEndian.Uint32(b))
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return nil
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case *uint32:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = binary.LittleEndian.Uint32(b)
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return nil
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case *int64:
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b := scratch[0:8]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = int64(binary.LittleEndian.Uint64(b))
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return nil
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case *uint64:
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b := scratch[0:8]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = binary.LittleEndian.Uint64(b)
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return nil
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case *bool:
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b := scratch[0:1]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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if b[0] == 0x00 {
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*e = false
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} else {
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*e = true
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}
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return nil
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// Message header checksum.
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case *[4]byte:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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// Message header command.
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case *[commandSize]uint8:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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// IP address.
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case *[16]byte:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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case *ShaHash:
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_, err := io.ReadFull(r, e[:])
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if err != nil {
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return err
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}
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return nil
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case *ServiceFlag:
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b := scratch[0:8]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = ServiceFlag(binary.LittleEndian.Uint64(b))
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return nil
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case *InvType:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = InvType(binary.LittleEndian.Uint32(b))
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return nil
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case *BitcoinNet:
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b := scratch[0:4]
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_, err := io.ReadFull(r, b)
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if err != nil {
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return err
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}
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*e = BitcoinNet(binary.LittleEndian.Uint32(b))
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return nil
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}
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// Fall back to the slower binary.Read if a fast path was not available
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// above.
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return binary.Read(r, binary.LittleEndian, element)
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}
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// readElements reads multiple items from r. It is equivalent to multiple
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// calls to readElement.
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func readElements(r io.Reader, elements ...interface{}) error {
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for _, element := range elements {
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err := readElement(r, element)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// writeElement writes the little endian representation of element to w.
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func writeElement(w io.Writer, element interface{}) error {
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var scratch [8]byte
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// Attempt to write the element based on the concrete type via fast
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// type assertions first.
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switch e := element.(type) {
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case int32:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, uint32(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case uint32:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, e)
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case int64:
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b := scratch[0:8]
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binary.LittleEndian.PutUint64(b, uint64(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case uint64:
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b := scratch[0:8]
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binary.LittleEndian.PutUint64(b, e)
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case bool:
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b := scratch[0:1]
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if e == true {
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b[0] = 0x01
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} else {
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b[0] = 0x00
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}
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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// Message header checksum.
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case [4]byte:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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// Message header command.
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case [commandSize]uint8:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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// IP address.
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case [16]byte:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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case *ShaHash:
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_, err := w.Write(e[:])
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if err != nil {
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return err
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}
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return nil
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case ServiceFlag:
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b := scratch[0:8]
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binary.LittleEndian.PutUint64(b, uint64(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case InvType:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, uint32(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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case BitcoinNet:
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b := scratch[0:4]
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binary.LittleEndian.PutUint32(b, uint32(e))
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_, err := w.Write(b)
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if err != nil {
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return err
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}
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return nil
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}
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// Fall back to the slower binary.Write if a fast path was not available
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// above.
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return binary.Write(w, binary.LittleEndian, element)
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}
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// writeElements writes multiple items to w. It is equivalent to multiple
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// calls to writeElement.
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func writeElements(w io.Writer, elements ...interface{}) error {
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for _, element := range elements {
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err := writeElement(w, element)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// readVarInt reads a variable length integer from r and returns it as a uint64.
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func readVarInt(r io.Reader, pver uint32) (uint64, error) {
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var b [8]byte
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_, err := io.ReadFull(r, b[0:1])
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if err != nil {
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return 0, err
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}
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var rv uint64
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discriminant := uint8(b[0])
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switch discriminant {
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case 0xff:
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_, err := io.ReadFull(r, b[:])
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if err != nil {
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return 0, err
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}
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rv = binary.LittleEndian.Uint64(b[:])
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case 0xfe:
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_, err := io.ReadFull(r, b[0:4])
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if err != nil {
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return 0, err
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}
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rv = uint64(binary.LittleEndian.Uint32(b[:]))
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case 0xfd:
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_, err := io.ReadFull(r, b[0:2])
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if err != nil {
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return 0, err
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}
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rv = uint64(binary.LittleEndian.Uint16(b[:]))
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default:
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rv = uint64(discriminant)
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}
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return rv, nil
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}
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// writeVarInt serializes val to w using a variable number of bytes depending
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// on its value.
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func writeVarInt(w io.Writer, pver uint32, val uint64) error {
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if val < 0xfd {
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_, err := w.Write([]byte{uint8(val)})
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return err
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}
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if val <= math.MaxUint16 {
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var buf [3]byte
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buf[0] = 0xfd
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binary.LittleEndian.PutUint16(buf[1:], uint16(val))
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_, err := w.Write(buf[:])
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return err
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}
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if val <= math.MaxUint32 {
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var buf [5]byte
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buf[0] = 0xfe
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binary.LittleEndian.PutUint32(buf[1:], uint32(val))
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_, err := w.Write(buf[:])
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return err
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}
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var buf [9]byte
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buf[0] = 0xff
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binary.LittleEndian.PutUint64(buf[1:], val)
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_, err := w.Write(buf[:])
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return err
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}
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// VarIntSerializeSize returns the number of bytes it would take to serialize
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// val as a variable length integer.
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func VarIntSerializeSize(val uint64) int {
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// The value is small enough to be represented by itself, so it's
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// just 1 byte.
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if val < 0xfd {
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return 1
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}
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// Discriminant 1 byte plus 2 bytes for the uint16.
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if val <= math.MaxUint16 {
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return 3
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}
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// Discriminant 1 byte plus 4 bytes for the uint32.
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if val <= math.MaxUint32 {
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return 5
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}
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// Discriminant 1 byte plus 8 bytes for the uint64.
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return 9
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}
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// readVarString reads a variable length string from r and returns it as a Go
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// string. A varString is encoded as a varInt containing the length of the
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// string, and the bytes that represent the string itself. An error is returned
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// if the length is greater than the maximum block payload size, since it would
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// not be possible to put a varString of that size into a block anyways and it
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// also helps protect against memory exhuastion attacks and forced panics
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// through malformed messages.
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func readVarString(r io.Reader, pver uint32) (string, error) {
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count, err := readVarInt(r, pver)
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if err != nil {
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return "", err
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}
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// Prevent variable length strings that are larger than the maximum
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// message size. It would be possible to cause memory exhaustion and
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// panics without a sane upper bound on this count.
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if count > maxMessagePayload {
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str := fmt.Sprintf("variable length string is too long "+
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"[count %d, max %d]", count, maxMessagePayload)
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return "", messageError("readVarString", str)
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}
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buf := make([]byte, count)
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_, err = io.ReadFull(r, buf)
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if err != nil {
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return "", err
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}
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return string(buf), nil
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}
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// writeVarString serializes str to w as a varInt containing the length of the
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// string followed by the bytes that represent the string itself.
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func writeVarString(w io.Writer, pver uint32, str string) error {
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err := writeVarInt(w, pver, uint64(len(str)))
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if err != nil {
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return err
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}
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_, err = w.Write([]byte(str))
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if err != nil {
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return err
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}
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return nil
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}
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// randomUint64 returns a cryptographically random uint64 value. This
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// unexported version takes a reader primarily to ensure the error paths
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// can be properly tested by passing a fake reader in the tests.
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func randomUint64(r io.Reader) (uint64, error) {
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var b [8]byte
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n, err := r.Read(b[:])
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if n != len(b) {
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return 0, io.ErrShortBuffer
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}
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if err != nil {
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return 0, err
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}
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return binary.BigEndian.Uint64(b[:]), nil
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}
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// RandomUint64 returns a cryptographically random uint64 value.
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func RandomUint64() (uint64, error) {
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return randomUint64(rand.Reader)
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}
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// DoubleSha256 calculates sha256(sha256(b)) and returns the resulting bytes.
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func DoubleSha256(b []byte) []byte {
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hasher := fastsha256.New()
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hasher.Write(b)
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sum := hasher.Sum(nil)
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hasher.Reset()
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hasher.Write(sum)
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return hasher.Sum(nil)
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}
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