92 lines
2.1 KiB
Go
92 lines
2.1 KiB
Go
|
// Copyright 2017 The Go Authors. All rights reserved.
|
||
|
|
// Use of this source code is governed by a BSD-style
|
||
|
|
// license that can be found in the LICENSE file.
|
||
|
|
|
||
|
|
package encoding
|
||
|
|
|
||
|
|
import (
|
||
|
|
"io"
|
||
|
|
"math/big"
|
||
|
|
"math/bits"
|
||
|
|
)
|
||
|
|
|
||
|
|
// An MPI is used to store the contents of a big integer, along with the bit
|
||
|
|
// length that was specified in the original input. This allows the MPI to be
|
||
|
|
// reserialized exactly.
|
||
|
|
type MPI struct {
|
||
|
|
bytes []byte
|
||
|
|
bitLength uint16
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewMPI returns a MPI initialized with bytes.
|
||
|
|
func NewMPI(bytes []byte) *MPI {
|
||
|
|
for len(bytes) != 0 && bytes[0] == 0 {
|
||
|
|
bytes = bytes[1:]
|
||
|
|
}
|
||
|
|
if len(bytes) == 0 {
|
||
|
|
bitLength := uint16(0)
|
||
|
|
return &MPI{bytes, bitLength}
|
||
|
|
}
|
||
|
|
bitLength := 8*uint16(len(bytes)-1) + uint16(bits.Len8(bytes[0]))
|
||
|
|
return &MPI{bytes, bitLength}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Bytes returns the decoded data.
|
||
|
|
func (m *MPI) Bytes() []byte {
|
||
|
|
return m.bytes
|
||
|
|
}
|
||
|
|
|
||
|
|
// BitLength is the size in bits of the decoded data.
|
||
|
|
func (m *MPI) BitLength() uint16 {
|
||
|
|
return m.bitLength
|
||
|
|
}
|
||
|
|
|
||
|
|
// EncodedBytes returns the encoded data.
|
||
|
|
func (m *MPI) EncodedBytes() []byte {
|
||
|
|
return append([]byte{byte(m.bitLength >> 8), byte(m.bitLength)}, m.bytes...)
|
||
|
|
}
|
||
|
|
|
||
|
|
// EncodedLength is the size in bytes of the encoded data.
|
||
|
|
func (m *MPI) EncodedLength() uint16 {
|
||
|
|
return uint16(2 + len(m.bytes))
|
||
|
|
}
|
||
|
|
|
||
|
|
// ReadFrom reads into m the next MPI from r.
|
||
|
|
func (m *MPI) ReadFrom(r io.Reader) (int64, error) {
|
||
|
|
var buf [2]byte
|
||
|
|
n, err := io.ReadFull(r, buf[0:])
|
||
|
|
if err != nil {
|
||
|
|
if err == io.EOF {
|
||
|
|
err = io.ErrUnexpectedEOF
|
||
|
|
}
|
||
|
|
return int64(n), err
|
||
|
|
}
|
||
|
|
|
||
|
|
m.bitLength = uint16(buf[0])<<8 | uint16(buf[1])
|
||
|
|
m.bytes = make([]byte, (int(m.bitLength)+7)/8)
|
||
|
|
|
||
|
|
nn, err := io.ReadFull(r, m.bytes)
|
||
|
|
if err == io.EOF {
|
||
|
|
err = io.ErrUnexpectedEOF
|
||
|
|
}
|
||
|
|
|
||
|
|
// remove leading zero bytes from malformed GnuPG encoded MPIs:
|
||
|
|
// https://bugs.gnupg.org/gnupg/issue1853
|
||
|
|
// for _, b := range m.bytes {
|
||
|
|
// if b != 0 {
|
||
|
|
// break
|
||
|
|
// }
|
||
|
|
// m.bytes = m.bytes[1:]
|
||
|
|
// m.bitLength -= 8
|
||
|
|
// }
|
||
|
|
|
||
|
|
return int64(n) + int64(nn), err
|
||
|
|
}
|
||
|
|
|
||
|
|
// SetBig initializes m with the bits from n.
|
||
|
|
func (m *MPI) SetBig(n *big.Int) *MPI {
|
||
|
|
m.bytes = n.Bytes()
|
||
|
|
m.bitLength = uint16(n.BitLen())
|
||
|
|
return m
|
||
|
|
}
|