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path: root/file/file.go
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// Package file implements signify file format
package file

import (
	"bufio"
	"bytes"
	"encoding"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strings"
)

const (
	ModeSec   os.FileMode = 0600
	ModePub   os.FileMode = 0644
	ModeSig   os.FileMode = 0644
	untrusted             = "untrusted comment: "
)

// Original Error: "invalid comment in %s; must start with 'untrusted comment: '"
var ErrComment = errors.New("comment must start with 'untrusted comment: '")

func DecodeFile(fname string, u encoding.BinaryUnmarshaler) (string, []byte, error) {
	fd, err := os.Open(fname)
	if err != nil {
		return "", nil, err
	}
	defer fd.Close()
	return Decode(fd, u)
}

func DecodeString(data string, u encoding.BinaryUnmarshaler) (string, []byte, error) {
	r := strings.NewReader(data)
	return Decode(r, u)
}

func DecodeBytes(data []byte, u encoding.BinaryUnmarshaler) (string, []byte, error) {
	r := bytes.NewReader(data)
	return Decode(r, u)
}

func Decode(r io.Reader, u encoding.BinaryUnmarshaler) (string, []byte, error) {
	buf := bufio.NewReader(r)

	comment, err := buf.ReadString('\n')
	if err != nil {
		return "", nil, err
	}
	if !strings.HasPrefix(comment, untrusted) {
		return "", nil, ErrComment
	}
	comment = strings.TrimPrefix(comment, untrusted)
	comment = strings.TrimSpace(comment)

	raw, err := buf.ReadString('\n')
	if err != nil {
		return "", nil, err
	}
	b, err := base64.StdEncoding.DecodeString(raw)
	if err != nil {
		return "", nil, err
	}
	if err := u.UnmarshalBinary(b); err != nil {
		return "", nil, err
	}

	message, err := ioutil.ReadAll(buf)
	if err != nil {
		return "", nil, err
	}

	return comment, message, nil
}

func EncodeFile(fname string, perm os.FileMode, u encoding.BinaryMarshaler, comment string, msg []byte) error {
	fd, err := os.OpenFile(fname, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
	if err != nil {
		return err
	}
	defer fd.Close()
	return Encode(fd, u, comment, msg)
}

func Encode(w io.Writer, u encoding.BinaryMarshaler, comment string, msg []byte) error {
	raw, err := u.MarshalBinary()
	if err != nil {
		return err
	}
	fmt.Fprintf(w, "%s%s\n", untrusted, comment)
	fmt.Fprintf(w, "%s\n", base64.StdEncoding.EncodeToString(raw))
	w.Write(msg)
	return nil
}