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// Copyright 2019 The age 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 armor provides a strict, streaming implementation of the ASCII
// armoring format for age files.
//
// It's PEM with type "AGE ENCRYPTED FILE", 64 character columns, no headers,
// and strict base64 decoding.
package armor
import (
"bufio"
"bytes"
"encoding/base64"
"errors"
"fmt"
"io"
"filippo.io/age/internal/format"
)
const (
Header = "-----BEGIN AGE ENCRYPTED FILE-----"
Footer = "-----END AGE ENCRYPTED FILE-----"
)
type armoredWriter struct {
started, closed bool
encoder *format.WrappedBase64Encoder
dst io.Writer
}
func (a *armoredWriter) Write(p []byte) (int, error) {
if !a.started {
if _, err := io.WriteString(a.dst, Header+"\n"); err != nil {
return 0, err
}
}
a.started = true
return a.encoder.Write(p)
}
func (a *armoredWriter) Close() error {
if a.closed {
return errors.New("ArmoredWriter already closed")
}
a.closed = true
if err := a.encoder.Close(); err != nil {
return err
}
footer := Footer + "\n"
if !a.encoder.LastLineIsEmpty() {
footer = "\n" + footer
}
_, err := io.WriteString(a.dst, footer)
return err
}
func NewWriter(dst io.Writer) io.WriteCloser {
// TODO: write a test with aligned and misaligned sizes, and 8 and 10 steps.
return &armoredWriter{
dst: dst,
encoder: format.NewWrappedBase64Encoder(base64.StdEncoding, dst),
}
}
type armoredReader struct {
r *bufio.Reader
started bool
unread []byte // backed by buf
buf [format.BytesPerLine]byte
err error
}
func NewReader(r io.Reader) io.Reader {
return &armoredReader{r: bufio.NewReader(r)}
}
func (r *armoredReader) Read(p []byte) (int, error) {
if len(r.unread) > 0 {
n := copy(p, r.unread)
r.unread = r.unread[n:]
return n, nil
}
if r.err != nil {
return 0, r.err
}
getLine := func() ([]byte, error) {
line, err := r.r.ReadBytes('\n')
if err == io.EOF && len(line) == 0 {
return nil, io.ErrUnexpectedEOF
} else if err != nil && err != io.EOF {
return nil, err
}
line = bytes.TrimSuffix(line, []byte("\n"))
line = bytes.TrimSuffix(line, []byte("\r"))
return line, nil
}
const maxWhitespace = 1024
drainTrailing := func() error {
buf, err := io.ReadAll(io.LimitReader(r.r, maxWhitespace))
if err != nil {
return err
}
if len(bytes.TrimSpace(buf)) != 0 {
return errors.New("trailing data after armored file")
}
if len(buf) == maxWhitespace {
return errors.New("too much trailing whitespace")
}
return io.EOF
}
var removedWhitespace int
for !r.started {
line, err := getLine()
if err != nil {
return 0, r.setErr(err)
}
// Ignore leading whitespace.
if len(bytes.TrimSpace(line)) == 0 {
removedWhitespace += len(line) + 1
if removedWhitespace > maxWhitespace {
return 0, r.setErr(errors.New("too much leading whitespace"))
}
continue
}
if string(line) != Header {
return 0, r.setErr(fmt.Errorf("invalid first line: %q", line))
}
r.started = true
}
line, err := getLine()
if err != nil {
return 0, r.setErr(err)
}
if string(line) == Footer {
return 0, r.setErr(drainTrailing())
}
if len(line) == 0 {
return 0, r.setErr(errors.New("empty line in armored data"))
}
if len(line) > format.ColumnsPerLine {
return 0, r.setErr(errors.New("column limit exceeded"))
}
r.unread = r.buf[:]
n, err := base64.StdEncoding.Strict().Decode(r.unread, line)
if err != nil {
return 0, r.setErr(err)
}
r.unread = r.unread[:n]
if n < format.BytesPerLine {
line, err := getLine()
if err != nil {
return 0, r.setErr(err)
}
if string(line) != Footer {
return 0, r.setErr(fmt.Errorf("invalid closing line: %q", line))
}
r.setErr(drainTrailing())
}
nn := copy(p, r.unread)
r.unread = r.unread[nn:]
return nn, nil
}
type Error struct {
err error
}
func (e *Error) Error() string {
return "invalid armor: " + e.err.Error()
}
func (e *Error) Unwrap() error {
return e.err
}
func (r *armoredReader) setErr(err error) error {
if err != io.EOF {
err = &Error{err}
}
r.err = err
return err
}
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