1 5e70998a 2022-04-12 o // package aliases provides encoding and decoding of Unix alias(5) files
  2 5e70998a 2022-04-12 o // read by systems like Postfix and OpenBSD's smtpd(8).
  3 5e70998a 2022-04-12 o package aliases
  4 5e70998a 2022-04-12 o 
  5 5e70998a 2022-04-12 o import (
  6 5e70998a 2022-04-12 o 	"bufio"
  7 5e70998a 2022-04-12 o 	"errors"
  8 5e70998a 2022-04-12 o 	"fmt"
  9 5e70998a 2022-04-12 o 	"io"
 10 5e70998a 2022-04-12 o 	"os"
 11 5e70998a 2022-04-12 o 	"strings"
 12 5e70998a 2022-04-12 o )
 13 5e70998a 2022-04-12 o 
 14 5e70998a 2022-04-12 o type Aliases map[string]string
 15 5e70998a 2022-04-12 o 
 16 5e70998a 2022-04-12 o type Encoder struct {
 17 5e70998a 2022-04-12 o 	w *bufio.Writer
 18 5e70998a 2022-04-12 o }
 19 5e70998a 2022-04-12 o 
 20 5e70998a 2022-04-12 o func NewEncoder(w io.Writer) *Encoder {
 21 5e70998a 2022-04-12 o 	return &Encoder{bufio.NewWriter(w)}
 22 5e70998a 2022-04-12 o }
 23 5e70998a 2022-04-12 o 
 24 5e70998a 2022-04-12 o func (e *Encoder) Encode(m Aliases) error {
 25 5e70998a 2022-04-12 o 	defer e.w.Flush()
 26 5e70998a 2022-04-12 o 	for rcpt, dest := range m {
 27 5e70998a 2022-04-12 o 		_, err := e.w.WriteString(fmt.Sprintf("%s: %s\n", rcpt, dest))
 28 5e70998a 2022-04-12 o 		if err != nil {
 29 5e70998a 2022-04-12 o 			return fmt.Errorf("write alias %s: %w", rcpt, err)
 30 5e70998a 2022-04-12 o 		}
 31 5e70998a 2022-04-12 o 	}
 32 5e70998a 2022-04-12 o 	return nil
 33 5e70998a 2022-04-12 o }
 34 5e70998a 2022-04-12 o 
 35 5e70998a 2022-04-12 o func Parse(r io.Reader) (Aliases, error) {
 36 5e70998a 2022-04-12 o 	m := make(Aliases)
 37 5e70998a 2022-04-12 o 	sc := bufio.NewScanner(r)
 38 5e70998a 2022-04-12 o 	for sc.Scan() {
 39 5e70998a 2022-04-12 o 		line := strings.TrimSpace(sc.Text())
 40 5e70998a 2022-04-12 o 		if strings.HasPrefix(line, "#") {
 41 5e70998a 2022-04-12 o 			continue // skip comments
 42 5e70998a 2022-04-12 o 		}
 43 5e70998a 2022-04-12 o 		if line == "" {
 44 5e70998a 2022-04-12 o 			continue // skip blank lines
 45 5e70998a 2022-04-12 o 		}
 46 5e70998a 2022-04-12 o 
 47 5e70998a 2022-04-12 o 		rcpt, dest, err := parseLine(line)
 48 5e70998a 2022-04-12 o 		if err != nil {
 49 5e70998a 2022-04-12 o 			return nil, fmt.Errorf("parse: %w", err)
 50 5e70998a 2022-04-12 o 		}
 51 5e70998a 2022-04-12 o 		m[rcpt] = dest
 52 5e70998a 2022-04-12 o 	}
 53 5e70998a 2022-04-12 o 	if sc.Err() != nil {
 54 5e70998a 2022-04-12 o 		return nil, fmt.Errorf("parse: %w", sc.Err())
 55 5e70998a 2022-04-12 o 	}
 56 5e70998a 2022-04-12 o 	return m, nil
 57 5e70998a 2022-04-12 o }
 58 5e70998a 2022-04-12 o 
 59 5e70998a 2022-04-12 o // Load reads and returns named aliases file.
 60 5e70998a 2022-04-12 o func Load(name string) (Aliases, error) {
 61 5e70998a 2022-04-12 o 	f, err := os.Open(name)
 62 5e70998a 2022-04-12 o 	if err != nil {
 63 5e70998a 2022-04-12 o 		return nil, fmt.Errorf("load: %w", err)
 64 5e70998a 2022-04-12 o 	}
 65 5e70998a 2022-04-12 o 	defer f.Close()
 66 5e70998a 2022-04-12 o 	return Parse(f)
 67 5e70998a 2022-04-12 o }
 68 5e70998a 2022-04-12 o 
 69 5e70998a 2022-04-12 o // Put writes aliases to the named file.
 70 5e70998a 2022-04-12 o // The file is truncated if it already exists, otherwise it is created.
 71 5e70998a 2022-04-12 o func Put(m Aliases, name string) error {
 72 5e70998a 2022-04-12 o 	f, err := os.Create(name)
 73 5e70998a 2022-04-12 o 	if err != nil {
 74 5e70998a 2022-04-12 o 		return fmt.Errorf("put: %w", err)
 75 5e70998a 2022-04-12 o 	}
 76 5e70998a 2022-04-12 o 	defer f.Close()
 77 5e70998a 2022-04-12 o 	if err := NewEncoder(f).Encode(m); err != nil {
 78 5e70998a 2022-04-12 o 		return fmt.Errorf("put: %w", err)
 79 5e70998a 2022-04-12 o 	}
 80 5e70998a 2022-04-12 o 	return nil
 81 5e70998a 2022-04-12 o }
 82 5e70998a 2022-04-12 o 
 83 5e70998a 2022-04-12 o // parseLine parses a line of the form "foo: bar@example.com", returning two fields:
 84 5e70998a 2022-04-12 o // the recipient (foo) and destination (bar@example.com).
 85 5e70998a 2022-04-12 o func parseLine(s string) (recipient, destination string, err error) {
 86 5e70998a 2022-04-12 o 	a := strings.Fields(s)
 87 5e70998a 2022-04-12 o 	if len(a) > 2 {
 88 5e70998a 2022-04-12 o 		return "", "", fmt.Errorf("parse line: too many fields")
 89 5e70998a 2022-04-12 o 	} else if len(a) < 2 {
 90 5e70998a 2022-04-12 o 		return "", "", fmt.Errorf("parse line: too few fields")
 91 5e70998a 2022-04-12 o 	}
 92 5e70998a 2022-04-12 o 
 93 5e70998a 2022-04-12 o 	recipient, destination = strings.TrimSuffix(a[0], ":"), a[1]
 94 5e70998a 2022-04-12 o 	if !strings.HasSuffix(a[0], ":") {
 95 5e70998a 2022-04-12 o 		return "", "", fmt.Errorf("parse line: invalid recipient: expected %q, got %q", ":", recipient[len(recipient)])
 96 5e70998a 2022-04-12 o 	}
 97 4678774c 2022-04-21 o 	if strings.Contains(recipient, ":") {
 98 4678774c 2022-04-21 o 		return "", "", errors.New("parse line: recipient contains colon character")
 99 4678774c 2022-04-21 o 	}
100 5e70998a 2022-04-12 o 	if recipient == "" {
101 5e70998a 2022-04-12 o 		return "", "", errors.New("parse line: empty recipient")
102 5e70998a 2022-04-12 o 	}
103 5e70998a 2022-04-12 o 	if destination == "" {
104 5e70998a 2022-04-12 o 		return "", "", errors.New("parse line: empty destination")
105 5e70998a 2022-04-12 o 	}
106 5e70998a 2022-04-12 o 	return recipient, destination, nil
107 5e70998a 2022-04-12 o }