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// Package readpassword reads a password from the terminal of from stdin.
package readpassword
import (
"bytes"
"fmt"
"io"
"os"
"os/exec"
"strings"
"golang.org/x/term"
"github.com/rfjakob/gocryptfs/v2/internal/tlog"
)
const (
// 2kB limit like EncFS
maxPasswordLen = 2048
)
// Once tries to get a password from the user, either from the terminal, extpass, passfile
// or stdin. Leave "prompt" empty to use the default "Password: " prompt.
func Once(extpass []string, passfile []string, prompt string) ([]byte, error) {
if len(passfile) != 0 {
return readPassFileConcatenate(passfile)
}
if len(extpass) != 0 {
return readPasswordExtpass(extpass)
}
if prompt == "" {
prompt = "Password"
}
if !term.IsTerminal(int(os.Stdin.Fd())) {
return readPasswordStdin(prompt)
}
return readPasswordTerminal(prompt + ": ")
}
// Twice is the same as Once but will prompt twice if we get the password from
// the terminal.
func Twice(extpass []string, passfile []string) ([]byte, error) {
if len(passfile) != 0 {
return readPassFileConcatenate(passfile)
}
if len(extpass) != 0 {
return readPasswordExtpass(extpass)
}
if !term.IsTerminal(int(os.Stdin.Fd())) {
return readPasswordStdin("Password")
}
p1, err := readPasswordTerminal("Password: ")
if err != nil {
return nil, err
}
p2, err := readPasswordTerminal("Repeat: ")
if err != nil {
return nil, err
}
if !bytes.Equal(p1, p2) {
return nil, fmt.Errorf("passwords do not match")
}
// Wipe the password duplicate from memory
for i := range p2 {
p2[i] = 0
}
return p1, nil
}
// readPasswordTerminal reads a line from the terminal.
// Exits on read error or empty result.
func readPasswordTerminal(prompt string) ([]byte, error) {
fd := int(os.Stdin.Fd())
fmt.Fprint(os.Stderr, prompt)
// term.ReadPassword removes the trailing newline
p, err := term.ReadPassword(fd)
if err != nil {
return nil, fmt.Errorf("could not read password from terminal: %v", err)
}
fmt.Fprintf(os.Stderr, "\n")
if len(p) == 0 {
return nil, fmt.Errorf("password is empty")
}
return p, nil
}
// readPasswordStdin reads a line from stdin.
// It exits with a fatal error on read error or empty result.
func readPasswordStdin(prompt string) ([]byte, error) {
// This should make debugging situations like
// https://github.com/rfjakob/gocryptfs/issues/852
// easier. Only works on Linux, otherwise shows "?".
target, err := os.Readlink("/proc/self/fd/0")
if err != nil {
target = "?"
}
tlog.Info.Printf("Reading %s from stdin (connected to %q)", prompt, target)
p, err := readLineUnbuffered(os.Stdin)
if err != nil {
return nil, err
}
if len(p) == 0 {
return nil, fmt.Errorf("got empty %s from stdin", prompt)
}
return p, nil
}
// readPasswordExtpass executes the "extpass" program and returns the first line
// of the output.
// Exits on read error or empty result.
func readPasswordExtpass(extpass []string) ([]byte, error) {
var parts []string
if len(extpass) == 1 {
parts = strings.Split(extpass[0], " ")
} else {
parts = extpass
}
tlog.Info.Printf("Reading password from extpass program %q, arguments: %q\n", parts[0], parts[1:])
cmd := exec.Command(parts[0], parts[1:]...)
cmd.Stderr = os.Stderr
pipe, err := cmd.StdoutPipe()
if err != nil {
return nil, fmt.Errorf("extpass pipe setup failed: %v", err)
}
err = cmd.Start()
if err != nil {
return nil, fmt.Errorf("extpass cmd start failed: %v", err)
}
p, err := readLineUnbuffered(pipe)
if err != nil {
return nil, err
}
pipe.Close()
err = cmd.Wait()
if err != nil {
return nil, fmt.Errorf("extpass program returned an error: %v", err)
}
if len(p) == 0 {
return nil, fmt.Errorf("extpass: password is empty")
}
return p, nil
}
// readLineUnbuffered reads single bytes from "r" util it gets "\n" or EOF.
// The returned string does NOT contain the trailing "\n".
func readLineUnbuffered(r io.Reader) (l []byte, err error) {
b := make([]byte, 1)
for {
if len(l) > maxPasswordLen {
return nil, fmt.Errorf("fatal: maximum password length of %d bytes exceeded", maxPasswordLen)
}
n, err := r.Read(b)
if err == io.EOF {
return l, nil
}
if err != nil {
return nil, fmt.Errorf("readLineUnbuffered: %v", err)
}
if n == 0 {
continue
}
if b[0] == '\n' {
return l, nil
}
l = append(l, b...)
}
}
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