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// Package auth manages a htpasswd-compatible password file (bcrypt entries).
// The file format is one "username:$2a$..." entry per line.
// nginx auth_basic accepts this file directly via auth_basic_user_file.
package auth
import (
"bufio"
"fmt"
"os"
"strings"
"syscall"
"golang.org/x/crypto/bcrypt"
"golang.org/x/term"
)
type Auth struct {
path string
}
func New(path string) *Auth { return &Auth{path: path} }
func (a *Auth) AddUser(username string) error {
users, err := a.read()
if err != nil && !os.IsNotExist(err) {
return err
}
if _, exists := users[username]; exists {
return fmt.Errorf("user %q already exists", username)
}
pw, err := readPassword("Password: ")
if err != nil {
return err
}
confirm, err := readPassword("Confirm: ")
if err != nil {
return err
}
if pw != confirm {
return fmt.Errorf("passwords do not match")
}
hash, err := bcrypt.GenerateFromPassword([]byte(pw), bcrypt.DefaultCost)
if err != nil {
return err
}
users[username] = string(hash)
return a.write(users)
}
func (a *Auth) ChangePassword(username string) error {
users, err := a.read()
if err != nil {
return err
}
if _, exists := users[username]; !exists {
return fmt.Errorf("user %q not found", username)
}
pw, err := readPassword("New password: ")
if err != nil {
return err
}
confirm, err := readPassword("Confirm: ")
if err != nil {
return err
}
if pw != confirm {
return fmt.Errorf("passwords do not match")
}
hash, err := bcrypt.GenerateFromPassword([]byte(pw), bcrypt.DefaultCost)
if err != nil {
return err
}
users[username] = string(hash)
return a.write(users)
}
func (a *Auth) DeleteUser(username string) error {
users, err := a.read()
if err != nil {
return err
}
if _, exists := users[username]; !exists {
return fmt.Errorf("user %q not found", username)
}
delete(users, username)
return a.write(users)
}
func (a *Auth) ListUsers() ([]string, error) {
users, err := a.read()
if err != nil {
if os.IsNotExist(err) {
return nil, nil
}
return nil, err
}
names := make([]string, 0, len(users))
for k := range users {
names = append(names, k)
}
return names, nil
}
func (a *Auth) Verify(username, password string) (bool, error) {
users, err := a.read()
if err != nil {
return false, err
}
hash, ok := users[username]
if !ok {
return false, nil
}
err = bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
if err == bcrypt.ErrMismatchedHashAndPassword {
return false, nil
}
return err == nil, err
}
func (a *Auth) read() (map[string]string, error) {
f, err := os.Open(a.path)
if err != nil {
return nil, err
}
defer f.Close()
users := make(map[string]string)
scanner := bufio.NewScanner(f)
for scanner.Scan() {
line := strings.TrimSpace(scanner.Text())
if line == "" || strings.HasPrefix(line, "#") {
continue
}
user, hash, ok := strings.Cut(line, ":")
if ok {
users[user] = hash
}
}
return users, scanner.Err()
}
func (a *Auth) write(users map[string]string) error {
f, err := os.OpenFile(a.path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
defer f.Close()
w := bufio.NewWriter(f)
for user, hash := range users {
fmt.Fprintf(w, "%s:%s\n", user, hash)
}
return w.Flush()
}
func readPassword(prompt string) (string, error) {
fmt.Print(prompt)
b, err := term.ReadPassword(int(syscall.Stdin))
fmt.Println()
return string(b), err
}
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