lisp/password-cache.el

   1 ;;; password-cache.el --- Read passwords, possibly using a password cache.
   2
   3 ;; Copyright (C) 1999-2000, 2003-2011  Free Software Foundation, Inc.
   4
   5 ;; Author: Simon Josefsson <simon@josefsson.org>
   6 ;; Created: 2003-12-21
   7 ;; Keywords: password cache passphrase key
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software: you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation, either version 3 of the License, or
  14 ;; (at your option) any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;; Greatly influenced by pgg.el written by Daiki Ueno, with timer
  27 ;; fixes for XEmacs by Katsumi Yamaoka.  In fact, this is mostly just
  28 ;; a rip-off.
  29 ;;
  30 ;; (password-read "Password? " "test")
  31 ;; ;; Minibuffer prompt for password.
  32 ;;  => "foo"
  33 ;;
  34 ;; (password-cache-add "test" "foo")
  35 ;;  => nil
  36
  37 ;; (password-read "Password? " "test")
  38 ;; ;; No minibuffer prompt
  39 ;;  => "foo"
  40 ;;
  41 ;; (password-read "Password? " "test")
  42 ;; ;; No minibuffer prompt
  43 ;;  => "foo"
  44 ;;
  45 ;; ;; Wait `password-cache-expiry' seconds.
  46 ;;
  47 ;; (password-read "Password? " "test")
  48 ;; ;; Minibuffer prompt for password is back.
  49 ;;  => "foo"
  50
  51 ;;; Code:
  52
  53 ;; Options are autoloaded since they are used by eg mml-sec.el.
  54
  55 ;;;###autoload
  56 (defcustom password-cache t
  57   "Whether to cache passwords."
  58   :group 'password
  59   :type 'boolean)
  60
  61 ;;;###autoload
  62 (defcustom password-cache-expiry 16
  63   "How many seconds passwords are cached, or nil to disable expiring.
  64 Whether passwords are cached at all is controlled by `password-cache'."
  65   :group 'password
  66   :type '(choice (const :tag "Never" nil)
  67                  (integer :tag "Seconds")))
  68
  69 (defvar password-data (make-vector 7 0))
  70
  71 (defun password-read-from-cache (key)
  72   "Obtain passphrase for KEY from time-limited passphrase cache.
  73 Custom variables `password-cache' and `password-cache-expiry'
  74 regulate cache behavior."
  75   (and password-cache
  76        key
  77        (symbol-value (intern-soft key password-data))))
  78
  79 (defun password-in-cache-p (key)
  80   "Check if KEY is in the cache."
  81   (and password-cache
  82        key
  83        (intern-soft key password-data)))
  84
  85 (defun password-read (prompt &optional key)
  86   "Read password, for use with KEY, from user, or from cache if wanted.
  87 KEY indicate the purpose of the password, so the cache can
  88 separate passwords.  The cache is not used if KEY is nil.  It is
  89 typically a string.
  90 The variable `password-cache' control whether the cache is used."
  91   (or (password-read-from-cache key)
  92       (read-passwd prompt)))
  93
  94 (defun password-read-and-add (prompt &optional key)
  95   "Read password, for use with KEY, from user, or from cache if wanted.
  96 Then store the password in the cache.  Uses `password-read' and
  97 `password-cache-add'.  Custom variables `password-cache' and
  98 `password-cache-expiry' regulate cache behavior.
  99
 100 Warning: the password is cached without checking that it is
 101 correct.  It is better to check the password before caching.  If
 102 you must use this function, take care to check passwords and
 103 remove incorrect ones from the cache."
 104   (let ((password (password-read prompt key)))
 105     (when (and password key)
 106       (password-cache-add key password))
 107     password))
 108
 109 (make-obsolete 'password-read-and-add 'password-read "23.1")
 110
 111 (defun password-cache-remove (key)
 112   "Remove password indexed by KEY from password cache.
 113 This is typically run by a timer setup from `password-cache-add',
 114 but can be invoked at any time to forcefully remove passwords
 115 from the cache.  This may be useful when it has been detected
 116 that a password is invalid, so that `password-read' query the
 117 user again."
 118   (let ((password (symbol-value (intern-soft key password-data))))
 119     (when password
 120       (when (stringp password)
 121         (if (fboundp 'clear-string)
 122             (clear-string password)
 123           (fillarray password ?_)))
 124       (unintern key password-data))))
 125
 126 (defun password-cache-add (key password)
 127   "Add password to cache.
 128 The password is removed by a timer after `password-cache-expiry' seconds."
 129   (when (and password-cache-expiry (null (intern-soft key password-data)))
 130     (run-at-time password-cache-expiry nil
 131                  #'password-cache-remove
 132                  key))
 133   (set (intern key password-data) password)
 134   nil)
 135
 136 (defun password-reset ()
 137   "Clear the password cache."
 138   (interactive)
 139   (fillarray password-data 0))
 140
 141 (provide 'password-cache)
 142
 143 ;;; password-cache.el ends here