lisp/mail/hashcash.el

   1 ;;; hashcash.el --- Add hashcash payments to email
   2
   3 ;; Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009  Free Software Foundation
   4
   5 ;; Written by: Paul Foley <mycroft@actrix.gen.nz> (1997-2002)
   6 ;; Maintainer: Paul Foley <mycroft@actrix.gen.nz>
   7 ;; Keywords: mail, hashcash
   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 ;; The hashcash binary is at http://www.hashcash.org/.
  27 ;;
  28 ;; Call mail-add-payment to add a hashcash payment to a mail message
  29 ;; in the current buffer.
  30 ;;
  31 ;; Call mail-add-payment-async after writing the addresses but before
  32 ;; writing the mail to start calculating the hashcash payment
  33 ;; asynchronously.
  34 ;;
  35 ;; The easiest way to do this automatically for all outgoing mail
  36 ;; is to set `message-generate-hashcash' to t.  If you want more
  37 ;; control, try the following hooks.
  38 ;;
  39 ;; To automatically add payments to all outgoing mail when sending:
  40 ;;    (add-hook 'message-send-hook 'mail-add-payment)
  41 ;;
  42 ;; To start calculations automatically when addresses are prefilled:
  43 ;;    (add-hook 'message-setup-hook 'mail-add-payment-async)
  44 ;;
  45 ;; To check whether calculations are done before sending:
  46 ;;    (add-hook 'message-send-hook 'hashcash-wait-or-cancel)
  47
  48 ;;; Code:
  49
  50 (eval-and-compile
  51   (unless (fboundp 'declare-function) (defmacro declare-function (&rest r))))
  52
  53 (eval-when-compile (require 'cl))       ; for case
  54
  55 (defgroup hashcash nil
  56   "Hashcash configuration."
  57   :group 'mail)
  58
  59 (defcustom hashcash-default-payment 20
  60   "*The default number of bits to pay to unknown users.
  61 If this is zero, no payment header will be generated.
  62 See `hashcash-payment-alist'."
  63   :type 'integer
  64   :group 'hashcash)
  65
  66 (defcustom hashcash-payment-alist '()
  67   "*An association list mapping email addresses to payment amounts.
  68 Elements may consist of (ADDR AMOUNT) or (ADDR STRING AMOUNT), where
  69 ADDR is the email address of the intended recipient and AMOUNT is
  70 the value of hashcash payment to be made to that user.  STRING, if
  71 present, is the string to be hashed; if not present ADDR will be used."
  72   :type '(repeat (choice (list :tag "Normal"
  73                                (string :name "Address")
  74                                (integer :name "Amount"))
  75                          (list :tag "Replace hash input"
  76                                (string :name "Address")
  77                                (string :name "Hash input")
  78                                (integer :name "Amount"))))
  79   :group 'hashcash)
  80
  81 (defcustom hashcash-default-accept-payment 20
  82   "*The default minimum number of bits to accept on incoming payments."
  83   :type 'integer
  84   :group 'hashcash)
  85
  86 (defcustom hashcash-accept-resources `((,user-mail-address nil))
  87   "*An association list mapping hashcash resources to payment amounts.
  88 Resources named here are to be accepted in incoming payments.  If the
  89 corresponding AMOUNT is NIL, the value of `hashcash-default-accept-payment'
  90 is used instead."
  91   :group 'hashcash)
  92
  93 (defcustom hashcash-path (executable-find "hashcash")
  94   "*The path to the hashcash binary."
  95   :group 'hashcash)
  96
  97 (defcustom hashcash-extra-generate-parameters nil
  98   "*A list of parameter strings passed to `hashcash-path' when minting.
  99 For example, you may want to set this to '(\"-Z2\") to reduce header length."
 100   :type '(repeat string)
 101   :group 'hashcash)
 102
 103 (defcustom hashcash-double-spend-database "hashcash.db"
 104   "*The path to the double-spending database."
 105   :group 'hashcash)
 106
 107 (defcustom hashcash-in-news nil
 108   "*Specifies whether or not hashcash payments should be made to newsgroups."
 109   :type 'boolean
 110   :group 'hashcash)
 111
 112 (defvar hashcash-process-alist nil
 113   "Alist of asynchronous hashcash processes and buffers.")
 114
 115 (require 'mail-utils)
 116
 117 (eval-and-compile
 118   (unless (fboundp 'declare-function) (defmacro declare-function (&rest r)))
 119
 120   (if (fboundp 'point-at-bol)
 121       (defalias 'hashcash-point-at-bol 'point-at-bol)
 122     (defalias 'hashcash-point-at-bol 'line-beginning-position))
 123
 124   (if (fboundp 'point-at-eol)
 125       (defalias 'hashcash-point-at-eol 'point-at-eol)
 126     (defalias 'hashcash-point-at-eol 'line-end-position)))
 127
 128 (defun hashcash-strip-quoted-names (addr)
 129   (setq addr (mail-strip-quoted-names addr))
 130   (if (and addr (string-match "\\`\\([^+@]+\\)\\+[^@]*\\(@.+\\)" addr))
 131       (concat (match-string 1 addr) (match-string 2 addr))
 132     addr))
 133
 134 (declare-function  message-narrow-to-headers-or-head "message" ())
 135 (declare-function  message-fetch-field "message" (header &optional not-all))
 136 (declare-function  message-goto-eoh "message" ())
 137 (declare-function  message-narrow-to-headers "message" ())
 138
 139 (defun hashcash-token-substring ()
 140   (save-excursion
 141     (let ((token ""))
 142       (loop
 143         (setq token
 144           (concat token (buffer-substring (point) (hashcash-point-at-eol))))
 145         (goto-char (hashcash-point-at-eol))
 146         (forward-char 1)
 147         (unless (looking-at "[ \t]") (return token))
 148         (while (looking-at "[ \t]") (forward-char 1))))))
 149
 150 (defun hashcash-payment-required (addr)
 151   "Return the hashcash payment value required for the given address."
 152   (let ((val (assoc addr hashcash-payment-alist)))
 153     (or (nth 2 val) (nth 1 val) hashcash-default-payment)))
 154
 155 (defun hashcash-payment-to (addr)
 156   "Return the string with which hashcash payments should collide."
 157   (let ((val (assoc addr hashcash-payment-alist)))
 158     (or (nth 1 val) (nth 0 val) addr)))
 159
 160 (defun hashcash-generate-payment (str val)
 161   "Generate a hashcash payment by finding a VAL-bit collison on STR."
 162   (if (and (> val 0)
 163            hashcash-path)
 164       (save-excursion
 165         (set-buffer (get-buffer-create " *hashcash*"))
 166         (erase-buffer)
 167         (apply 'call-process hashcash-path nil t nil
 168                "-m" "-q" "-b" (number-to-string val) str
 169                hashcash-extra-generate-parameters)
 170         (goto-char (point-min))
 171         (hashcash-token-substring))
 172     (error "No `hashcash' binary found")))
 173
 174 (defun hashcash-generate-payment-async (str val callback)
 175   "Generate a hashcash payment by finding a VAL-bit collison on STR.
 176 Return immediately.  Call CALLBACK with process and result when ready."
 177   (if (and (> val 0)
 178            hashcash-path)
 179       (let ((process (apply 'start-process "hashcash" nil
 180                             hashcash-path "-m" "-q"
 181                             "-b" (number-to-string val) str
 182                             hashcash-extra-generate-parameters)))
 183         (setq hashcash-process-alist (cons
 184                                       (cons process (current-buffer))
 185                                       hashcash-process-alist))
 186         (set-process-filter process `(lambda (process output)
 187                                        (funcall ,callback process output))))
 188     (funcall callback nil nil)))
 189
 190 (defun hashcash-check-payment (token str val)
 191   "Check the validity of a hashcash payment."
 192   (if hashcash-path
 193       (zerop (call-process hashcash-path nil nil nil "-c"
 194                            "-d" "-f" hashcash-double-spend-database
 195                            "-b" (number-to-string val)
 196                            "-r" str
 197                            token))
 198     (progn
 199       (message "No hashcash binary found")
 200       (sleep-for 1)
 201       nil)))
 202
 203 (defun hashcash-version (token)
 204   "Find the format version of a hashcash token."
 205   ;; Version 1.2 looks like n:yymmdd:rrrrr:xxxxxxxxxxxxxxxx
 206   ;;   This carries its own version number embedded in the token,
 207   ;;   so no further format number changes should be necessary
 208   ;;   in the X-Payment header.
 209   ;;
 210   ;; Version 1.1 looks like yymmdd:rrrrr:xxxxxxxxxxxxxxxx
 211   ;;   You need to upgrade your hashcash binary.
 212   ;;
 213   ;; Version 1.0 looked like nnnnnrrrrrxxxxxxxxxxxxxxxx
 214   ;;   This is no longer supported.
 215   (cond ((equal (aref token 1) ?:) 1.2)
 216         ((equal (aref token 6) ?:) 1.1)
 217         (t (error "Unknown hashcash format version"))))
 218
 219 (defun hashcash-already-paid-p (recipient)
 220   "Check for hashcash token to RECIPIENT in current buffer."
 221   (save-excursion
 222     (save-restriction
 223       (message-narrow-to-headers-or-head)
 224       (let ((token (message-fetch-field "x-hashcash"))
 225             (case-fold-search t))
 226         (and (stringp token)
 227              (string-match (regexp-quote recipient) token))))))
 228
 229 ;;;###autoload
 230 (defun hashcash-insert-payment (arg)
 231   "Insert X-Payment and X-Hashcash headers with a payment for ARG"
 232   (interactive "sPay to: ")
 233   (unless (hashcash-already-paid-p arg)
 234     (let ((pay (hashcash-generate-payment (hashcash-payment-to arg)
 235                                           (hashcash-payment-required arg))))
 236       (when pay
 237         (insert-before-markers "X-Hashcash: " pay "\n")))))
 238
 239 ;;;###autoload
 240 (defun hashcash-insert-payment-async (arg)
 241   "Insert X-Payment and X-Hashcash headers with a payment for ARG
 242 Only start calculation.  Results are inserted when ready."
 243   (interactive "sPay to: ")
 244   (unless (hashcash-already-paid-p arg)
 245     (hashcash-generate-payment-async
 246      (hashcash-payment-to arg)
 247      (hashcash-payment-required arg)
 248      `(lambda (process payment)
 249         (hashcash-insert-payment-async-2 ,(current-buffer) process payment)))))
 250
 251 (defun hashcash-insert-payment-async-2 (buffer process pay)
 252   (when (buffer-live-p buffer)
 253     (with-current-buffer buffer
 254       (save-excursion
 255         (save-restriction
 256           (setq hashcash-process-alist (delq
 257                                         (assq process hashcash-process-alist)
 258                                         hashcash-process-alist))
 259           (message-goto-eoh)
 260           (when pay
 261             (insert-before-markers "X-Hashcash: " pay)))))))
 262
 263 (defun hashcash-cancel-async (&optional buffer)
 264   "Delete any hashcash processes associated with BUFFER.
 265 BUFFER defaults to the current buffer."
 266   (interactive)
 267   (unless buffer (setq buffer (current-buffer)))
 268   (let (entry)
 269     (while (setq entry (rassq buffer hashcash-process-alist))
 270       (delete-process (car entry))
 271       (setq hashcash-process-alist
 272             (delq entry hashcash-process-alist)))))
 273
 274 (defun hashcash-wait-async (&optional buffer)
 275   "Wait for asynchronous hashcash processes in BUFFER to finish.
 276 BUFFER defaults to the current buffer."
 277   (interactive)
 278   (unless buffer (setq buffer (current-buffer)))
 279   (let (entry)
 280     (while (setq entry (rassq buffer hashcash-process-alist))
 281       (accept-process-output (car entry)))))
 282
 283 (defun hashcash-processes-running-p (buffer)
 284   "Return non-nil if hashcash processes in BUFFER are still running."
 285   (rassq buffer hashcash-process-alist))
 286
 287 (defun hashcash-wait-or-cancel ()
 288   "Ask user whether to wait for hashcash processes to finish."
 289   (interactive)
 290   (when (hashcash-processes-running-p (current-buffer))
 291     (if (y-or-n-p
 292           "Hashcash process(es) still running; wait for them to finish? ")
 293         (hashcash-wait-async)
 294       (hashcash-cancel-async))))
 295
 296 ;;;###autoload
 297 (defun hashcash-verify-payment (token &optional resource amount)
 298   "Verify a hashcash payment"
 299   (let* ((split (split-string token ":"))
 300          (key (if (< (hashcash-version token) 1.2)
 301                   (nth 1 split)
 302                   (case (string-to-number (nth 0 split))
 303                     (0 (nth 2 split))
 304                     (1 (nth 3 split))))))
 305     (cond ((null resource)
 306            (let ((elt (assoc key hashcash-accept-resources)))
 307              (and elt (hashcash-check-payment token (car elt)
 308                         (or (cadr elt) hashcash-default-accept-payment)))))
 309           ((equal token key)
 310            (hashcash-check-payment token resource
 311                                 (or amount hashcash-default-accept-payment)))
 312           (t nil))))
 313
 314 ;;;###autoload
 315 (defun mail-add-payment (&optional arg async)
 316   "Add X-Payment: and X-Hashcash: headers with a hashcash payment
 317 for each recipient address.  Prefix arg sets default payment temporarily.
 318 Set ASYNC to t to start asynchronous calculation.  (See
 319 `mail-add-payment-async')."
 320   (interactive "P")
 321   (let ((hashcash-default-payment (if arg (prefix-numeric-value arg)
 322                                     hashcash-default-payment))
 323         (addrlist nil))
 324     (save-excursion
 325       (save-restriction
 326         (message-narrow-to-headers)
 327         (let ((to (hashcash-strip-quoted-names (mail-fetch-field "To" nil t)))
 328               (cc (hashcash-strip-quoted-names (mail-fetch-field "Cc" nil t)))
 329               (ng (hashcash-strip-quoted-names (mail-fetch-field "Newsgroups"
 330                                                                  nil t))))
 331           (when to
 332             (setq addrlist (split-string to ",[ \t\n]*")))
 333           (when cc
 334             (setq addrlist (nconc addrlist (split-string cc ",[ \t\n]*"))))
 335           (when (and hashcash-in-news ng)
 336             (setq addrlist (nconc addrlist (split-string ng ",[ \t\n]*")))))
 337         (when addrlist
 338           (mapc (if async
 339                     #'hashcash-insert-payment-async
 340                   #'hashcash-insert-payment)
 341                 addrlist)))))
 342   t)
 343
 344 ;;;###autoload
 345 (defun mail-add-payment-async (&optional arg)
 346   "Add X-Payment: and X-Hashcash: headers with a hashcash payment
 347 for each recipient address.  Prefix arg sets default payment temporarily.
 348 Calculation is asynchronous."
 349   (interactive "P")
 350   (mail-add-payment arg t))
 351
 352 ;;;###autoload
 353 (defun mail-check-payment (&optional arg)
 354   "Look for a valid X-Payment: or X-Hashcash: header.
 355 Prefix arg sets default accept amount temporarily."
 356   (interactive "P")
 357   (let ((hashcash-default-accept-payment (if arg (prefix-numeric-value arg)
 358                                            hashcash-default-accept-payment))
 359         (version (hashcash-version (hashcash-generate-payment "x" 1))))
 360     (save-excursion
 361       (goto-char (point-min))
 362       (search-forward "\n\n")
 363       (beginning-of-line)
 364       (let ((end (point))
 365             (ok nil))
 366         (goto-char (point-min))
 367         (while (and (not ok) (search-forward "X-Payment: hashcash " end t))
 368           (let ((value (split-string (hashcash-token-substring) " ")))
 369             (when (equal (car value) (number-to-string version))
 370               (setq ok (hashcash-verify-payment (cadr value))))))
 371         (goto-char (point-min))
 372         (while (and (not ok) (search-forward "X-Hashcash: " end t))
 373           (setq ok (hashcash-verify-payment (hashcash-token-substring))))
 374         (when ok
 375           (message "Payment valid"))
 376         ok))))
 377
 378 (provide 'hashcash)
 379
 380 ;; arch-tag: 0e7fe983-a124-4392-9788-0dbcbd2c4d62