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1 | ;;; hashcash.el --- Add hashcash payments to email |
2 | ||
3 | ;; Copyright (C) 2003, 2004, 2005, 2007 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, or (at your option) | |
14 | ;; 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; see the file COPYING. If not, write to the | |
23 | ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, | |
24 | ;; Boston, MA 02110-1301, USA. | |
25 | ||
26 | ;;; Commentary: | |
27 | ||
28 | ;; The hashcash binary is at http://www.hashcash.org/. | |
29 | ;; | |
30 | ;; Call mail-add-payment to add a hashcash payment to a mail message | |
31 | ;; in the current buffer. | |
32 | ;; | |
33 | ;; Call mail-add-payment-async after writing the addresses but before | |
34 | ;; writing the mail to start calculating the hashcash payment | |
35 | ;; asynchronously. | |
36 | ;; | |
37 | ;; The easiest way to do this automatically for all outgoing mail | |
38 | ;; is to set `message-generate-hashcash' to t. If you want more | |
39 | ;; control, try the following hooks. | |
40 | ;; | |
41 | ;; To automatically add payments to all outgoing mail when sending: | |
42 | ;; (add-hook 'message-send-hook 'mail-add-payment) | |
43 | ;; | |
44 | ;; To start calculations automatically when addresses are prefilled: | |
45 | ;; (add-hook 'message-setup-hook 'mail-add-payment-async) | |
46 | ;; | |
47 | ;; To check whether calculations are done before sending: | |
48 | ;; (add-hook 'message-send-hook 'hashcash-wait-or-cancel) | |
49 | ||
50 | ;;; Code: | |
51 | ||
52 | (defgroup hashcash nil | |
53 | "Hashcash configuration." | |
54 | :group 'mail) | |
55 | ||
56 | (defcustom hashcash-default-payment 20 | |
57 | "*The default number of bits to pay to unknown users. | |
58 | If this is zero, no payment header will be generated. | |
59 | See `hashcash-payment-alist'." | |
60 | :type 'integer | |
61 | :group 'hashcash) | |
62 | ||
63 | (defcustom hashcash-payment-alist '() | |
64 | "*An association list mapping email addresses to payment amounts. | |
65 | Elements may consist of (ADDR AMOUNT) or (ADDR STRING AMOUNT), where | |
66 | ADDR is the email address of the intended recipient and AMOUNT is | |
67 | the value of hashcash payment to be made to that user. STRING, if | |
68 | present, is the string to be hashed; if not present ADDR will be used." | |
69 | :type '(repeat (choice (list :tag "Normal" | |
70 | (string :name "Address") | |
71 | (integer :name "Amount")) | |
72 | (list :tag "Replace hash input" | |
73 | (string :name "Address") | |
74 | (string :name "Hash input") | |
75 | (integer :name "Amount")))) | |
76 | :group 'hashcash) | |
77 | ||
78 | (defcustom hashcash-default-accept-payment 20 | |
79 | "*The default minimum number of bits to accept on incoming payments." | |
80 | :type 'integer | |
81 | :group 'hashcash) | |
82 | ||
83 | (defcustom hashcash-accept-resources `((,user-mail-address nil)) | |
84 | "*An association list mapping hashcash resources to payment amounts. | |
85 | Resources named here are to be accepted in incoming payments. If the | |
86 | corresponding AMOUNT is NIL, the value of `hashcash-default-accept-payment' | |
87 | is used instead." | |
88 | :group 'hashcash) | |
89 | ||
90 | (defcustom hashcash-path (executable-find "hashcash") | |
91 | "*The path to the hashcash binary." | |
92 | :group 'hashcash) | |
93 | ||
94 | (defcustom hashcash-extra-generate-parameters nil | |
95 | "*A list of parameter strings passed to `hashcash-path' when minting. | |
96 | For example, you may want to set this to '(\"-Z2\") to reduce header length." | |
97 | :type '(repeat string) | |
98 | :group 'hashcash) | |
99 | ||
100 | (defcustom hashcash-double-spend-database "hashcash.db" | |
101 | "*The path to the double-spending database." | |
102 | :group 'hashcash) | |
103 | ||
104 | (defcustom hashcash-in-news nil | |
105 | "*Specifies whether or not hashcash payments should be made to newsgroups." | |
106 | :type 'boolean | |
107 | :group 'hashcash) | |
108 | ||
109 | (defvar hashcash-process-alist nil | |
110 | "Alist of asynchronous hashcash processes and buffers.") | |
111 | ||
112 | (require 'mail-utils) | |
113 | ||
114 | (eval-and-compile | |
115 | (if (fboundp 'point-at-bol) | |
116 | (defalias 'hashcash-point-at-bol 'point-at-bol) | |
117 | (defalias 'hashcash-point-at-bol 'line-beginning-position)) | |
118 | ||
119 | (if (fboundp 'point-at-eol) | |
120 | (defalias 'hashcash-point-at-eol 'point-at-eol) | |
121 | (defalias 'hashcash-point-at-eol 'line-end-position))) | |
122 | ||
123 | (defun hashcash-strip-quoted-names (addr) | |
124 | (setq addr (mail-strip-quoted-names addr)) | |
125 | (if (and addr (string-match "\\`\\([^+@]+\\)\\+[^@]*\\(@.+\\)" addr)) | |
126 | (concat (match-string 1 addr) (match-string 2 addr)) | |
127 | addr)) | |
128 | ||
129 | (defun hashcash-token-substring () | |
130 | (save-excursion | |
131 | (let ((token "")) | |
132 | (loop | |
133 | (setq token | |
134 | (concat token (buffer-substring (point) (hashcash-point-at-eol)))) | |
135 | (goto-char (hashcash-point-at-eol)) | |
136 | (forward-char 1) | |
137 | (unless (looking-at "[ \t]") (return token)) | |
138 | (while (looking-at "[ \t]") (forward-char 1)))))) | |
139 | ||
140 | (defun hashcash-payment-required (addr) | |
141 | "Return the hashcash payment value required for the given address." | |
142 | (let ((val (assoc addr hashcash-payment-alist))) | |
143 | (or (nth 2 val) (nth 1 val) hashcash-default-payment))) | |
144 | ||
145 | (defun hashcash-payment-to (addr) | |
146 | "Return the string with which hashcash payments should collide." | |
147 | (let ((val (assoc addr hashcash-payment-alist))) | |
148 | (or (nth 1 val) (nth 0 val) addr))) | |
149 | ||
150 | (defun hashcash-generate-payment (str val) | |
151 | "Generate a hashcash payment by finding a VAL-bit collison on STR." | |
152 | (if (and (> val 0) | |
153 | hashcash-path) | |
154 | (save-excursion | |
155 | (set-buffer (get-buffer-create " *hashcash*")) | |
156 | (erase-buffer) | |
157 | (apply 'call-process hashcash-path nil t nil | |
158 | "-m" "-q" "-b" (number-to-string val) str | |
159 | hashcash-extra-generate-parameters) | |
160 | (goto-char (point-min)) | |
161 | (hashcash-token-substring)) | |
162 | (error "No `hashcash' binary found"))) | |
163 | ||
164 | (defun hashcash-generate-payment-async (str val callback) | |
165 | "Generate a hashcash payment by finding a VAL-bit collison on STR. | |
166 | Return immediately. Call CALLBACK with process and result when ready." | |
167 | (if (and (> val 0) | |
168 | hashcash-path) | |
169 | (let ((process (apply 'start-process "hashcash" nil | |
170 | hashcash-path "-m" "-q" | |
171 | "-b" (number-to-string val) str | |
172 | hashcash-extra-generate-parameters))) | |
173 | (setq hashcash-process-alist (cons | |
174 | (cons process (current-buffer)) | |
175 | hashcash-process-alist)) | |
176 | (set-process-filter process `(lambda (process output) | |
177 | (funcall ,callback process output)))) | |
178 | (funcall callback nil nil))) | |
179 | ||
180 | (defun hashcash-check-payment (token str val) | |
181 | "Check the validity of a hashcash payment." | |
182 | (if hashcash-path | |
183 | (zerop (call-process hashcash-path nil nil nil "-c" | |
184 | "-d" "-f" hashcash-double-spend-database | |
185 | "-b" (number-to-string val) | |
186 | "-r" str | |
187 | token)) | |
188 | (progn | |
189 | (message "No hashcash binary found") | |
190 | (sleep-for 1) | |
191 | nil))) | |
192 | ||
193 | (defun hashcash-version (token) | |
194 | "Find the format version of a hashcash token." | |
195 | ;; Version 1.2 looks like n:yymmdd:rrrrr:xxxxxxxxxxxxxxxx | |
196 | ;; This carries its own version number embedded in the token, | |
197 | ;; so no further format number changes should be necessary | |
198 | ;; in the X-Payment header. | |
199 | ;; | |
200 | ;; Version 1.1 looks like yymmdd:rrrrr:xxxxxxxxxxxxxxxx | |
201 | ;; You need to upgrade your hashcash binary. | |
202 | ;; | |
203 | ;; Version 1.0 looked like nnnnnrrrrrxxxxxxxxxxxxxxxx | |
204 | ;; This is no longer supported. | |
205 | (cond ((equal (aref token 1) ?:) 1.2) | |
206 | ((equal (aref token 6) ?:) 1.1) | |
207 | (t (error "Unknown hashcash format version")))) | |
208 | ||
209 | (defun hashcash-already-paid-p (recipient) | |
210 | "Check for hashcash token to RECIPIENT in current buffer." | |
211 | (save-excursion | |
212 | (save-restriction | |
213 | (message-narrow-to-headers-or-head) | |
214 | (let ((token (message-fetch-field "x-hashcash")) | |
215 | (case-fold-search t)) | |
216 | (and (stringp token) | |
217 | (string-match (regexp-quote recipient) token)))))) | |
218 | ||
219 | ;;;###autoload | |
220 | (defun hashcash-insert-payment (arg) | |
221 | "Insert X-Payment and X-Hashcash headers with a payment for ARG" | |
222 | (interactive "sPay to: ") | |
223 | (unless (hashcash-already-paid-p arg) | |
224 | (let ((pay (hashcash-generate-payment (hashcash-payment-to arg) | |
225 | (hashcash-payment-required arg)))) | |
226 | (when pay | |
227 | (insert-before-markers "X-Hashcash: " pay "\n"))))) | |
228 | ||
229 | ;;;###autoload | |
230 | (defun hashcash-insert-payment-async (arg) | |
231 | "Insert X-Payment and X-Hashcash headers with a payment for ARG | |
232 | Only start calculation. Results are inserted when ready." | |
233 | (interactive "sPay to: ") | |
234 | (unless (hashcash-already-paid-p arg) | |
235 | (hashcash-generate-payment-async | |
236 | (hashcash-payment-to arg) | |
237 | (hashcash-payment-required arg) | |
238 | `(lambda (process payment) | |
239 | (hashcash-insert-payment-async-2 ,(current-buffer) process payment))))) | |
240 | ||
241 | (defun hashcash-insert-payment-async-2 (buffer process pay) | |
242 | (when (buffer-live-p buffer) | |
243 | (with-current-buffer buffer | |
244 | (save-excursion | |
245 | (save-restriction | |
246 | (setq hashcash-process-alist (delq | |
247 | (assq process hashcash-process-alist) | |
248 | hashcash-process-alist)) | |
249 | (message-goto-eoh) | |
250 | (when pay | |
251 | (insert-before-markers "X-Hashcash: " pay))))))) | |
252 | ||
253 | (defun hashcash-cancel-async (&optional buffer) | |
254 | "Delete any hashcash processes associated with BUFFER. | |
255 | BUFFER defaults to the current buffer." | |
256 | (interactive) | |
257 | (unless buffer (setq buffer (current-buffer))) | |
258 | (let (entry) | |
259 | (while (setq entry (rassq buffer hashcash-process-alist)) | |
260 | (delete-process (car entry)) | |
261 | (setq hashcash-process-alist | |
262 | (delq entry hashcash-process-alist))))) | |
263 | ||
264 | (defun hashcash-wait-async (&optional buffer) | |
265 | "Wait for asynchronous hashcash processes in BUFFER to finish. | |
266 | BUFFER defaults to the current buffer." | |
267 | (interactive) | |
268 | (unless buffer (setq buffer (current-buffer))) | |
269 | (let (entry) | |
270 | (while (setq entry (rassq buffer hashcash-process-alist)) | |
271 | (accept-process-output (car entry))))) | |
272 | ||
273 | (defun hashcash-processes-running-p (buffer) | |
274 | "Return non-nil if hashcash processes in BUFFER are still running." | |
275 | (rassq buffer hashcash-process-alist)) | |
276 | ||
277 | (defun hashcash-wait-or-cancel () | |
278 | "Ask user whether to wait for hashcash processes to finish." | |
279 | (interactive) | |
280 | (when (hashcash-processes-running-p (current-buffer)) | |
281 | (if (y-or-n-p | |
282 | "Hashcash process(es) still running; wait for them to finish? ") | |
283 | (hashcash-wait-async) | |
284 | (hashcash-cancel-async)))) | |
285 | ||
286 | ;;;###autoload | |
287 | (defun hashcash-verify-payment (token &optional resource amount) | |
288 | "Verify a hashcash payment" | |
289 | (let* ((split (split-string token ":")) | |
290 | (key (if (< (hashcash-version token) 1.2) | |
291 | (nth 1 split) | |
292 | (case (string-to-number (nth 0 split)) | |
293 | (0 (nth 2 split)) | |
294 | (1 (nth 3 split)))))) | |
295 | (cond ((null resource) | |
296 | (let ((elt (assoc key hashcash-accept-resources))) | |
297 | (and elt (hashcash-check-payment token (car elt) | |
298 | (or (cadr elt) hashcash-default-accept-payment))))) | |
299 | ((equal token key) | |
300 | (hashcash-check-payment token resource | |
301 | (or amount hashcash-default-accept-payment))) | |
302 | (t nil)))) | |
303 | ||
304 | ;;;###autoload | |
305 | (defun mail-add-payment (&optional arg async) | |
306 | "Add X-Payment: and X-Hashcash: headers with a hashcash payment | |
307 | for each recipient address. Prefix arg sets default payment temporarily. | |
308 | Set ASYNC to t to start asynchronous calculation. (See | |
309 | `mail-add-payment-async')." | |
310 | (interactive "P") | |
311 | (let ((hashcash-default-payment (if arg (prefix-numeric-value arg) | |
312 | hashcash-default-payment)) | |
313 | (addrlist nil)) | |
314 | (save-excursion | |
315 | (save-restriction | |
316 | (message-narrow-to-headers) | |
317 | (let ((to (hashcash-strip-quoted-names (mail-fetch-field "To" nil t))) | |
318 | (cc (hashcash-strip-quoted-names (mail-fetch-field "Cc" nil t))) | |
319 | (ng (hashcash-strip-quoted-names (mail-fetch-field "Newsgroups" | |
320 | nil t)))) | |
321 | (when to | |
322 | (setq addrlist (split-string to ",[ \t\n]*"))) | |
323 | (when cc | |
324 | (setq addrlist (nconc addrlist (split-string cc ",[ \t\n]*")))) | |
325 | (when (and hashcash-in-news ng) | |
326 | (setq addrlist (nconc addrlist (split-string ng ",[ \t\n]*"))))) | |
327 | (when addrlist | |
328 | (mapc (if async | |
329 | #'hashcash-insert-payment-async | |
330 | #'hashcash-insert-payment) | |
331 | addrlist))))) | |
332 | t) | |
333 | ||
334 | ;;;###autoload | |
335 | (defun mail-add-payment-async (&optional arg) | |
336 | "Add X-Payment: and X-Hashcash: headers with a hashcash payment | |
337 | for each recipient address. Prefix arg sets default payment temporarily. | |
338 | Calculation is asynchronous." | |
339 | (interactive "P") | |
340 | (mail-add-payment arg t)) | |
341 | ||
342 | ;;;###autoload | |
343 | (defun mail-check-payment (&optional arg) | |
344 | "Look for a valid X-Payment: or X-Hashcash: header. | |
345 | Prefix arg sets default accept amount temporarily." | |
346 | (interactive "P") | |
347 | (let ((hashcash-default-accept-payment (if arg (prefix-numeric-value arg) | |
348 | hashcash-default-accept-payment)) | |
349 | (version (hashcash-version (hashcash-generate-payment "x" 1)))) | |
350 | (save-excursion | |
351 | (goto-char (point-min)) | |
352 | (search-forward "\n\n") | |
353 | (beginning-of-line) | |
354 | (let ((end (point)) | |
355 | (ok nil)) | |
356 | (goto-char (point-min)) | |
357 | (while (and (not ok) (search-forward "X-Payment: hashcash " end t)) | |
358 | (let ((value (split-string (hashcash-token-substring) " "))) | |
359 | (when (equal (car value) (number-to-string version)) | |
360 | (setq ok (hashcash-verify-payment (cadr value)))))) | |
361 | (goto-char (point-min)) | |
362 | (while (and (not ok) (search-forward "X-Hashcash: " end t)) | |
363 | (setq ok (hashcash-verify-payment (hashcash-token-substring)))) | |
364 | (when ok | |
365 | (message "Payment valid")) | |
366 | ok)))) | |
367 | ||
368 | (provide 'hashcash) | |
369 | ||
370 | ;;; arch-tag: 0e7fe983-a124-4392-9788-0dbcbd2c4d62 |