--- /dev/null
+;;; hashcash.el --- Add hashcash payments to email
+
+;; Copyright (C) 2003-2005, 2007-2016 Free Software Foundation, Inc.
+
+;; Written by: Paul Foley <mycroft@actrix.gen.nz> (1997-2002)
+;; Maintainer: Paul Foley <mycroft@actrix.gen.nz>
+;; Keywords: mail, hashcash
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; The hashcash binary is at http://www.hashcash.org/.
+;;
+;; Call mail-add-payment to add a hashcash payment to a mail message
+;; in the current buffer.
+;;
+;; Call mail-add-payment-async after writing the addresses but before
+;; writing the mail to start calculating the hashcash payment
+;; asynchronously.
+;;
+;; The easiest way to do this automatically for all outgoing mail
+;; is to set `message-generate-hashcash' to t. If you want more
+;; control, try the following hooks.
+;;
+;; To automatically add payments to all outgoing mail when sending:
+;; (add-hook 'message-send-hook 'mail-add-payment)
+;;
+;; To start calculations automatically when addresses are prefilled:
+;; (add-hook 'message-setup-hook 'mail-add-payment-async)
+;;
+;; To check whether calculations are done before sending:
+;; (add-hook 'message-send-hook 'hashcash-wait-or-cancel)
+
+;;; Code:
+
+(eval-when-compile (require 'cl)) ; for case
+
+(defgroup hashcash nil
+ "Hashcash configuration."
+ :group 'mail)
+
+(defcustom hashcash-default-payment 20
+ "The default number of bits to pay to unknown users.
+If this is zero, no payment header will be generated.
+See `hashcash-payment-alist'."
+ :type 'integer
+ :group 'hashcash)
+
+(defcustom hashcash-payment-alist '()
+ "An association list mapping email addresses to payment amounts.
+Elements may consist of (ADDR AMOUNT) or (ADDR STRING AMOUNT), where
+ADDR is the email address of the intended recipient and AMOUNT is
+the value of hashcash payment to be made to that user. STRING, if
+present, is the string to be hashed; if not present ADDR will be used."
+ :type '(repeat (choice (list :tag "Normal"
+ (string :name "Address")
+ (integer :name "Amount"))
+ (list :tag "Replace hash input"
+ (string :name "Address")
+ (string :name "Hash input")
+ (integer :name "Amount"))))
+ :group 'hashcash)
+
+(defcustom hashcash-default-accept-payment 20
+ "The default minimum number of bits to accept on incoming payments."
+ :type 'integer
+ :group 'hashcash)
+
+(defcustom hashcash-accept-resources `((,user-mail-address nil))
+ "An association list mapping hashcash resources to payment amounts.
+Resources named here are to be accepted in incoming payments. If the
+corresponding AMOUNT is NIL, the value of `hashcash-default-accept-payment'
+is used instead."
+ :type 'alist
+ :group 'hashcash)
+
+(define-obsolete-variable-alias 'hashcash-path 'hashcash-program "24.4")
+(defcustom hashcash-program "hashcash"
+ "The name of the hashcash executable.
+If this is not in your PATH, specify an absolute file name."
+ :type '(choice (const nil) file)
+ :group 'hashcash)
+
+(defcustom hashcash-extra-generate-parameters nil
+ "A list of parameter strings passed to `hashcash-program' when minting.
+For example, you may want to set this to (\"-Z2\") to reduce header length."
+ :type '(repeat string)
+ :group 'hashcash)
+
+(defcustom hashcash-double-spend-database "hashcash.db"
+ "The name of the double-spending database file."
+ :type 'file
+ :group 'hashcash)
+
+(defcustom hashcash-in-news nil
+ "Specifies whether or not hashcash payments should be made to newsgroups."
+ :type 'boolean
+ :group 'hashcash)
+
+(defvar hashcash-process-alist nil
+ "Alist of asynchronous hashcash processes and buffers.")
+
+(require 'mail-utils)
+
+(eval-and-compile
+ (if (fboundp 'point-at-bol)
+ (defalias 'hashcash-point-at-bol 'point-at-bol)
+ (defalias 'hashcash-point-at-bol 'line-beginning-position))
+
+ (if (fboundp 'point-at-eol)
+ (defalias 'hashcash-point-at-eol 'point-at-eol)
+ (defalias 'hashcash-point-at-eol 'line-end-position)))
+
+(defun hashcash-strip-quoted-names (addr)
+ (setq addr (mail-strip-quoted-names addr))
+ (if (and addr (string-match "\\`\\([^+@]+\\)\\+[^@]*\\(@.+\\)" addr))
+ (concat (match-string 1 addr) (match-string 2 addr))
+ addr))
+
+(declare-function message-narrow-to-headers-or-head "message" ())
+(declare-function message-fetch-field "message" (header &optional not-all))
+(declare-function message-goto-eoh "message" ())
+(declare-function message-narrow-to-headers "message" ())
+
+(defun hashcash-token-substring ()
+ (save-excursion
+ (let ((token ""))
+ (loop
+ (setq token
+ (concat token (buffer-substring (point) (hashcash-point-at-eol))))
+ (goto-char (hashcash-point-at-eol))
+ (forward-char 1)
+ (unless (looking-at "[ \t]") (return token))
+ (while (looking-at "[ \t]") (forward-char 1))))))
+
+(defun hashcash-payment-required (addr)
+ "Return the hashcash payment value required for the given address."
+ (let ((val (assoc addr hashcash-payment-alist)))
+ (or (nth 2 val) (nth 1 val) hashcash-default-payment)))
+
+(defun hashcash-payment-to (addr)
+ "Return the string with which hashcash payments should collide."
+ (let ((val (assoc addr hashcash-payment-alist)))
+ (or (nth 1 val) (nth 0 val) addr)))
+
+(defun hashcash-generate-payment (str val)
+ "Generate a hashcash payment by finding a VAL-bit collison on STR."
+ (if (and (> val 0)
+ hashcash-program)
+ (with-current-buffer (get-buffer-create " *hashcash*")
+ (erase-buffer)
+ (apply 'call-process hashcash-program nil t nil
+ "-m" "-q" "-b" (number-to-string val) str
+ hashcash-extra-generate-parameters)
+ (goto-char (point-min))
+ (hashcash-token-substring))
+ (error "No `hashcash' binary found")))
+
+(defun hashcash-generate-payment-async (str val callback)
+ "Generate a hashcash payment by finding a VAL-bit collison on STR.
+Return immediately. Call CALLBACK with process and result when ready."
+ (if (and (> val 0)
+ hashcash-program)
+ (let ((process (apply 'start-process "hashcash" nil
+ hashcash-program "-m" "-q"
+ "-b" (number-to-string val) str
+ hashcash-extra-generate-parameters)))
+ (setq hashcash-process-alist (cons
+ (cons process (current-buffer))
+ hashcash-process-alist))
+ (set-process-filter process `(lambda (process output)
+ (funcall ,callback process output))))
+ (funcall callback nil nil)))
+
+(defun hashcash-check-payment (token str val)
+ "Check the validity of a hashcash payment."
+ (if hashcash-program
+ (zerop (call-process hashcash-program nil nil nil "-c"
+ "-d" "-f" hashcash-double-spend-database
+ "-b" (number-to-string val)
+ "-r" str
+ token))
+ (progn
+ (message "No hashcash binary found")
+ (sleep-for 1)
+ nil)))
+
+(defun hashcash-version (token)
+ "Find the format version of a hashcash token."
+ ;; Version 1.2 looks like n:yymmdd:rrrrr:xxxxxxxxxxxxxxxx
+ ;; This carries its own version number embedded in the token,
+ ;; so no further format number changes should be necessary
+ ;; in the X-Payment header.
+ ;;
+ ;; Version 1.1 looks like yymmdd:rrrrr:xxxxxxxxxxxxxxxx
+ ;; You need to upgrade your hashcash binary.
+ ;;
+ ;; Version 1.0 looked like nnnnnrrrrrxxxxxxxxxxxxxxxx
+ ;; This is no longer supported.
+ (cond ((equal (aref token 1) ?:) 1.2)
+ ((equal (aref token 6) ?:) 1.1)
+ (t (error "Unknown hashcash format version"))))
+
+(defun hashcash-already-paid-p (recipient)
+ "Check for hashcash token to RECIPIENT in current buffer."
+ (save-excursion
+ (save-restriction
+ (message-narrow-to-headers-or-head)
+ (let ((token (message-fetch-field "x-hashcash"))
+ (case-fold-search t))
+ (and (stringp token)
+ (string-match (regexp-quote recipient) token))))))
+
+;;;###autoload
+(defun hashcash-insert-payment (arg)
+ "Insert X-Payment and X-Hashcash headers with a payment for ARG"
+ (interactive "sPay to: ")
+ (unless (hashcash-already-paid-p arg)
+ (let ((pay (hashcash-generate-payment (hashcash-payment-to arg)
+ (hashcash-payment-required arg))))
+ (when pay
+ (insert-before-markers "X-Hashcash: " pay "\n")))))
+
+;;;###autoload
+(defun hashcash-insert-payment-async (arg)
+ "Insert X-Payment and X-Hashcash headers with a payment for ARG
+Only start calculation. Results are inserted when ready."
+ (interactive "sPay to: ")
+ (unless (hashcash-already-paid-p arg)
+ (hashcash-generate-payment-async
+ (hashcash-payment-to arg)
+ (hashcash-payment-required arg)
+ `(lambda (process payment)
+ (hashcash-insert-payment-async-2 ,(current-buffer) process payment)))))
+
+(defun hashcash-insert-payment-async-2 (buffer process pay)
+ (when (buffer-live-p buffer)
+ (with-current-buffer buffer
+ (save-excursion
+ (save-restriction
+ (setq hashcash-process-alist (delq
+ (assq process hashcash-process-alist)
+ hashcash-process-alist))
+ (message-goto-eoh)
+ (when pay
+ (insert-before-markers "X-Hashcash: " pay)))))))
+
+(defun hashcash-cancel-async (&optional buffer)
+ "Delete any hashcash processes associated with BUFFER.
+BUFFER defaults to the current buffer."
+ (interactive)
+ (unless buffer (setq buffer (current-buffer)))
+ (let (entry)
+ (while (setq entry (rassq buffer hashcash-process-alist))
+ (delete-process (car entry))
+ (setq hashcash-process-alist
+ (delq entry hashcash-process-alist)))))
+
+(defun hashcash-wait-async (&optional buffer)
+ "Wait for asynchronous hashcash processes in BUFFER to finish.
+BUFFER defaults to the current buffer."
+ (interactive)
+ (unless buffer (setq buffer (current-buffer)))
+ (let (entry)
+ (while (setq entry (rassq buffer hashcash-process-alist))
+ (accept-process-output (car entry) 1))))
+
+(defun hashcash-processes-running-p (buffer)
+ "Return non-nil if hashcash processes in BUFFER are still running."
+ (rassq buffer hashcash-process-alist))
+
+(defun hashcash-wait-or-cancel ()
+ "Ask user whether to wait for hashcash processes to finish."
+ (interactive)
+ (when (hashcash-processes-running-p (current-buffer))
+ (if (y-or-n-p
+ "Hashcash process(es) still running; wait for them to finish? ")
+ (hashcash-wait-async)
+ (hashcash-cancel-async))))
+
+;;;###autoload
+(defun hashcash-verify-payment (token &optional resource amount)
+ "Verify a hashcash payment"
+ (let* ((split (split-string token ":"))
+ (key (if (< (hashcash-version token) 1.2)
+ (nth 1 split)
+ (case (string-to-number (nth 0 split))
+ (0 (nth 2 split))
+ (1 (nth 3 split))))))
+ (cond ((null resource)
+ (let ((elt (assoc key hashcash-accept-resources)))
+ (and elt (hashcash-check-payment token (car elt)
+ (or (cadr elt) hashcash-default-accept-payment)))))
+ ((equal token key)
+ (hashcash-check-payment token resource
+ (or amount hashcash-default-accept-payment)))
+ (t nil))))
+
+;;;###autoload
+(defun mail-add-payment (&optional arg async)
+ "Add X-Payment: and X-Hashcash: headers with a hashcash payment
+for each recipient address. Prefix arg sets default payment temporarily.
+Set ASYNC to t to start asynchronous calculation. (See
+`mail-add-payment-async')."
+ (interactive "P")
+ (let ((hashcash-default-payment (if arg (prefix-numeric-value arg)
+ hashcash-default-payment))
+ (addrlist nil))
+ (save-excursion
+ (save-restriction
+ (message-narrow-to-headers)
+ (let ((to (hashcash-strip-quoted-names (mail-fetch-field "To" nil t)))
+ (cc (hashcash-strip-quoted-names (mail-fetch-field "Cc" nil t)))
+ (ng (hashcash-strip-quoted-names (mail-fetch-field "Newsgroups"
+ nil t))))
+ (when to
+ (setq addrlist (split-string to ",[ \t\n]*")))
+ (when cc
+ (setq addrlist (nconc addrlist (split-string cc ",[ \t\n]*"))))
+ (when (and hashcash-in-news ng)
+ (setq addrlist (nconc addrlist (split-string ng ",[ \t\n]*")))))
+ (when addrlist
+ (mapc (if async
+ #'hashcash-insert-payment-async
+ #'hashcash-insert-payment)
+ addrlist)))))
+ t)
+
+;;;###autoload
+(defun mail-add-payment-async (&optional arg)
+ "Add X-Payment: and X-Hashcash: headers with a hashcash payment
+for each recipient address. Prefix arg sets default payment temporarily.
+Calculation is asynchronous."
+ (interactive "P")
+ (mail-add-payment arg t))
+
+;;;###autoload
+(defun mail-check-payment (&optional arg)
+ "Look for a valid X-Payment: or X-Hashcash: header.
+Prefix arg sets default accept amount temporarily."
+ (interactive "P")
+ (let ((hashcash-default-accept-payment (if arg (prefix-numeric-value arg)
+ hashcash-default-accept-payment))
+ (version (hashcash-version (hashcash-generate-payment "x" 1))))
+ (save-excursion
+ (goto-char (point-min))
+ (search-forward "\n\n")
+ (beginning-of-line)
+ (let ((end (point))
+ (ok nil))
+ (goto-char (point-min))
+ (while (and (not ok) (search-forward "X-Payment: hashcash " end t))
+ (let ((value (split-string (hashcash-token-substring) " ")))
+ (when (equal (car value) (number-to-string version))
+ (setq ok (hashcash-verify-payment (cadr value))))))
+ (goto-char (point-min))
+ (while (and (not ok) (search-forward "X-Hashcash: " end t))
+ (setq ok (hashcash-verify-payment (hashcash-token-substring))))
+ (when ok
+ (message "Payment valid"))
+ ok))))
+
+(provide 'hashcash)
+
+;;; hashcash.el ends here
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