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374 lines
13 KiB
EmacsLisp
374 lines
13 KiB
EmacsLisp
;;; hashcash.el --- Add hashcash payments to email -*- lexical-binding:t -*-
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;; Copyright (C) 2003-2005, 2007-2021 Free Software Foundation, Inc.
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;; Written by: Paul Foley <mycroft@actrix.gen.nz> (1997-2002)
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: mail, hashcash
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; The hashcash binary is at http://www.hashcash.org/.
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;;
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;; Call mail-add-payment to add a hashcash payment to a mail message
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;; in the current buffer.
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;;
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;; Call mail-add-payment-async after writing the addresses but before
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;; writing the mail to start calculating the hashcash payment
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;; asynchronously.
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;;
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;; The easiest way to do this automatically for all outgoing mail
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;; is to set `message-generate-hashcash' to t. If you want more
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;; control, try the following hooks.
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;;
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;; To automatically add payments to all outgoing mail when sending:
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;; (add-hook 'message-send-hook 'mail-add-payment)
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;;
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;; To start calculations automatically when addresses are prefilled:
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;; (add-hook 'message-setup-hook 'mail-add-payment-async)
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;;
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;; To check whether calculations are done before sending:
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;; (add-hook 'message-send-hook 'hashcash-wait-or-cancel)
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;;; Code:
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(eval-when-compile (require 'cl-lib))
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(defgroup hashcash nil
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"Hashcash configuration."
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:group 'mail)
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(defcustom hashcash-default-payment 20
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"The default number of bits to pay to unknown users.
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If this is zero, no payment header will be generated.
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See `hashcash-payment-alist'."
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:type 'integer
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:group 'hashcash)
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(defcustom hashcash-payment-alist '()
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"An association list mapping email addresses to payment amounts.
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Elements may consist of (ADDR AMOUNT) or (ADDR STRING AMOUNT), where
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ADDR is the email address of the intended recipient and AMOUNT is
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the value of hashcash payment to be made to that user. STRING, if
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present, is the string to be hashed; if not present ADDR will be used."
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:type '(repeat (choice (list :tag "Normal"
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(string :name "Address")
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(integer :name "Amount"))
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(list :tag "Replace hash input"
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(string :name "Address")
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(string :name "Hash input")
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(integer :name "Amount"))))
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:group 'hashcash)
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(defcustom hashcash-default-accept-payment 20
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"The default minimum number of bits to accept on incoming payments."
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:type 'integer
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:group 'hashcash)
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(defcustom hashcash-accept-resources `((,user-mail-address nil))
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"An association list mapping hashcash resources to payment amounts.
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Resources named here are to be accepted in incoming payments. If the
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corresponding AMOUNT is NIL, the value of `hashcash-default-accept-payment'
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is used instead."
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:type 'alist
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:group 'hashcash)
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(define-obsolete-variable-alias 'hashcash-path 'hashcash-program "24.4")
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(defcustom hashcash-program "hashcash"
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"The name of the hashcash executable.
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If this is not in your PATH, specify an absolute file name."
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:type '(choice (const nil) file)
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:group 'hashcash)
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(defcustom hashcash-extra-generate-parameters nil
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"A list of parameter strings passed to `hashcash-program' when minting.
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For example, you may want to set this to (\"-Z2\") to reduce header length."
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:type '(repeat string)
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:group 'hashcash)
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(defcustom hashcash-double-spend-database "hashcash.db"
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"The name of the double-spending database file."
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:type 'file
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:group 'hashcash)
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(defcustom hashcash-in-news nil
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"Specifies whether or not hashcash payments should be made to newsgroups."
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:type 'boolean
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:group 'hashcash)
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(defvar hashcash-process-alist nil
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"Alist of asynchronous hashcash processes and buffers.")
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(require 'mail-utils)
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(defun hashcash-strip-quoted-names (addr)
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(setq addr (mail-strip-quoted-names addr))
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(if (and addr (string-match "\\`\\([^+@]+\\)\\+[^@]*\\(@.+\\)" addr))
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(concat (match-string 1 addr) (match-string 2 addr))
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addr))
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(declare-function message-narrow-to-headers-or-head "message" ())
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(declare-function message-fetch-field "message" (header &optional not-all))
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(declare-function message-goto-eoh "message" (&optional interactive))
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(declare-function message-narrow-to-headers "message" ())
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(defun hashcash-token-substring ()
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(save-excursion
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(let ((token ""))
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(cl-loop
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(setq token
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(concat token (buffer-substring (point) (line-end-position))))
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(goto-char (line-end-position))
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(forward-char 1)
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(unless (looking-at "[ \t]") (cl-return token))
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(while (looking-at "[ \t]") (forward-char 1))))))
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(defun hashcash-payment-required (addr)
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"Return the hashcash payment value required for the given address."
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(let ((val (assoc addr hashcash-payment-alist)))
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(or (nth 2 val) (nth 1 val) hashcash-default-payment)))
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(defun hashcash-payment-to (addr)
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"Return the string with which hashcash payments should collide."
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(let ((val (assoc addr hashcash-payment-alist)))
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(or (nth 1 val) (nth 0 val) addr)))
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(defun hashcash-generate-payment (str val)
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"Generate a hashcash payment by finding a VAL-bit collision on STR."
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(if (and (> val 0)
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hashcash-program)
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(with-current-buffer (get-buffer-create " *hashcash*")
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(erase-buffer)
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(apply 'call-process hashcash-program nil t nil
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"-m" "-q" "-b" (number-to-string val) str
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hashcash-extra-generate-parameters)
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(goto-char (point-min))
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(hashcash-token-substring))
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(error "No `hashcash' binary found")))
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(defun hashcash-generate-payment-async (str val callback)
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"Generate a hashcash payment by finding a VAL-bit collision on STR.
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Return immediately. Call CALLBACK with process and result when ready."
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(if (and (> val 0)
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hashcash-program)
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(let ((process (apply 'start-process "hashcash" nil
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hashcash-program "-m" "-q"
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"-b" (number-to-string val) str
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hashcash-extra-generate-parameters)))
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(setq hashcash-process-alist (cons
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(cons process (current-buffer))
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hashcash-process-alist))
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(set-process-filter process callback))
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(funcall callback nil nil)))
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(defun hashcash-check-payment (token str val)
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"Check the validity of a hashcash payment."
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(if hashcash-program
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(zerop (call-process hashcash-program nil nil nil "-c"
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"-d" "-f" hashcash-double-spend-database
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"-b" (number-to-string val)
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"-r" str
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token))
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(progn
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(message "No hashcash binary found")
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(sleep-for 1)
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nil)))
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(defun hashcash-version (token)
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"Find the format version of a hashcash token."
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;; Version 1.2 looks like n:yymmdd:rrrrr:xxxxxxxxxxxxxxxx
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;; This carries its own version number embedded in the token,
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;; so no further format number changes should be necessary
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;; in the X-Payment header.
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;;
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;; Version 1.1 looks like yymmdd:rrrrr:xxxxxxxxxxxxxxxx
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;; You need to upgrade your hashcash binary.
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;;
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;; Version 1.0 looked like nnnnnrrrrrxxxxxxxxxxxxxxxx
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;; This is no longer supported.
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(cond ((equal (aref token 1) ?:) 1.2)
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((equal (aref token 6) ?:) 1.1)
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(t (error "Unknown hashcash format version"))))
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(defun hashcash-already-paid-p (recipient)
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"Check for hashcash token to RECIPIENT in current buffer."
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(save-excursion
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(save-restriction
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(message-narrow-to-headers-or-head)
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(let ((token (message-fetch-field "x-hashcash"))
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(case-fold-search t))
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(and (stringp token)
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(string-match (regexp-quote recipient) token))))))
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;;;###autoload
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(defun hashcash-insert-payment (arg)
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"Insert X-Payment and X-Hashcash headers with a payment for ARG."
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(interactive "sPay to: ")
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(unless (hashcash-already-paid-p arg)
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(let ((pay (hashcash-generate-payment (hashcash-payment-to arg)
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(hashcash-payment-required arg))))
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(when pay
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(insert-before-markers "X-Hashcash: " pay "\n")))))
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;;;###autoload
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(defun hashcash-insert-payment-async (arg)
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"Insert X-Payment and X-Hashcash headers with a payment for ARG
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Only start calculation. Results are inserted when ready."
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(interactive "sPay to: ")
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(unless (hashcash-already-paid-p arg)
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(hashcash-generate-payment-async
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(hashcash-payment-to arg)
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(hashcash-payment-required arg)
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(let ((buf (current-buffer)))
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(lambda (process payment)
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(hashcash-insert-payment-async-2 buf process payment))))))
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(defun hashcash-insert-payment-async-2 (buffer process pay)
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(when (buffer-live-p buffer)
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(with-current-buffer buffer
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(save-excursion
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(save-restriction
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(setq hashcash-process-alist (delq
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(assq process hashcash-process-alist)
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hashcash-process-alist))
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(message-goto-eoh)
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(when pay
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(insert-before-markers "X-Hashcash: " pay)))))))
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(defun hashcash-cancel-async (&optional buffer)
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"Delete any hashcash processes associated with BUFFER.
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BUFFER defaults to the current buffer."
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(interactive)
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(unless buffer (setq buffer (current-buffer)))
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(let (entry)
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(while (setq entry (rassq buffer hashcash-process-alist))
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(delete-process (car entry))
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(setq hashcash-process-alist
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(delq entry hashcash-process-alist)))))
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(defun hashcash-wait-async (&optional buffer)
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"Wait for asynchronous hashcash processes in BUFFER to finish.
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BUFFER defaults to the current buffer."
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(interactive)
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(unless buffer (setq buffer (current-buffer)))
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(let (entry)
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(while (setq entry (rassq buffer hashcash-process-alist))
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(accept-process-output (car entry) 1))))
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(defun hashcash-processes-running-p (buffer)
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"Return non-nil if hashcash processes in BUFFER are still running."
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(rassq buffer hashcash-process-alist))
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(defun hashcash-wait-or-cancel ()
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"Ask user whether to wait for hashcash processes to finish."
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(interactive)
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(when (hashcash-processes-running-p (current-buffer))
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(if (y-or-n-p
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"Hashcash process(es) still running; wait for them to finish? ")
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(hashcash-wait-async)
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(hashcash-cancel-async))))
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;;;###autoload
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(defun hashcash-verify-payment (token &optional resource amount)
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"Verify a hashcash payment."
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(let* ((split (split-string token ":"))
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(key (if (< (hashcash-version token) 1.2)
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(nth 1 split)
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(pcase (string-to-number (nth 0 split))
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(0 (nth 2 split))
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(1 (nth 3 split))))))
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(cond ((null resource)
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(let ((elt (assoc key hashcash-accept-resources)))
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(and elt (hashcash-check-payment token (car elt)
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(or (cadr elt) hashcash-default-accept-payment)))))
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((equal token key)
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(hashcash-check-payment token resource
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(or amount hashcash-default-accept-payment)))
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(t nil))))
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;;;###autoload
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(defun mail-add-payment (&optional arg async)
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"Add X-Payment: and X-Hashcash: headers with a hashcash payment
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for each recipient address. Prefix arg sets default payment temporarily.
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Set ASYNC to t to start asynchronous calculation. (See
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`mail-add-payment-async')."
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(interactive "P")
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(let ((hashcash-default-payment (if arg (prefix-numeric-value arg)
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hashcash-default-payment))
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(addrlist nil))
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(save-excursion
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(save-restriction
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(message-narrow-to-headers)
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(let ((to (hashcash-strip-quoted-names (mail-fetch-field "To" nil t)))
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(cc (hashcash-strip-quoted-names (mail-fetch-field "Cc" nil t)))
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(ng (hashcash-strip-quoted-names (mail-fetch-field "Newsgroups"
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nil t))))
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(when to
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(setq addrlist (split-string to ",[ \t\n]*")))
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(when cc
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(setq addrlist (nconc addrlist (split-string cc ",[ \t\n]*"))))
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(when (and hashcash-in-news ng)
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(setq addrlist (nconc addrlist (split-string ng ",[ \t\n]*")))))
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(when addrlist
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(mapc (if async
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#'hashcash-insert-payment-async
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#'hashcash-insert-payment)
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addrlist)))))
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t)
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;;;###autoload
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(defun mail-add-payment-async (&optional arg)
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"Add X-Payment: and X-Hashcash: headers with a hashcash payment
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for each recipient address. Prefix arg sets default payment temporarily.
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Calculation is asynchronous."
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(interactive "P")
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(mail-add-payment arg t))
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;;;###autoload
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(defun mail-check-payment (&optional arg)
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"Look for a valid X-Payment: or X-Hashcash: header.
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Prefix arg sets default accept amount temporarily."
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(interactive "P")
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(let ((hashcash-default-accept-payment (if arg (prefix-numeric-value arg)
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hashcash-default-accept-payment))
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(version (hashcash-version (hashcash-generate-payment "x" 1))))
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(save-excursion
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(goto-char (point-min))
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(search-forward "\n\n")
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(beginning-of-line)
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(let ((end (point))
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(ok nil))
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(goto-char (point-min))
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(while (and (not ok) (search-forward "X-Payment: hashcash " end t))
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(let ((value (split-string (hashcash-token-substring) " ")))
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(when (equal (car value) (number-to-string version))
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(setq ok (hashcash-verify-payment (cadr value))))))
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(goto-char (point-min))
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(while (and (not ok) (search-forward "X-Hashcash: " end t))
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(setq ok (hashcash-verify-payment (hashcash-token-substring))))
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(when ok
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(message "Payment valid"))
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ok))))
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(define-obsolete-function-alias 'hashcash-point-at-bol #'line-beginning-position "28.1")
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(define-obsolete-function-alias 'hashcash-point-at-eol #'line-end-position "28.1")
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(provide 'hashcash)
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;;; hashcash.el ends here
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