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c3f58a6651
* lisp/erc/erc-sasl.el (erc-sasl-user): Fix doc string. (erc-sasl--get-user): Don't apply casemapping when the option `erc-sasl-user' is set to `:nick'. While many servers and auth-services providers perform case-folding when comparing SASL usernames, only some recognize RFC1459 mappings, which ERC previously applied blindly. Instead, ERC now behaves like other clients in leaving such preparation in the hands of the server. This bug was introduced with changes new to ERC 5.5 and Emacs 29 (bug#29108).
448 lines
18 KiB
EmacsLisp
448 lines
18 KiB
EmacsLisp
;;; erc-sasl.el --- SASL for ERC -*- lexical-binding: t -*-
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;; Copyright (C) 2022-2023 Free Software Foundation, Inc.
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;;
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;; This file is part of GNU Emacs.
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;;
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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
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;; by the Free Software Foundation, either version 3 of the License,
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;; or (at your option) any later version.
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;;
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;; GNU Emacs is distributed in the hope that it will be useful, but
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;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;; General Public License for more details.
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;;
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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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;; This "non-IRCv3" implementation resembles others that have surfaced
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;; over the years, the first possibly being from Joseph Gay:
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;;
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;; https://lists.gnu.org/archive/html/erc-discuss/2012-02/msg00001.html
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;;
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;; See options and Info manual for usage.
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;;
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;; TODO:
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;;
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;; - Find a way to obfuscate the password in memory (via something
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;; like `auth-source--obfuscate'); it's currently visible in
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;; backtraces.
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;;
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;; - Implement a proxy mechanism that chooses the strongest available
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;; mechanism for you. Requires CAP 3.2 (see bug#49860).
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;;
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;; - Integrate with whatever solution ERC eventually settles on to
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;; handle user options for different network contexts. At the
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;; moment, this does its own thing for stashing and restoring
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;; session options, but ERC should make abstractions available for
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;; all local modules to use, possibly based on connection-local
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;; variables.
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;;; Code:
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(require 'erc)
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(require 'rx)
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(require 'sasl)
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(require 'sasl-scram-rfc)
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(require 'sasl-scram-sha256 nil t) ; not present in Emacs 27
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(defgroup erc-sasl nil
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"SASL for ERC."
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:group 'erc
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:package-version '(ERC . "5.4.1")) ; FIXME increment on next release
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(defcustom erc-sasl-mechanism 'plain
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"SASL mechanism to connect with.
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Note that any value other than nil or `external' likely requires
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`erc-sasl-user' and `erc-sasl-password'."
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:type '(choice (const plain)
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(const external)
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(const scram-sha-1)
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(const scram-sha-256)
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(const scram-sha-512)
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(const ecdsa-nist256p-challenge)))
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(defcustom erc-sasl-user :user
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"Account username to send when authenticating.
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This option specifies the SASL authentication identity, or
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\"authcid\". A value of `:user' or `:nick' indicates that the
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corresponding connection parameter on file should be used. ERC
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typically obtains these from arguments given to its entry-point
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commands, `erc' and `erc-tls'."
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:type '(choice string (const :user) (const :nick)))
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(defcustom erc-sasl-password :password
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"Optional account password to send when authenticating.
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When `erc-sasl-auth-source-function' is a function, ERC will
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attempt an auth-source query and prompt for input if it fails.
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Otherwise, when the value is a nonempty string, ERC will use it
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unconditionally for most mechanisms. Likewise with `:password',
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except ERC will instead use the \"session password\" on file, if
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any, which often originates from the entry-point commands `erc'
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or `erc-tls'. As with auth-source, ERC will prompt for input as
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a fallback.
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Note that, with `:password', ERC will forgo sending a traditional
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server password via the IRC \"PASS\" command. Also, when
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`erc-sasl-mechanism' is set to `ecdsa-nist256p-challenge', this
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option should hold the file name of the key."
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:type '(choice (const nil) (const :password) string symbol))
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(defcustom erc-sasl-auth-source-function nil
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"Function to query auth-source for an SASL password.
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If provided, this function should expect to be called with any
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number of keyword params known to `auth-source-search', even
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though ERC itself only specifies `:user' paired with a
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\"resolved\" `erc-sasl-user' value. When calling this function,
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ERC binds all options defined in this library, such as
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`erc-sasl-password', to their values from entry-point invocation.
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In return, ERC expects a string to send as the SASL password, or
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nil, in which case, ERC will prompt the for input. See info
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node `(erc) auth-source' for details on ERC's auth-source
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integration."
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:type '(choice (function-item erc-sasl-auth-source-password-as-host)
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(function-item erc-auth-source-search)
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(const nil)
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function))
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(defcustom erc-sasl-authzid nil
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"SASL authorization identity, likely unneeded for everyday use."
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:type '(choice (const nil) string))
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;; Analogous to what erc-backend does to persist opening params.
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(defvar-local erc-sasl--options nil)
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;; Session-local (server buffer) SASL subproto state
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(defvar-local erc-sasl--state nil)
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(cl-defstruct erc-sasl--state
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"Holder for client object and subproto state."
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(client nil :type vector)
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(step nil :type vector)
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(pending nil :type string))
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(defun erc-sasl--get-user ()
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(pcase (alist-get 'user erc-sasl--options)
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(:user erc-session-username)
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(:nick (erc-current-nick))
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(v v)))
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(defun erc-sasl-auth-source-password-as-host (&rest plist)
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"Call `erc-auth-source-search' with `erc-sasl-password' as `:host'.
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But only do so when it's a string or a non-nil symbol, unless
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that symbol is `:password', in which case, use a non-nil
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`erc-session-password' instead. Otherwise, just defer to
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`erc-auth-source-search' to pick a suitable `:host'. Expect
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PLIST to contain keyword params known to `auth-source-search'."
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(when erc-sasl-password
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(when-let ((host (if (eq :password erc-sasl-password)
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(and (not (functionp erc-session-password))
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erc-session-password)
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erc-sasl-password)))
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(setq plist `(,@plist :host ,(format "%s" host)))))
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(apply #'erc-auth-source-search plist))
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(defun erc-sasl--read-password (prompt)
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"Return configured option or server password.
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If necessary, pass PROMPT to `read-passwd'."
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(if-let ((found (pcase (alist-get 'password erc-sasl--options)
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((guard (alist-get 'authfn erc-sasl--options))
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(let-alist erc-sasl--options
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(let ((erc-sasl-user .user)
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(erc-sasl-password .password)
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(erc-sasl-mechanism .mechanism)
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(erc-sasl-authzid .authzid)
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(erc-sasl-auth-source-function .authfn))
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(funcall .authfn :user (erc-sasl--get-user)))))
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(:password erc-session-password)
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((and (pred stringp) v) (unless (string-empty-p v) v)))))
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(copy-sequence (erc--unfun found))
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(read-passwd prompt)))
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(defun erc-sasl--plain-response (client steps)
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(let ((sasl-read-passphrase #'erc-sasl--read-password))
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(sasl-plain-response client steps)))
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(declare-function erc-compat--29-sasl-scram--client-final-message "erc-compat"
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(hash-fun block-length hash-length client step))
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(defun erc-sasl--scram-sha-hack-client-final-message (&rest args)
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;; In the future (29+), we'll hopefully be able to call
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;; `sasl-scram--client-final-message' directly
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(require 'erc-compat)
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(let ((sasl-read-passphrase #'erc-sasl--read-password))
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(apply #'erc-compat--29-sasl-scram--client-final-message args)))
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(defun erc-sasl--scram-sha-1-client-final-message (client step)
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(erc-sasl--scram-sha-hack-client-final-message 'sha1 64 20 client step))
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(defun erc-sasl--scram-sha-256-client-final-message (client step)
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(erc-sasl--scram-sha-hack-client-final-message 'sasl-scram-sha256 64 32
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client step))
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(defun erc-sasl--scram-sha512 (object &optional start end binary)
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(secure-hash 'sha512 object start end binary))
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(defun erc-sasl--scram-sha-512-client-final-message (client step)
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(erc-sasl--scram-sha-hack-client-final-message #'erc-sasl--scram-sha512
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128 64 client step))
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(defun erc-sasl--scram-sha-512-authenticate-server (client step)
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(sasl-scram--authenticate-server #'erc-sasl--scram-sha512
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128 64 client step))
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(defun erc-sasl--ecdsa-first (client _step)
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"Return CLIENT name."
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(sasl-client-name client))
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;; FIXME do this with gnutls somehow
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(defun erc-sasl--ecdsa-sign (client step)
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"Return signed challenge for CLIENT and current STEP."
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(let ((challenge (sasl-step-data step)))
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(with-temp-buffer
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(set-buffer-multibyte nil)
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(insert challenge)
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(call-process-region (point-min) (point-max)
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"openssl" 'delete t nil "pkeyutl" "-inkey"
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(sasl-client-property client 'ecdsa-keyfile)
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"-sign")
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(buffer-string))))
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(pcase-dolist
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(`(,name . ,steps)
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'(("PLAIN"
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erc-sasl--plain-response)
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("EXTERNAL"
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ignore)
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("SCRAM-SHA-1"
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erc-compat--29-sasl-scram-client-first-message
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erc-sasl--scram-sha-1-client-final-message
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sasl-scram-sha-1-authenticate-server)
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("SCRAM-SHA-256"
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erc-compat--29-sasl-scram-client-first-message
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erc-sasl--scram-sha-256-client-final-message
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sasl-scram-sha-256-authenticate-server)
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("SCRAM-SHA-512"
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erc-compat--29-sasl-scram-client-first-message
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erc-sasl--scram-sha-512-client-final-message
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erc-sasl--scram-sha-512-authenticate-server)
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("ECDSA-NIST256P-CHALLENGE"
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erc-sasl--ecdsa-first
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erc-sasl--ecdsa-sign)))
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(let ((feature (intern (concat "erc-sasl-" (downcase name)))))
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(put feature 'sasl-mechanism (sasl-make-mechanism name steps))
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(provide feature)))
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(cl-defgeneric erc-sasl--create-client (mechanism)
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"Create and return a new SASL client object for MECHANISM."
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(let ((sasl-mechanism-alist (copy-sequence sasl-mechanism-alist))
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(sasl-mechanisms sasl-mechanisms)
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(name (upcase (symbol-name mechanism)))
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(feature (intern-soft (concat "erc-sasl-" (symbol-name mechanism))))
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client)
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(when feature
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(setf (alist-get name sasl-mechanism-alist nil nil #'equal) `(,feature))
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(cl-pushnew name sasl-mechanisms :test #'equal)
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(setq client (sasl-make-client (sasl-find-mechanism (list name))
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(erc-sasl--get-user)
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"N/A" "N/A"))
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(sasl-client-set-property client 'authenticator-name
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(alist-get 'authzid erc-sasl--options))
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client)))
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(cl-defmethod erc-sasl--create-client ((_ (eql plain)))
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"Create and return a new PLAIN client object."
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;; https://tools.ietf.org/html/rfc4616#section-2.
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(let* ((sans (remq (assoc "PLAIN" sasl-mechanism-alist)
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sasl-mechanism-alist))
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(sasl-mechanism-alist (cons '("PLAIN" erc-sasl-plain) sans))
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(authc (erc-sasl--get-user))
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(port (if (numberp erc-session-port)
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(number-to-string erc-session-port)
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"0"))
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;; In most cases, `erc-server-announced-name' won't be known.
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(host (or erc-server-announced-name erc-session-server))
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(mech (sasl-find-mechanism '("PLAIN")))
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(client (sasl-make-client mech authc port host)))
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(sasl-client-set-property client 'authenticator-name
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(alist-get 'authzid erc-sasl--options))
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client))
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(cl-defmethod erc-sasl--create-client ((_ (eql scram-sha-256)))
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"Create and return a new SCRAM-SHA-256 client."
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(when (featurep 'sasl-scram-sha256)
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(cl-call-next-method)))
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(cl-defmethod erc-sasl--create-client ((_ (eql scram-sha-512)))
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"Create and return a new SCRAM-SHA-512 client."
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(when (featurep 'sasl-scram-sha256)
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(cl-call-next-method)))
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(cl-defmethod erc-sasl--create-client ((_ (eql ecdsa-nist256p-challenge)))
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"Create and return a new ECDSA-NIST256P-CHALLENGE client."
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(let ((keyfile (cdr (assq 'password erc-sasl--options))))
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;; Better to signal usage errors now than inside a process filter.
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(cond ((or (not (stringp keyfile)) (not (file-readable-p keyfile)))
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(erc-display-error-notice
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nil "`erc-sasl-password' not accessible as a file")
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nil)
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((not (executable-find "openssl"))
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(erc-display-error-notice nil "Could not find openssl program")
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nil)
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(t
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(let ((client (cl-call-next-method)))
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(sasl-client-set-property client 'ecdsa-keyfile keyfile)
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client)))))
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;; This stands alone because it's also used by bug#49860.
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(defun erc-sasl--init ()
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(setq erc-sasl--state (make-erc-sasl--state))
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;; If the previous attempt failed during registration, this may be
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;; non-nil and contain erroneous values, but how can we detect that?
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;; What if the server dropped the connection for some other reason?
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(setq erc-sasl--options
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(or (and erc--server-reconnecting
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(alist-get 'erc-sasl--options erc--server-reconnecting))
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`((user . ,erc-sasl-user)
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(password . ,erc-sasl-password)
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(mechanism . ,erc-sasl-mechanism)
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(authfn . ,erc-sasl-auth-source-function)
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(authzid . ,erc-sasl-authzid)))))
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(defun erc-sasl--mechanism-offered-p (offered)
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"Return non-nil when OFFERED appears among a list of mechanisms."
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(string-match-p (rx-to-string
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`(: (| bot ",")
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,(symbol-name (alist-get 'mechanism erc-sasl--options))
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(| eot ",")))
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(downcase offered)))
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(erc-define-catalog
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'english
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'((s902 . "ERR_NICKLOCKED nick %n unavailable: %s")
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(s904 . "ERR_SASLFAIL (authentication failed) %s")
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(s905 . "ERR SASLTOOLONG (credentials too long) %s")
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(s906 . "ERR_SASLABORTED (authentication aborted) %s")
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(s907 . "ERR_SASLALREADY (already authenticated) %s")
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(s908 . "RPL_SASLMECHS (unsupported mechanism: %m) %s")))
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(define-erc-module sasl nil
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"Non-IRCv3 SASL support for ERC.
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This doesn't solicit or validate a suite of supported mechanisms."
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;; See bug#49860 for a CAP 3.2-aware WIP implementation.
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((unless erc--target
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(erc-sasl--init)
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(let* ((mech (alist-get 'mechanism erc-sasl--options))
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(client (erc-sasl--create-client mech)))
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(unless client
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(erc-display-error-notice
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nil (format "Unknown or unsupported SASL mechanism: %s" mech))
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(erc-error "Unknown or unsupported SASL mechanism: %s" mech))
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(setf (erc-sasl--state-client erc-sasl--state) client))))
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((kill-local-variable 'erc-sasl--state)
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(kill-local-variable 'erc-sasl--options))
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'local)
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(define-erc-response-handler (AUTHENTICATE)
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"Begin or resume an SASL session." nil
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(if-let* ((response (car (erc-response.command-args parsed)))
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((= 400 (length response))))
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(cl-callf (lambda (s) (concat s response))
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(erc-sasl--state-pending erc-sasl--state))
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(cl-assert response t)
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(when (string= "+" response)
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(setq response ""))
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(setf response (base64-decode-string
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(concat (erc-sasl--state-pending erc-sasl--state)
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response))
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(erc-sasl--state-pending erc-sasl--state) nil)
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(let ((client (erc-sasl--state-client erc-sasl--state))
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(step (erc-sasl--state-step erc-sasl--state))
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data)
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(when step
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(sasl-step-set-data step response))
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(setq step (setf (erc-sasl--state-step erc-sasl--state)
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(sasl-next-step client step))
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data (sasl-step-data step))
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(when (string= data "")
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(setq data nil))
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(when data
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(setq data (erc--unfun (base64-encode-string data t))))
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(erc-server-send (concat "AUTHENTICATE " (or data "+"))))))
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(defun erc-sasl--destroy (proc)
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(run-hook-with-args 'erc-quit-hook proc)
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(delete-process proc)
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(erc-error "Disconnected from %s; please review SASL settings" proc))
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(define-erc-response-handler (902)
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"Handle an ERR_NICKLOCKED response." nil
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(erc-display-message parsed '(notice error) 'active 's902
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?n (car (erc-response.command-args parsed))
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?s (erc-response.contents parsed))
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(erc-sasl--destroy proc))
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(define-erc-response-handler (903)
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"Handle a RPL_SASLSUCCESS response." nil
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(when erc-sasl-mode
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(unless erc-server-connected
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(erc-server-send "CAP END")))
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(erc-display-message parsed 'notice proc (erc-response.contents parsed)))
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(define-erc-response-handler (907)
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"Handle a RPL_SASLALREADY response." nil
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(erc-display-message parsed '(notice error) 'active 's907
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?s (erc-response.contents parsed)))
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(define-erc-response-handler (904 905 906)
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"Handle various SASL-related error responses." nil
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(erc-display-message parsed '(notice error) 'active
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(intern (format "s%s" (erc-response.command parsed)))
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?s (erc-response.contents parsed))
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(erc-sasl--destroy proc))
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(define-erc-response-handler (908)
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"Handle a RPL_SASLALREADY response." nil
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(erc-display-message parsed '(notice error) 'active 's908
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?m (alist-get 'mechanism erc-sasl--options)
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?s (string-join (cdr (erc-response.command-args parsed))
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" "))
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(erc-sasl--destroy proc))
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(defvar erc-sasl--send-cap-ls nil
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|
"Whether to send an opening \"CAP LS\" command.
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|
This is an escape hatch for picky servers. If you need it turned
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|
into a user option, please let ERC know via \\[erc-bug].
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Otherwise, expect it to disappear in subsequent versions.")
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(cl-defmethod erc--register-connection (&context (erc-sasl-mode (eql t)))
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"Send speculative CAP and pipelined AUTHENTICATE and hope for the best."
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|
(if-let* ((c (erc-sasl--state-client erc-sasl--state))
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|
(m (sasl-mechanism-name (sasl-client-mechanism c))))
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|
(progn
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(erc-server-send (if erc-sasl--send-cap-ls "CAP LS" "CAP REQ :sasl"))
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|
(let ((erc-session-password
|
|
(and erc-session-password
|
|
(not (eq :password (alist-get 'password erc-sasl--options)))
|
|
erc-session-password))
|
|
(erc-session-username
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|
;; The username may contain a colon or a space
|
|
(if (eq :user (alist-get 'user erc-sasl--options))
|
|
(erc-current-nick)
|
|
erc-session-username)))
|
|
(cl-call-next-method))
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|
(when erc-sasl--send-cap-ls
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|
(erc-server-send "CAP REQ :sasl"))
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|
(erc-server-send (format "AUTHENTICATE %s" m)))
|
|
(erc-sasl--destroy erc-server-process)))
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|
|
|
(provide 'erc-sasl)
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|
;;; erc-sasl.el ends here
|
|
;;
|
|
;; Local Variables:
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|
;; generated-autoload-file: "erc-loaddefs.el"
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|
;; End:
|