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jabber-sasl.el
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jabber-sasl.el
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;; jabber-sasl.el - SASL authentication
;; Copyright (C) 2004, 2007, 2008 - Magnus Henoch - mange@freemail.hu
;; This file is a part of jabber.el.
;; This program 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 2 of the License, or
;; (at your option) any later version.
;; This program 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 this program; if not, write to the Free Software
;; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
(require 'cl)
;;; This file uses sasl.el from FLIM or Gnus. If it can't be found,
;;; jabber-core.el won't use the SASL functions.
(eval-and-compile
(condition-case nil
(require 'sasl)
(error nil)))
;;; Alternatives to FLIM would be the command line utility of GNU SASL,
;;; or anything the Gnus people decide to use.
;;; See XMPP-CORE and XMPP-IM for details about the protocol.
(require 'jabber-xml)
(defun jabber-sasl-start-auth (jc stream-features)
;; Find a suitable common mechanism.
(let* ((mechanism-elements (car (jabber-xml-get-children stream-features 'mechanisms)))
(mechanisms (mapcar
(lambda (tag)
(car (jabber-xml-node-children tag)))
(jabber-xml-get-children mechanism-elements 'mechanism)))
(mechanism
(if (and (member "ANONYMOUS" mechanisms)
(or jabber-silent-mode (yes-or-no-p "Use anonymous authentication? ")))
(sasl-find-mechanism '("ANONYMOUS"))
(sasl-find-mechanism mechanisms))))
;; No suitable mechanism?
(if (null mechanism)
;; Maybe we can use legacy authentication
(let ((iq-auth (find "http://jabber.org/features/iq-auth"
(jabber-xml-get-children stream-features 'auth)
:key #'jabber-xml-get-xmlns
:test #'string=))
;; Or maybe we have to use STARTTLS, but can't
(starttls (find "urn:ietf:params:xml:ns:xmpp-tls"
(jabber-xml-get-children stream-features 'starttls)
:key #'jabber-xml-get-xmlns
:test #'string=)))
(cond
(iq-auth
(fsm-send jc :use-legacy-auth-instead))
(starttls
(message "STARTTLS encryption required, but disabled/non-functional at our end")
(fsm-send jc :authentication-failure))
(t
(message "Authentication failure: no suitable SASL mechanism found")
(fsm-send jc :authentication-failure))))
;; Watch for plaintext logins over unencrypted connections
(if (and (not (plist-get (fsm-get-state-data jc) :encrypted))
(member (sasl-mechanism-name mechanism)
'("PLAIN" "LOGIN"))
(not (yes-or-no-p "Jabber server only allows cleartext password transmission! Continue? ")))
(fsm-send jc :authentication-failure)
;; Start authentication.
(let* (passphrase
(client (sasl-make-client mechanism
(plist-get (fsm-get-state-data jc) :username)
"xmpp"
(plist-get (fsm-get-state-data jc) :server)))
(sasl-read-passphrase (jabber-sasl-read-passphrase-closure
jc
(lambda (p) (setq passphrase (copy-sequence p)) p)))
(step (sasl-next-step client nil)))
(jabber-send-sexp
jc
`(auth ((xmlns . "urn:ietf:params:xml:ns:xmpp-sasl")
(mechanism . ,(sasl-mechanism-name mechanism)))
,(when (sasl-step-data step)
(base64-encode-string (sasl-step-data step) t))))
(list client step passphrase))))))
(defun jabber-sasl-read-passphrase-closure (jc remember)
"Return a lambda function suitable for `sasl-read-passphrase' for JC.
Call REMEMBER with the password. REMEMBER is expected to return it as well."
(lexical-let ((password (plist-get (fsm-get-state-data jc) :password))
(bare-jid (jabber-connection-bare-jid jc))
(remember remember))
(if password
(lambda (prompt) (funcall remember (copy-sequence password)))
(lambda (prompt) (funcall remember (jabber-read-password bare-jid))))))
(defun jabber-sasl-process-input (jc xml-data sasl-data)
(let* ((client (first sasl-data))
(step (second sasl-data))
(passphrase (third sasl-data))
(sasl-read-passphrase (jabber-sasl-read-passphrase-closure
jc
(lambda (p) (setq passphrase (copy-sequence p)) p))))
(cond
((eq (car xml-data) 'challenge)
(sasl-step-set-data step (base64-decode-string (car (jabber-xml-node-children xml-data))))
(setq step (sasl-next-step client step))
(jabber-send-sexp
jc
`(response ((xmlns . "urn:ietf:params:xml:ns:xmpp-sasl"))
,(when (sasl-step-data step)
(base64-encode-string (sasl-step-data step) t)))))
((eq (car xml-data) 'failure)
(message "%s: authentication failure: %s"
(jabber-connection-bare-jid jc)
(jabber-xml-node-name (car (jabber-xml-node-children xml-data))))
(fsm-send jc :authentication-failure))
((eq (car xml-data) 'success)
;; The server might, depending on the mechanism, send
;; "additional data" (see RFC 4422) with the <success/> element.
;; Since some SASL mechanisms perform mutual authentication, we
;; need to pass this data to sasl.el - we're not necessarily
;; done just because the server says we're done.
(let* ((data (car (jabber-xml-node-children xml-data)))
(decoded (if data
(base64-decode-string data)
"")))
(sasl-step-set-data step decoded)
(condition-case e
(progn
;; Check that sasl-next-step doesn't signal an error.
;; TODO: once sasl.el allows it, check that all steps have
;; been completed.
(sasl-next-step client step)
(message "Authentication succeeded for %s" (jabber-connection-bare-jid jc))
(fsm-send jc (cons :authentication-success passphrase)))
(sasl-error
(message "%s: authentication failure: %s"
(jabber-connection-bare-jid jc)
(error-message-string e))
(fsm-send jc :authentication-failure))))))
(list client step passphrase)))
(provide 'jabber-sasl)
;;; arch-tag: 2a4a234d-34d3-49dd-950d-518c899c0fd0