[Search] [pdf|bibtex] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 rfc4146                                 Informational
Internet Draft: Notify Mail                                  R. Gellens
Document: draft-gellens-notify-mail-02.txt                     QUALCOMM
Expires: July 2005                                         January 2005




                      Simple New Mail Notification


Status of this Memo

    By submitting this Internet-Draft, each author represents that any
    applicable patent or other IPR claims of which he or she is aware
    have been or will be disclosed, and any of which he or she becomes
    aware will be disclosed, in accordance with Section 6 of RFC 3668.

    By submitting this Internet-Draft, I accept the provisions of
    Section 3 of RFC 3667 (BCP 78).

    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups.  Note that
    other groups may also distribute working documents as Internet-
    Drafts.

    Internet-Drafts are draft documents valid for a maximum of six
    months and may be updated, replaced, or obsoleted by other documents
    at any time.  It is inappropriate to use Internet-Drafts as
    reference material or to cite them other than as "work in progress."

    The list of current Internet-Drafts can be accessed at
    http://www.ietf.org/ietf/1id-abstracts.txt The list of
    Internet-Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html.




Copyright Notice

    Copyright (C) The Internet Society (2005).  All Rights Reserved.


Abstract

    This memo documents a long-standing technique, supported by a large
    number of mail servers, which allows users to be notified of new
    mail.  In addition to server support, there are a number of clients
    which support this, ranging from full email clients to specialized
    clients whose only purpose is to receive new mail notifications and


Gellens                    Expires July 2005                    [Page 1]


Internet Draft                 Notify Mail                 January 2005


    alert a mail client.

    In brief, the technique is for the server to send the string
    "nm_notifyuser" CRLF to the finger port on the IP address (either
    configured or last used) for the user who has received new mail.














































Gellens                    Expires July 2005                    [Page 2]


Internet Draft                 Notify Mail                 January 2005


                           Table of Contents

     1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.  Conventions Used in this Document . . . . . . . . . . . . . . 3
     3.  Simple Mail Notification . . . . . . . . . . . . . . . . . .  3
     4.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     5.  Security Considerations  . . . . . . . . . . . . . . . . . .  4
     6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
     7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .  5
     8.  Normative References  . . . . . . . . . . . . . . . . . . . . 5
     9.  Informative References . . . . . . . . . . . . . . . . . . .  5
    10.  Author's Addresses  . . . . . . . . . . . . . . . . . . . . . 5
       Intellectual Property Statement  . . . . . . . . . . . . . . .  5
       Full Copyright Statement  . . . . . . . . . . . . . . . . . . . 6
       Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . .  6


1.  Introduction

    There is a long-standing technique supported by a large number of
    mail servers which allows users to be notified of new mail.  In
    addition to server support, there are a number of clients which
    support this, ranging from full email clients to specialized clients
    whose only purpose is to receive new mail notifications and alert a
    mail client.  This technique is sometimes known as "notify mail"
    (after a shareware client of the same name), sometimes called
    "biff", and sometimes the "finger hack".


2.  Conventions Used in this Document

    In examples, "C:" is used to indicate lines sent by the client, and
    "S:" indicates those sent by the server.  Line breaks within a
    command example are for editorial purposes only.  Line breaks in the
    protocol are indicated by "CRLF".


3.  Simple Mail Notification

    The technique is for the server to send the string "nm_notifyuser"
    immediately followed by CRLF to the finger port on the IP address
    for the user who has received new mail.  The finger port is 79.
    (Note that only the port for finger is used; the finger protocol
    itself is not used.)

    The IP address to use may be configured, or the server may use the
    IP address that was last used to check mail by the user.  Typically
    this is a per-account configuration option.



Gellens                    Expires July 2005                    [Page 3]


Internet Draft                 Notify Mail                 January 2005


    To be useful, on the client system a process must be listening to
    the finger port.  When it receives the "nm_notifyuser" string, it
    takes a configured action, typically instructing a mail client to
    fetch mail.

    Normally, a TCP connection to the target computer is opened, the
    "nm_notifyuser" string is sent, and the connection is closed without
    waiting for any response.

    In some cases UDP is used instead of TCP, but the default and
    general practice is TCP.  Even though one a single message in one
    direction is sent (with no reply), TCP is used most often, probably
    for reliability.

    There is an assumption that the client listening on an IP address
    only has responsibility for one email account; if a client can check
    multiple accounts and receives the "nm_notifyuser" string, it does
    not know which account received the mail.

    There is a requirement that a finger daemon is not active on the
    client.


4.  Example

    This example assumes that new mail has arrived at server
    mail.isp.example.com for account fastness@example.net.  The server
    has determined an IP address to which notification should be sent.

        C: <listens on TCP port 79>
        S: <opens TCP connection to IP address port 79>
        C: <accepts inbound connection on port 79>
        S: nm_notifyuserCRLF
        S: <closes TCP connection>


5.  Security Considerations

    There is of course no assurance that the "nm_notifyuser" message is
    being sent to the correct IP address.  Nor does the listening agent
    on the client system have any assurance that a "nm_notifyuser"
    string was sent by a mail server which has received new mail for the
    user.

    It is trivial for an attacker to send large numbers of
    "nm_notifyuser" messages to any targeted system.  Client systems
    listening for this message SHOULD implement protections against
    being flooded with notifications.  Many server systems already
    implement protections against users logging in and checking mail too


Gellens                    Expires July 2005                    [Page 4]


Internet Draft                 Notify Mail                 January 2005


    frequently.

    Since use of this protocol requires that a port be open with an
    agent listening on it, if that agent contains vulnerabilities it may
    create a remotely exploitable attack (for example, buffer overflows
    permitting an attacker to execute arbitrary code on the client
    system with the permissions of the agent).  As usual with a process
    listening on a port, the process should execute with the least
    possible privelege level and access.


6.  IANA Considerations

    The notify mail hack (and this document) should be included as an
    additional usage for port 79.


7.  Acknowledgments

    The NotifyMail shareware utility was written by Scott Gruby.


8.  Normative References

    None.


9.  Informative References

    None.


10.  Author's Addresses

    Randall Gellens
    QUALCOMM Incorporated
    6455 Lusk Blvd.
    San Diego, CA  92121-2779
    USA
    randy@qualcomm.Com


Intellectual Property Statement

    The IETF takes no position regarding the validity or scope of any
    Intellectual Property Rights or other rights that might be claimed
    to pertain to the implementation or use of the technology described
    in this document or the extent to which any license under such
    rights might or might not be available; nor does it represent that


Gellens                    Expires July 2005                    [Page 5]


Internet Draft                 Notify Mail                 January 2005


    it has made any independent effort to identify any such rights.
    Information on the procedures with respect to rights in RFC
    documents can be found in BCP 78 and BCP 79.

    Copies of IPR disclosures made to the IETF Secretariat and any
    assurances of licenses to be made available, or the result of an
    attempt made to obtain a general license or permission for the use
    of such proprietary rights by implementers or users of this
    specification can be obtained from the IETF on-line IPR repository
    at http://www.ietf.org/ipr.

    The IETF invites any interested party to bring to its attention any
    copyrights, patents or patent applications, or other proprietary
    rights that may cover technology that may be required to implement
    this standard.  Please address the information to the IETF at
    ietf-ipr@ietf.org.


Full Copyright Statement

    Copyright (C) The Internet Society (2005).  This document is subject
    to the rights, licenses and restrictions contained in BCP 78, and
    except as set forth therein, the authors retain all their rights.


Disclaimer

    This document and the information contained herein are provided on
    an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
    REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
    INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
    THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
    WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

















Gellens                    Expires July 2005                    [Page 6]