From: Charles Lindsey (chl@clw.cs.man.ac.uk)
Date: Thu Apr 11 2002 - 15:01:02 CDT
Bruce Lilly raised concerns about the Disposition-Notification-To-header
(deprecated for Netnews in RFC 2298) because it could cause mailbombing.
However, this problem needs to be solved in a ore general fashion,
because there might be other such undesirable headers. Here is what I
have done:
In 4.2.1 Header Names
Whilst relaying agents MUST accept, and pass on unaltered, any non-
variant header whose header-name is syntactically correct, and
reading agents MUST enable them to be displayed, at least optionally,
posting and injecting agents SHOULD NOT generate headers other than
o headers established by this standard or any extension to it;
| o those recognized by other IETF-established standards, notably the
| Email standard [RFC 2822] and its extensions, excluding any
| explicitly deprecated for Netnews (e.g. see section 9.2.1 for the
| deprecated Disposition-Notification-To-header); or,
| alternatively, those listed in some future IANA registry of
| recognized headers;
o experimental headers beginning with "X-" (as defined in 4.2.5.1);
o on a provisional basis only, headers related to new protocols
under development which are the subject of (or intended to be the
subject of) some IETF-approved RFC (whether Informational,
Experimental or Standards-Track).
In 8.2.2. Procedure to be followed by Injecting Agents
An injecting agent processes articles as follows:
4. It MUST reject any article that does not have the correct
mandatory headers for a proto-article (5 and 8.2.1) present, or
which contains any header that does not have legal contents, and it
SHOULD reject any article which contains any header deprecated for
Netnews (4.2.1).
In 8.2.2 Duties of an Incoming Gateway
News articles prepared by gateways MUST be legal news articles. In
particular, they MUST include all of the mandatory headers, MUST
fully conform to the restrictions on said headers, and SHOULD exclude
any deprecated headers (4.2.1). This often requires that a gateway
function not only as a relaying agent, but also partly as a posting
agent, aiding in the synthesis of a conforming article from non-
conforming input.
In 9.2.1. Denial of Service
Such articles intended to deny service, or other articles of an
inflammatory nature, may also have their From or Reply-To addresses
set to valid but incorrect email addresses, thus causing large
volumes of mail to descend on the true owners of those addresses.
| Similar effects could be caused by any Email header which could cause
| every reading agent receiving it to take some externally visible
| action. For example, the Disposition-Notification-To-header defined
| in [RFC 2298] could cause huge numbers of acknowledgements to be
| emailed to an unsuspecting third party (for which reason [RFC 2298]
| declares that that header SHOULD NOT be used in Netnews).
Charles H. Lindsey ---------At Home, doing my own thing------------------------
Tel: +44 161 436 6131 Fax: +44 161 436 6133 Web: http://www.cs.man.ac.uk/~chl
Email: chl@clw.cs.man.ac.uk Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K.
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