--- 1/draft-ietf-extra-imap-fetch-preview-04.txt 2019-04-28 22:13:13.129828185 -0700 +++ 2/draft-ietf-extra-imap-fetch-preview-05.txt 2019-04-28 22:13:13.157828892 -0700 @@ -1,18 +1,18 @@ EXTRA M. Slusarz Internet-Draft Open-Xchange Inc. -Intended status: Standards Track April 24, 2019 -Expires: October 26, 2019 +Intended status: Standards Track April 28, 2019 +Expires: October 30, 2019 IMAP4 Extension: Message Preview Generation - draft-ietf-extra-imap-fetch-preview-04 + draft-ietf-extra-imap-fetch-preview-05 Abstract This document specifies an Internet Message Access Protocol (IMAP) protocol extension allowing a client to request a server-generated abbreviated representation of message data useful as a contextual preview of the entire message. Status of This Memo @@ -22,21 +22,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on October 26, 2019. + This Internet-Draft will expire on October 30, 2019. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -101,24 +101,24 @@ will likely strip the markup tags to obtain textual content. However, without fetching the entire content of the part, there is no way to guarantee that sufficient non-tag content will exist unless either 1) the entire part is retrieved or 2) an additional partial FETCH is executed when the client determines that it does not possess sufficient data from a previous partial FETCH to display an adequate representation of the preview. Finally, server generation allows caching in a centralized location. Using server-generated previews allows global generation once per - message, and then cached indefinitely. Retrieval of message data may - be expensive within a server, for example, so a server can be - configured to reduce its storage retrieval load by pre-generating - preview data. + message, and then cached for the retention period of the source + message. Retrieval of message data may be expensive within a server, + for example, so a server can be configured to reduce its storage + retrieval load by pre-generating preview data. A server indicates support for this extension by listing one or more capability names consisting of "PREVIEW=" followed by a supported preview algorithm name. This format provides for future upwards- compatible extensions and/or the ability to use locally-defined preview algorithms. 2. Conventions Used In This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", @@ -417,23 +417,24 @@ Implementation of this extension might enable denial-of-service attacks against server resources, due to excessive memory or CPU usage during preview generation or increased storage usage if preview results are stored on the server after generation. Servers MAY limit the resources that preview generation uses. In order to mitigate such attacks, servers SHOULD log the client authentication identity on FETCH PREVIEW operations in order to facilitate tracking of abusive clients. Just as the messages they summarize, preview data may contain - sensitive information. If stored permanently, these previews MUST be - protected with equivalent authorization and confidentiality controls - as the source message. + sensitive information. If generated preview data is stored on the + server, e.g. for caching purposes, these previews MUST be protected + with equivalent authorization and confidentiality controls as the + source message. 10. References 10.1. Normative References [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046, November 1996, . @@ -580,20 +581,25 @@ o Add normative reference for text/plain o Add warning regarding buffers and multiple octet preview characters o Clarify how to handle preview data return when using an explicit algorithm list o Various editorial fixes + Changes from draft-ietf-extra-imap-fetch-preview-04: + + o Make clear that preview caching is tied to retention period of the + source message + Acknowledgments The author would like to thank the following people for their comments and contributions to this document: Stephan Bosch, Bron Gondwana, Teemu Huovila, Steffen Lehmann, Alexey Melnikov, Chris Newman, Jeff Sipek, Timo Sirainen, Steffen Templin, and Aki Tuomi. Author's Address Michael M. Slusarz