The application/zlib and application/gzip media types
draft-levine-application-gzip-02

Abstract

This document defines the 'application/gzip' and 'application/zlib' media types for compressed data using the gzip and zlib compression formats.

Status of this Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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 http://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on October 01, 2012.

Copyright Notice

Copyright (c) 2012 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

1. Introduction

The Zlib [RFC1950] and gzip [RFC1952] formats are widely used compression formats. Zlib is a stream format, while gzip adds header and trailer fields more appropriate for a file format. Both implement the DEFLATE compression scheme described in [RFC1951].

They are used to compress a wide variety of material, from unstructured text to structured data to executable code.

Some applications have informally used media types including application/gzip-compressed, application/gzipped, application/x-gunzip, application/x-gzip, application/x-gzip-compressed, and gzip/document to describe data compressed with gzip. The media types defined in this document should replace those media types in future applications.

2. The Application/Zlib Media Type

The application/zlib media type describes a block of data that is compressed using Zlib [RFC1950] compression. The data is a stream of bytes as described in RFC 1950.

2.1. Registration Details

Type name: application

Subtype name: zlib

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: needs base64 or other encoding that allows arbitrary binary data

Security considerations: See section Section 4 below

Interoperability considerations: N/A

Published specification: [RFC1950]

Applications that use this media type: anywhere data size is an issue

Additional information:

• Magic number(s): first byte is usually 0x78 but can also be 0x08, 0x18, 0x28, 0x38, 0x48, 0x58, or 0x68.
• File extension(s): N/A
• Macintosh file type code(s): N/A

Person and email address to contact for further information: see http://zlib.net/

Intended usage: COMMON

Restrictions on usage: N/A

Author: John Levine

Change controller: IETF

3. The Application/Gzip Media Type

The application/gzip media type describes a block of data that is compressed using gzip [RFC1952] compression. The data is a stream of bytes as described in RFC 1952.

3.1. Registration Details

Type name: application

Subtype name: gzip

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: needs base64 or other encoding that allows arbitrary binary data

Security considerations: See section Section 4 below

Interoperability considerations: N/A

Published specification: [RFC1952]

Applications that use this media type: anywhere data size is an issue

Additional information:

• Magic number(s): first two bytes are 0x1f, 0x8b.
• File extension(s): gz
• Macintosh file type code(s): N/A

Person and email address to contact for further information: see http://www.gzip.org/

Intended usage: COMMON

Restrictions on usage: N/A

Author: John Levine

Change controller: IETF

4. Security Considerations

Zlib and gzip compression can be used to compress arbitrary binary data such as hostile executable code. Also, data that purports to be in zlib or gzip format may not be, and fields that are supposed to be flags, lengths, or pointers, could contain anything. Applications should treat any data with due skepticism.

Also see the security considerations in the underlying format documents, Section 5 of [RFC1950], Section 6 of [RFC1951], and Section 4 of [RFC1952].

5. References

Appendix A. Change log

Note to editor: Please remove this section before publication.

Appendix A.1. Changes from -01 to -02

Fix gzip.org

Note other former names

Appendix A.2. Changes from -00 to -01

Note former x-gzip

Refer to security sections in underlying format docs

Author's Address

Table of Contents

• 1. Introduction
• 2. The Application/Zlib Media Type
• 2.1. Registration Details
• 3. The Application/Gzip Media Type
• 3.1. Registration Details
• 4. Security Considerations
• 5. References
• Appendix A. Change log
• Appendix A.1. Changes from -01 to -02
• Appendix A.2. Changes from -00 to -01
• Author's Address