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Posted to commits@commons.apache.org by bo...@apache.org on 2015/12/13 17:38:44 UTC
[5/7] commons-compress git commit: removed APPNOTE which is bound to
get outdated soon
http://git-wip-us.apache.org/repos/asf/commons-compress/blob/0c3ef534/doc/APPNOTE-6.3.4.TXT
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-File: APPNOTE.TXT - .ZIP File Format Specification
-Version: 6.3.4
-Status: Final - replaces version 6.3.3
-Revised: October 1, 2014
-Copyright (c) 1989 - 2014 PKWARE Inc., All Rights Reserved.
-
-1.0 Introduction
----------------
-
-1.1 Purpose
------------
-
- 1.1.1 This specification is intended to define a cross-platform,
- interoperable file storage and transfer format. Since its
- first publication in 1989, PKWARE, Inc. ("PKWARE") has remained
- committed to ensuring the interoperability of the .ZIP file
- format through periodic publication and maintenance of this
- specification. We trust that all .ZIP compatible vendors and
- application developers that use and benefit from this format
- will share and support this commitment to interoperability.
-
-1.2 Scope
----------
-
- 1.2.1 ZIP is one of the most widely used compressed file formats. It is
- universally used to aggregate, compress, and encrypt files into a single
- interoperable container. No specific use or application need is
- defined by this format and no specific implementation guidance is
- provided. This document provides details on the storage format for
- creating ZIP files. Information is provided on the records and
- fields that describe what a ZIP file is.
-
-1.3 Trademarks
---------------
-
- 1.3.1 PKWARE, PKZIP, SecureZIP, and PKSFX are registered trademarks of
- PKWARE, Inc. in the United States and elsewhere. PKPatchMaker,
- Deflate64, and ZIP64 are trademarks of PKWARE, Inc. Other marks
- referenced within this document appear for identification
- purposes only and are the property of their respective owners.
-
-
-1.4 Permitted Use
------------------
-
- 1.4.1 This document, "APPNOTE.TXT - .ZIP File Format Specification" is the
- exclusive property of PKWARE. Use of the information contained in this
- document is permitted solely for the purpose of creating products,
- programs and processes that read and write files in the ZIP format
- subject to the terms and conditions herein.
-
- 1.4.2 Use of the content of this document within other publications is
- permitted only through reference to this document. Any reproduction
- or distribution of this document in whole or in part without prior
- written permission from PKWARE is strictly prohibited.
-
- 1.4.3 Certain technological components provided in this document are the
- patented proprietary technology of PKWARE and as such require a
- separate, executed license agreement from PKWARE. Applicable
- components are marked with the following, or similar, statement:
- 'Refer to the section in this document entitled "Incorporating
- PKWARE Proprietary Technology into Your Product" for more information'.
-
-1.5 Contacting PKWARE
----------------------
-
- 1.5.1 If you have questions on this format, its use, or licensing, or if you
- wish to report defects, request changes or additions, please contact:
-
- PKWARE, Inc.
- 201 E. Pittsburgh Avenue, Suite 400
- Milwaukee, WI 53204
- +1-414-289-9788
- +1-414-289-9789 FAX
- zipformat@pkware.com
-
- 1.5.2 Information about this format and copies of this document are publicly
- available at:
-
- http://www.pkware.com/appnote
-
-1.6 Disclaimer
---------------
-
- 1.6.1 Although PKWARE will attempt to supply current and accurate
- information relating to its file formats, algorithms, and the
- subject programs, the possibility of error or omission cannot
- be eliminated. PKWARE therefore expressly disclaims any warranty
- that the information contained in the associated materials relating
- to the subject programs and/or the format of the files created or
- accessed by the subject programs and/or the algorithms used by
- the subject programs, or any other matter, is current, correct or
- accurate as delivered. Any risk of damage due to any possible
- inaccurate information is assumed by the user of the information.
- Furthermore, the information relating to the subject programs
- and/or the file formats created or accessed by the subject
- programs and/or the algorithms used by the subject programs is
- subject to change without notice.
-
-2.0 Revisions
---------------
-
-2.1 Document Status
---------------------
-
- 2.1.1 If the STATUS of this file is marked as DRAFT, the content
- defines proposed revisions to this specification which may consist
- of changes to the ZIP format itself, or that may consist of other
- content changes to this document. Versions of this document and
- the format in DRAFT form may be subject to modification prior to
- publication STATUS of FINAL. DRAFT versions are published periodically
- to provide notification to the ZIP community of pending changes and to
- provide opportunity for review and comment.
-
- 2.1.2 Versions of this document having a STATUS of FINAL are
- considered to be in the final form for that version of the document
- and are not subject to further change until a new, higher version
- numbered document is published. Newer versions of this format
- specification are intended to remain interoperable with with all prior
- versions whenever technically possible.
-
-2.2 Change Log
---------------
-
- Version Change Description Date
- ------- ------------------ ----------
- 5.2 -Single Password Symmetric Encryption 07/16/2003
- storage
-
- 6.1.0 -Smartcard compatibility 01/20/2004
- -Documentation on certificate storage
-
- 6.2.0 -Introduction of Central Directory 04/26/2004
- Encryption for encrypting metadata
- -Added OS X to Version Made By values
-
- 6.2.1 -Added Extra Field placeholder for 04/01/2005
- POSZIP using ID 0x4690
-
- -Clarified size field on
- "zip64 end of central directory record"
-
- 6.2.2 -Documented Final Feature Specification 01/06/2006
- for Strong Encryption
-
- -Clarifications and typographical
- corrections
-
- 6.3.0 -Added tape positioning storage 09/29/2006
- parameters
-
- -Expanded list of supported hash algorithms
-
- -Expanded list of supported compression
- algorithms
-
- -Expanded list of supported encryption
- algorithms
-
- -Added option for Unicode filename
- storage
-
- -Clarifications for consistent use
- of Data Descriptor records
-
- -Added additional "Extra Field"
- definitions
-
- 6.3.1 -Corrected standard hash values for 04/11/2007
- SHA-256/384/512
-
- 6.3.2 -Added compression method 97 09/28/2007
-
- -Documented InfoZIP "Extra Field"
- values for UTF-8 file name and
- file comment storage
-
- 6.3.3 -Formatting changes to support 09/01/2012
- easier referencing of this APPNOTE
- from other documents and standards
-
- 6.3.4 -Address change 10/01/2014
-
-
-3.0 Notations
--------------
-
- 3.1 Use of the term MUST or SHALL indicates a required element.
-
- 3.2 MAY NOT or SHALL NOT indicates an element is prohibited from use.
-
- 3.3 SHOULD indicates a RECOMMENDED element.
-
- 3.4 SHOULD NOT indicates an element NOT RECOMMENDED for use.
-
- 3.5 MAY indicates an OPTIONAL element.
-
-
-4.0 ZIP Files
--------------
-
-4.1 What is a ZIP file
-----------------------
-
- 4.1.1 ZIP files MAY be identified by the standard .ZIP file extension
- although use of a file extension is not required. Use of the
- extension .ZIPX is also recognized and MAY be used for ZIP files.
- Other common file extensions using the ZIP format include .JAR, .WAR,
- .DOCX, .XLXS, .PPTX, .ODT, .ODS, .ODP and others. Programs reading or
- writing ZIP files SHOULD rely on internal record signatures described
- in this document to identify files in this format.
-
- 4.1.2 ZIP files SHOULD contain at least one file and MAY contain
- multiple files.
-
- 4.1.3 Data compression MAY be used to reduce the size of files
- placed into a ZIP file, but is not required. This format supports the
- use of multiple data compression algorithms. When compression is used,
- one of the documented compression algorithms MUST be used. Implementors
- are advised to experiment with their data to determine which of the
- available algorithms provides the best compression for their needs.
- Compression method 8 (Deflate) is the method used by default by most
- ZIP compatible application programs.
-
-
- 4.1.4 Data encryption MAY be used to protect files within a ZIP file.
- Keying methods supported for encryption within this format include
- passwords and public/private keys. Either MAY be used individually
- or in combination. Encryption MAY be applied to individual files.
- Additional security MAY be used through the encryption of ZIP file
- metadata stored within the Central Directory. See the section on the
- Strong Encryption Specification for information. Refer to the section
- in this document entitled "Incorporating PKWARE Proprietary Technology
- into Your Product" for more information.
-
- 4.1.5 Data integrity MUST be provided for each file using CRC32.
-
- 4.1.6 Additional data integrity MAY be included through the use of
- digital signatures. Individual files MAY be signed with one or more
- digital signatures. The Central Directory, if signed, MUST use a
- single signature.
-
- 4.1.7 Files MAY be placed within a ZIP file uncompressed or stored.
- The term "stored" as used in the context of this document means the file
- is copied into the ZIP file uncompressed.
-
- 4.1.8 Each data file placed into a ZIP file MAY be compressed, stored,
- encrypted or digitally signed independent of how other data files in the
- same ZIP file are archived.
-
- 4.1.9 ZIP files MAY be streamed, split into segments (on fixed or on
- removable media) or "self-extracting". Self-extracting ZIP
- files MUST include extraction code for a target platform within
- the ZIP file.
-
- 4.1.10 Extensibility is provided for platform or application specific
- needs through extra data fields that MAY be defined for custom
- purposes. Extra data definitions MUST NOT conflict with existing
- documented record definitions.
-
- 4.1.11 Common uses for ZIP MAY also include the use of manifest files.
- Manifest files store application specific information within a file stored
- within the ZIP file. This manifest file SHOULD be the first file in the
- ZIP file. This specification does not provide any information or guidance on
- the use of manifest files within ZIP files. Refer to the application developer
- for information on using manifest files and for any additional profile
- information on using ZIP within an application.
-
- 4.1.12 ZIP files MAY be placed within other ZIP files.
-
-4.2 ZIP Metadata
-----------------
-
- 4.2.1 ZIP files are identified by metadata consisting of defined record types
- containing the storage information necessary for maintaining the files
- placed into a ZIP file. Each record type MUST be identified using a header
- signature that identifies the record type. Signature values begin with the
- two byte constant marker of 0x4b50, representing the characters "PK".
-
-
-4.3 General Format of a .ZIP file
----------------------------------
-
- 4.3.1 A ZIP file MUST contain an "end of central directory record". A ZIP
- file containing only an "end of central directory record" is considered an
- empty ZIP file. Files may be added or replaced within a ZIP file, or deleted.
- A ZIP file MUST have only one "end of central directory record". Other
- records defined in this specification MAY be used as needed to support
- storage requirements for individual ZIP files.
-
- 4.3.2 Each file placed into a ZIP file MUST be preceeded by a "local
- file header" record for that file. Each "local file header" MUST be
- accompanied by a corresponding "central directory header" record within
- the central directory section of the ZIP file.
-
- 4.3.3 Files MAY be stored in arbitrary order within a ZIP file. A ZIP
- file MAY span multiple volumes or it MAY be split into user-defined
- segment sizes. All values MUST be stored in little-endian byte order unless
- otherwise specified in this document for a specific data element.
-
- 4.3.4 Compression MUST NOT be applied to a "local file header", an "encryption
- header", or an "end of central directory record". Individual "central
- directory records" must not be compressed, but the aggregate of all central
- directory records MAY be compressed.
-
- 4.3.5 File data MAY be followed by a "data descriptor" for the file. Data
- descriptors are used to facilitate ZIP file streaming.
-
-
- 4.3.6 Overall .ZIP file format:
-
- [local file header 1]
- [encryption header 1]
- [file data 1]
- [data descriptor 1]
- .
- .
- .
- [local file header n]
- [encryption header n]
- [file data n]
- [data descriptor n]
- [archive decryption header]
- [archive extra data record]
- [central directory header 1]
- .
- .
- .
- [central directory header n]
- [zip64 end of central directory record]
- [zip64 end of central directory locator]
- [end of central directory record]
-
-
- 4.3.7 Local file header:
-
- local file header signature 4 bytes (0x04034b50)
- version needed to extract 2 bytes
- general purpose bit flag 2 bytes
- compression method 2 bytes
- last mod file time 2 bytes
- last mod file date 2 bytes
- crc-32 4 bytes
- compressed size 4 bytes
- uncompressed size 4 bytes
- file name length 2 bytes
- extra field length 2 bytes
-
- file name (variable size)
- extra field (variable size)
-
- 4.3.8 File data
-
- Immediately following the local header for a file
- SHOULD be placed the compressed or stored data for the file.
- If the file is encrypted, the encryption header for the file
- SHOULD be placed after the local header and before the file
- data. The series of [local file header][encryption header]
- [file data][data descriptor] repeats for each file in the
- .ZIP archive.
-
- Zero-byte files, directories, and other file types that
- contain no content MUST not include file data.
-
- 4.3.9 Data descriptor:
-
- crc-32 4 bytes
- compressed size 4 bytes
- uncompressed size 4 bytes
-
- 4.3.9.1 This descriptor MUST exist if bit 3 of the general
- purpose bit flag is set (see below). It is byte aligned
- and immediately follows the last byte of compressed data.
- This descriptor SHOULD be used only when it was not possible to
- seek in the output .ZIP file, e.g., when the output .ZIP file
- was standard output or a non-seekable device. For ZIP64(tm) format
- archives, the compressed and uncompressed sizes are 8 bytes each.
-
- 4.3.9.2 When compressing files, compressed and uncompressed sizes
- should be stored in ZIP64 format (as 8 byte values) when a
- file's size exceeds 0xFFFFFFFF. However ZIP64 format may be
- used regardless of the size of a file. When extracting, if
- the zip64 extended information extra field is present for
- the file the compressed and uncompressed sizes will be 8
- byte values.
-
- 4.3.9.3 Although not originally assigned a signature, the value
- 0x08074b50 has commonly been adopted as a signature value
- for the data descriptor record. Implementers should be
- aware that ZIP files may be encountered with or without this
- signature marking data descriptors and SHOULD account for
- either case when reading ZIP files to ensure compatibility.
-
- 4.3.9.4 When writing ZIP files, implementors SHOULD include the
- signature value marking the data descriptor record. When
- the signature is used, the fields currently defined for
- the data descriptor record will immediately follow the
- signature.
-
- 4.3.9.5 An extensible data descriptor will be released in a
- future version of this APPNOTE. This new record is intended to
- resolve conflicts with the use of this record going forward,
- and to provide better support for streamed file processing.
-
- 4.3.9.6 When the Central Directory Encryption method is used,
- the data descriptor record is not required, but MAY be used.
- If present, and bit 3 of the general purpose bit field is set to
- indicate its presence, the values in fields of the data descriptor
- record MUST be set to binary zeros. See the section on the Strong
- Encryption Specification for information. Refer to the section in
- this document entitled "Incorporating PKWARE Proprietary Technology
- into Your Product" for more information.
-
-
- 4.3.10 Archive decryption header:
-
- 4.3.10.1 The Archive Decryption Header is introduced in version 6.2
- of the ZIP format specification. This record exists in support
- of the Central Directory Encryption Feature implemented as part of
- the Strong Encryption Specification as described in this document.
- When the Central Directory Structure is encrypted, this decryption
- header MUST precede the encrypted data segment.
-
- 4.3.10.2 The encrypted data segment SHALL consist of the Archive
- extra data record (if present) and the encrypted Central Directory
- Structure data. The format of this data record is identical to the
- Decryption header record preceding compressed file data. If the
- central directory structure is encrypted, the location of the start of
- this data record is determined using the Start of Central Directory
- field in the Zip64 End of Central Directory record. See the
- section on the Strong Encryption Specification for information
- on the fields used in the Archive Decryption Header record.
- Refer to the section in this document entitled "Incorporating
- PKWARE Proprietary Technology into Your Product" for more information.
-
-
- 4.3.11 Archive extra data record:
-
- archive extra data signature 4 bytes (0x08064b50)
- extra field length 4 bytes
- extra field data (variable size)
-
- 4.3.11.1 The Archive Extra Data Record is introduced in version 6.2
- of the ZIP format specification. This record MAY be used in support
- of the Central Directory Encryption Feature implemented as part of
- the Strong Encryption Specification as described in this document.
- When present, this record MUST immediately precede the central
- directory data structure.
-
- 4.3.11.2 The size of this data record SHALL be included in the
- Size of the Central Directory field in the End of Central
- Directory record. If the central directory structure is compressed,
- but not encrypted, the location of the start of this data record is
- determined using the Start of Central Directory field in the Zip64
- End of Central Directory record. Refer to the section in this document
- entitled "Incorporating PKWARE Proprietary Technology into Your
- Product" for more information.
-
- 4.3.12 Central directory structure:
-
- [central directory header 1]
- .
- .
- .
- [central directory header n]
- [digital signature]
-
- File header:
-
- central file header signature 4 bytes (0x02014b50)
- version made by 2 bytes
- version needed to extract 2 bytes
- general purpose bit flag 2 bytes
- compression method 2 bytes
- last mod file time 2 bytes
- last mod file date 2 bytes
- crc-32 4 bytes
- compressed size 4 bytes
- uncompressed size 4 bytes
- file name length 2 bytes
- extra field length 2 bytes
- file comment length 2 bytes
- disk number start 2 bytes
- internal file attributes 2 bytes
- external file attributes 4 bytes
- relative offset of local header 4 bytes
-
- file name (variable size)
- extra field (variable size)
- file comment (variable size)
-
- 4.3.13 Digital signature:
-
- header signature 4 bytes (0x05054b50)
- size of data 2 bytes
- signature data (variable size)
-
- With the introduction of the Central Directory Encryption
- feature in version 6.2 of this specification, the Central
- Directory Structure MAY be stored both compressed and encrypted.
- Although not required, it is assumed when encrypting the
- Central Directory Structure, that it will be compressed
- for greater storage efficiency. Information on the
- Central Directory Encryption feature can be found in the section
- describing the Strong Encryption Specification. The Digital
- Signature record will be neither compressed nor encrypted.
-
- 4.3.14 Zip64 end of central directory record
-
- zip64 end of central dir
- signature 4 bytes (0x06064b50)
- size of zip64 end of central
- directory record 8 bytes
- version made by 2 bytes
- version needed to extract 2 bytes
- number of this disk 4 bytes
- number of the disk with the
- start of the central directory 4 bytes
- total number of entries in the
- central directory on this disk 8 bytes
- total number of entries in the
- central directory 8 bytes
- size of the central directory 8 bytes
- offset of start of central
- directory with respect to
- the starting disk number 8 bytes
- zip64 extensible data sector (variable size)
-
- 4.3.14.1 The value stored into the "size of zip64 end of central
- directory record" should be the size of the remaining
- record and should not include the leading 12 bytes.
-
- Size = SizeOfFixedFields + SizeOfVariableData - 12.
-
- 4.3.14.2 The above record structure defines Version 1 of the
- zip64 end of central directory record. Version 1 was
- implemented in versions of this specification preceding
- 6.2 in support of the ZIP64 large file feature. The
- introduction of the Central Directory Encryption feature
- implemented in version 6.2 as part of the Strong Encryption
- Specification defines Version 2 of this record structure.
- Refer to the section describing the Strong Encryption
- Specification for details on the version 2 format for
- this record. Refer to the section in this document entitled
- "Incorporating PKWARE Proprietary Technology into Your Product"
- for more information applicable to use of Version 2 of this
- record.
-
- 4.3.14.3 Special purpose data MAY reside in the zip64 extensible
- data sector field following either a V1 or V2 version of this
- record. To ensure identification of this special purpose data
- it must include an identifying header block consisting of the
- following:
-
- Header ID - 2 bytes
- Data Size - 4 bytes
-
- The Header ID field indicates the type of data that is in the
- data block that follows.
-
- Data Size identifies the number of bytes that follow for this
- data block type.
-
- 4.3.14.4 Multiple special purpose data blocks MAY be present.
- Each MUST be preceded by a Header ID and Data Size field. Current
- mappings of Header ID values supported in this field are as
- defined in APPENDIX C.
-
- 4.3.15 Zip64 end of central directory locator
-
- zip64 end of central dir locator
- signature 4 bytes (0x07064b50)
- number of the disk with the
- start of the zip64 end of
- central directory 4 bytes
- relative offset of the zip64
- end of central directory record 8 bytes
- total number of disks 4 bytes
-
- 4.3.16 End of central directory record:
-
- end of central dir signature 4 bytes (0x06054b50)
- number of this disk 2 bytes
- number of the disk with the
- start of the central directory 2 bytes
- total number of entries in the
- central directory on this disk 2 bytes
- total number of entries in
- the central directory 2 bytes
- size of the central directory 4 bytes
- offset of start of central
- directory with respect to
- the starting disk number 4 bytes
- .ZIP file comment length 2 bytes
- .ZIP file comment (variable size)
-
-4.4 Explanation of fields
---------------------------
-
- 4.4.1 General notes on fields
-
- 4.4.1.1 All fields unless otherwise noted are unsigned and stored
- in Intel low-byte:high-byte, low-word:high-word order.
-
- 4.4.1.2 String fields are not null terminated, since the length
- is given explicitly.
-
- 4.4.1.3 The entries in the central directory may not necessarily
- be in the same order that files appear in the .ZIP file.
-
- 4.4.1.4 If one of the fields in the end of central directory
- record is too small to hold required data, the field should be
- set to -1 (0xFFFF or 0xFFFFFFFF) and the ZIP64 format record
- should be created.
-
- 4.4.1.5 The end of central directory record and the Zip64 end
- of central directory locator record MUST reside on the same
- disk when splitting or spanning an archive.
-
- 4.4.2 version made by (2 bytes)
-
- 4.4.2.1 The upper byte indicates the compatibility of the file
- attribute information. If the external file attributes
- are compatible with MS-DOS and can be read by PKZIP for
- DOS version 2.04g then this value will be zero. If these
- attributes are not compatible, then this value will
- identify the host system on which the attributes are
- compatible. Software can use this information to determine
- the line record format for text files etc.
-
- 4.4.2.2 The current mappings are:
-
- 0 - MS-DOS and OS/2 (FAT / VFAT / FAT32 file systems)
- 1 - Amiga 2 - OpenVMS
- 3 - UNIX 4 - VM/CMS
- 5 - Atari ST 6 - OS/2 H.P.F.S.
- 7 - Macintosh 8 - Z-System
- 9 - CP/M 10 - Windows NTFS
- 11 - MVS (OS/390 - Z/OS) 12 - VSE
- 13 - Acorn Risc 14 - VFAT
- 15 - alternate MVS 16 - BeOS
- 17 - Tandem 18 - OS/400
- 19 - OS X (Darwin) 20 thru 255 - unused
-
- 4.4.2.3 The lower byte indicates the ZIP specification version
- (the version of this document) supported by the software
- used to encode the file. The value/10 indicates the major
- version number, and the value mod 10 is the minor version
- number.
-
- 4.4.3 version needed to extract (2 bytes)
-
- 4.4.3.1 The minimum supported ZIP specification version needed
- to extract the file, mapped as above. This value is based on
- the specific format features a ZIP program MUST support to
- be able to extract the file. If multiple features are
- applied to a file, the minimum version MUST be set to the
- feature having the highest value. New features or feature
- changes affecting the published format specification will be
- implemented using higher version numbers than the last
- published value to avoid conflict.
-
- 4.4.3.2 Current minimum feature versions are as defined below:
-
- 1.0 - Default value
- 1.1 - File is a volume label
- 2.0 - File is a folder (directory)
- 2.0 - File is compressed using Deflate compression
- 2.0 - File is encrypted using traditional PKWARE encryption
- 2.1 - File is compressed using Deflate64(tm)
- 2.5 - File is compressed using PKWARE DCL Implode
- 2.7 - File is a patch data set
- 4.5 - File uses ZIP64 format extensions
- 4.6 - File is compressed using BZIP2 compression*
- 5.0 - File is encrypted using DES
- 5.0 - File is encrypted using 3DES
- 5.0 - File is encrypted using original RC2 encryption
- 5.0 - File is encrypted using RC4 encryption
- 5.1 - File is encrypted using AES encryption
- 5.1 - File is encrypted using corrected RC2 encryption**
- 5.2 - File is encrypted using corrected RC2-64 encryption**
- 6.1 - File is encrypted using non-OAEP key wrapping***
- 6.2 - Central directory encryption
- 6.3 - File is compressed using LZMA
- 6.3 - File is compressed using PPMd+
- 6.3 - File is encrypted using Blowfish
- 6.3 - File is encrypted using Twofish
-
- 4.4.3.3 Notes on version needed to extract
-
- * Early 7.x (pre-7.2) versions of PKZIP incorrectly set the
- version needed to extract for BZIP2 compression to be 50
- when it should have been 46.
-
- ** Refer to the section on Strong Encryption Specification
- for additional information regarding RC2 corrections.
-
- *** Certificate encryption using non-OAEP key wrapping is the
- intended mode of operation for all versions beginning with 6.1.
- Support for OAEP key wrapping MUST only be used for
- backward compatibility when sending ZIP files to be opened by
- versions of PKZIP older than 6.1 (5.0 or 6.0).
-
- + Files compressed using PPMd MUST set the version
- needed to extract field to 6.3, however, not all ZIP
- programs enforce this and may be unable to decompress
- data files compressed using PPMd if this value is set.
-
- When using ZIP64 extensions, the corresponding value in the
- zip64 end of central directory record MUST also be set.
- This field should be set appropriately to indicate whether
- Version 1 or Version 2 format is in use.
-
-
- 4.4.4 general purpose bit flag: (2 bytes)
-
- Bit 0: If set, indicates that the file is encrypted.
-
- (For Method 6 - Imploding)
- Bit 1: If the compression method used was type 6,
- Imploding, then this bit, if set, indicates
- an 8K sliding dictionary was used. If clear,
- then a 4K sliding dictionary was used.
-
- Bit 2: If the compression method used was type 6,
- Imploding, then this bit, if set, indicates
- 3 Shannon-Fano trees were used to encode the
- sliding dictionary output. If clear, then 2
- Shannon-Fano trees were used.
-
- (For Methods 8 and 9 - Deflating)
- Bit 2 Bit 1
- 0 0 Normal (-en) compression option was used.
- 0 1 Maximum (-exx/-ex) compression option was used.
- 1 0 Fast (-ef) compression option was used.
- 1 1 Super Fast (-es) compression option was used.
-
- (For Method 14 - LZMA)
- Bit 1: If the compression method used was type 14,
- LZMA, then this bit, if set, indicates
- an end-of-stream (EOS) marker is used to
- mark the end of the compressed data stream.
- If clear, then an EOS marker is not present
- and the compressed data size must be known
- to extract.
-
- Note: Bits 1 and 2 are undefined if the compression
- method is any other.
-
- Bit 3: If this bit is set, the fields crc-32, compressed
- size and uncompressed size are set to zero in the
- local header. The correct values are put in the
- data descriptor immediately following the compressed
- data. (Note: PKZIP version 2.04g for DOS only
- recognizes this bit for method 8 compression, newer
- versions of PKZIP recognize this bit for any
- compression method.)
-
- Bit 4: Reserved for use with method 8, for enhanced
- deflating.
-
- Bit 5: If this bit is set, this indicates that the file is
- compressed patched data. (Note: Requires PKZIP
- version 2.70 or greater)
-
- Bit 6: Strong encryption. If this bit is set, you MUST
- set the version needed to extract value to at least
- 50 and you MUST also set bit 0. If AES encryption
- is used, the version needed to extract value MUST
- be at least 51. See the section describing the Strong
- Encryption Specification for details. Refer to the
- section in this document entitled "Incorporating PKWARE
- Proprietary Technology into Your Product" for more
- information.
-
- Bit 7: Currently unused.
-
- Bit 8: Currently unused.
-
- Bit 9: Currently unused.
-
- Bit 10: Currently unused.
-
- Bit 11: Language encoding flag (EFS). If this bit is set,
- the filename and comment fields for this file
- MUST be encoded using UTF-8. (see APPENDIX D)
-
- Bit 12: Reserved by PKWARE for enhanced compression.
-
- Bit 13: Set when encrypting the Central Directory to indicate
- selected data values in the Local Header are masked to
- hide their actual values. See the section describing
- the Strong Encryption Specification for details. Refer
- to the section in this document entitled "Incorporating
- PKWARE Proprietary Technology into Your Product" for
- more information.
-
- Bit 14: Reserved by PKWARE.
-
- Bit 15: Reserved by PKWARE.
-
- 4.4.5 compression method: (2 bytes)
-
- 0 - The file is stored (no compression)
- 1 - The file is Shrunk
- 2 - The file is Reduced with compression factor 1
- 3 - The file is Reduced with compression factor 2
- 4 - The file is Reduced with compression factor 3
- 5 - The file is Reduced with compression factor 4
- 6 - The file is Imploded
- 7 - Reserved for Tokenizing compression algorithm
- 8 - The file is Deflated
- 9 - Enhanced Deflating using Deflate64(tm)
- 10 - PKWARE Data Compression Library Imploding (old IBM TERSE)
- 11 - Reserved by PKWARE
- 12 - File is compressed using BZIP2 algorithm
- 13 - Reserved by PKWARE
- 14 - LZMA (EFS)
- 15 - Reserved by PKWARE
- 16 - Reserved by PKWARE
- 17 - Reserved by PKWARE
- 18 - File is compressed using IBM TERSE (new)
- 19 - IBM LZ77 z Architecture (PFS)
- 97 - WavPack compressed data
- 98 - PPMd version I, Rev 1
-
-
- 4.4.6 date and time fields: (2 bytes each)
-
- The date and time are encoded in standard MS-DOS format.
- If input came from standard input, the date and time are
- those at which compression was started for this data.
- If encrypting the central directory and general purpose bit
- flag 13 is set indicating masking, the value stored in the
- Local Header will be zero.
-
- 4.4.7 CRC-32: (4 bytes)
-
- The CRC-32 algorithm was generously contributed by
- David Schwaderer and can be found in his excellent
- book "C Programmers Guide to NetBIOS" published by
- Howard W. Sams & Co. Inc. The 'magic number' for
- the CRC is 0xdebb20e3. The proper CRC pre and post
- conditioning is used, meaning that the CRC register
- is pre-conditioned with all ones (a starting value
- of 0xffffffff) and the value is post-conditioned by
- taking the one's complement of the CRC residual.
- If bit 3 of the general purpose flag is set, this
- field is set to zero in the local header and the correct
- value is put in the data descriptor and in the central
- directory. When encrypting the central directory, if the
- local header is not in ZIP64 format and general purpose
- bit flag 13 is set indicating masking, the value stored
- in the Local Header will be zero.
-
- 4.4.8 compressed size: (4 bytes)
- 4.4.9 uncompressed size: (4 bytes)
-
- The size of the file compressed (4.4.8) and uncompressed,
- (4.4.9) respectively. When a decryption header is present it
- will be placed in front of the file data and the value of the
- compressed file size will include the bytes of the decryption
- header. If bit 3 of the general purpose bit flag is set,
- these fields are set to zero in the local header and the
- correct values are put in the data descriptor and
- in the central directory. If an archive is in ZIP64 format
- and the value in this field is 0xFFFFFFFF, the size will be
- in the corresponding 8 byte ZIP64 extended information
- extra field. When encrypting the central directory, if the
- local header is not in ZIP64 format and general purpose bit
- flag 13 is set indicating masking, the value stored for the
- uncompressed size in the Local Header will be zero.
-
- 4.4.10 file name length: (2 bytes)
- 4.4.11 extra field length: (2 bytes)
- 4.4.12 file comment length: (2 bytes)
-
- The length of the file name, extra field, and comment
- fields respectively. The combined length of any
- directory record and these three fields should not
- generally exceed 65,535 bytes. If input came from standard
- input, the file name length is set to zero.
-
-
- 4.4.13 disk number start: (2 bytes)
-
- The number of the disk on which this file begins. If an
- archive is in ZIP64 format and the value in this field is
- 0xFFFF, the size will be in the corresponding 4 byte zip64
- extended information extra field.
-
- 4.4.14 internal file attributes: (2 bytes)
-
- Bits 1 and 2 are reserved for use by PKWARE.
-
- 4.4.14.1 The lowest bit of this field indicates, if set,
- that the file is apparently an ASCII or text file. If not
- set, that the file apparently contains binary data.
- The remaining bits are unused in version 1.0.
-
- 4.4.14.2 The 0x0002 bit of this field indicates, if set, that
- a 4 byte variable record length control field precedes each
- logical record indicating the length of the record. The
- record length control field is stored in little-endian byte
- order. This flag is independent of text control characters,
- and if used in conjunction with text data, includes any
- control characters in the total length of the record. This
- value is provided for mainframe data transfer support.
-
- 4.4.15 external file attributes: (4 bytes)
-
- The mapping of the external attributes is
- host-system dependent (see 'version made by'). For
- MS-DOS, the low order byte is the MS-DOS directory
- attribute byte. If input came from standard input, this
- field is set to zero.
-
- 4.4.16 relative offset of local header: (4 bytes)
-
- This is the offset from the start of the first disk on
- which this file appears, to where the local header should
- be found. If an archive is in ZIP64 format and the value
- in this field is 0xFFFFFFFF, the size will be in the
- corresponding 8 byte zip64 extended information extra field.
-
- 4.4.17 file name: (Variable)
-
- 4.4.17.1 The name of the file, with optional relative path.
- The path stored MUST not contain a drive or
- device letter, or a leading slash. All slashes
- MUST be forward slashes '/' as opposed to
- backwards slashes '\' for compatibility with Amiga
- and UNIX file systems etc. If input came from standard
- input, there is no file name field.
-
- 4.4.17.2 If using the Central Directory Encryption Feature and
- general purpose bit flag 13 is set indicating masking, the file
- name stored in the Local Header will not be the actual file name.
- A masking value consisting of a unique hexadecimal value will
- be stored. This value will be sequentially incremented for each
- file in the archive. See the section on the Strong Encryption
- Specification for details on retrieving the encrypted file name.
- Refer to the section in this document entitled "Incorporating PKWARE
- Proprietary Technology into Your Product" for more information.
-
-
- 4.4.18 file comment: (Variable)
-
- The comment for this file.
-
- 4.4.19 number of this disk: (2 bytes)
-
- The number of this disk, which contains central
- directory end record. If an archive is in ZIP64 format
- and the value in this field is 0xFFFF, the size will
- be in the corresponding 4 byte zip64 end of central
- directory field.
-
-
- 4.4.20 number of the disk with the start of the central
- directory: (2 bytes)
-
- The number of the disk on which the central
- directory starts. If an archive is in ZIP64 format
- and the value in this field is 0xFFFF, the size will
- be in the corresponding 4 byte zip64 end of central
- directory field.
-
- 4.4.21 total number of entries in the central dir on
- this disk: (2 bytes)
-
- The number of central directory entries on this disk.
- If an archive is in ZIP64 format and the value in
- this field is 0xFFFF, the size will be in the
- corresponding 8 byte zip64 end of central
- directory field.
-
- 4.4.22 total number of entries in the central dir: (2 bytes)
-
- The total number of files in the .ZIP file. If an
- archive is in ZIP64 format and the value in this field
- is 0xFFFF, the size will be in the corresponding 8 byte
- zip64 end of central directory field.
-
- 4.4.23 size of the central directory: (4 bytes)
-
- The size (in bytes) of the entire central directory.
- If an archive is in ZIP64 format and the value in
- this field is 0xFFFFFFFF, the size will be in the
- corresponding 8 byte zip64 end of central
- directory field.
-
- 4.4.24 offset of start of central directory with respect to
- the starting disk number: (4 bytes)
-
- Offset of the start of the central directory on the
- disk on which the central directory starts. If an
- archive is in ZIP64 format and the value in this
- field is 0xFFFFFFFF, the size will be in the
- corresponding 8 byte zip64 end of central
- directory field.
-
- 4.4.25 .ZIP file comment length: (2 bytes)
-
- The length of the comment for this .ZIP file.
-
- 4.4.26 .ZIP file comment: (Variable)
-
- The comment for this .ZIP file. ZIP file comment data
- is stored unsecured. No encryption or data authentication
- is applied to this area at this time. Confidential information
- should not be stored in this section.
-
- 4.4.27 zip64 extensible data sector (variable size)
-
- (currently reserved for use by PKWARE)
-
-
- 4.4.28 extra field: (Variable)
-
- This SHOULD be used for storage expansion. If additional
- information needs to be stored within a ZIP file for special
- application or platform needs, it SHOULD be stored here.
- Programs supporting earlier versions of this specification can
- then safely skip the file, and find the next file or header.
- This field will be 0 length in version 1.0.
-
- Existing extra fields are defined in the section
- Extensible data fields that follows.
-
-4.5 Extensible data fields
---------------------------
-
- 4.5.1 In order to allow different programs and different types
- of information to be stored in the 'extra' field in .ZIP
- files, the following structure MUST be used for all
- programs storing data in this field:
-
- header1+data1 + header2+data2 . . .
-
- Each header should consist of:
-
- Header ID - 2 bytes
- Data Size - 2 bytes
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- The Header ID field indicates the type of data that is in
- the following data block.
-
- Header IDs of 0 thru 31 are reserved for use by PKWARE.
- The remaining IDs can be used by third party vendors for
- proprietary usage.
-
- 4.5.2 The current Header ID mappings defined by PKWARE are:
-
- 0x0001 Zip64 extended information extra field
- 0x0007 AV Info
- 0x0008 Reserved for extended language encoding data (PFS)
- (see APPENDIX D)
- 0x0009 OS/2
- 0x000a NTFS
- 0x000c OpenVMS
- 0x000d UNIX
- 0x000e Reserved for file stream and fork descriptors
- 0x000f Patch Descriptor
- 0x0014 PKCS#7 Store for X.509 Certificates
- 0x0015 X.509 Certificate ID and Signature for
- individual file
- 0x0016 X.509 Certificate ID for Central Directory
- 0x0017 Strong Encryption Header
- 0x0018 Record Management Controls
- 0x0019 PKCS#7 Encryption Recipient Certificate List
- 0x0065 IBM S/390 (Z390), AS/400 (I400) attributes
- - uncompressed
- 0x0066 Reserved for IBM S/390 (Z390), AS/400 (I400)
- attributes - compressed
- 0x4690 POSZIP 4690 (reserved)
-
-
- 4.5.3 -Zip64 Extended Information Extra Field (0x0001):
-
- The following is the layout of the zip64 extended
- information "extra" block. If one of the size or
- offset fields in the Local or Central directory
- record is too small to hold the required data,
- a Zip64 extended information record is created.
- The order of the fields in the zip64 extended
- information record is fixed, but the fields MUST
- only appear if the corresponding Local or Central
- directory record field is set to 0xFFFF or 0xFFFFFFFF.
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(ZIP64) 0x0001 2 bytes Tag for this "extra" block type
- Size 2 bytes Size of this "extra" block
- Original
- Size 8 bytes Original uncompressed file size
- Compressed
- Size 8 bytes Size of compressed data
- Relative Header
- Offset 8 bytes Offset of local header record
- Disk Start
- Number 4 bytes Number of the disk on which
- this file starts
-
- This entry in the Local header MUST include BOTH original
- and compressed file size fields. If encrypting the
- central directory and bit 13 of the general purpose bit
- flag is set indicating masking, the value stored in the
- Local Header for the original file size will be zero.
-
-
- 4.5.4 -OS/2 Extra Field (0x0009):
-
- The following is the layout of the OS/2 attributes "extra"
- block. (Last Revision 09/05/95)
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(OS/2) 0x0009 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size for the following data block
- BSize 4 bytes Uncompressed Block Size
- CType 2 bytes Compression type
- EACRC 4 bytes CRC value for uncompress block
- (var) variable Compressed block
-
- The OS/2 extended attribute structure (FEA2LIST) is
- compressed and then stored in its entirety within this
- structure. There will only ever be one "block" of data in
- VarFields[].
-
- 4.5.5 -NTFS Extra Field (0x000a):
-
- The following is the layout of the NTFS attributes
- "extra" block. (Note: At this time the Mtime, Atime
- and Ctime values MAY be used on any WIN32 system.)
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(NTFS) 0x000a 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of the total "extra" block
- Reserved 4 bytes Reserved for future use
- Tag1 2 bytes NTFS attribute tag value #1
- Size1 2 bytes Size of attribute #1, in bytes
- (var) Size1 Attribute #1 data
- .
- .
- .
- TagN 2 bytes NTFS attribute tag value #N
- SizeN 2 bytes Size of attribute #N, in bytes
- (var) SizeN Attribute #N data
-
- For NTFS, values for Tag1 through TagN are as follows:
- (currently only one set of attributes is defined for NTFS)
-
- Tag Size Description
- ----- ---- -----------
- 0x0001 2 bytes Tag for attribute #1
- Size1 2 bytes Size of attribute #1, in bytes
- Mtime 8 bytes File last modification time
- Atime 8 bytes File last access time
- Ctime 8 bytes File creation time
-
- 4.5.6 -OpenVMS Extra Field (0x000c):
-
- The following is the layout of the OpenVMS attributes
- "extra" block.
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
- (VMS) 0x000c 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of the total "extra" block
- CRC 4 bytes 32-bit CRC for remainder of the block
- Tag1 2 bytes OpenVMS attribute tag value #1
- Size1 2 bytes Size of attribute #1, in bytes
- (var) Size1 Attribute #1 data
- .
- .
- .
- TagN 2 bytes OpenVMS attribute tag value #N
- SizeN 2 bytes Size of attribute #N, in bytes
- (var) SizeN Attribute #N data
-
- OpenVMS Extra Field Rules:
-
- 4.5.6.1. There will be one or more attributes present, which
- will each be preceded by the above TagX & SizeX values.
- These values are identical to the ATR$C_XXXX and ATR$S_XXXX
- constants which are defined in ATR.H under OpenVMS C. Neither
- of these values will ever be zero.
-
- 4.5.6.2. No word alignment or padding is performed.
-
- 4.5.6.3. A well-behaved PKZIP/OpenVMS program should never produce
- more than one sub-block with the same TagX value. Also, there will
- never be more than one "extra" block of type 0x000c in a particular
- directory record.
-
- 4.5.7 -UNIX Extra Field (0x000d):
-
- The following is the layout of the UNIX "extra" block.
- Note: all fields are stored in Intel low-byte/high-byte
- order.
-
- Value Size Description
- ----- ---- -----------
-(UNIX) 0x000d 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size for the following data block
- Atime 4 bytes File last access time
- Mtime 4 bytes File last modification time
- Uid 2 bytes File user ID
- Gid 2 bytes File group ID
- (var) variable Variable length data field
-
- The variable length data field will contain file type
- specific data. Currently the only values allowed are
- the original "linked to" file names for hard or symbolic
- links, and the major and minor device node numbers for
- character and block device nodes. Since device nodes
- cannot be either symbolic or hard links, only one set of
- variable length data is stored. Link files will have the
- name of the original file stored. This name is NOT NULL
- terminated. Its size can be determined by checking TSize -
- 12. Device entries will have eight bytes stored as two 4
- byte entries (in little endian format). The first entry
- will be the major device number, and the second the minor
- device number.
-
- 4.5.8 -PATCH Descriptor Extra Field (0x000f):
-
- 4.5.8.1 The following is the layout of the Patch Descriptor
- "extra" block.
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(Patch) 0x000f 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of the total "extra" block
- Version 2 bytes Version of the descriptor
- Flags 4 bytes Actions and reactions (see below)
- OldSize 4 bytes Size of the file about to be patched
- OldCRC 4 bytes 32-bit CRC of the file to be patched
- NewSize 4 bytes Size of the resulting file
- NewCRC 4 bytes 32-bit CRC of the resulting file
-
- 4.5.8.2 Actions and reactions
-
- Bits Description
- ---- ----------------
- 0 Use for auto detection
- 1 Treat as a self-patch
- 2-3 RESERVED
- 4-5 Action (see below)
- 6-7 RESERVED
- 8-9 Reaction (see below) to absent file
- 10-11 Reaction (see below) to newer file
- 12-13 Reaction (see below) to unknown file
- 14-15 RESERVED
- 16-31 RESERVED
-
- 4.5.8.2.1 Actions
-
- Action Value
- ------ -----
- none 0
- add 1
- delete 2
- patch 3
-
- 4.5.8.2.2 Reactions
-
- Reaction Value
- -------- -----
- ask 0
- skip 1
- ignore 2
- fail 3
-
- 4.5.8.3 Patch support is provided by PKPatchMaker(tm) technology
- and is covered under U.S. Patents and Patents Pending. The use or
- implementation in a product of certain technological aspects set
- forth in the current APPNOTE, including those with regard to
- strong encryption or patching requires a license from PKWARE.
- Refer to the section in this document entitled "Incorporating
- PKWARE Proprietary Technology into Your Product" for more
- information.
-
- 4.5.9 -PKCS#7 Store for X.509 Certificates (0x0014):
-
- This field MUST contain information about each of the certificates
- files may be signed with. When the Central Directory Encryption
- feature is enabled for a ZIP file, this record will appear in
- the Archive Extra Data Record, otherwise it will appear in the
- first central directory record and will be ignored in any
- other record.
-
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(Store) 0x0014 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of the store data
- TData TSize Data about the store
-
-
- 4.5.10 -X.509 Certificate ID and Signature for individual file (0x0015):
-
- This field contains the information about which certificate in
- the PKCS#7 store was used to sign a particular file. It also
- contains the signature data. This field can appear multiple
- times, but can only appear once per certificate.
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(CID) 0x0015 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of data that follows
- TData TSize Signature Data
-
- 4.5.11 -X.509 Certificate ID and Signature for central directory (0x0016):
-
- This field contains the information about which certificate in
- the PKCS#7 store was used to sign the central directory structure.
- When the Central Directory Encryption feature is enabled for a
- ZIP file, this record will appear in the Archive Extra Data Record,
- otherwise it will appear in the first central directory record.
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(CDID) 0x0016 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of data that follows
- TData TSize Data
-
- 4.5.12 -Strong Encryption Header (0x0017):
-
- Value Size Description
- ----- ---- -----------
- 0x0017 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of data that follows
- Format 2 bytes Format definition for this record
- AlgID 2 bytes Encryption algorithm identifier
- Bitlen 2 bytes Bit length of encryption key
- Flags 2 bytes Processing flags
- CertData TSize-8 Certificate decryption extra field data
- (refer to the explanation for CertData
- in the section describing the
- Certificate Processing Method under
- the Strong Encryption Specification)
-
- See the section describing the Strong Encryption Specification
- for details. Refer to the section in this document entitled
- "Incorporating PKWARE Proprietary Technology into Your Product"
- for more information.
-
- 4.5.13 -Record Management Controls (0x0018):
-
- Value Size Description
- ----- ---- -----------
-(Rec-CTL) 0x0018 2 bytes Tag for this "extra" block type
- CSize 2 bytes Size of total extra block data
- Tag1 2 bytes Record control attribute 1
- Size1 2 bytes Size of attribute 1, in bytes
- Data1 Size1 Attribute 1 data
- .
- .
- .
- TagN 2 bytes Record control attribute N
- SizeN 2 bytes Size of attribute N, in bytes
- DataN SizeN Attribute N data
-
-
- 4.5.14 -PKCS#7 Encryption Recipient Certificate List (0x0019):
-
- This field MAY contain information about each of the certificates
- used in encryption processing and it can be used to identify who is
- allowed to decrypt encrypted files. This field should only appear
- in the archive extra data record. This field is not required and
- serves only to aid archive modifications by preserving public
- encryption key data. Individual security requirements may dictate
- that this data be omitted to deter information exposure.
-
- Note: all fields stored in Intel low-byte/high-byte order.
-
- Value Size Description
- ----- ---- -----------
-(CStore) 0x0019 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size of the store data
- TData TSize Data about the store
-
- TData:
-
- Value Size Description
- ----- ---- -----------
- Version 2 bytes Format version number - must 0x0001 at this time
- CStore (var) PKCS#7 data blob
-
- See the section describing the Strong Encryption Specification
- for details. Refer to the section in this document entitled
- "Incorporating PKWARE Proprietary Technology into Your Product"
- for more information.
-
- 4.5.15 -MVS Extra Field (0x0065):
-
- The following is the layout of the MVS "extra" block.
- Note: Some fields are stored in Big Endian format.
- All text is in EBCDIC format unless otherwise specified.
-
- Value Size Description
- ----- ---- -----------
-(MVS) 0x0065 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size for the following data block
- ID 4 bytes EBCDIC "Z390" 0xE9F3F9F0 or
- "T4MV" for TargetFour
- (var) TSize-4 Attribute data (see APPENDIX B)
-
-
- 4.5.16 -OS/400 Extra Field (0x0065):
-
- The following is the layout of the OS/400 "extra" block.
- Note: Some fields are stored in Big Endian format.
- All text is in EBCDIC format unless otherwise specified.
-
- Value Size Description
- ----- ---- -----------
-(OS400) 0x0065 2 bytes Tag for this "extra" block type
- TSize 2 bytes Size for the following data block
- ID 4 bytes EBCDIC "I400" 0xC9F4F0F0 or
- "T4MV" for TargetFour
- (var) TSize-4 Attribute data (see APPENDIX A)
-
-4.6 Third Party Mappings
-------------------------
-
- 4.6.1 Third party mappings commonly used are:
-
- 0x07c8 Macintosh
- 0x2605 ZipIt Macintosh
- 0x2705 ZipIt Macintosh 1.3.5+
- 0x2805 ZipIt Macintosh 1.3.5+
- 0x334d Info-ZIP Macintosh
- 0x4341 Acorn/SparkFS
- 0x4453 Windows NT security descriptor (binary ACL)
- 0x4704 VM/CMS
- 0x470f MVS
- 0x4b46 FWKCS MD5 (see below)
- 0x4c41 OS/2 access control list (text ACL)
- 0x4d49 Info-ZIP OpenVMS
- 0x4f4c Xceed original location extra field
- 0x5356 AOS/VS (ACL)
- 0x5455 extended timestamp
- 0x554e Xceed unicode extra field
- 0x5855 Info-ZIP UNIX (original, also OS/2, NT, etc)
- 0x6375 Info-ZIP Unicode Comment Extra Field
- 0x6542 BeOS/BeBox
- 0x7075 Info-ZIP Unicode Path Extra Field
- 0x756e ASi UNIX
- 0x7855 Info-ZIP UNIX (new)
- 0xa220 Microsoft Open Packaging Growth Hint
- 0xfd4a SMS/QDOS
-
- Detailed descriptions of Extra Fields defined by third
- party mappings will be documented as information on
- these data structures is made available to PKWARE.
- PKWARE does not guarantee the accuracy of any published
- third party data.
-
- 4.6.2 Third-party Extra Fields must include a Header ID using
- the format defined in the section of this document
- titled Extensible Data Fields (section 4.5).
-
- The Data Size field indicates the size of the following
- data block. Programs can use this value to skip to the
- next header block, passing over any data blocks that are
- not of interest.
-
- Note: As stated above, the size of the entire .ZIP file
- header, including the file name, comment, and extra
- field should not exceed 64K in size.
-
- 4.6.3 In case two different programs should appropriate the same
- Header ID value, it is strongly recommended that each
- program SHOULD place a unique signature of at least two bytes in
- size (and preferably 4 bytes or bigger) at the start of
- each data area. Every program SHOULD verify that its
- unique signature is present, in addition to the Header ID
- value being correct, before assuming that it is a block of
- known type.
-
- Third-party Mappings:
-
- 4.6.4 -ZipIt Macintosh Extra Field (long) (0x2605):
-
- The following is the layout of the ZipIt extra block
- for Macintosh. The local-header and central-header versions
- are identical. This block must be present if the file is
- stored MacBinary-encoded and it should not be used if the file
- is not stored MacBinary-encoded.
-
- Value Size Description
- ----- ---- -----------
- (Mac2) 0x2605 Short tag for this extra block type
- TSize Short total data size for this block
- "ZPIT" beLong extra-field signature
- FnLen Byte length of FileName
- FileName variable full Macintosh filename
- FileType Byte[4] four-byte Mac file type string
- Creator Byte[4] four-byte Mac creator string
-
-
- 4.6.5 -ZipIt Macintosh Extra Field (short, for files) (0x2705):
-
- The following is the layout of a shortened variant of the
- ZipIt extra block for Macintosh (without "full name" entry).
- This variant is used by ZipIt 1.3.5 and newer for entries of
- files (not directories) that do not have a MacBinary encoded
- file. The local-header and central-header versions are identical.
-
- Value Size Description
- ----- ---- -----------
- (Mac2b) 0x2705 Short tag for this extra block type
- TSize Short total data size for this block (12)
- "ZPIT" beLong extra-field signature
- FileType Byte[4] four-byte Mac file type string
- Creator Byte[4] four-byte Mac creator string
- fdFlags beShort attributes from FInfo.frFlags,
- may be omitted
- 0x0000 beShort reserved, may be omitted
-
-
- 4.6.6 -ZipIt Macintosh Extra Field (short, for directories) (0x2805):
-
- The following is the layout of a shortened variant of the
- ZipIt extra block for Macintosh used only for directory
- entries. This variant is used by ZipIt 1.3.5 and newer to
- save some optional Mac-specific information about directories.
- The local-header and central-header versions are identical.
-
- Value Size Description
- ----- ---- -----------
- (Mac2c) 0x2805 Short tag for this extra block type
- TSize Short total data size for this block (12)
- "ZPIT" beLong extra-field signature
- frFlags beShort attributes from DInfo.frFlags, may
- be omitted
- View beShort ZipIt view flag, may be omitted
-
-
- The View field specifies ZipIt-internal settings as follows:
-
- Bits of the Flags:
- bit 0 if set, the folder is shown expanded (open)
- when the archive contents are viewed in ZipIt.
- bits 1-15 reserved, zero;
-
-
- 4.6.7 -FWKCS MD5 Extra Field (0x4b46):
-
- The FWKCS Contents_Signature System, used in
- automatically identifying files independent of file name,
- optionally adds and uses an extra field to support the
- rapid creation of an enhanced contents_signature:
-
- Header ID = 0x4b46
- Data Size = 0x0013
- Preface = 'M','D','5'
- followed by 16 bytes containing the uncompressed file's
- 128_bit MD5 hash(1), low byte first.
-
- When FWKCS revises a .ZIP file central directory to add
- this extra field for a file, it also replaces the
- central directory entry for that file's uncompressed
- file length with a measured value.
-
- FWKCS provides an option to strip this extra field, if
- present, from a .ZIP file central directory. In adding
- this extra field, FWKCS preserves .ZIP file Authenticity
- Verification; if stripping this extra field, FWKCS
- preserves all versions of AV through PKZIP version 2.04g.
-
- FWKCS, and FWKCS Contents_Signature System, are
- trademarks of Frederick W. Kantor.
-
- (1) R. Rivest, RFC1321.TXT, MIT Laboratory for Computer
- Science and RSA Data Security, Inc., April 1992.
- ll.76-77: "The MD5 algorithm is being placed in the
- public domain for review and possible adoption as a
- standard."
-
-
- 4.6.8 -Info-ZIP Unicode Comment Extra Field (0x6375):
-
- Stores the UTF-8 version of the file comment as stored in the
- central directory header. (Last Revision 20070912)
-
- Value Size Description
- ----- ---- -----------
- (UCom) 0x6375 Short tag for this extra block type ("uc")
- TSize Short total data size for this block
- Version 1 byte version of this extra field, currently 1
- ComCRC32 4 bytes Comment Field CRC32 Checksum
- UnicodeCom Variable UTF-8 version of the entry comment
-
- Currently Version is set to the number 1. If there is a need
- to change this field, the version will be incremented. Changes
- may not be backward compatible so this extra field should not be
- used if the version is not recognized.
-
- The ComCRC32 is the standard zip CRC32 checksum of the File Comment
- field in the central directory header. This is used to verify that
- the comment field has not changed since the Unicode Comment extra field
- was created. This can happen if a utility changes the File Comment
- field but does not update the UTF-8 Comment extra field. If the CRC
- check fails, this Unicode Comment extra field should be ignored and
- the File Comment field in the header should be used instead.
-
- The UnicodeCom field is the UTF-8 version of the File Comment field
- in the header. As UnicodeCom is defined to be UTF-8, no UTF-8 byte
- order mark (BOM) is used. The length of this field is determined by
- subtracting the size of the previous fields from TSize. If both the
- File Name and Comment fields are UTF-8, the new General Purpose Bit
- Flag, bit 11 (Language encoding flag (EFS)), can be used to indicate
- both the header File Name and Comment fields are UTF-8 and, in this
- case, the Unicode Path and Unicode Comment extra fields are not
- needed and should not be created. Note that, for backward
- compatibility, bit 11 should only be used if the native character set
- of the paths and comments being zipped up are already in UTF-8. It is
- expected that the same file comment storage method, either general
- purpose bit 11 or extra fields, be used in both the Local and Central
- Directory Header for a file.
-
-
- 4.6.9 -Info-ZIP Unicode Path Extra Field (0x7075):
-
- Stores the UTF-8 version of the file name field as stored in the
- local header and central directory header. (Last Revision 20070912)
-
- Value Size Description
- ----- ---- -----------
- (UPath) 0x7075 Short tag for this extra block type ("up")
- TSize Short total data size for this block
- Version 1 byte version of this extra field, currently 1
- NameCRC32 4 bytes File Name Field CRC32 Checksum
- UnicodeName Variable UTF-8 version of the entry File Name
-
- Currently Version is set to the number 1. If there is a need
- to change this field, the version will be incremented. Changes
- may not be backward compatible so this extra field should not be
- used if the version is not recognized.
-
- The NameCRC32 is the standard zip CRC32 checksum of the File Name
- field in the header. This is used to verify that the header
- File Name field has not changed since the Unicode Path extra field
- was created. This can happen if a utility renames the File Name but
- does not update the UTF-8 path extra field. If the CRC check fails,
- this UTF-8 Path Extra Field should be ignored and the File Name field
- in the header should be used instead.
-
- The UnicodeName is the UTF-8 version of the contents of the File Name
- field in the header. As UnicodeName is defined to be UTF-8, no UTF-8
- byte order mark (BOM) is used. The length of this field is determined
- by subtracting the size of the previous fields from TSize. If both
- the File Name and Comment fields are UTF-8, the new General Purpose
- Bit Flag, bit 11 (Language encoding flag (EFS)), can be used to
- indicate that both the header File Name and Comment fields are UTF-8
- and, in this case, the Unicode Path and Unicode Comment extra fields
- are not needed and should not be created. Note that, for backward
- compatibility, bit 11 should only be used if the native character set
- of the paths and comments being zipped up are already in UTF-8. It is
- expected that the same file name storage method, either general
- purpose bit 11 or extra fields, be used in both the Local and Central
- Directory Header for a file.
-
-
- 4.6.10 -Microsoft Open Packaging Growth Hint (0xa220):
-
- Value Size Description
- ----- ---- -----------
- 0xa220 Short tag for this extra block type
- TSize Short size of Sig + PadVal + Padding
- Sig Short verification signature (A028)
- PadVal Short Initial padding value
- Padding variable filled with NULL characters
-
-4.7 Manifest Files
-------------------
-
- 4.7.1 Applications using ZIP files may have a need for additional
- information that must be included with the files placed into
- a ZIP file. Application specific information that cannot be
- stored using the defined ZIP storage records SHOULD be stored
- using the extensible Extra Field convention defined in this
- document. However, some applications may use a manifest
- file as a means for storing additional information. One
- example is the META-INF/MANIFEST.MF file used in ZIP formatted
- files having the .JAR extension (JAR files).
-
- 4.7.2 A manifest file is a file created for the application process
- that requires this information. A manifest file MAY be of any
- file type required by the defining application process. It is
- placed within the same ZIP file as files to which this information
- applies. By convention, this file is typically the first file placed
- into the ZIP file and it may include a defined directory path.
-
- 4.7.3 Manifest files may be compressed or encrypted as needed for
- application processing of the files inside the ZIP files.
-
- Manifest files are outside of the scope of this specification.
-
-
-5.0 Explanation of compression methods
---------------------------------------
-
-
-5.1 UnShrinking - Method 1
---------------------------
-
- 5.1.1 Shrinking is a Dynamic Ziv-Lempel-Welch compression algorithm
- with partial clearing. The initial code size is 9 bits, and the
- maximum code size is 13 bits. Shrinking differs from conventional
- Dynamic Ziv-Lempel-Welch implementations in several respects:
-
- 5.1.2 The code size is controlled by the compressor, and is
- not automatically increased when codes larger than the current
- code size are created (but not necessarily used). When
- the decompressor encounters the code sequence 256
- (decimal) followed by 1, it should increase the code size
- read from the input stream to the next bit size. No
- blocking of the codes is performed, so the next code at
- the increased size should be read from the input stream
- immediately after where the previous code at the smaller
- bit size was read. Again, the decompressor should not
- increase the code size used until the sequence 256,1 is
- encountered.
-
- 5.1.3 When the table becomes full, total clearing is not
- performed. Rather, when the compressor emits the code
- sequence 256,2 (decimal), the decompressor should clear
- all leaf nodes from the Ziv-Lempel tree, and continue to
- use the current code size. The nodes that are cleared
- from the Ziv-Lempel tree are then re-used, with the lowest
- code value re-used first, and the highest code value
- re-used last. The compressor can emit the sequence 256,2
- at any time.
-
-5.2 Expanding - Methods 2-5
----------------------------
-
- 5.2.1 The Reducing algorithm is actually a combination of two
- distinct algorithms. The first algorithm compresses repeated
- byte sequences, and the second algorithm takes the compressed
- stream from the first algorithm and applies a probabilistic
- compression method.
-
- 5.2.2 The probabilistic compression stores an array of 'follower
- sets' S(j), for j=0 to 255, corresponding to each possible
- ASCII character. Each set contains between 0 and 32
- characters, to be denoted as S(j)[0],...,S(j)[m], where m<32.
- The sets are stored at the beginning of the data area for a
- Reduced file, in reverse order, with S(255) first, and S(0)
- last.
-
- 5.2.3 The sets are encoded as { N(j), S(j)[0],...,S(j)[N(j)-1] },
- where N(j) is the size of set S(j). N(j) can be 0, in which
- case the follower set for S(j) is empty. Each N(j) value is
- encoded in 6 bits, followed by N(j) eight bit character values
- corresponding to S(j)[0] to S(j)[N(j)-1] respectively. If
- N(j) is 0, then no values for S(j) are stored, and the value
- for N(j-1) immediately follows.
-
- 5.2.4 Immediately after the follower sets, is the compressed data
- stream. The compressed data stream can be interpreted for the
- probabilistic decompression as follows:
-
- let Last-Character <- 0.
- loop until done
- if the follower set S(Last-Character) is empty then
- read 8 bits from the input stream, and copy this
- value to the output stream.
- otherwise if the follower set S(Last-Character) is non-empty then
- read 1 bit from the input stream.
- if this bit is not zero then
- read 8 bits from the input stream, and copy this
- value to the output stream.
- otherwise if this bit is zero then
- read B(N(Last-Character)) bits from the input
- stream, and assign this value to I.
- Copy the value of S(Last-Character)[I] to the
- output stream.
-
- assign the last value placed on the output stream to
- Last-Character.
- end loop
-
- B(N(j)) is defined as the minimal number of bits required to
- encode the value N(j)-1.
-
- 5.2.5 The decompressed stream from above can then be expanded to
- re-create the original file as follows:
-
- let State <- 0.
-
- loop until done
- read 8 bits from the input stream into C.
- case State of
- 0: if C is not equal to DLE (144 decimal) then
- copy C to the output stream.
- otherwise if C is equal to DLE then
- let State <- 1.
-
- 1: if C is non-zero then
- let V <- C.
- let Len <- L(V)
- let State <- F(Len).
- otherwise if C is zero then
- copy the value 144 (decimal) to the output stream.
- let State <- 0
-
- 2: let Len <- Len + C
- let State <- 3.
-
- 3: move backwards D(V,C) bytes in the output stream
- (if this position is before the start of the output
- stream, then assume that all the data before the
- start of the output stream is filled with zeros).
- copy Len+3 bytes from this position to the output stream.
- let State <- 0.
- end case
- end loop
-
- The functions F,L, and D are dependent on the 'compression
- factor', 1 through 4, and are defined as follows:
-
- For compression factor 1:
- L(X) equals the lower 7 bits of X.
- F(X) equals 2 if X equals 127 otherwise F(X) equals 3.
- D(X,Y) equals the (upper 1 bit of X) * 256 + Y + 1.
- For compression factor 2:
- L(X) equals the lower 6 bits of X.
- F(X) equals 2 if X equals 63 otherwise F(X) equals 3.
- D(X,Y) equals the (upper 2 bits of X) * 256 + Y + 1.
- For compression factor 3:
- L(X) equals the lower 5 bits of X.
- F(X) equals 2 if X equals 31 otherwise F(X) equals 3.
- D(X,Y) equals the (upper 3 bits of X) * 256 + Y + 1.
- For compression factor 4:
- L(X) equals the lower 4 bits of X.
- F(X) equals 2 if X equals 15 otherwise F(X) equals 3.
- D(X,Y) equals the (upper 4 bits of X) * 256 + Y + 1.
-
-5.3 Imploding - Method 6
-------------------------
-
- 5.3.1 The Imploding algorithm is actually a combination of two
- distinct algorithms. The first algorithm compresses repeated byte
- sequences using a sliding dictionary. The second algorithm is
- used to compress the encoding of the sliding dictionary output,
- using multiple Shannon-Fano trees.
-
- 5.3.2 The Imploding algorithm can use a 4K or 8K sliding dictionary
- size. The dictionary size used can be determined by bit 1 in the
- general purpose flag word; a 0 bit indicates a 4K dictionary
- while a 1 bit indicates an 8K dictionary.
-
- 5.3.3 The Shannon-Fano trees are stored at the start of the
- compressed file. The number of trees stored is defined by bit 2 in
- the general purpose flag word; a 0 bit indicates two trees stored,
- a 1 bit indicates three trees are stored. If 3 trees are stored,
- the first Shannon-Fano tree represents the encoding of the
- Literal characters, the second tree represents the encoding of
- the Length information, the third represents the encoding of the
- Distance information. When 2 Shannon-Fano trees are stored, the
- Length tree is stored first, followed by the Distance tree.
-
- 5.3.4 The Literal Shannon-Fano tree, if present is used to represent
- the entire ASCII character set, and contains 256 values. This
- tree is used to compress any data not compressed by the sliding
- dictionary algorithm. When this tree is present, the Minimum
- Match Length for the sliding dictionary is 3. If this tree is
- not present, the Minimum Match Length is 2.
-
- 5.3.5 The Length Shannon-Fano tree is used to compress the Length
- part of the (length,distance) pairs from the sliding dictionary
- output. The Length tree contains 64 values, ranging from the
- Minimum Match Length, to 63 plus the Minimum Match Length.
-
- 5.3.6 The Distance Shannon-Fano tree is used to compress the Distance
- part of the (length,distance) pairs from the sliding dictionary
- output. The Distance tree contains 64 values, ranging from 0 to
- 63, representing the upper 6 bits of the distance value. The
- distance values themselves will be between 0 and the sliding
- dictionary size, either 4K or 8K.
-
- 5.3.7 The Shannon-Fano trees themselves are stored in a compressed
- format. The first byte of the tree data represents the number of
- bytes of data representing the (compressed) Shannon-Fano tree
- minus 1. The remaining bytes represent the Shannon-Fano tree
- data encoded as:
-
- High 4 bits: Number of values at this bit length + 1. (1 - 16)
- Low 4 bits: Bit Length needed to represent value + 1. (1 - 16)
-
- 5.3.8 The Shannon-Fano codes can be constructed from the bit lengths
- using the following algorithm:
-
- 1) Sort the Bit Lengths in ascending order, while retaining the
- order of the original lengths stored in the file.
-
- 2) Generate the Shannon-Fano trees:
-
- Code <- 0
- CodeIncrement <- 0
- LastBitLength <- 0
- i <- number of Shannon-Fano codes - 1 (either 255 or 63)
-
- loop while i >= 0
- Code = Code + CodeIncrement
- if BitLength(i) <> LastBitLength then
- LastBitLength=BitLength(i)
- CodeIncrement = 1 shifted left (16 - LastBitLength)
- ShannonCode(i) = Code
- i <- i - 1
- end loop
-
- 3) Reverse the order of all the bits in the above ShannonCode()
- vector, so that the most significant bit becomes the least
- significant bit. For example, the value 0x1234 (hex) would
- become 0x2C48 (hex).
-
- 4) Restore the order of Shannon-Fano codes as originally stored
- within the file.
-
- Example:
-
- This example will show the encoding of a Shannon-Fano tree
- of size 8. Notice that the actual Shannon-Fano trees used
- for Imploding are either 64 or 256 entries in size.
-
- Example: 0x02, 0x42, 0x01, 0x13
-
- The first byte indicates 3 values in this table. Decoding the
- bytes:
- 0x42 = 5 codes of 3 bits long
- 0x01 = 1 code of 2 bits long
- 0x13 = 2 codes of 4 bits long
-
- This would generate the original bit length array of:
- (3, 3, 3, 3, 3, 2, 4, 4)
-
- There are 8 codes in this table for the values 0 thru 7. Using
- the algorithm to obtain the Shannon-Fano codes produces:
-
- Reversed Order Original
- Val Sorted Constructed Code Value Restored Length
- --- ------ ----------------- -------- -------- ------
- 0: 2 1100000000000000 11 101 3
- 1: 3 1010000000000000 101 001 3
- 2: 3 1000000000000000 001 110 3
- 3: 3 0110000000000000 110 010 3
- 4: 3 0100000000000000 010 100 3
- 5: 3 0010000000000000 100 11 2
- 6: 4 0001000000000000 1000 1000 4
- 7: 4 0000000000000000 0000 0000 4
-
- The values in the Val, Order Restored and Original Length columns
- now represent the Shannon-Fano encoding tree that can be used for
- decoding the Shannon-Fano encoded data. How to parse the
- variable length Shannon-Fano values from the data stream is beyond
- the scope of this document. (See the references listed at the end of
- this document for more information.) However, traditional decoding
- schemes used for Huffman variable length decoding, such as the
- Greenlaw algorithm, can be successfully applied.
-
- 5.3.9 The compressed data stream begins immediately after the
- compressed Shannon-Fano data. The compressed data stream can be
- interpreted as follows:
-
- loop until done
- read 1 bit from input stream.
-
- if this bit is non-zero then (encoded data is literal data)
- if L
<TRUNCATED>