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APPNOTE.TXT
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File: APPNOTE.TXT - .ZIP File Format Specification
Version: 6.3.2
Revised: September 28, 2007
Copyright (c) 1989 - 2007 PKWARE Inc., All Rights Reserved.
The use of certain technological aspects disclosed in the current
APPNOTE is available pursuant to the below section entitled
"Incorporating PKWARE Proprietary Technology into Your Product".
I. Purpose
----------
This specification is intended to define a cross-platform,
interoperable file storage and transfer format. Since its
first publication in 1989, PKWARE has remained committed to
ensuring the interoperability of the .ZIP file format through
publication and maintenance of this specification. We trust that
all .ZIP compatible vendors and application developers that have
adopted and benefited from this format will share and support
this commitment to interoperability.
II. Contacting PKWARE
---------------------
PKWARE, Inc.
648 N. Plankinton Avenue, Suite 220
Milwaukee, WI 53203
+1-414-289-9788
+1-414-289-9789 FAX
III. Disclaimer
---------------
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.
If the version of this file is marked as a NOTIFICATION OF CHANGE,
the content defines an Early Feature Specification (EFS) change
to the .ZIP file format that may be subject to modification prior
to publication of the Final Feature Specification (FFS). This
document may also contain information on Planned Feature
Specifications (PFS) defining recognized future extensions.
IV. Change Log
--------------
Version Change Description Date
------- ------------------ ----------
5.2 -Single Password Symmetric Encryption 06/02/2003
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
V. General Format of a .ZIP file
--------------------------------
Files stored in arbitrary order. Large .ZIP files can span multiple
volumes or be split into user-defined segment sizes. All values
are stored in little-endian byte order unless otherwise specified.
Overall .ZIP file format:
[local file header 1]
[file data 1]
[data descriptor 1]
.
.
.
[local file header n]
[file data n]
[data descriptor n]
[archive decryption header]
[archive extra data record]
[central directory]
[zip64 end of central directory record]
[zip64 end of central directory locator]
[end of central directory record]
A. 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)
B. File data
Immediately following the local header for a file
is the compressed or stored data for the file.
The series of [local file header][file data][data
descriptor] repeats for each file in the .ZIP archive.
C. Data descriptor:
crc-32 4 bytes
compressed size 4 bytes
uncompressed size 4 bytes
This descriptor exists only 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 is 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.
When compressing files, compressed and uncompressed sizes
should be stored in ZIP64 format (as 8 byte values) when a
files 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.
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.
When writing ZIP files, it is recommended to 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.
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.
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 should be set to binary zeros.
D. Archive decryption header:
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 will precede the encrypted data segment. The encrypted
data segment will 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. Refer to the
section on the Strong Encryption Specification for information
on the fields used in the Archive Decryption Header record.
E. Archive extra data record:
archive extra data signature 4 bytes (0x08064b50)
extra field length 4 bytes
extra field data (variable size)
The Archive Extra Data Record 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 present, this record immediately precedes the central
directory data structure. The size of this data record will 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.
F. Central directory structure:
[file header 1]
.
.
.
[file 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)
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.
G. 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)
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.
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.
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.
Multiple special purpose data blocks may be present, but 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.
H. 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
I. 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)
J. Explanation of fields:
version made by (2 bytes)
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. 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
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.
version needed to extract (2 bytes)
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 should 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.
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
* 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 should 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 should 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 should also be set.
This field should be set appropriately to indicate whether
Version 1 or Version 2 format is in use.
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 should
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.
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: Used 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.
Bit 14: Reserved by PKWARE.
Bit 15: Reserved by PKWARE.
compression method: (2 bytes)
(see accompanying documentation for algorithm
descriptions)
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
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.
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.
compressed size: (4 bytes)
uncompressed size: (4 bytes)
The size of the file compressed and uncompressed,
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.
file name length: (2 bytes)
extra field length: (2 bytes)
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.
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.
internal file attributes: (2 bytes)
Bits 1 and 2 are reserved for use by PKWARE.
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.
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.
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.
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.
file name: (Variable)
The name of the file, with optional relative path.
The path stored should not contain a drive or
device letter, or a leading slash. All slashes
should 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. If encrypting
the central directory 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.
extra field: (Variable)
This is for expansion. If additional information
needs to be stored for special needs or for specific
platforms, it should be stored here. Earlier versions
of the software can then safely skip this file, and
find the next file or header. This field will be 0
length in version 1.0.
In order to allow different programs and different types
of information to be stored in the 'extra' field in .ZIP
files, the following structure should 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 ID's of 0 thru 31 are reserved for use by PKWARE.
The remaining ID's can be used by third party vendors for
proprietary usage.
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)
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.
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.
In case two different programs should appropriate the same
Header ID value, it is strongly recommended that each
program 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.
-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 will
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.
-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 it's entirety within this
structure. There will only ever be one "block" of data in
VarFields[].
-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
-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
Rules:
1. There will be one or more of 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.
2. No word alignment or padding is performed.
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.
-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.
-PATCH Descriptor Extra Field (0x000f):
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
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
Actions
Action Value
------ -----
none 0
add 1
delete 2
patch 3