zipdetails

zipdetails [-v][--scan][--redact][--utc] zipfile.zip zipdetails -h zipdetails --version

This program creates a detailed report on the internal structure of zip files. For each item of metadata within a zip file the program will output

the offset into the zip file where the item is located.

a textual representation for the item.

an optional hex dump of the item.

The program assumes a prior understanding of the internal structure of Zip files. You should have a copy of the Zip APPNOTE.TXT <http://www.pkware.com/documents/casestudies/APPNOTE.TXT> file at hand to help understand the output from this program.

Default Behaviour

By default the program expects to be given a well-formed zip file. It will navigate the Zip file by first parsing the zip central directory at the end of the file. If that is found, it will then walk through the zip records starting at the beginning of the file. Any badly formed zip data structures encountered are likely to terminate the program.

If the program finds any structural problems with the zip file it will print a summary at the end of the output report. The set of error cases reported is very much a work in progress, so don't rely on this feature to find all the possible errors in a zip file. If you have suggestions for use-cases where this could be enhanced please consider creating an enhancement request (see SUPPORT).

Date/time fields are found in zip files are displayed in local time. Use the --utc option to display these fields in Coordinated Universal Time (UTC).

Scan-Mode

If you do have a potentially corrupt zip file, particulatly where the central directory at the end of the file is absent/incomplete, you can try usng the --scan option to search for zip records that are still present.

When Scan-mode is enabled, the program will walk the zip file from the start, blindly looking for the 4-byte signatures that preceed each of the zip data structures. If it finds any of the recognised signatures it will attempt to dump the associated zip record. For very large zip files, this operation can take a long time to run.

Note that the 4-byte signatures used in zip files can sometimes match with random data stored in the zip file, so care is needed interpreting the results.

OPTIONS

-h

Display help

--redact

Obscure filenames in the output. Handy for the use case where the zip files contains sensitive data that cannot be shared.

--scan

Walk the zip file loking for possible zip records. Can be error-prone. See Scan-Mode

--utc

By default, date/time fields are displayed in local time. Use this option to display them in in Coordinated Universal Time (UTC).

-v

Enable Verbose mode. See Verbose Output.

--version

Display version number of the program and exit.

Default Output

By default zipdetails will output the details of the zip file in three columns.

Column 1

This contains the offset from the start of the file in hex.

Column 2

This contains a textual description of the field.

Column 3

If the field contains a numeric value it will be displayed in hex. Zip stores most numbers in little-endian format - the value displayed will have the little-endian encoding removed. Next, is an optional description of what the value means.

For example, assuming you have a zip file with two entries, like this

$ unzip -l test.zip Archive: setup/test.zip Length Date Time Name --------- ---------- ----- ---- 6 2021-03-23 18:52 latters.txt 6 2021-03-23 18:52 numbers.txt --------- ------- 12 2 files

Running zipdetails will gives this output

$ zipdetails test.zip 0000 LOCAL HEADER #1 04034B50 0004 Extract Zip Spec 0A 1.0 0005 Extract OS 00 MS-DOS 0006 General Purpose Flag 0000 0008 Compression Method 0000 Stored 000A Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 000E CRC 0F8A149C 0012 Compressed Length 00000006 0016 Uncompressed Length 00000006 001A Filename Length 000B 001C Extra Length 0000 001E Filename letters.txt 0029 PAYLOAD abcde. 002F LOCAL HEADER #2 04034B50 0033 Extract Zip Spec 0A 1.0 0034 Extract OS 00 MS-DOS 0035 General Purpose Flag 0000 0037 Compression Method 0000 Stored 0039 Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 003D CRC 261DAFE6 0041 Compressed Length 00000006 0045 Uncompressed Length 00000006 0049 Filename Length 000B 004B Extra Length 0000 004D Filename numbers.txt 0058 PAYLOAD 12345. 005E CENTRAL HEADER #1 02014B50 0062 Created Zip Spec 1E 3.0 0063 Created OS 03 Unix 0064 Extract Zip Spec 0A 1.0 0065 Extract OS 00 MS-DOS 0066 General Purpose Flag 0000 0068 Compression Method 0000 Stored 006A Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 006E CRC 0F8A149C 0072 Compressed Length 00000006 0076 Uncompressed Length 00000006 007A Filename Length 000B 007C Extra Length 0000 007E Comment Length 0000 0080 Disk Start 0000 0082 Int File Attributes 0001 [Bit 0] 1 Text Data 0084 Ext File Attributes 81B40000 0088 Local Header Offset 00000000 008C Filename letters.txt 0097 CENTRAL HEADER #2 02014B50 009B Created Zip Spec 1E 3.0 009C Created OS 03 Unix 009D Extract Zip Spec 0A 1.0 009E Extract OS 00 MS-DOS 009F General Purpose Flag 0000 00A1 Compression Method 0000 Stored 00A3 Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 00A7 CRC 261DAFE6 00AB Compressed Length 00000006 00AF Uncompressed Length 00000006 00B3 Filename Length 000B 00B5 Extra Length 0000 00B7 Comment Length 0000 00B9 Disk Start 0000 00BB Int File Attributes 0001 [Bit 0] 1 Text Data 00BD Ext File Attributes 81B40000 00C1 Local Header Offset 0000002F 00C5 Filename numbers.txt 00D0 END CENTRAL HEADER 06054B50 00D4 Number of this disk 0000 00D6 Central Dir Disk no 0000 00D8 Entries in this disk 0002 00DA Total Entries 0002 00DC Size of Central Dir 00000072 00E0 Offset to Central Dir 0000005E 00E4 Comment Length 0000 Done

Verbose Output

If the -v option is present, column 1 is expanded to include

• The offset from the start of the file in hex.

• The length of the field in hex.

• A hex dump of the bytes in field in the order they are stored in the zip file.

Here is the same zip file dumped using the zipdetails -v option:

$ zipdetails -v test.zip 0000 0004 50 4B 03 04 LOCAL HEADER #1 04034B50 0004 0001 0A Extract Zip Spec 0A 1.0 0005 0001 00 Extract OS 00 MS-DOS 0006 0002 00 00 General Purpose Flag 0000 0008 0002 00 00 Compression Method 0000 Stored 000A 0004 3D 98 77 52 Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 000E 0004 9C 14 8A 0F CRC 0F8A149C 0012 0004 06 00 00 00 Compressed Length 00000006 0016 0004 06 00 00 00 Uncompressed Length 00000006 001A 0002 0B 00 Filename Length 000B 001C 0002 00 00 Extra Length 0000 001E 000B 6C 65 74 74 Filename letters.txt 65 72 73 2E 74 78 74 0029 0006 61 62 63 64 PAYLOAD abcde. 65 0A 002F 0004 50 4B 03 04 LOCAL HEADER #2 04034B50 0033 0001 0A Extract Zip Spec 0A 1.0 0034 0001 00 Extract OS 00 MS-DOS 0035 0002 00 00 General Purpose Flag 0000 0037 0002 00 00 Compression Method 0000 Stored 0039 0004 3D 98 77 52 Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 003D 0004 E6 AF 1D 26 CRC 261DAFE6 0041 0004 06 00 00 00 Compressed Length 00000006 0045 0004 06 00 00 00 Uncompressed Length 00000006 0049 0002 0B 00 Filename Length 000B 004B 0002 00 00 Extra Length 0000 004D 000B 6E 75 6D 62 Filename numbers.txt 65 72 73 2E 74 78 74 0058 0006 31 32 33 34 PAYLOAD 12345. 35 0A 005E 0004 50 4B 01 02 CENTRAL HEADER #1 02014B50 0062 0001 1E Created Zip Spec 1E 3.0 0063 0001 03 Created OS 03 Unix 0064 0001 0A Extract Zip Spec 0A 1.0 0065 0001 00 Extract OS 00 MS-DOS 0066 0002 00 00 General Purpose Flag 0000 0068 0002 00 00 Compression Method 0000 Stored 006A 0004 3D 98 77 52 Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 006E 0004 9C 14 8A 0F CRC 0F8A149C 0072 0004 06 00 00 00 Compressed Length 00000006 0076 0004 06 00 00 00 Uncompressed Length 00000006 007A 0002 0B 00 Filename Length 000B 007C 0002 00 00 Extra Length 0000 007E 0002 00 00 Comment Length 0000 0080 0002 00 00 Disk Start 0000 0082 0002 01 00 Int File Attributes 0001 [Bit 0] 1 Text Data 0084 0004 00 00 B4 81 Ext File Attributes 81B40000 0088 0004 00 00 00 00 Local Header Offset 00000000 008C 000B 6C 65 74 74 Filename letters.txt 65 72 73 2E 74 78 74 0097 0004 50 4B 01 02 CENTRAL HEADER #2 02014B50 009B 0001 1E Created Zip Spec 1E 3.0 009C 0001 03 Created OS 03 Unix 009D 0001 0A Extract Zip Spec 0A 1.0 009E 0001 00 Extract OS 00 MS-DOS 009F 0002 00 00 General Purpose Flag 0000 00A1 0002 00 00 Compression Method 0000 Stored 00A3 0004 3D 98 77 52 Last Mod Time 5277983D Tue Mar 23 19:01:58 2021 00A7 0004 E6 AF 1D 26 CRC 261DAFE6 00AB 0004 06 00 00 00 Compressed Length 00000006 00AF 0004 06 00 00 00 Uncompressed Length 00000006 00B3 0002 0B 00 Filename Length 000B 00B5 0002 00 00 Extra Length 0000 00B7 0002 00 00 Comment Length 0000 00B9 0002 00 00 Disk Start 0000 00BB 0002 01 00 Int File Attributes 0001 [Bit 0] 1 Text Data 00BD 0004 00 00 B4 81 Ext File Attributes 81B40000 00C1 0004 2F 00 00 00 Local Header Offset 0000002F 00C5 000B 6E 75 6D 62 Filename numbers.txt 65 72 73 2E 74 78 74 00D0 0004 50 4B 05 06 END CENTRAL HEADER 06054B50 00D4 0002 00 00 Number of this disk 0000 00D6 0002 00 00 Central Dir Disk no 0000 00D8 0002 02 00 Entries in this disk 0002 00DA 0002 02 00 Total Entries 0002 00DC 0004 72 00 00 00 Size of Central Dir 00000072 00E0 0004 5E 00 00 00 Offset to Central Dir 0000005E 00E4 0002 00 00 Comment Length 0000 Done

The following zip file features are not supported by this program:

• Multi-part archives.

• The strong encryption features defined in the APPNOTE.TXT <http://www.pkware.com/documents/casestudies/APPNOTE.TXT> document.

Error handling is a work in progress. If the program encounters a problem reading a zip file it is likely to terminate with an unhelpful error message.

General feedback/questions/bug reports should be sent to <https://github.com/pmqs/zipdetails/issues>.

Copyright (c) 2011-2022 Paul Marquess. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The primary reference for Zip files is APPNOTE.TXT <http://www.pkware.com/documents/casestudies/APPNOTE.TXT>. An alternative reference is the Info-Zip appnote. This is available from <ftp://ftp.info-zip.org/pub/infozip/doc/> For details of WinZip AES encryption see AES Encryption Information: Encryption Specification AE-1 and AE-2 <https://www.winzip.com/win/es/aes_info.html>. The zipinfo program that comes with the info-zip distribution (<http://www.info-zip.org/>) can also display details of the structure of a zip file.

Paul Marquess pmqs@cpan.org.