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README.md

minizip-ng Documentation

Table of Contents

API

Constants

Prefix Description
MZ_COMPRESS_LEVEL Compression level enumeration
MZ_COMPRESS_METHOD Compression method enumeration
MZ_ENCODING Character encoding enumeration
MZ_ERROR Error constants
MZ_HASH Hash algorithms and digest sizes
MZ_HOST_SYSTEM System identifiers
MZ_OPEN_MODE Stream open modes
MZ_SEEK Stream seek origins
MZ_ZIP64 Zip64 extrafield options

Interfaces

Name Description
MZ_COMPAT Old minizip 1.x compatibility layer
MZ_OS Operating system level file system operations
MZ_ZIP Zip archive and entry interface
MZ_ZIP_RW Easy zip file extraction and creation

Structures

Name Description
MZ_ZIP_FILE Zip entry information

Extrafield Proposals

The zip reader and writer interface provides support for extended hash algorithms for zip entries, compression of the central directory, and the adding and verifying of CMS signatures for each entry. In order to add support for these features, extrafields were added and are described in the minizip extrafield documentation.

Limitations

  • Archives are required to have a central directory unless recovery mode is enabled.
  • Central directory header values should be correct and it is necessary for the compressed size to be accurate for encryption.
  • Central directory is the only data stored on the last disk of a split-disk archive and doesn't follow disk size restrictions.

Third-Party Limitations

  • Windows Explorer zip extraction utility does not support disk splitting. 1
  • macOS archive utility does not properly support ZIP files over 4GB. 1 2

Xcode Instructions

To create an Xcode project with CMake use:

cmake -G Xcode .

Zlib Configuration

By default, if zlib is not found, it will be pulled as an external project and installed. This requires Git to be installed and available to your command interpreter.

  • To specify your own zlib repository use ZLIB_REPOSITORY and/or ZLIB_TAG.
  • To specify your own zlib installation use ZLIB_LIBRARY and ZLIB_INCLUDE_DIR.

Compiling with Zlib-ng

To compile using zlib-ng use the following cmake args:

-DZLIB_REPOSITORY=https://github.com/zlib-ng/zlib-ng -DZLIB_TAG=develop

Compiling and Installing Zlib (Windows)

To compile and install zlib to the Program Files directory with an Administrator command prompt:

cmake -DCMAKE_INSTALL_PREFIX="C:\Program Files (x86)\zlib" .
cmake --build . --config Release --target INSTALL

Configure Existing Zlib Installation (Windows)

To configure cmake with an existing zlib installation point cmake to your install directories:

cmake -DZLIB_LIBRARY:FILEPATH="C:\Program Files (x86)\zlib\lib\zlibstaticd.lib" .
cmake -DZLIB_INCLUDE_DIR:PATH="C:\Program Files (x86)\zlib\include" .

Upgrading from 1.x

If you are using CMAKE it will automatically include all the files and define all the #defines required based on your configuration and it will also build the project files necessary for your platform.

However, for some projects it may be necessary to drop in the new files into an existing project. In that instance, some #defines will have to be set as they have changed.

1.x 2.x Description
HAVE_ZLIB Compile with ZLIB library. Older versions of Minizip required ZLIB. It is now possible to alternatively compile only using liblzma library.
HAVE_LZMA Compile with LZMA support.
HAVE_BZIP2 HAVE_BZIP2 Compile with BZIP2 library support.
HAVE_APPLE_COMPRESSION HAVE_LIBCOMP Compile using Apple Compression library.
HAVE_AES HAVE_WZAES Compile using AES encryption support.
HAVE_PKCRYPT Compile using PKWARE traditional encryption support. Previously this was automatically assumed.
NOUNCRYPT Nearest to MZ_ZIP_NO_ENCRYPTION Previously turn off all decryption support.
NOCRYPT Nearest to MZ_ZIP_NO_ENCRYPTION Previously turned off all encryption support.
MZ_ZIP_NO_ENCRYPTION Turns off all encryption/decryption support.
NO_ADDFILEINEXISTINGZIP Not currently supported.
IOWIN32_USING_WINRT_API MZ_WINRT_API Enable WinRT API support in Win32 file I/O stream.
MZ_ZIP_NO_COMPRESSION Intended to reduce compilation size if not using zipping functionality.
MZ_ZIP_NO_COMPRESSION Intended to reduce compilation size if not using zipping functionality.

At a minimum HAVE_ZLIB and HAVE_PKCRYPT will be necessary to be defined for drop-in replacement. To determine which files to drop in, see the Contents section of the README.

The compatibility layer for 1.x does not currently provide support for the ioapi interface; it has been replaced with a new streaming interface. It is possible to create a stream interface in a similar way that you would have created an ioapi interface.

Security Considerations

WinZip AES

When compressing an archive with WinZIP AES enabled, by default it uses 256 bit encryption. During decompression whatever bit encryption was specified when the entry was added to the archive will be used.

WinZip AES encryption uses CTR on top of ECB which prevents identical ciphertext blocks that might occur when using ECB by itself. More details about the WinZIP AES format can be found in the winzip documentation.

How to Create a Secure Zip

In order to create a secure zip file you must:

  • Use WinZIP AES encryption
  • Zip the central directory
  • Sign the zip file using a certificate

The combination of using AES encryption and zipping the central directory prevents data leakage through filename exposure.