forked from KolibriOS/kolibrios
112 lines
5.8 KiB
Plaintext
112 lines
5.8 KiB
Plaintext
Info-ZIP portable Zip/UnZip Windows NT security descriptor support
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==================================================================
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Scott Field (sfield@microsoft.com), 8 October 1996
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This version of Info-ZIP's Win32 code allows for processing of Windows
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NT security descriptors if they were saved in the .zip file using the
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appropriate Win32 Zip running under Windows NT. This also requires
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that the file system that Zip/UnZip operates on supports persistent
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Acl storage. When the operating system is not Windows NT and the
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target file system does not support persistent Acl storage, no security
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descriptor processing takes place.
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A Windows NT security descriptor consists of any combination of the
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following components:
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an owner (Sid)
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a primary group (Sid)
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a discretionary ACL (Dacl)
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a system ACL (Sacl)
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qualifiers for the preceding items
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By default, Zip will save all aspects of the security descriptor except
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for the Sacl. The Sacl contains information pertaining to auditing of
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the file, and requires a security privilege be granted to the calling
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user in addition to being enabled by the calling application. In order
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to save the Sacl during Zip, the user must specify the -! switch on the
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Zip commandline. The user must also be granted either the SeBackupPrivilege
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"Backup files and directories" or the SeSystemSecurityPrivilege "Manage
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auditing and security log".
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By default, UnZip will not restore any aspects of the security descriptor.
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If the -X option is specified to UnZip, the Dacl is restored to the file.
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The other items in the security descriptor on the new file will receive
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default values. If the -XX option is specified to UnZip, as many aspects
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of the security descriptor as possible will be restored. If the calling
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user is granted the SeRestorePrivilege "Restore files and directories",
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all aspects of the security descriptor will be restored. If the calling
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user is only granted the SeSystemSecurityPrivilege "Manage auditing and
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security log", only the Dacl and Sacl will be restored to the new file.
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Note that when operating on files that reside on remote volumes, the
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privileges specified above must be granted to the calling user on that
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remote machine. Currently, there is no way to directly test what privileges
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are present on a remote machine, so Zip and UnZip make a remote privilege
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determination based on an indirect method.
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UnZip considerations
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--------------------
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In order for file security to be processed correctly, any directory entries
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that have a security descriptor will be processed at the end of the unzip
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cycle. This allows for unzip to process files within the newly created
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directory regardless of the security descriptor associated with the directory
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entry. This also prevents security inheritance problems that can occur as
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a result of creating a new directory and then creating files in that directory
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that will inherit parent directory permissions; such inherited permissions may
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prevent the security descriptor taken from the zip file from being applied
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to the new file.
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If directories exist which match directory/extract paths in the .zip file,
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file security is not updated on the target directory. It is assumed that if
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the target directory already exists, then appropriate security has already
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been applied to that directory.
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"unzip -t" will test the integrity of stored security descriptors when
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present and the operating system is Windows NT.
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ZipInfo (unzip -Z) will display information on stored security descriptor
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when "unzip -Zv" is specifed.
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Potential uses
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==============
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The obvious use for this new support is to better support backup and restore
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operations in a Windows NT environment where NTFS file security is utilized.
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This allows individuals and organizations to archive files in a portable
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fashion and transport these files across the organization.
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Another potential use of this support is setup and installation. This
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allows for distribution of Windows NT based applications that have preset
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security on files and directories. For example, prior to creation of the
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.zip file, the user can set file security via File Manager or Explorer on
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the files to be contained in the .zip file. In many cases, it is appropriate
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to only grant Everyone Read access to .exe and .dll files, while granting
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Administrators Full control. Using this support in conjunction with the
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unzipsfx.exe self-extractor stub can yield a useful and powerful way to
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install software with preset security (note that -X or -XX should be
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specified on the self-extractor commandline).
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When creating .zip files with security which are intended for transport
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across systems, it is important to take into account the relevance of
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access control entries and the associated Sid of each entry. For example,
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if a .zip file is created on a Windows NT workstation, and file security
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references local workstation user accounts (like an account named Fred),
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this access entry will not be relevant if the .zip file is transported to
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another machine. Where possible, take advantage of the built-in well-known
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groups, like Administrators, Everyone, Network, Guests, etc. These groups
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have the same meaning on any Windows NT machine. Note that the names of
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these groups may differ depending on the language of the installed Windows
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NT, but this isn't a problem since each name has well-known ID that, upon
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restore, translates to the correct group name regardless of locale.
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When access control entries contain Sid entries that reference Domain
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accounts, these entries will only be relevant on systems that recognize
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the referenced domain. Generally speaking, the only side effects of
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irrelevant access control entries is wasted space in the stored security
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descriptor and loss of complete intended access control. Such irrelevant
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access control entries will show up as "Account Unknown" when viewing file
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security with File Manager or Explorer.
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