Improper Handling of Apple HFS+ Alternate Data Stream Path
Weakness ID: 72 (Weakness Variant)Status: Incomplete
+ Description

Description Summary

The software does not properly handle special paths that may identify the data or resource fork of a file on the HFS+ file system.

Extended Description

If the software chooses actions to take based on the file name, then if an attacker provides the data or resource fork, the software may take unexpected actions. Further, if the software intends to restrict access to a file, then an attacker might still be able to bypass intended access restrictions by requesting the data or resource fork for that file.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms



Operating Systems

Mac OS

+ Demonstrative Examples

Example 1

A web server that interprets FILE.cgi as processing instructions could disclose the source code for FILE.cgi by requesting FILE.cgi/..namedfork/data. This might occur because the web server invokes the default handler which may return the contents of the file.

+ Observed Examples
+ Background Details

The Apple HFS+ file system permits files to have multiple data input streams, accessible through special paths. The Mac OS X operating system provides a way to access the different data input streams through special paths and as an extended attribute:

- Resource fork: file/..namedfork/rsrc, file/rsrc (deprecated),

- Data fork: file/..namedfork/data (only versions prior to Mac OS X v10.5)

Additionally, on filesystems that lack native support for multiple streams, the resource fork and file metadata may be stored in a file with "._" prepended to the name.

Forks can also be accessed through non-portable APIs.

Forks inherit the file system access controls of the file they belong to.

Programs need to control access to these paths, if the processing of a file system object is dependent on the structure of its path.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base66Improper Handling of File Names that Identify Virtual Resources
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory70Mac Virtual File Problems
Resource-specific Weaknesses (primary)631
Development Concepts699
+ Research Gaps


+ Theoretical Notes

This and similar problems exist because the same resource can have multiple identifiers that dictate which behavior can be performed on the resource.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERApple HFS+ alternate data stream
+ Content History
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other Notes, Taxonomy Mappings
2008-11-05David RemahlAppleExternal
clarified description, provided background details, and added demonstrative example
2008-11-24CWE Content TeamMITREInternal
updated Applicable Platforms, Background Details, Demonstrative Examples, Description, Name, References
2009-05-27CWE Content TeamMITREInternal
updated Name
2009-10-29CWE Content TeamMITREInternal
updated Other Notes, Theoretical Notes
Previous Entry Names
Change DatePrevious Entry Name
2008-11-24Apple HFS+ Alternate Data Stream
2009-05-27Failure to Handle Apple HFS+ Alternate Data Stream Path