CWE-637: Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')
Unnecessary Complexity in Protection Mechanism (Not Using 'Economy of Mechanism')
Weakness ID: 637 (Weakness Class)
Status: Draft
Description
Description Summary
The software uses a more complex mechanism than necessary, which could lead to resultant weaknesses when the mechanism is not correctly understood, modeled, configured, implemented, or used.
Extended Description
Security mechanisms should be as simple as possible. Complex security mechanisms may engender partial implementations and compatibility problems, with resulting mismatches in assumptions and implemented security. A corollary of this principle is that data specifications should be as simple as possible, because complex data specifications result in complex validation code. Complex tasks and systems may also need to be guarded by complex security checks, so simple systems should be preferred.
Alternate Terms
Unnecessary Complexity
Time of Introduction
Architecture and Design
Implementation
Operation
Applicable Platforms
Languages
All
Common Consequences
Scope
Effect
Other
Technical Impact: Other
Demonstrative Examples
Example 1
The IPSEC specification is complex, which resulted in bugs, partial
implementations, and incompatibilities between vendors.
Example 2
HTTP Request Smuggling (CWE-444) attacks are feasible because there are not stringent requirements for how illegal or inconsistent HTTP headers should be handled. This can lead to inconsistent implementations in which a proxy or firewall interprets the same data stream as a different set of requests than the end points in that stream.
Either a filename extension and a Content-Type header could be used to infer the file type, but the developer only checks the Content-Type, enabling unrestricted file upload (CWE-434).
In Apache environments, a "filename.php.gif" can
be redirected to the PHP interpreter instead of being sent as an image/gif
directly to the user. Not knowing this, the developer only checks the last
extension of a submitted filename, enabling arbitrary code
execution.
The developer cleanses the $_REQUEST superglobal
array, but PHP also populates $_GET, allowing attackers to bypass the
protection mechanism and conduct SQL injection attacks against code that
uses $_GET.
Potential Mitigations
Avoid complex security mechanisms when simpler ones would meet
requirements. Avoid complex data models, and unnecessarily complex
operations. Adopt architectures that provide guarantees, simplify
understanding through elegance and abstraction, and that can be
implemented similarly. Modularize, isolate and do not trust complex
code, and apply other secure programming principles on these modules
(e.g., least privilege) to mitigate vulnerabilities.
Weakness Ordinalities
Ordinality
Description
Primary
(where
the weakness exists independent of other weaknesses)
Description
