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CWE-289: Authentication Bypass by Alternate Name

Authentication Bypass by Alternate Name
Weakness ID: 289 (Weakness Variant)Status: Incomplete
+ Description

Description Summary

The software performs authentication based on the name of a resource being accessed, or the name of the actor performing the access, but it does not properly check all possible names for that resource or actor.
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms



+ Common Consequences

Technical Impact: Bypass protection mechanism

+ Observed Examples
Protection mechanism that restricts URL access can be bypassed using URL encoding.
Bypass of authentication for files using "\" (backslash) or "%5C" (encoded backslash).
+ Potential Mitigations

Phase: Architecture and Design

Strategy: Input Validation

Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class592Authentication Bypass Issues
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory845CERT Java Secure Coding Section 00 - Input Validation and Data Sanitization (IDS)
Weaknesses Addressed by the CERT Java Secure Coding Standard (primary)844
ChildOfCategoryCategory898SFP Cluster: Authentication
Software Fault Pattern (SFP) Clusters (primary)888
CanFollowWeakness VariantWeakness Variant46Path Equivalence: 'filename ' (Trailing Space)
Research Concepts1000
CanFollowWeakness VariantWeakness Variant52Path Equivalence: '/multiple/trailing/slash//'
Research Concepts1000
CanFollowCategoryCategory171Cleansing, Canonicalization, and Comparison Errors
Research Concepts1000
CanFollowWeakness VariantWeakness Variant173Improper Handling of Alternate Encoding
Research Concepts1000
CanFollowWeakness BaseWeakness Base178Improper Handling of Case Sensitivity
Research Concepts1000
+ Relationship Notes

Overlaps equivalent encodings, canonicalization, authorization, multiple trailing slash, trailing space, mixed case, and other equivalence issues.

+ Theoretical Notes

Alternate names are useful in data driven manipulation attacks, not just for authentication.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERAuthentication bypass by alternate name
CERT Java Secure CodingIDS01-JNormalize strings before validating them
+ Content History
Submission DateSubmitterOrganizationSource
Externally Mined
Modification DateModifierOrganizationSource
updated Potential_Mitigations, Time_of_Introduction
updated Description, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings
updated Observed_Examples
updated Other_Notes, Potential_Mitigations, Theoretical_Notes
updated Potential_Mitigations
updated Common_Consequences, Relationships, Taxonomy_Mappings
updated Relationships, Taxonomy_Mappings
updated Potential_Mitigations
Page Last Updated: June 23, 2014