CWE - CWE-464: Addition of Data Structure Sentinel (2.11)

Weakness ID: 464

Abstraction: Base

Status: Incomplete

Presentation Filter:

Description

Description Summary

The accidental addition of a data-structure sentinel can cause serious programming logic problems.

Extended Description

Data-structure sentinels are often used to mark the structure of data. A common example of this is the null character at the end of strings or a special sentinel to mark the end of a linked list. It is dangerous to allow this type of control data to be easily accessible. Therefore, it is important to protect from the addition or modification of sentinels.

Time of Introduction

Architecture and Design
Implementation

Applicable Platforms

Languages

C++

Common Consequences

Scope	Effect
Integrity	Technical Impact: Modify application data Generally this error will cause the data structure to not work properly by truncating the data.

Likelihood of Exploit

High to Very High

Demonstrative Examples

Example 1

The following example assigns some character values to a list of characters and prints them each individually, and then as a string. The third character value is intended to be an integer taken from user input and converted to an int.

(Bad Code)

Example Languages: C and C++

char *foo;

foo=malloc(sizeof(char)*5);

foo[0]='a';

foo[1]='a';

foo[2]=atoi(getc(stdin));

foo[3]='c';

foo[4]='\0'

printf("%c %c %c %c %c \n",foo[0],foo[1],foo[2],foo[3],foo[4]);

printf("%s\n",foo);

The first print statement will print each character separated by a space. However, if a non-integer is read from stdin by getc, then atoi will not make a conversion and return 0. When foo is printed as a string, the 0 at character foo[2] will act as a NULL terminator and foo[3] will never be printed.

Potential Mitigations

Phases: Implementation; Architecture and Design

Encapsulate the user from interacting with data sentinels. Validate user input to verify that sentinels are not present.

Phase: Implementation

Proper error checking can reduce the risk of inadvertently introducing sentinel values into data. For example, if a parsing function fails or encounters an error, it might return a value that is the same as the sentinel.

Phase: Architecture and Design

Use an abstraction library to abstract away risky APIs. This is not a complete solution.

Phase: Operation

Use OS-level preventative functionality. This is not a complete solution.

Relationships

Nature	Type	ID	Name	View(s) this relationship pertains to
ChildOf	Weakness Class	138	Improper Neutralization of Special Elements	Research Concepts (primary)1000
ChildOf	Category	461	Data Structure Issues	Development Concepts (primary)699
ChildOf	Category	741	CERT C Secure Coding Section 07 - Characters and Strings (STR)	Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOf	Category	875	CERT C++ Secure Coding Section 07 - Characters and Strings (STR)	Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOf	Category	977	SFP Secondary Cluster: Design	Software Fault Pattern (SFP) Clusters (primary)888
PeerOf	Weakness Base	170	Improper Null Termination	Research Concepts1000
PeerOf	Weakness Base	463	Deletion of Data Structure Sentinel	Research Concepts1000

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Mapped Node Name
CLASP		Addition of data-structure sentinel
CERT C Secure Coding	STR03-C	Do not inadvertently truncate a null-terminated byte string
CERT C Secure Coding	STR06-C	Do not assume that strtok() leaves the parse string unchanged
CERT C++ Secure Coding	STR03-CPP	Do not inadvertently truncate a null-terminated character array
CERT C++ Secure Coding	STR06-CPP	Do not assume that strtok() leaves the parse string unchanged

Content History

Submissions
Submission Date	Submitter	Organization	Source
	CLASP		Externally Mined

Modifications
Modification Date	Modifier	Organization	Source
2008-07-01	Eric Dalci	Cigital	External
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE	Internal
2008-09-08	updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24	CWE Content Team	MITRE	Internal
2008-11-24	updated Relationships, Taxonomy_Mappings
2009-07-27	CWE Content Team	MITRE	Internal
2009-07-27	updated Demonstrative_Examples, Description, Other_Notes, Potential_Mitigations, Relationships
2011-06-01	CWE Content Team	MITRE	Internal
2011-06-01	updated Common_Consequences
2011-06-27	CWE Content Team	MITRE	Internal
2011-06-27	updated Common_Consequences
2011-09-13	CWE Content Team	MITRE	Internal
2011-09-13	updated Relationships, Taxonomy_Mappings
2012-05-11	CWE Content Team	MITRE	Internal
2012-05-11	updated Relationships
2012-10-30	CWE Content Team	MITRE	Internal
2012-10-30	updated Potential_Mitigations
2014-07-30	CWE Content Team	MITRE	Internal
2014-07-30	updated Relationships
Previous Entry Names
Change Date	Previous Entry Name
2008-04-11	Addition of Data-structure Sentinel


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Common Weakness Enumeration

CWE-464: Addition of Data Structure Sentinel