CWE-665 初始化不恰当

Improper Initialization

结构: Simple

Abstraction: Class

状态: Draft

被利用可能性: Medium

基本描述

The software does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used.

扩展描述

This can have security implications when the associated resource is expected to have certain properties or values, such as a variable that determines whether a user has been authenticated or not.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 664 cwe_View_ID: 1000 cwe_Ordinal: Primary

适用平台

Language: {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}

常见的影响

检测方法

DM-2 Automated Dynamic Analysis

DM-12 Manual Dynamic Analysis

可能的缓解方案

MIT-3 Requirements

策略: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, in Java, if the programmer does not explicitly initialize a variable, then the code could produce a compile-time error (if the variable is local) or automatically initialize the variable to the default value for the variable's type. In Perl, if explicit initialization is not performed, then a default value of undef is assigned, which is interpreted as 0, false, or an equivalent value depending on the context in which the variable is accessed.

Architecture and Design

策略:

Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values.

Implementation

策略:

Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage.

Implementation

策略:

Pay close attention to complex conditionals that affect initialization, since some conditions might not perform the initialization.

Implementation

策略:

Avoid race conditions (CWE-362) during initialization routines.

Build and Compilation

策略:

Run or compile your software with settings that generate warnings about uninitialized variables or data.

Testing

策略:

Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible.

示例代码

例

Here, a boolean initiailized field is consulted to ensure that initialization tasks are only completed once. However, the field is mistakenly set to true during static initialization, so the initialization code is never reached.

bad Java

例

The following code intends to limit certain operations to the administrator only.

bad Perl

If the application is unable to extract the state information - say, due to a database timeout - then the $uid variable will not be explicitly set by the programmer. This will cause $uid to be regarded as equivalent to "0" in the conditional, allowing the original user to perform administrator actions. Even if the attacker cannot directly influence the state data, unexpected errors could cause incorrect privileges to be assigned to a user just by accident.

例

The following code intends to concatenate a string to a variable and print the string.

bad C

This might seem innocent enough, but str was not initialized, so it contains random memory. As a result, str[0] might not contain the null terminator, so the copy might start at an offset other than 0. The consequences can vary, depending on the underlying memory.

If a null terminator is found before str[8], then some bytes of random garbage will be printed before the "hello world" string. The memory might contain sensitive information from previous uses, such as a password (which might occur as a result of CWE-14 or CWE-244). In this example, it might not be a big deal, but consider what could happen if large amounts of memory are printed out before the null terminator is found.

If a null terminator isn't found before str[8], then a buffer overflow could occur, since strcat will first look for the null terminator, then copy 12 bytes starting with that location. Alternately, a buffer over-read might occur (CWE-126) if a null terminator isn't found before the end of the memory segment is reached, leading to a segmentation fault and crash.

分析过的案例

分类映射

相关攻击模式

• CAPEC-26
• CAPEC-29

引用

• REF-436 Exploiting Uninitialized Data

• REF-437 MS08-014 : The Case of the Uninitialized Stack Variable Vulnerability

• REF-62 The Art of Software Security Assessment