CWE-909 资源初始化缺失

Missing Initialization of Resource

结构: Simple

Abstraction: Base

状态: Incomplete

被利用可能性: Medium

基本描述

The software does not initialize a critical resource.

扩展描述

Many resources require initialization before they can be properly used. If a resource is not initialized, it could contain unpredictable or expired data, or it could be initialized to defaults that are invalid. This can have security implications when the resource is expected to have certain properties or values.

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 665 cwe_View_ID: 1000 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 665 cwe_View_ID: 1003 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 665 cwe_View_ID: 699 cwe_Ordinal: Primary

  • cwe_Nature: CanPrecede cwe_CWE_ID: 908 cwe_View_ID: 1000

适用平台

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

常见的影响

范围 影响 注释
Confidentiality ['Read Memory', 'Read Application Data'] When reusing a resource such as memory or a program variable, the original contents of that resource may not be cleared before it is sent to an untrusted party.
Availability DoS: Crash, Exit, or Restart The uninitialized resource may contain values that cause program flow to change in ways that the programmer did not intend.

可能的缓解方案

Implementation

策略:

Explicitly initialize the resource before use. If this is performed through an API function or standard procedure, follow all specified steps.

Implementation

策略:

Pay close attention to complex conditionals that affect initialization, since some branches 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.

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

private boolean initialized = true;
public void someMethod() {
if (!initialized) {

// perform initialization tasks
...

initialized = true;
}

例

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

bad Perl

$username = GetCurrentUser();
$state = GetStateData($username);
if (defined($state)) {
$uid = ExtractUserID($state);
}

# do stuff
if ($uid == 0) {
DoAdminThings();
}

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

char str[20];
strcat(str, "hello world");
printf("%s", str);

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.