CWE-672 在过期或释放后对资源进行操作

Operation on a Resource after Expiration or Release

结构: Simple

Abstraction: Class

状态: Draft

被利用可能性: unkown

基本描述

The software uses, accesses, or otherwise operates on a resource after that resource has been expired, released, or revoked.

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 666 cwe_View_ID: 1000 cwe_Ordinal: Primary

适用平台

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

Paradigm: {'cwe_Name': 'Mobile', 'cwe_Prevalence': 'Undetermined'}

常见的影响

范围 影响 注释
['Integrity', 'Confidentiality'] ['Modify Application Data', 'Read Application Data'] If a released resource is subsequently reused or reallocated, then an attempt to use the original resource might allow access to sensitive data that is associated with a different user or entity.
['Other', 'Availability'] ['Other', 'DoS: Crash, Exit, or Restart'] When a resource is released it might not be in an expected state, later attempts to access the resource may lead to resultant errors that may lead to a crash.

示例代码

例

The following code shows a simple example of a use after free error:

bad C

char ptr = (char)malloc (SIZE);
if (err) {
abrt = 1;
free(ptr);
}
...
if (abrt) {
logError("operation aborted before commit", ptr);
}

When an error occurs, the pointer is immediately freed. However, this pointer is later incorrectly used in the logError function.

例

The following code shows a simple example of a double free error:

bad C

char ptr = (char)malloc (SIZE);
...
if (abrt) {
free(ptr);
}
...
free(ptr);

Double free vulnerabilities have two common (and sometimes overlapping) causes:

None

Although some double free vulnerabilities are not much more complicated than the previous example, most are spread out across hundreds of lines of code or even different files. Programmers seem particularly susceptible to freeing global variables more than once.

例

In the following C/C++ example the method processMessage is used to process a message received in the input array of char arrays. The input message array contains two char arrays: the first is the length of the message and the second is the body of the message. The length of the message is retrieved and used to allocate enough memory for a local char array, messageBody, to be created for the message body. The messageBody is processed in the method processMessageBody that will return an error if an error occurs while processing. If an error occurs then the return result variable is set to indicate an error and the messageBody char array memory is released using the method free and an error message is sent to the logError method.

bad C

#define FAIL 0
#define SUCCESS 1
#define ERROR -1
#define MAX_MESSAGE_SIZE 32

int processMessage(char message)
{
int result = SUCCESS;

int length = getMessageLength(message[0]);
char messageBody;

if ((length > 0) && (length < MAX_MESSAGE_SIZE)) {
messageBody = (char)malloc(length*sizeof(char));
messageBody = &message[1][0];

int success = processMessageBody(messageBody);

if (success == ERROR) {
result = ERROR;
free(messageBody);
}
}
else {
printf("Unable to process message; invalid message length");
result = FAIL;
}

if (result == ERROR) {
logError("Error processing message", messageBody);
}

return result;
}

However, the call to the method logError includes the messageBody after the memory for messageBody has been released using the free method. This can cause unexpected results and may lead to system crashes. A variable should never be used after its memory resources have been released.

good C

...
messageBody = (char)malloc(lengthsizeof(char));
messageBody = &message[1][0];

int success = processMessageBody(messageBody);

if (success == ERROR) {
result = ERROR;
logError("Error processing message", messageBody);
free(messageBody);
}
...

分析过的案例

标识 说明 链接

分类映射

映射的分类名 ImNode ID Fit Mapped Node Name
Software Fault Patterns SFP15 Faulty Resource Use
CERT C Secure Coding FIO46-C CWE More Abstract Do not access a closed file
CERT C Secure Coding MEM30-C CWE More Abstract Do not access freed memory
OMG ASCSM ASCSM-CWE-672

引用