CWE-126 缓冲区上溢读取
Buffer Over-read
结构: Simple
Abstraction: Variant
状态: Draft
被利用可能性: unkown
基本描述
The software reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.
扩展描述
This typically occurs when the pointer or its index is incremented to a position beyond the bounds of the buffer or when pointer arithmetic results in a position outside of the valid memory location to name a few. This may result in exposure of sensitive information or possibly a crash.
相关缺陷
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cwe_Nature: ChildOf cwe_CWE_ID: 125 cwe_View_ID: 1000
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cwe_Nature: ChildOf cwe_CWE_ID: 125 cwe_View_ID: 699
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cwe_Nature: ChildOf cwe_CWE_ID: 788 cwe_View_ID: 1000 cwe_Ordinal: Primary
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cwe_Nature: ChildOf cwe_CWE_ID: 788 cwe_View_ID: 699 cwe_Ordinal: Primary
适用平台
Language: [{'cwe_Name': 'C', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'C++', 'cwe_Prevalence': 'Undetermined'}]
常见的影响
| 范围 | 影响 | 注释 |
|---|---|---|
| Confidentiality | Read Memory | |
| Confidentiality | Bypass Protection Mechanism | By reading out-of-bounds memory, an attacker might be able to get secret values, such as memory addresses, which can be bypass protection mechanisms such as ASLR in order to improve the reliability and likelihood of exploiting a separate weakness to achieve code execution instead of just denial of service. |
示例代码
例
In the following C/C++ example the method processMessageFromSocket() will get a message from a socket, placed into a buffer, and will parse the contents of the buffer into a structure that contains the message length and the message body. A for loop is used to copy the message body into a local character string which will be passed to another method for processing.
bad C
char buffer[BUFFER_SIZE];
char message[MESSAGE_SIZE];
// get message from socket and store into buffer
//Ignoring possibliity that buffer > BUFFER_SIZE
if (getMessage(socket, buffer, BUFFER_SIZE) > 0) {
// place contents of the buffer into message structure
ExMessage *msg = recastBuffer(buffer);
// copy message body into string for processing
int index;
for (index = 0; index msgLength; index++) {
}
message[index] = ' ';
// process message
success = processMessage(message);
}
return success;
}
However, the message length variable from the structure is used as the condition for ending the for loop without validating that the message length variable accurately reflects the length of message body. This can result in a buffer over read by reading from memory beyond the bounds of the buffer if the message length variable indicates a length that is longer than the size of a message body (CWE-130).
例
The following C/C++ example demonstrates a buffer over-read due to a missing NULL terminator. The main method of a pattern matching utility that looks for a specific pattern within a specific file uses the string strncopy() method to copy the command line user input file name and pattern to the Filename and Pattern character arrays respectively.
bad C
{
char Pattern[32];
/ Validate number of parameters and ensure valid content /
...
/ copy filename parameter to variable, may cause off-by-one overflow /
strncpy(Filename, argv[1], sizeof(Filename));
/ copy pattern parameter to variable, may cause off-by-one overflow /
strncpy(Pattern, argv[2], sizeof(Pattern));
printf("Searching file: %s for the pattern: %sn", Filename, Pattern);
Scan_File(Filename, Pattern);
}
However, the code do not take into account that strncpy() will not add a NULL terminator when the source buffer is equal in length of longer than that provide size attribute. Therefore if a user enters a filename or pattern that are the same size as (or larger than) their respective character arrays, a NULL terminator will not be added (CWE-170) which leads to the printf() read beyond the expected end of the Filename and Pattern buffers.
To fix this problem, be sure to subtract 1 from the sizeof() call to allow room for the null byte to be added.
good C
strncpy(Filename, argv[2], sizeof(Filename)-1);
Filename[255]=' ';
/ copy pattern parameter to variable, no off-by-one overflow /
strncpy(Pattern, argv[3], sizeof(Pattern)-1);
Pattern[31]=' ';
分析过的案例
| 标识 | 说明 | 链接 |
|---|---|---|
| CVE-2014-0160 | Chain: "Heartbleed" bug receives an inconsistent length parameter (CWE-130) enabling an out-of-bounds read (CWE-126), returning memory that could include private cryptographic keys and other sensitive data. | https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-0160 |
| CVE-2009-2523 | Chain: product does not handle when an input string is not NULL terminated, leading to buffer over-read or heap-based buffer overflow. | https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-2523 |
Notes
分类映射
| 映射的分类名 | ImNode ID | Fit | Mapped Node Name |
|---|---|---|---|
| PLOVER | Buffer over-read | ||
| Software Fault Patterns | SFP8 | Faulty Buffer Access |
引用
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