CAPEC 描述

This type of attack leverages the use of symbolic links to cause buffer overflows. An adversary can try to create or manipulate a symbolic link file such that its contents result in out of bounds data. When the target software processes the symbolic link file, it could potentially overflow internal buffers with insufficient bounds checking.

CAPEC 信息

执行流程

1) Explore

[Identify target application] The adversary identifies a target application or program that might load in certain files to memory.

2) Experiment

[Find injection vector] The adversary identifies an injection vector to deliver the excessive content to the targeted application's buffer.

技术手段

The adversary creates or modifies a symbolic link pointing to those files which contain an excessive amount of data. If creating a symbolic link to one of those files causes different behavior in the application, then an injection vector has been identified.

3) Experiment

[Craft overflow file content] The adversary crafts the content to be injected. If the intent is to simply cause the software to crash, the content need only consist of an excessive quantity of random data. If the intent is to leverage the overflow for execution of arbitrary code, the adversary crafts the payload in such a way that the overwritten return address is replaced with one of the adversary's choosing.

技术手段

Create malicious shellcode that will execute when the program execution is returned to it.
Use a NOP-sled in the overflow content to more easily "slide" into the malicious code. This is done so that the exact return address need not be correct, only in the range of all of the NOPs

4) Exploit

[Overflow the buffer] Using the specially crafted file content, the adversary creates a symbolic link from the identified resource to the malicious file, causing a targeted buffer overflow attack.

前提条件

The adversary can create symbolic link on the target host.
The target host does not perform correct boundary checking while consuming data from a resources.

所需技能

An adversary can simply overflow a buffer by inserting a long string into an adversary-modifiable injection vector. The result can be a DoS.
Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level.

缓解措施

Pay attention to the fact that the resource you read from can be a replaced by a Symbolic link. You can do a Symlink check before reading the file and decide that this is not a legitimate way of accessing the resource.
Because Symlink can be modified by an adversary, make sure that the ones you read are located in protected directories.
Pay attention to the resource pointed to by your symlink links (See attack pattern named "Forced Symlink race"), they can be replaced by malicious resources.
Always check the size of the input data before copying to a buffer.
Use a language or compiler that performs automatic bounds checking.
Use an abstraction library to abstract away risky APIs. Not a complete solution.
Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution.
Use OS-level preventative functionality. Not a complete solution.

相关弱点

CWE-ID	弱点名称
CWE-120	Buffer Copy without Checking Size of Input The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
CWE-285	Improper Authorization The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
CWE-302	Authentication Bypass by Assumed-Immutable Data The authentication scheme or implementation uses key data elements that are assumed to be immutable, but can be controlled or modified by the attacker.
CWE-118	Incorrect Access of Indexable Resource The product does not restrict or incorrectly restricts operations within the boundaries of a resource that is accessed using an index or pointer, such as memory or files.
CWE-119	Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary.
CWE-74	Improper Neutralization of Special Elements in Output Used by a Downstream Component The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.
CWE-20	Improper Input Validation The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
CWE-680	Integer Overflow to Buffer Overflow The product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow.
CWE-697	Incorrect Comparison The product compares two entities in a security-relevant context, but the comparison is incorrect.

参考资料

REF-1

Exploiting Software: How to Break Code
G. Hoglund, G. McGraw.

提交记录

名称	组织	日期	发布日期
CAPEC Content Team	The MITRE Corporation	2014-06-23 +00:00

修改记录

名称	组织	日期	备注
CAPEC Content Team	The MITRE Corporation	2018-07-31 +00:00	Updated References
CAPEC Content Team	The MITRE Corporation	2021-10-21 +00:00	Updated Execution_Flow
CAPEC Content Team	The MITRE Corporation	2022-02-22 +00:00	Updated Description, Example_Instances, Indicators, Mitigations, Prerequisites, Skills_Required
CAPEC Content Team	The MITRE Corporation	2022-09-29 +00:00	Updated Example_Instances

CAPEC-45 详情

CAPEC-45