CWE-27 路径遍历:'dir/../../filename'

admin 2022年1月5日21:05:08CWE(弱点枚举)评论15 views3363字阅读11分12秒阅读模式

CWE-27 路径遍历:'dir/../../filename'

Path Traversal: 'dir/../../filename'

结构: Simple

Abstraction: Variant

状态: Draft

被利用可能性: unkown

基本描述

The software uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize multiple internal "../" sequences that can resolve to a location that is outside of that directory.

扩展描述

This allows attackers to traverse the file system to access files or directories that are outside of the restricted directory.

The 'directory/../../filename' manipulation is useful for bypassing some path traversal protection schemes. Sometimes a program only removes one "../" sequence, so multiple "../" can bypass that check. Alternately, this manipulation could be used to bypass a check for "../" at the beginning of the pathname, moving up more than one directory level.

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 23 cwe_View_ID: 1000 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 23 cwe_View_ID: 699 cwe_Ordinal: Primary

适用平台

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

常见的影响

范围 影响 注释
['Confidentiality', 'Integrity'] ['Read Files or Directories', 'Modify Files or Directories']

可能的缓解方案

MIT-5.1 Implementation

策略: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
When validating filenames, use stringent whitelists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a whitelist of allowable file extensions, which will help to avoid CWE-434.
Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a blacklist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.

MIT-20 Implementation

策略: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

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
PLOVER 'directory/../../filename
Software Fault Patterns SFP16 Path Traversal

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  • 本文由 发表于 2022年1月5日21:05:08
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