CWE-639 通过用户控制密钥绕过授权机制

Authorization Bypass Through User-Controlled Key

结构: Simple

Abstraction: Base

状态: Incomplete

被利用可能性: High

基本描述

The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.

扩展描述

Retrieval of a user record occurs in the system based on some key value that is under user control. The key would typically identify a user-related record stored in the system and would be used to lookup that record for presentation to the user. It is likely that an attacker would have to be an authenticated user in the system. However, the authorization process would not properly check the data access operation to ensure that the authenticated user performing the operation has sufficient entitlements to perform the requested data access, hence bypassing any other authorization checks present in the system.

For example, attackers can look at places where user specific data is retrieved (e.g. search screens) and determine whether the key for the item being looked up is controllable externally. The key may be a hidden field in the HTML form field, might be passed as a URL parameter or as an unencrypted cookie variable, then in each of these cases it will be possible to tamper with the key value.

One manifestation of this weakness is when a system uses sequential or otherwise easily-guessable session IDs that would allow one user to easily switch to another user's session and read/modify their data.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 863 cwe_View_ID: 1000 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 863 cwe_View_ID: 1003 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 863 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
Access Control	Bypass Protection Mechanism	Access control checks for specific user data or functionality can be bypassed.
Access Control	Gain Privileges or Assume Identity	Horizontal escalation of privilege is possible (one user can view/modify information of another user).
Access Control	Gain Privileges or Assume Identity	Vertical escalation of privilege is possible if the user-controlled key is actually a flag that indicates administrator status, allowing the attacker to gain administrative access.

可能的缓解方案

Architecture and Design

策略:

For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.

['Architecture and Design', 'Implementation']

策略:

Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.

Architecture and Design

策略:

Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.

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