CWE-272 最小特权原则违背

Least Privilege Violation

结构: Simple

Abstraction: Base

状态: Incomplete

被利用可能性: unkown

基本描述

The elevated privilege level required to perform operations such as chroot() should be dropped immediately after the operation is performed.

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 271 cwe_View_ID: 1000 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 271 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', 'Confidentiality'] ['Gain Privileges or Assume Identity', 'Read Application Data', 'Read Files or Directories'] An attacker may be able to access resources with the elevated privilege that could not be accessed with the attacker's original privileges. This is particularly likely in conjunction with another flaw, such as a buffer overflow.

检测方法

Automated Static Analysis - Binary or Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:
  • Compare binary / bytecode to application permission manifest

Dynamic Analysis with Automated Results Interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:
  • Host-based Vulnerability Scanners – Examine configuration for flaws, verifying that audit mechanisms work, ensure host configuration meets certain predefined criteria

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:
  • Manual Source Code Review (not inspections)
Cost effective for partial coverage:
  • Focused Manual Spotcheck - Focused manual analysis of source

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:
  • Source code Weakness Analyzer
  • Context-configured Source Code Weakness Analyzer

Automated Static Analysis

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:
  • Permission Manifest Analysis

Architecture or Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:
  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)
  • Formal Methods / Correct-By-Construction
Cost effective for partial coverage:
  • Attack Modeling

可能的缓解方案

MIT-1 ['Architecture and Design', 'Operation']

策略:

Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.

MIT-48 Architecture and Design

策略: Separation of Privilege

Follow the principle of least privilege when assigning access rights to entities in a software system.

MIT-46 Architecture and Design

策略: Separation of Privilege

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design and that the compartmentalization serves to allow for and further reinforce privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide when it is appropriate to use and to drop system privileges.

示例代码

例

The following example demonstrates the weakness.

bad C

setuid(0);
// Do some important stuff
setuid(old_uid);
// Do some non privileged stuff.

bad Java

method() {
AccessController.doPrivileged(new PrivilegedAction()) {
public Object run() {

// Insert all code here
}
};
}

例

The following code calls chroot() to restrict the application to a subset of the filesystem below APP_HOME in order to prevent an attacker from using the program to gain unauthorized access to files located elsewhere. The code then opens a file specified by the user and processes the contents of the file.

bad C

chroot(APP_HOME);
chdir("/");
FILE* data = fopen(argv[1], "r+");
...

Constraining the process inside the application's home directory before opening any files is a valuable security measure. However, the absence of a call to setuid() with some non-zero value means the application is continuing to operate with unnecessary root privileges. Any successful exploit carried out by an attacker against the application can now result in a privilege escalation attack because any malicious operations will be performed with the privileges of the superuser. If the application drops to the privilege level of a non-root user, the potential for damage is substantially reduced.

Notes

Maintenance CWE-271, CWE-272, and CWE-250 are all closely related and possibly overlapping. CWE-271 is probably better suited as a category. Other

分类映射

映射的分类名 ImNode ID Fit Mapped Node Name
7 Pernicious Kingdoms Least Privilege Violation
CLASP Failure to drop privileges when reasonable
CERT C Secure Coding POS02-C Follow the principle of least privilege
The CERT Oracle Secure Coding Standard for Java (2011) SEC00-J Do not allow privileged blocks to leak sensitive information across a trust boundary
The CERT Oracle Secure Coding Standard for Java (2011) SEC01-J Do not allow tainted variables in privileged blocks
Software Fault Patterns SFP36 Privilege

相关攻击模式

  • CAPEC-17
  • CAPEC-35
  • CAPEC-76