CWE-331 信息熵不充分
Insufficient Entropy
结构: Simple
Abstraction: Base
状态: Draft
被利用可能性: unkown
基本描述
The software uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others.
相关缺陷
-
cwe_Nature: ChildOf cwe_CWE_ID: 330 cwe_View_ID: 1000 cwe_Ordinal: Primary
-
cwe_Nature: ChildOf cwe_CWE_ID: 330 cwe_View_ID: 1003 cwe_Ordinal: Primary
-
cwe_Nature: ChildOf cwe_CWE_ID: 330 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', 'Other'] | ['Bypass Protection Mechanism', 'Other'] | An attacker could guess the random numbers generated and could gain unauthorized access to a system if the random numbers are used for authentication and authorization. |
可能的缓解方案
Implementation
策略:
Determine the necessary entropy to adequately provide for randomness and predictability. This can be achieved by increasing the number of bits of objects such as keys and seeds.
示例代码
例
This code generates a unique random identifier for a user's session.
bad PHP
return rand();
}
Because the seed for the PRNG is always the user's ID, the session ID will always be the same. An attacker could thus predict any user's session ID and potentially hijack the session.
This example also exhibits a Small Seed Space (CWE-339).
例
The following code uses a statistical PRNG to create a URL for a receipt that remains active for some period of time after a purchase.
bad Java
ranGen.setSeed((new Date()).getTime());
return(baseUrl + ranGen.nextInt(400000000) + ".html");
}
This code uses the Random.nextInt() function to generate "unique" identifiers for the receipt pages it generates. Because Random.nextInt() is a statistical PRNG, it is easy for an attacker to guess the strings it generates. Although the underlying design of the receipt system is also faulty, it would be more secure if it used a random number generator that did not produce predictable receipt identifiers, such as a cryptographic PRNG.
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 | Insufficient Entropy | ||
| WASC | 11 | Brute Force | |
| CERT C Secure Coding | MSC32-C | Exact | Properly seed pseudorandom number generators |
相关攻击模式
- CAPEC-59
引用
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