CWE-916 使用具有不充分计算复杂性的口令哈希

Use of Password Hash With Insufficient Computational Effort

结构: Simple

Abstraction: Base

状态: Incomplete

被利用可能性: unkown

基本描述

The software generates a hash for a password, but it uses a scheme that does not provide a sufficient level of computational effort that would make password cracking attacks infeasible or expensive.

扩展描述

Many password storage mechanisms compute a hash and store the hash, instead of storing the original password in plaintext. In this design, authentication involves accepting an incoming password, computing its hash, and comparing it to the stored hash.

Many hash algorithms are designed to execute quickly with minimal overhead, even cryptographic hashes. However, this efficiency is a problem for password storage, because it can reduce an attacker's workload for brute-force password cracking. If an attacker can obtain the hashes through some other method (such as SQL injection on a database that stores hashes), then the attacker can store the hashes offline and use various techniques to crack the passwords by computing hashes efficiently. Without a built-in workload, modern attacks can compute large numbers of hashes, or even exhaust the entire space of all possible passwords, within a very short amount of time, using massively-parallel computing (such as cloud computing) and GPU, ASIC, or FPGA hardware. In such a scenario, an efficient hash algorithm helps the attacker.

There are several properties of a hash scheme that are relevant to its strength against an offline, massively-parallel attack:

Note that the security requirements for the software may vary depending on the environment and the value of the passwords. Different schemes might not provide all of these properties, yet may still provide sufficient security for the environment. Conversely, a solution might be very strong in preserving one property, which still being very weak for an attack against another property, or it might not be able to significantly reduce the efficiency of a massively-parallel attack.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 327 cwe_View_ID: 1000 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 327 cwe_View_ID: 1003 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 327 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', 'Gain Privileges or Assume Identity']	If an attacker can gain access to the hashes, then the lack of sufficient computational effort will make it easier to conduct brute force attacks using techniques such as rainbow tables, or specialized hardware such as GPUs, which can be much faster than general-purpose CPUs for computing hashes.

检测方法

Automated Static Analysis - Binary or Bytecode

Manual Static Analysis - Binary or Bytecode

Manual Static Analysis - Source Code

Automated Static Analysis - Source Code

Automated Static Analysis

Architecture or Design Review

可能的缓解方案

MIT-51 Architecture and Design

策略:

Use an adaptive hash function that can be configured to change the amount of computational effort needed to compute the hash, such as the number of iterations ("stretching") or the amount of memory required. Some hash functions perform salting automatically. These functions can significantly increase the overhead for a brute force attack compared to intentionally-fast functions such as MD5. For example, rainbow table attacks can become infeasible due to the high computing overhead. Finally, since computing power gets faster and cheaper over time, the technique can be reconfigured to increase the workload without forcing an entire replacement of the algorithm in use.
Some hash functions that have one or more of these desired properties include bcrypt [REF-291], scrypt [REF-292], and PBKDF2 [REF-293]. While there is active debate about which of these is the most effective, they are all stronger than using salts with hash functions with very little computing overhead.
Note that using these functions can have an impact on performance, so they require special consideration to avoid denial-of-service attacks. However, their configurability provides finer control over how much CPU and memory is used, so it could be adjusted to suit the environment's needs.

MIT-25 ['Implementation', 'Architecture and Design']

策略:

When using industry-approved techniques, use them correctly. Don't cut corners by skipping resource-intensive steps (CWE-325). These steps are often essential for preventing common attacks.

分析过的案例

标识	说明	链接
CVE-2008-1526	Router does not use a salt with a hash, making it easier to crack passwords.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-1526
CVE-2006-1058	Router does not use a salt with a hash, making it easier to crack passwords.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-1058
CVE-2008-4905	Blogging software uses a hard-coded salt when calculating a password hash.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-4905
CVE-2002-1657	Database server uses the username for a salt when encrypting passwords, simplifying brute force attacks.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-1657
CVE-2001-0967	Server uses a constant salt when encrypting passwords, simplifying brute force attacks.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2001-0967
CVE-2005-0408	chain: product generates predictable MD5 hashes using a constant value combined with username, allowing authentication bypass.	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-0408

相关攻击模式

• CAPEC-55

引用

• REF-291 bcrypt

• REF-292 Tarsnap - The scrypt key derivation function and encryption utility

• REF-293 RFC2898 - PKCS #5: Password-Based Cryptography Specification Version 2.0

• REF-294 How To Safely Store A Password

• REF-295 How Companies Can Beef Up Password Security (interview with Thomas H. Ptacek)

• REF-296 Password security: past, present, future

• REF-297 Our password hashing has no clothes

• REF-298 Should we really use bcrypt/scrypt?

• REF-636 Speed Hashing

• REF-631 Password Storage Cheat Sheet

• REF-632 Enough With The Rainbow Tables: What You Need To Know About Secure Password Schemes

• REF-908 Password hashing at scale

• REF-909 New developments in password hashing: ROM-port-hard functions

• REF-633 The Importance of Being Canonical

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