flawopen.com/ssrf/Rust

● CWE-918 · 高危
安全研究 · FlawOpen

漏洞深度剖析：Server-Side Request Forgery in Rust

How reqwest allows internal network queries in Rust, and how to validate resolved socket addresses before connecting.

💡 通俗易懂的原理解析 (ELI5)

想象一下，你派办公室助理去公共快递站取包裹，却故意给他留了总经理办公室带锁保险箱的内部地址。因为助理佩戴着公司内部通行工牌，保安直接放行，他便打开保险箱将公司核心机密交给了你。

核心概念与专有名词

Web Application Security
技术概念 (Web Application Security)：Core architecture component affected by CWE-918.
CWE-918
技术概念 (CWE-918)：Standard Common Weakness Enumeration classification for ssrf-rust.
Defense-in-Depth
技术概念 (Defense-in-Depth)：Multi-layered engineering verification and runtime boundary isolation.

攻击执行流程分解

Step 1

接收不可信远程 URL

应用程序接受用户提交的外部 URL 用于拉取头像、Webhook 推送或生成网页预览。

Step 2

指向内部专用网络与元数据服务

攻击者输入指向内网回环地址或云厂商元数据接口（如 http://169.254.169.254/latest/meta-data/）的地址。

Step 3

未受限制的内部网络套接字请求

服务器内部 HTTP 客户端直接从受信任的私有 VPC 发起网络请求，未做 IP 白名单与私有地址段校验。

Step 4

云身份凭证与敏感数据外泄

内部元数据服务信任来自同主机的请求，回传临时 IAM 访问凭据、Kubernetes Token 或管理后台内容。

源代码对比：漏洞与安全实现

✕ 存在漏洞的实现
// VULNERABLE: Unchecked reqwest::get
use reqwest;

async fn fetch_remote_resource(user_url: &str) -> Result<Vec<u8>, reqwest::Error> {
    // Attacker passes: http://169.254.169.254/latest/meta-data/
    let resp = reqwest::get(user_url).await?;
    let bytes = resp.bytes().await?;
    Ok(bytes.to_vec())
}
✓ 加固后的安全修复
// HARDENED: Resolve DNS, assert non-private IP, and disable redirects
use std::net::{IpAddr, ToSocketAddrs};
use reqwest::redirect::Policy;
use url::Url;

fn is_safe_ip(ip: IpAddr) -> bool {
    match ip {
        IpAddr::V4(ipv4) => {
            !ipv4.is_loopback() &&
            !ipv4.is_private() &&
            !ipv4.is_link_local() &&
            !ipv4.is_unspecified()
        }
        IpAddr::V6(ipv6) => {
            !ipv6.is_loopback() &&
            !ipv6.is_unspecified()
        }
    }
}

async fn fetch_remote_resource(user_url: &str) -> Result<Vec<u8>, Box<dyn std::error::Error>> {
    let parsed_url = Url::parse(user_url)?;
    if parsed_url.scheme() != "http" && parsed_url.scheme() != "https" {
        return Err("Invalid URL scheme".into());
    }
    
    let host = parsed_url.host_str().ok_or("Missing host")?;
    let port = parsed_url.port_or_known_default().unwrap_or(80);
    
    // 1. Resolve host and inspect all IP addresses
    let socket_addrs: Vec<_> = format!("{}:{}", host, port).to_socket_addrs()?.collect();
    for sa in &socket_addrs {
        if !is_safe_ip(sa.ip()) {
            return Err("Access to private/internal IP rejected".into());
        }
    }
    
    // 2. Build client with redirects disabled
    let client = reqwest::Client::builder()
        .redirect(Policy::none())
        .timeout(std::time::Duration::from_secs(3))
        .build()?;
        
    let resp = client.get(parsed_url).send().await?;
    let bytes = resp.bytes().await?;
    Ok(bytes.to_vec())
}

工程与系统安全加固清单

References