CkSKILLS: Skill for Claude Code

.agents/skills/ssrf-internal-network/SKILL.md

ssrf-internal-network is a skill for Claude Code, Codex from zhaji2333/CkSKILLS. It costs 89 tokens per session (1,180 once invoked), scanned C, original, MIT.

A security guide for testing server-side request forgery (SSRF), where a server can be tricked into requesting attacker-chosen URLs.

In plain words
What is it for?
Use it during authorized testing of crawlers, proxies, previews, webhooks, callbacks, QR-code tools, online unpackers, and media or document processors.
Why use it?
It helps uncover access to internal services, cloud metadata, private files, or administrative systems through URL-fetching features.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

This is zhaji2333/CkSKILLS's own configuration. It tells Claude Code and Codex how to work on CkSKILLS itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything CkSKILLS configures →

Reuse

Borrowing it

Nothing to install: this file belongs to zhaji2333/CkSKILLS. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/zhaji2333/CkSKILLS/main/.agents/skills/ssrf-internal-network/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/zhaji2333/CkSKILLS

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for ssrf-internal-network

README.md
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Your own site
<a href="https://agentmods.dev/skills/zhaji2333/ckskills/ssrf-internal-network"><img src="https://agentmods.dev/badge/skills/zhaji2333/ckskills/ssrf-internal-network/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for ssrf-internal-network

Your own site · 80×15
<a href="https://agentmods.dev/skills/zhaji2333/ckskills/ssrf-internal-network"><img src="https://agentmods.dev/badge/skills/zhaji2333/ckskills/ssrf-internal-network.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 89 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,180 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00089 $0.01180
Opus 5.5 $0.00036 $0.00472
Sonnet 5.5 $0.00018 $0.00236
Haiku 4.5 $0.00009 $0.00118

Measured 1mo ago against content hash 4c9cc8a70733, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade C, and why

ssrf-internal-network scanned grade C with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Cloud metadata endpointhighServer-side request forgery

One request to 169.254.169.254 can return temporary IAM credentials.

AWS: http://169.254.169.254/latest/meta-data/
.agents/skills/ssrf-internal-network/SKILL.md · 81 lines

What it actually says

ssrf-internal-network — SSRF 与内网横向专项深度挖掘

何时调用(触发条件)

  • 请求中存在 URL 参数(url、link、img、redirect、callback、webhook、notify_url)
  • 服务端抓取/代理/转发功能(爬虫、采集、预览、转码)
  • 回调类功能(支付回调、Webhook 配置、回调验证)
  • 二维码/短链生成、在线解压(远程 URL)
  • 图片/文档/音视频在线预览

一、SSRF 场景清单

场景 漏洞类型 挖掘要点
二维码生成 SSRF/XSS/钓鱼 URL参数可控、二维码内容可控
短链服务 重定向/SSRF/遍历 短链可预测、目标URL可控
代理/转发服务 SSRF/内网穿透 目标地址可控、协议可控
爬虫/采集功能 SSRF/RCE 采集URL可控、解析引擎漏洞
在线预览(文档/代码) SSRF/XSS/RCE 远程URL加载、渲染引擎漏洞
模板/报表生成 SSTI/任意文件读取 用户输入进入模板引擎
Webhook/回调配置 SSRF/信息泄露 回调URL可控、内网探测
文件预览(PDF/Office) SSRF/XXE/RCE 远程URL加载、OLE对象
图片处理 SSRF url:协议(ImageMagick)
视频/音频处理 SSRF/文件读取 concat协议、HLS playlist(FFmpeg)

二、云元数据(打内网核心)

AWS:     http://169.254.169.254/latest/meta-data/
阿里云:  http://100.100.100.200/latest/meta-data/
腾讯云:  http://metadata.tencentyun.com/latest/meta-data/

目标:获取临时凭证(IAM Role)、实例元数据、网络配置,进一步接管云资产。

三、内网探测思路

  1. 先验证可控性:请求外网可控地址(Burp Collaborator / DNSLog / 自己的 VPS)确认请求发出
  2. 内网网段探测:扫描 127.0.0.1、10.x、172.16-31.x、192.168.x 常见端口
  3. Redis 未授权:gopher:// 写入 crontab/SSH key/主从复制 RCE
  4. 管理面板:内网 Jenkins/ES/Grafana/MySQL 等
  5. 协议利用:
    file:///etc/passwd
    gopher://127.0.0.1:6379/_<redis命令>
    dict://127.0.0.1:6379/info
    
  6. DNS 重绑定:注册域名解析到 127.0.0.1/内网 IP,绕过 IP 校验
  7. 重定向绕过:302 跳转至内网/云元数据,绕过 URL 白名单

四、绕过技术

  • IP 混淆:十进制/十六进制/八进制(2130706433、0x7f000001、0177.0.0.1)
  • 短域名/URL 解析差异(http://[email protected])
  • 重定向(http://evil.com/redirect?to=169.254.169.254)
  • DNS 重绑定
  • 编码(双重 URL 编码、Unicode)
  • 协议差异(代理与后端解析不一致)

五、验证要点

  • 先证明出网(DNSLog 外带),再证明内网可达
  • 云元数据:能读取即为严重(临时凭证可能接管云账号)
  • 内网 Redis/数据库:未授权可交互即为严重
  • 响应差异:端口开放/关闭、服务指纹、错误信息
  • 报告标注:网络位置、出网方向、可达内网网段

六、修复建议

  • URL 白名单(协议+域名+端口),禁止私网地址
  • 禁用重定向跟随、禁用危险协议(file/gopher/dict)
  • DNS 解析后二次校验 IP,防 DNS 重绑定
  • 出口流量隔离、最小权限网络策略
  • 云元数据服务:IMDSv2 + 限制访问
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago First seen · 81 lines · 89 tokens per session scan C 4c9cc8a70733

Subscribe to this mod's changes

ssrf-internal-network is a skill published in the GitHub repository zhaji2333/CkSKILLS (126 stars, last pushed 1mo ago), licensed MIT. It adds 89 tokens to every session and 1,180 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it C with 1 finding (cloud metadata endpoint). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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