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Use when building features that fetch URLs or make HTTP requests based on user-supplied input — web scrapers, webhook receivers, URL preview services, import-from-URL features, or any server-side HTTP client.
默认使用会先检查来源的 Prompt；你也可以切换为直接命令，或下载本地副本。
决定是否安装前，请先阅读 SKILL.md，以及 SkillsMP 当前展示的配套文件。
用 Codex 或 Claude 帮你安装 复制这段 Prompt，粘贴到 Codex、Claude 或其他助手里，让它检查 Skill 页面并帮你完成安装。
直接命令不会经过审查 Prompt；运行前请先检查来源。
npx skills add https://github.com/jeffreytse/grimoire-core --skill prevent-ssrf命令会保持在同一行。复制前请横向滚动并检查完整内容。
想先保存到本地？可下载 SkillsMP 当前能够提供的文件。
Use when comparing very differently-titled roles for compensation banding, leveling, or organizational design — score each role's inherent Know-How (knowledge, skills, experience required), Problem Solving (complexity and freedom of thinking, scored as a percentage of Know-How), and Accountability (freedom to act and magnitude of impact), because job titles and informal seniority perceptions vary inconsistently across departments and don't provide a comparable basis on their own.
Use when many people request your scarce time, mentorship, or expertise and you cannot evaluate their genuine commitment level from a conversation alone — require a specific, costly, objectively verifiable unit of self-directed output (a set number of completed attempts) before engaging, because genuine commitment is what a conversation cannot reliably reveal but a completed, verifiable body of work can.
Use when deciding how to allocate a manager's or leader's limited time across competing activities — before defaulting to whatever is most urgent, estimate each candidate activity's leverage (how many people's output it affects, for how long, and whether it requires your specific position), because a manager's actual output is the output of the organization under their influence, not their own individual task completion.
基于 SOC 职业分类
正在显示 SKILL.md
| name | prevent-ssrf |
| description | Use when building features that fetch URLs or make HTTP requests based on user-supplied input — web scrapers, webhook receivers, URL preview services, import-from-URL features, or any server-side HTTP client. |
| source | OWASP Server-Side Request Forgery Prevention Cheat Sheet (owasp.org/www-project-cheat-sheets); OWASP Top 10 2021 A10; CWE-918 |
| tags | ["security","owasp","ssrf","server-side-request-forgery","web","developer","cloud"] |
Block server-side request forgery by validating and allowlisting URLs before making server-side HTTP requests — preventing attackers from using your server as a proxy to reach internal metadata endpoints, databases, or cloud infrastructure.
Adopted by: OWASP added SSRF as its own category in Top 10 2021 (A10) due to increasing severity in cloud environments. AWS, GCP, and Azure now offer IMDS v2 (token-required metadata endpoints) specifically to mitigate SSRF. Google exposed $31,337 in SSRF bug bounties. Capital One's 2019 breach (100M records) was executed entirely via SSRF exploiting AWS EC2 metadata at 169.254.169.254.
Impact: In cloud environments, SSRF can reach the instance metadata service (IMDS) and retrieve IAM credentials, enabling full cloud account takeover without any direct database access. Capital One breach (2019) affected 100M+ records via a WAF SSRF vulnerability. Netflix, GitLab, and Shopify have all paid significant SSRF bug bounties. In containerized environments, SSRF can reach Kubernetes API servers on internal networks.
Why best: Denylist-based approaches (blocking 169.254.169.254, localhost, 127.0.0.1) fail because attackers bypass them with DNS rebinding, IPv6 addresses (::1, ::ffff:127.0.0.1), decimal encoding (2130706433 = 127.0.0.1), or redirects. Allowlist-based validation (permitting only known external domains) is the only reliable defense.
Sources: OWASP SSRF Prevention Cheat Sheet; Capital One breach report (2019); AWS IMDS v2 documentation; CWE-918
Use an allowlist of approved URL patterns — define which domains/URLs your feature should reach:
ALLOWED_DOMAINS = {'api.example.com', 'uploads.example.com', 'cdn.partner.com'}
from urllib.parse import urlparse
import ipaddress
def validate_url(url):
parsed = urlparse(url)
if parsed.scheme not in ('http', 'https'):
raise ValueError("Only HTTP/HTTPS allowed")
hostname = parsed.hostname
if hostname not in ALLOWED_DOMAINS:
raise ValueError(f"Domain not allowed: {hostname}")
return url
Block all private and link-local IP ranges after DNS resolution — resolve the hostname and check the resulting IP, not just the domain name:
import socket
import ipaddress
BLOCKED_RANGES = [
ipaddress.ip_network('10.0.0.0/8'),
ipaddress.ip_network('172.16.0.0/12'),
ipaddress.ip_network('192.168.0.0/16'),
ipaddress.ip_network('127.0.0.0/8'),
ipaddress.ip_network('169.254.0.0/16'), # AWS/GCP/Azure IMDS
ipaddress.ip_network('::1/128'),
ipaddress.ip_network('fc00::/7'),
]
def is_safe_ip(hostname):
try:
ip = ipaddress.ip_address(socket.gethostbyname(hostname))
except (socket.gaierror, ValueError):
(ip net net BLOCKED_RANGES)
http://169.254.169.254 will bypass hostname-only checks.file:///etc/passwd) and other non-HTTP schemes must be blocked explicitly.if '169.254' in url is bypassed by http://0251.0376.0251.0376/ (octal encoding).Prevent DNS rebinding — resolve DNS once and use the resolved IP for the actual connection:
import requests
from requests.adapters import HTTPAdapter
class SSRFSafeAdapter(HTTPAdapter):
def send(self, request, **kwargs):
# Resolve and validate before sending
hostname = urlparse(request.url).hostname
if not is_safe_ip(hostname):
raise SecurityError("Blocked SSRF attempt")
return super().send(request, **kwargs)
session = requests.Session()
session.mount('http://', SSRFSafeAdapter())
session.mount('https://', SSRFSafeAdapter())
Disable HTTP redirects, or re-validate after each redirect:
# Option A: disable redirects entirely
response = requests.get(url, allow_redirects=False)
# Option B: validate each redirect destination
def safe_get(url, max_redirects=3):
for _ in range(max_redirects):
resp = requests.get(url, allow_redirects=False)
if resp.is_redirect:
url = resp.headers['Location']
validate_url(url) # re-validate the redirect target
else:
return resp
raise SecurityError("Too many redirects")
In cloud environments, enforce IMDS v2 — IMDSv2 requires a PUT request to obtain a token before accessing metadata. Even if SSRF reaches the endpoint, the attacker cannot get credentials without the token step.
AWS: Set HttpTokens: required on EC2 instance metadata options.
GCP: Block metadata.google.internal via VPC firewall rules.
Azure: Enable IMDS v2 (managed identity with required tokens).
Use an isolated outbound proxy for user-facing fetch features — route all user-driven HTTP requests through a dedicated proxy with strict allowlist enforcement, separate from your internal service traffic. Prevents SSRF from reaching internal microservices.