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🛡️ Sentinel: [HIGH] Fix SSRF bypass on DNS resolution failure

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Modified `is_private_ip` in `app/utils/network.py` to fail securely by returning True (blocking the request) when a hostname cannot be resolved. The previous implementation failed open, creating a risk for Server-Side Request Forgery (SSRF) and DNS rebinding attacks.

Updated corresponding tests to expect the secure behavior and correctly appended the security finding to the Sentinel journal.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
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google-labs-jules[bot]
2026-03-23 15:25:53 +00:00
parent ef897f660d
commit 06b0fced38
4 changed files with 24 additions and 7 deletions
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**Vulnerability:** The `_test_webdav_connection` function used `urllib.request.urlopen`, which natively supports dangerous schemes like `file://` or `ftp://` and follows redirects by default, potentially allowing SSRF bypasses or Local File Inclusion.
**Learning:** `urllib.request` should be avoided for user-supplied URLs. Even when URL schemes are manually validated, `urllib`'s default redirect following behavior can bypass SSRF protections (e.g. redirecting to `127.0.0.1`).
**Prevention:** Use a modern, safer HTTP client like `httpx` with `follow_redirects=False` when testing user-provided URLs.
## 2025-05-18 - [SSRF Bypass via DNS Resolution Failure]
**Vulnerability:** The `is_private_ip` function in `app/utils/network.py` failed open (returned `False`) when a hostname could not be resolved (`socket.gaierror`).
**Learning:** This fail-open pattern was originally added to allow external domains in tests, but in production, it created a severe SSRF risk. An attacker could bypass SSRF protections by providing a URL that fails to resolve during the security check but resolves later (DNS rebinding), or by exploiting internal routing behaviors via unresolvable addresses.
**Prevention:** Always fail securely in network authorization functions. If a domain cannot be resolved to verify its safety, the request must be blocked (`return True` / default-deny). Tests should mock DNS resolution correctly instead of compromising production security logic.