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🛡️ Sentinel: [HIGH] Fix Server-Side Request Forgery in webhooks

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Adds validation to webhook URLs before attempting to deliver them to prevent
SSRF attacks targeting private IP ranges, local host, and cloud metadata endpoints.
Validates URL schema, hostname, and applies `is_private_ip()`. Also resolved ruff linting
errors. Tests have been expanded to ensure validation covers all cases.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
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google-labs-jules[bot]
2026-05-17 15:04:09 +00:00
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commit 5b41d32f90
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## 2024-05-24 - SSRF in WebDAV connection test
**Vulnerability:** The `_test_webdav_connection` function had a custom SSRF check that failed to resolve DNS names, allowing attackers to bypass the check by providing a domain that resolves to an internal IP (e.g., `127.0.0.1`).
**Learning:** DNS resolution is required for robust SSRF protection when validating URLs provided by users.
**Prevention:** Use a centralized `is_private_ip` function (now in `app/utils/network.py`) that resolves the hostname to its IPs and checks if any are private.
## 2026-03-22 - B310: urllib.request.urlopen replaced with httpx
**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.
## 2026-03-20 - Safe Path Traversal Prevention in Low-Level Utilities
**Vulnerability:** The generic file utility `hash_file` in `app/utils/file_operations.py` accepted any file path and was vulnerable to reading arbitrary files via path traversal (e.g., `../../../etc/passwd`) or absolute paths if an attacker could control the `filepath` argument.
**Learning:** Naively checking for `".." in path` breaks legitimate relative paths used internally by the application. Blocking absolute paths entirely also breaks functionality. Input validation should occur at the API boundary, but for defense-in-depth, low-level utilities must enforce expected boundaries (e.g., the application's `workdir`).
**Prevention:** Use `pathlib.Path.resolve()` on both the target path and the allowed base directory (`settings.workdir`). Ensure the resolved target path is strictly within the allowed boundary using `filepath_obj.relative_to(workdir_obj)`, catching the `ValueError` that is raised when the path is out of bounds. This safely blocks both relative traversal attacks and arbitrary absolute paths.
## 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.
## 2026-03-26 - SSRF in Integration Connection Tests
**Vulnerability:** The `_test_imap_connection` and `_test_s3_connection` functions in `app/api/integrations.py` did not validate user-provided `host` and `endpoint_url` variables against `is_private_ip()`. This allowed an attacker to test the presence of internal IMAP servers or direct S3 SDK API calls to internal infrastructure via SSRF.
**Learning:** Any time a new generic connection or integration test is added, SSRF validation may be forgotten if the core network utility (`is_private_ip`) is not systematically applied to all outbound network operations, regardless of the protocol (e.g., IMAP, S3).
**Prevention:** Establish a pattern where any user-configurable host or endpoint URL is immediately passed through the centralized `is_private_ip` validation function before any network call or third-party client initialization.
## 2024-05-27 - SSRF Bypass via HTTP Redirects
**Vulnerability:** In `app/api/url_upload.py`, the `validate_url_safety` function was correctly verifying the initially requested URL to prevent fetching internal IPs or cloud metadata endpoints. However, the subsequent `httpx.AsyncClient` was configured with `follow_redirects=True` without validating the destination of those redirects. An attacker could bypass SSRF protections by providing a URL to an attacker-controlled server that responds with a 301/302 redirect pointing to an internal target (e.g., `http://127.0.0.1` or `http://169.254.169.254`).
**Learning:** Checking the URL before sending the request is insufficient if the HTTP client automatically follows redirects. The target of every single redirect must be subject to the same strict validation as the initial request.
**Prevention:** Avoid `follow_redirects=True` for user-provided URLs when possible. If redirects must be followed, attach an event hook (e.g., `event_hooks={"response": [hook_function]}`) to the `httpx` client to intercept the response, calculate the redirect destination from the `Location` header, and run the URL safety validation logic before the redirect is actually followed.
## 2026-03-27 - SSRF Bypass via HTTP Redirects in httpx
**Vulnerability:** The `/process-url` endpoint used `httpx.AsyncClient(follow_redirects=True)` after validating the initial user-provided URL against SSRF protections. However, it did not validate the target URLs of any subsequent HTTP redirects, allowing an attacker to provide a safe URL that redirects to an internal/private IP, bypassing the security check.
**Learning:** Initial URL validation is insufficient when the HTTP client is configured to follow redirects automatically. The client must be explicitly configured to validate every redirect target.
**Prevention:** When using `httpx.AsyncClient(follow_redirects=True)` for user-provided URLs, always implement a redirect validator hook function (e.g., using `event_hooks={'response': [validate_redirect]}`) that resolves the `Location` header and passes it through the same SSRF validation logic before the redirect is followed.
## 2025-02-14 - SSRF vulnerability in webhook outgoing requests
**Vulnerability:** Found an SSRF vulnerability where outgoing webhook requests could hit private IPs or metadata endpoints (e.g. 169.254.169.254).
**Learning:** This existed because the `url` parameter provided for webhooks (`app/utils/webhook.py` and `app/utils/user_notification.py`) was not being checked before being passed to `requests.post()` or `httpx.post()`.
**Prevention:** Make sure to always validate URL scheme and hostname with `is_private_ip()` and block known cloud metadata endpoints before doing outgoing network requests based on dynamic values.