🛡️ Sentinel: [HIGH] Fix SSRF bypass via HTTP redirects in url_upload

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/api/url_upload.py

@@ -106,6 +106,25 @@ def validate_file_type(content_type: str, filename: str) -> bool:
     return False
 
 
+async def verify_redirect(response: httpx.Response) -> None:
+    """
+    Event hook to intercept redirects and validate the new destination URL.
+    Prevents SSRF bypasses via redirects to internal networks or metadata endpoints.
+    """
+    if response.status_code in (301, 302, 303, 307, 308):
+        location = response.headers.get("Location")
+        if location:
+            # Resolve relative redirects
+            new_url = str(response.url.join(location))
+            # Validate the new URL
+            try:
+                validate_url_safety(new_url)
+            except HTTPException as e:
+                # Map the validation error to an httpx exception so it can be handled
+                # properly by the caller, avoiding raw HTTPExceptions escaping the client scope
+                raise httpx.RequestError(f"Redirect to unsafe URL blocked: {e.detail}", request=response.request) from e
+
+
 @router.post("/process-url")
 @require_login
 async def process_url(
@@ -165,6 +184,7 @@ async def process_url(
             headers={
                 "User-Agent": "DocuElevate/1.0",  # Identify ourselves
             },
+            event_hooks={"response": [verify_redirect]},
         ) as client:
             async with client.stream("GET", url) as response:
                 response.raise_for_status()