Rubocop redundant module info keys

[sjanusz-r7]

Description

Closes #21606
This PR adds a RuboCop rule to help contributors with the redundant metadata that is often copy-pasted in the module metadata hash (arch and platform), if the Targets already has them defined.

Related work: #20786

This should follow the already-existing code conventions for other rubocop rules.

Potential scenarios

Some 'mock' module metadata, that you can store as a file and run rubocop against:

# frozen_string_literal: true

# BAD: Arch is redundant because all targets define it
class MetasploitModule < Msf::Exploit::Remote
  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Bad Example - Redundant Arch',
        'Description' => %q{
          This fake module demonstrates a redundant top-level Arch.
          Every target already specifies Arch, so the top-level value is unnecessary.
        },
        'Author' => ['Test Author'],
        'License' => MSF_LICENSE,
        'Platform' => 'win',
        'Arch' => ARCH_X86,
        'Targets' => [
          ['Windows x86', { 'Arch' => ARCH_X86 }],
          ['Windows x64', { 'Arch' => ARCH_X64 }]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2025-01-01',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS],
          'Reliability' => [REPEATABLE_SESSION]
        }
      )
    )
  end
end
# frozen_string_literal: true

# BAD: Both Arch and Platform are redundant because all targets define them
class MetasploitModule < Msf::Exploit::Remote
  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Bad Example - Redundant Arch and Platform',
        'Description' => %q{
          This fake module demonstrates redundant top-level Arch AND Platform.
          Every target already specifies both, so neither is needed at the top level.
        },
        'Author' => ['Test Author'],
        'License' => MSF_LICENSE,
        'Platform' => 'win',
        'Arch' => [ARCH_X86, ARCH_X64],
        'Targets' => [
          ['Windows x86', { 'Platform' => 'win', 'Arch' => ARCH_X86 }],
          ['Windows x64', { 'Platform' => 'win', 'Arch' => ARCH_X64 }],
          ['Windows ARM', { 'Platform' => 'win', 'Arch' => ARCH_AARCH64 }]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2025-01-01',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS],
          'Reliability' => [REPEATABLE_SESSION]
        }
      )
    )
  end
end
# frozen_string_literal: true

# BAD: Platform is redundant because all targets define it
class MetasploitModule < Msf::Exploit::Remote
  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Bad Example - Redundant Platform',
        'Description' => %q{
          This fake module demonstrates a redundant top-level Platform.
          Every target already specifies Platform, so the top-level value is unnecessary.
        },
        'Author' => ['Test Author'],
        'License' => MSF_LICENSE,
        'Platform' => 'win',
        'Targets' => [
          ['Windows x86', { 'Platform' => 'win', 'Arch' => ARCH_X86 }],
          ['Windows x64', { 'Platform' => 'win', 'Arch' => ARCH_X64 }]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2025-01-01',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS],
          'Reliability' => [REPEATABLE_SESSION]
        }
      )
    )
  end
end
# frozen_string_literal: true

# GOOD: Targets have empty hashes, so top-level Arch/Platform provide the values
class MetasploitModule < Msf::Exploit::Remote
  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Good Example - Empty Target Hashes',
        'Description' => %q{
          This fake module has targets with empty option hashes. The top-level
          Arch and Platform are needed as the fallback for all targets.
        },
        'Author' => ['Test Author'],
        'License' => MSF_LICENSE,
        'Arch' => [ARCH_X86, ARCH_X64],
        'Platform' => 'win',
        'Targets' => [
          ['Automatic', {}],
          ['Manual', {}]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2026-01-01',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS],
          'Reliability' => [REPEATABLE_SESSION]
        }
      )
    )
  end
end
# frozen_string_literal: true

# GOOD: No Targets defined, so top-level Arch/Platform are the only source of truth
class MetasploitModule < Msf::Exploit::Remote
  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Good Example - No Targets',
        'Description' => %q{
          This fake module has no Targets at all, so the top-level Arch and
          Platform are required and should not trigger any offence.
        },
        'Author' => ['Test Author'],
        'License' => MSF_LICENSE,
        'Arch' => ARCH_X86,
        'Platform' => 'win',
        'DisclosureDate' => '2025-01-01',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS],
          'Reliability' => [REPEATABLE_SESSION]
        }
      )
    )
  end
end
# frozen_string_literal: true

# GOOD: Top-level Arch is necessary because not all targets define it
class MetasploitModule < Msf::Exploit::Remote
  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Good Example - Targets Missing Arch',
        'Description' => %q{
          This fake module correctly uses a top-level Arch because one target
          does not override it. Framework falls back to the top-level value.
        },
        'Author' => ['Test Author'],
        'License' => MSF_LICENSE,
        'Arch' => ARCH_X86,
        'Platform' => 'win',
        'Targets' => [
          ['Windows x86', { 'Arch' => ARCH_X86 }],
          ['Automatic', {}]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2026-01-01',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS],
          'Reliability' => [REPEATABLE_SESSION]
        }
      )
    )
  end
end

Breaking Changes

None

Reviewer Notes

Verification Steps

• Run the rspec tests

Test Evidence

➜  metasploit-framework git:(rubocop-redundant-module-info-keys) ✗ bundle exec rspec spec/rubocop/cop/lint/module_redundant_arch_platform_spec.rb  
...
18 examples, 0 failures

AI Usage Disclosure

Claude was used.

Pre-Submission Checklist

• Included a corresponding documentation markdown file in documentation/modules (new modules only)
• No sensitive information (IP addresses, credentials, API keys, hashes) in code or documentation
• Tested on the target environment specified in the Environment section above
• Included RSpec tests for library changes (encouraged for lib/ changes)
• Read the CONTRIBUTING.md and module acceptance guidelines

[cgranleese-r7]

Looks good to me 👍

Tests output:

Finished in 0.1734 seconds (files took 2.98 seconds to load)
18 examples, 0 failures

Example test file output:

❯ rubocop --only Lint/ModuleRedundantArchPlatform modules/rubocop_test_file.rb -A
WARN: Unresolved or ambiguous specs during Gem::Specification.reset:
      stringio (>= 0)
      Available/installed versions of this gem:
      - 3.1.7
      - 3.1.1
WARN: Clearing out unresolved specs. Try 'gem cleanup <gem>'
Please report a bug if this causes problems.
Inspecting 1 file
W

Offenses:

modules/rubocop_test_file.rb:17:9: W: [Corrected] Lint/ModuleRedundantArchPlatform: Remove top-level Arch as it is already defined in all Targets
        'Arch' => ARCH_X86,
        ^^^^^^
modules/rubocop_test_file.rb:48:9: W: [Corrected] Lint/ModuleRedundantArchPlatform: Remove top-level Platform as it is already defined in all Targets
        'Platform' => 'win',
        ^^^^^^^^^^
modules/rubocop_test_file.rb:49:9: W: [Corrected] Lint/ModuleRedundantArchPlatform: Remove top-level Arch as it is already defined in all Targets
        'Arch' => [ARCH_X86, ARCH_X64],
        ^^^^^^
modules/rubocop_test_file.rb:81:9: W: [Corrected] Lint/ModuleRedundantArchPlatform: Remove top-level Platform as it is already defined in all Targets
        'Platform' => 'win',
        ^^^^^^^^^^

1 file inspected, 4 offenses detected, 4 offenses corrected