Add ZeroZeroZeroZero cop

Add a new RuboCop to detect the use of 0.0.0.0 in formulae which
indicates binding to all network interfaces, internally or externally,
so is a bad default and potentially a security risk.

Co-authored-by: Issy Long <me@issylong.com>

Library/Homebrew/rubocops/all.rb

@@ -43,5 +43,6 @@ require_relative "text"
 require_relative "urls"
 require_relative "uses_from_macos"
 require_relative "version"
+require_relative "zero_zero_zero_zero"
 
 require_relative "rubocop-cask"

Library/Homebrew/rubocops/zero_zero_zero_zero.rb

@@ -0,0 +1,48 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "rubocops/extend/formula_cop"
+
+module RuboCop
+  module Cop
+    module FormulaAudit
+      # This cop audits the use of 0.0.0.0 in formulae.
+      # 0.0.0.0 should not be used outside of test do blocks as it can be a security risk.
+      class ZeroZeroZeroZero < FormulaCop
+        sig { override.params(formula_nodes: FormulaNodes).void }
+        def audit_formula(formula_nodes)
+          return if formula_tap != "homebrew-core"
+
+          body_node = formula_nodes.body_node
+          return if body_node.nil?
+
+          test_block = find_block(body_node, :test)
+
+          # Find all string literals in the formula
+          body_node.each_descendant(:str) do |str_node|
+            content = string_content(str_node)
+            next unless content.include?("0.0.0.0")
+            next if test_block && str_node.ancestors.any?(test_block)
+
+            next if valid_ip_range?(content)
+
+            offending_node(str_node)
+            problem "Do not use 0.0.0.0 as it can be a security risk."
+          end
+        end
+
+        private
+
+        sig { params(content: String).returns(T::Boolean) }
+        def valid_ip_range?(content)
+          # Allow private IP ranges like 10.0.0.0, 172.16.0.0-172.31.255.255, 192.168.0.0-192.168.255.255
+          return true if content.match?(/\b(?:10|172\.(?:1[6-9]|2[0-9]|3[01])|192\.168)\.\d+\.\d+\b/)
+          # Allow IP range notation like 0.0.0.0-255.255.255.255
+          return true if content.match?(/\b0\.0\.0\.0\s*-\s*255\.255\.255\.255\b/)
+
+          false
+        end
+      end
+    end
+  end
+end

Library/Homebrew/test/rubocops/zero_zero_zero_zero_spec.rb

@@ -0,0 +1,135 @@
+# frozen_string_literal: true
+
+require "rubocops/zero_zero_zero_zero"
+
+RSpec.describe RuboCop::Cop::FormulaAudit::ZeroZeroZeroZero do
+  subject(:cop) { described_class.new }
+
+  it "reports no offenses when 0.0.0.0 is used inside test do blocks" do
+    expect_no_offenses(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        test do
+          system "echo", "0.0.0.0"
+        end
+      end
+    RUBY
+  end
+
+  it "reports no offenses for valid IP ranges like 10.0.0.0" do
+    expect_no_offenses(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        def install
+          system "echo", "10.0.0.0"
+        end
+      end
+    RUBY
+  end
+
+  it "reports no offenses for IP range notation like 0.0.0.0-255.255.255.255" do
+    expect_no_offenses(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        def install
+          system "echo", "0.0.0.0-255.255.255.255"
+        end
+      end
+    RUBY
+  end
+
+  it "reports no offenses for private IP ranges" do
+    expect_no_offenses(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        def install
+          system "echo", "192.168.1.1"
+          system "echo", "172.16.0.1"
+          system "echo", "10.0.0.1"
+        end
+      end
+    RUBY
+  end
+
+  it "reports no offenses when outside of homebrew-core" do
+    expect_no_offenses(<<~RUBY)
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        service do
+          run [bin/"foo", "--host", "0.0.0.0"]
+        end
+      end
+    RUBY
+  end
+
+  it "reports offenses when 0.0.0.0 is used in service blocks" do
+    expect_offense(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        service do
+          run [bin/"foo", "--host", "0.0.0.0"]
+                                    ^^^^^^^^^ FormulaAudit/ZeroZeroZeroZero: Do not use 0.0.0.0 as it can be a security risk.
+        end
+      end
+    RUBY
+  end
+
+  it "reports offenses when 0.0.0.0 is used outside of test do blocks" do
+    expect_offense(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        def install
+          system "echo", "0.0.0.0"
+                         ^^^^^^^^^ FormulaAudit/ZeroZeroZeroZero: Do not use 0.0.0.0 as it can be a security risk.
+        end
+      end
+    RUBY
+  end
+
+  it "reports offenses for 0.0.0.0 in method definitions outside test blocks" do
+    expect_offense(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        def configure
+          system "./configure", "--bind-address=0.0.0.0"
+                                ^^^^^^^^^^^^^^^^^^^^^^^^ FormulaAudit/ZeroZeroZeroZero: Do not use 0.0.0.0 as it can be a security risk.
+        end
+      end
+    RUBY
+  end
+
+  it "reports multiple offenses when 0.0.0.0 is used in multiple places" do
+    expect_offense(<<~RUBY, "/homebrew-core/")
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        desc "A test formula"
+
+        def install
+          system "echo", "0.0.0.0"
+                         ^^^^^^^^^ FormulaAudit/ZeroZeroZeroZero: Do not use 0.0.0.0 as it can be a security risk.
+        end
+
+        def post_install
+          system "echo", "0.0.0.0"
+                         ^^^^^^^^^ FormulaAudit/ZeroZeroZeroZero: Do not use 0.0.0.0 as it can be a security risk.
+        end
+      end
+    RUBY
+  end
+end