🧑‍💻 Improved docs for checksums

Author: pboling

security.md

@@ -119,14 +119,84 @@ Add cert paths to your gemspec
 
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-### Include checksum of released gems in your repository
-
-    require 'digest/sha2'
-    built_gem_path = 'pkg/gemname-version.gem'
-    checksum = Digest::SHA512.new.hexdigest(File.read(built_gem_path))
-    checksum_path = 'checksum/gemname-version.gem.sha512'
-    File.open(checksum_path, 'w' ) {|f| f.write(checksum) }
-    # add and commit 'checksum_path'
+### Include SHA-256 and SHA-512 checksums of released gems in your repository
+
+Checksums can be created when you are ready to release a gem. 
+
+Currently the rake task only creates an SHA-256 checksum. Run:
+
+    rake build:checksum
+
+The checksum will be placed in the `checksums/` directory.  If you track the
+checksums in your source repository, others will be able to verify the 
+authenticity of a release.
+
+Alternatively, if you'd like a script that will create both SHA-256 and SHA-512
+checksums you might use something like the following:
+
+```ruby
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "digest/sha2"
+
+VERSION_REGEX = /\d+\.\d+\.\d+([-.].+)*/.freeze
+
+gem_path_parts = ARGV.first&.split("/")
+
+if gem_path_parts&.any?
+  gem_name = gem_path_parts.last
+  gem_pkg = File.join(gem_path_parts)
+  puts "Looking for: #{gem_pkg.inspect}"
+  gems = Dir[gem_pkg]
+  puts "Found: #{gems.inspect}"
+else
+  gem_pkgs = File.join("pkg", "*.gem")
+  puts "Looking for: #{gem_pkgs.inspect}"
+  gems = Dir[gem_pkgs]
+  raise "Unable to find gems #{gem_pkgs}" if gems.empty?
+
+  # Sort by newest last
+  # [ "my_gem-2.3.9.gem", "my_gem-2.3.11.pre.alpha.4.gem", "my_gem-2.3.15.gem", ... ]
+  gems.sort_by! { |gem| Gem::Version.new(gem[VERSION_REGEX]) }
+  gem_pkg = gems.last
+  gem_path_parts = gem_pkg.split("/")
+  gem_name = gem_path_parts.last
+  puts "Found: #{gems.length} gems; latest is #{gem_name}"
+end
+
+checksum512 = Digest::SHA512.new.hexdigest(File.read(gem_pkg))
+checksum512_path = "checksums/#{gem_name}.sha512"
+File.write(checksum512_path, checksum512)
+
+checksum256 = Digest::SHA256.new.hexdigest(File.read(gem_pkg))
+checksum256_path = "checksums/#{gem_name}.sha256"
+File.write(checksum256_path, checksum256)
+
+version = File.basename(checksum256_path[VERSION_REGEX], ".gem")
+
+git_cmd = <<~GIT_MSG
+git add checksums/* && \
+git commit -m "🔒️ Checksums for v#{version}"
+GIT_MSG
+
+puts <<~RESULTS
+[GEM: #{gem_name}]
+[VERSION: #{version}]
+[CHECKSUM SHA256 PATH: #{checksum256_path}]
+[CHECKSUM SHA512 PATH: #{checksum512_path}]
+
+... Running ...
+
+#{git_cmd}
+RESULTS
+
+# This will replace the current process with the git process, and exit.
+# Any command placed after this will not be run:
+#   See: https://www.akshaykhot.com/call-shell-commands-in-ruby
+exec(git_cmd)
+
+```
 
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