Associate GgpSignature with GpgKeySubkey if comes from a subkey

Additionally we're delegating missing method calls on GpgKeySubkey to
GpgKey since most of the info required when verifying a signature is
found on GpgKey which is the parent of GpgKeySubkey

app/models/gpg_key.rb

@@ -40,17 +40,6 @@ class GpgKey < ActiveRecord::Base
   after_commit :update_invalid_gpg_signatures, on: :create
   after_create :generate_subkeys
 
-  def self.find_with_subkeys(fingerprint)
-    keys_table = arel_table
-    subkeys_table = GpgKeySubkey.arel_table
-
-    condition = keys_table[:primary_keyid].eq(fingerprint).or(
-      subkeys_table[:keyid].eq(fingerprint)
-    )
-
-    joins(:subkeys).where(condition).first
-  end
-
   def primary_keyid
     super&.upcase
   end

app/models/gpg_key_subkey.rb

 class GpgKeySubkey < ActiveRecord::Base
+  include ShaAttribute
+
+  sha_attribute :keyid
+  sha_attribute :fingerprint
+
   belongs_to :gpg_key
+
+  def method_missing(m, *a, &b)
+    return super unless gpg_key.respond_to?(m)
+
+    gpg_key.public_send(m, *a, &b) # rubocop:disable GitlabSecurity/PublicSend
+  end
+
+  def respond_to_missing?(method, include_private = false)
+    gpg_key.respond_to?(method, include_private) || super
+  end
 end

app/models/gpg_signature.rb

@@ -15,11 +15,27 @@ class GpgSignature < ActiveRecord::Base
 
   belongs_to :project
   belongs_to :gpg_key
+  belongs_to :gpg_key_subkey
 
   validates :commit_sha, presence: true
   validates :project_id, presence: true
   validates :gpg_key_primary_keyid, presence: true
 
+  def gpg_key=(model)
+    case model
+    when GpgKey       then super
+    when GpgKeySubkey then write_attribute(:gpg_key_subkey_id, model.id)
+    end
+  end
+
+  def gpg_key
+    if gpg_key_id
+      super
+    elsif gpg_key_subkey_id
+      gpg_key_subkey
+    end
+  end
+
   def gpg_key_primary_keyid
     super&.upcase
   end

db/migrate/20170927232658_add_gpg_key_subkey_id_to_gpg_signatures.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddGpgKeySubkeyIdToGpgSignatures < ActiveRecord::Migration
+  DOWNTIME = false
+
+  def change
+    add_reference(:gpg_signatures, :gpg_key_subkey, index: true, foreign_key: { on_delete: :nullify })
+  end
+end

db/schema.rb

@@ -610,11 +610,13 @@ ActiveRecord::Schema.define(version: 20171004121444) do
     t.text "gpg_key_user_name"
     t.text "gpg_key_user_email"
     t.integer "verification_status", limit: 2, default: 0, null: false
+    t.integer "gpg_key_subkey_id"
   end
 
   add_index "gpg_signatures", ["commit_sha"], name: "index_gpg_signatures_on_commit_sha", unique: true, using: :btree
   add_index "gpg_signatures", ["gpg_key_id"], name: "index_gpg_signatures_on_gpg_key_id", using: :btree
   add_index "gpg_signatures", ["gpg_key_primary_keyid"], name: "index_gpg_signatures_on_gpg_key_primary_keyid", using: :btree
+  add_index "gpg_signatures", ["gpg_key_subkey_id"], name: "index_gpg_signatures_on_gpg_key_subkey_id", using: :btree
   add_index "gpg_signatures", ["project_id"], name: "index_gpg_signatures_on_project_id", using: :btree
 
   create_table "identities", force: :cascade do |t|
@@ -1736,6 +1738,7 @@ ActiveRecord::Schema.define(version: 20171004121444) do
   add_foreign_key "forked_project_links", "projects", column: "forked_to_project_id", name: "fk_434510edb0", on_delete: :cascade
   add_foreign_key "gpg_key_subkeys", "gpg_keys", on_delete: :cascade
   add_foreign_key "gpg_keys", "users", on_delete: :cascade
+  add_foreign_key "gpg_signatures", "gpg_key_subkeys", on_delete: :nullify
   add_foreign_key "gpg_signatures", "gpg_keys", on_delete: :nullify
   add_foreign_key "gpg_signatures", "projects", on_delete: :cascade
   add_foreign_key "issue_assignees", "issues", name: "fk_b7d881734a", on_delete: :cascade

lib/gitlab/gpg/commit.rb

@@ -43,7 +43,7 @@ module Gitlab
           # key belonging to the keyid.
           # This way we can add the key to the temporary keychain and extract
           # the proper signature.
-          gpg_key = GpgKey.find_with_subkeys(verified_signature.fingerprint)
+          gpg_key = find_gpg_key(verified_signature.fingerprint)
 
           if gpg_key
             Gitlab::Gpg::CurrentKeyChain.add(gpg_key.key)
@@ -74,7 +74,7 @@ module Gitlab
           commit_sha: @commit.sha,
           project: @commit.project,
           gpg_key: gpg_key,
-          gpg_key_primary_keyid: gpg_key&.primary_keyid || verified_signature.fingerprint,
+          gpg_key_primary_keyid: gpg_keyid(gpg_key) || verified_signature.fingerprint,
           gpg_key_user_name: user_infos[:name],
           gpg_key_user_email: user_infos[:email],
           verification_status: verification_status
@@ -98,6 +98,16 @@ module Gitlab
       def user_infos(gpg_key)
         gpg_key&.verified_user_infos&.first || gpg_key&.user_infos&.first || {}
       end
+
+      def gpg_keyid(gpg_key)
+        return nil unless gpg_key
+
+        gpg_key.is_a?(GpgKey) ? gpg_key.primary_keyid : gpg_key.keyid
+      end
+
+      def find_gpg_key(keyid)
+        GpgKey.find_by(primary_keyid: keyid) || GpgKeySubkey.find_by(keyid: keyid)
+      end
     end
   end
 end