user may now revoke a gpg key

other than just removing a key, which doesn't affect the verified state
of a commit, revoking a key unverifies all signed commits.

app/controllers/profiles/gpg_keys_controller.rb

@@ -25,6 +25,16 @@ class Profiles::GpgKeysController < Profiles::ApplicationController
     end
   end
+  def revoke
+    @gpp_key = current_user.gpg_keys.find(params[:id])
+    @gpp_key.revoke
+
+    respond_to do |format|
+      format.html { redirect_to profile_gpg_keys_url, status: 302 }
+      format.js { head :ok }
+    end
+  end
+
   private
   def gpg_key_params

app/models/gpg_key.rb

@@ -58,6 +58,17 @@ class GpgKey < ActiveRecord::Base
     InvalidGpgSignatureUpdateWorker.perform_async(self.id)
   end
+  def revoke
+    GpgSignature.where(gpg_key: self, valid_signature: true).find_each do |gpg_signature|
+      gpg_signature.update_attributes!(
+        gpg_key: nil,
+        valid_signature: false
+      )
+    end
+
+    destroy
+  end
+
   private
   def extract_fingerprint

app/views/profiles/gpg_keys/_key.html.haml

@@ -3,13 +3,17 @@
     = icon 'key', class: "settings-list-icon hidden-xs"
   .key-list-item-info
     - key.emails_with_verified_status.map do |email, verified|
+      = email
       = verified_email_badge(email, verified)
     .description
-      = key.fingerprint
+      %code= key.fingerprint
   .pull-right
     %span.key-created-at
       created #{time_ago_with_tooltip(key.created_at)}
-    = link_to profile_gpg_key_path(key), data: { confirm: 'Are you sure?' }, method: :delete, class: "btn btn-transparent prepend-left-10" do
+    = link_to profile_gpg_key_path(key), data: { confirm: 'Are you sure? Removing this GPG key does not affect already signed commits.' }, method: :delete, class: "btn btn-danger prepend-left-10" do
       %span.sr-only Remove
       = icon('trash')
+    = link_to revoke_profile_gpg_key_path(key), data: { confirm: 'Are you sure? All commits that were signed with this GPG key will be unverified.' }, method: :put, class: "btn btn-danger prepend-left-10" do
+      %span.sr-only Revoke
+      Revoke

config/routes/profile.rb

@@ -23,7 +23,11 @@ resource :profile, only: [:show, :update] do
     end
     resource :preferences, only: [:show, :update]
     resources :keys, only: [:index, :show, :create, :destroy]
-    resources :gpg_keys, only: [:index, :create, :destroy]
+    resources :gpg_keys, only: [:index, :create, :destroy] do
+      member do
+        put :revoke
+      end
+    end
     resources :emails, only: [:index, :create, :destroy]
     resources :chat_names, only: [:index, :new, :create, :destroy] do
       collection do

doc/workflow/gpg_signed_commits/index.md

@@ -42,6 +42,33 @@ For a signature to be verified two prerequisites need to be met:
 Once you add a key, you cannot edit it, only remove it. In case the paste
 didn't work, you will have to remove the offending key and re-add it.
+## Remove a GPG key
+
+1. On the upper right corner, click on your avatar and go to your **Settings**.
+
+1. Navigate to the **GPG keys** tab.
+
+1. Click on the trash icon besides the GPG key you want to delete.
+
+>**Note:**
+Removing a key **does not unverify** already signed commits. Commits that were
+verified by using this key will stay verified. Only unpushed commits will stay
+unverified once you remove this key.
+
+## Revoke a GPG key
+
+1. On the upper right corner, click on your avatar and go to your **Settings**.
+
+1. Navigate to the **GPG keys** tab.
+
+1. Click on **Revoke** besides the GPG key you want to delete.
+
+>**Note:**
+Revoking a key **unverifies** already signed commits. Commits that were
+verified by using this key will change to an unverified state. Future commits
+will also stay unverified once you revoke this key. This action should be used
+in case your key has been compromised.
+
 ## Verifying commits
 1. Within a project navigate to the **Commits** tag. Signed commits will show a

spec/features/profiles/gpg_keys_spec.rb

@@ -39,4 +39,20 @@ feature 'Profile > GPG Keys' do
     expect(page).to have_content('Your GPG keys (0)')
   end
+
+  scenario 'User revokes a key via the key index' do
+    gpg_key = create :gpg_key, user: user, key: GpgHelpers::User2.public_key
+    gpg_signature = create :gpg_signature, gpg_key: gpg_key, valid_signature: true
+
+    visit profile_gpg_keys_path
+
+    click_link('Revoke')
+
+    expect(page).to have_content('Your GPG keys (0)')
+
+    expect(gpg_signature.reload).to have_attributes(
+      valid_signature: false,
+      gpg_key: nil
+    )
+  end
 end

spec/models/gpg_key_spec.rb

@@ -95,4 +95,31 @@ describe GpgKey do
       should_email(user)
     end
   end
+
+  describe '#revoke' do
+    it 'invalidates all associated gpg signatures and destroys the key' do
+      gpg_key = create :gpg_key
+      gpg_signature = create :gpg_signature, valid_signature: true, gpg_key: gpg_key
+
+      unrelated_gpg_key = create :gpg_key, key: GpgHelpers::User2.public_key
+      unrelated_gpg_signature = create :gpg_signature, valid_signature: true, gpg_key: unrelated_gpg_key
+
+      gpg_key.revoke
+
+      expect(gpg_signature.reload).to have_attributes(
+        valid_signature: false,
+        gpg_key: nil
+      )
+
+      expect(gpg_key.destroyed?).to be true
+
+      # unrelated signature is left untouched
+      expect(unrelated_gpg_signature.reload).to have_attributes(
+        valid_signature: true,
+        gpg_key: unrelated_gpg_key
+      )
+
+      expect(unrelated_gpg_key.destroyed?).to be false
+    end
+  end
 end