Update the logic to decide if a key is valid and update the docs

Any key that has a validity period i.e. the difference of its
expires_at and created_at greater than the max SSH key lifetime
set by the instance administrator is invalid.

app/helpers/profiles_helper.rb

@@ -61,6 +61,11 @@ module ProfilesHelper
   def ssh_key_expires_field_description
     s_('Profiles|Key can still be used after expiration.')
   end
+
+  # Overridden in EE::ProfilesHelper#ssh_key_expiration_policy_enabled?
+  def ssh_key_expiration_policy_enabled?
+    false
+  end
 end
 
 ProfilesHelper.prepend_mod

doc/user/admin_area/settings/account_and_limit_settings.md

@@ -194,7 +194,7 @@ To set a limit on how long these sessions are valid:
 
 ## Limit the lifetime of SSH keys **(ULTIMATE SELF)**
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/1007) in GitLab 14.6. [with a flag](../../../administration/feature_flags.md) named `ff_limit_ssh_key_lifetime`. Disabled by default. 
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/1007) in GitLab 14.6 [with a flag](../../../administration/feature_flags.md) named `ff_limit_ssh_key_lifetime`. Disabled by default. 
 
 FLAG:
 On self-managed GitLab, by default this feature is not available. To make it available,

ee/app/helpers/ee/profiles_helper.rb

@@ -16,9 +16,9 @@ module EE
       return super unless ::Key.expiration_enforced?
 
       if ssh_key_expiration_policy_enabled?
-        s_('Profiles|Key will be deleted on this date. Maximum lifetime for SSH keys is %{max_ssh_key_lifetime} days') % { max_ssh_key_lifetime: ::Gitlab::CurrentSettings.max_ssh_key_lifetime }
+        s_('Profiles|Key becomes invalid on this date. Maximum lifetime for SSH keys is %{max_ssh_key_lifetime} days') % { max_ssh_key_lifetime: ::Gitlab::CurrentSettings.max_ssh_key_lifetime }
       else
-        s_('Profiles|Key will be deleted on this date.')
+        s_('Profiles|Key becomes invalid on this date.')
       end
     end
 
@@ -30,6 +30,7 @@ module EE
       ::Gitlab::CurrentSettings.max_ssh_key_lifetime_from_now
     end
 
+    override :ssh_key_expiration_policy_enabled?
     def ssh_key_expiration_policy_enabled?
       ::Gitlab::CurrentSettings.max_ssh_key_lifetime && ssh_key_expiration_policy_licensed? && ::Feature.enabled?(:ff_limit_ssh_key_lifetime)
     end

ee/app/models/ee/key.rb

@@ -33,9 +33,11 @@ module EE
       end
 
       def expires_at_before_max_expiry_date
-        return errors.add(:key, message: 'does not have an expiry date but maximum allowable lifetime for SSH keys is enforced by the instance administrator') if expires_at.blank?
+        return errors.add(:key, message: 'has no expiry date but an expiry date is required for SSH keys on this instance. Contact the instance administrator.') if expires_at.blank?
 
-        errors.add(:key, message: 'has greater than the maximum allowable lifetime for SSH keys enforced by the instance administrator') if expires_at > ssh_key_max_expiry_date
+        # when the key is not yet persisted the `created_at` field is nil
+        key_creation_date = created_at.presence || Time.current
+        errors.add(:key, message: 'has an invalid expiry date. Set a shorter lifetime for the key or contact the instance administrator.') if expires_at > key_creation_date + ::Gitlab::CurrentSettings.max_ssh_key_lifetime.days
       end
     end
 

ee/app/views/admin/application_settings/_ssh_key_expiration_policy.html.haml

@@ -2,6 +2,6 @@
 - form = local_assigns.fetch(:form)
 
 .form-group
-  = form.label :max_ssh_key_lifetime, _('Maximum allowable lifetime for SSH keys (days)'), class: 'label-light'
+  = form.label :max_ssh_key_lifetime, _('Maximum allowed lifetime for SSH keys (in days)'), class: 'label-light'
   = form.number_field :max_ssh_key_lifetime, class: 'form-control gl-form-input input-xs'
-  %span.form-text.text-muted#max_ssh_key_lifetime= _('When enabled, existing SSH keys may be revoked. Leave blank for no limit.')
+  %span.form-text.text-muted#max_ssh_key_lifetime= _('When enabled, SSH keys with no expiry date or an invalid expiration date are no longer accepted. Leave blank for no limit.')

ee/spec/helpers/ee/profiles_helper_spec.rb

@@ -51,7 +51,7 @@ RSpec.describe ProfilesHelper do
     using RSpec::Parameterized::TableSyntax
 
     where(:expiration_enforced, :result) do
-      true  | "Key will be deleted on this date."
+      true  | "Key becomes invalid on this date."
       false | "Key can still be used after expiration."
     end
 

ee/spec/models/ee/key_spec.rb

@@ -26,12 +26,15 @@ RSpec.describe Key do
     describe '#expires_at_before_max_expiry_date' do
       using RSpec::Parameterized::TableSyntax
 
+      context 'for a range of key expiry combinations' do
         where(:key, :max_ssh_key_lifetime, :valid) do
-        build(:personal_key, expires_at: 20.days.from_now) | 10 | false
-        build(:personal_key, expires_at: 7.days.from_now) | 10 | true
-        build(:personal_key, expires_at: 20.days.from_now) | nil | true
-        build(:personal_key, expires_at: nil) | 20 | false
-        build(:personal_key, expires_at: nil) | nil | true
+          build(:personal_key, created_at: Time.current, expires_at: nil) | nil | true
+          build(:personal_key, created_at: Time.current, expires_at: 20.days.from_now) | nil | true
+          build(:personal_key, created_at: 1.day.ago, expires_at: 20.days.from_now) | 10 | false
+          build(:personal_key, created_at: 6.days.ago, expires_at: 3.days.from_now) | 10 | true
+          build(:personal_key, created_at: 10.days.ago, expires_at: 7.days.from_now) | 10 | false
+          build(:personal_key, created_at: Time.current, expires_at: nil) | 20 | false
+          build(:personal_key, expires_at: nil) | 30 | false
         end
 
         with_them do
@@ -39,12 +42,33 @@ RSpec.describe Key do
             stub_licensed_features(ssh_key_expiration_policy: true)
             stub_application_setting(max_ssh_key_lifetime: max_ssh_key_lifetime)
           end
-
           it 'checks if ssh key expiration is valid' do
             expect(key.valid?).to eq(valid)
           end
         end
       end
+
+      context 'when keys and max expiry are set' do
+        where(:key, :max_ssh_key_lifetime, :valid) do
+          build(:personal_key, created_at: Time.current, expires_at: 20.days.from_now) | 10 | false
+          build(:personal_key, created_at: Time.current, expires_at: 7.days.from_now) | 10 | true
+        end
+
+        with_them do
+          before do
+            stub_licensed_features(ssh_key_expiration_policy: true)
+            stub_application_setting(max_ssh_key_lifetime: max_ssh_key_lifetime)
+          end
+          it 'checks validity properly in the future too' do
+            # Travel to the day before the key is set to 'expire'.
+            # max_ssh_key_lifetime should still be enforced correctly.
+            travel_to(key.expires_at - 1) do
+              expect(key.valid?).to eq(valid)
+            end
+          end
+        end
+      end
+    end
   end
 
   describe 'only_expired_and_enforced?' do

locale/gitlab.pot

@@ -21493,10 +21493,10 @@ msgstr ""
 msgid "Maximum Users"
 msgstr ""
 
-msgid "Maximum allowable lifetime for SSH keys (days)"
+msgid "Maximum allowable lifetime for personal access token (days)"
 msgstr ""
 
-msgid "Maximum allowable lifetime for personal access token (days)"
+msgid "Maximum allowed lifetime for SSH keys (in days)"
 msgstr ""
 
 msgid "Maximum artifacts size"
@@ -26756,16 +26756,16 @@ msgstr ""
 msgid "Profiles|Key"
 msgstr ""
 
-msgid "Profiles|Key can still be used after expiration."
+msgid "Profiles|Key becomes invalid on this date."
 msgstr ""
 
-msgid "Profiles|Key usable beyond expiration date."
+msgid "Profiles|Key becomes invalid on this date. Maximum lifetime for SSH keys is %{max_ssh_key_lifetime} days"
 msgstr ""
 
-msgid "Profiles|Key will be deleted on this date."
+msgid "Profiles|Key can still be used after expiration."
 msgstr ""
 
-msgid "Profiles|Key will be deleted on this date. Maximum lifetime for SSH keys is %{max_ssh_key_lifetime} days"
+msgid "Profiles|Key usable beyond expiration date."
 msgstr ""
 
 msgid "Profiles|Last used:"
@@ -39227,7 +39227,7 @@ msgstr ""
 msgid "When a runner is locked, it cannot be assigned to other projects"
 msgstr ""
 
-msgid "When enabled, existing SSH keys may be revoked. Leave blank for no limit."
+msgid "When enabled, SSH keys with no expiry date or an invalid expiration date are no longer accepted. Leave blank for no limit."
 msgstr ""
 
 msgid "When enabled, existing personal access tokens may be revoked. Leave blank for no limit."