fix: gate passphrase cache behind authenticator availability

Fixes #2783

Author: msfjarvis

app/src/main/java/app/passwordstore/ui/settings/PGPSettings.kt

@@ -8,6 +8,7 @@ package app.passwordstore.ui.settings
 import androidx.fragment.app.FragmentActivity
 import app.passwordstore.R
 import app.passwordstore.ui.pgp.PGPKeyListActivity
+import app.passwordstore.util.auth.BiometricAuthenticator
 import app.passwordstore.util.extensions.launchActivity
 import app.passwordstore.util.features.Feature
 import app.passwordstore.util.settings.PreferenceKeys
@@ -33,6 +34,7 @@ class PGPSettings(private val activity: FragmentActivity) : SettingsProvider {
         persistent = true
       }
       switch(Feature.EnablePGPPassphraseCache.configKey) {
+        enabled = BiometricAuthenticator.canAuthenticate(activity)
         titleRes = R.string.pref_passphrase_cache_title
         summaryRes = R.string.pref_passphrase_cache_summary
         defaultValue = false

app/src/main/res/values/strings.xml

@@ -136,7 +136,7 @@
   <string name="pref_pgp_key_manager_title">Key manager</string>
   <string name="pref_pgp_ascii_armor_title">Encrypt in ASCII armor mode</string>
   <string name="pref_passphrase_cache_title">Enable passphrase caching</string>
-  <string name="pref_passphrase_cache_summary">WARNING: this feature is functional but very experimental.</string>
+  <string name="pref_passphrase_cache_summary">WARNING: this feature is functional but very experimental. Requires an active screen lock.</string>
 
   <!-- PasswordGenerator fragment -->
   <string name="pwgen_title">Generate Password</string>