[Wi-Fi] Do not delete certs when forgetting network

Deleting EAP Wi-Fi configuration deletes shared credentials used by other
configs. To resolve this issue the following changes were implemented:
1. When manually adding Wi-Fi certs from storage, Wi-Fi will not attempt
to delete them when network is removed.
2. When apps use WifiEnterpriseConfig#setClientKeyEntry to add certs,
they will be deleted if the network is removed.
3. Allow the user to delete Wi-Fi certs the same way that allows the
user to add them. Make the "Remove" option available, and implement key
store removal in settings.

Bug: 30248175
Test: atest WifiEnterpriseConfigTest
Test: Load certs, remove certs from credentials menu
Test: Load cert, create 2 EAP networks that use it, forget one network
Change-Id: I2015207d51188821da3397e1947e5eb6aefbf6e1

src/com/android/settings/UserCredentialsSettings.java

@@ -154,11 +154,15 @@ public class UserCredentialsSettings extends SettingsPreferenceFragment
                         dialog.dismiss();
                     }
                 };
-                if (item.isSystem()) {
+                // TODO: b/127865361
-                    // TODO: a safe means of clearing wifi certificates. Configs refer to aliases
+                //       a safe means of clearing wifi certificates. Configs refer to aliases
-                    //       directly so deleting certs will break dependent access points.
+                //       directly so deleting certs will break dependent access points.
-                    builder.setNegativeButton(R.string.trusted_credentials_remove_label, listener);
+                //       However, Wi-Fi used to remove this certificate from storage if the network
-                }
+                //       was removed, regardless if it is used in more than one network.
+                //       It has been decided to allow removing certificates from this menu, as we
+                //       assume that the user who manually adds certificates must have a way to
+                //       manually remove them.
+                builder.setNegativeButton(R.string.trusted_credentials_remove_label, listener);
             }
             return builder.create();
         }
@@ -172,7 +176,8 @@ public class UserCredentialsSettings extends SettingsPreferenceFragment
          * Deletes all certificates and keys under a given alias.
          *
          * If the {@link Credential} is for a system alias, all active grants to the alias will be
-         * removed using {@link KeyChain}.
+         * removed using {@link KeyChain}. If the {@link Credential} is for Wi-Fi alias, all
+         * credentials and keys will be removed using {@link KeyStore}.
          */
         private class RemoveCredentialsTask extends AsyncTask<Credential, Void, Credential[]> {
             private Context context;
@@ -188,14 +193,32 @@ public class UserCredentialsSettings extends SettingsPreferenceFragment
                 for (final Credential credential : credentials) {
                     if (credential.isSystem()) {
                         removeGrantsAndDelete(credential);
-                        continue;
+                    } else {
+                        deleteWifiCredential(credential);
                     }
-                    throw new UnsupportedOperationException(
-                            "Not implemented for wifi certificates. This should not be reachable.");
                 }
                 return credentials;
             }
 
+            private void deleteWifiCredential(final Credential credential) {
+                final KeyStore keyStore = KeyStore.getInstance();
+                final EnumSet<Credential.Type> storedTypes = credential.getStoredTypes();
+
+                // Remove all Wi-Fi credentials
+                if (storedTypes.contains(Credential.Type.USER_KEY)) {
+                    keyStore.delete(Credentials.USER_PRIVATE_KEY + credential.getAlias(),
+                            Process.WIFI_UID);
+                }
+                if (storedTypes.contains(Credential.Type.USER_CERTIFICATE)) {
+                    keyStore.delete(Credentials.USER_CERTIFICATE + credential.getAlias(),
+                            Process.WIFI_UID);
+                }
+                if (storedTypes.contains(Credential.Type.CA_CERTIFICATE)) {
+                    keyStore.delete(Credentials.CA_CERTIFICATE + credential.getAlias(),
+                            Process.WIFI_UID);
+                }
+            }
+
             private void removeGrantsAndDelete(final Credential credential) {
                 final KeyChainConnection conn;
                 try {
@@ -488,5 +511,11 @@ public class UserCredentialsSettings extends SettingsPreferenceFragment
         public boolean isSystem() {
             return UserHandle.getAppId(uid) == Process.SYSTEM_UID;
         }
+
+        public String getAlias() { return alias; }
+
+        public EnumSet<Type> getStoredTypes() {
+            return storedTypes;
+        }
     }
 }