Revert "Store mutable reference to Device in PasswordSafe"

This reverts commit 13006c00dcbd570cf8347d89557834e320427377.

3 files changed, 45 insertions, 21 deletions

diff --git a/TODO.md b/TODO.md
index d6a3509..1ff723d 100644
--- a/TODO.md
+++ b/TODO.md
@@ -13,6 +13,7 @@ SPDX-License-Identifier: MIT
 - Clear passwords from memory.
 - Lock password safe in `PasswordSafe::drop()` (see [nitrokey-storage-firmware
   issue 65][]).
+- Disable creation of multiple password safes at the same time.
 - Check timing in Storage tests.
 - Consider restructuring `device::StorageStatus`.
 
diff --git a/src/pws.rs b/src/pws.rs
index a5b9d33..371de6e 100644
--- a/src/pws.rs
+++ b/src/pws.rs
@@ -18,7 +18,8 @@ pub const SLOT_COUNT: u8 = 16;
 /// The password safe stores a tuple consisting of a name, a login and a password on a slot.  The
 /// number of available slots is [`SLOT_COUNT`][].  The slots are addressed starting with zero.  To
 /// retrieve a password safe from a Nitrokey device, use the [`get_password_safe`][] method from
-/// the [`GetPasswordSafe`][] trait.
+/// the [`GetPasswordSafe`][] trait.  Note that the device must live at least as long as the
+/// password safe.
 ///
 /// Once the password safe has been unlocked, it can be accessed without a password.  Therefore it
 /// is mandatory to call [`lock`][] on the corresponding device after the password store is used.
@@ -57,17 +58,21 @@ pub const SLOT_COUNT: u8 = 16;
 /// [`GetPasswordSafe`]: trait.GetPasswordSafe.html
 #[derive(Debug)]
 pub struct PasswordSafe<'a> {
-    device: &'a mut dyn Device,
+    _device: &'a dyn Device,
 }
 
 /// Provides access to a [`PasswordSafe`][].
 ///
+/// The device that implements this trait must always live at least as long as a password safe
+/// retrieved from it.
+///
 /// [`PasswordSafe`]: struct.PasswordSafe.html
 pub trait GetPasswordSafe {
     /// Enables and returns the password safe.
     ///
-    /// It is mandatory to lock the underlying device using [`lock`][] after the password safe has
-    /// been used.  Otherwise, other applications can access the password store without
+    /// The underlying device must always live at least as long as a password safe retrieved from
+    /// it.  It is mandatory to lock the underlying device using [`lock`][] after the password safe
+    /// has been used.  Otherwise, other applications can access the password store without
     /// authentication.
     ///
     /// If this method returns an `AesDecryptionFailed` (Nitrokey Pro) or `Unknown` (Nitrokey
@@ -116,17 +121,12 @@ pub trait GetPasswordSafe {
 }
 
 fn get_password_safe<'a>(
-    device: &'a mut dyn Device,
+    device: &'a dyn Device,
     user_pin: &str,
 ) -> Result<PasswordSafe<'a>, Error> {
     let user_pin_string = get_cstring(user_pin)?;
-    let result = get_command_result(unsafe {
-        nitrokey_sys::NK_enable_password_safe(user_pin_string.as_ptr())
-    });
-    match result {
-        Ok(()) => Ok(PasswordSafe { device }),
-        Err(err) => Err(err),
-    }
+    get_command_result(unsafe { nitrokey_sys::NK_enable_password_safe(user_pin_string.as_ptr()) })
+        .map(|_| PasswordSafe { _device: device })
 }
 
 fn get_pws_result(s: String) -> Result<String, Error> {
diff --git a/tests/device.rs b/tests/device.rs
index 6a3683b..5c52024 100644
--- a/tests/device.rs
+++ b/tests/device.rs
@@ -156,7 +156,10 @@ fn change_user_pin(device: DeviceWrapper) {
     let device = device.authenticate_user(USER_NEW_PASSWORD).unwrap_err().0;
 
     let mut device = device;
-    assert_ok!((), device.change_user_pin(DEFAULT_USER_PIN, USER_NEW_PASSWORD));
+    assert_ok!(
+        (),
+        device.change_user_pin(DEFAULT_USER_PIN, USER_NEW_PASSWORD)
+    );
 
     let device = device.authenticate_user(DEFAULT_USER_PIN).unwrap_err().0;
     let device = device
@@ -179,7 +182,10 @@ fn change_user_pin(device: DeviceWrapper) {
 
 #[test_device]
 fn change_admin_pin(device: DeviceWrapper) {
-    let device = device.authenticate_admin(DEFAULT_ADMIN_PIN).unwrap().device();
+    let device = device
+        .authenticate_admin(DEFAULT_ADMIN_PIN)
+        .unwrap()
+        .device();
     let mut device = device.authenticate_admin(ADMIN_NEW_PASSWORD).unwrap_err().0;
 
     assert_ok!(
@@ -203,7 +209,10 @@ fn change_admin_pin(device: DeviceWrapper) {
         device.change_admin_pin(ADMIN_NEW_PASSWORD, DEFAULT_ADMIN_PIN)
     );
 
-    let device = device.authenticate_admin(DEFAULT_ADMIN_PIN).unwrap().device();
+    let device = device
+        .authenticate_admin(DEFAULT_ADMIN_PIN)
+        .unwrap()
+        .device();
     device.authenticate_admin(ADMIN_NEW_PASSWORD).unwrap_err();
 }
 
@@ -225,7 +234,10 @@ where
 #[test_device]
 fn unlock_user_pin(device: DeviceWrapper) {
     let mut device = device.authenticate_user(DEFAULT_USER_PIN).unwrap().device();
-    assert_ok!((), device.unlock_user_pin(DEFAULT_ADMIN_PIN, DEFAULT_USER_PIN));
+    assert_ok!(
+        (),
+        device.unlock_user_pin(DEFAULT_ADMIN_PIN, DEFAULT_USER_PIN)
+    );
     assert_cmd_err!(
         CommandError::WrongPassword,
         device.unlock_user_pin(DEFAULT_USER_PIN, DEFAULT_USER_PIN)
@@ -236,21 +248,26 @@ fn unlock_user_pin(device: DeviceWrapper) {
     let device = require_failed_user_login(device, &wrong_password, CommandError::WrongPassword);
     let device = require_failed_user_login(device, &wrong_password, CommandError::WrongPassword);
     let device = require_failed_user_login(device, &wrong_password, CommandError::WrongPassword);
-    let mut device = require_failed_user_login(device, DEFAULT_USER_PIN, CommandError::WrongPassword);
+    let mut device =
+        require_failed_user_login(device, DEFAULT_USER_PIN, CommandError::WrongPassword);
 
     // unblock with current PIN
     assert_cmd_err!(
         CommandError::WrongPassword,
         device.unlock_user_pin(DEFAULT_USER_PIN, DEFAULT_USER_PIN)
     );
-    assert_ok!((), device.unlock_user_pin(DEFAULT_ADMIN_PIN, DEFAULT_USER_PIN));
+    assert_ok!(
+        (),
+        device.unlock_user_pin(DEFAULT_ADMIN_PIN, DEFAULT_USER_PIN)
+    );
     let device = device.authenticate_user(DEFAULT_USER_PIN).unwrap().device();
 
     // block user PIN
     let device = require_failed_user_login(device, &wrong_password, CommandError::WrongPassword);
     let device = require_failed_user_login(device, &wrong_password, CommandError::WrongPassword);
     let device = require_failed_user_login(device, &wrong_password, CommandError::WrongPassword);
-    let mut device = require_failed_user_login(device, DEFAULT_USER_PIN, CommandError::WrongPassword);
+    let mut device =
+        require_failed_user_login(device, DEFAULT_USER_PIN, CommandError::WrongPassword);
 
     // unblock with new PIN
     assert_cmd_err!(
@@ -307,7 +324,10 @@ fn factory_reset(device: DeviceWrapper) {
     );
     assert_ok!((), device.factory_reset(ADMIN_NEW_PASSWORD));
 
-    let device = device.authenticate_admin(DEFAULT_ADMIN_PIN).unwrap().device();
+    let device = device
+        .authenticate_admin(DEFAULT_ADMIN_PIN)
+        .unwrap()
+        .device();
 
     let user = unwrap_ok!(device.authenticate_user(DEFAULT_USER_PIN));
     assert_cmd_err!(CommandError::SlotNotProgrammed, user.get_totp_slot_name(1));
@@ -335,7 +355,10 @@ fn build_aes_key(device: DeviceWrapper) {
     );
     assert_ok!((), device.build_aes_key(DEFAULT_ADMIN_PIN));
 
-    let mut device = device.authenticate_admin(DEFAULT_ADMIN_PIN).unwrap().device();
+    let mut device = device
+        .authenticate_admin(DEFAULT_ADMIN_PIN)
+        .unwrap()
+        .device();
 
     let pws = unwrap_ok!(device.get_password_safe(DEFAULT_USER_PIN));
     assert_utf8_err_or_ne("test", pws.get_slot_name(0));