Merge branch 'revert' into next

The tests with the 0.4.0-alpha.1 version showed that the approach using
mutable references to the Device in User, Admin and PasswordSafe causes
problems in nitrocli, see [0].  Therefore, these changes are reverted.

[0] https://lists.sr.ht/~ireas/nitrokey-rs-dev/%3C43cc304d-23e8-7f95-2167-ce3f0530b81e%40posteo.net%3E

* revert:
  Revert "Store mutable reference to Device in PasswordSafe"
  Revert "Refactor User and Admin to use a mutable reference"

10 files changed, 301 insertions, 198 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9227510..e98e857 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -38,10 +38,6 @@ SPDX-License-Identifier: MIT
   - Implement `DerefMut` for `User<T>` and `Admin<T>`.
   - Add `device_mut` method to `DeviceWrapper`.
   - Require a mutable `Device` reference if a method changes the device state.
-- Let `Admin` and `User` store a mutable reference to the `Device` instead of
-  the `Device` value.
-- Let `PasswordStore` store a mutable reference to the `Device` instead of a
-  non-mutable reference.
 
 # v0.3.4 (2019-01-20)
 - Fix authentication methods that assumed that `char` is signed.
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/auth.rs b/src/auth.rs
index 573fed3..f9f50fa 100644
--- a/src/auth.rs
+++ b/src/auth.rs
@@ -42,10 +42,16 @@ pub trait Authenticate {
     /// fn perform_other_task(device: &DeviceWrapper) {}
     ///
     /// # fn try_main() -> Result<(), Error> {
-    /// let mut device = nitrokey::connect()?;
-    /// match device.authenticate_user("123456") {
-    ///     Ok(user) => perform_user_task(&user),
-    ///     Err(err) => eprintln!("Could not authenticate as user: {}", err),
+    /// let device = nitrokey::connect()?;
+    /// let device = match device.authenticate_user("123456") {
+    ///     Ok(user) => {
+    ///         perform_user_task(&user);
+    ///         user.device()
+    ///     },
+    ///     Err((device, err)) => {
+    ///         eprintln!("Could not authenticate as user: {}", err);
+    ///         device
+    ///     },
     /// };
     /// perform_other_task(&device);
     /// #     Ok(())
@@ -55,9 +61,9 @@ pub trait Authenticate {
     /// [`InvalidString`]: enum.LibraryError.html#variant.InvalidString
     /// [`RngError`]: enum.CommandError.html#variant.RngError
     /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
-    fn authenticate_user(&mut self, password: &str) -> Result<User<'_, Self>, Error>
+    fn authenticate_user(self, password: &str) -> Result<User<Self>, (Self, Error)>
     where
-        Self: Device + std::marker::Sized;
+        Self: Device + Sized;
 
     /// Performs admin authentication.  This method consumes the device.  If successful, an
     /// authenticated device is returned.  Otherwise, the current unauthenticated device and the
@@ -82,10 +88,16 @@ pub trait Authenticate {
     /// fn perform_other_task(device: &DeviceWrapper) {}
     ///
     /// # fn try_main() -> Result<(), Error> {
-    /// let mut device = nitrokey::connect()?;
-    /// match device.authenticate_admin("123456") {
-    ///     Ok(admin) => perform_admin_task(&admin),
-    ///     Err(err) => eprintln!("Could not authenticate as admin: {}", err),
+    /// let device = nitrokey::connect()?;
+    /// let device = match device.authenticate_admin("123456") {
+    ///     Ok(admin) => {
+    ///         perform_admin_task(&admin);
+    ///         admin.device()
+    ///     },
+    ///     Err((device, err)) => {
+    ///         eprintln!("Could not authenticate as admin: {}", err);
+    ///         device
+    ///     },
     /// };
     /// perform_other_task(&device);
     /// #     Ok(())
@@ -95,13 +107,13 @@ pub trait Authenticate {
     /// [`InvalidString`]: enum.LibraryError.html#variant.InvalidString
     /// [`RngError`]: enum.CommandError.html#variant.RngError
     /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
-    fn authenticate_admin(&mut self, password: &str) -> Result<Admin<'_, Self>, Error>
+    fn authenticate_admin(self, password: &str) -> Result<Admin<Self>, (Self, Error)>
     where
-        Self: Device + std::marker::Sized;
+        Self: Device + Sized;
 }
 
-trait AuthenticatedDevice<'a, T> {
-    fn new(device: &'a mut T, temp_password: Vec<u8>) -> Self;
+trait AuthenticatedDevice<T> {
+    fn new(device: T, temp_password: Vec<u8>) -> Self;
 
     fn temp_password_ptr(&self) -> *const c_char;
 }
@@ -116,8 +128,8 @@ trait AuthenticatedDevice<'a, T> {
 /// [`authenticate_admin`]: trait.Authenticate.html#method.authenticate_admin
 /// [`device`]: #method.device
 #[derive(Debug)]
-pub struct User<'a, T: Device> {
-    device: &'a mut T,
+pub struct User<T: Device> {
+    device: T,
     temp_password: Vec<u8>,
 }
 
@@ -131,42 +143,89 @@ pub struct User<'a, T: Device> {
 /// [`authenticate_admin`]: trait.Authenticate.html#method.authenticate_admin
 /// [`device`]: #method.device
 #[derive(Debug)]
-pub struct Admin<'a, T: Device> {
-    device: &'a mut T,
+pub struct Admin<T: Device> {
+    device: T,
     temp_password: Vec<u8>,
 }
 
-fn authenticate<'a, D, A, T>(device: &'a mut D, password: &str, callback: T) -> Result<A, Error>
+fn authenticate<D, A, T>(device: D, password: &str, callback: T) -> Result<A, (D, Error)>
 where
     D: Device,
-    A: AuthenticatedDevice<'a, D>,
+    A: AuthenticatedDevice<D>,
     T: Fn(*const c_char, *const c_char) -> c_int,
 {
-    let temp_password = generate_password(TEMPORARY_PASSWORD_LENGTH)?;
-    let password = get_cstring(password)?;
+    let temp_password = match generate_password(TEMPORARY_PASSWORD_LENGTH) {
+        Ok(temp_password) => temp_password,
+        Err(err) => return Err((device, err)),
+    };
+    let password = match get_cstring(password) {
+        Ok(password) => password,
+        Err(err) => return Err((device, err)),
+    };
     let password_ptr = password.as_ptr();
     let temp_password_ptr = temp_password.as_ptr() as *const c_char;
     match callback(password_ptr, temp_password_ptr) {
         0 => Ok(A::new(device, temp_password)),
-        rv => Err(Error::from(rv)),
+        rv => Err((device, Error::from(rv))),
     }
 }
 
-impl<'a, T: Device> ops::Deref for User<'a, T> {
+fn authenticate_user_wrapper<T, C>(
+    device: T,
+    constructor: C,
+    password: &str,
+) -> Result<User<DeviceWrapper>, (DeviceWrapper, Error)>
+where
+    T: Device,
+    C: Fn(T) -> DeviceWrapper,
+{
+    let result = device.authenticate_user(password);
+    match result {
+        Ok(user) => Ok(User::new(constructor(user.device), user.temp_password)),
+        Err((device, err)) => Err((constructor(device), err)),
+    }
+}
+
+fn authenticate_admin_wrapper<T, C>(
+    device: T,
+    constructor: C,
+    password: &str,
+) -> Result<Admin<DeviceWrapper>, (DeviceWrapper, Error)>
+where
+    T: Device,
+    C: Fn(T) -> DeviceWrapper,
+{
+    let result = device.authenticate_admin(password);
+    match result {
+        Ok(user) => Ok(Admin::new(constructor(user.device), user.temp_password)),
+        Err((device, err)) => Err((constructor(device), err)),
+    }
+}
+
+impl<T: Device> User<T> {
+    /// Forgets the user authentication and returns an unauthenticated device.  This method
+    /// consumes the authenticated device.  It does not perform any actual commands on the
+    /// Nitrokey.
+    pub fn device(self) -> T {
+        self.device
+    }
+}
+
+impl<T: Device> ops::Deref for User<T> {
     type Target = T;
 
     fn deref(&self) -> &Self::Target {
-        self.device
+        &self.device
     }
 }
 
-impl<'a, T: Device> ops::DerefMut for User<'a, T> {
+impl<T: Device> ops::DerefMut for User<T> {
     fn deref_mut(&mut self) -> &mut T {
-        self.device
+        &mut self.device
     }
 }
 
-impl<'a, T: Device> GenerateOtp for User<'a, T> {
+impl<T: Device> GenerateOtp for User<T> {
     fn get_hotp_code(&mut self, slot: u8) -> Result<String, Error> {
         result_from_string(unsafe {
             nitrokey_sys::NK_get_hotp_code_PIN(slot, self.temp_password_ptr())
@@ -180,8 +239,8 @@ impl<'a, T: Device> GenerateOtp for User<'a, T> {
     }
 }
 
-impl<'a, T: Device> AuthenticatedDevice<'a, T> for User<'a, T> {
-    fn new(device: &'a mut T, temp_password: Vec<u8>) -> Self {
+impl<T: Device> AuthenticatedDevice<T> for User<T> {
+    fn new(device: T, temp_password: Vec<u8>) -> Self {
         User {
             device,
             temp_password,
@@ -193,21 +252,28 @@ impl<'a, T: Device> AuthenticatedDevice<'a, T> for User<'a, T> {
     }
 }
 
-impl<'a, T: Device> ops::Deref for Admin<'a, T> {
+impl<T: Device> ops::Deref for Admin<T> {
     type Target = T;
 
     fn deref(&self) -> &Self::Target {
-        self.device
+        &self.device
     }
 }
 
-impl<'a, T: Device> ops::DerefMut for Admin<'a, T> {
+impl<T: Device> ops::DerefMut for Admin<T> {
     fn deref_mut(&mut self) -> &mut T {
-        self.device
+        &mut self.device
     }
 }
 
-impl<'a, T: Device> Admin<'a, T> {
+impl<T: Device> Admin<T> {
+    /// Forgets the user authentication and returns an unauthenticated device.  This method
+    /// consumes the authenticated device.  It does not perform any actual commands on the
+    /// Nitrokey.
+    pub fn device(self) -> T {
+        self.device
+    }
+
     /// Writes the given configuration to the Nitrokey device.
     ///
     /// # Errors
@@ -221,11 +287,14 @@ impl<'a, T: Device> Admin<'a, T> {
     /// # use nitrokey::Error;
     ///
     /// # fn try_main() -> Result<(), Error> {
-    /// let mut device = nitrokey::connect()?;
+    /// let device = nitrokey::connect()?;
     /// let config = Config::new(None, None, None, false);
     /// match device.authenticate_admin("12345678") {
-    ///     Ok(mut admin) => admin.write_config(config)?,
-    ///     Err(err) => eprintln!("Could not authenticate as admin: {}", err),
+    ///     Ok(mut admin) => {
+    ///         admin.write_config(config);
+    ///         ()
+    ///     },
+    ///     Err((_, err)) => eprintln!("Could not authenticate as admin: {}", err),
     /// };
     /// #     Ok(())
     /// # }
@@ -247,7 +316,7 @@ impl<'a, T: Device> Admin<'a, T> {
     }
 }
 
-impl<'a, T: Device> ConfigureOtp for Admin<'a, T> {
+impl<T: Device> ConfigureOtp for Admin<T> {
     fn write_hotp_slot(&mut self, data: OtpSlotData, counter: u64) -> Result<(), Error> {
         let raw_data = RawOtpSlotData::new(data)?;
         get_command_result(unsafe {
@@ -295,8 +364,8 @@ impl<'a, T: Device> ConfigureOtp for Admin<'a, T> {
     }
 }
 
-impl<'a, T: Device> AuthenticatedDevice<'a, T> for Admin<'a, T> {
-    fn new(device: &'a mut T, temp_password: Vec<u8>) -> Self {
+impl<T: Device> AuthenticatedDevice<T> for Admin<T> {
+    fn new(device: T, temp_password: Vec<u8>) -> Self {
         Admin {
             device,
             temp_password,
@@ -309,27 +378,35 @@ impl<'a, T: Device> AuthenticatedDevice<'a, T> for Admin<'a, T> {
 }
 
 impl Authenticate for DeviceWrapper {
-    fn authenticate_user(&mut self, password: &str) -> Result<User<'_, Self>, Error> {
-        authenticate(self, password, |password_ptr, temp_password_ptr| unsafe {
-            nitrokey_sys::NK_user_authenticate(password_ptr, temp_password_ptr)
-        })
+    fn authenticate_user(self, password: &str) -> Result<User<Self>, (Self, Error)> {
+        match self {
+            DeviceWrapper::Storage(storage) => {
+                authenticate_user_wrapper(storage, DeviceWrapper::Storage, password)
+            }
+            DeviceWrapper::Pro(pro) => authenticate_user_wrapper(pro, DeviceWrapper::Pro, password),
+        }
     }
 
-    fn authenticate_admin(&mut self, password: &str) -> Result<Admin<'_, Self>, Error> {
-        authenticate(self, password, |password_ptr, temp_password_ptr| unsafe {
-            nitrokey_sys::NK_user_authenticate(password_ptr, temp_password_ptr)
-        })
+    fn authenticate_admin(self, password: &str) -> Result<Admin<Self>, (Self, Error)> {
+        match self {
+            DeviceWrapper::Storage(storage) => {
+                authenticate_admin_wrapper(storage, DeviceWrapper::Storage, password)
+            }
+            DeviceWrapper::Pro(pro) => {
+                authenticate_admin_wrapper(pro, DeviceWrapper::Pro, password)
+            }
+        }
     }
 }
 
 impl Authenticate for Pro {
-    fn authenticate_user(&mut self, password: &str) -> Result<User<'_, Self>, Error> {
+    fn authenticate_user(self, password: &str) -> Result<User<Self>, (Self, Error)> {
         authenticate(self, password, |password_ptr, temp_password_ptr| unsafe {
             nitrokey_sys::NK_user_authenticate(password_ptr, temp_password_ptr)
         })
     }
 
-    fn authenticate_admin(&mut self, password: &str) -> Result<Admin<'_, Self>, Error> {
+    fn authenticate_admin(self, password: &str) -> Result<Admin<Self>, (Self, Error)> {
         authenticate(self, password, |password_ptr, temp_password_ptr| unsafe {
             nitrokey_sys::NK_first_authenticate(password_ptr, temp_password_ptr)
         })
@@ -337,13 +414,13 @@ impl Authenticate for Pro {
 }
 
 impl Authenticate for Storage {
-    fn authenticate_user(&mut self, password: &str) -> Result<User<'_, Self>, Error> {
+    fn authenticate_user(self, password: &str) -> Result<User<Self>, (Self, Error)> {
         authenticate(self, password, |password_ptr, temp_password_ptr| unsafe {
             nitrokey_sys::NK_user_authenticate(password_ptr, temp_password_ptr)
         })
     }
 
-    fn authenticate_admin(&mut self, password: &str) -> Result<Admin<'_, Self>, Error> {
+    fn authenticate_admin(self, password: &str) -> Result<Admin<Self>, (Self, Error)> {
         authenticate(self, password, |password_ptr, temp_password_ptr| unsafe {
             nitrokey_sys::NK_first_authenticate(password_ptr, temp_password_ptr)
         })
diff --git a/src/device.rs b/src/device.rs
index a0df30e..f6492cd 100644
--- a/src/device.rs
+++ b/src/device.rs
@@ -71,10 +71,16 @@ impl fmt::Display for VolumeMode {
 /// fn perform_other_task(device: &DeviceWrapper) {}
 ///
 /// # fn try_main() -> Result<(), Error> {
-/// let mut device = nitrokey::connect()?;
-/// match device.authenticate_user("123456") {
-///     Ok(user) => perform_user_task(&user),
-///     Err(err) => eprintln!("Could not authenticate as user: {}", err),
+/// let device = nitrokey::connect()?;
+/// let device = match device.authenticate_user("123456") {
+///     Ok(user) => {
+///         perform_user_task(&user);
+///         user.device()
+///     },
+///     Err((device, err)) => {
+///         eprintln!("Could not authenticate as user: {}", err);
+///         device
+///     },
 /// };
 /// perform_other_task(&device);
 /// #     Ok(())
@@ -129,10 +135,16 @@ pub enum DeviceWrapper {
 /// fn perform_other_task(device: &Pro) {}
 ///
 /// # fn try_main() -> Result<(), Error> {
-/// let mut device = nitrokey::Pro::connect()?;
-/// match device.authenticate_user("123456") {
-///     Ok(user) => perform_user_task(&user),
-///     Err(err) => eprintln!("Could not authenticate as user: {}", err),
+/// let device = nitrokey::Pro::connect()?;
+/// let device = match device.authenticate_user("123456") {
+///     Ok(user) => {
+///         perform_user_task(&user);
+///         user.device()
+///     },
+///     Err((device, err)) => {
+///         eprintln!("Could not authenticate as user: {}", err);
+///         device
+///     },
 /// };
 /// perform_other_task(&device);
 /// #     Ok(())
@@ -169,10 +181,16 @@ pub struct Pro {
 /// fn perform_other_task(device: &Storage) {}
 ///
 /// # fn try_main() -> Result<(), Error> {
-/// let mut device = nitrokey::Storage::connect()?;
-/// match device.authenticate_user("123456") {
-///     Ok(user) => perform_user_task(&user),
-///     Err(err) => eprintln!("Could not authenticate as user: {}", err),
+/// let device = nitrokey::Storage::connect()?;
+/// let device = match device.authenticate_user("123456") {
+///     Ok(user) => {
+///         perform_user_task(&user);
+///         user.device()
+///     },
+///     Err((device, err)) => {
+///         eprintln!("Could not authenticate as user: {}", err);
+///         device
+///     },
 /// };
 /// perform_other_task(&device);
 /// #     Ok(())
diff --git a/src/lib.rs b/src/lib.rs
index d7a8c5e..c35829c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -44,7 +44,7 @@
 //! # use nitrokey::Error;
 //!
 //! # fn try_main() -> Result<(), Error> {
-//! let mut device = nitrokey::connect()?;
+//! let device = nitrokey::connect()?;
 //! let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::SixDigits);
 //! match device.authenticate_admin("12345678") {
 //!     Ok(mut admin) => {
@@ -53,7 +53,7 @@
 //!             Err(err) => eprintln!("Could not write slot: {}", err),
 //!         }
 //!     },
-//!     Err(err) => eprintln!("Could not authenticate as admin: {}", err),
+//!     Err((_, err)) => eprintln!("Could not authenticate as admin: {}", err),
 //! }
 //! #     Ok(())
 //! # }
diff --git a/src/otp.rs b/src/otp.rs
index a8dd20b..ee142c7 100644
--- a/src/otp.rs
+++ b/src/otp.rs
@@ -35,7 +35,7 @@ pub trait ConfigureOtp {
     /// # use nitrokey::Error;
     ///
     /// # fn try_main() -> Result<(), Error> {
-    /// let mut device = nitrokey::connect()?;
+    /// let device = nitrokey::connect()?;
     /// let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::SixDigits);
     /// match device.authenticate_admin("12345678") {
     ///     Ok(mut admin) => {
@@ -44,7 +44,7 @@ pub trait ConfigureOtp {
     ///             Err(err) => eprintln!("Could not write slot: {}", err),
     ///         }
     ///     },
-    ///     Err(err) => eprintln!("Could not authenticate as admin: {}", err),
+    ///     Err((_, err)) => eprintln!("Could not authenticate as admin: {}", err),
     /// }
     /// #     Ok(())
     /// # }
@@ -71,7 +71,7 @@ pub trait ConfigureOtp {
     /// # use nitrokey::Error;
     ///
     /// # fn try_main() -> Result<(), Error> {
-    /// let mut device = nitrokey::connect()?;
+    /// let device = nitrokey::connect()?;
     /// let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::EightDigits);
     /// match device.authenticate_admin("12345678") {
     ///     Ok(mut admin) => {
@@ -80,7 +80,7 @@ pub trait ConfigureOtp {
     ///             Err(err) => eprintln!("Could not write slot: {}", err),
     ///         }
     ///     },
-    ///     Err(err) => eprintln!("Could not authenticate as admin: {}", err),
+    ///     Err((_, err)) => eprintln!("Could not authenticate as admin: {}", err),
     /// }
     /// #     Ok(())
     /// # }
@@ -104,7 +104,7 @@ pub trait ConfigureOtp {
     /// # use nitrokey::Error;
     ///
     /// # fn try_main() -> Result<(), Error> {
-    /// let mut device = nitrokey::connect()?;
+    /// let device = nitrokey::connect()?;
     /// match device.authenticate_admin("12345678") {
     ///     Ok(mut admin) => {
     ///         match admin.erase_hotp_slot(1) {
@@ -112,7 +112,7 @@ pub trait ConfigureOtp {
     ///             Err(err) => eprintln!("Could not erase slot: {}", err),
     ///         }
     ///     },
-    ///     Err(err) => eprintln!("Could not authenticate as admin: {}", err),
+    ///     Err((_, err)) => eprintln!("Could not authenticate as admin: {}", err),
     /// }
     /// #     Ok(())
     /// # }
@@ -134,7 +134,7 @@ pub trait ConfigureOtp {
     /// # use nitrokey::Error;
     ///
     /// # fn try_main() -> Result<(), Error> {
-    /// let mut device = nitrokey::connect()?;
+    /// let device = nitrokey::connect()?;
     /// match device.authenticate_admin("12345678") {
     ///     Ok(mut admin) => {
     ///         match admin.erase_totp_slot(1) {
@@ -142,7 +142,7 @@ pub trait ConfigureOtp {
     ///             Err(err) => eprintln!("Could not erase slot: {}", err),
     ///         }
     ///     },
-    ///     Err(err) => eprintln!("Could not authenticate as admin: {}", err),
+    ///     Err((_, err)) => eprintln!("Could not authenticate as admin: {}", err),
     /// }
     /// #     Ok(())
     /// # }
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 ecc3cfa..5c52024 100644
--- a/tests/device.rs
+++ b/tests/device.rs
@@ -97,34 +97,41 @@ fn get_firmware_version(device: Pro) {
     assert!(version.minor > 0);
 }
 
-fn admin_retry<T: Authenticate + Device>(device: &mut T, suffix: &str, count: u8) {
-    assert_any_ok!(device.authenticate_admin(&(DEFAULT_ADMIN_PIN.to_owned() + suffix)));
+fn admin_retry<T: Authenticate + Device>(device: T, suffix: &str, count: u8) -> T {
+    let result = device.authenticate_admin(&(DEFAULT_ADMIN_PIN.to_owned() + suffix));
+    let device = match result {
+        Ok(admin) => admin.device(),
+        Err((device, _)) => device,
+    };
     assert_ok!(count, device.get_admin_retry_count());
+    return device;
 }
 
-fn user_retry<T: Authenticate + Device>(device: &mut T, suffix: &str, count: u8) {
-    assert_any_ok!(device.authenticate_user(&(DEFAULT_USER_PIN.to_owned() + suffix)));
+fn user_retry<T: Authenticate + Device>(device: T, suffix: &str, count: u8) -> T {
+    let result = device.authenticate_user(&(DEFAULT_USER_PIN.to_owned() + suffix));
+    let device = match result {
+        Ok(admin) => admin.device(),
+        Err((device, _)) => device,
+    };
     assert_ok!(count, device.get_user_retry_count());
+    return device;
 }
 
 #[test_device]
 fn get_retry_count(device: DeviceWrapper) {
-    let mut device = device;
-
-    admin_retry(&mut device, "", 3);
-    admin_retry(&mut device, "123", 2);
-    admin_retry(&mut device, "456", 1);
-    admin_retry(&mut device, "", 3);
-
-    user_retry(&mut device, "", 3);
-    user_retry(&mut device, "123", 2);
-    user_retry(&mut device, "456", 1);
-    user_retry(&mut device, "", 3);
+    let device = admin_retry(device, "", 3);
+    let device = admin_retry(device, "123", 2);
+    let device = admin_retry(device, "456", 1);
+    let device = admin_retry(device, "", 3);
+
+    let device = user_retry(device, "", 3);
+    let device = user_retry(device, "123", 2);
+    let device = user_retry(device, "456", 1);
+    user_retry(device, "", 3);
 }
 
 #[test_device]
 fn config(device: DeviceWrapper) {
-    let mut device = device;
     let mut admin = unwrap_ok!(device.authenticate_admin(DEFAULT_ADMIN_PIN));
 
     let config = Config::new(None, None, None, true);
@@ -145,24 +152,22 @@ fn config(device: DeviceWrapper) {
 
 #[test_device]
 fn change_user_pin(device: DeviceWrapper) {
-    let mut device = device;
-    assert_any_ok!(device.authenticate_user(DEFAULT_USER_PIN));
-    assert_cmd_err!(
-        CommandError::WrongPassword,
-        device.authenticate_user(USER_NEW_PASSWORD)
-    );
+    let device = device.authenticate_user(DEFAULT_USER_PIN).unwrap().device();
+    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_cmd_err!(
-        CommandError::WrongPassword,
-        device.authenticate_user(DEFAULT_USER_PIN)
-    );
-    assert_any_ok!(device.authenticate_user(USER_NEW_PASSWORD));
+    let device = device.authenticate_user(DEFAULT_USER_PIN).unwrap_err().0;
+    let device = device
+        .authenticate_user(USER_NEW_PASSWORD)
+        .unwrap()
+        .device();
 
+    let mut device = device;
     let result = device.change_user_pin(DEFAULT_USER_PIN, DEFAULT_USER_PIN);
     assert_cmd_err!(CommandError::WrongPassword, result);
 
@@ -171,32 +176,28 @@ fn change_user_pin(device: DeviceWrapper) {
         device.change_user_pin(USER_NEW_PASSWORD, DEFAULT_USER_PIN)
     );
 
-    assert_any_ok!(device.authenticate_user(DEFAULT_USER_PIN));
-    assert_cmd_err!(
-        CommandError::WrongPassword,
-        device.authenticate_user(USER_NEW_PASSWORD)
-    );
+    let device = device.authenticate_user(DEFAULT_USER_PIN).unwrap().device();
+    assert!(device.authenticate_user(USER_NEW_PASSWORD).is_err());
 }
 
 #[test_device]
 fn change_admin_pin(device: DeviceWrapper) {
-    let mut device = device;
-    assert_any_ok!(device.authenticate_admin(DEFAULT_ADMIN_PIN));
-    assert_cmd_err!(
-        CommandError::WrongPassword,
-        device.authenticate_admin(ADMIN_NEW_PASSWORD)
-    );
+    let device = device
+        .authenticate_admin(DEFAULT_ADMIN_PIN)
+        .unwrap()
+        .device();
+    let mut device = device.authenticate_admin(ADMIN_NEW_PASSWORD).unwrap_err().0;
 
     assert_ok!(
         (),
         device.change_admin_pin(DEFAULT_ADMIN_PIN, ADMIN_NEW_PASSWORD)
     );
 
-    assert_cmd_err!(
-        CommandError::WrongPassword,
-        device.authenticate_admin(DEFAULT_ADMIN_PIN)
-    );
-    assert_any_ok!(device.authenticate_admin(ADMIN_NEW_PASSWORD));
+    let device = device.authenticate_admin(DEFAULT_ADMIN_PIN).unwrap_err().0;
+    let mut device = device
+        .authenticate_admin(ADMIN_NEW_PASSWORD)
+        .unwrap()
+        .device();
 
     assert_cmd_err!(
         CommandError::WrongPassword,
@@ -208,24 +209,31 @@ fn change_admin_pin(device: DeviceWrapper) {
         device.change_admin_pin(ADMIN_NEW_PASSWORD, DEFAULT_ADMIN_PIN)
     );
 
-    assert_any_ok!(device.authenticate_admin(DEFAULT_ADMIN_PIN));
-    assert_cmd_err!(
-        CommandError::WrongPassword,
-        device.authenticate_admin(ADMIN_NEW_PASSWORD)
-    );
+    let device = device
+        .authenticate_admin(DEFAULT_ADMIN_PIN)
+        .unwrap()
+        .device();
+    device.authenticate_admin(ADMIN_NEW_PASSWORD).unwrap_err();
 }
 
-fn require_failed_user_login<D: Authenticate + Device>(device: &mut D, password: &str) {
-    assert_cmd_err!(
-        CommandError::WrongPassword,
-        device.authenticate_user(password)
-    );
+fn require_failed_user_login<D>(device: D, password: &str, error: CommandError) -> D
+where
+    D: Device + Authenticate,
+    nitrokey::User<D>: std::fmt::Debug,
+{
+    let result = device.authenticate_user(password);
+    assert!(result.is_err());
+    let err = result.unwrap_err();
+    match err.1 {
+        Error::CommandError(err) => assert_eq!(error, err),
+        _ => assert!(false),
+    };
+    err.0
 }
 
 #[test_device]
 fn unlock_user_pin(device: DeviceWrapper) {
-    let mut device = device;
-    assert_any_ok!(device.authenticate_user(DEFAULT_USER_PIN));
+    let mut device = device.authenticate_user(DEFAULT_USER_PIN).unwrap().device();
     assert_ok!(
         (),
         device.unlock_user_pin(DEFAULT_ADMIN_PIN, DEFAULT_USER_PIN)
@@ -237,10 +245,11 @@ fn unlock_user_pin(device: DeviceWrapper) {
 
     // block user PIN
     let wrong_password = DEFAULT_USER_PIN.to_owned() + "foo";
-    require_failed_user_login(&mut device, &wrong_password);
-    require_failed_user_login(&mut device, &wrong_password);
-    require_failed_user_login(&mut device, &wrong_password);
-    require_failed_user_login(&mut device, DEFAULT_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);
 
     // unblock with current PIN
     assert_cmd_err!(
@@ -251,13 +260,14 @@ fn unlock_user_pin(device: DeviceWrapper) {
         (),
         device.unlock_user_pin(DEFAULT_ADMIN_PIN, DEFAULT_USER_PIN)
     );
-    assert_any_ok!(device.authenticate_user(DEFAULT_USER_PIN));
+    let device = device.authenticate_user(DEFAULT_USER_PIN).unwrap().device();
 
     // block user PIN
-    require_failed_user_login(&mut device, &wrong_password);
-    require_failed_user_login(&mut device, &wrong_password);
-    require_failed_user_login(&mut device, &wrong_password);
-    require_failed_user_login(&mut device, DEFAULT_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);
 
     // unblock with new PIN
     assert_cmd_err!(
@@ -286,11 +296,11 @@ fn assert_utf8_err_or_ne(left: &str, right: Result<String, Error>) {
 
 #[test_device]
 fn factory_reset(device: DeviceWrapper) {
-    let mut device = device;
     let mut admin = unwrap_ok!(device.authenticate_admin(DEFAULT_ADMIN_PIN));
     let otp_data = OtpSlotData::new(1, "test", "0123468790", OtpMode::SixDigits);
     assert_ok!((), admin.write_totp_slot(otp_data, 30));
 
+    let mut device = admin.device();
     let mut pws = unwrap_ok!(device.get_password_safe(DEFAULT_USER_PIN));
     assert_ok!((), pws.write_slot(0, "test", "testlogin", "testpw"));
     drop(pws);
@@ -314,11 +324,15 @@ fn factory_reset(device: DeviceWrapper) {
     );
     assert_ok!((), device.factory_reset(ADMIN_NEW_PASSWORD));
 
-    assert_any_ok!(device.authenticate_admin(DEFAULT_ADMIN_PIN));
+    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));
 
+    let mut device = user.device();
     let pws = unwrap_ok!(device.get_password_safe(DEFAULT_USER_PIN));
     assert_utf8_err_or_ne("test", pws.get_slot_name(0));
     assert_utf8_err_or_ne("testlogin", pws.get_slot_login(0));
@@ -341,7 +355,10 @@ fn build_aes_key(device: DeviceWrapper) {
     );
     assert_ok!((), device.build_aes_key(DEFAULT_ADMIN_PIN));
 
-    assert_any_ok!(device.authenticate_admin(DEFAULT_ADMIN_PIN));
+    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));
diff --git a/tests/otp.rs b/tests/otp.rs
index d55d54a..c0bbecf 100644
--- a/tests/otp.rs
+++ b/tests/otp.rs
@@ -3,6 +3,7 @@
 
 mod util;
 
+use std::fmt::Debug;
 use std::ops::DerefMut;
 
 use nitrokey::{
@@ -35,9 +36,10 @@ enum TotpTimestampSize {
     U64,
 }
 
-fn make_admin_test_device<'a, T>(device: &'a mut T) -> Admin<'a, T>
+fn make_admin_test_device<T>(device: T) -> Admin<T>
 where
     T: Device,
+    (T, nitrokey::Error): Debug,
 {
     unwrap_ok!(device.authenticate_admin(DEFAULT_ADMIN_PIN))
 }
@@ -66,8 +68,7 @@ fn set_time(device: DeviceWrapper) {
 
 #[test_device]
 fn hotp_no_pin(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, false);
     assert_ok!((), admin.write_config(config));
 
@@ -78,38 +79,36 @@ fn hotp_no_pin(device: DeviceWrapper) {
     check_hotp_codes(admin.deref_mut(), 5);
 
     configure_hotp(&mut admin, 0);
-    check_hotp_codes(&mut device, 0);
+    check_hotp_codes(&mut admin.device(), 0);
 }
 
 #[test_device]
 fn hotp_pin(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, true);
     assert_ok!((), admin.write_config(config));
 
     configure_hotp(&mut admin, 0);
-    let mut user = unwrap_ok!(device.authenticate_user(DEFAULT_USER_PIN));
+    let mut user = unwrap_ok!(admin.device().authenticate_user(DEFAULT_USER_PIN));
     check_hotp_codes(&mut user, 0);
 
-    assert_cmd_err!(CommandError::NotAuthorized, user.get_hotp_code(1));
+    assert_cmd_err!(CommandError::NotAuthorized, user.device().get_hotp_code(1));
 }
 
 #[test_device]
 fn hotp_slot_name(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let slot_data = OtpSlotData::new(1, "test-hotp", HOTP_SECRET, OtpMode::SixDigits);
     assert_ok!((), admin.write_hotp_slot(slot_data, 0));
 
+    let device = admin.device();
     assert_ok!("test-hotp".to_string(), device.get_hotp_slot_name(1));
     assert_lib_err!(LibraryError::InvalidSlot, device.get_hotp_slot_name(4));
 }
 
 #[test_device]
 fn hotp_error(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let slot_data = OtpSlotData::new(1, "", HOTP_SECRET, OtpMode::SixDigits);
     assert_cmd_err!(CommandError::NoName, admin.write_hotp_slot(slot_data, 0));
     let slot_data = OtpSlotData::new(4, "test", HOTP_SECRET, OtpMode::SixDigits);
@@ -128,8 +127,7 @@ fn hotp_error(device: DeviceWrapper) {
 
 #[test_device]
 fn hotp_erase(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, false);
     assert_ok!((), admin.write_config(config));
     let slot_data = OtpSlotData::new(1, "test1", HOTP_SECRET, OtpMode::SixDigits);
@@ -139,6 +137,7 @@ fn hotp_erase(device: DeviceWrapper) {
 
     assert_ok!((), admin.erase_hotp_slot(1));
 
+    let mut device = admin.device();
     let result = device.get_hotp_slot_name(1);
     assert_cmd_err!(CommandError::SlotNotProgrammed, result);
     let result = device.get_hotp_code(1);
@@ -175,8 +174,7 @@ fn check_totp_codes(device: &mut GenerateOtp, factor: u64, timestamp_size: TotpT
 
 #[test_device]
 fn totp_no_pin(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, false);
     assert_ok!((), admin.write_config(config));
 
@@ -187,15 +185,14 @@ fn totp_no_pin(device: DeviceWrapper) {
     check_totp_codes(admin.deref_mut(), 2, TotpTimestampSize::U32);
 
     configure_totp(&mut admin, 1);
-    check_totp_codes(&mut device, 1, TotpTimestampSize::U32);
+    check_totp_codes(&mut admin.device(), 1, TotpTimestampSize::U32);
 }
 
 #[test_device]
 // Nitrokey Storage does only support timestamps that fit in a 32-bit
 // unsigned integer, so don't test with it.
 fn totp_no_pin_64(device: Pro) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, false);
     assert_ok!((), admin.write_config(config));
 
@@ -206,45 +203,43 @@ fn totp_no_pin_64(device: Pro) {
     check_totp_codes(admin.deref_mut(), 2, TotpTimestampSize::U64);
 
     configure_totp(&mut admin, 1);
-    check_totp_codes(&mut device, 1, TotpTimestampSize::U64);
+    check_totp_codes(&mut admin.device(), 1, TotpTimestampSize::U64);
 }
 
 #[test_device]
 fn totp_pin(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, true);
     assert_ok!((), admin.write_config(config));
 
     configure_totp(&mut admin, 1);
-    let mut user = unwrap_ok!(device.authenticate_user(DEFAULT_USER_PIN));
+    let mut user = unwrap_ok!(admin.device().authenticate_user(DEFAULT_USER_PIN));
     check_totp_codes(&mut user, 1, TotpTimestampSize::U32);
 
-    assert_cmd_err!(CommandError::NotAuthorized, user.get_totp_code(1));
+    assert_cmd_err!(CommandError::NotAuthorized, user.device().get_totp_code(1));
 }
 
 #[test_device]
 // See comment for totp_no_pin_64.
 fn totp_pin_64(device: Pro) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, true);
     assert_ok!((), admin.write_config(config));
 
     configure_totp(&mut admin, 1);
-    let mut user = unwrap_ok!(admin.authenticate_user(DEFAULT_USER_PIN));
+    let mut user = unwrap_ok!(admin.device().authenticate_user(DEFAULT_USER_PIN));
     check_totp_codes(&mut user, 1, TotpTimestampSize::U64);
 
-    assert_cmd_err!(CommandError::NotAuthorized, device.get_totp_code(1));
+    assert_cmd_err!(CommandError::NotAuthorized, user.device().get_totp_code(1));
 }
 
 #[test_device]
 fn totp_slot_name(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let slot_data = OtpSlotData::new(1, "test-totp", TOTP_SECRET, OtpMode::EightDigits);
     assert_ok!((), admin.write_totp_slot(slot_data, 0));
 
+    let device = admin.device();
     let result = device.get_totp_slot_name(1);
     assert_ok!("test-totp", result);
     let result = device.get_totp_slot_name(16);
@@ -253,8 +248,7 @@ fn totp_slot_name(device: DeviceWrapper) {
 
 #[test_device]
 fn totp_error(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let slot_data = OtpSlotData::new(1, "", TOTP_SECRET, OtpMode::SixDigits);
     assert_cmd_err!(CommandError::NoName, admin.write_totp_slot(slot_data, 0));
     let slot_data = OtpSlotData::new(20, "test", TOTP_SECRET, OtpMode::SixDigits);
@@ -273,8 +267,7 @@ fn totp_error(device: DeviceWrapper) {
 
 #[test_device]
 fn totp_erase(device: DeviceWrapper) {
-    let mut device = device;
-    let mut admin = make_admin_test_device(&mut device);
+    let mut admin = make_admin_test_device(device);
     let config = Config::new(None, None, None, false);
     assert_ok!((), admin.write_config(config));
     let slot_data = OtpSlotData::new(1, "test1", TOTP_SECRET, OtpMode::SixDigits);
@@ -284,6 +277,7 @@ fn totp_erase(device: DeviceWrapper) {
 
     assert_ok!((), admin.erase_totp_slot(1));
 
+    let device = admin.device();
     let result = device.get_totp_slot_name(1);
     assert_cmd_err!(CommandError::SlotNotProgrammed, result);
     let result = device.get_totp_code(1);
diff --git a/tests/util/mod.rs b/tests/util/mod.rs
index 5bd19d1..f2b20ec 100644
--- a/tests/util/mod.rs
+++ b/tests/util/mod.rs
@@ -3,7 +3,7 @@
 
 #[macro_export]
 macro_rules! unwrap_ok {
-    ($val:expr) => {
+    ($val:expr) => {{
         match $val {
             Ok(val) => val,
             Err(err) => panic!(
@@ -13,12 +13,12 @@ macro_rules! unwrap_ok {
                 err
             ),
         }
-    };
+    }};
 }
 
 #[macro_export]
 macro_rules! assert_any_ok {
-    ($val:expr) => {
+    ($val:expr) => {{
         match &$val {
             Ok(_) => {}
             Err(err) => panic!(
@@ -28,12 +28,12 @@ macro_rules! assert_any_ok {
                 err
             ),
         }
-    };
+    }};
 }
 
 #[macro_export]
 macro_rules! assert_ok {
-    ($left:expr, $right:expr) => {
+    ($left:expr, $right:expr) => {{
         match &$right {
             Ok(right) => match &$left {
                 left => {
@@ -54,7 +54,7 @@ macro_rules! assert_ok {
                 $left, right_err
             ),
         }
-    };
+    }};
 }
 
 #[macro_export]