Revert "Store mutable reference to Device in PasswordSafe"

This reverts commit 13006c00dcbd570cf8347d89557834e320427377.

1 files changed, 12 insertions, 12 deletions

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> {