Add Storage::change_update_pin method

This patch adds the change_update_pin method to the Storage struct that
uses the NK_change_update_password function to set the password required
for firmware updates.

5 files changed, 54 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 018ff4d..1611414 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@
 - Add `CommandError::Undefined` to represent errors without further
   information (e. g. a method returned `NULL` unexpectedly).
 - Add error code to `CommandError::Unknown`.
+- Add function `Storage::change_update_pin` that changes the firmware update
+  PIN.
 
 # v0.2.3 (2018-12-31)
 
diff --git a/TODO.md b/TODO.md
index 16ec558..0071dcc 100644
--- a/TODO.md
+++ b/TODO.md
@@ -17,7 +17,6 @@
     - `NK_export_firmware`
     - `NK_clear_new_sd_card_warning`
     - `NK_fill_SD_card_with_random_data`
-    - `NK_change_update_password`
     - `NK_get_SD_usage_data_as_string`
     - `NK_get_progress_bar_value`
     - `NK_list_devices_by_cpuID`
diff --git a/src/device.rs b/src/device.rs
index 33e5410..4b8cc5c 100644
--- a/src/device.rs
+++ b/src/device.rs
@@ -667,6 +667,45 @@ impl Storage {
         }
     }
 
+    /// Changes the update PIN.
+    ///
+    /// The update PIN is used to enable firmware updates.  Unlike the user and the admin PIN, the
+    /// update PIN is not managed by the OpenPGP smart card but by the Nitrokey firmware.  There is
+    /// no retry counter as with the other PIN types.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidString`][] if one of the provided passwords contains a null byte
+    /// - [`WrongPassword`][] if the current update password is wrong
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::Storage::connect()?;
+    /// match device.change_storage_pin("12345678", "87654321") {
+    ///     Ok(()) => println!("Updated update PIN."),
+    ///     Err(err) => println!("Failed to update update PIN: {}", err),
+    /// };
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
+    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
+    pub fn change_update_pin(&self, current: &str, new: &str) -> Result<(), CommandError> {
+        let current_string = get_cstring(current)?;
+        let new_string = get_cstring(new)?;
+        unsafe {
+            get_command_result(nitrokey_sys::NK_change_update_password(
+                    current_string.as_ptr(),
+                    new_string.as_ptr(),
+                    ))
+        }
+    }
+
     /// Enables the encrypted storage volume.
     ///
     /// Once the encrypted volume is enabled, it is presented to the operating system as a block
diff --git a/tests/device.rs b/tests/device.rs
index 4551534..a225d2d 100644
--- a/tests/device.rs
+++ b/tests/device.rs
@@ -6,9 +6,10 @@ use std::{thread, time};
 
 use nitrokey::{Authenticate, CommandError, Config, Device, Storage};
 
-use crate::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
+use crate::util::{Target, ADMIN_PASSWORD, USER_PASSWORD, UPDATE_PIN};
 
 static ADMIN_NEW_PASSWORD: &str = "1234567890";
+static UPDATE_NEW_PIN: &str = "87654321";
 static USER_NEW_PASSWORD: &str = "abcdefghij";
 
 fn count_nitrokey_block_devices() -> usize {
@@ -296,6 +297,16 @@ fn unlock_user_pin() {
 
 #[test]
 #[cfg_attr(not(feature = "test-storage"), ignore)]
+fn change_update_pin() {
+    let device = Storage::connect().unwrap();
+
+    assert_eq!(Err(CommandError::WrongPassword), device.change_update_pin(UPDATE_NEW_PIN, UPDATE_PIN));
+    assert_eq!(Ok(()), device.change_update_pin(UPDATE_PIN, UPDATE_NEW_PIN));
+    assert_eq!(Ok(()), device.change_update_pin(UPDATE_NEW_PIN, UPDATE_PIN));
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-storage"), ignore)]
 fn encrypted_volume() {
     let device = Storage::connect().unwrap();
     assert!(device.lock().is_ok());
diff --git a/tests/util/mod.rs b/tests/util/mod.rs
index c2c94e2..5e495d8 100644
--- a/tests/util/mod.rs
+++ b/tests/util/mod.rs
@@ -1,4 +1,5 @@
 pub static ADMIN_PASSWORD: &str = "12345678";
+pub static UPDATE_PIN: &str = "12345678";
 pub static USER_PASSWORD: &str = "123456";
 
 #[cfg(not(feature = "test-storage"))]