Initial commit

13 files changed, 1798 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
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--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+
+/target
+/nitrokey-sys/target
+**/*.rs.bk
+Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..652f454
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "nitrokey"
+version = "0.1.0"
+authors = ["Robin Krahl <robin.krahl@ireas.org>"]
+homepage = "https://code.ireas.org/nitrokey-rs/"
+repository = "https://git.ireas.org/nitrokey-rs/"
+description = "Bindings to libnitrokey for communication with Nitrokey devices"
+keywords = ["nitrokey", "otp"]
+categories = ["api-bindings"]
+license = "MIT"
+
+[features]
+default = ["test-no-device"]
+test-no-device = []
+test-pro = []
+
+[dependencies]
+libc = "0.2"
+nitrokey-sys = { path = "nitrokey-sys" }
+rand = "0.4"
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..1a3601d
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2018 Robin Krahl <robin.krahl@ireas.org>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..1cd8e24
--- /dev/null
+++ b/README.md
@@ -0,0 +1,64 @@
+# nitrokey-rs
+
+A libnitrokey wrapper for Rust providing access to Nitrokey devices.
+
+[Documentation][]
+
+```toml
+[dependencies]
+nitrokey = "0.1.0"
+```
+
+## Compatibility
+
+In order to use this crate, a [`libnitrokey`][] installation is required
+(both development headers and library).  The crate is developed using version
+3.2, but any newer version should work too.
+
+As I only have access to a Nitrokey Pro, this crate only provides support for
+the Nitrokey Pro methods.  If you want to contribute for the Nitrokey Storage,
+please send a mail to [nitrokey-rs-dev@ireas.org][].
+
+### Unsupported Functions
+
+The following functions provided by `libnitrokey` are deliberately not
+supported by `nitrokey-rs`:
+
+- `NK_get_time()`.  This method is useless as it will always cause a timestamp
+  error on the device (see [pull request #114][] for `libnitrokey` for details).
+- `NK_get_status()`.  This method only provides a string representation of
+  data that can be accessed by other methods (firmware version, seriel number,
+  configuration).
+
+## Tests
+
+The default test suite assumes that no Nitrokey device is connected and only
+performs minor sanity checks.  There is another test suite that assumes that a
+Nitrokey Pro is connected (admin password `12345678`, user password `123456`).
+To execute this test suite, run `cargo test --no-default-features --features 
+test-pro -- --test-threads 1`.  Note that this test suite might lock your stick
+if you have different passwords!
+
+The `totp` and `totp_pin` tests can occasionally fail due to bad timing.  Also
+make sure to run the tests sequentially (`--test-threads 1`), otherwise they
+might interfere.
+
+The `get_major_firmware_version` test will fail for newer `libnitrokey`
+versions as it relies on buggy behavior in version 3.2.
+
+## Contact
+
+For bug reports, patches, feature requests or other messages, please send a
+mail to [nitrokey-rs-dev@ireas.org][].
+
+## License
+
+This project is licensed under the [MIT License][].  `libnitrokey` is licensed
+under the [LGPL-3.0][].
+
+[Documentation]: https://docs.rs/nitrokey
+[`libnitrokey`]: https://github.com/nitrokey/libnitrokey
+[nitrokey-rs-dev@ireas.org]: mailto:nitrokey-rs-dev@ireas.org
+[pull request #114]: https://github.com/Nitrokey/libnitrokey/pull/114
+[MIT license]: https://opensource.org/licenses/MIT
+[LGPL-3.0]: https://opensource.org/licenses/lgpl-3.0.html
diff --git a/TODO.md b/TODO.md
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index 0000000..ca239c8
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,42 @@
+- Fix segmentation faults when freeing string literals with old Nitrokey
+  versions.
+- Add support and tests for the Nitrokey Storage.
+- Add support for the currently unsupported commands:
+  - `NK_lock_device`
+  - `NK_factory_reset`
+  - `NK_build_aes_key`
+  - `NK_unlock_user_password`
+  - `NK_erase_hotp_slot`
+  - `NK_erase_totp_slot`
+  - `NK_change_admin_PIN`
+  - `NK_change_user_PIN`
+  - `NK_enable_password_safe`
+  - `NK_get_password_safe_slot_status`
+  - `NK_get_password_safe_slot_name`
+  - `NK_get_password_safe_slot_login`
+  - `NK_get_password_safe_slot_password`
+  - `NK_write_password_safe_slot`
+  - `NK_erase_password_safe_slot`
+  - `NK_is_AES_supported`
+  - `NK_send_startup`
+  - `NK_unlock_encrypted_volume`
+  - `NK_lock_encrypted_volume`
+  - `NK_unlock_hidden_volume`
+  - `NK_lock_hidden_volume`
+  - `NK_create_hidden_volume`
+  - `NK_set_unencrypted_read_only`
+  - `NK_set_unencrypted_read_write`
+  - `NK_export_firmware`
+  - `NK_clear_new_sd_card_warning`
+  - `NK_fill_SD_card_with_random_data`
+  - `NK_change_update_password`
+  - `NK_get_status_storage_as_string`
+  - `NK_get_SD_usage_data_as_string`
+  - `NK_get_progress_bar_value`
+- Fix timing issues with the `totp` and `totp_pin` test cases.
+- Fix the inconsistent method `get_major_firmware_version`.
+- Consider implementing `Drop` instead of the method `disconnect`.
+- Find an example for `set_time`, also adapt `get_totp_code`.
+- Improve log level documentation.
+- Clear passwords from memory.
+- Find a nicer syntax for the `write_config` test.
diff --git a/nitrokey-sys/Cargo.toml b/nitrokey-sys/Cargo.toml
new file mode 100644
index 0000000..e8ff489
--- /dev/null
+++ b/nitrokey-sys/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "nitrokey-sys"
+version = "0.1.0"
+authors = ["Robin Krahl <robin.krahl@ireas.org>"]
+homepage = "https://code.ireas.org/nitrokey-rs/"
+repository = "https://git.ireas.org/nitrokey-rs/"
+description = "Bindings to libnitrokey for communication with Nitrokey devices"
+categories = ["external-ffi-bindings"]
+license = "MIT"
+links = "nitrokey"
+build = "build.rs"
+
+[dependencies]
+
+[build-dependencies]
+bindgen = "0.26.3"
diff --git a/nitrokey-sys/build.rs b/nitrokey-sys/build.rs
new file mode 100644
index 0000000..7b3325c
--- /dev/null
+++ b/nitrokey-sys/build.rs
@@ -0,0 +1,17 @@
+extern crate bindgen;
+
+use std::env;
+use std::path::PathBuf;
+
+fn main() {
+    println!("cargo:rustc-link-lib=nitrokey");
+
+    let bindings = bindgen::Builder::default()
+        .header("wrapper.h")
+        .generate()
+        .expect("Unable to generate bindings");
+    let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
+    bindings
+        .write_to_file(out_path.join("bindings.rs"))
+        .expect("Could not write bindings");
+}
diff --git a/nitrokey-sys/src/lib.rs b/nitrokey-sys/src/lib.rs
new file mode 100644
index 0000000..0641e13
--- /dev/null
+++ b/nitrokey-sys/src/lib.rs
@@ -0,0 +1,29 @@
+#![allow(non_upper_case_globals)]
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+
+include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::ffi::CString;
+
+    #[test]
+    fn login_auto() {
+        unsafe {
+            assert_eq!(0, NK_login_auto());
+        }
+    }
+
+    #[test]
+    fn login() {
+        unsafe {
+            // Unconnected
+            assert_eq!(0, NK_login(CString::new("S").unwrap().as_ptr()));
+            assert_eq!(0, NK_login(CString::new("P").unwrap().as_ptr()));
+            // Unsupported model
+            assert_eq!(0, NK_login(CString::new("T").unwrap().as_ptr()));
+        }
+    }
+}
diff --git a/nitrokey-sys/wrapper.h b/nitrokey-sys/wrapper.h
new file mode 100644
index 0000000..3c8d7cf
--- /dev/null
+++ b/nitrokey-sys/wrapper.h
@@ -0,0 +1,2 @@
+#include <stdbool.h>
+#include <libnitrokey/NK_C_API.h>
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..fdc7954
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,1303 @@
+//! Provides access to a Nitrokey device using the native libnitrokey API.
+//!
+//! # Usage
+//!
+//! Operations on the Nitrokey require different authentication levels.  Some
+//! operations can be performed without authentication, some require user
+//! access, and some require admin access.  This is modelled using the types
+//! [`UnauthenticatedDevice`][], [`UserAuthenticatedDevice`][] and
+//! [`AdminAuthenticatedDevice`][].
+//!
+//! Use [`connect`][] or [`connect_model`][] to obtain an
+//! [`UnauthenticatedDevice`][].  You can then use [`authenticate_user`][] or
+//! [`authenticate_admin`][] to get an authenticated device.  You can then use
+//! [`device`][] to go back to the unauthenticated device.
+//!
+//! This makes sure that you can only execute a command if you have the
+//! required access rights.  Otherwise, your code will not compile.  The only
+//! exception are the methods to generate one-time passwords –
+//! [`get_hotp_code`][] and [`get_totp_code`][].  Depending on the stick
+//! configuration, these operations are available without authentication or
+//! with user authentication.
+//!
+//! Per default, libnitrokey writes log messages, for example the packets that
+//! are sent to and received from the stick, to the standard output.  To
+//! change this behaviour, use [`set_debug`][] or [`set_log_level`][].
+//!
+//! # Examples
+//!
+//! Connect to any Nitrokey and print its serial number:
+//!
+//! ```no_run
+//! use nitrokey::Device;
+//! # use nitrokey::CommandError;
+//!
+//! # fn try_main() -> Result<(), CommandError> {
+//! let device = nitrokey::connect()?;
+//! println!("{}", device.get_serial_number()?);
+//! #     Ok(())
+//! # }
+//! ```
+//!
+//! Configure an HOTP slot:
+//!
+//! ```no_run
+//! use nitrokey::{CommandStatus, Device, OtpMode, OtpSlotData};
+//! # use nitrokey::CommandError;
+//!
+//! # fn try_main() -> Result<(), (CommandError)> {
+//! let device = nitrokey::connect()?;
+//! let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::SixDigits);
+//! match device.authenticate_admin("12345678") {
+//!     Ok(admin) => {
+//!         match admin.write_hotp_slot(slot_data, 0) {
+//!             CommandStatus::Success => println!("Successfully wrote slot."),
+//!             CommandStatus::Error(err) => println!("Could not write slot: {:?}", err),
+//!         }
+//!     },
+//!     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
+//! }
+//! #     Ok(())
+//! # }
+//! ```
+//!
+//! Generate an HOTP one-time password:
+//!
+//! ```no_run
+//! use nitrokey::Device;
+//! # use nitrokey::CommandError;
+//!
+//! # fn try_main() -> Result<(), (CommandError)> {
+//! let device = nitrokey::connect()?;
+//! match device.get_hotp_code(1) {
+//!     Ok(code) => println!("Generated HOTP code: {:?}", code),
+//!     Err(err) => println!("Could not generate HOTP code: {:?}", err),
+//! }
+//! #     Ok(())
+//! # }
+//! ```
+//!
+//! [`authenticate_admin`]: struct.UnauthenticatedDevice.html#method.authenticate_admin
+//! [`authenticate_user`]: struct.UnauthenticatedDevice.html#method.authenticate_user
+//! [`connect`]: fn.connect.html
+//! [`connect_model`]: fn.connect_model.html
+//! [`device`]: struct.AuthenticatedDevice.html#method.device
+//! [`get_hotp_code`]: trait.Device.html#method.get_hotp_code
+//! [`get_totp_code`]: trait.Device.html#method.get_totp_code
+//! [`set_debug`]: fn.set_debug.html
+//! [`set_log_level`]: fn.set_log_level.html
+//! [`AdminAuthenticatedDevice`]: struct.AdminAuthenticatedDevice.html
+//! [`UserAuthenticatedDevice`]: struct.UserAuthenticatedDevice.html
+//! [`UnauthenticatedDevice`]: struct.UnauthenticatedDevice.html
+
+extern crate libc;
+extern crate nitrokey_sys;
+extern crate rand;
+
+use std::ffi::CString;
+use std::ffi::CStr;
+use libc::c_int;
+use rand::Rng;
+
+#[cfg(test)]
+mod tests;
+
+/// Modes for one-time password generation.
+#[derive(Debug, PartialEq)]
+pub enum OtpMode {
+    /// Generate one-time passwords with six digits.
+    SixDigits,
+    /// Generate one-time passwords with eight digits.
+    EightDigits,
+}
+
+/// Error types returned by Nitrokey device or by the library.
+#[derive(Debug, PartialEq)]
+pub enum CommandError {
+    /// A packet with a wrong checksum has been sent or received.
+    WrongCrc,
+    /// A command tried to access an OTP slot that does not exist.
+    WrongSlot,
+    /// A command tried to generate an OTP on a slot that is not configured.
+    SlotNotProgrammed,
+    /// The provided password is wrong.
+    WrongPassword,
+    /// You are not authorized for this command or provided a wrong temporary
+    /// password.
+    NotAuthorized,
+    /// An error occured when getting or setting the time.
+    Timestamp,
+    /// You did not provide a name for the OTP slot.
+    NoName,
+    /// This command is not supported by this device.
+    NotSupported,
+    /// This command is unknown.
+    UnknownCommand,
+    /// AES decryptionfailed.
+    AesDecryptionFailed,
+    /// An unknown error occured.
+    Unknown,
+    /// You passed a string containing a null byte.
+    InvalidString,
+    /// You passed an invalid slot.
+    InvalidSlot,
+    /// An error occured during random number generation.
+    RngError,
+}
+
+/// Command execution status.
+#[derive(Debug, PartialEq)]
+pub enum CommandStatus {
+    /// The command was successful.
+    Success,
+    /// An error occured during command execution.
+    Error(CommandError),
+}
+
+/// Log level for libnitrokey.
+#[derive(Debug, PartialEq)]
+pub enum LogLevel {
+    /// Only log error messages.
+    Error,
+    /// Log error messages and warnings.
+    Warning,
+    /// Log error messages, warnings and info messages.
+    Info,
+    /// Log error messages, warnings, info messages and debug messages.
+    DebugL1,
+    /// Log error messages, warnings, info messages and detailed debug
+    /// messages.
+    Debug,
+    /// Log error messages, warnings, info messages and very detailed debug
+    /// messages.
+    DebugL2,
+}
+
+/// Available Nitrokey models.
+#[derive(Debug, PartialEq)]
+pub enum Model {
+    /// The Nitrokey Storage.
+    Storage,
+    /// The Nitrokey Pro.
+    Pro,
+}
+
+/// The configuration for a Nitrokey.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Config {
+    /// If set, the stick will generate a code from the HOTP slot with the
+    /// given number if numlock is pressed.  The slot number must be 0, 1 or 2.
+    pub numlock: Option<u8>,
+    /// If set, the stick will generate a code from the HOTP slot with the
+    /// given number if capslock is pressed.  The slot number must be 0, 1 or 2.
+    pub capslock: Option<u8>,
+    /// If set, the stick will generate a code from the HOTP slot with the
+    /// given number if scrollock is pressed.  The slot number must be 0, 1 or 2.
+    pub scrollock: Option<u8>,
+    /// If set, OTP generation using [`get_hotp_code`][] or [`get_totp_code`][]
+    /// requires user authentication.  Otherwise, OTPs can be generated without
+    /// authentication.
+    ///
+    /// [`get_hotp_code`]: struct.Device.html#method.get_hotp_code
+    /// [`get_totp_code`]: struct.Device.html#method.get_totp_code
+    pub user_password: bool,
+}
+
+#[derive(Debug)]
+struct RawConfig {
+    pub numlock: u8,
+    pub capslock: u8,
+    pub scrollock: u8,
+    pub user_password: bool,
+}
+
+#[derive(Debug)]
+/// A Nitrokey device without user or admin authentication.
+///
+/// Use [`connect`][] or [`connect_model`][] to obtain an instance.  If you
+/// want to execute a command that requires user or admin authentication,
+/// use [`authenticate_admin`][] or [`authenticate_user`][].
+///
+/// # Examples
+///
+/// Authentication with error handling:
+///
+/// ```no_run
+/// use nitrokey::{UnauthenticatedDevice, UserAuthenticatedDevice};
+/// # use nitrokey::CommandError;
+///
+/// fn perform_user_task(device: &UserAuthenticatedDevice) {}
+/// fn perform_other_task(device: &UnauthenticatedDevice) {}
+///
+/// # fn try_main() -> Result<(), CommandError> {
+/// let device = nitrokey::connect()?;
+/// let device = match device.authenticate_user("123456") {
+///     Ok(user) => {
+///         perform_user_task(&user);
+///         user.device()
+///     },
+///     Err((device, err)) => {
+///         println!("Could not authenticate as user: {:?}", err);
+///         device
+///     },
+/// };
+/// perform_other_task(&device);
+/// #     Ok(())
+/// # }
+/// ```
+///
+/// [`authenticate_admin`]: #method.authenticate_admin
+/// [`authenticate_user`]: #method.authenticate_user
+/// [`connect`]: fn.connect.html
+/// [`connect_model`]: fn.connect_model.html
+pub struct UnauthenticatedDevice {}
+
+/// A Nitrokey device with user authentication.
+///
+/// To obtain an instance of this struct, use the [`authenticate_user`][]
+/// method on an [`UnauthenticatedDevice`][].  To get back to an
+/// unauthenticated device, use the [`device`][] method.
+///
+/// [`authenticate_admin`]: struct.UnauthenticatedDevice#method.authenticate_admin
+/// [`device`]: #method.device
+/// [`UnauthenticatedDevice`]: struct.UnauthenticatedDevice.html
+pub struct UserAuthenticatedDevice {
+    device: UnauthenticatedDevice,
+    temp_password: Vec<u8>,
+}
+
+/// A Nitrokey device with admin authentication.
+///
+/// To obtain an instance of this struct, use the [`authenticate_admin`][]
+/// method on an [`UnauthenticatedDevice`][].  To get back to an
+/// unauthenticated device, use the [`device`][] method.
+///
+/// [`authenticate_admin`]: struct.UnauthenticatedDevice#method.authenticate_admin
+/// [`device`]: #method.device
+/// [`UnauthenticatedDevice`]: struct.UnauthenticatedDevice.html
+pub struct AdminAuthenticatedDevice {
+    device: UnauthenticatedDevice,
+    temp_password: Vec<u8>,
+}
+
+/// The configuration for an OTP slot.
+#[derive(Debug)]
+pub struct OtpSlotData {
+    /// The number of the slot – must be less than three for HOTP and less than
+    /// 15 for TOTP.
+    pub number: u8,
+    /// The name of the slot – must not be empty.
+    pub name: String,
+    /// The secret for the slot.
+    pub secret: String,
+    /// The OTP generation mode.
+    pub mode: OtpMode,
+    /// If true, press the enter key after sending an OTP code using double-pressed
+    /// numlock, capslock or scrolllock.
+    pub use_enter: bool,
+    /// Set the token ID [OATH Token Identifier Specification][tokspec], section
+    /// “Class A”.
+    ///
+    /// [tokspec]: https://openauthentication.org/token-specs/
+    pub token_id: Option<String>,
+}
+
+#[derive(Debug)]
+struct RawOtpSlotData {
+    pub number: u8,
+    pub name: CString,
+    pub secret: CString,
+    pub mode: OtpMode,
+    pub use_enter: bool,
+    pub use_token_id: bool,
+    pub token_id: CString,
+}
+
+static TEMPORARY_PASSWORD_LENGTH: usize = 25;
+
+/// A Nitrokey device.
+///
+/// This trait provides the commands that can be executed without
+/// authentication.  The only exception are the [`get_hotp_code`][] and
+/// [`get_totp_code`][] methods:  It depends on the device configuration
+/// ([`get_config`][]) whether these commands require user authentication
+/// or not.
+///
+/// [`get_config`]: #method.get_config
+/// [`get_hotp_code`]: #method.get_hotp_code
+/// [`get_totp_code`]: #method.get_totp_code
+pub trait Device {
+    /// Closes the connection to this device.  This method consumes the device.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// // perform tasks ...
+    /// device.disconnect();
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn disconnect(self)
+    where
+        Self: std::marker::Sized,
+    {
+        unsafe {
+            nitrokey_sys::NK_logout();
+        }
+    }
+
+    /// Sets the time on the Nitrokey.  This command may set the time to
+    /// arbitrary values.  `time` is the number of seconds since January 1st,
+    /// 1970 (Unix timestamp).
+    ///
+    /// The time is used for TOTP generation (see [`get_totp_code`][]).
+    ///
+    /// # Errors
+    ///
+    /// - [`Timestamp`][] if the time could not be set
+    ///
+    /// [`get_totp_code`]: #method.get_totp_code
+    /// [`Timestamp`]: enum.CommandError.html#variant.Timestamp
+    // TODO: example
+    fn set_time(&self, time: u64) -> CommandStatus {
+        unsafe { CommandStatus::from(nitrokey_sys::NK_totp_set_time(time)) }
+    }
+
+    /// Returns the serial number of the Nitrokey device.  The serial number
+    /// is the string representation of a hex number.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// match device.get_serial_number() {
+    ///     Ok(number) => println!("serial no: {:?}", number),
+    ///     Err(err) => println!("Could not get serial number: {:?}", err),
+    /// };
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn get_serial_number(&self) -> Result<String, CommandError> {
+        unsafe { result_from_string(nitrokey_sys::NK_device_serial_number()) }
+    }
+
+    /// Returns the name of the given HOTP slot.
+    ///
+    /// # Errors
+    ///
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandError, Device};
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// match device.get_hotp_slot_name(1) {
+    ///     Ok(name) => println!("HOTP slot 1: {:?}", name),
+    ///     Err(CommandError::SlotNotProgrammed) => println!("HOTP slot 1 not programmed"),
+    ///     Err(err) => println!("Could not get slot name: {:?}", err),
+    /// };
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    fn get_hotp_slot_name(&self, slot: u8) -> Result<String, CommandError> {
+        unsafe { result_from_string(nitrokey_sys::NK_get_hotp_slot_name(slot)) }
+    }
+
+    /// Returns the name of the given TOTP slot.
+    ///
+    /// # Errors
+    ///
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandError, Device};
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// match device.get_totp_slot_name(1) {
+    ///     Ok(name) => println!("TOTP slot 1: {:?}", name),
+    ///     Err(CommandError::SlotNotProgrammed) => println!("TOTP slot 1 not programmed"),
+    ///     Err(err) => println!("Could not get slot name: {:?}", err),
+    /// };
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    fn get_totp_slot_name(&self, slot: u8) -> Result<String, CommandError> {
+        unsafe { result_from_string(nitrokey_sys::NK_get_totp_slot_name(slot)) }
+    }
+
+    /// Returns the number of remaining authentication attempts for the user.  The
+    /// total number of available attempts is three.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let count = device.get_user_retry_count();
+    /// println!("{} remaining authentication attempts (user)", count);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn get_user_retry_count(&self) -> u8 {
+        unsafe { nitrokey_sys::NK_get_user_retry_count() }
+    }
+
+    /// Returns the number of remaining authentication attempts for the admin.  The
+    /// total number of available attempts is three.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let count = device.get_admin_retry_count();
+    /// println!("{} remaining authentication attempts (admin)", count);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn get_admin_retry_count(&self) -> u8 {
+        unsafe { nitrokey_sys::NK_get_admin_retry_count() }
+    }
+
+    /// Returns the major part of the firmware version (should be zero).
+    /// Note that this method is buggy for libnitrokey older than v3.3.  For
+    /// these versions, this method returns the minor part.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// println!("Firmware version: {}.x", device.get_major_firmware_version());
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn get_major_firmware_version(&self) -> i32 {
+        unsafe { nitrokey_sys::NK_get_major_firmware_version() }
+    }
+
+    /// Returns the current configuration of the Nitrokey device.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let config = device.get_config()?;
+    /// println!("numlock binding:          {:?}", config.numlock);
+    /// println!("capslock binding:         {:?}", config.capslock);
+    /// println!("scrollock binding:        {:?}", config.scrollock);
+    /// println!("require password for OTP: {:?}", config.user_password);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn get_config(&self) -> Result<Config, CommandError> {
+        unsafe {
+            let config_ptr = nitrokey_sys::NK_read_config();
+            if config_ptr.is_null() {
+                return Err(get_last_error());
+            }
+            let config_array_ptr = config_ptr as *const [u8; 5];
+            let raw_config = RawConfig::from(*config_array_ptr);
+            libc::free(config_ptr as *mut libc::c_void);
+            return Ok(raw_config.into());
+        }
+    }
+
+    /// Generates an HOTP code on the given slot.  This operation may require
+    /// user authorization, depending on the device configuration (see
+    /// [`get_config`][]).
+    ///
+    /// # Errors
+    ///
+    /// - [`NotAuthorized`][] if OTP generation requires user authentication
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let code = device.get_hotp_code(1)?;
+    /// println!("Generated HOTP code on slot 1: {:?}", code);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`get_config`]: #method.get_config
+    /// [`NotAuthorized`]: enum.CommandError.html#variant.NotAuthorized
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    fn get_hotp_code(&self, slot: u8) -> Result<String, CommandError> {
+        unsafe {
+            return result_from_string(nitrokey_sys::NK_get_hotp_code(slot));
+        }
+    }
+
+    /// Generates a TOTP code on the given slot.  This operation may require
+    /// user authorization, depending on the device configuration (see
+    /// [`get_config`][]).
+    ///
+    /// To make sure that the Nitrokey’s time is in sync, consider calling
+    /// [`set_time`][] before calling this method.
+    ///
+    /// # Errors
+    ///
+    /// - [`NotAuthorized`][] if OTP generation requires user authentication
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let code = device.get_totp_code(1)?;
+    /// println!("Generated TOTP code on slot 1: {:?}", code);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`set_time`]: #method.set_time
+    /// [`get_config`]: #method.get_config
+    /// [`NotAuthorized`]: enum.CommandError.html#variant.NotAuthorized
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    fn get_totp_code(&self, slot: u8) -> Result<String, CommandError> {
+        unsafe {
+            return result_from_string(nitrokey_sys::NK_get_totp_code(slot, 0, 0, 0));
+        }
+    }
+}
+
+trait AuthenticatedDevice {
+    fn new(device: UnauthenticatedDevice, temp_password: Vec<u8>) -> Self;
+}
+
+/// Connects to a Nitrokey device.  This method can be used to connect to any
+/// connected device, both a Nitrokey Pro and a Nitrokey Storage.
+///
+/// # Example
+///
+/// ```
+/// use nitrokey::UnauthenticatedDevice;
+///
+/// fn do_something(device: UnauthenticatedDevice) {}
+///
+/// match nitrokey::connect() {
+///     Ok(device) => do_something(device),
+///     Err(err) => println!("Could not connect to a Nitrokey: {:?}", err),
+/// }
+/// ```
+pub fn connect() -> Result<UnauthenticatedDevice, CommandError> {
+    unsafe {
+        match nitrokey_sys::NK_login_auto() {
+            1 => Ok(UnauthenticatedDevice {}),
+            _ => Err(CommandError::Unknown),
+        }
+    }
+}
+
+/// Connects to a Nitrokey device of the given model.
+///
+/// # Example
+///
+/// ```
+/// use nitrokey::{Model, UnauthenticatedDevice};
+///
+/// fn do_something(device: UnauthenticatedDevice) {}
+///
+/// match nitrokey::connect_model(Model::Pro) {
+///     Ok(device) => do_something(device),
+///     Err(err) => println!("Could not connect to a Nitrokey Pro: {:?}", err),
+/// }
+/// ```
+pub fn connect_model(model: Model) -> Result<UnauthenticatedDevice, CommandError> {
+    let model_string = match model {
+        Model::Storage => "S",
+        Model::Pro => "P",
+    };
+    let model_cstring = CString::new(model_string);
+    if model_cstring.is_err() {
+        return Err(CommandError::InvalidString);
+    }
+    let model = model_cstring.unwrap();
+    unsafe {
+        return match nitrokey_sys::NK_login(model.as_ptr()) {
+            1 => Ok(UnauthenticatedDevice {}),
+            rv => Err(CommandError::from(rv)),
+        };
+    }
+}
+
+/// Enables or disables debug output.  Calling this method with `true` is
+/// equivalent to setting the log level to `Debug`; calling it with `false` is
+/// equivalent to the log level `Error` (see [`set_log_level`][]).
+///
+/// If debug output is enabled, detailed information about the communication
+/// with the Nitrokey device is printed to the standard output.
+///
+/// [`set_log_level`]: fn.set_log_level.html
+pub fn set_debug(state: bool) {
+    unsafe {
+        nitrokey_sys::NK_set_debug(state);
+    }
+}
+
+/// Sets the log level for libnitrokey.  All log messages are written to the
+/// standard output or standard errror.
+pub fn set_log_level(level: LogLevel) {
+    unsafe {
+        nitrokey_sys::NK_set_debug_level(level.into());
+    }
+}
+
+fn config_otp_slot_to_option(value: u8) -> Option<u8> {
+    if value < 3 {
+        return Some(value);
+    }
+    None
+}
+
+fn option_to_config_otp_slot(value: Option<u8>) -> Result<u8, CommandError> {
+    match value {
+        Some(value) => {
+            if value < 3 {
+                Ok(value)
+            } else {
+                Err(CommandError::InvalidSlot)
+            }
+        }
+        None => Ok(255),
+    }
+}
+
+impl From<c_int> for CommandError {
+    fn from(value: c_int) -> Self {
+        match value {
+            1 => CommandError::WrongCrc,
+            2 => CommandError::WrongSlot,
+            3 => CommandError::SlotNotProgrammed,
+            4 => CommandError::WrongPassword,
+            5 => CommandError::NotAuthorized,
+            6 => CommandError::Timestamp,
+            7 => CommandError::NoName,
+            8 => CommandError::NotSupported,
+            9 => CommandError::UnknownCommand,
+            10 => CommandError::AesDecryptionFailed,
+            _ => CommandError::Unknown,
+        }
+    }
+}
+
+impl From<c_int> for CommandStatus {
+    fn from(value: c_int) -> Self {
+        match value {
+            0 => CommandStatus::Success,
+            other => CommandStatus::Error(CommandError::from(other)),
+        }
+    }
+}
+
+impl Into<i32> for LogLevel {
+    fn into(self) -> i32 {
+        match self {
+            LogLevel::Error => 0,
+            LogLevel::Warning => 1,
+            LogLevel::Info => 2,
+            LogLevel::DebugL1 => 3,
+            LogLevel::Debug => 4,
+            LogLevel::DebugL2 => 5,
+        }
+    }
+}
+
+fn get_last_status() -> CommandStatus {
+    unsafe {
+        let status = nitrokey_sys::NK_get_last_command_status();
+        return CommandStatus::from(status as c_int);
+    }
+}
+
+fn get_last_error() -> CommandError {
+    return match get_last_status() {
+        CommandStatus::Success => CommandError::Unknown,
+        CommandStatus::Error(err) => err,
+    };
+}
+
+fn owned_str_from_ptr(ptr: *const std::os::raw::c_char) -> String {
+    unsafe {
+        return CStr::from_ptr(ptr).to_string_lossy().into_owned();
+    }
+}
+
+fn result_from_string(ptr: *const std::os::raw::c_char) -> Result<String, CommandError> {
+    if ptr.is_null() {
+        return Err(CommandError::Unknown);
+    }
+    unsafe {
+        let s = owned_str_from_ptr(ptr);
+        libc::free(ptr as *mut libc::c_void);
+        if s.is_empty() {
+            return Err(get_last_error());
+        }
+        return Ok(s);
+    }
+}
+
+fn generate_password(length: usize) -> std::io::Result<Vec<u8>> {
+    let mut rng = match rand::OsRng::new() {
+        Ok(rng) => rng,
+        Err(err) => return Err(err),
+    };
+    let mut data = vec![0u8; length];
+    rng.fill_bytes(&mut data[..]);
+    return Ok(data);
+}
+
+impl OtpSlotData {
+    /// Constructs a new instance of this struct.
+    pub fn new(number: u8, name: &str, secret: &str, mode: OtpMode) -> OtpSlotData {
+        OtpSlotData {
+            number,
+            name: String::from(name),
+            secret: String::from(secret),
+            mode,
+            use_enter: false,
+            token_id: None,
+        }
+    }
+}
+
+impl RawOtpSlotData {
+    pub fn new(data: OtpSlotData) -> Result<RawOtpSlotData, CommandError> {
+        let name = CString::new(data.name);
+        let secret = CString::new(data.secret);
+        let use_token_id = data.token_id.is_some();
+        let token_id = CString::new(data.token_id.unwrap_or_else(String::new));
+        if name.is_err() || secret.is_err() || token_id.is_err() {
+            return Err(CommandError::InvalidString);
+        }
+
+        Ok(RawOtpSlotData {
+            number: data.number,
+            name: name.unwrap(),
+            secret: secret.unwrap(),
+            mode: data.mode,
+            use_enter: data.use_enter,
+            use_token_id,
+            token_id: token_id.unwrap(),
+        })
+    }
+}
+
+impl Config {
+    /// Constructs a new instance of this struct.
+    pub fn new(
+        numlock: Option<u8>,
+        capslock: Option<u8>,
+        scrollock: Option<u8>,
+        user_password: bool,
+    ) -> Config {
+        Config {
+            numlock,
+            capslock,
+            scrollock,
+            user_password,
+        }
+    }
+}
+
+impl RawConfig {
+    fn try_from(config: Config) -> Result<RawConfig, CommandError> {
+        Ok(RawConfig {
+            numlock: option_to_config_otp_slot(config.numlock)?,
+            capslock: option_to_config_otp_slot(config.capslock)?,
+            scrollock: option_to_config_otp_slot(config.scrollock)?,
+            user_password: config.user_password,
+        })
+    }
+}
+
+impl From<[u8; 5]> for RawConfig {
+    fn from(data: [u8; 5]) -> Self {
+        RawConfig {
+            numlock: data[0],
+            capslock: data[1],
+            scrollock: data[2],
+            user_password: data[3] != 0,
+        }
+    }
+}
+
+impl Into<Config> for RawConfig {
+    fn into(self) -> Config {
+        Config {
+            numlock: config_otp_slot_to_option(self.numlock),
+            capslock: config_otp_slot_to_option(self.capslock),
+            scrollock: config_otp_slot_to_option(self.scrollock),
+            user_password: self.user_password,
+        }
+    }
+}
+
+impl UnauthenticatedDevice {
+    fn authenticate<D, T>(
+        self,
+        password: &str,
+        callback: T,
+    ) -> Result<D, (UnauthenticatedDevice, CommandError)>
+    where
+        D: AuthenticatedDevice,
+        T: Fn(*const i8, *const i8) -> c_int,
+    {
+        let temp_password = match generate_password(TEMPORARY_PASSWORD_LENGTH) {
+            Ok(pw) => pw,
+            Err(_) => return Err((self, CommandError::RngError)),
+        };
+        let password = CString::new(password);
+        if password.is_err() {
+            return Err((self, CommandError::InvalidString));
+        }
+
+        let pw = password.unwrap();
+        let password_ptr = pw.as_ptr();
+        let temp_password_ptr = temp_password.as_ptr() as *const i8;
+        return match callback(password_ptr, temp_password_ptr) {
+            0 => Ok(D::new(self, temp_password)),
+            rv => Err((self, CommandError::from(rv))),
+        };
+    }
+
+    /// Performs user authentication.  This method consumes the device.  If
+    /// successful, an authenticated device is returned.  Otherwise, the
+    /// current unauthenticated device and the error are returned.
+    ///
+    /// This method generates a random temporary password that is used for all
+    /// operations that require user access.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidString`][] if the provided user password contains a null byte
+    /// - [`RngError`][] if the generation of the temporary password failed
+    /// - [`WrongPassword`][] if the provided user password is wrong
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{UnauthenticatedDevice, UserAuthenticatedDevice};
+    /// # use nitrokey::CommandError;
+    ///
+    /// fn perform_user_task(device: &UserAuthenticatedDevice) {}
+    /// fn perform_other_task(device: &UnauthenticatedDevice) {}
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let device = match device.authenticate_user("123456") {
+    ///     Ok(user) => {
+    ///         perform_user_task(&user);
+    ///         user.device()
+    ///     },
+    ///     Err((device, err)) => {
+    ///         println!("Could not authenticate as user: {:?}", err);
+    ///         device
+    ///     },
+    /// };
+    /// perform_other_task(&device);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
+    /// [`RngError`]: enum.CommandError.html#variant.RngError
+    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
+    pub fn authenticate_user(
+        self,
+        password: &str,
+    ) -> Result<UserAuthenticatedDevice, (UnauthenticatedDevice, CommandError)> {
+        return self.authenticate(password, |password_ptr, temp_password_ptr| unsafe {
+            nitrokey_sys::NK_user_authenticate(password_ptr, temp_password_ptr)
+        });
+    }
+
+    /// Performs admin authentication.  This method consumes the device.  If
+    /// successful, an authenticated device is returned.  Otherwise, the
+    /// current unauthenticated device and the error are returned.
+    ///
+    /// This method generates a random temporary password that is used for all
+    /// operations that require admin access.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidString`][] if the provided admin password contains a null byte
+    /// - [`RngError`][] if the generation of the temporary password failed
+    /// - [`WrongPassword`][] if the provided admin password is wrong
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{AdminAuthenticatedDevice, UnauthenticatedDevice};
+    /// # use nitrokey::CommandError;
+    ///
+    /// fn perform_admin_task(device: &AdminAuthenticatedDevice) {}
+    /// fn perform_other_task(device: &UnauthenticatedDevice) {}
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let device = match device.authenticate_admin("123456") {
+    ///     Ok(admin) => {
+    ///         perform_admin_task(&admin);
+    ///         admin.device()
+    ///     },
+    ///     Err((device, err)) => {
+    ///         println!("Could not authenticate as admin: {:?}", err);
+    ///         device
+    ///     },
+    /// };
+    /// perform_other_task(&device);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
+    /// [`RngError`]: enum.CommandError.html#variant.RngError
+    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
+    pub fn authenticate_admin(
+        self,
+        password: &str,
+    ) -> Result<AdminAuthenticatedDevice, (UnauthenticatedDevice, CommandError)> {
+        return self.authenticate(password, |password_ptr, temp_password_ptr| unsafe {
+            nitrokey_sys::NK_first_authenticate(password_ptr, temp_password_ptr)
+        });
+    }
+}
+
+impl Device for UnauthenticatedDevice {}
+
+impl UserAuthenticatedDevice {
+    /// 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) -> UnauthenticatedDevice {
+        self.device
+    }
+}
+
+impl Device for UserAuthenticatedDevice {
+    /// Generates an HOTP code on the given slot.  This operation may not
+    /// require user authorization, depending on the device configuration (see
+    /// [`get_config`][]).
+    ///
+    /// # Errors
+    ///
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// match device.authenticate_user("123456") {
+    ///     Ok(user) => {
+    ///         let code = user.get_hotp_code(1)?;
+    ///         println!("Generated HOTP code on slot 1: {:?}", code);
+    ///     },
+    ///     Err(err) => println!("Could not authenticate: {:?}", err),
+    /// };
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`get_config`]: #method.get_config
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    fn get_hotp_code(&self, slot: u8) -> Result<String, CommandError> {
+        unsafe {
+            let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
+            return result_from_string(nitrokey_sys::NK_get_hotp_code_PIN(slot, temp_password_ptr));
+        }
+    }
+
+    /// Generates a TOTP code on the given slot.  This operation may not
+    /// require user authorization, depending on the device configuration (see
+    /// [`get_config`][]).
+    ///
+    /// To make sure that the Nitrokey’s time is in sync, consider calling
+    /// [`set_time`][] before calling this method.
+    ///
+    /// # Errors
+    ///
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// match device.authenticate_user("123456") {
+    ///     Ok(user) => {
+    ///         let code = user.get_totp_code(1)?;
+    ///         println!("Generated TOTP code on slot 1: {:?}", code);
+    ///     },
+    ///     Err(err) => println!("Could not authenticate: {:?}", err),
+    /// };
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`get_config`]: #method.get_config
+    /// [`set_time`]: trait.Device.html#method.set_time
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    fn get_totp_code(&self, slot: u8) -> Result<String, CommandError> {
+        unsafe {
+            let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
+            return result_from_string(nitrokey_sys::NK_get_totp_code_PIN(
+                slot,
+                0,
+                0,
+                0,
+                temp_password_ptr,
+            ));
+        }
+    }
+}
+
+impl AuthenticatedDevice for UserAuthenticatedDevice {
+    fn new(device: UnauthenticatedDevice, temp_password: Vec<u8>) -> Self {
+        UserAuthenticatedDevice {
+            device,
+            temp_password,
+        }
+    }
+}
+
+impl AdminAuthenticatedDevice {
+    /// 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) -> UnauthenticatedDevice {
+        self.device
+    }
+
+    /// Writes the given configuration to the Nitrokey device.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidSlot`][] if the provided numlock, capslock or scrolllock
+    ///   slot is larger than two
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Config;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// let config = Config::new(None, None, None, false);
+    /// match device.authenticate_admin("12345678") {
+    ///     Ok(admin) => {
+    ///         admin.write_config(config);
+    ///         ()
+    ///     },
+    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
+    /// };
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    pub fn write_config(&self, config: Config) -> CommandStatus {
+        let raw_config = match RawConfig::try_from(config) {
+            Ok(raw_config) => raw_config,
+            Err(err) => return CommandStatus::Error(err),
+        };
+        unsafe {
+            let rv = nitrokey_sys::NK_write_config(
+                raw_config.numlock,
+                raw_config.capslock,
+                raw_config.scrollock,
+                raw_config.user_password,
+                false,
+                self.temp_password.as_ptr() as *const i8,
+            );
+            return CommandStatus::from(rv);
+        }
+    }
+
+    fn write_otp_slot<T>(&self, data: OtpSlotData, callback: T) -> CommandStatus
+    where
+        T: Fn(RawOtpSlotData, *const i8) -> c_int,
+    {
+        let raw_data = match RawOtpSlotData::new(data) {
+            Ok(raw_data) => raw_data,
+            Err(err) => return CommandStatus::Error(err),
+        };
+        let temp_password_ptr = self.temp_password.as_ptr() as *const i8;
+        let rv = callback(raw_data, temp_password_ptr);
+        return CommandStatus::from(rv);
+    }
+
+    /// Configure an HOTP slot with the given data and set the HOTP counter to
+    /// the given value (default 0).
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidString`][] if the provided token ID contains a null byte
+    /// - [`NoName`][] if the provided name is empty
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandStatus, Device, OtpMode, OtpSlotData};
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), (CommandError)> {
+    /// let device = nitrokey::connect()?;
+    /// let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::SixDigits);
+    /// match device.authenticate_admin("12345678") {
+    ///     Ok(admin) => {
+    ///         match admin.write_hotp_slot(slot_data, 0) {
+    ///             CommandStatus::Success => println!("Successfully wrote slot."),
+    ///             CommandStatus::Error(err) => println!("Could not write slot: {:?}", err),
+    ///         }
+    ///     },
+    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
+    /// }
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
+    /// [`NoName`]: enum.CommandError.html#variant.NoName
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    pub fn write_hotp_slot(&self, data: OtpSlotData, counter: u64) -> CommandStatus {
+        return self.write_otp_slot(data, |raw_data: RawOtpSlotData, temp_password_ptr| unsafe {
+            nitrokey_sys::NK_write_hotp_slot(
+                raw_data.number,
+                raw_data.name.as_ptr(),
+                raw_data.secret.as_ptr(),
+                counter,
+                raw_data.mode == OtpMode::EightDigits,
+                raw_data.use_enter,
+                raw_data.use_token_id,
+                raw_data.token_id.as_ptr(),
+                temp_password_ptr,
+            )
+        });
+    }
+
+    /// Configure a TOTP slot with the given data and set the TOTP time window
+    /// to the given value (default 30).
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidString`][] if the provided token ID contains a null byte
+    /// - [`NoName`][] if the provided name is empty
+    /// - [`WrongSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandStatus, Device, OtpMode, OtpSlotData};
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), (CommandError)> {
+    /// let device = nitrokey::connect()?;
+    /// let slot_data = OtpSlotData::new(1, "test", "01234567890123456689", OtpMode::EightDigits);
+    /// match device.authenticate_admin("12345678") {
+    ///     Ok(admin) => {
+    ///         match admin.write_totp_slot(slot_data, 30) {
+    ///             CommandStatus::Success => println!("Successfully wrote slot."),
+    ///             CommandStatus::Error(err) => println!("Could not write slot: {:?}", err),
+    ///         }
+    ///     },
+    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
+    /// }
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
+    /// [`NoName`]: enum.CommandError.html#variant.NoName
+    /// [`WrongSlot`]: enum.CommandError.html#variant.WrongSlot
+    pub fn write_totp_slot(&self, data: OtpSlotData, time_window: u16) -> CommandStatus {
+        return self.write_otp_slot(data, |raw_data: RawOtpSlotData, temp_password_ptr| unsafe {
+            nitrokey_sys::NK_write_totp_slot(
+                raw_data.number,
+                raw_data.name.as_ptr(),
+                raw_data.secret.as_ptr(),
+                time_window,
+                raw_data.mode == OtpMode::EightDigits,
+                raw_data.use_enter,
+                raw_data.use_token_id,
+                raw_data.token_id.as_ptr(),
+                temp_password_ptr,
+            )
+        });
+    }
+}
+
+impl Device for AdminAuthenticatedDevice {}
+
+impl AuthenticatedDevice for AdminAuthenticatedDevice {
+    fn new(device: UnauthenticatedDevice, temp_password: Vec<u8>) -> Self {
+        AdminAuthenticatedDevice {
+            device,
+            temp_password,
+        }
+    }
+}
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
new file mode 100644
index 0000000..5f01b67
--- /dev/null
+++ b/src/tests/mod.rs
@@ -0,0 +1,2 @@
+mod no_device;
+mod pro;
diff --git a/src/tests/no_device.rs b/src/tests/no_device.rs
new file mode 100644
index 0000000..04c5c8a
--- /dev/null
+++ b/src/tests/no_device.rs
@@ -0,0 +1,9 @@
+use Model;
+
+#[test]
+#[cfg_attr(not(feature = "test-no-device"), ignore)]
+fn connect() {
+    assert!(::connect().is_err());
+    assert!(::connect_model(Model::Storage).is_err());
+    assert!(::connect_model(Model::Pro).is_err());
+}
diff --git a/src/tests/pro.rs b/src/tests/pro.rs
new file mode 100644
index 0000000..7fa8ec3
--- /dev/null
+++ b/src/tests/pro.rs
@@ -0,0 +1,268 @@
+use std::ffi::CStr;
+use std::marker::Sized;
+use {set_debug, AdminAuthenticatedDevice, CommandError, CommandStatus, Config, Device, Model,
+     OtpMode, OtpSlotData, UnauthenticatedDevice};
+
+static ADMIN_PASSWORD: &str = "12345678";
+static USER_PASSWORD: &str = "123456";
+
+// test suite according to RFC 4226, Appendix D
+static HOTP_SECRET: &str = "3132333435363738393031323334353637383930";
+static HOTP_CODES: &[&str] = &[
+    "755224", "287082", "359152", "969429", "338314", "254676", "287922", "162583", "399871",
+    "520489",
+];
+
+// test suite according to RFC 6238, Appendix B
+static TOTP_SECRET: &str = "3132333435363738393031323334353637383930";
+static TOTP_CODES: &[(u64, &str)] = &[
+    (59, "94287082"),
+    (1111111109, "07081804"),
+    (1111111111, "14050471"),
+    (1234567890, "89005924"),
+    (2000000000, "69279037"),
+    (20000000000, "65353130"),
+];
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn connect() {
+    set_debug(false);
+    assert!(::connect().is_ok());
+    assert!(::connect_model(Model::Pro).is_ok());
+    assert!(::connect_model(Model::Storage).is_err());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn disconnect() {
+    set_debug(false);
+    ::connect().unwrap().disconnect();
+    unsafe {
+        let ptr = ::nitrokey_sys::NK_device_serial_number();
+        assert!(!ptr.is_null());
+        let cstr = CStr::from_ptr(ptr);
+        assert_eq!(cstr.to_string_lossy(), "");
+    }
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn get_serial_number() {
+    set_debug(false);
+    let device = ::connect().unwrap();
+    let result = device.get_serial_number();
+    assert!(result.is_ok());
+    let serial_number = result.unwrap();
+    assert!(serial_number.is_ascii());
+    assert!(serial_number.chars().all(|c| c.is_ascii_hexdigit()));
+}
+
+fn configure_hotp(admin: &AdminAuthenticatedDevice) {
+    let slot_data = OtpSlotData::new(1, "test-hotp", HOTP_SECRET, OtpMode::SixDigits);
+    assert_eq!(CommandStatus::Success, admin.write_hotp_slot(slot_data, 0));
+}
+
+fn check_hotp_codes<T: Device>(device: &T)
+where
+    T: Sized,
+{
+    for code in HOTP_CODES {
+        let result = device.get_hotp_code(1);
+        assert_eq!(code, &result.unwrap());
+    }
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn hotp() {
+    set_debug(false);
+    let device = ::connect().unwrap();
+    let admin = device.authenticate_admin(ADMIN_PASSWORD).unwrap();
+    let config = Config::new(None, None, None, false);
+    assert_eq!(CommandStatus::Success, admin.write_config(config));
+
+    configure_hotp(&admin);
+    check_hotp_codes(&admin);
+
+    configure_hotp(&admin);
+    check_hotp_codes(&admin.device());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn hotp_pin() {
+    set_debug(false);
+    let device = ::connect().unwrap();
+    let admin = device.authenticate_admin(ADMIN_PASSWORD).unwrap();
+    let config = Config::new(None, None, None, true);
+    assert_eq!(CommandStatus::Success, admin.write_config(config));
+
+    configure_hotp(&admin);
+    let user = admin.device().authenticate_user(USER_PASSWORD).unwrap();
+    check_hotp_codes(&user);
+
+    // TODO: enable for newer libnitrokey
+    // assert!(user.device().get_hotp_code(1).is_err());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn hotp_slot_name() {
+    set_debug(false);
+    let device = ::connect().unwrap();
+
+    let admin = device.authenticate_admin(ADMIN_PASSWORD).unwrap();
+    let slot_data = OtpSlotData::new(1, "test-hotp", HOTP_SECRET, OtpMode::SixDigits);
+    assert_eq!(CommandStatus::Success, admin.write_hotp_slot(slot_data, 0));
+
+    let result = admin.device().get_hotp_slot_name(1);
+    assert_eq!("test-hotp", result.unwrap());
+}
+
+fn configure_totp(admin: &AdminAuthenticatedDevice) {
+    let slot_data = OtpSlotData::new(1, "test-totp", TOTP_SECRET, OtpMode::EightDigits);
+    assert_eq!(CommandStatus::Success, admin.write_totp_slot(slot_data, 30));
+}
+
+fn check_totp_codes<T: Device>(device: &T)
+where
+    T: Sized,
+{
+    for (i, &(time, code)) in TOTP_CODES.iter().enumerate() {
+        assert_eq!(CommandStatus::Success, device.set_time(time));
+        let result = device.get_totp_code(1);
+        assert!(result.is_ok());
+        let result_code = result.unwrap();
+        assert_eq!(
+            code, result_code,
+            "TOTP code {} should be {} but is {}",
+            i, code, result_code
+        );
+    }
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn totp() {
+    // TODO: this test may fail due to bad timing --> find solution
+    set_debug(false);
+    let device = ::connect().unwrap();
+    let admin = device.authenticate_admin(ADMIN_PASSWORD).unwrap();
+    let config = Config::new(None, None, None, false);
+    assert_eq!(CommandStatus::Success, admin.write_config(config));
+
+    configure_totp(&admin);
+    check_totp_codes(&admin);
+
+    configure_totp(&admin);
+    check_totp_codes(&admin.device());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn totp_pin() {
+    // TODO: this test may fail due to bad timing --> find solution
+    set_debug(false);
+    let device = ::connect().unwrap();
+    let admin = device.authenticate_admin(ADMIN_PASSWORD).unwrap();
+    let config = Config::new(None, None, None, true);
+    assert_eq!(CommandStatus::Success, admin.write_config(config));
+
+    configure_totp(&admin);
+    let user = admin.device().authenticate_user(USER_PASSWORD).unwrap();
+    check_totp_codes(&user);
+
+    // TODO: enable for newer libnitrokey
+    // assert!(user.device().get_totp_code(1).is_err());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn totp_slot_name() {
+    set_debug(false);
+    let device = ::connect().unwrap();
+
+    let admin = device.authenticate_admin(ADMIN_PASSWORD).unwrap();
+    let slot_data = OtpSlotData::new(1, "test-totp", TOTP_SECRET, OtpMode::EightDigits);
+    assert_eq!(CommandStatus::Success, admin.write_totp_slot(slot_data, 0));
+
+    let result = admin.device().get_totp_slot_name(1);
+    assert!(result.is_ok());
+    assert_eq!("test-totp", result.unwrap());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn get_major_firmware_version() {
+    set_debug(false);
+    // TODO fix for different libnitrokey versions
+    assert_eq!(8, ::connect().unwrap().get_major_firmware_version());
+}
+
+fn admin_retry(device: UnauthenticatedDevice, suffix: &str, count: u8) -> UnauthenticatedDevice {
+    let result = device.authenticate_admin(&(ADMIN_PASSWORD.to_owned() + suffix));
+    let device = match result {
+        Ok(admin) => admin.device(),
+        Err((device, _)) => device,
+    };
+    assert_eq!(count, device.get_admin_retry_count());
+    return device;
+}
+
+fn user_retry(device: UnauthenticatedDevice, suffix: &str, count: u8) -> UnauthenticatedDevice {
+    let result = device.authenticate_user(&(USER_PASSWORD.to_owned() + suffix));
+    let device = match result {
+        Ok(admin) => admin.device(),
+        Err((device, _)) => device,
+    };
+    assert_eq!(count, device.get_user_retry_count());
+    return device;
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn get_retry_count() {
+    set_debug(false);
+    let device = ::connect().unwrap();
+
+    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]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn read_write_config() {
+    set_debug(false);
+    let device = ::connect().unwrap();
+
+    let admin = device.authenticate_admin(ADMIN_PASSWORD).unwrap();
+
+    let config = Config::new(None, None, None, true);
+    assert_eq!(CommandStatus::Success, admin.write_config(config));
+    let get_config = admin.get_config().unwrap();
+    assert_eq!(config, get_config);
+
+    let config = Config::new(None, Some(9), None, true);
+    assert_eq!(
+        CommandStatus::Error(CommandError::InvalidSlot),
+        admin.write_config(config)
+    );
+
+    let config = Config::new(Some(1), None, Some(0), false);
+    assert_eq!(CommandStatus::Success, admin.write_config(config));
+    let get_config = admin.get_config().unwrap();
+    assert_eq!(config, get_config);
+
+    let config = Config::new(None, None, None, false);
+    assert_eq!(CommandStatus::Success, admin.write_config(config));
+    let get_config = admin.get_config().unwrap();
+    assert_eq!(config, get_config);
+}