Restructure code by functionality

In future versions, we want to support not only the Nitrokey Pro, but
also the Nitrokey Storage.  This requires a better code layout.  This
patch introduces two main changes:

First, the OTP-specific methods are moved from the Device trait and the
AdminAuthenticatedDevice struct to the functionality-based traits
ConfigureOtp and GenerateOtp.  This will hopefully make it easier to
integrate the Nitrokey Storage.

Secondly, the code is split into separate modules.  These modules are
currently all private and re-exported in the lib module, but we can
consider making them public in the future.

1 files changed, 350 insertions, 0 deletions

diff --git a/src/otp.rs b/src/otp.rs
new file mode 100644
index 0000000..c0a470f
--- /dev/null
+++ b/src/otp.rs
@@ -0,0 +1,350 @@
+use nitrokey_sys;
+use std::ffi::CString;
+use util::{result_from_string, CommandError, CommandStatus};
+
+/// 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,
+}
+
+/// Provides methods to configure and erase OTP slots on a Nitrokey device.
+pub trait ConfigureOtp {
+    /// Configure an HOTP slot with the given data and set the HOTP counter to
+    /// the given value (default 0).
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    /// - [`InvalidString`][] if the provided token ID contains a null byte
+    /// - [`NoName`][] if the provided name is empty
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandStatus, ConfigureOtp, 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(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
+    /// [`NoName`]: enum.CommandError.html#variant.NoName
+    fn write_hotp_slot(&self, data: OtpSlotData, counter: u64) -> CommandStatus;
+
+    /// Configure a TOTP slot with the given data and set the TOTP time window
+    /// to the given value (default 30).
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    /// - [`InvalidString`][] if the provided token ID contains a null byte
+    /// - [`NoName`][] if the provided name is empty
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandStatus, ConfigureOtp, 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(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
+    /// [`NoName`]: enum.CommandError.html#variant.NoName
+    fn write_totp_slot(&self, data: OtpSlotData, time_window: u16) -> CommandStatus;
+
+    /// Erases an HOTP slot.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandStatus, ConfigureOtp};
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), (CommandError)> {
+    /// let device = nitrokey::connect()?;
+    /// match device.authenticate_admin("12345678") {
+    ///     Ok(admin) => {
+    ///         match admin.erase_hotp_slot(1) {
+    ///             CommandStatus::Success => println!("Successfully erased slot."),
+    ///             CommandStatus::Error(err) => println!("Could not erase slot: {:?}", err),
+    ///         }
+    ///     },
+    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
+    /// }
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    fn erase_hotp_slot(&self, slot: u8) -> CommandStatus;
+
+    /// Erases a TOTP slot.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandStatus, ConfigureOtp};
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), (CommandError)> {
+    /// let device = nitrokey::connect()?;
+    /// match device.authenticate_admin("12345678") {
+    ///     Ok(admin) => {
+    ///         match admin.erase_totp_slot(1) {
+    ///             CommandStatus::Success => println!("Successfully erased slot."),
+    ///             CommandStatus::Error(err) => println!("Could not erase slot: {:?}", err),
+    ///         }
+    ///     },
+    ///     Err((_, err)) => println!("Could not authenticate as admin: {:?}", err),
+    /// }
+    /// #     Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    fn erase_totp_slot(&self, slot: u8) -> CommandStatus;
+}
+
+/// Provides methods to generate OTP codes and to query OTP slots on a Nitrokey
+/// device.
+pub trait GenerateOtp {
+    /// Returns the name of the given HOTP slot.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandError, GenerateOtp};
+    ///
+    /// # 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(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    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
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::{CommandError, GenerateOtp};
+    ///
+    /// # 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(())
+    /// # }
+    /// ```
+    ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    fn get_totp_slot_name(&self, slot: u8) -> Result<String, CommandError> {
+        unsafe { result_from_string(nitrokey_sys::NK_get_totp_slot_name(slot)) }
+    }
+
+    /// Generates an HOTP code on the given slot.  This operation may require
+    /// user authorization, depending on the device configuration (see
+    /// [`get_config`][]).
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    /// - [`NotAuthorized`][] if OTP generation requires user authentication
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::GenerateOtp;
+    /// # 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`]: trait.Device.html#method.get_config
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    /// [`NotAuthorized`]: enum.CommandError.html#variant.NotAuthorized
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    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
+    ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
+    /// - [`NotAuthorized`][] if OTP generation requires user authentication
+    /// - [`SlotNotProgrammed`][] if the given slot is not configured
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::GenerateOtp;
+    /// # 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`]: trait.Device.html#method.set_time
+    /// [`get_config`]: trait.Device.html#method.get_config
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
+    /// [`NotAuthorized`]: enum.CommandError.html#variant.NotAuthorized
+    /// [`SlotNotProgrammed`]: enum.CommandError.html#variant.SlotNotProgrammed
+    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));
+        }
+    }
+}
+
+/// 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)]
+pub 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,
+}
+
+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(),
+        })
+    }
+}