Correct invalid slot handling

While the Nitrokey device would generate a WrongSlot error, libnitrokey
catches these errors and raises an InvalidSlotException with error code
201.  This patch matches this error code to CommandError::InvalidSlot,
corrects the documentation and adds test cases.

To be able to test a failing OTP generation command, we have to adapt
get_string_result to free the string only if successful.  This is due to
the segfault issue in libnitrokey v3.3 (see todo list).

2 files changed, 47 insertions, 15 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 471d481..117659f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -394,8 +394,8 @@ pub trait Device {
     ///
     /// # Errors
     ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
     /// - [`SlotNotProgrammed`][] if the given slot is not configured
-    /// - [`WrongSlot`][] if there is no slot with the given number
     ///
     /// # Example
     ///
@@ -413,8 +413,8 @@ pub trait Device {
     /// # }
     /// ```
     ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
     /// [`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)) }
     }
@@ -423,8 +423,8 @@ pub trait Device {
     ///
     /// # Errors
     ///
+    /// - [`InvalidSlot`][] if there is no slot with the given number
     /// - [`SlotNotProgrammed`][] if the given slot is not configured
-    /// - [`WrongSlot`][] if there is no slot with the given number
     ///
     /// # Example
     ///
@@ -442,8 +442,8 @@ pub trait Device {
     /// # }
     /// ```
     ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
     /// [`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)) }
     }
@@ -569,9 +569,9 @@ pub trait Device {
     ///
     /// # 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
-    /// - [`WrongSlot`][] if there is no slot with the given number
     ///
     /// # Example
     ///
@@ -588,9 +588,9 @@ pub trait Device {
     /// ```
     ///
     /// [`get_config`]: #method.get_config
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
     /// [`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));
@@ -606,9 +606,9 @@ pub trait Device {
     ///
     /// # 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
-    /// - [`WrongSlot`][] if there is no slot with the given number
     ///
     /// # Example
     ///
@@ -626,9 +626,9 @@ pub trait Device {
     ///
     /// [`set_time`]: #method.set_time
     /// [`get_config`]: #method.get_config
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
     /// [`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));
@@ -746,6 +746,7 @@ impl From<c_int> for CommandError {
             8 => CommandError::NotSupported,
             9 => CommandError::UnknownCommand,
             10 => CommandError::AesDecryptionFailed,
+            201 => CommandError::InvalidSlot,
             _ => CommandError::Unknown,
         }
     }
@@ -799,10 +800,11 @@ fn result_from_string(ptr: *const std::os::raw::c_char) -> Result<String, Comman
     }
     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());
         }
+        // TODO: move up for newer libnitrokey versions
+        libc::free(ptr as *mut libc::c_void);
         return Ok(s);
     }
 }
@@ -1214,9 +1216,9 @@ impl AdminAuthenticatedDevice {
     ///
     /// # 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
-    /// - [`WrongSlot`][] if there is no slot with the given number
     ///
     /// # Example
     ///
@@ -1240,9 +1242,9 @@ impl AdminAuthenticatedDevice {
     /// # }
     /// ```
     ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
     /// [`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(
@@ -1264,9 +1266,9 @@ impl AdminAuthenticatedDevice {
     ///
     /// # 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
-    /// - [`WrongSlot`][] if there is no slot with the given number
     ///
     /// # Example
     ///
@@ -1290,9 +1292,9 @@ impl AdminAuthenticatedDevice {
     /// # }
     /// ```
     ///
+    /// [`InvalidSlot`]: enum.CommandError.html#variant.InvalidSlot
     /// [`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(
diff --git a/src/tests/pro.rs b/src/tests/pro.rs
index 8394e47..a508801 100644
--- a/src/tests/pro.rs
+++ b/src/tests/pro.rs
@@ -117,8 +117,23 @@ fn hotp_slot_name() {
     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);
+    let device = admin.device();
+    let result = device.get_hotp_slot_name(1);
     assert_eq!("test-hotp", result.unwrap());
+    let result = device.get_hotp_slot_name(4);
+    assert_eq!(CommandError::InvalidSlot, result.unwrap_err());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn hotp_error() {
+    let admin = get_admin_test_device();
+    let slot_data = OtpSlotData::new(1, "", HOTP_SECRET, OtpMode::SixDigits);
+    assert_eq!(CommandStatus::Error(CommandError::NoName), admin.write_hotp_slot(slot_data, 0));
+    let slot_data = OtpSlotData::new(4, "test", HOTP_SECRET, OtpMode::SixDigits);
+    assert_eq!(CommandStatus::Error(CommandError::InvalidSlot), admin.write_hotp_slot(slot_data, 0));
+    let code = admin.get_hotp_code(4);
+    assert_eq!(CommandError::InvalidSlot, code.unwrap_err());
 }
 
 fn configure_totp(admin: &AdminAuthenticatedDevice) {
@@ -181,9 +196,24 @@ fn totp_slot_name() {
     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);
+    let device = admin.device();
+    let result = device.get_totp_slot_name(1);
     assert!(result.is_ok());
     assert_eq!("test-totp", result.unwrap());
+    let result = device.get_totp_slot_name(16);
+    assert_eq!(CommandError::InvalidSlot, result.unwrap_err());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn totp_error() {
+    let admin = get_admin_test_device();
+    let slot_data = OtpSlotData::new(1, "", HOTP_SECRET, OtpMode::SixDigits);
+    assert_eq!(CommandStatus::Error(CommandError::NoName), admin.write_hotp_slot(slot_data, 0));
+    let slot_data = OtpSlotData::new(4, "test", HOTP_SECRET, OtpMode::SixDigits);
+    assert_eq!(CommandStatus::Error(CommandError::InvalidSlot), admin.write_hotp_slot(slot_data, 0));
+    let code = admin.get_hotp_code(4);
+    assert_eq!(CommandError::InvalidSlot, code.unwrap_err());
 }
 
 #[test]