Preserve unknown error code values

The CommandError::Unknown variant, which is used whenever a reported
error code is not known, makes it close to impossible to determine the
root cause of, say, a one-off error, because all information explaining
what went wrong is discarded.
With this change we adjust the Unknown variant to include the error
report. In addition, we introduce a new CommandError variant, Undefined,
that is used when no error code is available.

3 files changed, 50 insertions, 35 deletions

diff --git a/src/device.rs b/src/device.rs
index 9c6608d..33e5410 100644
--- a/src/device.rs
+++ b/src/device.rs
@@ -532,9 +532,9 @@ pub fn connect() -> Result<DeviceWrapper, CommandError> {
         match nitrokey_sys::NK_login_auto() {
             1 => match get_connected_device() {
                 Some(wrapper) => Ok(wrapper),
-                None => Err(CommandError::Unknown),
+                None => Err(CommandError::Undefined),
             },
-            _ => Err(CommandError::Unknown),
+            _ => Err(CommandError::Undefined),
         }
     }
 }
@@ -623,7 +623,7 @@ impl Pro {
         // TODO: maybe Option instead of Result?
         match connect_model(Model::Pro) {
             true => Ok(Pro {}),
-            false => Err(CommandError::Unknown),
+            false => Err(CommandError::Undefined),
         }
     }
 }
@@ -663,7 +663,7 @@ impl Storage {
         // TODO: maybe Option instead of Result?
         match connect_model(Model::Storage) {
             true => Ok(Storage {}),
-            false => Err(CommandError::Unknown),
+            false => Err(CommandError::Undefined),
         }
     }
 
diff --git a/src/util.rs b/src/util.rs
index 315cb34..1ecc0b7 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,3 +1,4 @@
+use std::borrow;
 use std::ffi::{CStr, CString};
 use std::fmt;
 use std::os::raw::{c_char, c_int};
@@ -30,7 +31,9 @@ pub enum CommandError {
     /// AES decryption failed.
     AesDecryptionFailed,
     /// An unknown error occurred.
-    Unknown,
+    Unknown(i64),
+    /// An unspecified error occurred.
+    Undefined,
     /// You passed a string containing a null byte.
     InvalidString,
     /// You passed an invalid slot.
@@ -66,7 +69,7 @@ pub fn owned_str_from_ptr(ptr: *const c_char) -> String {
 
 pub fn result_from_string(ptr: *const c_char) -> Result<String, CommandError> {
     if ptr.is_null() {
-        return Err(CommandError::Unknown);
+        return Err(CommandError::Undefined);
     }
     unsafe {
         let s = owned_str_from_ptr(ptr);
@@ -92,7 +95,7 @@ pub fn get_last_result() -> Result<(), CommandError> {
 
 pub fn get_last_error() -> CommandError {
     return match get_last_result() {
-        Ok(()) => CommandError::Unknown,
+        Ok(()) => CommandError::Undefined,
         Err(err) => err,
     };
 }
@@ -107,26 +110,38 @@ pub fn get_cstring<T: Into<Vec<u8>>>(s: T) -> Result<CString, CommandError> {
     CString::new(s).or(Err(CommandError::InvalidString))
 }
 
-impl fmt::Display for CommandError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let msg = match *self {
-            CommandError::WrongCrc => "A packet with a wrong checksum has been sent or received",
-            CommandError::WrongSlot => "The given OTP slot does not exist",
-            CommandError::SlotNotProgrammed => "The given OTP slot is not programmed",
-            CommandError::WrongPassword => "The given password is wrong",
+impl CommandError {
+    fn as_str(&self) -> borrow::Cow<'static, str> {
+        match *self {
+            CommandError::WrongCrc => {
+                "A packet with a wrong checksum has been sent or received".into()
+            }
+            CommandError::WrongSlot => "The given OTP slot does not exist".into(),
+            CommandError::SlotNotProgrammed => "The given OTP slot is not programmed".into(),
+            CommandError::WrongPassword => "The given password is wrong".into(),
             CommandError::NotAuthorized => {
-                "You are not authorized for this command or provided a wrong temporary password"
+                "You are not authorized for this command or provided a wrong temporary \
+                 password"
+                    .into()
             }
-            CommandError::Timestamp => "An error occurred when getting or setting the time",
-            CommandError::NoName => "You did not provide a name for the OTP slot",
-            CommandError::NotSupported => "This command is not supported by this device",
-            CommandError::UnknownCommand => "This command is unknown",
-            CommandError::AesDecryptionFailed => "AES decryption failed",
-            CommandError::Unknown => "An unknown error occurred",
-            CommandError::InvalidString => "You passed a string containing a null byte",
-            CommandError::InvalidSlot => "The given slot is invalid",
-        };
-        write!(f, "{}", msg)
+            CommandError::Timestamp => "An error occurred when getting or setting the time".into(),
+            CommandError::NoName => "You did not provide a name for the OTP slot".into(),
+            CommandError::NotSupported => "This command is not supported by this device".into(),
+            CommandError::UnknownCommand => "This command is unknown".into(),
+            CommandError::AesDecryptionFailed => "AES decryption failed".into(),
+            CommandError::Unknown(x) => {
+                borrow::Cow::from(format!("An unknown error occurred ({})", x))
+            }
+            CommandError::Undefined => "An unspecified error occurred".into(),
+            CommandError::InvalidString => "You passed a string containing a null byte".into(),
+            CommandError::InvalidSlot => "The given slot is invalid".into(),
+        }
+    }
+}
+
+impl fmt::Display for CommandError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.as_str())
     }
 }
 
@@ -144,7 +159,7 @@ impl From<c_int> for CommandError {
             9 => CommandError::UnknownCommand,
             10 => CommandError::AesDecryptionFailed,
             201 => CommandError::InvalidSlot,
-            _ => CommandError::Unknown,
+            x => CommandError::Unknown(x.into()),
         }
     }
 }
diff --git a/tests/pws.rs b/tests/pws.rs
index 875324b..5061298 100644
--- a/tests/pws.rs
+++ b/tests/pws.rs
@@ -11,7 +11,7 @@ use crate::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
 fn get_slot_name_direct(slot: u8) -> Result<String, CommandError> {
     let ptr = unsafe { nitrokey_sys::NK_get_password_safe_slot_name(slot) };
     if ptr.is_null() {
-        return Err(CommandError::Unknown);
+        return Err(CommandError::Undefined);
     }
     let s = unsafe { CStr::from_ptr(ptr).to_string_lossy().into_owned() };
     unsafe { free(ptr as *mut c_void) };
@@ -19,7 +19,7 @@ fn get_slot_name_direct(slot: u8) -> Result<String, CommandError> {
         true => {
             let error = unsafe { nitrokey_sys::NK_get_last_command_status() } as c_int;
             match error {
-                0 => Err(CommandError::Unknown),
+                0 => Err(CommandError::Undefined),
                 other => Err(CommandError::from(other)),
             }
         }
@@ -97,9 +97,9 @@ fn get_data() {
 
     assert!(pws.erase_slot(1).is_ok());
     // TODO: check error codes
-    assert_eq!(Err(CommandError::Unknown), pws.get_slot_name(1));
-    assert_eq!(Err(CommandError::Unknown), pws.get_slot_login(1));
-    assert_eq!(Err(CommandError::Unknown), pws.get_slot_password(1));
+    assert_eq!(Err(CommandError::Undefined), pws.get_slot_name(1));
+    assert_eq!(Err(CommandError::Undefined), pws.get_slot_login(1));
+    assert_eq!(Err(CommandError::Undefined), pws.get_slot_password(1));
 
     let name = "with å";
     let login = "pär@test.com";
@@ -135,19 +135,19 @@ fn write() {
     );
 
     assert!(pws.write_slot(0, "", "login", "password").is_ok());
-    assert_eq!(Err(CommandError::Unknown), pws.get_slot_name(0));
+    assert_eq!(Err(CommandError::Undefined), pws.get_slot_name(0));
     assert_eq!(Ok(String::from("login")), pws.get_slot_login(0));
     assert_eq!(Ok(String::from("password")), pws.get_slot_password(0));
 
     assert!(pws.write_slot(0, "name", "", "password").is_ok());
     assert_eq!(Ok(String::from("name")), pws.get_slot_name(0));
-    assert_eq!(Err(CommandError::Unknown), pws.get_slot_login(0));
+    assert_eq!(Err(CommandError::Undefined), pws.get_slot_login(0));
     assert_eq!(Ok(String::from("password")), pws.get_slot_password(0));
 
     assert!(pws.write_slot(0, "name", "login", "").is_ok());
     assert_eq!(Ok(String::from("name")), pws.get_slot_name(0));
     assert_eq!(Ok(String::from("login")), pws.get_slot_login(0));
-    assert_eq!(Err(CommandError::Unknown), pws.get_slot_password(0));
+    assert_eq!(Err(CommandError::Undefined), pws.get_slot_password(0));
 }
 
 #[test]
@@ -160,5 +160,5 @@ fn erase() {
     assert!(pws.write_slot(0, "name", "login", "password").is_ok());
     assert!(pws.erase_slot(0).is_ok());
     assert!(pws.erase_slot(0).is_ok());
-    assert_eq!(Err(CommandError::Unknown), pws.get_slot_name(0));
+    assert_eq!(Err(CommandError::Undefined), pws.get_slot_name(0));
 }