Rewrite translated code to use the pcsc crate

This commit contains a "big bang" refactor/rewrite which does the
following:

- Replaces all `SCard*` FFI calls with the `pcsc` crate, which provides
  a safe, portable PC/SC API across Windows, macOS, and Linux
- Refactors the `util` module into modules representing the various
  device functions and concepts, e.g. `certificate`, `key`, `mgm`
- Replaces all usage of `libc` with `std` functionality, and in many
  places rewriting functionality to use safe code.
- Removes `ykpiv_` from all function names, and `Piv*` from type names.

In 20/20 hindsight I wish I had done this commit more incrementally so
as to make it easier to review. Que sera sera.

However, realistically we need to test all functionality on the device
to ensure that it actually works. Going forward I would like to put
pretty much all of the current code behind an `untested` cargo feature,
and then remove it for each bit of functionality we test.

src/response.rs

@@ -0,0 +1,183 @@
+//! Responses to issued commands
+
+// Adapted from yubico-piv-tool:
+// <https://github.com/Yubico/yubico-piv-tool/>
+//
+// Copyright (c) 2014-2016 Yubico AB
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//   * Redistributions of source code must retain the above copyright
+//     notice, this list of conditions and the following disclaimer.
+//
+//   * Redistributions in binary form must reproduce the above
+//     copyright notice, this list of conditions and the following
+//     disclaimer in the documentation and/or other materials provided
+//     with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+use crate::Buffer;
+
+/// Parsed response to a command
+pub(crate) struct Response {
+    /// Status words
+    status_words: StatusWords,
+
+    /// Buffer
+    buffer: Buffer,
+}
+
+impl Response {
+    /// Parse a response from the given buffer
+    pub fn from_bytes(mut buffer: Buffer) -> Self {
+        if buffer.len() >= 2 {
+            let sw = StatusWords::from(
+                (buffer[buffer.len() - 2] as u32) << 8 | (buffer[buffer.len() - 1] as u32),
+            );
+
+            let len = buffer.len() - 2;
+            buffer.truncate(len);
+            Response {
+                status_words: sw,
+                buffer,
+            }
+        } else {
+            Response {
+                status_words: StatusWords::None,
+                buffer,
+            }
+        }
+    }
+
+    /// Create a new response from the given status words and buffer
+    pub fn new(status_words: StatusWords, buffer: Buffer) -> Response {
+        Response {
+            status_words,
+            buffer,
+        }
+    }
+
+    /// Get the [`StatusWords`] for this response.
+    pub fn status_words(&self) -> StatusWords {
+        self.status_words
+    }
+
+    /// Get the raw [`StatusWords`] code for this response.
+    pub fn code(&self) -> u32 {
+        self.status_words.code()
+    }
+
+    /// Do the status words for this response indicate success?
+    pub fn is_success(&self) -> bool {
+        self.status_words.is_success()
+    }
+
+    /// Borrow the response buffer
+    pub fn buffer(&self) -> &[u8] {
+        self.buffer.as_ref()
+    }
+
+    /// Consume this response, returning its buffer
+    pub fn into_buffer(self) -> Buffer {
+        self.buffer
+    }
+}
+
+impl AsRef<[u8]> for Response {
+    fn as_ref(&self) -> &[u8] {
+        self.buffer()
+    }
+}
+
+/// Status Words (SW) are 2-byte values returned by a card command.
+///
+/// The first byte of a status word is referred to as SW1 and the second byte
+/// of a status word is referred to as SW2.
+///
+/// See NIST special publication 800-73-4, section 5.6:
+/// <https://csrc.nist.gov/publications/detail/sp/800-73/4/final>
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub(crate) enum StatusWords {
+    /// No status words present in response
+    None,
+
+    /// Successful execution
+    Success,
+
+    /// Security status not satisfied
+    SecurityStatusError,
+
+    /// Authentication method blocked
+    AuthBlockedError,
+
+    /// Incorrect parameter in command data field
+    IncorrectParamError,
+
+    //
+    // Custom Yubico Status Word extensions
+    //
+    /// Incorrect card slot error
+    IncorrectSlotError,
+
+    /// Not supported error
+    NotSupportedError,
+
+    /// Other/unrecognized status words
+    Other(u32),
+}
+
+impl StatusWords {
+    /// Get the numerical response code for these status words
+    pub fn code(self) -> u32 {
+        match self {
+            StatusWords::None => 0,
+            StatusWords::SecurityStatusError => 0x6982,
+            StatusWords::AuthBlockedError => 0x6983,
+            StatusWords::IncorrectParamError => 0x6a80,
+            StatusWords::IncorrectSlotError => 0x6b00,
+            StatusWords::NotSupportedError => 0x6d00,
+            StatusWords::Success => 0x9000,
+            StatusWords::Other(n) => n,
+        }
+    }
+
+    /// Do these status words indicate success?
+    pub fn is_success(self) -> bool {
+        self == StatusWords::Success
+    }
+}
+
+impl From<u32> for StatusWords {
+    fn from(sw: u32) -> Self {
+        match sw {
+            0x0000 => StatusWords::None,
+            0x6982 => StatusWords::SecurityStatusError,
+            0x6983 => StatusWords::AuthBlockedError,
+            0x6a80 => StatusWords::IncorrectParamError,
+            0x6b00 => StatusWords::IncorrectSlotError,
+            0x6d00 => StatusWords::NotSupportedError,
+            0x9000 => StatusWords::Success,
+            _ => StatusWords::Other(sw),
+        }
+    }
+}
+
+impl From<StatusWords> for u32 {
+    fn from(sw: StatusWords) -> u32 {
+        sw.code()
+    }
+}