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/msroots.rs

@@ -0,0 +1,176 @@
+//! `msroots`: PKCS#7 formatted certificate store for enterprise trusted roots.
+//!
+//! This `msroots` file contains a bag of certificates with empty content and
+//! an empty signature, allowing an enterprise root certificate truststore to
+//! be written to and read from a YubiKey.
+//!
+//! For more information, see:
+//! <https://docs.microsoft.com/en-us/windows-hardware/drivers/smartcard/developer-guidelines#-interoperability-with-msroots>
+
+// 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::{consts::*, error::Error, serialization::*, yubikey::YubiKey};
+use log::error;
+use std::{ptr, slice};
+
+/// `msroots` file: PKCS#7-formatted certificate store for enterprise trust roots
+pub struct MsRoots(Vec<u8>);
+
+impl MsRoots {
+    /// Initialize a local certificate struct from the given bytebuffer
+    pub fn new(msroots: impl AsRef<[u8]>) -> Result<Self, Error> {
+        Ok(MsRoots(msroots.as_ref().into()))
+    }
+
+    /// Read `msroots` file from YubiKey
+    pub fn read(yubikey: &mut YubiKey) -> Result<Vec<Self>, Error> {
+        let mut len: usize = 0;
+        let mut ptr: *mut u8;
+        let mut tag: u8;
+        let mut offset: usize = 0;
+
+        let mut results = vec![];
+        let cb_data = yubikey.obj_size_max();
+        let txn = yubikey.begin_transaction()?;
+
+        // allocate first page
+        let mut p_data = vec![0u8; cb_data];
+
+        for object_id in YKPIV_OBJ_MSROOTS1..YKPIV_OBJ_MSROOTS5 {
+            let mut buf = txn.fetch_object(object_id)?;
+            let cb_buf = buf.len();
+
+            ptr = buf.as_mut_ptr();
+
+            if cb_buf < CB_OBJ_TAG_MIN {
+                return Ok(results);
+            }
+
+            unsafe {
+                tag = *ptr;
+                ptr = ptr.add(1);
+            }
+
+            if tag != TAG_MSROOTS_MID && (tag != TAG_MSROOTS_END || object_id == YKPIV_OBJ_MSROOTS5)
+            {
+                // the current object doesn't contain a valid part of a msroots file
+
+                // treat condition as object isn't found
+                return Ok(results);
+            }
+
+            unsafe {
+                ptr = ptr.add(get_length(
+                    slice::from_raw_parts(ptr, buf.as_ptr() as usize + buf.len() - ptr as usize),
+                    &mut len,
+                ));
+            }
+
+            // check that decoded length represents object contents
+            if len > cb_buf - (ptr as isize - buf.as_mut_ptr() as isize) as usize {
+                return Ok(results);
+            }
+
+            unsafe {
+                ptr::copy(ptr, p_data.as_mut_ptr().add(offset), len);
+            }
+
+            offset += len;
+
+            match MsRoots::new(&p_data[..offset]) {
+                Ok(msroots) => results.push(msroots),
+                Err(res) => error!("error parsing msroots: {:?}", res),
+            }
+
+            if tag == TAG_MSROOTS_END {
+                break;
+            }
+        }
+
+        Ok(results)
+    }
+
+    /// Write `msroots` file to YubiKey
+    pub fn write(&self, yubikey: &mut YubiKey) -> Result<(), Error> {
+        let mut buf = [0u8; CB_OBJ_MAX];
+        let mut offset: usize;
+        let mut data_offset: usize = 0;
+        let mut data_chunk: usize;
+        let data = &self.0;
+        let data_len = data.len();
+        let n_objs: usize;
+        let cb_obj_max = yubikey.obj_size_max();
+        let txn = yubikey.begin_transaction()?;
+
+        if data_len == 0 {
+            return txn.save_object(YKPIV_OBJ_MSROOTS1, &[]);
+        }
+
+        n_objs = (data_len / (cb_obj_max - 4)) + 1;
+
+        if n_objs > 5 {
+            return Err(Error::SizeError);
+        }
+
+        for i in 0..n_objs {
+            offset = 0;
+
+            data_chunk = if cb_obj_max - 4 < data_len - data_offset {
+                cb_obj_max - 4
+            } else {
+                data_len - data_offset
+            };
+
+            buf[offset] = if i == n_objs - 1 {
+                TAG_MSROOTS_END
+            } else {
+                TAG_MSROOTS_MID
+            };
+
+            offset += 1;
+            offset += set_length(&mut buf[offset..], data_chunk);
+            buf[offset..].copy_from_slice(&data[data_offset..(data_offset + data_chunk)]);
+            offset += data_chunk;
+
+            txn.save_object(YKPIV_OBJ_MSROOTS1 + i as u32, &buf[..offset])?;
+
+            data_offset += data_chunk;
+        }
+
+        Ok(())
+    }
+}
+
+impl AsRef<[u8]> for MsRoots {
+    fn as_ref(&self) -> &[u8] {
+        self.0.as_ref()
+    }
+}