From a0c6480aa6b1c6dad45b67e5bc7c29c5f0a4bb0e Mon Sep 17 00:00:00 2001
From: Daniel Mueller <deso@posteo.net>
Date: Tue, 28 Mar 2017 20:06:42 -0700
Subject: Send HID feature report to open/close the encrypted volume

With this change we assemble a HID feature report and send it to the
nitrokey device. Feature reports are the objects used for sending
commands to the nitrokey. We create two different reports for
opening and closing of the encrypted volume.
---
 nitrocli/src/crc32.rs | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 nitrocli/src/crc32.rs

(limited to 'nitrocli/src/crc32.rs')

diff --git a/nitrocli/src/crc32.rs b/nitrocli/src/crc32.rs
new file mode 100644
index 0000000..8431db5
--- /dev/null
+++ b/nitrocli/src/crc32.rs
@@ -0,0 +1,88 @@
+// crc32.rs
+
+// *************************************************************************
+// * Copyright (C) 2017 Daniel Mueller (deso@posteo.net)                   *
+// *                                                                       *
+// * This program is free software: you can redistribute it and/or modify  *
+// * it under the terms of the GNU General Public License as published by  *
+// * the Free Software Foundation, either version 3 of the License, or     *
+// * (at your option) any later version.                                   *
+// *                                                                       *
+// * This program is distributed in the hope that it will be useful,       *
+// * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+// * GNU General Public License for more details.                          *
+// *                                                                       *
+// * You should have received a copy of the GNU General Public License     *
+// * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
+// *************************************************************************
+
+/// Polynomial used in STM32.
+const CRC32_POLYNOMIAL: u32 = 0x04c11db7;
+
+
+fn crc32(mut crc: u32, data: u32) -> u32 {
+  crc = crc ^ data;
+
+  for _ in 0..32 {
+    if crc & 0x80000000 != 0 {
+      crc = (crc << 1) ^ CRC32_POLYNOMIAL;
+    } else {
+      crc = crc << 1;
+    }
+  }
+  return crc;
+}
+
+
+/// Retrieve a u32 slice of the 'data' part.
+///
+/// Note that the size of the supplied data has to be a multiple of 4
+/// bytes.
+fn as_slice_u32(data: &[u8]) -> &[u32] {
+  assert!(data.len() % ::std::mem::size_of::<u32>() == 0);
+
+  unsafe {
+    let ptr = data.as_ptr() as *const u32;
+    let len = data.len() / ::std::mem::size_of::<u32>();
+    return ::std::slice::from_raw_parts(ptr, len);
+  }
+}
+
+
+/// Calculate the CRC of a byte slice.
+pub fn crc(data: &[u8]) -> u32 {
+  let mut crc = 0xffffffff;
+  let data = as_slice_u32(data);
+
+  for i in 0..data.len() {
+    crc = crc32(crc, data[i]);
+  }
+  return crc;
+}
+
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn test_crc32() {
+    let mut crc = 0;
+
+    // The expected values were computed with the original function.
+    crc = crc32(crc, 0xdeadbeef);
+    assert_eq!(crc, 0x46dec763);
+
+    crc = crc32(crc, 42);
+    assert_eq!(crc, 0x7e579b45);
+  }
+
+  #[test]
+  fn test_crc() {
+    let data = &"thisisatextthatistobecrced..".to_string().into_bytes();
+    let crc = crc(data);
+
+    assert_eq!(crc, 0x469db4ee);
+  }
+}
-- 
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