From 7f3cc787d03423aa982ade0fa054bb79be18f6ae Mon Sep 17 00:00:00 2001
From: Robin Krahl <robin.krahl@ireas.org>
Date: Mon, 18 Feb 2019 14:23:10 +0000
Subject: Implement Nitrokey command handling

This patch changes the Get_Report handler in Nitrokey to extract the
command data from the buffer sent with the Set_Report request, to
execute a command based on this data and to write appropriate return
data back to the device.
---
 src/device.rs | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 76 insertions(+), 2 deletions(-)

diff --git a/src/device.rs b/src/device.rs
index f7c4fc7..3b6cf46 100644
--- a/src/device.rs
+++ b/src/device.rs
@@ -5,6 +5,7 @@ use usb_device::bus::{UsbBus, UsbBusAllocator};
 use usb_device::device::{UsbDevice, UsbDeviceBuilder, UsbVidPid};
 
 use crate::hid::{HidDevice, Protocol, ReportType, Subclass};
+use crate::util::TryFrom;
 
 const VID_CLAY_LOGIC: u16 = 0x20a0;
 const PID_NITROKEY_PRO: u16 = 0x4108;
@@ -18,6 +19,40 @@ const REPORT_DESCRIPTOR: &[u8] = &[
     0x75, 0x08, 0x95, 0x40, 0xB1, 0x02, 0xC0,
 ];
 
+enum_u8! {
+    #[derive(Clone, Copy, Debug, PartialEq)]
+    pub enum DeviceStatus {
+        Ok = 0,
+        Busy = 1,
+        Error = 2,
+        ReceivedReport = 3,
+    }
+}
+
+enum_u8! {
+    #[derive(Clone, Copy, Debug, PartialEq)]
+    pub enum CommandStatus {
+        Ok = 0,
+        WrongCrc = 1,
+        WrongSlot = 2,
+        SlotNotProgrammed = 3,
+        WrongPassword = 4,
+        NotAuthorized = 5,
+        TimestampWarning = 6,
+        NoNameError = 7,
+        NotSupported = 8,
+        UnknownCommand = 9,
+        AesDecryptionFailed = 10,
+    }
+}
+
+enum_u8! {
+    #[derive(Clone, Copy, Debug, PartialEq)]
+    pub enum CommandId {
+        GetStatus = 0,
+    }
+}
+
 pub struct Nitrokey {
     buf: [u8; REPORT_LEN],
 }
@@ -28,6 +63,15 @@ impl Nitrokey {
             buf: [0; REPORT_LEN],
         }
     }
+
+    fn execute_command(
+        &self,
+        command_id: CommandId,
+        data: &[u8],
+    ) -> Result<[u8; 53], CommandStatus> {
+        let _ = (command_id, data);
+        Err(CommandStatus::UnknownCommand)
+    }
 }
 
 impl HidDevice for Nitrokey {
@@ -44,8 +88,38 @@ impl HidDevice for Nitrokey {
     }
 
     fn get_report(&mut self, report_type: ReportType, report_id: u8) -> Result<&[u8], ()> {
-        let _ = (report_type, report_id);
-        Err(())
+        if report_type != ReportType::Feature || report_id != 0 {
+            return Err(());
+        }
+
+        let device_status = DeviceStatus::Ok;
+        let command_id = self.buf[0];
+        let result = if let Ok(command_id) = CommandId::try_from(command_id) {
+            self.execute_command(command_id, &self.buf[1..60])
+        } else {
+            Err(CommandStatus::UnknownCommand)
+        };
+        let (command_status, command_data) = result
+            .map(|d| (CommandStatus::Ok, d))
+            .unwrap_or_else(|status| (status, [0; 53]));
+
+        let pre_data: [u8; 7] = [
+            device_status.into(), // device status
+            command_id,           // command_id
+            self.buf[60],
+            self.buf[61],
+            self.buf[62],
+            self.buf[63],          // last_command_crc
+            command_status.into(), // last_command_status
+        ];
+        let post_data: [u8; 4] = [
+            0x00, 0x00, 0x00, 0x01, // crc -- libnitrokey accepts any non-zero value
+        ];
+
+        self.buf[0..7].copy_from_slice(&pre_data);
+        self.buf[7..7 + command_data.len()].copy_from_slice(&command_data);
+        self.buf[60..64].copy_from_slice(&post_data);
+        Ok(&self.buf)
     }
 
     fn set_report(
-- 
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