Add the fill_sd_card function to Storage

This patch adds support for libnitrokey’s
NK_fill_SD_card_with_random_data function.  It is executed by the
fill_sd_card function of the Storage struct.  We also add a new test
case that is set to ignore because it takes between 30 and 60 minutes to
run.

5 files changed, 95 insertions, 4 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 419a942..06836d9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ SPDX-License-Identifier: CC0-1.0
 - Add the `get_sd_card_usage` function to the `Storage` struct.
 - Add the `OperationStatus` enum and the `get_operation_status` function for
   the `Storage` struct.
+- Add the `fill_sd_card` function to the `Storage` struct.
 
 # v0.4.0 (2020-01-02)
 - Remove the `test-pro` and `test-storage` features.
diff --git a/README.md b/README.md
index d62e38e..5f775ef 100644
--- a/README.md
+++ b/README.md
@@ -64,6 +64,10 @@ an AES key has been built.  Some tests will overwrite the data stored on the
 Nitrokey device or perform a factory reset.  Never execute the tests if you
 don’t want to destroy all data on any connected Nitrokey device!
 
+The test suite contains some test that take very long to execute, for example
+filling the SD card of a Nitrokey Storage with random data.  These tests are
+ignored per default.  Use `cargo test -- --ignored` to execute the tests.
+
 ## Acknowledgments
 
 Thanks to Nitrokey UG for providing two Nitrokey devices to support the
diff --git a/TODO.md b/TODO.md
index 8f9b898..ef2f6d4 100644
--- a/TODO.md
+++ b/TODO.md
@@ -3,8 +3,6 @@ Copyright (C) 2019 Robin Krahl <robin.krahl@ireas.org>
 SPDX-License-Identifier: CC0-1.0
 -->
 
-- Add support for the currently unsupported commands:
-    - `NK_fill_SD_card_with_random_data`
 - Clear passwords from memory.
 - Lock password safe in `PasswordSafe::drop()` (see [nitrokey-storage-firmware
   issue 65][]).
diff --git a/src/device/storage.rs b/src/device/storage.rs
index 8d45763..deb2844 100644
--- a/src/device/storage.rs
+++ b/src/device/storage.rs
@@ -8,7 +8,7 @@ use std::ops;
 use nitrokey_sys;
 
 use crate::device::{Device, FirmwareVersion, Model, Status};
-use crate::error::Error;
+use crate::error::{CommandError, Error};
 use crate::otp::GenerateOtp;
 use crate::util::{get_command_result, get_cstring, get_last_error};
 
@@ -700,7 +700,9 @@ impl<'a> Storage<'a> {
     /// Some commands may start a background operation during which no other commands can be
     /// executed.  This method can be used to check whether such an operation is ongoing.
     ///
-    /// Currently, this is only used by the `fill_sd_card` method.
+    /// Currently, this is only used by the [`fill_sd_card`][] method.
+    ///
+    /// [`fill_sd_card`]: #method.fill_sd_card
     pub fn get_operation_status(&self) -> Result<OperationStatus, Error> {
         let status = unsafe { nitrokey_sys::NK_get_progress_bar_value() };
         match status {
@@ -713,6 +715,53 @@ impl<'a> Storage<'a> {
         }
     }
 
+    /// Overwrites the SD card with random data.
+    ///
+    /// Ths method starts a background operation that overwrites the SD card with random data.
+    /// While this operation is ongoing, no other commands can be executed.  Use the
+    /// [`get_operation_status`][] function to check the progress of the operation.
+    ///
+    /// # Errors
+    ///
+    /// - [`InvalidString`][] if one of the provided passwords contains a null byte
+    /// - [`WrongPassword`][] if the admin password is wrong
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::OperationStatus;
+    ///
+    /// let mut manager = nitrokey::take()?;
+    /// let mut storage = manager.connect_storage()?;
+    /// storage.fill_sd_card("12345678")?;
+    /// loop {
+    ///     match storage.get_operation_status()? {
+    ///         OperationStatus::Ongoing(progress) => println!("{}/100", progress),
+    ///         OperationStatus::Idle => {
+    ///             println!("Done!");
+    ///             break;
+    ///         }
+    ///     }
+    /// }
+    /// # Ok::<(), nitrokey::Error>(())
+    /// ```
+    ///
+    /// [`get_operation_status`]: #method.get_operation_status
+    /// [`InvalidString`]: enum.LibraryError.html#variant.InvalidString
+    /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
+    pub fn fill_sd_card(&mut self, admin_pin: &str) -> Result<(), Error> {
+        let admin_pin_string = get_cstring(admin_pin)?;
+        get_command_result(unsafe {
+            nitrokey_sys::NK_fill_SD_card_with_random_data(admin_pin_string.as_ptr())
+        })
+        .or_else(|err| match err {
+            // libnitrokey’s C API returns a LongOperationInProgressException with the same error
+            // code as the WrongCrc command error, so we cannot distinguish them.
+            Error::CommandError(CommandError::WrongCrc) => Ok(()),
+            err => Err(err),
+        })
+    }
+
     /// Exports the firmware to the unencrypted volume.
     ///
     /// This command requires the admin PIN.  The unencrypted volume must be in read-write mode
diff --git a/tests/device.rs b/tests/device.rs
index 7296372..a88c956 100644
--- a/tests/device.rs
+++ b/tests/device.rs
@@ -653,6 +653,45 @@ fn get_operation_status(device: Storage) {
 }
 
 #[test_device]
+#[ignore]
+fn fill_sd_card(device: Storage) {
+    // This test takes up to 60 min to execute and is therefore ignored by default.  Use `cargo
+    // test -- --ignored fill_sd_card` to run the test.
+
+    let mut device = device;
+    assert_ok!((), device.factory_reset(DEFAULT_ADMIN_PIN));
+    thread::sleep(time::Duration::from_secs(3));
+    assert_ok!((), device.build_aes_key(DEFAULT_ADMIN_PIN));
+
+    let status = unwrap_ok!(device.get_storage_status());
+    assert!(!status.filled_with_random);
+
+    assert_ok!((), device.fill_sd_card(DEFAULT_ADMIN_PIN));
+    assert_cmd_err!(CommandError::WrongCrc, device.get_status());
+
+    let mut status = OperationStatus::Ongoing(0);
+    let mut last_progress = 0u8;
+    while status != OperationStatus::Idle {
+        status = unwrap_ok!(device.get_operation_status());
+        if let OperationStatus::Ongoing(progress) = status {
+            assert!(progress <= 100, "progress = {}", progress);
+            assert!(
+                progress >= last_progress,
+                "progress = {}, last_progress = {}",
+                progress,
+                last_progress
+            );
+            last_progress = progress;
+
+            thread::sleep(time::Duration::from_secs(10));
+        }
+    }
+
+    let status = unwrap_ok!(device.get_storage_status());
+    assert!(status.filled_with_random);
+}
+
+#[test_device]
 fn export_firmware(device: Storage) {
     let mut device = device;
     assert_cmd_err!(