Hostenv file storage

libraries/persistent_store/Cargo.toml

@@ -7,5 +7,8 @@ edition = "2018"
 
 [dependencies]
 
+[dev-dependencies]
+tempfile = "3"
+
 [features]
 std = []

libraries/persistent_store/src/file.rs

@@ -0,0 +1,189 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! File-backed persistent flash storage for virtual authenticator.
+//!
+//! [`FileStorage`] implements the flash [`Storage`] interface but doesn't interface with an
+//! actual flash storage. Instead it uses a host-based file to persist the storage state.
+
+use crate::{Storage, StorageIndex, StorageResult};
+use alloc::borrow::Cow;
+use core::cell::RefCell;
+use std::fs::{File, OpenOptions};
+use std::io::{Read, Seek, SeekFrom, Write};
+use std::path::Path;
+
+/// Simulates a flash storage using a host-based file.
+///
+/// This is usable for emulating authenticator hardware on VM hypervisor's host OS.
+pub struct FileStorage {
+    // Options of the storage.
+    options: FileOptions,
+
+    /// File for persisting contents of the storage.
+    ///
+    /// Reading data from File requires mutable reference, as seeking and reading data
+    /// changes file's current position.
+    ///
+    /// All operations on backing file internally always first seek to needed position,
+    /// so it's safe to borrow mutable reference to backing file for the time of operation.
+    file: RefCell<File>,
+}
+
+/// Options for file-backed storage.
+pub struct FileOptions {
+    /// Size of a word in bytes.
+    pub word_size: usize,
+
+    /// Size of a page in bytes.
+    pub page_size: usize,
+
+    /// Number of pages in storage.
+    pub num_pages: usize,
+}
+
+impl FileStorage {
+    pub fn new(path: &Path, options: FileOptions) -> StorageResult<FileStorage> {
+        let mut file_ref = RefCell::new(
+            OpenOptions::new()
+                .read(true)
+                .write(true)
+                .create(true)
+                .open(path)?,
+        );
+        let file = file_ref.get_mut();
+        let file_len = file.metadata()?.len();
+        let store_len: u64 = (options.page_size * options.num_pages) as u64;
+
+        if file_len == 0 {
+            file.seek(SeekFrom::Start(0))?;
+            let buf = vec![0xffu8; options.page_size];
+            for _ in 0..options.num_pages {
+                file.write(&buf)?;
+            }
+        } else if file_len != store_len {
+            // FileStorage buffer should be of fixed size, opening previously saved file
+            // from storage of different size is not supported
+            panic!("Invalid file size {}, should be {}", file_len, store_len);
+        }
+        Ok(FileStorage {
+            options,
+            file: file_ref,
+        })
+    }
+}
+
+impl Storage for FileStorage {
+    fn word_size(&self) -> usize {
+        self.options.word_size
+    }
+
+    fn page_size(&self) -> usize {
+        self.options.page_size
+    }
+
+    fn num_pages(&self) -> usize {
+        self.options.num_pages
+    }
+
+    fn max_word_writes(&self) -> usize {
+        usize::MAX
+    }
+
+    fn max_page_erases(&self) -> usize {
+        usize::MAX
+    }
+
+    fn read_slice(&self, index: StorageIndex, length: usize) -> StorageResult<Cow<[u8]>> {
+        let mut file = self.file.borrow_mut();
+        file.seek(SeekFrom::Start(index.range(length, self)?.start as u64))?;
+        let mut buf = vec![0u8; length];
+        file.read_exact(&mut buf)?;
+        Ok(Cow::Owned(buf))
+    }
+
+    fn write_slice(&mut self, index: StorageIndex, value: &[u8]) -> StorageResult<()> {
+        let mut file = self.file.borrow_mut();
+        file.seek(SeekFrom::Start(
+            index.range(value.len(), self)?.start as u64,
+        ))?;
+        file.write_all(value)?;
+        Ok(())
+    }
+
+    fn erase_page(&mut self, page: usize) -> StorageResult<()> {
+        let mut file = self.file.borrow_mut();
+        let index = StorageIndex { page, byte: 0 };
+        file.seek(SeekFrom::Start(
+            index.range(self.page_size(), self)?.start as u64,
+        ))?;
+        file.write_all(&vec![0xffu8; self.page_size()][..])?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::path::PathBuf;
+    use tempfile::TempDir;
+
+    const BLANK_WORD: &[u8] = &[0xff, 0xff, 0xff, 0xff];
+    const DATA_WORD: &[u8] = &[0xee, 0xdd, 0xbb, 0x77];
+
+    const FILE_NAME: &str = "opensk_storage.bin";
+
+    const OPTIONS: FileOptions = FileOptions {
+        word_size: 4,
+        page_size: 0x1000,
+        num_pages: 20,
+    };
+
+    fn make_tmp_dir() -> PathBuf {
+        let tmp_dir = TempDir::new().unwrap();
+        tmp_dir.into_path()
+    }
+
+    fn remove_tmp_dir(tmp_dir: PathBuf) {
+        std::fs::remove_dir_all(tmp_dir).unwrap();
+    }
+
+    fn temp_storage(tmp_dir: &PathBuf) -> FileStorage {
+        let mut tmp_file = tmp_dir.clone();
+        tmp_file.push(FILE_NAME);
+        FileStorage::new(&tmp_file, OPTIONS).unwrap()
+    }
+
+    #[test]
+    fn read_write_persist_ok() {
+        let index = StorageIndex { page: 0, byte: 0 };
+        let next_index = StorageIndex { page: 0, byte: 4 };
+
+        let tmp_dir = make_tmp_dir();
+        {
+            let mut file_storage = temp_storage(&tmp_dir);
+            assert_eq!(file_storage.read_slice(index, 4).unwrap(), BLANK_WORD);
+            file_storage.write_slice(index, DATA_WORD).unwrap();
+            assert_eq!(file_storage.read_slice(index, 4).unwrap(), DATA_WORD);
+            assert_eq!(file_storage.read_slice(next_index, 4).unwrap(), BLANK_WORD);
+        }
+        // Reload and check the data from previously persisted storage
+        {
+            let file_storage = temp_storage(&tmp_dir);
+            assert_eq!(file_storage.read_slice(index, 4).unwrap(), DATA_WORD);
+            assert_eq!(file_storage.read_slice(next_index, 4).unwrap(), BLANK_WORD);
+        }
+        remove_tmp_dir(tmp_dir);
+    }
+}

libraries/persistent_store/src/lib.rs

@@ -365,6 +365,8 @@ extern crate alloc;
 mod buffer;
 #[cfg(feature = "std")]
 mod driver;
+#[cfg(feature = "std")]
+mod file;
 mod format;
 pub mod fragment;
 #[cfg(feature = "std")]
@@ -381,6 +383,8 @@ pub use self::driver::{
     StoreDriver, StoreDriverOff, StoreDriverOn, StoreInterruption, StoreInvariant,
 };
 #[cfg(feature = "std")]
+pub use self::file::{FileOptions, FileStorage};
+#[cfg(feature = "std")]
 pub use self::model::{StoreModel, StoreOperation};
 pub use self::storage::{Storage, StorageError, StorageIndex, StorageResult};
 pub use self::store::{

libraries/persistent_store/src/storage.rs

@@ -36,6 +36,13 @@ pub enum StorageError {
     CustomError,
 }
 
+#[cfg(feature = "std")]
+impl From<std::io::Error> for StorageError {
+    fn from(_: std::io::Error) -> Self {
+        Self::CustomError
+    }
+}
+
 pub type StorageResult<T> = Result<T, StorageError>;
 
 /// Abstracts a flash storage.