authfs/src/file.rs

mod attr;
mod dir;
mod remote_file;

pub use attr::Attr;
pub use dir::{InMemoryDir, RemoteDirEditor};
pub use remote_file::{RemoteFileEditor, RemoteFileReader, RemoteMerkleTreeReader};

use crate::common::{divide_roundup, CHUNK_SIZE};
use authfs_aidl_interface::aidl::com::android::virt::fs::IVirtFdService::IVirtFdService;
use binder::{Status, StatusCode, Strong};
use rpcbinder::RpcSession;
use std::convert::TryFrom;
use std::io;
use std::path::{Path, MAIN_SEPARATOR};

pub type VirtFdService = Strong<dyn IVirtFdService>;
pub type VirtFdServiceStatus = Status;

pub type ChunkBuffer = [u8; CHUNK_SIZE as usize];

pub const RPC_SERVICE_PORT: u32 = 3264;

pub fn get_rpc_binder_service(cid: u32) -> io::Result<VirtFdService> {
    RpcSession::new().setup_vsock_client(cid, RPC_SERVICE_PORT).map_err(|e| match e {
        StatusCode::BAD_VALUE => {
            io::Error::new(io::ErrorKind::InvalidInput, "Invalid raw AIBinder")
        }
        _ => io::Error::new(
            io::ErrorKind::AddrNotAvailable,
            format!("Cannot connect to RPC service: {}", e),
        ),
    })
}

/// A trait for reading data by chunks. Chunks can be read by specifying the chunk index. Only the
/// last chunk may have incomplete chunk size.
pub trait ReadByChunk {
    /// Reads the `chunk_index`-th chunk to a `ChunkBuffer`. Returns the size read, which has to be
    /// `CHUNK_SIZE` except for the last incomplete chunk. Reading beyond the file size (including
    /// empty file) should return 0.
    fn read_chunk(&self, chunk_index: u64, buf: &mut ChunkBuffer) -> io::Result<usize>;
}

/// A trait to write a buffer to the destination at a given offset. The implementation does not
/// necessarily own or maintain the destination state.
///
/// NB: The trait is required in a member of `fusefs::AuthFs`, which is required to be Sync and
/// immutable (this the member).
pub trait RandomWrite {
    /// Writes `buf` to the destination at `offset`. Returns the written size, which may not be the
    /// full buffer.
    fn write_at(&self, buf: &[u8], offset: u64) -> io::Result<usize>;

    /// Writes the full `buf` to the destination at `offset`.
    fn write_all_at(&self, buf: &[u8], offset: u64) -> io::Result<()> {
        let mut input_offset = 0;
        let mut output_offset = offset;
        while input_offset < buf.len() {
            let size = self.write_at(&buf[input_offset..], output_offset)?;
            input_offset += size;
            output_offset += size as u64;
        }
        Ok(())
    }

    /// Resizes the file to the new size.
    fn resize(&self, size: u64) -> io::Result<()>;
}

/// Checks whether the path is a simple file name without any directory separator.
pub fn validate_basename(path: &Path) -> io::Result<()> {
    if matches!(path.to_str(), Some(path_str) if !path_str.contains(MAIN_SEPARATOR)) {
        Ok(())
    } else {
        Err(io::Error::from_raw_os_error(libc::EINVAL))
    }
}

pub struct EagerChunkReader {
    buffer: Vec<u8>,
}

impl EagerChunkReader {
    pub fn new<F: ReadByChunk>(chunked_file: F, file_size: u64) -> io::Result<EagerChunkReader> {
        let last_index = divide_roundup(file_size, CHUNK_SIZE);
        let file_size = usize::try_from(file_size).unwrap();
        let mut buffer = Vec::with_capacity(file_size);
        let mut chunk_buffer = [0; CHUNK_SIZE as usize];
        for index in 0..last_index {
            let size = chunked_file.read_chunk(index, &mut chunk_buffer)?;
            buffer.extend_from_slice(&chunk_buffer[..size]);
        }
        if buffer.len() < file_size {
            Err(io::Error::new(
                io::ErrorKind::InvalidData,
                format!("Insufficient data size ({} < {})", buffer.len(), file_size),
            ))
        } else {
            Ok(EagerChunkReader { buffer })
        }
    }
}

impl ReadByChunk for EagerChunkReader {
    fn read_chunk(&self, chunk_index: u64, buf: &mut ChunkBuffer) -> io::Result<usize> {
        if let Some(chunk) = &self.buffer.chunks(CHUNK_SIZE as usize).nth(chunk_index as usize) {
            buf[..chunk.len()].copy_from_slice(chunk);
            Ok(chunk.len())
        } else {
            Ok(0) // Read beyond EOF is normal
        }
    }
}