Decouple apkdmverity from device mapper modules
We need to extend & reuse device mapper modules to construct other
targets such as crypt. This patch moves dm related modules to a separate
lib & change apkdmverity binary to use that library.
Other changes include making delete_device_deferred removing test
annotation from delete_device_deferred & changing visibility of
functions.
Test: atest apkdmverity.test
Bug: 250880499
Change-Id: I5894c362e2b85c6260931b4c9d90f7e3d602291c
diff --git a/libs/devicemapper/src/lib.rs b/libs/devicemapper/src/lib.rs
new file mode 100644
index 0000000..1bcaf1a
--- /dev/null
+++ b/libs/devicemapper/src/lib.rs
@@ -0,0 +1,208 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * 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.
+ */
+
+// `dm` module implements part of the `device-mapper` ioctl interfaces. It currently supports
+// creation and deletion of the mapper device. It doesn't support other operations like querying
+// the status of the mapper device. And there's no plan to extend the support unless it is
+// required.
+//
+// Why in-house development? [`devicemapper`](https://crates.io/crates/devicemapper) is a public
+// Rust implementation of the device mapper APIs. However, it doesn't provide any abstraction for
+// the target-specific tables. User has to manually craft the table. Ironically, the library
+// provides a lot of APIs for the features that are not required for `apkdmverity` such as listing
+// the device mapper block devices that are currently listed in the kernel. Size is an important
+// criteria for Microdroid.
+
+//! A library to create device mapper spec & issue ioctls.
+
+#![allow(missing_docs)]
+
+use anyhow::{Context, Result};
+use data_model::DataInit;
+use std::fs::{File, OpenOptions};
+use std::io::Write;
+use std::mem::size_of;
+use std::os::unix::io::AsRawFd;
+use std::path::{Path, PathBuf};
+
+/// Expose util functions
+pub mod util;
+/// Exposes the DmVerityTarget & related builder
+pub mod verity;
+
+mod sys;
+use sys::*;
+use util::*;
+use verity::*;
+
+nix::ioctl_readwrite!(_dm_dev_create, DM_IOCTL, Cmd::DM_DEV_CREATE, DmIoctl);
+nix::ioctl_readwrite!(_dm_dev_suspend, DM_IOCTL, Cmd::DM_DEV_SUSPEND, DmIoctl);
+nix::ioctl_readwrite!(_dm_table_load, DM_IOCTL, Cmd::DM_TABLE_LOAD, DmIoctl);
+nix::ioctl_readwrite!(_dm_dev_remove, DM_IOCTL, Cmd::DM_DEV_REMOVE, DmIoctl);
+
+/// Create a new (mapper) device
+fn dm_dev_create(dm: &DeviceMapper, ioctl: *mut DmIoctl) -> Result<i32> {
+ // SAFETY: `ioctl` is copied into the kernel. It modifies the state in the kernel, not the
+ // state of this process in any way.
+ Ok(unsafe { _dm_dev_create(dm.0.as_raw_fd(), ioctl) }?)
+}
+
+fn dm_dev_suspend(dm: &DeviceMapper, ioctl: *mut DmIoctl) -> Result<i32> {
+ // SAFETY: `ioctl` is copied into the kernel. It modifies the state in the kernel, not the
+ // state of this process in any way.
+ Ok(unsafe { _dm_dev_suspend(dm.0.as_raw_fd(), ioctl) }?)
+}
+
+fn dm_table_load(dm: &DeviceMapper, ioctl: *mut DmIoctl) -> Result<i32> {
+ // SAFETY: `ioctl` is copied into the kernel. It modifies the state in the kernel, not the
+ // state of this process in any way.
+ Ok(unsafe { _dm_table_load(dm.0.as_raw_fd(), ioctl) }?)
+}
+
+fn dm_dev_remove(dm: &DeviceMapper, ioctl: *mut DmIoctl) -> Result<i32> {
+ // SAFETY: `ioctl` is copied into the kernel. It modifies the state in the kernel, not the
+ // state of this process in any way.
+ Ok(unsafe { _dm_dev_remove(dm.0.as_raw_fd(), ioctl) }?)
+}
+
+// `DmTargetSpec` is the header of the data structure for a device-mapper target. When doing the
+// ioctl, one of more `DmTargetSpec` (and its body) are appened to the `DmIoctl` struct.
+#[repr(C)]
+#[derive(Copy, Clone)]
+struct DmTargetSpec {
+ sector_start: u64,
+ length: u64, // number of 512 sectors
+ status: i32,
+ next: u32,
+ target_type: [u8; DM_MAX_TYPE_NAME],
+}
+
+// SAFETY: C struct is safe to be initialized from raw data
+unsafe impl DataInit for DmTargetSpec {}
+
+impl DmTargetSpec {
+ fn new(target_type: &str) -> Result<Self> {
+ // safe because the size of the array is the same as the size of the struct
+ let mut spec: Self = *DataInit::from_mut_slice(&mut [0; size_of::<Self>()]).unwrap();
+ spec.target_type.as_mut().write_all(target_type.as_bytes())?;
+ Ok(spec)
+ }
+}
+
+impl DmIoctl {
+ fn new(name: &str) -> Result<DmIoctl> {
+ // safe because the size of the array is the same as the size of the struct
+ let mut data: Self = *DataInit::from_mut_slice(&mut [0; size_of::<Self>()]).unwrap();
+ data.version[0] = DM_VERSION_MAJOR;
+ data.version[1] = DM_VERSION_MINOR;
+ data.version[2] = DM_VERSION_PATCHLEVEL;
+ data.data_size = size_of::<Self>() as u32;
+ data.data_start = 0;
+ data.name.as_mut().write_all(name.as_bytes())?;
+ Ok(data)
+ }
+
+ fn set_uuid(&mut self, uuid: &str) -> Result<()> {
+ let mut dst = self.uuid.as_mut();
+ dst.fill(0);
+ dst.write_all(uuid.as_bytes())?;
+ Ok(())
+ }
+}
+
+/// `DeviceMapper` is the entry point for the device mapper framework. It essentially is a file
+/// handle to "/dev/mapper/control".
+pub struct DeviceMapper(File);
+
+#[cfg(not(target_os = "android"))]
+const MAPPER_CONTROL: &str = "/dev/mapper/control";
+#[cfg(not(target_os = "android"))]
+const MAPPER_DEV_ROOT: &str = "/dev/mapper";
+
+#[cfg(target_os = "android")]
+const MAPPER_CONTROL: &str = "/dev/device-mapper";
+#[cfg(target_os = "android")]
+const MAPPER_DEV_ROOT: &str = "/dev/block/mapper";
+
+impl DeviceMapper {
+ /// Constructs a new `DeviceMapper` entrypoint. This is essentially the same as opening
+ /// "/dev/mapper/control".
+ pub fn new() -> Result<DeviceMapper> {
+ let f = OpenOptions::new()
+ .read(true)
+ .write(true)
+ .open(MAPPER_CONTROL)
+ .context(format!("failed to open {}", MAPPER_CONTROL))?;
+ Ok(DeviceMapper(f))
+ }
+
+ /// Creates a device mapper device and configure it according to the `target` specification.
+ /// The path to the generated device is "/dev/mapper/<name>".
+ pub fn create_verity_device(&self, name: &str, target: &DmVerityTarget) -> Result<PathBuf> {
+ // Step 1: create an empty device
+ let mut data = DmIoctl::new(name)?;
+ data.set_uuid(&uuid("apkver".as_bytes())?)?;
+ dm_dev_create(self, &mut data)
+ .context(format!("failed to create an empty device with name {}", &name))?;
+
+ // Step 2: load table onto the device
+ let payload_size = size_of::<DmIoctl>() + target.as_slice().len();
+
+ let mut data = DmIoctl::new(name)?;
+ data.data_size = payload_size as u32;
+ data.data_start = size_of::<DmIoctl>() as u32;
+ data.target_count = 1;
+ data.flags |= Flag::DM_READONLY_FLAG;
+
+ let mut payload = Vec::with_capacity(payload_size);
+ payload.extend_from_slice(data.as_slice());
+ payload.extend_from_slice(target.as_slice());
+ dm_table_load(self, payload.as_mut_ptr() as *mut DmIoctl)
+ .context("failed to load table")?;
+
+ // Step 3: activate the device (note: the term 'suspend' might be misleading, but it
+ // actually activates the table. See include/uapi/linux/dm-ioctl.h
+ let mut data = DmIoctl::new(name)?;
+ dm_dev_suspend(self, &mut data).context("failed to activate")?;
+
+ // Step 4: wait unti the device is created and return the device path
+ let path = Path::new(MAPPER_DEV_ROOT).join(&name);
+ wait_for_path(&path)?;
+ Ok(path)
+ }
+
+ /// Removes a mapper device
+ pub fn delete_device_deferred(&self, name: &str) -> Result<()> {
+ let mut data = DmIoctl::new(name)?;
+ data.flags |= Flag::DM_DEFERRED_REMOVE;
+ dm_dev_remove(self, &mut data)
+ .context(format!("failed to remove device with name {}", &name))?;
+ Ok(())
+ }
+}
+
+/// Used to derive a UUID that uniquely identifies a device mapper device when creating it.
+fn uuid(node_id: &[u8]) -> Result<String> {
+ use std::time::{SystemTime, UNIX_EPOCH};
+ use uuid::v1::{Context, Timestamp};
+ use uuid::Uuid;
+
+ let context = Context::new(0);
+ let now = SystemTime::now().duration_since(UNIX_EPOCH)?;
+ let ts = Timestamp::from_unix(&context, now.as_secs(), now.subsec_nanos());
+ let uuid = Uuid::new_v1(ts, node_id)?;
+ Ok(String::from(uuid.to_hyphenated().encode_lower(&mut Uuid::encode_buffer())))
+}