Store/Pass root digests of APEX payload
Root digests of APEX payload are now collected by microdroid_manager and
stored in instance.img and passed to apexd.
Bug: 199371341
Test: MicrodroidHostTestCases
Change-Id: I940347068400822f7d8140c3daf68036f553b087
diff --git a/microdroid_manager/src/payload/apex.rs b/microdroid_manager/src/payload/apex.rs
new file mode 100644
index 0000000..24c4f05
--- /dev/null
+++ b/microdroid_manager/src/payload/apex.rs
@@ -0,0 +1,225 @@
+// Copyright 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.
+
+//! Routines for handling APEX payload
+
+use anyhow::{anyhow, ensure, Result};
+use avb_bindgen::*;
+use std::ffi::{c_void, CStr};
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom};
+use std::mem::{size_of, zeroed};
+use std::ops::Deref;
+use std::ptr::null_mut;
+use std::slice::{from_raw_parts, from_raw_parts_mut};
+use zip::ZipArchive;
+
+const APEX_PUBKEY_ENTRY: &str = "apex_pubkey";
+const APEX_PAYLOAD_ENTRY: &str = "apex_payload.img";
+
+/// Verification result holds public key and root digest of apex_payload.img
+pub struct ApexVerificationResult {
+ pub public_key: Vec<u8>,
+ pub root_digest: Vec<u8>,
+}
+
+/// Verify APEX payload by AVB verification and return public key and root digest
+pub fn verify(path: &str) -> Result<ApexVerificationResult> {
+ let apex_file = File::open(path)?;
+ let (public_key, image_offset, image_size) = get_public_key_and_image_info(&apex_file)?;
+ let root_digest = verify_vbmeta(apex_file, image_offset, image_size, &public_key)?;
+ Ok(ApexVerificationResult { public_key, root_digest })
+}
+
+fn get_public_key_and_image_info(apex_file: &File) -> Result<(Vec<u8>, u64, u64)> {
+ let mut z = ZipArchive::new(apex_file)?;
+
+ let mut public_key = Vec::new();
+ z.by_name(APEX_PUBKEY_ENTRY)?.read_to_end(&mut public_key)?;
+
+ let (image_offset, image_size) =
+ z.by_name(APEX_PAYLOAD_ENTRY).map(|f| (f.data_start(), f.size()))?;
+
+ Ok((public_key, image_offset, image_size))
+}
+
+// Manual addition of a missing enum
+#[allow(non_camel_case_types, dead_code)]
+#[repr(u8)]
+enum AvbDescriptorTag {
+ AVB_DESCRIPTOR_TAG_PROPERTY = 0,
+ AVB_DESCRIPTOR_TAG_HASHTREE,
+ AVB_DESCRIPTOR_TAG_HASH,
+ AVB_DESCRIPTOR_TAG_KERNEL_CMDLINE,
+ AVB_DESCRIPTOR_TAG_CHAIN_PARTITION,
+}
+
+const FOOTER_SIZE: usize = size_of::<AvbFooter>();
+const HASHTREE_DESCRIPTOR_SIZE: usize = size_of::<AvbHashtreeDescriptor>();
+
+/// Verify VBmeta image and return root digest
+fn verify_vbmeta<R: Read + Seek>(
+ image: R,
+ offset: u64,
+ size: u64,
+ public_key: &[u8],
+) -> Result<Vec<u8>> {
+ let vbmeta = VbMeta::from(image, offset, size)?;
+ vbmeta.verify(public_key)?;
+ for &descriptor in vbmeta.descriptors()?.iter() {
+ if let Ok(hashtree_descriptor) = HashtreeDescriptor::from(descriptor) {
+ return hashtree_descriptor.root_digest();
+ }
+ }
+ Err(anyhow!("HashtreeDescriptor is not found."))
+}
+
+struct VbMeta {
+ data: Vec<u8>,
+}
+
+impl VbMeta {
+ // Read a VbMeta data from a given image
+ fn from<R: Read + Seek>(mut image: R, offset: u64, size: u64) -> Result<VbMeta> {
+ // Get AvbFooter first
+ image.seek(SeekFrom::Start(offset + size - FOOTER_SIZE as u64))?;
+ // SAFETY: AvbDescriptor is a "repr(C,packed)" struct from bindgen
+ let mut footer: AvbFooter = unsafe { zeroed() };
+ // SAFETY: safe to read because of seek(-FOOTER_SIZE) above
+ unsafe {
+ let footer_slice = from_raw_parts_mut(&mut footer as *mut _ as *mut u8, FOOTER_SIZE);
+ image.read_exact(footer_slice)?;
+ ensure!(avb_footer_validate_and_byteswap(&footer, &mut footer));
+ }
+ // Get VbMeta block
+ image.seek(SeekFrom::Start(offset + footer.vbmeta_offset))?;
+ let vbmeta_size = footer.vbmeta_size as usize;
+ let mut data = vec![0u8; vbmeta_size];
+ image.read_exact(&mut data)?;
+ Ok(VbMeta { data })
+ }
+ // Verify VbMeta image. Its enclosed public key should match with a given public key.
+ fn verify(&self, outer_public_key: &[u8]) -> Result<()> {
+ // SAFETY: self.data points to a valid VBMeta data and avb_vbmeta_image_verify should work fine
+ // with it
+ let public_key = unsafe {
+ let mut pk_ptr: *const u8 = null_mut();
+ let mut pk_len: usize = 0;
+ let res = avb_vbmeta_image_verify(
+ self.data.as_ptr(),
+ self.data.len(),
+ &mut pk_ptr,
+ &mut pk_len,
+ );
+ ensure!(
+ res == AvbVBMetaVerifyResult_AVB_VBMETA_VERIFY_RESULT_OK,
+ CStr::from_ptr(avb_vbmeta_verify_result_to_string(res))
+ .to_string_lossy()
+ .into_owned()
+ );
+ from_raw_parts(pk_ptr, pk_len)
+ };
+
+ ensure!(public_key == outer_public_key, "Public key mismatch with a given one.");
+ Ok(())
+ }
+ // Return a slice of AvbDescriptor pointers
+ fn descriptors(&self) -> Result<Descriptors> {
+ let mut num: usize = 0;
+ // SAFETY: ptr will be freed by Descriptor.
+ Ok(unsafe {
+ let ptr = avb_descriptor_get_all(self.data.as_ptr(), self.data.len(), &mut num);
+ ensure!(!ptr.is_null(), "VbMeta has no descriptors.");
+ let all = from_raw_parts(ptr, num);
+ Descriptors { ptr, all }
+ })
+ }
+}
+
+struct HashtreeDescriptor {
+ ptr: *const u8,
+ inner: AvbHashtreeDescriptor,
+}
+
+impl HashtreeDescriptor {
+ fn from(descriptor: *const AvbDescriptor) -> Result<HashtreeDescriptor> {
+ // SAFETY: AvbDescriptor is a "repr(C,packed)" struct from bindgen
+ let mut desc: AvbDescriptor = unsafe { zeroed() };
+ // SAFETY: both points to valid AvbDescriptor pointers
+ unsafe {
+ ensure!(avb_descriptor_validate_and_byteswap(descriptor, &mut desc));
+ }
+ ensure!({ desc.tag } == AvbDescriptorTag::AVB_DESCRIPTOR_TAG_HASHTREE as u64);
+ // SAFETY: AvbHashtreeDescriptor is a "repr(C, packed)" struct from bindgen
+ let mut hashtree_descriptor: AvbHashtreeDescriptor = unsafe { zeroed() };
+ // SAFETY: With tag == AVB_DESCRIPTOR_TAG_HASHTREE, descriptor should point to
+ // a AvbHashtreeDescriptor.
+ unsafe {
+ ensure!(avb_hashtree_descriptor_validate_and_byteswap(
+ descriptor as *const AvbHashtreeDescriptor,
+ &mut hashtree_descriptor,
+ ));
+ }
+ Ok(Self { ptr: descriptor as *const u8, inner: hashtree_descriptor })
+ }
+ fn root_digest(&self) -> Result<Vec<u8>> {
+ // SAFETY: digest_ptr should point to a valid buffer of root_digest_len
+ let root_digest = unsafe {
+ let digest_ptr = self.ptr.offset(
+ HASHTREE_DESCRIPTOR_SIZE as isize
+ + self.inner.partition_name_len as isize
+ + self.inner.salt_len as isize,
+ );
+ from_raw_parts(digest_ptr, self.inner.root_digest_len as usize)
+ };
+ Ok(root_digest.to_owned())
+ }
+}
+
+// Wraps pointer to a heap-allocated array of AvbDescriptor pointers
+struct Descriptors<'a> {
+ ptr: *mut *const AvbDescriptor,
+ all: &'a [*const AvbDescriptor],
+}
+
+// Wrapped pointer should be freed with avb_free.
+impl Drop for Descriptors<'_> {
+ fn drop(&mut self) {
+ // SAFETY: ptr is allocated by avb_descriptor_get_all
+ unsafe { avb_free(self.ptr as *mut c_void) }
+ }
+}
+
+impl<'a> Deref for Descriptors<'a> {
+ type Target = &'a [*const AvbDescriptor];
+ fn deref(&self) -> &Self::Target {
+ &self.all
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ fn to_hex_string(buf: &[u8]) -> String {
+ buf.iter().map(|b| format!("{:02x}", b)).collect()
+ }
+ #[test]
+ fn test_open_apex() {
+ let res = verify("tests/data/test.apex").unwrap();
+ assert_eq!(
+ to_hex_string(&res.root_digest),
+ "fe11ab17da0a3a738b54bdc3a13f6139cbdf91ec32f001f8d4bbbf8938e04e39"
+ );
+ }
+}