[client-vm] Build client VM CSR and sign the CSR with two keys
This cl builds the CSR that a client VM sends to the RKP VM for
remote attestation and adjusted the API accordingly as discussed
in the doc go/pvm-remote-attestation
The CSR payload is signed with both the CDI_Leaf_Priv of the
client VM's DICE chain and the attestation key. RKP VM should
verify the signature later with the CDI_Leaf_Pub extracted
from the same DICE chain in the CSR and the attestation public
key.
The new unit tests are added to config at cl/577763874.
Bug: 303807447
Test: run ServiceVmClientTestApp
Test: atest libservice_vm_comm.test
Test: atest microdroid_manager_test
Change-Id: Ic2c09e7339d9981edda028e2694fa551c911a274
diff --git a/service_vm/comm/Android.bp b/service_vm/comm/Android.bp
index 3a18052..6e05587 100644
--- a/service_vm/comm/Android.bp
+++ b/service_vm/comm/Android.bp
@@ -43,3 +43,31 @@
"std",
],
}
+
+rust_defaults {
+ name: "libservice_vm_comm_test_defaults",
+ crate_name: "diced_open_dice_test",
+ srcs: ["tests/*.rs"],
+ test_suites: ["general-tests"],
+ prefer_rlib: true,
+ rustlibs: [
+ "libdiced_sample_inputs",
+ "libdiced_open_dice",
+ ],
+}
+
+rust_test {
+ name: "libservice_vm_comm.test",
+ defaults: ["libservice_vm_comm_test_defaults"],
+ rustlibs: [
+ "libservice_vm_comm",
+ ],
+}
+
+rust_test {
+ name: "libservice_vm_comm_nostd.test",
+ defaults: ["libservice_vm_comm_test_defaults"],
+ rustlibs: [
+ "libservice_vm_comm_nostd",
+ ],
+}
diff --git a/service_vm/comm/TEST_MAPPING b/service_vm/comm/TEST_MAPPING
new file mode 100644
index 0000000..e677ba2
--- /dev/null
+++ b/service_vm/comm/TEST_MAPPING
@@ -0,0 +1,12 @@
+// When adding or removing tests here, don't forget to amend _all_modules list in
+// wireless/android/busytown/ath_config/configs/prod/avf/tests.gcl
+{
+ "avf-presubmit" : [
+ {
+ "name" : "libservice_vm_comm.test"
+ },
+ {
+ "name" : "libservice_vm_comm_nostd.test"
+ }
+ ]
+}
\ No newline at end of file
diff --git a/service_vm/comm/src/csr.rs b/service_vm/comm/src/csr.rs
new file mode 100644
index 0000000..5e1cbad
--- /dev/null
+++ b/service_vm/comm/src/csr.rs
@@ -0,0 +1,121 @@
+// Copyright 2023, 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.
+
+//! This module contains the structs related to the CSR (Certificate Signing Request)
+//! sent from the client VM to the service VM for attestation.
+
+use alloc::vec;
+use alloc::vec::Vec;
+use ciborium::Value;
+use coset::{self, CborSerializable, CoseError};
+
+/// Represents a CSR sent from the client VM to the service VM for attestation.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Csr {
+ /// The DICE certificate chain of the client VM.
+ pub dice_cert_chain: Vec<u8>,
+
+ /// The signed CSR payload in COSE_Sign structure, which includes two signatures:
+ /// - one by CDI_Leaf_Priv of the client VM's DICE chain,
+ /// - another by the private key corresponding to the public key.
+ pub signed_csr_payload: Vec<u8>,
+}
+
+impl Csr {
+ /// Serializes this object to a CBOR-encoded vector.
+ pub fn into_cbor_vec(self) -> coset::Result<Vec<u8>> {
+ let value = Value::Array(vec![
+ Value::Bytes(self.dice_cert_chain),
+ Value::Bytes(self.signed_csr_payload),
+ ]);
+ value.to_vec()
+ }
+
+ /// Creates an object instance from the provided CBOR-encoded slice.
+ pub fn from_cbor_slice(data: &[u8]) -> coset::Result<Self> {
+ let value = Value::from_slice(data)?;
+ let Value::Array(mut arr) = value else {
+ return Err(CoseError::UnexpectedItem(cbor_value_type(&value), "array"));
+ };
+ if arr.len() != 2 {
+ return Err(CoseError::UnexpectedItem("array", "array with 2 items"));
+ }
+ Ok(Self {
+ signed_csr_payload: try_as_bytes(arr.remove(1))?,
+ dice_cert_chain: try_as_bytes(arr.remove(0))?,
+ })
+ }
+}
+
+/// Represents the data to be signed and sent from the client VM to the service VM
+/// for attestation.
+///
+/// It will be signed by both CDI_Leaf_Priv of the client VM's DICE chain and
+/// the private key corresponding to the public key to be attested.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct CsrPayload {
+ /// COSE_Key encoded EC P-256 public key to be attested.
+ pub public_key: Vec<u8>,
+
+ /// A random array with a length between 0 and 64.
+ /// It will be included in the certificate chain in the attestation result,
+ /// serving as proof of the freshness of the result.
+ pub challenge: Vec<u8>,
+}
+
+impl CsrPayload {
+ /// Serializes this object to a CBOR-encoded vector.
+ pub fn into_cbor_vec(self) -> coset::Result<Vec<u8>> {
+ let value = Value::Array(vec![Value::Bytes(self.public_key), Value::Bytes(self.challenge)]);
+ value.to_vec()
+ }
+
+ /// Creates an object instance from the provided CBOR-encoded slice.
+ pub fn from_cbor_slice(data: &[u8]) -> coset::Result<Self> {
+ let value = Value::from_slice(data)?;
+ let Value::Array(mut arr) = value else {
+ return Err(CoseError::UnexpectedItem(cbor_value_type(&value), "array"));
+ };
+ if arr.len() != 2 {
+ return Err(CoseError::UnexpectedItem("array", "array with 2 items"));
+ }
+ Ok(Self {
+ challenge: try_as_bytes(arr.remove(1))?,
+ public_key: try_as_bytes(arr.remove(0))?,
+ })
+ }
+}
+
+fn try_as_bytes(v: Value) -> coset::Result<Vec<u8>> {
+ if let Value::Bytes(data) = v {
+ Ok(data)
+ } else {
+ Err(CoseError::UnexpectedItem(cbor_value_type(&v), "bytes"))
+ }
+}
+
+fn cbor_value_type(v: &Value) -> &'static str {
+ match v {
+ Value::Integer(_) => "int",
+ Value::Bytes(_) => "bstr",
+ Value::Float(_) => "float",
+ Value::Text(_) => "tstr",
+ Value::Bool(_) => "bool",
+ Value::Null => "nul",
+ Value::Tag(_, _) => "tag",
+ Value::Array(_) => "array",
+ Value::Map(_) => "map",
+ _ => "other",
+ }
+}
diff --git a/service_vm/comm/src/lib.rs b/service_vm/comm/src/lib.rs
index d8f7bd7..0818f24 100644
--- a/service_vm/comm/src/lib.rs
+++ b/service_vm/comm/src/lib.rs
@@ -19,9 +19,11 @@
extern crate alloc;
+mod csr;
mod message;
mod vsock;
+pub use csr::{Csr, CsrPayload};
pub use message::{
EcdsaP256KeyPair, GenerateCertificateRequestParams, Request, RequestProcessingError, Response,
ServiceVmRequest,
diff --git a/service_vm/comm/tests/api_test.rs b/service_vm/comm/tests/api_test.rs
new file mode 100644
index 0000000..44a3ef9
--- /dev/null
+++ b/service_vm/comm/tests/api_test.rs
@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2023 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.
+ */
+
+use diced_open_dice::DiceArtifacts;
+use service_vm_comm::{Csr, CsrPayload};
+
+/// The following test data are generated with urandom
+const DATA1: [u8; 32] = [
+ 0x8b, 0x09, 0xc0, 0x7e, 0x20, 0x3c, 0xa2, 0x11, 0x7e, 0x7f, 0x0b, 0xdd, 0x2b, 0x68, 0x98, 0xb0,
+ 0x2b, 0x34, 0xb5, 0x63, 0x39, 0x01, 0x90, 0x06, 0xaf, 0x5f, 0xdd, 0xb7, 0x81, 0xca, 0xc7, 0x46,
+];
+const DATA2: [u8; 16] = [
+ 0x6c, 0xb9, 0x39, 0x86, 0x9b, 0x2f, 0x12, 0xd8, 0x45, 0x92, 0x57, 0x44, 0x65, 0xce, 0x94, 0x63,
+];
+
+#[test]
+fn csr_payload_cbor_serialization() {
+ let csr_payload = CsrPayload { public_key: DATA1.to_vec(), challenge: DATA2.to_vec() };
+ let expected_csr_payload = csr_payload.clone();
+ let cbor_vec = csr_payload.into_cbor_vec().unwrap();
+ let deserialized_csr_payload = CsrPayload::from_cbor_slice(&cbor_vec).unwrap();
+
+ assert_eq!(expected_csr_payload, deserialized_csr_payload);
+}
+
+#[test]
+fn csr_cbor_serialization() {
+ let dice_artifacts = diced_sample_inputs::make_sample_bcc_and_cdis().unwrap();
+ let dice_cert_chain = dice_artifacts.bcc().unwrap().to_vec();
+ let csr = Csr { signed_csr_payload: DATA1.to_vec(), dice_cert_chain };
+ let expected_csr = csr.clone();
+ let cbor_vec = csr.into_cbor_vec().unwrap();
+ let deserialized_csr = Csr::from_cbor_slice(&cbor_vec).unwrap();
+
+ assert_eq!(expected_csr, deserialized_csr);
+}
diff --git a/service_vm/test_apk/src/main.rs b/service_vm/test_apk/src/main.rs
index 7d8416f..ba65aca 100644
--- a/service_vm/test_apk/src/main.rs
+++ b/service_vm/test_apk/src/main.rs
@@ -14,10 +14,20 @@
//! Main executable of Service VM client for manual testing.
-use anyhow::Result;
+use anyhow::{anyhow, ensure, Result};
use log::{error, info};
-use std::{ffi::c_void, panic};
-use vm_payload_bindgen::AVmPayload_requestAttestation;
+use std::{
+ ffi::{c_void, CStr},
+ panic,
+ ptr::{self, NonNull},
+ result,
+};
+use vm_payload_bindgen::{
+ attestation_status_t, AVmAttestationResult, AVmAttestationResult_free,
+ AVmAttestationResult_getCertificateAt, AVmAttestationResult_getCertificateCount,
+ AVmAttestationResult_getPrivateKey, AVmAttestationResult_resultToString,
+ AVmAttestationResult_sign, AVmPayload_requestAttestation,
+};
/// Entry point of the Service VM client.
#[allow(non_snake_case)]
@@ -40,38 +50,180 @@
fn try_main() -> Result<()> {
info!("Welcome to Service VM Client!");
+
+ let too_big_challenge = &[0u8; 66];
+ let res = AttestationResult::request_attestation(too_big_challenge);
+ ensure!(res.is_err());
+ let status = res.unwrap_err();
+ ensure!(
+ status == attestation_status_t::ATTESTATION_ERROR_INVALID_CHALLENGE,
+ "Unexpected status: {:?}",
+ status
+ );
+ info!("Status: {:?}", status_to_cstr(status));
+
// The data below is only a placeholder generated randomly with urandom
let challenge = &[
0x6c, 0xad, 0x52, 0x50, 0x15, 0xe7, 0xf4, 0x1d, 0xa5, 0x60, 0x7e, 0xd2, 0x7d, 0xf1, 0x51,
0x67, 0xc3, 0x3e, 0x73, 0x9b, 0x30, 0xbd, 0x04, 0x20, 0x2e, 0xde, 0x3b, 0x1d, 0xc8, 0x07,
0x11, 0x7b,
];
- info!("Sending challenge: {:?}", challenge);
- let certificate = request_attestation(challenge);
- info!("Certificate: {:?}", certificate);
+ let res = AttestationResult::request_attestation(challenge)
+ .map_err(|e| anyhow!("Unexpected status: {:?}", status_to_cstr(e)))?;
+
+ let cert_chain = res.certificate_chain()?;
+ info!("Attestation result certificateChain = {:?}", cert_chain);
+
+ let private_key = res.private_key()?;
+ info!("Attestation result privateKey = {:?}", private_key);
+
+ let message = b"Hello from Service VM client";
+ info!("Signing message: {:?}", message);
+ let signature = res.sign(message)?;
+ info!("Signature: {:?}", signature);
+
Ok(())
}
-fn request_attestation(challenge: &[u8]) -> Vec<u8> {
- // SAFETY: It is safe as we only request the size of the certificate in this call.
- let certificate_size = unsafe {
- AVmPayload_requestAttestation(
- challenge.as_ptr() as *const c_void,
- challenge.len(),
- [].as_mut_ptr(),
+#[derive(Debug)]
+struct AttestationResult(NonNull<AVmAttestationResult>);
+
+impl AttestationResult {
+ fn request_attestation(challenge: &[u8]) -> result::Result<Self, attestation_status_t> {
+ let mut res: *mut AVmAttestationResult = ptr::null_mut();
+ // SAFETY: It is safe as we only read the challenge within its bounds and the
+ // function does not retain any reference to it.
+ let status = unsafe {
+ AVmPayload_requestAttestation(
+ challenge.as_ptr() as *const c_void,
+ challenge.len(),
+ &mut res,
+ )
+ };
+ if status == attestation_status_t::ATTESTATION_OK {
+ info!("Attestation succeeds. Status: {:?}", status_to_cstr(status));
+ let res = NonNull::new(res).expect("The attestation result is null");
+ Ok(Self(res))
+ } else {
+ Err(status)
+ }
+ }
+
+ fn certificate_chain(&self) -> Result<Vec<Box<[u8]>>> {
+ let num_certs = get_certificate_count(self.as_ref());
+ let mut certs = Vec::with_capacity(num_certs);
+ for i in 0..num_certs {
+ certs.push(get_certificate_at(self.as_ref(), i)?);
+ }
+ Ok(certs)
+ }
+
+ fn private_key(&self) -> Result<Box<[u8]>> {
+ get_private_key(self.as_ref())
+ }
+
+ fn sign(&self, message: &[u8]) -> Result<Box<[u8]>> {
+ sign_with_attested_key(self.as_ref(), message)
+ }
+}
+
+impl AsRef<AVmAttestationResult> for AttestationResult {
+ fn as_ref(&self) -> &AVmAttestationResult {
+ // SAFETY: This field is private, and only populated with a successful call to
+ // `AVmPayload_requestAttestation`.
+ unsafe { self.0.as_ref() }
+ }
+}
+
+impl Drop for AttestationResult {
+ fn drop(&mut self) {
+ // SAFETY: This field is private, and only populated with a successful call to
+ // `AVmPayload_requestAttestation`, and not freed elsewhere.
+ unsafe { AVmAttestationResult_free(self.0.as_ptr()) };
+ }
+}
+
+fn get_certificate_count(res: &AVmAttestationResult) -> usize {
+ // SAFETY: The result is returned by `AVmPayload_requestAttestation` and should be valid
+ // before getting freed.
+ unsafe { AVmAttestationResult_getCertificateCount(res) }
+}
+
+fn get_certificate_at(res: &AVmAttestationResult, index: usize) -> Result<Box<[u8]>> {
+ let size =
+ // SAFETY: The result is returned by `AVmPayload_requestAttestation` and should be valid
+ // before getting freed.
+ unsafe { AVmAttestationResult_getCertificateAt(res, index, ptr::null_mut(), 0) };
+ let mut cert = vec![0u8; size];
+ // SAFETY: The result is returned by `AVmPayload_requestAttestation` and should be valid
+ // before getting freed. This function only writes within the bounds of `cert`.
+ // And `cert` cannot overlap `res` because we just allocated it.
+ let size = unsafe {
+ AVmAttestationResult_getCertificateAt(
+ res,
+ index,
+ cert.as_mut_ptr() as *mut c_void,
+ cert.len(),
+ )
+ };
+ ensure!(size == cert.len());
+ Ok(cert.into_boxed_slice())
+}
+
+fn get_private_key(res: &AVmAttestationResult) -> Result<Box<[u8]>> {
+ let size =
+ // SAFETY: The result is returned by `AVmPayload_requestAttestation` and should be valid
+ // before getting freed.
+ unsafe { AVmAttestationResult_getPrivateKey(res, ptr::null_mut(), 0) };
+ let mut private_key = vec![0u8; size];
+ // SAFETY: The result is returned by `AVmPayload_requestAttestation` and should be valid
+ // before getting freed. This function only writes within the bounds of `private_key`.
+ // And `private_key` cannot overlap `res` because we just allocated it.
+ let size = unsafe {
+ AVmAttestationResult_getPrivateKey(
+ res,
+ private_key.as_mut_ptr() as *mut c_void,
+ private_key.len(),
+ )
+ };
+ ensure!(size == private_key.len());
+ Ok(private_key.into_boxed_slice())
+}
+
+fn sign_with_attested_key(res: &AVmAttestationResult, message: &[u8]) -> Result<Box<[u8]>> {
+ // SAFETY: The result is returned by `AVmPayload_requestAttestation` and should be valid
+ // before getting freed.
+ let size = unsafe {
+ AVmAttestationResult_sign(
+ res,
+ message.as_ptr() as *const c_void,
+ message.len(),
+ ptr::null_mut(),
0,
)
};
- let mut certificate = vec![0u8; certificate_size];
- // SAFETY: It is safe as we only write the data into the given buffer within the buffer
- // size in this call.
- unsafe {
- AVmPayload_requestAttestation(
- challenge.as_ptr() as *const c_void,
- challenge.len(),
- certificate.as_mut_ptr() as *mut c_void,
- certificate.len(),
- );
+ let mut signature = vec![0u8; size];
+ // SAFETY: The result is returned by `AVmPayload_requestAttestation` and should be valid
+ // before getting freed. This function only writes within the bounds of `signature`.
+ // And `signature` cannot overlap `res` because we just allocated it.
+ let size = unsafe {
+ AVmAttestationResult_sign(
+ res,
+ message.as_ptr() as *const c_void,
+ message.len(),
+ signature.as_mut_ptr() as *mut c_void,
+ signature.len(),
+ )
};
- certificate
+ ensure!(size == signature.len());
+ Ok(signature.into_boxed_slice())
+}
+
+fn status_to_cstr(status: attestation_status_t) -> &'static CStr {
+ // SAFETY: The function only reads the given enum status and returns a pointer to a
+ // static string.
+ let message = unsafe { AVmAttestationResult_resultToString(status) };
+ // SAFETY: The pointer returned by `AVmAttestationResult_resultToString` is guaranteed to
+ // point to a valid C String.
+ unsafe { CStr::from_ptr(message) }
}