[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/vm_payload/Android.bp b/vm_payload/Android.bp
index b5322a8..7f2b9df 100644
--- a/vm_payload/Android.bp
+++ b/vm_payload/Android.bp
@@ -19,11 +19,26 @@
"liblazy_static",
"liblibc",
"liblog_rust",
+ "libopenssl",
"librpcbinder_rs",
+ "libvm_payload_status_bindgen",
"libvsock",
],
}
+rust_bindgen {
+ name: "libvm_payload_status_bindgen",
+ wrapper_src: "include/vm_payload.h",
+ crate_name: "vm_payload_status_bindgen",
+ defaults: ["avf_build_flags_rust"],
+ source_stem: "bindings",
+ bindgen_flags: [
+ "--default-enum-style rust",
+ "--allowlist-type=attestation_status_t",
+ ],
+ visibility: [":__subpackages__"],
+}
+
// Rust wrappers round the C API for Rust clients.
// (Yes, this involves going Rust -> C -> Rust.)
rust_bindgen {
@@ -33,6 +48,9 @@
defaults: ["avf_build_flags_rust"],
source_stem: "bindings",
apex_available: ["com.android.compos"],
+ bindgen_flags: [
+ "--default-enum-style rust",
+ ],
visibility: [
"//packages/modules/Virtualization/compos",
"//packages/modules/Virtualization/service_vm/test_apk",
@@ -49,6 +67,7 @@
"libbinder_ndk",
"libbinder_rpc_unstable",
"liblog",
+ "libcrypto",
],
whole_static_libs: ["libvm_payload_impl"],
export_static_lib_headers: ["libvm_payload_impl"],
diff --git a/vm_payload/include-restricted/vm_payload_restricted.h b/vm_payload/include-restricted/vm_payload_restricted.h
index ee92366..15c37ed 100644
--- a/vm_payload/include-restricted/vm_payload_restricted.h
+++ b/vm_payload/include-restricted/vm_payload_restricted.h
@@ -55,23 +55,4 @@
*/
size_t AVmPayload_getDiceAttestationCdi(void* _Nullable data, size_t size);
-/**
- * Requests the remote attestation of the client VM.
- *
- * The challenge will be included in the certificate chain in the attestation result,
- * serving as proof of the freshness of the result.
- *
- * \param challenge A pointer to the challenge buffer.
- * \param challenge_size size of the challenge, the maximum supported challenge size is
- * 64 bytes. An error will be returned if an invalid challenge is
- * passed.
- * \param buffer A pointer to the certificate buffer.
- * \param size number of bytes that can be written to the certificate buffer.
- *
- * \return the total size of the certificate
- */
-size_t AVmPayload_requestAttestation(const void* _Nonnull challenge, size_t challenge_size,
- void* _Nullable buffer, size_t size)
- __INTRODUCED_IN(__ANDROID_API_V__);
-
__END_DECLS
diff --git a/vm_payload/include/vm_payload.h b/vm_payload/include/vm_payload.h
index c28cd42..2dfa2cb 100644
--- a/vm_payload/include/vm_payload.h
+++ b/vm_payload/include/vm_payload.h
@@ -30,6 +30,27 @@
typedef struct AIBinder AIBinder;
/**
+ * Introduced in API 35.
+ * Remote attestation result if the attestation succeeds.
+ */
+struct AVmAttestationResult;
+
+/**
+ * Introduced in API 35.
+ * Remote attestation status types returned from remote attestation functions.
+ */
+typedef enum attestation_status_t : int32_t {
+ /** The remote attestation completes successfully. */
+ ATTESTATION_OK = 0,
+
+ /** The remote attestation has failed due to an unspecified cause. */
+ ATTESTATION_UNKNOWN_ERROR = -10000,
+
+ /** The challenge size is not between 0 and 64. */
+ ATTESTATION_ERROR_INVALID_CHALLENGE = -10001,
+} attestation_status_t;
+
+/**
* Notifies the host that the payload is ready.
*
* If the host app has set a `VirtualMachineCallback` for the VM, its
@@ -112,4 +133,129 @@
*/
const char* _Nullable AVmPayload_getEncryptedStoragePath(void);
+/**
+ * Requests the remote attestation of the client VM.
+ *
+ * The challenge will be included in the certificate chain in the attestation result,
+ * serving as proof of the freshness of the result.
+ *
+ * \param challenge A pointer to the challenge buffer.
+ * \param challenge_size size of the challenge. The maximum supported challenge size is
+ * 64 bytes. The status ATTESTATION_ERROR_INVALID_CHALLENGE will be returned if
+ * an invalid challenge is passed.
+ * \param result The remote attestation result will be filled here if the attestation
+ * succeeds. The result remains valid until it is freed with
+ * `AVmPayload_freeAttestationResult`.
+ *
+ * \return ATTESTATION_OK upon successful attestation.
+ */
+attestation_status_t AVmPayload_requestAttestation(
+ const void* _Nonnull challenge, size_t challenge_size,
+ struct AVmAttestationResult* _Nullable* _Nonnull result) __INTRODUCED_IN(__ANDROID_API_V__);
+
+/**
+ * Converts the return value from `AVmPayload_requestAttestation` to a text string
+ * representing the status code.
+ *
+ * \return a constant string value representing the status code. The string should not
+ * be deleted or freed by the application and remains valid for the lifetime of the VM.
+ */
+const char* _Nonnull AVmAttestationResult_resultToString(attestation_status_t status)
+ __INTRODUCED_IN(__ANDROID_API_V__);
+
+/**
+ * Frees all the data owned by the provided attestation result, including the result itself.
+ *
+ * Callers should ensure to invoke this API only once on a valid attestation result
+ * returned by `AVmPayload_requestAttestation` to avoid undefined behavior.
+ *
+ * \param result A pointer to the attestation result.
+ */
+void AVmAttestationResult_free(struct AVmAttestationResult* _Nullable result)
+ __INTRODUCED_IN(__ANDROID_API_V__);
+
+/**
+ * Reads the DER-encoded ECPrivateKey structure specified in [RFC 5915 s3] for the
+ * EC P-256 private key from the provided attestation result.
+ *
+ * \param result A pointer to the attestation result filled in
+ * `AVmPayload_requestAttestation` when the attestation succeeds.
+ * \param data A pointer to the memory where the private key will be written
+ * (can be null if size is 0).
+ * \param size The maximum number of bytes that can be written to the data buffer.
+ * If `size` is smaller than the total size of the private key, the key data will be
+ * truncated to this `size`.
+ *
+ * \return The total size of the private key.
+ *
+ * [RFC 5915 s3]: https://datatracker.ietf.org/doc/html/rfc5915#section-3
+ */
+size_t AVmAttestationResult_getPrivateKey(const struct AVmAttestationResult* _Nonnull result,
+ void* _Nullable data, size_t size)
+ __INTRODUCED_IN(__ANDROID_API_V__);
+
+/**
+ * Signs the given message using ECDSA P-256, the message is first hashed with SHA-256 and
+ * then it is signed with the attested EC P-256 private key in the attestation result.
+ *
+ * \param result A pointer to the attestation result filled in
+ * `AVmPayload_requestAttestation` when the attestation succeeds.
+ * \param message A pointer to the message buffer.
+ * \param message_size size of the message.
+ * \param data A pointer to the memory where the signature will be written
+ * (can be null if size is 0). The signature is a DER-encoded ECDSASignature structure
+ * detailed in the [RFC 6979].
+ * \param size The maximum number of bytes that can be written to the data buffer.
+ * If `size` is smaller than the total size of the signature, the signature will be
+ * truncated to this `size`.
+ *
+ * \return The total size of the signature.
+ *
+ * [RFC 6979]: https://datatracker.ietf.org/doc/html/rfc6979
+ */
+size_t AVmAttestationResult_sign(const struct AVmAttestationResult* _Nonnull result,
+ const void* _Nonnull message, size_t message_size,
+ void* _Nullable data, size_t size)
+ __INTRODUCED_IN(__ANDROID_API_V__);
+
+/**
+ * Gets the number of certificates in the certificate chain.
+ *
+ * The certificate chain consists of a sequence of DER-encoded X.509 certificates that form
+ * the attestation key's certificate chain. It starts with a root certificate and ends with a
+ * leaf certificate covering the attested public key.
+ *
+ * \param result A pointer to the attestation result obtained from `AVmPayload_requestAttestation`
+ * when the attestation succeeds.
+ *
+ * \return The number of certificates in the certificate chain.
+ */
+size_t AVmAttestationResult_getCertificateCount(const struct AVmAttestationResult* _Nonnull result)
+ __INTRODUCED_IN(__ANDROID_API_V__);
+
+/**
+ * Retrieves the certificate at the given `index` from the certificate chain in the provided
+ * attestation result.
+ *
+ * The certificate chain consists of a sequence of DER-encoded X.509 certificates that form
+ * the attestation key's certificate chain. It starts with a root certificate and ends with a
+ * leaf certificate covering the attested public key.
+ *
+ * \param result A pointer to the attestation result obtained from `AVmPayload_requestAttestation`
+ * when the attestation succeeds.
+ * \param index Index of the certificate to retrieve. The `index` must be within the range of
+ * [0, number of certificates). The number of certificates can be obtained with
+ * `AVmAttestationResult_getCertificateCount`.
+ * \param data A pointer to the memory where the certificate will be written
+ * (can be null if size is 0).
+ * \param size The maximum number of bytes that can be written to the data buffer. If `size`
+ * is smaller than the total size of the certificate, the certificate will be
+ * truncated to this `size`.
+ *
+ * \return The total size of the certificate at the given `index`.
+ */
+size_t AVmAttestationResult_getCertificateAt(const struct AVmAttestationResult* _Nonnull result,
+ size_t index, void* _Nullable data, size_t size)
+ __INTRODUCED_IN(__ANDROID_API_V__);
+
__END_DECLS
diff --git a/vm_payload/libvm_payload.map.txt b/vm_payload/libvm_payload.map.txt
index 32dd33b..975a5a3 100644
--- a/vm_payload/libvm_payload.map.txt
+++ b/vm_payload/libvm_payload.map.txt
@@ -8,6 +8,12 @@
AVmPayload_getApkContentsPath; # systemapi introduced=UpsideDownCake
AVmPayload_getEncryptedStoragePath; # systemapi introduced=UpsideDownCake
AVmPayload_requestAttestation; # systemapi introduced=VanillaIceCream
+ AVmAttestationResult_getPrivateKey; # systemapi introduced=VanillaIceCream
+ AVmAttestationResult_sign; # systemapi introduced=VanillaIceCream
+ AVmAttestationResult_free; # systemapi introduced=VanillaIceCream
+ AVmAttestationResult_resultToString; # systemapi introduced=VanillaIceCream
+ AVmAttestationResult_getCertificateCount; # systemapi introduced=VanillaIceCream
+ AVmAttestationResult_getCertificateAt; # systemapi introduced=VanillaIceCream
local:
*;
};
diff --git a/vm_payload/src/api.rs b/vm_payload/src/api.rs
index 93dbd1c..64f8d6a 100644
--- a/vm_payload/src/api.rs
+++ b/vm_payload/src/api.rs
@@ -14,20 +14,30 @@
//! This module handles the interaction with virtual machine payload service.
-use android_system_virtualization_payload::aidl::android::system::virtualization::payload::IVmPayloadService::{
- ENCRYPTEDSTORE_MOUNTPOINT, IVmPayloadService, VM_PAYLOAD_SERVICE_SOCKET_NAME, VM_APK_CONTENTS_PATH};
-use anyhow::{ensure, bail, Context, Result};
-use binder::{Strong, unstable_api::{AIBinder, new_spibinder}};
+use android_system_virtualization_payload::aidl::android::system::virtualization::payload:: IVmPayloadService::{
+ IVmPayloadService, ENCRYPTEDSTORE_MOUNTPOINT, VM_APK_CONTENTS_PATH,
+ VM_PAYLOAD_SERVICE_SOCKET_NAME, AttestationResult::AttestationResult,
+};
+use anyhow::{bail, ensure, Context, Result};
+use binder::{
+ unstable_api::{new_spibinder, AIBinder},
+ Strong,
+};
use lazy_static::lazy_static;
use log::{error, info, Level};
-use rpcbinder::{RpcSession, RpcServer};
+use rpcbinder::{RpcServer, RpcSession};
+use openssl::{ec::EcKey, sha::sha256, ecdsa::EcdsaSig};
use std::convert::Infallible;
-use std::ffi::CString;
+use std::ffi::{CString, CStr};
use std::fmt::Debug;
use std::os::raw::{c_char, c_void};
use std::path::Path;
-use std::ptr;
-use std::sync::{Mutex, atomic::{AtomicBool, Ordering}};
+use std::ptr::{self, NonNull};
+use std::sync::{
+ atomic::{AtomicBool, Ordering},
+ Mutex,
+};
+use vm_payload_status_bindgen::attestation_status_t;
lazy_static! {
static ref VM_APK_CONTENTS_PATH_C: CString =
@@ -263,42 +273,210 @@
/// Behavior is undefined if any of the following conditions are violated:
///
/// * `challenge` must be [valid] for reads of `challenge_size` bytes.
-/// * `buffer` must be [valid] for writes of `size` bytes. `buffer` can be null if `size` is 0.
+/// * `res` must be [valid] to write the attestation result.
+/// * The region of memory beginning at `challenge` with `challenge_size` bytes must not
+/// overlap with the region of memory `res` points to.
///
/// [valid]: ptr#safety
#[no_mangle]
pub unsafe extern "C" fn AVmPayload_requestAttestation(
challenge: *const u8,
challenge_size: usize,
- buffer: *mut u8,
+ res: &mut *mut AttestationResult,
+) -> attestation_status_t {
+ initialize_logging();
+ const MAX_CHALLENGE_SIZE: usize = 64;
+ if challenge_size > MAX_CHALLENGE_SIZE {
+ return attestation_status_t::ATTESTATION_ERROR_INVALID_CHALLENGE;
+ }
+ let challenge = if challenge_size == 0 {
+ &[]
+ } else {
+ // SAFETY: The caller guarantees that `challenge` is valid for reads of
+ // `challenge_size` bytes and `challenge_size` is not zero.
+ unsafe { std::slice::from_raw_parts(challenge, challenge_size) }
+ };
+ let attestation_res = unwrap_or_abort(try_request_attestation(challenge));
+ *res = Box::into_raw(Box::new(attestation_res));
+ attestation_status_t::ATTESTATION_OK
+}
+
+fn try_request_attestation(public_key: &[u8]) -> Result<AttestationResult> {
+ get_vm_payload_service()?
+ .requestAttestation(public_key)
+ .context("Failed to request attestation")
+}
+
+/// Converts the return value from `AVmPayload_requestAttestation` to a text string
+/// representing the error code.
+#[no_mangle]
+pub extern "C" fn AVmAttestationResult_resultToString(
+ status: attestation_status_t,
+) -> *const c_char {
+ let message = match status {
+ attestation_status_t::ATTESTATION_OK => {
+ CStr::from_bytes_with_nul(b"The remote attestation completes successfully.\0").unwrap()
+ }
+ attestation_status_t::ATTESTATION_ERROR_INVALID_CHALLENGE => {
+ CStr::from_bytes_with_nul(b"The challenge size is not between 0 and 64.\0").unwrap()
+ }
+ _ => CStr::from_bytes_with_nul(
+ b"The remote attestation has failed due to an unspecified cause.\0",
+ )
+ .unwrap(),
+ };
+ message.as_ptr()
+}
+
+/// Reads the DER-encoded ECPrivateKey structure specified in [RFC 5915 s3] for the
+/// EC P-256 private key from the provided attestation result.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `data` must be [valid] for writes of `size` bytes, if size > 0.
+/// * The region of memory beginning at `data` with `size` bytes must not overlap with the
+/// region of memory `res` points to.
+///
+/// [valid]: ptr#safety
+/// [RFC 5915 s3]: https://datatracker.ietf.org/doc/html/rfc5915#section-3
+#[no_mangle]
+pub unsafe extern "C" fn AVmAttestationResult_getPrivateKey(
+ res: &AttestationResult,
+ data: *mut u8,
size: usize,
) -> usize {
- initialize_logging();
+ let private_key = &res.privateKey;
+ if size != 0 {
+ let data = NonNull::new(data).expect("data must not be null when size > 0");
+ // SAFETY: See the requirements on `data` above. The number of bytes copied doesn't exceed
+ // the length of either buffer, and the caller ensures that `private_key` cannot overlap
+ // `data`. We allow data to be null, which is never valid, but only if size == 0
+ // which is checked above.
+ unsafe {
+ ptr::copy_nonoverlapping(
+ private_key.as_ptr(),
+ data.as_ptr(),
+ std::cmp::min(private_key.len(), size),
+ )
+ };
+ }
+ private_key.len()
+}
- // SAFETY: See the requirements on `challenge` above.
- let challenge = unsafe { std::slice::from_raw_parts(challenge, challenge_size) };
- let certificate = unwrap_or_abort(try_request_attestation(challenge));
+/// Signs the given message using ECDSA P-256, the message is first hashed with SHA-256 and
+/// then it is signed with the attested EC P-256 private key in the attestation result.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `message` must be [valid] for reads of `message_size` bytes.
+/// * `data` must be [valid] for writes of `size` bytes, if size > 0.
+/// * The region of memory beginning at `data` with `size` bytes must not overlap with the
+/// region of memory `res` or `message` point to.
+///
+///
+/// [valid]: ptr#safety
+#[no_mangle]
+pub unsafe extern "C" fn AVmAttestationResult_sign(
+ res: &AttestationResult,
+ message: *const u8,
+ message_size: usize,
+ data: *mut u8,
+ size: usize,
+) -> usize {
+ if message_size == 0 {
+ panic!("Message to be signed must not be empty.")
+ }
+ // SAFETY: See the requirements on `message` above.
+ let message = unsafe { std::slice::from_raw_parts(message, message_size) };
+ let signature = unwrap_or_abort(try_ecdsa_sign(message, &res.privateKey));
+ if size != 0 {
+ let data = NonNull::new(data).expect("data must not be null when size > 0");
+ // SAFETY: See the requirements on `data` above. The number of bytes copied doesn't exceed
+ // the length of either buffer, and the caller ensures that `signature` cannot overlap
+ // `data`. We allow data to be null, which is never valid, but only if size == 0
+ // which is checked above.
+ unsafe {
+ ptr::copy_nonoverlapping(
+ signature.as_ptr(),
+ data.as_ptr(),
+ std::cmp::min(signature.len(), size),
+ )
+ };
+ }
+ signature.len()
+}
- if size != 0 || buffer.is_null() {
- // SAFETY: See the requirements on `buffer` above. The number of bytes copied doesn't exceed
- // the length of either buffer, and `certificate` cannot overlap `buffer` because we just
- // allocated it.
+fn try_ecdsa_sign(message: &[u8], der_encoded_ec_private_key: &[u8]) -> Result<Vec<u8>> {
+ let private_key = EcKey::private_key_from_der(der_encoded_ec_private_key)?;
+ let digest = sha256(message);
+ let sig = EcdsaSig::sign(&digest, &private_key)?;
+ Ok(sig.to_der()?)
+}
+
+/// Gets the number of certificates in the certificate chain.
+#[no_mangle]
+pub extern "C" fn AVmAttestationResult_getCertificateCount(res: &AttestationResult) -> usize {
+ res.certificateChain.len()
+}
+
+/// Retrieves the certificate at the given `index` from the certificate chain in the provided
+/// attestation result.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `data` must be [valid] for writes of `size` bytes, if size > 0.
+/// * `index` must be within the range of [0, number of certificates). The number of certificates
+/// can be obtained with `AVmAttestationResult_getCertificateCount`.
+/// * The region of memory beginning at `data` with `size` bytes must not overlap with the
+/// region of memory `res` points to.
+///
+/// [valid]: ptr#safety
+#[no_mangle]
+pub unsafe extern "C" fn AVmAttestationResult_getCertificateAt(
+ res: &AttestationResult,
+ index: usize,
+ data: *mut u8,
+ size: usize,
+) -> usize {
+ let certificate =
+ &res.certificateChain.get(index).expect("The index is out of bounds.").encodedCertificate;
+ if size != 0 {
+ let data = NonNull::new(data).expect("data must not be null when size > 0");
+ // SAFETY: See the requirements on `data` above. The number of bytes copied doesn't exceed
+ // the length of either buffer, and the caller ensures that `certificate` cannot overlap
+ // `data`. We allow data to be null, which is never valid, but only if size == 0
+ // which is checked above.
unsafe {
ptr::copy_nonoverlapping(
certificate.as_ptr(),
- buffer,
+ data.as_ptr(),
std::cmp::min(certificate.len(), size),
- );
- }
+ )
+ };
}
certificate.len()
}
-fn try_request_attestation(challenge: &[u8]) -> Result<Vec<u8>> {
- let certificate = get_vm_payload_service()?
- .requestAttestation(challenge)
- .context("Failed to request attestation")?;
- Ok(certificate)
+/// Frees all the data owned by given attestation result and result itself.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `res` must point to a valid `AttestationResult` and has not been freed before.
+#[no_mangle]
+pub unsafe extern "C" fn AVmAttestationResult_free(res: *mut AttestationResult) {
+ if !res.is_null() {
+ // SAFETY: The result is only freed once is ensured by the caller.
+ let res = unsafe { Box::from_raw(res) };
+ drop(res)
+ }
}
/// Gets the path to the APK contents.
diff --git a/vm_payload/src/lib.rs b/vm_payload/src/lib.rs
index 4d059d1..e305769 100644
--- a/vm_payload/src/lib.rs
+++ b/vm_payload/src/lib.rs
@@ -17,7 +17,9 @@
mod api;
pub use api::{
- AVmPayload_getCertificate, AVmPayload_getDiceAttestationCdi,
- AVmPayload_getDiceAttestationChain, AVmPayload_getVmInstanceSecret,
- AVmPayload_notifyPayloadReady,
+ AVmAttestationResult_free, AVmAttestationResult_getCertificateAt,
+ AVmAttestationResult_getCertificatesCount, AVmAttestationResult_getPrivateKey,
+ AVmAttestationResult_resultToString, AVmAttestationResult_sign,
+ AVmPayload_getDiceAttestationCdi, AVmPayload_getDiceAttestationChain,
+ AVmPayload_getVmInstanceSecret, AVmPayload_notifyPayloadReady, AVmPayload_requestAttestation,
};