Implement simple remote attestion for the UEFI app

Author: Juliette Pretot

experimental/uefi/app/Cargo.lock

@@ -16,6 +16,9 @@ log = { version = "*" }
 ciborium = { version = "*", default-features = false }
 ciborium-io = "*"
 oak_remote_attestation = { path = "../../../remote_attestation/rust" }
+oak_remote_attestation_sessions = { path = "../../../remote_attestation_sessions" }
+lru = "*"
+anyhow = { version = "*", default-features = false }
 
 [dev-dependencies]
 anyhow = { version = "*", default-features = false }

experimental/uefi/app/Cargo.toml

@@ -28,9 +28,11 @@
 extern crate log;
 extern crate alloc;
 
+use crate::remote_attestation_server::AttestationHandler;
 use ciborium::{de, ser};
 use uefi::{prelude::*, table::runtime::ResetType};
 
+mod remote_attestation_server;
 mod serial;
 
 // The main entry point of the UEFI application.
@@ -71,6 +73,8 @@ fn main(handle: Handle, system_table: &mut SystemTable<Boot>) -> Status {
     serial_echo(handle, system_table.boot_services(), ECHO_SERIAL_PORT_INDEX).unwrap();
 }
 
+const MOCK_SESSION_ID: [u8; 8] = [0; 8];
+
 // Opens the index-th serial port on the system and echoes back all frames sent over the serial
 // port.
 //
@@ -85,6 +89,7 @@ fn main(handle: Handle, system_table: &mut SystemTable<Boot>) -> Status {
 //  Normally does not return, unless an error is raised.
 fn serial_echo(handle: Handle, bt: &BootServices, index: usize) -> Result<!, uefi::Error<()>> {
     let mut serial = serial::Serial::get(handle, bt, index)?;
+    let attestation_handler = &mut AttestationHandler::create(|v| v);
     loop {
         let msg: alloc::vec::Vec<u8> = de::from_reader(&mut serial).map_err(|err| match err {
             de::Error::Io(err) => err,
@@ -98,7 +103,8 @@ fn serial_echo(handle: Handle, bt: &BootServices, index: usize) -> Result<!, uef
             }
             de::Error::RecursionLimitExceeded => uefi::Error::from(Status::ABORTED),
         })?;
-        ser::into_writer(&msg, &mut serial).map_err(|err| match err {
+        let response = attestation_handler.message(MOCK_SESSION_ID, msg);
+        ser::into_writer(&response, &mut serial).map_err(|err| match err {
             ser::Error::Io(err) => err,
             ser::Error::Value(msg) => {
                 error!("Error serializing value: {}", msg);

experimental/uefi/app/src/main.rs

@@ -0,0 +1,88 @@
+//
+// Copyright 2022 The Project Oak Authors
+//
+// 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.
+//
+
+//! Server-side implementation of the bidirectional gRPC remote attestation handshake
+//! protocol.
+//!
+//! A simplified version of the implementation from the `grpc_unary_attestation`
+//! crate. TODO(#2741): Refactor this to share more code between the two runtimes.
+
+use alloc::{boxed::Box, sync::Arc, vec::Vec};
+use lru::LruCache;
+use oak_remote_attestation::handshaker::{
+    Encryptor, ServerHandshaker, SessionId, SessionState, SessionTracker,
+};
+
+pub struct AttestationHandler<F> {
+    session_tracker: SessionTracker,
+    request_handler: F,
+}
+
+const MOCK_TEE_CERTIFICATE: [u8; 0] = [];
+const MOCK_ADDITIONAL_INFO: [u8; 0] = [];
+
+impl<F> AttestationHandler<F>
+where
+    F: Send + Sync + Clone + FnOnce(Vec<u8>) -> Vec<u8>,
+{
+    pub fn create(request_handler: F) -> Self {
+        let session_tracker =
+            SessionTracker::create(MOCK_TEE_CERTIFICATE.to_vec(), MOCK_ADDITIONAL_INFO.to_vec());
+
+        Self {
+            session_tracker,
+            request_handler,
+        }
+    }
+
+    pub fn message(&mut self, session_id: SessionId, request: Vec<u8>) -> Vec<u8> {
+        let mut session_state = {
+            self.session_tracker
+                .pop_session_state(session_id)
+                .expect("Couldn't pop session state")
+        };
+        let response_body = match session_state {
+            SessionState::HandshakeInProgress(ref mut handshaker) => {
+                handshaker
+                    .next_step(&request)
+                    .expect("Couldn't process handshake message")
+                    // After receiving a valid `ClientIdentity` message
+                    // (the last step of the key exchange)
+                    // ServerHandshaker.next_step returns `None`. For unary
+                    // request we do want to send an explicit confirmation in
+                    // the form of a status message. Hence in case of `None`
+                    // fallback to a default (empty) response.
+                    .unwrap_or_default()
+            }
+            SessionState::EncryptedMessageExchange(ref mut encryptor) => {
+                let decrypted_request = encryptor
+                    .decrypt(&request)
+                    .expect("Couldn't decrypt response");
+
+                let response = (self.request_handler.clone())(decrypted_request);
+
+                encryptor
+                    .encrypt(&response)
+                    .expect("Couldn't encrypt response")
+            }
+        };
+
+        self.session_tracker
+            .put_session_state(session_id, session_state);
+
+        response_body
+    }
+}

experimental/uefi/app/src/remote_attestation.rs

@@ -71,6 +71,10 @@ impl Qemu {
         // Construct the command-line arguments for `qemu`. See
         // https://www.qemu.org/docs/master/system/invocation.html for all available options.
 
+        // Needed to expose advanced CPU features to the UEFI app. Specifically
+        // RDRAND which is required for remote attestation.
+        cmd.arg("-enable-kvm");
+        cmd.args(&["-cpu", "Broadwell-IBRS"]);
         // We're going to run qemu as a noninteractive embedded program, so disable any
         // graphical outputs.
         cmd.arg("-nographic");