Get CompOS talking to diced

Create a module in compsvc to handle using DICE for signing. Initially
we just expose a method for returning our key's attestation
chain.

Add a method to composd, accessed via compos_cmd, to exercise this
functionality for testing purposes.

Bug: 214233409
Test: composd_cmd dice
Change-Id: I65ef19d0126862b800b6539ae1798b1a433085b8
diff --git a/compos/src/compsvc.rs b/compos/src/compsvc.rs
index 5a2c3ca..28bf5d9 100644
--- a/compos/src/compsvc.rs
+++ b/compos/src/compsvc.rs
@@ -28,6 +28,7 @@
 
 use crate::compilation::{compile_cmd, odrefresh, CompilerOutput, OdrefreshContext};
 use crate::compos_key_service::{CompOsKeyService, Signer};
+use crate::dice::Dice;
 use crate::fsverity;
 use authfs_aidl_interface::aidl::com::android::virt::fs::IAuthFsService::IAuthFsService;
 use compos_aidl_interface::aidl::com::android::compos::{
@@ -79,6 +80,11 @@
             Ok(self.key_service.new_signer(key))
         }
     }
+
+    fn get_boot_certificate_chain(&self) -> Result<Vec<u8>> {
+        let dice = Dice::new()?;
+        dice.get_boot_certificate_chain()
+    }
 }
 
 impl Interface for CompOsService {}
@@ -164,6 +170,10 @@
             true
         })
     }
+
+    fn getBootCertificateChain(&self) -> BinderResult<Vec<u8>> {
+        to_binder_result(self.get_boot_certificate_chain())
+    }
 }
 
 fn get_authfs_service() -> BinderResult<Strong<dyn IAuthFsService>> {
diff --git a/compos/src/compsvc_main.rs b/compos/src/compsvc_main.rs
index 9347905..b4e3128 100644
--- a/compos/src/compsvc_main.rs
+++ b/compos/src/compsvc_main.rs
@@ -20,6 +20,7 @@
 mod compilation;
 mod compos_key_service;
 mod compsvc;
+mod dice;
 mod fsverity;
 
 use android_system_virtualmachineservice::{
diff --git a/compos/src/dice.rs b/compos/src/dice.rs
new file mode 100644
index 0000000..22a7ee2
--- /dev/null
+++ b/compos/src/dice.rs
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2022 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.
+ */
+
+//! Handles the use of DICE as the source of our unique signing key via diced / IDiceNode.
+
+use android_security_dice::aidl::android::security::dice::IDiceNode::IDiceNode;
+use android_security_dice::binder::{wait_for_interface, Strong};
+use anyhow::{Context, Result};
+
+pub struct Dice {
+    node: Strong<dyn IDiceNode>,
+}
+
+impl Dice {
+    pub fn new() -> Result<Self> {
+        let dice_service = wait_for_interface::<dyn IDiceNode>("android.security.dice.IDiceNode")
+            .context("No IDiceNode service")?;
+        Ok(Self { node: dice_service })
+    }
+
+    pub fn get_boot_certificate_chain(&self) -> Result<Vec<u8>> {
+        let input_values = []; // Get our BCC, not a child's
+        let bcc = self
+            .node
+            .getAttestationChain(&input_values)
+            .context("Getting attestation chain failed")?;
+        Ok(bcc.data)
+    }
+}