Add Ciborium to pvmfw
Import Ciborium to enable us to validate & manipulate the BCC CBOR.
Initially we do very minimal verification, just to prove that we can
call into the crate.
Bug: 266172411
Test: atest MicrodroidTests
Change-Id: Iaa78f9fc4f9b5c32e26c54eafc45bf5b29046f1e
diff --git a/pvmfw/Android.bp b/pvmfw/Android.bp
index 7ea1189..0ae2203 100644
--- a/pvmfw/Android.bp
+++ b/pvmfw/Android.bp
@@ -17,6 +17,8 @@
"libaarch64_paging",
"libbssl_ffi_nostd",
"libbuddy_system_allocator",
+ "libciborium_nostd",
+ "libciborium_io_nostd",
"libdiced_open_dice_nostd",
"libfdtpci",
"libhyp",
diff --git a/pvmfw/src/main.rs b/pvmfw/src/main.rs
index a773f1a..1c22861 100644
--- a/pvmfw/src/main.rs
+++ b/pvmfw/src/main.rs
@@ -37,6 +37,7 @@
mod virtio;
use alloc::boxed::Box;
+use alloc::string::ToString;
use crate::dice::PartialInputs;
use crate::entry::RebootReason;
@@ -46,6 +47,7 @@
use crate::instance::get_or_generate_instance_salt;
use crate::memory::MemoryTracker;
use crate::virtio::pci;
+use ciborium::{de::from_reader, value::Value};
use diced_open_dice::bcc_handover_main_flow;
use diced_open_dice::bcc_handover_parse;
use diced_open_dice::DiceArtifacts;
@@ -58,6 +60,19 @@
const NEXT_BCC_SIZE: usize = GUEST_PAGE_SIZE;
+type CiboriumError = ciborium::de::Error<ciborium_io::EndOfFile>;
+
+/// Decodes the provided binary CBOR-encoded value and returns a
+/// ciborium::Value struct wrapped in Result.
+fn value_from_bytes(mut bytes: &[u8]) -> Result<Value, CiboriumError> {
+ let value = from_reader(&mut bytes)?;
+ // Ciborium tries to read one Value, but doesn't care if there is trailing data. We do.
+ if !bytes.is_empty() {
+ return Err(CiboriumError::Semantic(Some(0), "unexpected trailing data".to_string()));
+ }
+ Ok(value)
+}
+
fn main(
fdt: &mut Fdt,
signed_kernel: &[u8],
@@ -81,6 +96,18 @@
})?;
trace!("BCC: {bcc_handover:x?}");
+ // Minimal BCC verification - check the BCC exists & is valid CBOR.
+ // TODO(alanstokes): Do something more useful.
+ if let Some(bytes) = bcc_handover.bcc() {
+ let _ = value_from_bytes(bytes).map_err(|e| {
+ error!("Invalid BCC: {e:?}");
+ RebootReason::InvalidBcc
+ })?;
+ } else {
+ error!("Missing BCC");
+ return Err(RebootReason::InvalidBcc);
+ }
+
// Set up PCI bus for VirtIO devices.
let pci_info = PciInfo::from_fdt(fdt).map_err(handle_pci_error)?;
debug!("PCI: {:#x?}", pci_info);