| // 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. |
| |
| //! This module handles the pvmfw payload verification. |
| |
| use crate::descriptor::{Descriptors, Digest}; |
| use crate::ops::{Ops, Payload}; |
| use crate::partition::PartitionName; |
| use crate::PvmfwVerifyError; |
| use alloc::vec; |
| use alloc::vec::Vec; |
| use avb_bindgen::{AvbPartitionData, AvbVBMetaData}; |
| use core::ffi::c_char; |
| |
| // We use this for the rollback_index field if AvbSlotVerifyDataWrap has empty rollback_indexes |
| const DEFAULT_ROLLBACK_INDEX: u64 = 0; |
| |
| /// Verified data returned when the payload verification succeeds. |
| #[derive(Debug, PartialEq, Eq)] |
| pub struct VerifiedBootData<'a> { |
| /// DebugLevel of the VM. |
| pub debug_level: DebugLevel, |
| /// Kernel digest. |
| pub kernel_digest: Digest, |
| /// Initrd digest if initrd exists. |
| pub initrd_digest: Option<Digest>, |
| /// Trusted public key. |
| pub public_key: &'a [u8], |
| /// VM capabilities. |
| pub capabilities: Vec<Capability>, |
| /// Rollback index of kernel. |
| pub rollback_index: u64, |
| } |
| |
| impl VerifiedBootData<'_> { |
| /// Returns whether the kernel have the given capability |
| pub fn has_capability(&self, cap: Capability) -> bool { |
| self.capabilities.contains(&cap) |
| } |
| } |
| |
| /// This enum corresponds to the `DebugLevel` in `VirtualMachineConfig`. |
| #[derive(Clone, Copy, Debug, PartialEq, Eq)] |
| pub enum DebugLevel { |
| /// Not debuggable at all. |
| None, |
| /// Fully debuggable. |
| Full, |
| } |
| |
| /// VM Capability. |
| #[derive(Copy, Clone, Debug, PartialEq, Eq)] |
| pub enum Capability { |
| /// Remote attestation. |
| RemoteAttest, |
| /// Secretkeeper protected secrets. |
| SecretkeeperProtection, |
| } |
| |
| impl Capability { |
| const KEY: &[u8] = b"com.android.virt.cap"; |
| const REMOTE_ATTEST: &[u8] = b"remote_attest"; |
| const SECRETKEEPER_PROTECTION: &[u8] = b"secretkeeper_protection"; |
| const SEPARATOR: u8 = b'|'; |
| |
| fn get_capabilities(property_value: &[u8]) -> Result<Vec<Self>, PvmfwVerifyError> { |
| let mut res = Vec::new(); |
| |
| for v in property_value.split(|b| *b == Self::SEPARATOR) { |
| let cap = match v { |
| Self::REMOTE_ATTEST => Self::RemoteAttest, |
| Self::SECRETKEEPER_PROTECTION => Self::SecretkeeperProtection, |
| _ => return Err(PvmfwVerifyError::UnknownVbmetaProperty), |
| }; |
| if res.contains(&cap) { |
| return Err(avb::SlotVerifyError::InvalidMetadata.into()); |
| } |
| res.push(cap); |
| } |
| Ok(res) |
| } |
| } |
| |
| fn verify_only_one_vbmeta_exists( |
| vbmeta_images: &[AvbVBMetaData], |
| ) -> Result<(), avb::SlotVerifyError> { |
| if vbmeta_images.len() == 1 { |
| Ok(()) |
| } else { |
| Err(avb::SlotVerifyError::InvalidMetadata) |
| } |
| } |
| |
| fn verify_vbmeta_is_from_kernel_partition( |
| vbmeta_image: &AvbVBMetaData, |
| ) -> Result<(), avb::SlotVerifyError> { |
| match (vbmeta_image.partition_name as *const c_char).try_into() { |
| Ok(PartitionName::Kernel) => Ok(()), |
| _ => Err(avb::SlotVerifyError::InvalidMetadata), |
| } |
| } |
| |
| fn verify_vbmeta_has_only_one_hash_descriptor( |
| descriptors: &Descriptors, |
| ) -> Result<(), avb::SlotVerifyError> { |
| if descriptors.num_hash_descriptor() == 1 { |
| Ok(()) |
| } else { |
| Err(avb::SlotVerifyError::InvalidMetadata) |
| } |
| } |
| |
| fn verify_loaded_partition_has_expected_length( |
| loaded_partitions: &[AvbPartitionData], |
| partition_name: PartitionName, |
| expected_len: usize, |
| ) -> Result<(), avb::SlotVerifyError> { |
| if loaded_partitions.len() != 1 { |
| // Only one partition should be loaded in each verify result. |
| return Err(avb::SlotVerifyError::Io); |
| } |
| let loaded_partition = loaded_partitions[0]; |
| if !PartitionName::try_from(loaded_partition.partition_name as *const c_char) |
| .map_or(false, |p| p == partition_name) |
| { |
| // Only the requested partition should be loaded. |
| return Err(avb::SlotVerifyError::Io); |
| } |
| if loaded_partition.data_size == expected_len { |
| Ok(()) |
| } else { |
| Err(avb::SlotVerifyError::Verification) |
| } |
| } |
| |
| /// Verifies that the vbmeta contains at most one property descriptor and it indicates the |
| /// vm type is service VM. |
| fn verify_property_and_get_capabilities( |
| descriptors: &Descriptors, |
| ) -> Result<Vec<Capability>, PvmfwVerifyError> { |
| if !descriptors.has_property_descriptor() { |
| return Ok(vec![]); |
| } |
| descriptors |
| .find_property_value(Capability::KEY) |
| .ok_or(PvmfwVerifyError::UnknownVbmetaProperty) |
| .and_then(Capability::get_capabilities) |
| } |
| |
| /// Verifies the payload (signed kernel + initrd) against the trusted public key. |
| pub fn verify_payload<'a>( |
| kernel: &[u8], |
| initrd: Option<&[u8]>, |
| trusted_public_key: &'a [u8], |
| ) -> Result<VerifiedBootData<'a>, PvmfwVerifyError> { |
| let mut payload = Payload::new(kernel, initrd, trusted_public_key); |
| let mut ops = Ops::from(&mut payload); |
| let kernel_verify_result = ops.verify_partition(PartitionName::Kernel.as_cstr())?; |
| |
| let vbmeta_images = kernel_verify_result.vbmeta_images()?; |
| // TODO(b/302093437): Use explicit rollback_index_location instead of default |
| // location (first element). |
| let rollback_index = |
| *kernel_verify_result.rollback_indexes().first().unwrap_or(&DEFAULT_ROLLBACK_INDEX); |
| verify_only_one_vbmeta_exists(vbmeta_images)?; |
| let vbmeta_image = vbmeta_images[0]; |
| verify_vbmeta_is_from_kernel_partition(&vbmeta_image)?; |
| // SAFETY: It is safe because the `vbmeta_image` is collected from `AvbSlotVerifyData`, |
| // which is returned by `avb_slot_verify()` when the verification succeeds. It is |
| // guaranteed by libavb to be non-null and to point to a valid VBMeta structure. |
| let descriptors = unsafe { Descriptors::from_vbmeta(vbmeta_image)? }; |
| let capabilities = verify_property_and_get_capabilities(&descriptors)?; |
| let kernel_descriptor = descriptors.find_hash_descriptor(PartitionName::Kernel)?; |
| |
| if initrd.is_none() { |
| verify_vbmeta_has_only_one_hash_descriptor(&descriptors)?; |
| return Ok(VerifiedBootData { |
| debug_level: DebugLevel::None, |
| kernel_digest: *kernel_descriptor.digest, |
| initrd_digest: None, |
| public_key: trusted_public_key, |
| capabilities, |
| rollback_index, |
| }); |
| } |
| |
| let initrd = initrd.unwrap(); |
| let (debug_level, initrd_verify_result, initrd_partition_name) = |
| if let Ok(result) = ops.verify_partition(PartitionName::InitrdNormal.as_cstr()) { |
| (DebugLevel::None, result, PartitionName::InitrdNormal) |
| } else if let Ok(result) = ops.verify_partition(PartitionName::InitrdDebug.as_cstr()) { |
| (DebugLevel::Full, result, PartitionName::InitrdDebug) |
| } else { |
| return Err(avb::SlotVerifyError::Verification.into()); |
| }; |
| let loaded_partitions = initrd_verify_result.loaded_partitions()?; |
| verify_loaded_partition_has_expected_length( |
| loaded_partitions, |
| initrd_partition_name, |
| initrd.len(), |
| )?; |
| let initrd_descriptor = descriptors.find_hash_descriptor(initrd_partition_name)?; |
| Ok(VerifiedBootData { |
| debug_level, |
| kernel_digest: *kernel_descriptor.digest, |
| initrd_digest: Some(*initrd_descriptor.digest), |
| public_key: trusted_public_key, |
| capabilities, |
| rollback_index, |
| }) |
| } |