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// Copyright 2021, 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.
//! Implements get_attestation_key_info which loads remote provisioned or user
//! generated attestation keys.
use crate::database::{BlobMetaData, KeyEntryLoadBits, KeyType};
use crate::database::{KeyIdGuard, KeystoreDB};
use crate::error::{Error, ErrorCode};
use crate::permission::KeyPerm;
use crate::remote_provisioning::RemProvState;
use crate::utils::check_key_permission;
use android_hardware_security_keymint::aidl::android::hardware::security::keymint::{
AttestationKey::AttestationKey, Certificate::Certificate, KeyParameter::KeyParameter, Tag::Tag,
};
use android_system_keystore2::aidl::android::system::keystore2::{
Domain::Domain, KeyDescriptor::KeyDescriptor,
};
use anyhow::{Context, Result};
use keystore2_crypto::parse_subject_from_certificate;
/// KeyMint takes two different kinds of attestation keys. Remote provisioned keys
/// and those that have been generated by the user. Unfortunately, they need to be
/// handled quite differently, thus the different representations.
pub enum AttestationKeyInfo {
RemoteProvisioned {
key_id_guard: KeyIdGuard,
attestation_key: AttestationKey,
attestation_certs: Certificate,
},
UserGenerated {
key_id_guard: KeyIdGuard,
blob: Vec<u8>,
blob_metadata: BlobMetaData,
issuer_subject: Vec<u8>,
},
}
/// This function loads and, optionally, assigns the caller's remote provisioned
/// attestation key if a challenge is present. Alternatively, if `attest_key_descriptor` is given,
/// it loads the user generated attestation key from the database.
pub fn get_attest_key_info(
key: &KeyDescriptor,
caller_uid: u32,
attest_key_descriptor: Option<&KeyDescriptor>,
params: &[KeyParameter],
rem_prov_state: &RemProvState,
db: &mut KeystoreDB,
) -> Result<Option<AttestationKeyInfo>> {
let challenge_present = params.iter().any(|kp| kp.tag == Tag::ATTESTATION_CHALLENGE);
match attest_key_descriptor {
None if challenge_present => rem_prov_state
.get_remotely_provisioned_attestation_key_and_certs(&key, caller_uid, params, db)
.context(concat!(
"In get_attest_key_and_cert_chain: ",
"Trying to get remotely provisioned attestation key."
))
.map(|result| {
result.map(|(key_id_guard, attestation_key, attestation_certs)| {
AttestationKeyInfo::RemoteProvisioned {
key_id_guard,
attestation_key,
attestation_certs,
}
})
}),
None => Ok(None),
Some(attest_key) => get_user_generated_attestation_key(&attest_key, caller_uid, db)
.context("In get_attest_key_and_cert_chain: Trying to load attest key")
.map(Some),
}
}
fn get_user_generated_attestation_key(
key: &KeyDescriptor,
caller_uid: u32,
db: &mut KeystoreDB,
) -> Result<AttestationKeyInfo> {
let (key_id_guard, blob, cert, blob_metadata) =
load_attest_key_blob_and_cert(&key, caller_uid, db)
.context("In get_user_generated_attestation_key: Failed to load blob and cert")?;
let issuer_subject: Vec<u8> = parse_subject_from_certificate(&cert).context(
"In get_user_generated_attestation_key: Failed to parse subject from certificate.",
)?;
Ok(AttestationKeyInfo::UserGenerated { key_id_guard, blob, issuer_subject, blob_metadata })
}
fn load_attest_key_blob_and_cert(
key: &KeyDescriptor,
caller_uid: u32,
db: &mut KeystoreDB,
) -> Result<(KeyIdGuard, Vec<u8>, Vec<u8>, BlobMetaData)> {
match key.domain {
Domain::BLOB => Err(Error::Km(ErrorCode::INVALID_ARGUMENT)).context(
"In load_attest_key_blob_and_cert: Domain::BLOB attestation keys not supported",
),
_ => {
let (key_id_guard, mut key_entry) = db
.load_key_entry(
&key,
KeyType::Client,
KeyEntryLoadBits::BOTH,
caller_uid,
|k, av| check_key_permission(KeyPerm::use_(), k, &av),
)
.context("In load_attest_key_blob_and_cert: Failed to load key.")?;
let (blob, blob_metadata) =
key_entry.take_key_blob_info().ok_or_else(Error::sys).context(concat!(
"In load_attest_key_blob_and_cert: Successfully loaded key entry,",
" but KM blob was missing."
))?;
let cert = key_entry.take_cert().ok_or_else(Error::sys).context(concat!(
"In load_attest_key_blob_and_cert: Successfully loaded key entry,",
" but cert was missing."
))?;
Ok((key_id_guard, blob, cert, blob_metadata))
}
}
}
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