1 // Copyright 2021, The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 //! Implements get_attestation_key_info which loads remote provisioned or user
16 //! generated attestation keys.
17
18 use crate::database::{BlobMetaData, KeyEntryLoadBits, KeyType};
19 use crate::database::{KeyIdGuard, KeystoreDB};
20 use crate::error::{Error, ErrorCode};
21 use crate::ks_err;
22 use crate::permission::KeyPerm;
23 use crate::remote_provisioning::RemProvState;
24 use crate::utils::check_key_permission;
25 use android_hardware_security_keymint::aidl::android::hardware::security::keymint::{
26 AttestationKey::AttestationKey, Certificate::Certificate, KeyParameter::KeyParameter, Tag::Tag,
27 };
28 use android_system_keystore2::aidl::android::system::keystore2::{
29 Domain::Domain, KeyDescriptor::KeyDescriptor, ResponseCode::ResponseCode,
30 };
31 use anyhow::{Context, Result};
32 use keystore2_crypto::parse_subject_from_certificate;
33
34 /// KeyMint takes two different kinds of attestation keys. Remote provisioned keys
35 /// and those that have been generated by the user. Unfortunately, they need to be
36 /// handled quite differently, thus the different representations.
37 pub enum AttestationKeyInfo {
38 RkpdProvisioned {
39 attestation_key: AttestationKey,
40 attestation_certs: Certificate,
41 },
42 UserGenerated {
43 key_id_guard: KeyIdGuard,
44 blob: Vec<u8>,
45 blob_metadata: BlobMetaData,
46 issuer_subject: Vec<u8>,
47 },
48 }
49
50 /// This function loads and, optionally, assigns the caller's remote provisioned
51 /// attestation key if a challenge is present. Alternatively, if `attest_key_descriptor` is given,
52 /// it loads the user generated attestation key from the database.
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>>53 pub fn get_attest_key_info(
54 key: &KeyDescriptor,
55 caller_uid: u32,
56 attest_key_descriptor: Option<&KeyDescriptor>,
57 params: &[KeyParameter],
58 rem_prov_state: &RemProvState,
59 db: &mut KeystoreDB,
60 ) -> Result<Option<AttestationKeyInfo>> {
61 let challenge_present = params.iter().any(|kp| kp.tag == Tag::ATTESTATION_CHALLENGE);
62 let is_device_unique_attestation =
63 params.iter().any(|kp| kp.tag == Tag::DEVICE_UNIQUE_ATTESTATION);
64 match attest_key_descriptor {
65 // Do not select an RKP key if DEVICE_UNIQUE_ATTESTATION is present.
66 None if challenge_present && !is_device_unique_attestation => rem_prov_state
67 .get_rkpd_attestation_key_and_certs(key, caller_uid, params)
68 .context(ks_err!("Trying to get attestation key from RKPD."))
69 .map(|result| {
70 result.map(|(attestation_key, attestation_certs)| {
71 AttestationKeyInfo::RkpdProvisioned { attestation_key, attestation_certs }
72 })
73 }),
74 None => Ok(None),
75 Some(attest_key) => get_user_generated_attestation_key(attest_key, caller_uid, db)
76 .context(ks_err!("Trying to load attest key"))
77 .map(Some),
78 }
79 }
80
get_user_generated_attestation_key( key: &KeyDescriptor, caller_uid: u32, db: &mut KeystoreDB, ) -> Result<AttestationKeyInfo>81 fn get_user_generated_attestation_key(
82 key: &KeyDescriptor,
83 caller_uid: u32,
84 db: &mut KeystoreDB,
85 ) -> Result<AttestationKeyInfo> {
86 let (key_id_guard, blob, cert, blob_metadata) =
87 load_attest_key_blob_and_cert(key, caller_uid, db)
88 .context(ks_err!("Failed to load blob and cert"))?;
89
90 let issuer_subject: Vec<u8> = parse_subject_from_certificate(&cert)
91 .context(ks_err!("Failed to parse subject from certificate"))?;
92
93 Ok(AttestationKeyInfo::UserGenerated { key_id_guard, blob, issuer_subject, blob_metadata })
94 }
95
load_attest_key_blob_and_cert( key: &KeyDescriptor, caller_uid: u32, db: &mut KeystoreDB, ) -> Result<(KeyIdGuard, Vec<u8>, Vec<u8>, BlobMetaData)>96 fn load_attest_key_blob_and_cert(
97 key: &KeyDescriptor,
98 caller_uid: u32,
99 db: &mut KeystoreDB,
100 ) -> Result<(KeyIdGuard, Vec<u8>, Vec<u8>, BlobMetaData)> {
101 match key.domain {
102 Domain::BLOB => Err(Error::Km(ErrorCode::INVALID_ARGUMENT))
103 .context(ks_err!("Domain::BLOB attestation keys not supported")),
104 _ => {
105 let (key_id_guard, mut key_entry) = db
106 .load_key_entry(
107 key,
108 KeyType::Client,
109 KeyEntryLoadBits::BOTH,
110 caller_uid,
111 |k, av| check_key_permission(KeyPerm::Use, k, &av),
112 )
113 .context(ks_err!("Failed to load key."))?;
114
115 let (blob, blob_metadata) = key_entry
116 .take_key_blob_info()
117 .ok_or(Error::Rc(ResponseCode::INVALID_ARGUMENT))
118 .context(ks_err!("Successfully loaded key entry, but KM blob was missing"))?;
119 let cert = key_entry
120 .take_cert()
121 .ok_or(Error::Rc(ResponseCode::INVALID_ARGUMENT))
122 .context(ks_err!("Successfully loaded key entry, but cert was missing"))?;
123 Ok((key_id_guard, blob, cert, blob_metadata))
124 }
125 }
126 }
127