1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
|
// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <jni.h>
#include "base/android/jni_array.h"
#include "components/cbor/reader.h"
#include "components/webauthn/android/jni_headers/Fido2Api_jni.h"
#include "device/fido/attested_credential_data.h"
#include "device/fido/public_key.h"
#include "third_party/boringssl/src/include/openssl/bytestring.h"
using base::android::ScopedJavaLocalRef;
using base::android::ToJavaByteArray;
namespace webauthn {
// Parses a CTAP2 attestation[1] and extracts the
// parts that the browser provides via Javascript API [2]. Called
// Fido2Api.java when constructing the makeCredential reply.
//
// [1] https://www.w3.org/TR/webauthn/#attestation-object
// [2] https://w3c.github.io/webauthn/#sctn-public-key-easy
static jboolean JNI_Fido2Api_ParseAttestationObject(
JNIEnv* env,
const base::android::JavaParamRef<jbyteArray>& jattestation_object_bytes,
const base::android::JavaParamRef<jobject>& out_result) {
std::vector<uint8_t> attestation_object_bytes;
JavaByteArrayToByteVector(env, jattestation_object_bytes,
&attestation_object_bytes);
absl::optional<cbor::Value> attestation_object =
cbor::Reader::Read(attestation_object_bytes);
if (!attestation_object || !attestation_object->is_map()) {
return false;
}
const cbor::Value::MapValue& map = attestation_object->GetMap();
// See https://www.w3.org/TR/webauthn/#generating-an-attestation-object
cbor::Value::MapValue::const_iterator it = map.find(cbor::Value("authData"));
if (it == map.end() || !it->second.is_bytestring()) {
return false;
}
const std::vector<uint8_t>& auth_data = it->second.GetBytestring();
// See https://www.w3.org/TR/webauthn/#sec-authenticator-data
CBS cbs;
CBS_init(&cbs, auth_data.data(), auth_data.size());
uint8_t flags;
if ( // RP ID hash.
!CBS_skip(&cbs, 32) || !CBS_get_u8(&cbs, &flags) ||
// Check AT flag is set.
((flags >> 6) & 1) == 0 ||
// Signature counter.
!CBS_skip(&cbs, 4)) {
return false;
}
const auto result = device::AttestedCredentialData::ConsumeFromCtapResponse(
base::span<const uint8_t>(CBS_data(&cbs), CBS_len(&cbs)));
if (!result) {
return false;
}
ScopedJavaLocalRef<jbyteArray> auth_data_java(
ToJavaByteArray(env, auth_data));
const device::PublicKey* pub_key = result->first.public_key();
const absl::optional<std::vector<uint8_t>>& der_bytes(pub_key->der_bytes);
ScopedJavaLocalRef<jbyteArray> spki_java;
if (der_bytes) {
spki_java.Reset(ToJavaByteArray(env, *der_bytes));
}
Java_AttestationObjectParts_setAll(env, out_result, auth_data_java, spki_java,
pub_key->algorithm);
return true;
}
} // namespace webauthn
|
