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
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
|
/*
* Copyright 2015 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.
*/
#include "integrity_assured_key_blob.h"
#include <assert.h>
#include <new>
#include <openssl/hmac.h>
#include <openssl/mem.h>
#include <keymaster/android_keymaster_utils.h>
#include <keymaster/authorization_set.h>
#include "openssl_err.h"
namespace keymaster {
static const uint8_t BLOB_VERSION = 0;
static const size_t HMAC_SIZE = 8;
static const char HMAC_KEY[] = "IntegrityAssuredBlob0";
inline size_t min(size_t a, size_t b) {
if (a < b)
return a;
return b;
}
class HmacCleanup {
public:
HmacCleanup(HMAC_CTX* ctx) : ctx_(ctx) {}
~HmacCleanup() { HMAC_CTX_cleanup(ctx_); }
private:
HMAC_CTX* ctx_;
};
static keymaster_error_t ComputeHmac(const uint8_t* serialized_data, size_t serialized_data_size,
const AuthorizationSet& hidden, uint8_t hmac[HMAC_SIZE]) {
size_t hidden_bytes_size = hidden.SerializedSize();
UniquePtr<uint8_t[]> hidden_bytes(new (std::nothrow) uint8_t[hidden_bytes_size]);
if (!hidden_bytes.get())
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
hidden.Serialize(hidden_bytes.get(), hidden_bytes.get() + hidden_bytes_size);
HMAC_CTX ctx;
HMAC_CTX_init(&ctx);
const EVP_MD* md = EVP_sha256();
if (!HMAC_Init_ex(&ctx, HMAC_KEY, sizeof(HMAC_KEY), md, NULL /* engine */))
return TranslateLastOpenSslError();
HmacCleanup cleanup(&ctx);
uint8_t tmp[EVP_MAX_MD_SIZE];
unsigned tmp_len;
if (!HMAC_Update(&ctx, serialized_data, serialized_data_size) ||
!HMAC_Update(&ctx, hidden_bytes.get(), hidden_bytes_size) || //
!HMAC_Final(&ctx, tmp, &tmp_len))
return TranslateLastOpenSslError();
assert(tmp_len >= HMAC_SIZE);
memcpy(hmac, tmp, min(HMAC_SIZE, tmp_len));
return KM_ERROR_OK;
}
keymaster_error_t SerializeIntegrityAssuredBlob(const KeymasterKeyBlob& key_material,
const AuthorizationSet& hidden,
const AuthorizationSet& hw_enforced,
const AuthorizationSet& sw_enforced,
KeymasterKeyBlob* key_blob) {
size_t size = 1 /* version */ + //
key_material.SerializedSize() + //
hw_enforced.SerializedSize() + //
sw_enforced.SerializedSize() + //
HMAC_SIZE;
if (!key_blob->Reset(size))
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
uint8_t* p = key_blob->writable_data();
*p++ = BLOB_VERSION;
p = key_material.Serialize(p, key_blob->end());
p = hw_enforced.Serialize(p, key_blob->end());
p = sw_enforced.Serialize(p, key_blob->end());
return ComputeHmac(key_blob->key_material, p - key_blob->key_material, hidden, p);
}
keymaster_error_t DeserializeIntegrityAssuredBlob(const KeymasterKeyBlob& key_blob,
const AuthorizationSet& hidden,
KeymasterKeyBlob* key_material,
AuthorizationSet* hw_enforced,
AuthorizationSet* sw_enforced) {
const uint8_t* p = key_blob.begin();
const uint8_t* end = key_blob.end();
if (p > end || p + HMAC_SIZE > end)
return KM_ERROR_INVALID_KEY_BLOB;
uint8_t computed_hmac[HMAC_SIZE];
keymaster_error_t error = ComputeHmac(key_blob.begin(), key_blob.key_material_size - HMAC_SIZE,
hidden, computed_hmac);
if (error != KM_ERROR_OK)
return error;
if (CRYPTO_memcmp(key_blob.end() - HMAC_SIZE, computed_hmac, HMAC_SIZE) != 0)
return KM_ERROR_INVALID_KEY_BLOB;
if (*p != BLOB_VERSION)
return KM_ERROR_INVALID_KEY_BLOB;
++p;
if (!key_material->Deserialize(&p, end) || //
!hw_enforced->Deserialize(&p, end) || //
!sw_enforced->Deserialize(&p, end))
return KM_ERROR_INVALID_KEY_BLOB;
return KM_ERROR_OK;
}
} // namespace keymaster;
|
