1 /*
2  * Copyright (C) 2012 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include <stdint.h>
18 #include <string.h>
19 #include <sys/types.h>
20 #include <unistd.h>
21 
22 #include <keystore/keystore.h>
23 
24 /**
25  * When a key is being migrated from a software keymaster implementation
26  * to a hardware keymaster implementation, the first 4 bytes of the key_blob
27  * given to the hardware implementation will be equal to SOFT_KEY_MAGIC.
28  * The hardware implementation should import these PKCS#8 format keys which
29  * are encoded like this:
30  *
31  * 4-byte SOFT_KEY_MAGIC
32  *
33  * 4-byte 32-bit integer big endian for public_key_length. This may be zero
34  *     length which indicates the public key should be derived from the
35  *     private key.
36  *
37  * public_key_length bytes of public key (may be empty)
38  *
39  * 4-byte 32-bit integer big endian for private_key_length
40  *
41  * private_key_length bytes of private key
42  */
43 static const uint8_t SOFT_KEY_MAGIC[] = { 'P', 'K', '#', '8' };
44 
45 size_t get_softkey_header_size() {
46     return sizeof(SOFT_KEY_MAGIC);
47 }
48 
49 uint8_t* add_softkey_header(uint8_t* key_blob, size_t key_blob_length) {
50     if (key_blob_length < sizeof(SOFT_KEY_MAGIC)) {
51         return NULL;
52     }
53 
54     memcpy(key_blob, SOFT_KEY_MAGIC, sizeof(SOFT_KEY_MAGIC));
55 
56     return key_blob + sizeof(SOFT_KEY_MAGIC);
57 }
58 
59 bool is_softkey(const uint8_t* key_blob, const size_t key_blob_length) {
60     if (key_blob_length < sizeof(SOFT_KEY_MAGIC)) {
61         return false;
62     }
63 
64     return !memcmp(key_blob, SOFT_KEY_MAGIC, sizeof(SOFT_KEY_MAGIC));
65 }
66