1 /*
2  * Copyright 2015 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 <keymaster/km_openssl/hmac.h>
18 
19 #include <assert.h>
20 
21 #include <openssl/evp.h>
22 #include <openssl/hmac.h>
23 #include <openssl/mem.h>
24 #include <openssl/sha.h>
25 
26 #include <keymaster/android_keymaster_utils.h>
27 
28 namespace keymaster {
29 
30 size_t HmacSha256::DigestLength() const {
31     return SHA256_DIGEST_LENGTH;
32 }
33 
34 bool HmacSha256::Init(const Buffer& key) {
35     return Init(key.peek_read(), key.available_read());
36 }
37 
38 bool HmacSha256::Init(const uint8_t* key, size_t key_len) {
39     if (!key)
40         return false;
41 
42     key_len_ = key_len;
43     key_.reset(dup_buffer(key, key_len));
44     if (!key_.get()) {
45         return false;
46     }
47     return true;
48 }
49 
50 bool HmacSha256::Sign(const Buffer& data, uint8_t* out_digest, size_t digest_len) const {
51     return Sign(data.peek_read(), data.available_read(), out_digest, digest_len);
52 }
53 
54 bool HmacSha256::Sign(const uint8_t* data, size_t data_len, uint8_t* out_digest,
55                       size_t digest_len) const {
56     assert(digest_len);
57 
58     uint8_t tmp[SHA256_DIGEST_LENGTH];
59     uint8_t* digest = tmp;
60     if (digest_len >= SHA256_DIGEST_LENGTH)
61         digest = out_digest;
62 
63     if (nullptr == ::HMAC(EVP_sha256(), key_.get(), key_len_, data, data_len, digest, nullptr)) {
64         return false;
65     }
66     if (digest_len < SHA256_DIGEST_LENGTH)
67         memcpy(out_digest, tmp, digest_len);
68 
69     return true;
70 }
71 
72 bool HmacSha256::Verify(const Buffer& data, const Buffer& digest) const {
73     return Verify(data.peek_read(), data.available_read(), digest.peek_read(),
74                   digest.available_read());
75 }
76 
77 bool HmacSha256::Verify(const uint8_t* data, size_t data_len, const uint8_t* digest,
78                         size_t digest_len) const {
79     if (digest_len != SHA256_DIGEST_LENGTH)
80         return false;
81 
82     uint8_t computed_digest[SHA256_DIGEST_LENGTH];
83     if (!Sign(data, data_len, computed_digest, sizeof(computed_digest)))
84         return false;
85 
86     return 0 == CRYPTO_memcmp(digest, computed_digest, SHA256_DIGEST_LENGTH);
87 }
88 
89 }  // namespace keymaster
90