hmac_operation.cpp revision a550fba3d26d878873956f128de7607ff4cc96e4 
1/*
2 * Copyright 2014 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 "hmac_operation.h"
18
19#include <openssl/evp.h>
20#include <openssl/hmac.h>
21
22#if defined(OPENSSL_IS_BORINGSSL)
23typedef size_t openssl_size_t;
24#else
25typedef int openssl_size_t;
26#endif
27
28namespace keymaster {
29
30HmacOperation::HmacOperation(keymaster_purpose_t purpose, const Logger& logger,
31                             const uint8_t* key_data, size_t key_data_size,
32                             keymaster_digest_t digest, size_t tag_length)
33    : Operation(purpose, logger), error_(KM_ERROR_OK), tag_length_(tag_length) {
34    // Initialize CTX first, so dtor won't crash even if we error out later.
35    HMAC_CTX_init(&ctx_);
36
37    const EVP_MD* md;
38    switch (digest) {
39    case KM_DIGEST_SHA_2_224:
40        md = EVP_sha224();
41        break;
42    case KM_DIGEST_SHA_2_256:
43        md = EVP_sha256();
44        break;
45    case KM_DIGEST_SHA_2_384:
46        md = EVP_sha384();
47        break;
48    case KM_DIGEST_SHA_2_512:
49        md = EVP_sha512();
50        break;
51    default:
52        error_ = KM_ERROR_UNSUPPORTED_DIGEST;
53        return;
54    }
55
56    if ((openssl_size_t)tag_length_ > EVP_MD_size(md)) {
57        error_ = KM_ERROR_UNSUPPORTED_MAC_LENGTH;
58        return;
59    }
60
61    HMAC_Init_ex(&ctx_, key_data, key_data_size, md, NULL /* engine */);
62}
63
64HmacOperation::~HmacOperation() {
65    HMAC_CTX_cleanup(&ctx_);
66}
67
68keymaster_error_t HmacOperation::Begin() {
69    return error_;
70}
71
72keymaster_error_t HmacOperation::Update(const Buffer& input, Buffer* /* output */,
73                                        size_t* input_consumed) {
74    if (!HMAC_Update(&ctx_, input.peek_read(), input.available_read()))
75        return KM_ERROR_UNKNOWN_ERROR;
76    *input_consumed = input.available_read();
77    return KM_ERROR_OK;
78}
79
80keymaster_error_t HmacOperation::Abort() {
81    return KM_ERROR_OK;
82}
83
84keymaster_error_t HmacOperation::Finish(const Buffer& signature, Buffer* output) {
85    uint8_t digest[EVP_MAX_MD_SIZE];
86    unsigned int digest_len;
87    if (!HMAC_Final(&ctx_, digest, &digest_len))
88        return KM_ERROR_UNKNOWN_ERROR;
89
90    switch (purpose()) {
91    case KM_PURPOSE_SIGN:
92        output->reserve(tag_length_);
93        output->write(digest, tag_length_);
94        return KM_ERROR_OK;
95    case KM_PURPOSE_VERIFY:
96        if (signature.available_read() != tag_length_)
97            return KM_ERROR_INVALID_INPUT_LENGTH;
98        if (memcmp(signature.peek_read(), digest, tag_length_) != 0)
99            return KM_ERROR_VERIFICATION_FAILED;
100        return KM_ERROR_OK;
101    default:
102        return KM_ERROR_UNSUPPORTED_PURPOSE;
103    }
104}
105
106}  // namespace keymaster
107