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1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #include "components/gcm_driver/crypto/gcm_message_cryptographer.h" | |
6 | |
7 #include <openssl/aead.h> | |
8 #include <stddef.h> | |
9 #include <stdint.h> | |
10 | |
11 #include "base/logging.h" | |
12 #include "base/numerics/safe_math.h" | |
13 #include "base/strings/string_util.h" | |
14 | |
15 namespace gcm { | |
16 | |
17 namespace { | |
18 | |
19 // The BoringSSL functions used to seal (encrypt) and open (decrypt) a payload | |
20 // follow the same prototype, declared as follows. | |
21 using EVP_AEAD_CTX_TransformFunction = | |
22 int(const EVP_AEAD_CTX *ctx, uint8_t *out, size_t *out_len, | |
23 size_t max_out_len, const uint8_t *nonce, size_t nonce_len, | |
24 const uint8_t *in, size_t in_len, const uint8_t *ad, size_t ad_len); | |
25 | |
26 } // namespace | |
27 | |
28 bool GCMMessageCryptographer::EncryptDecryptRecordInternal( | |
29 Mode mode, | |
30 const base::StringPiece& input, | |
31 const base::StringPiece& key, | |
32 const base::StringPiece& nonce, | |
33 std::string* output) const { | |
34 DCHECK(output); | |
35 | |
36 const EVP_AEAD* aead = EVP_aead_aes_128_gcm(); | |
37 | |
38 EVP_AEAD_CTX context; | |
39 if (!EVP_AEAD_CTX_init(&context, aead, | |
40 reinterpret_cast<const uint8_t*>(key.data()), | |
41 key.size(), EVP_AEAD_DEFAULT_TAG_LENGTH, nullptr)) { | |
42 return false; | |
43 } | |
44 | |
45 base::CheckedNumeric<size_t> maximum_output_length(input.size()); | |
46 if (mode == ENCRYPT) | |
47 maximum_output_length += kAuthenticationTagBytes; | |
48 | |
49 // WriteInto requires the buffer to finish with a NULL-byte. | |
50 maximum_output_length += 1; | |
51 | |
52 size_t output_length = 0; | |
53 uint8_t* raw_output = reinterpret_cast<uint8_t*>( | |
54 base::WriteInto(output, maximum_output_length.ValueOrDie())); | |
55 | |
56 EVP_AEAD_CTX_TransformFunction* transform_function = | |
57 mode == ENCRYPT ? EVP_AEAD_CTX_seal : EVP_AEAD_CTX_open; | |
58 | |
59 if (!transform_function( | |
60 &context, raw_output, &output_length, output->size(), | |
61 reinterpret_cast<const uint8_t*>(nonce.data()), nonce.size(), | |
62 reinterpret_cast<const uint8_t*>(input.data()), input.size(), | |
63 nullptr, 0)) { | |
64 EVP_AEAD_CTX_cleanup(&context); | |
65 return false; | |
66 } | |
67 | |
68 EVP_AEAD_CTX_cleanup(&context); | |
69 | |
70 base::CheckedNumeric<size_t> expected_output_length(input.size()); | |
71 if (mode == ENCRYPT) | |
72 expected_output_length += kAuthenticationTagBytes; | |
73 else | |
74 expected_output_length -= kAuthenticationTagBytes; | |
75 | |
76 DCHECK_EQ(expected_output_length.ValueOrDie(), output_length); | |
77 | |
78 output->resize(output_length); | |
79 return true; | |
80 } | |
81 | |
82 } // namespace gcm | |
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