1 // Copyright 2023 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 //
15 ////////////////////////////////////////////////////////////////////////////////
16
17 #include "tink/aead/aes_gcm_key.h"
18
19 #include <string>
20
21 #include "absl/strings/escaping.h"
22 #include "absl/types/optional.h"
23 #include "tink/aead/aes_gcm_parameters.h"
24 #include "tink/partial_key_access_token.h"
25 #include "tink/restricted_data.h"
26 #include "tink/subtle/subtle_util.h"
27 #include "tink/util/status.h"
28 #include "tink/util/statusor.h"
29
30 namespace crypto {
31 namespace tink {
32 namespace {
33
ComputeOutputPrefix(const AesGcmParameters & parameters,absl::optional<int> id_requirement)34 util::StatusOr<std::string> ComputeOutputPrefix(
35 const AesGcmParameters& parameters, absl::optional<int> id_requirement) {
36 switch (parameters.GetVariant()) {
37 case AesGcmParameters::Variant::kNoPrefix:
38 return std::string(""); // Empty prefix.
39 case AesGcmParameters::Variant::kCrunchy:
40 if (!id_requirement.has_value()) {
41 return util::Status(
42 absl::StatusCode::kInvalidArgument,
43 "id requirement must have value with kCrunchy or kLegacy");
44 }
45 return absl::StrCat(absl::HexStringToBytes("00"),
46 subtle::BigEndian32(*id_requirement));
47 case AesGcmParameters::Variant::kTink:
48 if (!id_requirement.has_value()) {
49 return util::Status(absl::StatusCode::kInvalidArgument,
50 "id requirement must have value with kTink");
51 }
52 return absl::StrCat(absl::HexStringToBytes("01"),
53 subtle::BigEndian32(*id_requirement));
54 default:
55 return util::Status(
56 absl::StatusCode::kInvalidArgument,
57 absl::StrCat("Invalid variant: ", parameters.GetVariant()));
58 }
59 }
60
61 } // namespace
62
Create(const AesGcmParameters & parameters,const RestrictedData & key_bytes,absl::optional<int> id_requirement,PartialKeyAccessToken token)63 util::StatusOr<AesGcmKey> AesGcmKey::Create(const AesGcmParameters& parameters,
64 const RestrictedData& key_bytes,
65 absl::optional<int> id_requirement,
66 PartialKeyAccessToken token) {
67 if (parameters.KeySizeInBytes() != key_bytes.size()) {
68 return util::Status(absl::StatusCode::kInvalidArgument,
69 "Key size does not match AES-GCM parameters");
70 }
71 if (parameters.HasIdRequirement() && !id_requirement.has_value()) {
72 return util::Status(
73 absl::StatusCode::kInvalidArgument,
74 "Cannot create key without ID requirement with parameters with ID "
75 "requirement");
76 }
77 if (!parameters.HasIdRequirement() && id_requirement.has_value()) {
78 return util::Status(
79 absl::StatusCode::kInvalidArgument,
80 "Cannot create key with ID requirement with parameters without ID "
81 "requirement");
82 }
83 util::StatusOr<std::string> output_prefix =
84 ComputeOutputPrefix(parameters, id_requirement);
85 if (!output_prefix.ok()) {
86 return output_prefix.status();
87 }
88 return AesGcmKey(parameters, key_bytes, id_requirement,
89 *std::move(output_prefix));
90 }
91
operator ==(const Key & other) const92 bool AesGcmKey::operator==(const Key& other) const {
93 const AesGcmKey* that = dynamic_cast<const AesGcmKey*>(&other);
94 if (that == nullptr) {
95 return false;
96 }
97 if (GetParameters() != that->GetParameters()) {
98 return false;
99 }
100 if (id_requirement_ != that->id_requirement_) {
101 return false;
102 }
103 return key_bytes_ == that->key_bytes_;
104 }
105
106 } // namespace tink
107 } // namespace crypto
108