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/mac/hmac_key.h"
18
19 #include <memory>
20 #include <string>
21
22 #include "absl/base/attributes.h"
23 #include "absl/strings/escaping.h"
24 #include "absl/strings/str_format.h"
25 #include "absl/types/optional.h"
26 #include "tink/mac/hmac_parameters.h"
27 #include "tink/partial_key_access_token.h"
28 #include "tink/restricted_data.h"
29 #include "tink/subtle/subtle_util.h"
30 #include "tink/util/status.h"
31 #include "tink/util/statusor.h"
32
33 namespace crypto {
34 namespace tink {
35
Create(const HmacParameters & parameters,const RestrictedData & key_bytes,absl::optional<int> id_requirement,PartialKeyAccessToken token)36 util::StatusOr<HmacKey> HmacKey::Create(const HmacParameters& parameters,
37 const RestrictedData& key_bytes,
38 absl::optional<int> id_requirement,
39 PartialKeyAccessToken token) {
40 if (parameters.KeySizeInBytes() != key_bytes.size()) {
41 return util::Status(absl::StatusCode::kInvalidArgument,
42 "Key size does not match HMAC parameters");
43 }
44 if (parameters.HasIdRequirement() && !id_requirement.has_value()) {
45 return util::Status(
46 absl::StatusCode::kInvalidArgument,
47 "Cannot create key without ID requirement with parameters with ID "
48 "requirement");
49 }
50 if (!parameters.HasIdRequirement() && id_requirement.has_value()) {
51 return util::Status(
52 absl::StatusCode::kInvalidArgument,
53 "Cannot create key with ID requirement with parameters without ID "
54 "requirement");
55 }
56 util::StatusOr<std::string> output_prefix =
57 ComputeOutputPrefix(parameters, id_requirement);
58 if (!output_prefix.ok()) {
59 return output_prefix.status();
60 }
61 return HmacKey(parameters, key_bytes, id_requirement,
62 *std::move(output_prefix));
63 }
64
ComputeOutputPrefix(const HmacParameters & parameters,absl::optional<int> id_requirement)65 util::StatusOr<std::string> HmacKey::ComputeOutputPrefix(
66 const HmacParameters& parameters, absl::optional<int> id_requirement) {
67 switch (parameters.GetVariant()) {
68 case HmacParameters::Variant::kNoPrefix:
69 return std::string(""); // Empty prefix.
70 case HmacParameters::Variant::kLegacy:
71 ABSL_FALLTHROUGH_INTENDED;
72 case HmacParameters::Variant::kCrunchy:
73 if (!id_requirement.has_value()) {
74 return util::Status(
75 absl::StatusCode::kInvalidArgument,
76 "id requirement must have value with kCrunchy or kLegacy");
77 }
78 return absl::StrCat(absl::HexStringToBytes("00"),
79 subtle::BigEndian32(*id_requirement));
80 case HmacParameters::Variant::kTink:
81 if (!id_requirement.has_value()) {
82 return util::Status(absl::StatusCode::kInvalidArgument,
83 "id requirement must have value with kTink");
84 }
85 return absl::StrCat(absl::HexStringToBytes("01"),
86 subtle::BigEndian32(*id_requirement));
87 default:
88 return util::Status(
89 absl::StatusCode::kInvalidArgument,
90 absl::StrCat("Invalid variant: ", parameters.GetVariant()));
91 }
92 }
93
operator ==(const Key & other) const94 bool HmacKey::operator==(const Key& other) const {
95 const HmacKey* that = dynamic_cast<const HmacKey*>(&other);
96 if (that == nullptr) {
97 return false;
98 }
99 if (GetParameters() != that->GetParameters()) {
100 return false;
101 }
102 if (id_requirement_ != that->id_requirement_) {
103 return false;
104 }
105 return key_bytes_ == that->key_bytes_;
106 }
107
108 } // namespace tink
109 } // namespace crypto
110