1 // Copyright 2019 Google Inc.
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/streamingaead/decrypting_input_stream.h"
18
19 #include <algorithm>
20 #include <cstring>
21 #include <memory>
22 #include <string>
23 #include <utility>
24 #include <vector>
25
26 #include "absl/memory/memory.h"
27 #include "absl/status/status.h"
28 #include "tink/input_stream.h"
29 #include "tink/primitive_set.h"
30 #include "tink/streaming_aead.h"
31 #include "tink/streamingaead/buffered_input_stream.h"
32 #include "tink/streamingaead/shared_input_stream.h"
33 #include "tink/util/errors.h"
34 #include "tink/util/status.h"
35 #include "tink/util/statusor.h"
36
37 namespace crypto {
38 namespace tink {
39 namespace streamingaead {
40
41 using crypto::tink::PrimitiveSet;
42 using crypto::tink::StreamingAead;
43 using util::Status;
44 using util::StatusOr;
45
46 using StreamingAeadEntry = PrimitiveSet<StreamingAead>::Entry<StreamingAead>;
47
48 // static
New(std::shared_ptr<PrimitiveSet<StreamingAead>> primitives,std::unique_ptr<crypto::tink::InputStream> ciphertext_source,absl::string_view associated_data)49 StatusOr<std::unique_ptr<InputStream>> DecryptingInputStream::New(
50 std::shared_ptr<PrimitiveSet<StreamingAead>> primitives,
51 std::unique_ptr<crypto::tink::InputStream> ciphertext_source,
52 absl::string_view associated_data) {
53 std::unique_ptr<DecryptingInputStream> dec_stream(
54 new DecryptingInputStream());
55 dec_stream->primitives_ = primitives;
56 dec_stream->buffered_ct_source_ =
57 std::make_shared<BufferedInputStream>(std::move(ciphertext_source));
58 dec_stream->associated_data_ = std::string(associated_data);
59 dec_stream->attempted_matching_ = false;
60 dec_stream->matching_stream_ = nullptr;
61 return {std::move(dec_stream)};
62 }
63
Next(const void ** data)64 util::StatusOr<int> DecryptingInputStream::Next(const void** data) {
65 if (matching_stream_ != nullptr) {
66 return matching_stream_->Next(data);
67 }
68 if (attempted_matching_) {
69 return Status(absl::StatusCode::kInvalidArgument,
70 "Could not find a decrypter matching the ciphertext stream.");
71 }
72 // Matching has not been attempted yet, so try it now.
73 attempted_matching_ = true;
74 std::vector<StreamingAeadEntry*> all_primitives = primitives_->get_all();
75
76 for (const StreamingAeadEntry* entry : all_primitives) {
77 StreamingAead& streaming_aead = entry->get_primitive();
78 auto shared_ct = absl::make_unique<SharedInputStream>(
79 buffered_ct_source_.get());
80 auto decrypting_stream_result = streaming_aead.NewDecryptingStream(
81 std::move(shared_ct), associated_data_);
82 if (decrypting_stream_result.ok()) {
83 auto next_result = decrypting_stream_result.value()->Next(data);
84 if (next_result.status().code() == absl::StatusCode::kOutOfRange ||
85 next_result.ok()) { // Found a match.
86 buffered_ct_source_->DisableRewinding();
87 matching_stream_ = std::move(decrypting_stream_result.value());
88 return next_result;
89 }
90 }
91 // Not a match, rewind and try the next primitive.
92 Status s = buffered_ct_source_->Rewind();
93 if (!s.ok()) {
94 return s;
95 }
96 }
97 return Status(absl::StatusCode::kInvalidArgument,
98 "Could not find a decrypter matching the ciphertext stream.");
99 }
100
BackUp(int count)101 void DecryptingInputStream::BackUp(int count) {
102 if (matching_stream_ != nullptr) {
103 matching_stream_->BackUp(count);
104 }
105 }
106
107
Position() const108 int64_t DecryptingInputStream::Position() const {
109 if (matching_stream_ != nullptr) {
110 return matching_stream_->Position();
111 }
112 return 0;
113 }
114
115 } // namespace streamingaead
116 } // namespace tink
117 } // namespace crypto
118