1 /*
2 * Copyright (C) 2021 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 "microdroid/signature.h"
18
19 #include <android-base/endian.h>
20 #include <android-base/file.h>
21
22 using android::base::ErrnoError;
23 using android::base::Error;
24 using android::base::Result;
25
26 namespace android {
27 namespace microdroid {
28
ReadMicrodroidSignature(const std::string & path)29 Result<MicrodroidSignature> ReadMicrodroidSignature(const std::string& path) {
30 std::string content;
31 if (!base::ReadFileToString(path, &content)) {
32 return ErrnoError() << "Failed to read " << path;
33 }
34
35 // read length prefix (4-byte, big-endian)
36 uint32_t size;
37 const size_t length_prefix_bytes = sizeof(size);
38 if (content.size() < length_prefix_bytes) {
39 return Error() << "Invalid signature: size == " << content.size();
40 }
41 size = be32toh(*reinterpret_cast<uint32_t*>(content.data()));
42 if (content.size() < length_prefix_bytes + size) {
43 return Error() << "Invalid signature: size(" << size << ") mimatches to the content size("
44 << content.size() - length_prefix_bytes << ")";
45 }
46 content = content.substr(length_prefix_bytes, size);
47
48 // parse content
49 MicrodroidSignature signature;
50 if (!signature.ParseFromString(content)) {
51 return Error() << "Can't parse MicrodroidSignature from " << path;
52 }
53 return signature;
54 }
55
WriteMicrodroidSignature(const MicrodroidSignature & signature,std::ostream & out)56 Result<void> WriteMicrodroidSignature(const MicrodroidSignature& signature, std::ostream& out) {
57 // prepare content
58 std::string content;
59 if (!signature.SerializeToString(&content)) {
60 return Error() << "Failed to write protobuf.";
61 }
62
63 // write length prefix (4-byte, big-endian)
64 uint32_t size = htobe32(static_cast<uint32_t>(content.size()));
65 out.write(reinterpret_cast<const char*>(&size), sizeof(size));
66
67 // write content
68 out << content;
69
70 return {};
71 }
72
73 } // namespace microdroid
74 } // namespace android