1 /*
2  * Copyright (C) 2019 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 #define LOG_TAG "fsverity_init"
18 
19 #include <sys/types.h>
20 
21 #include <filesystem>
22 #include <string>
23 
24 #include <android-base/file.h>
25 #include <android-base/logging.h>
26 #include <android-base/properties.h>
27 #include <android-base/strings.h>
28 #include <log/log.h>
29 #include <mini_keyctl_utils.h>
30 
31 bool LoadKeyToKeyring(key_serial_t keyring_id, const char* desc, const char* data, size_t size) {
32     key_serial_t key = add_key("asymmetric", desc, data, size, keyring_id);
33     if (key < 0) {
34         PLOG(ERROR) << "Failed to add key";
35         return false;
36     }
37     return true;
38 }
39 
40 void LoadKeyFromDirectory(key_serial_t keyring_id, const char* keyname, const char* dir) {
41     if (!std::filesystem::exists(dir)) {
42         return;
43     }
44     for (const auto& entry : std::filesystem::directory_iterator(dir)) {
45         if (!android::base::EndsWithIgnoreCase(entry.path().c_str(), ".der")) continue;
46         std::string content;
47         if (!android::base::ReadFileToString(entry.path(), &content)) {
48             continue;
49         }
50         if (!LoadKeyToKeyring(keyring_id, keyname, content.c_str(), content.size())) {
51             LOG(ERROR) << "Failed to load key from " << entry.path();
52         }
53     }
54 }
55 
56 void LoadKeyFromVerifiedPartitions(key_serial_t keyring_id) {
57     // NB: Directories need to be synced with FileIntegrityService.java in
58     // frameworks/base.
59     LoadKeyFromDirectory(keyring_id, "fsv_system", "/system/etc/security/fsverity");
60     LoadKeyFromDirectory(keyring_id, "fsv_product", "/product/etc/security/fsverity");
61 }
62 
63 int main(int /*argc*/, const char** /*argv*/) {
64     key_serial_t keyring_id = android::GetKeyringId(".fs-verity");
65     if (keyring_id < 0) {
66         LOG(ERROR) << "Failed to find .fs-verity keyring id";
67         return -1;
68     }
69 
70     // Requires files backed by fs-verity to be verified with a key in .fs-verity
71     // keyring.
72     if (!android::base::WriteStringToFile("1", "/proc/sys/fs/verity/require_signatures")) {
73         PLOG(ERROR) << "Failed to enforce fs-verity signature";
74     }
75 
76     LoadKeyFromVerifiedPartitions(keyring_id);
77 
78     if (!android::base::GetBoolProperty("ro.debuggable", false)) {
79         if (keyctl_restrict_keyring(keyring_id, nullptr, nullptr) < 0) {
80             PLOG(ERROR) << "Cannot restrict .fs-verity keyring";
81         }
82     }
83     return 0;
84 }
85