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 //
18 // fsverity_init is a tool for loading X.509 certificates into the kernel keyring used by the
19 // fsverity builtin signature verification kernel feature
20 // (https://www.kernel.org/doc/html/latest/filesystems/fsverity.html#built-in-signature-verification).
21 // Starting in Android 14, Android has actually stopped using this feature, as it was too inflexible
22 // and caused problems. It has been replaced by userspace signature verification. Also, some uses
23 // of fsverity in Android are now for integrity-only use cases.
24 //
25 // Regardless, there may exist fsverity files on-disk that were created by Android 13 or earlier.
26 // These files still have builtin signatures. If the kernel is an older kernel that still has
27 // CONFIG_FS_VERITY_BUILTIN_SIGNATURES enabled, these files cannot be opened unless the
28 // corresponding key is in the ".fs-verity" keyring. Therefore, this tool still has to exist and be
29 // used to load keys into the kernel, even though this has no security purpose anymore.
30 //
31 // This tool can be removed as soon as all supported kernels are guaranteed to have
32 // CONFIG_FS_VERITY_BUILTIN_SIGNATURES disabled, or alternatively as soon as support for upgrades
33 // from Android 13 or earlier is no longer required.
34 //
35
36 #define LOG_TAG "fsverity_init"
37
38 #include <sys/types.h>
39
40 #include <filesystem>
41 #include <string>
42
43 #include <android-base/file.h>
44 #include <android-base/logging.h>
45 #include <android-base/strings.h>
46 #include <android_security_flag.h>
47 #include <log/log.h>
48 #include <mini_keyctl_utils.h>
49
LoadKeyFromFile(key_serial_t keyring_id,const char * keyname,const std::string & path)50 void LoadKeyFromFile(key_serial_t keyring_id, const char* keyname, const std::string& path) {
51 LOG(INFO) << "LoadKeyFromFile path=" << path << " keyname=" << keyname;
52 std::string content;
53 if (!android::base::ReadFileToString(path, &content)) {
54 LOG(ERROR) << "Failed to read key from " << path;
55 return;
56 }
57 if (add_key("asymmetric", keyname, content.c_str(), content.size(), keyring_id) < 0) {
58 PLOG(ERROR) << "Failed to add key from " << path;
59 }
60 }
61
LoadKeyFromDirectory(key_serial_t keyring_id,const char * keyname_prefix,const char * dir)62 void LoadKeyFromDirectory(key_serial_t keyring_id, const char* keyname_prefix, const char* dir) {
63 if (!std::filesystem::exists(dir)) {
64 return;
65 }
66 int counter = 0;
67 for (const auto& entry : std::filesystem::directory_iterator(dir)) {
68 if (!android::base::EndsWithIgnoreCase(entry.path().c_str(), ".der")) continue;
69 std::string keyname = keyname_prefix + std::to_string(counter);
70 counter++;
71 LoadKeyFromFile(keyring_id, keyname.c_str(), entry.path());
72 }
73 }
74
LoadKeyFromVerifiedPartitions(key_serial_t keyring_id)75 void LoadKeyFromVerifiedPartitions(key_serial_t keyring_id) {
76 // NB: Directories need to be synced with FileIntegrityService.java in
77 // frameworks/base.
78 LoadKeyFromDirectory(keyring_id, "fsv_system_", "/system/etc/security/fsverity");
79 LoadKeyFromDirectory(keyring_id, "fsv_product_", "/product/etc/security/fsverity");
80 }
81
main(int argc,const char ** argv)82 int main(int argc, const char** argv) {
83 if (android::security::flag::deprecate_fsverity_init()) {
84 // Don't load keys to the built-in fs-verity keyring in kernel. This will make existing
85 // files not readable. We expect to only enable the flag when there are no such files or
86 // when failure is ok (e.g. with a fallback).
87 return 0;
88 }
89
90 if (argc < 2) {
91 LOG(ERROR) << "Not enough arguments";
92 return -1;
93 }
94
95 key_serial_t keyring_id = android::GetKeyringId(".fs-verity");
96 if (keyring_id < 0) {
97 // This is expected on newer kernels. See comment at the beginning of this file.
98 LOG(DEBUG) << "no initialization required";
99 return 0;
100 }
101
102 const std::string_view command = argv[1];
103
104 if (command == "--load-verified-keys") {
105 LoadKeyFromVerifiedPartitions(keyring_id);
106 } else {
107 LOG(ERROR) << "Unknown argument(s).";
108 return -1;
109 }
110
111 return 0;
112 }
113