1 /*
2 * Copyright (C) 2018 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 "VerityUtils"
18
19 #include <nativehelper/JNIHelp.h>
20 #include <nativehelper/ScopedPrimitiveArray.h>
21 #include <nativehelper/ScopedUtfChars.h>
22 #include <utils/Log.h>
23 #include "jni.h"
24
25 #include <errno.h>
26 #include <fcntl.h>
27 #include <linux/fsverity.h>
28 #include <linux/stat.h>
29 #include <string.h>
30 #include <sys/ioctl.h>
31 #include <sys/stat.h>
32 #include <sys/types.h>
33
34 #include <android-base/unique_fd.h>
35
36 #include <type_traits>
37
38 namespace android {
39
40 namespace {
41
enableFsverity(JNIEnv * env,jobject,jstring filePath,jbyteArray signature)42 int enableFsverity(JNIEnv *env, jobject /* clazz */, jstring filePath, jbyteArray signature) {
43 ScopedUtfChars path(env, filePath);
44 if (path.c_str() == nullptr) {
45 return EINVAL;
46 }
47 ::android::base::unique_fd rfd(open(path.c_str(), O_RDONLY | O_CLOEXEC));
48 if (rfd.get() < 0) {
49 return errno;
50 }
51 ScopedByteArrayRO signature_bytes(env, signature);
52 if (signature_bytes.get() == nullptr) {
53 return EINVAL;
54 }
55
56 fsverity_enable_arg arg = {};
57 arg.version = 1;
58 arg.hash_algorithm = FS_VERITY_HASH_ALG_SHA256; // hardcoded in measureFsverity below
59 arg.block_size = 4096;
60 arg.salt_size = 0;
61 arg.salt_ptr = reinterpret_cast<uintptr_t>(nullptr);
62 arg.sig_size = signature_bytes.size();
63 arg.sig_ptr = reinterpret_cast<uintptr_t>(signature_bytes.get());
64
65 if (ioctl(rfd.get(), FS_IOC_ENABLE_VERITY, &arg) < 0) {
66 return errno;
67 }
68 return 0;
69 }
70
71 // Returns whether the file has fs-verity enabled.
72 // 0 if it is not present, 1 if is present, and -errno if there was an error.
statxForFsverity(JNIEnv * env,jobject,jstring filePath)73 int statxForFsverity(JNIEnv *env, jobject /* clazz */, jstring filePath) {
74 ScopedUtfChars path(env, filePath);
75
76 struct statx out = {};
77 if (statx(AT_FDCWD, path.c_str(), 0 /* flags */, STATX_ALL, &out) != 0) {
78 return -errno;
79 }
80
81 // Validity check.
82 if ((out.stx_attributes_mask & STATX_ATTR_VERITY) == 0) {
83 ALOGE("Unexpected, STATX_ATTR_VERITY not supported by kernel");
84 return -ENOSYS;
85 }
86
87 return (out.stx_attributes & STATX_ATTR_VERITY) != 0;
88 }
89
measureFsverity(JNIEnv * env,jobject,jstring filePath,jbyteArray digest)90 int measureFsverity(JNIEnv *env, jobject /* clazz */, jstring filePath, jbyteArray digest) {
91 static constexpr auto kDigestSha256 = 32;
92 using Storage = std::aligned_storage_t<sizeof(fsverity_digest) + kDigestSha256>;
93
94 Storage bytes;
95 fsverity_digest *data = reinterpret_cast<fsverity_digest *>(&bytes);
96 data->digest_size = kDigestSha256; // the only input/output parameter
97
98 ScopedUtfChars path(env, filePath);
99 ::android::base::unique_fd rfd(open(path.c_str(), O_RDONLY | O_CLOEXEC));
100 if (rfd.get() < 0) {
101 return rfd.get();
102 }
103 if (auto err = ioctl(rfd.get(), FS_IOC_MEASURE_VERITY, data); err < 0) {
104 return err;
105 }
106
107 if (data->digest_algorithm != FS_VERITY_HASH_ALG_SHA256) {
108 return -EINVAL;
109 }
110
111 if (digest != nullptr && data->digest_size > 0) {
112 auto digestSize = env->GetArrayLength(digest);
113 if (data->digest_size > digestSize) {
114 return -E2BIG;
115 }
116 env->SetByteArrayRegion(digest, 0, data->digest_size, (const jbyte *)data->digest);
117 }
118
119 return 0;
120 }
121 const JNINativeMethod sMethods[] = {
122 {"enableFsverityNative", "(Ljava/lang/String;[B)I", (void *)enableFsverity},
123 {"statxForFsverityNative", "(Ljava/lang/String;)I", (void *)statxForFsverity},
124 {"measureFsverityNative", "(Ljava/lang/String;[B)I", (void *)measureFsverity},
125 };
126
127 } // namespace
128
register_com_android_internal_security_VerityUtils(JNIEnv * env)129 int register_com_android_internal_security_VerityUtils(JNIEnv *env) {
130 return jniRegisterNativeMethods(env, "com/android/internal/security/VerityUtils", sMethods,
131 NELEM(sMethods));
132 }
133
134 } // namespace android
135