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 <android-base/logging.h>
18 #include <android-base/result.h>
19 #include <android/dlext.h>
20 #include <dlfcn.h>
21
22 #include <cstdlib>
23 #include <iostream>
24 #include <string>
25
26 #include "vm_main.h"
27
28 using android::base::Error;
29 using android::base::Result;
30
31 extern "C" {
32 enum {
33 ANDROID_NAMESPACE_TYPE_REGULAR = 0,
34 ANDROID_NAMESPACE_TYPE_ISOLATED = 1,
35 ANDROID_NAMESPACE_TYPE_SHARED = 2,
36 };
37
38 extern struct android_namespace_t* android_create_namespace(
39 const char* name, const char* ld_library_path, const char* default_library_path,
40 uint64_t type, const char* permitted_when_isolated_path,
41 struct android_namespace_t* parent);
42
43 extern bool android_link_namespaces(struct android_namespace_t* from,
44 struct android_namespace_t* to,
45 const char* shared_libs_sonames);
46 } // extern "C"
47
48 static Result<void*> load(const std::string& libname);
49
50 constexpr char entrypoint_name[] = "AVmPayload_main";
51
52 static constexpr const char* kAllowedLibs[] = {
53 "libc.so", "libm.so", "libdl.so", "libdl_android.so",
54 "liblog.so", "libvm_payload.so", "libbinder_ndk.so", "libbinder_rpc_unstable.so",
55 };
56
main(int argc,char * argv[])57 int main(int argc, char* argv[]) {
58 if (argc != 2) {
59 std::cout << "Usage:\n";
60 std::cout << " " << argv[0] << " LIBNAME\n";
61 return EXIT_FAILURE;
62 }
63
64 android::base::InitLogging(argv, &android::base::KernelLogger);
65
66 const char* libname = argv[1];
67 auto handle = load(libname);
68 if (!handle.ok()) {
69 LOG(ERROR) << "Failed to load " << libname << ": " << handle.error().message();
70 return EXIT_FAILURE;
71 }
72
73 AVmPayload_main_t* entry = reinterpret_cast<decltype(entry)>(dlsym(*handle, entrypoint_name));
74 if (entry == nullptr) {
75 LOG(ERROR) << "Failed to find entrypoint `" << entrypoint_name << "`: " << dlerror();
76 return EXIT_FAILURE;
77 }
78
79 return entry();
80 }
81
82 // Create a new linker namespace whose search path is set to the directory of the library. Then
83 // load it from there. Returns the handle to the loaded library if successful. Returns nullptr
84 // if failed.
load(const std::string & libname)85 Result<void*> load(const std::string& libname) {
86 // Parent as nullptr means the default namespace
87 android_namespace_t* parent = nullptr;
88 // The search paths of the new namespace are isolated to restrict system private libraries.
89 const uint64_t type = ANDROID_NAMESPACE_TYPE_ISOLATED;
90 // The directory of the library is appended to the search paths
91 const std::string libdir = libname.substr(0, libname.find_last_of("/"));
92 const char* ld_library_path = libdir.c_str();
93 const char* default_library_path = libdir.c_str();
94
95 android_namespace_t* new_ns = nullptr;
96 new_ns = android_create_namespace("microdroid_app", ld_library_path, default_library_path, type,
97 /* permitted_when_isolated_path */ nullptr, parent);
98 if (new_ns == nullptr) {
99 return Error() << "Failed to create linker namespace: " << dlerror();
100 }
101
102 std::string libs;
103 for (const char* lib : kAllowedLibs) {
104 if (!libs.empty()) libs += ':';
105 libs += lib;
106 }
107 if (!android_link_namespaces(new_ns, nullptr, libs.c_str())) {
108 return Error() << "Failed to link namespace: " << dlerror();
109 }
110
111 const android_dlextinfo info = {
112 .flags = ANDROID_DLEXT_USE_NAMESPACE,
113 .library_namespace = new_ns,
114 };
115 if (auto ret = android_dlopen_ext(libname.c_str(), RTLD_NOW, &info); ret) {
116 return ret;
117 } else {
118 return Error() << "Failed to dlopen: " << dlerror();
119 }
120 }
121