1 /*
2 * Copyright (C) 2022 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 #include <fuzzbinder/libbinder_driver.h>
17
18 #include <fuzzbinder/random_parcel.h>
19
20 #include <android-base/logging.h>
21 #include <binder/IPCThreadState.h>
22 #include <binder/ProcessState.h>
23
24 #include <private/android_filesystem_config.h>
25
26 using android::binder::unique_fd;
27
28 namespace android {
29
fuzzService(const sp<IBinder> & binder,FuzzedDataProvider && provider)30 void fuzzService(const sp<IBinder>& binder, FuzzedDataProvider&& provider) {
31 fuzzService(std::vector<sp<IBinder>>{binder}, std::move(provider));
32 }
33
fuzzService(const std::vector<sp<IBinder>> & binders,FuzzedDataProvider && provider)34 void fuzzService(const std::vector<sp<IBinder>>& binders, FuzzedDataProvider&& provider) {
35 RandomParcelOptions options{
36 .extraBinders = binders,
37 .extraFds = {},
38 };
39
40 // Reserved bytes so that we don't have to change fuzzers and seed corpus if
41 // we introduce anything new in fuzzService.
42 std::vector<uint8_t> reservedBytes = provider.ConsumeBytes<uint8_t>(8);
43 (void)reservedBytes;
44
45 // always refresh the calling identity, because we sometimes set it below, but also,
46 // the code we're fuzzing might reset it
47 IPCThreadState::self()->clearCallingIdentity();
48
49 // Always take so that a perturbation of just the one ConsumeBool byte will always
50 // take the same path, but with a different UID. Without this, the fuzzer needs to
51 // guess both the change in value and the shift at the same time.
52 int64_t maybeSetUid = provider.PickValueInArray<int64_t>(
53 {static_cast<int64_t>(AID_ROOT) << 32, static_cast<int64_t>(AID_SYSTEM) << 32,
54 provider.ConsumeIntegralInRange<int64_t>(static_cast<int64_t>(AID_ROOT) << 32,
55 static_cast<int64_t>(AID_USER) << 32),
56 provider.ConsumeIntegral<int64_t>()});
57
58 if (provider.ConsumeBool()) {
59 // set calling uid
60 IPCThreadState::self()->restoreCallingIdentity(maybeSetUid);
61 }
62
63 while (provider.remaining_bytes() > 0) {
64 // Most of the AIDL services will have small set of transaction codes.
65 // TODO(b/295942369) : Add remaining transact codes from IBinder.h
66 uint32_t code = provider.ConsumeBool() ? provider.ConsumeIntegral<uint32_t>()
67 : provider.ConsumeBool()
68 ? provider.ConsumeIntegralInRange<uint32_t>(0, 100)
69 : provider.PickValueInArray<uint32_t>(
70 {IBinder::DUMP_TRANSACTION, IBinder::PING_TRANSACTION,
71 IBinder::SHELL_COMMAND_TRANSACTION, IBinder::INTERFACE_TRANSACTION,
72 IBinder::SYSPROPS_TRANSACTION, IBinder::EXTENSION_TRANSACTION,
73 IBinder::TWEET_TRANSACTION, IBinder::LIKE_TRANSACTION});
74 uint32_t flags = provider.ConsumeIntegral<uint32_t>();
75 Parcel data;
76 // for increased fuzz coverage
77 data.setEnforceNoDataAvail(false);
78 data.setServiceFuzzing();
79
80 sp<IBinder> target = options.extraBinders.at(
81 provider.ConsumeIntegralInRange<size_t>(0, options.extraBinders.size() - 1));
82 options.writeHeader = [&target](Parcel* p, FuzzedDataProvider& provider) {
83 // most code will be behind checks that the head of the Parcel
84 // is exactly this, so make it easier for fuzzers to reach this
85 if (provider.ConsumeBool()) {
86 p->writeInterfaceToken(target->getInterfaceDescriptor());
87 }
88 };
89
90 std::vector<uint8_t> subData = provider.ConsumeBytes<uint8_t>(
91 provider.ConsumeIntegralInRange<size_t>(0, provider.remaining_bytes()));
92 fillRandomParcel(&data, FuzzedDataProvider(subData.data(), subData.size()), &options);
93
94 Parcel reply;
95 // for increased fuzz coverage
96 reply.setEnforceNoDataAvail(false);
97 reply.setServiceFuzzing();
98 (void)target->transact(code, data, &reply, flags);
99
100 // feed back in binders and fds that are returned from the service, so that
101 // we can fuzz those binders, and use the fds and binders to feed back into
102 // the binders
103 auto retBinders = reply.debugReadAllStrongBinders();
104 options.extraBinders.insert(options.extraBinders.end(), retBinders.begin(),
105 retBinders.end());
106 auto retFds = reply.debugReadAllFileDescriptors();
107 for (size_t i = 0; i < retFds.size(); i++) {
108 options.extraFds.push_back(unique_fd(dup(retFds[i])));
109 }
110 }
111
112 // invariants
113 auto ps = ProcessState::selfOrNull();
114 if (ps) {
115 CHECK_EQ(0, ps->getThreadPoolMaxTotalThreadCount())
116 << "Binder threadpool should not be started by fuzzer because coverage can only "
117 "cover in-process calls.";
118 }
119 }
120
121 } // namespace android
122