1 /*
2 * Copyright (C) 2020 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 "VoldNativeServiceValidation.h"
18
19 #include <android-base/stringprintf.h>
20 #include <android-base/strings.h>
21 #include <binder/IPCThreadState.h>
22 #include <binder/IServiceManager.h>
23 #include <private/android_filesystem_config.h>
24
25 #include <cctype>
26 #include <string_view>
27
28 using android::base::StringPrintf;
29 using namespace std::literals;
30
31 namespace android::vold {
32
Ok()33 binder::Status Ok() {
34 return binder::Status::ok();
35 }
36
Exception(uint32_t code,const std::string & msg)37 binder::Status Exception(uint32_t code, const std::string& msg) {
38 return binder::Status::fromExceptionCode(code, String8(msg.c_str()));
39 }
40
CheckPermission(const char * permission)41 binder::Status CheckPermission(const char* permission) {
42 int32_t pid;
43 int32_t uid;
44
45 if (checkCallingPermission(String16(permission), &pid, &uid)) {
46 return Ok();
47 } else {
48 return Exception(binder::Status::EX_SECURITY,
49 StringPrintf("UID %d / PID %d lacks permission %s", uid, pid, permission));
50 }
51 }
52
CheckUidOrRoot(uid_t expectedUid)53 binder::Status CheckUidOrRoot(uid_t expectedUid) {
54 uid_t uid = IPCThreadState::self()->getCallingUid();
55 if (uid == expectedUid || uid == AID_ROOT) {
56 return Ok();
57 } else {
58 return Exception(binder::Status::EX_SECURITY,
59 StringPrintf("UID %d is not expected UID %d", uid, expectedUid));
60 }
61 }
62
CheckArgumentId(const std::string & id)63 binder::Status CheckArgumentId(const std::string& id) {
64 if (id.empty()) {
65 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT, "Missing ID");
66 }
67 for (const char& c : id) {
68 if (!std::isalnum(c) && c != ':' && c != ',' && c != ';') {
69 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT,
70 StringPrintf("ID %s is malformed", id.c_str()));
71 }
72 }
73 return Ok();
74 }
75
CheckArgumentPath(const std::string & path)76 binder::Status CheckArgumentPath(const std::string& path) {
77 if (path.empty()) {
78 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT, "Missing path");
79 }
80 if (path[0] != '/') {
81 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT,
82 StringPrintf("Path %s is relative", path.c_str()));
83 }
84 if (path.find("/../"sv) != path.npos || android::base::EndsWith(path, "/.."sv)) {
85 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT,
86 StringPrintf("Path %s is shady", path.c_str()));
87 }
88 for (const char& c : path) {
89 if (c == '\0' || c == '\n') {
90 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT,
91 StringPrintf("Path %s is malformed", path.c_str()));
92 }
93 }
94 return Ok();
95 }
96
CheckArgumentHex(const std::string & hex)97 binder::Status CheckArgumentHex(const std::string& hex) {
98 // Empty hex strings are allowed
99 for (const char& c : hex) {
100 if (!std::isxdigit(c) && c != ':' && c != '-') {
101 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT,
102 StringPrintf("Hex %s is malformed", hex.c_str()));
103 }
104 }
105 return Ok();
106 }
107
CheckIncrementalPath(IncrementalPathKind kind,const std::string & path)108 binder::Status CheckIncrementalPath(IncrementalPathKind kind, const std::string& path) {
109 if (auto status = CheckArgumentPath(path); !status.isOk()) {
110 return status;
111 }
112 if (kind == IncrementalPathKind::MountSource || kind == IncrementalPathKind::MountTarget ||
113 kind == IncrementalPathKind::Any) {
114 if (android::base::StartsWith(path, "/data/incremental/MT_")) {
115 if (kind != IncrementalPathKind::MountSource &&
116 (android::base::EndsWith(path, "/mount") || path.find("/mount/") != path.npos)) {
117 return Ok();
118 }
119 if (kind != IncrementalPathKind::MountTarget &&
120 (android::base::EndsWith(path, "/backing_store") ||
121 path.find("/backing_store/") != path.npos)) {
122 return Ok();
123 }
124 }
125 }
126 if (kind == IncrementalPathKind::Bind || kind == IncrementalPathKind::Any) {
127 if (android::base::StartsWith(path, "/data/app/")) {
128 return Ok();
129 }
130 }
131 return Exception(binder::Status::EX_ILLEGAL_ARGUMENT,
132 StringPrintf("Path '%s' is not allowed", path.c_str()));
133 }
134
135 } // namespace android::vold
136