1 /*
2  * Copyright (C) 2020 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 TRACE_TAG TRANSPORT
18 
19 #include "adb_mdns.h"
20 
21 #include <set>
22 
23 #include <android-base/stringprintf.h>
24 #include <android-base/strings.h>
25 
26 #include "adb_trace.h"
27 
28 #define ADB_SECURE_SERVICE_VERSION_TXT_RECORD(ver) ("v=" #ver)
29 
30 const char* kADBSecurePairingServiceTxtRecord =
31         ADB_SECURE_SERVICE_VERSION_TXT_RECORD(ADB_SECURE_SERVICE_VERSION);
32 const char* kADBSecureConnectServiceTxtRecord =
33         ADB_SECURE_SERVICE_VERSION_TXT_RECORD(ADB_SECURE_SERVICE_VERSION);
34 
35 #define ADB_FULL_MDNS_SERVICE_TYPE(atype) ("_" atype "._tcp")
36 const char* kADBDNSServices[] = {ADB_FULL_MDNS_SERVICE_TYPE(ADB_MDNS_SERVICE_TYPE),
37                                  ADB_FULL_MDNS_SERVICE_TYPE(ADB_MDNS_TLS_PAIRING_TYPE),
38                                  ADB_FULL_MDNS_SERVICE_TYPE(ADB_MDNS_TLS_CONNECT_TYPE)};
39 
40 const char* kADBDNSServiceTxtRecords[] = {
41         nullptr,
42         kADBSecurePairingServiceTxtRecord,
43         kADBSecureConnectServiceTxtRecord,
44 };
45 
46 #if ADB_HOST
47 namespace {
48 
49 std::atomic<bool> g_allowedlist_configured{false};
50 [[clang::no_destroy]] std::set<int> g_autoconn_allowedlist;
51 
52 void config_auto_connect_services() {
53     bool expected = false;
54     if (!g_allowedlist_configured.compare_exchange_strong(expected, true)) {
55         return;
56     }
57 
58     // ADB_MDNS_AUTO_CONNECT is a comma-delimited list of mdns services
59     // that are allowed to auto-connect. By default, only allow "adb-tls-connect"
60     // to auto-connect, since this is filtered down to auto-connect only to paired
61     // devices.
62     g_autoconn_allowedlist.insert(kADBSecureConnectServiceRefIndex);
63     const char* srvs = getenv("ADB_MDNS_AUTO_CONNECT");
64     if (!srvs) {
65         return;
66     }
67 
68     if (strcmp(srvs, "0") == 0) {
69         D("Disabling all auto-connecting");
70         g_autoconn_allowedlist.clear();
71         return;
72     }
73 
74     if (strcmp(srvs, "all") == 0) {
75         D("Allow all auto-connecting");
76         g_autoconn_allowedlist.insert(kADBTransportServiceRefIndex);
77         return;
78     }
79 
80     // Selectively choose which services to allow auto-connect.
81     // E.g. ADB_MDNS_AUTO_CONNECT=adb,adb-tls-connect would allow
82     // _adb._tcp and _adb-tls-connnect._tcp services to auto-connect.
83     auto srvs_list = android::base::Split(srvs, ",");
84     std::set<int> new_allowedlist;
85     for (const auto& item : srvs_list) {
86         auto full_srv = android::base::StringPrintf("_%s._tcp", item.data());
87         std::optional<int> idx = adb_DNSServiceIndexByName(full_srv);
88         if (idx.has_value()) {
89             new_allowedlist.insert(*idx);
90         }
91     }
92 
93     if (!new_allowedlist.empty()) {
94         g_autoconn_allowedlist = std::move(new_allowedlist);
95     }
96 
97     std::string res;
98     std::for_each(g_autoconn_allowedlist.begin(), g_autoconn_allowedlist.end(), [&](const int& i) {
99         res += kADBDNSServices[i];
100         res += ",";
101     });
102     D("mdns auto-connect allowedlist: [%s]", res.data());
103 }
104 
105 }  // namespace
106 
107 std::optional<int> adb_DNSServiceIndexByName(std::string_view reg_type) {
108     for (int i = 0; i < kNumADBDNSServices; ++i) {
109         if (!strncmp(reg_type.data(), kADBDNSServices[i], strlen(kADBDNSServices[i]))) {
110             return i;
111         }
112     }
113     return std::nullopt;
114 }
115 
116 bool adb_DNSServiceShouldAutoConnect(std::string_view reg_type, std::string_view service_name) {
117     config_auto_connect_services();
118 
119     // Try to auto-connect to any "_adb" or "_adb-tls-connect" services excluding emulator services.
120     std::optional<int> index = adb_DNSServiceIndexByName(reg_type);
121     if (!index ||
122         (index != kADBTransportServiceRefIndex && index != kADBSecureConnectServiceRefIndex)) {
123         return false;
124     }
125     if (g_autoconn_allowedlist.find(*index) == g_autoconn_allowedlist.end()) {
126         D("Auto-connect for reg_type '%s' disabled", reg_type.data());
127         return false;
128     }
129     // Ignore adb-EMULATOR* service names, as it interferes with the
130     // emulator ports that are already connected.
131     if (android::base::StartsWith(service_name, "adb-EMULATOR")) {
132         LOG(INFO) << "Ignoring emulator transport service [" << service_name << "]";
133         return false;
134     }
135     return true;
136 }
137 
138 #endif  // ADB_HOST
139