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 #include "server_configurable_flags/disaster_recovery.h"
18 #include "server_configurable_flags/get_flags.h"
19 
20 #if defined(__BIONIC__)
21 #include <cutils/properties.h>
22 #endif  // __BIONIC__
23 #include <regex>
24 #include <string>
25 
26 #include "android-base/file.h"
27 #include "android-base/logging.h"
28 #include "android-base/properties.h"
29 #include "android-base/strings.h"
30 #include "android-base/unique_fd.h"
31 
32 #define SYSTEM_PROPERTY_PREFIX "persist.device_config."
33 
34 #define ATTEMPTED_BOOT_COUNT_PROPERTY "persist.device_config.attempted_boot_count"
35 
36 #define RESET_PERFORMED_PROPERTY "device_config.reset_performed"
37 
38 #define RESET_FLAGS_FILE_PATH "/data/server_configurable_flags/reset_flags"
39 
40 #define ATTEMPTED_BOOT_COUNT_THRESHOLD 4
41 
42 namespace server_configurable_flags {
43 
44 static const std::regex NAME_VALID_CHARACTER_REGIX("^[\\w\\.\\-@:]*$");
45 
46 static std::string MakeSystemPropertyName(const std::string& experiment_category_name,
47                                           const std::string& experiment_flag_name) {
48   return SYSTEM_PROPERTY_PREFIX + experiment_category_name + "." + experiment_flag_name;
49 }
50 
51 static bool ValidateExperimentSegment(const std::string& segment) {
52   return std::regex_match(segment, NAME_VALID_CHARACTER_REGIX) && segment.find(".") != 0 &&
53          segment.find(".") != segment.size() - 1;
54 }
55 
56 #if defined(__BIONIC__)
57 static void ResetFlag(const char* key, const char* value, void* cookie) {
58   if (strcmp(ATTEMPTED_BOOT_COUNT_PROPERTY, key) &&
59       android::base::StartsWith(key, SYSTEM_PROPERTY_PREFIX) && strlen(value) > 0 &&
60       android::base::SetProperty(key, "")) {
61     std::string* reset_flags = static_cast<std::string*>(cookie);
62     if (reset_flags->length() > 0) {
63       reset_flags->append(";");
64     }
65     reset_flags->append(key);
66     android::base::SetProperty(RESET_PERFORMED_PROPERTY, "true");
67   }
68 }
69 
70 // Reset all system properties used as flags into empty value,
71 // and record reset flags' names in /data/server_configurable_flags/reset_flags
72 static void ResetAllFlags() {
73   std::string reset_flags;
74   property_list(ResetFlag, &reset_flags);
75 
76   if (reset_flags.length() > 0) {
77     android::base::unique_fd fd(
78         TEMP_FAILURE_RETRY(open(RESET_FLAGS_FILE_PATH, O_RDWR | O_CREAT | O_TRUNC, 0666)));
79     if (fd == -1) {
80       LOG(INFO) << __FUNCTION__ << " failed to open file " << RESET_FLAGS_FILE_PATH;
81     } else if (!WriteStringToFd(reset_flags, fd)) {
82       LOG(INFO) << __FUNCTION__ << " failed to write file " << RESET_FLAGS_FILE_PATH;
83     } else {
84       LOG(INFO) << __FUNCTION__ << " successfully write to file " << RESET_FLAGS_FILE_PATH;
85     }
86   }
87 }
88 #endif  // __BIONIC__
89 
90 void ServerConfigurableFlagsReset(ResetMode reset_mode) {
91   LOG(INFO) << __FUNCTION__ << " reset_mode value: " << reset_mode;
92 #if defined(__BIONIC__)
93   if (reset_mode == BOOT_FAILURE) {
94     int fail_count = android::base::GetIntProperty(ATTEMPTED_BOOT_COUNT_PROPERTY, 0);
95     if (fail_count < ATTEMPTED_BOOT_COUNT_THRESHOLD) {
96       LOG(INFO) << __FUNCTION__ << " attempted boot count is under threshold, skipping reset.";
97 
98       // ATTEMPTED_BOOT_COUNT_PROPERTY will be reset to 0 when sys.boot_completed is set to 1.
99       // The code lives in flags_health_check.rc.
100       android::base::SetProperty(ATTEMPTED_BOOT_COUNT_PROPERTY, std::to_string(fail_count + 1));
101     } else {
102       LOG(INFO) << __FUNCTION__ << " attempted boot count reaches threshold, resetting flags.";
103       ResetAllFlags();
104     }
105   } else if (reset_mode == UPDATABLE_CRASHING) {
106     LOG(INFO) << __FUNCTION__ << " updatable crashing detected, resetting flags.";
107     ResetAllFlags();
108   } else {
109     LOG(ERROR) << __FUNCTION__ << " invalid reset_mode, skipping reset.";
110   }
111 #else
112   LOG(ERROR) << __FUNCTION__ << " ServerConfigurableFlagsReset is not available for this build.";
113 #endif  // __BIONIC__
114 }
115 
116 std::string GetServerConfigurableFlag(const std::string& experiment_category_name,
117                                       const std::string& experiment_flag_name,
118                                       const std::string& default_value) {
119   if (!ValidateExperimentSegment(experiment_category_name)) {
120     LOG(ERROR) << __FUNCTION__ << " invalid category name " << experiment_category_name;
121     return default_value;
122   }
123   if (!ValidateExperimentSegment(experiment_flag_name)) {
124     LOG(ERROR) << __FUNCTION__ << " invalid flag name " << experiment_flag_name;
125     return default_value;
126   }
127   return android::base::GetProperty(
128       MakeSystemPropertyName(experiment_category_name, experiment_flag_name), default_value);
129 }
130 
131 }  // namespace server_configurable_flags
132