Janis Danisevskis | 064ce85 | 2018-03-12 16:49:16 -0700 | [diff] [blame] | 1 | /* |
| 2 | ** |
| 3 | ** Copyright 2018, The Android Open Source Project |
| 4 | ** |
| 5 | ** Licensed under the Apache License, Version 2.0 (the "License"); |
| 6 | ** you may not use this file except in compliance with the License. |
| 7 | ** You may obtain a copy of the License at |
| 8 | ** |
| 9 | ** http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | ** |
| 11 | ** Unless required by applicable law or agreed to in writing, software |
| 12 | ** distributed under the License is distributed on an "AS IS" BASIS, |
| 13 | ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 14 | ** See the License for the specific language governing permissions and |
| 15 | ** limitations under the License. |
| 16 | */ |
| 17 | |
| 18 | #ifndef KEYSTORE_CONFIRMATIONUI_RATE_LIMITING_H_ |
| 19 | #define KEYSTORE_CONFIRMATIONUI_RATE_LIMITING_H_ |
| 20 | |
| 21 | #include <android/hardware/confirmationui/1.0/types.h> |
| 22 | #include <chrono> |
| 23 | #include <stdint.h> |
| 24 | #include <sys/types.h> |
| 25 | #include <tuple> |
| 26 | #include <unordered_map> |
| 27 | |
| 28 | namespace keystore { |
| 29 | |
| 30 | using ConfirmationResponseCode = android::hardware::confirmationui::V1_0::ResponseCode; |
| 31 | |
| 32 | using std::chrono::time_point; |
| 33 | using std::chrono::duration; |
| 34 | |
| 35 | template <typename Clock = std::chrono::steady_clock> class RateLimiting { |
| 36 | private: |
| 37 | struct Slot { |
| 38 | Slot() : previous_start{}, prompt_start{}, counter(0) {} |
| 39 | typename Clock::time_point previous_start; |
| 40 | typename Clock::time_point prompt_start; |
| 41 | uint32_t counter; |
| 42 | }; |
| 43 | |
| 44 | std::unordered_map<uid_t, Slot> slots_; |
| 45 | |
| 46 | uint_t latest_requester_; |
| 47 | |
| 48 | static std::chrono::seconds getBackoff(uint32_t counter) { |
| 49 | using namespace std::chrono_literals; |
| 50 | switch (counter) { |
| 51 | case 0: |
| 52 | case 1: |
| 53 | case 2: |
| 54 | return 0s; |
| 55 | case 3: |
| 56 | case 4: |
| 57 | case 5: |
| 58 | return 30s; |
| 59 | default: |
| 60 | return 60s * (1ULL << (counter - 6)); |
| 61 | } |
| 62 | } |
| 63 | |
| 64 | public: |
| 65 | // Exposes the number of used slots. This is only used by the test to verify the assumption |
| 66 | // about used counter slots. |
| 67 | size_t usedSlots() const { return slots_.size(); } |
| 68 | void doGC() { |
| 69 | using namespace std::chrono_literals; |
| 70 | using std::chrono::system_clock; |
| 71 | using std::chrono::time_point_cast; |
| 72 | auto then = Clock::now() - 24h; |
| 73 | auto iter = slots_.begin(); |
| 74 | while (iter != slots_.end()) { |
| 75 | if (iter->second.prompt_start <= then) { |
| 76 | iter = slots_.erase(iter); |
| 77 | } else { |
| 78 | ++iter; |
| 79 | } |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | bool tryPrompt(uid_t id) { |
| 84 | using namespace std::chrono_literals; |
| 85 | // remove slots that have not been touched in 24 hours |
| 86 | doGC(); |
| 87 | auto& slot = slots_[id]; |
| 88 | auto now = Clock::now(); |
| 89 | if (!slot.counter || slot.prompt_start <= now - getBackoff(slot.counter)) { |
| 90 | latest_requester_ = id; |
| 91 | slot.counter += 1; |
| 92 | slot.previous_start = slot.prompt_start; |
| 93 | slot.prompt_start = now; |
| 94 | return true; |
| 95 | } |
| 96 | return false; |
| 97 | } |
| 98 | |
| 99 | void processResult(ConfirmationResponseCode rc) { |
| 100 | switch (rc) { |
| 101 | case ConfirmationResponseCode::OK: |
| 102 | // reset the counter slot |
| 103 | slots_.erase(latest_requester_); |
| 104 | return; |
| 105 | case ConfirmationResponseCode::Canceled: |
| 106 | // nothing to do here |
| 107 | return; |
| 108 | default:; |
| 109 | } |
| 110 | |
| 111 | // roll back latest request |
| 112 | auto& slot = slots_[latest_requester_]; |
| 113 | if (slot.counter <= 1) { |
| 114 | slots_.erase(latest_requester_); |
| 115 | return; |
| 116 | } |
| 117 | slot.counter -= 1; |
| 118 | slot.prompt_start = slot.previous_start; |
| 119 | } |
| 120 | }; |
| 121 | |
| 122 | } // namespace keystore |
| 123 | |
| 124 | #endif // KEYSTORE_CONFIRMATIONUI_RATE_LIMITING_H_ |