blob: 658bf416d849f18fe65c7d5da240a46b17be9e82 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
/*
**
** Copyright 2018, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
#ifndef KEYSTORE_CONFIRMATIONUI_RATE_LIMITING_H_
#define KEYSTORE_CONFIRMATIONUI_RATE_LIMITING_H_
#include <android/hardware/confirmationui/1.0/types.h>
#include <chrono>
#include <stdint.h>
#include <sys/types.h>
#include <tuple>
#include <unordered_map>
namespace keystore {
using ConfirmationResponseCode = android::hardware::confirmationui::V1_0::ResponseCode;
using std::chrono::duration;
using std::chrono::time_point;
template <typename Clock = std::chrono::steady_clock> class RateLimiting {
private:
struct Slot {
Slot() : previous_start{}, prompt_start{}, counter(0) {}
typename Clock::time_point previous_start;
typename Clock::time_point prompt_start;
uint32_t counter;
};
std::unordered_map<uid_t, Slot> slots_;
uint_t latest_requester_;
static std::chrono::seconds getBackoff(uint32_t counter) {
using namespace std::chrono_literals;
switch (counter) {
case 0:
case 1:
case 2:
return 0s;
case 3:
case 4:
case 5:
return 30s;
default:
return 60s * (1ULL << (counter - 6));
}
}
public:
// Exposes the number of used slots. This is only used by the test to verify the assumption
// about used counter slots.
size_t usedSlots() const { return slots_.size(); }
void doGC() {
using namespace std::chrono_literals;
using std::chrono::system_clock;
using std::chrono::time_point_cast;
auto then = Clock::now() - 24h;
auto iter = slots_.begin();
while (iter != slots_.end()) {
if (iter->second.prompt_start <= then) {
iter = slots_.erase(iter);
} else {
++iter;
}
}
}
bool tryPrompt(uid_t id) {
using namespace std::chrono_literals;
// remove slots that have not been touched in 24 hours
doGC();
auto& slot = slots_[id];
auto now = Clock::now();
if (!slot.counter || slot.prompt_start <= now - getBackoff(slot.counter)) {
latest_requester_ = id;
slot.counter += 1;
slot.previous_start = slot.prompt_start;
slot.prompt_start = now;
return true;
}
return false;
}
// The app is penalized for cancelling a request. Request are rolled back only if
// the prompt was cancelled by the system: e.g. a system error or asynchronous event.
// When the user cancels the prompt, it is subject to rate limiting.
static constexpr const uint_t kInvalidRequester = -1;
void cancelPrompt() { latest_requester_ = kInvalidRequester; }
void processResult(ConfirmationResponseCode rc) {
if (latest_requester_ == kInvalidRequester) {
return;
}
switch (rc) {
case ConfirmationResponseCode::OK:
// reset the counter slot
slots_.erase(latest_requester_);
return;
case ConfirmationResponseCode::Canceled:
// nothing to do here
return;
default:;
}
// roll back latest request
auto& slot = slots_[latest_requester_];
if (slot.counter <= 1) {
slots_.erase(latest_requester_);
return;
}
slot.counter -= 1;
slot.prompt_start = slot.previous_start;
}
};
} // namespace keystore
#endif // KEYSTORE_CONFIRMATIONUI_RATE_LIMITING_H_
|
