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fix: guard time token arithmetic against overflow #24

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Merged
LimiNode merged 1 commit into from
Sep 3, 2025
Merged

fix: guard time token arithmetic against overflow #24

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20 changes: 14 additions & 6 deletions hmac_utils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,8 +36,12 @@ namespace hmac {
}
std::time_t rounded = (now / interval_sec) * interval_sec;
if (constant_time_equals(token, get_hmac(key, std::to_string(rounded), hash_type))) return true;
if (constant_time_equals(token, get_hmac(key, std::to_string(rounded - interval_sec), hash_type))) return true;
if (constant_time_equals(token, get_hmac(key, std::to_string(rounded + interval_sec), hash_type))) return true;
if (rounded >= std::numeric_limits<std::time_t>::min() + interval_sec) {
if (constant_time_equals(token, get_hmac(key, std::to_string(rounded - interval_sec), hash_type))) return true;
}
if (rounded <= std::numeric_limits<std::time_t>::max() - interval_sec) {
if (constant_time_equals(token, get_hmac(key, std::to_string(rounded + interval_sec), hash_type))) return true;
}
return false;
}

Expand Down Expand Up @@ -66,10 +70,14 @@ namespace hmac {
std::string prefix = "|" + fingerprint;
std::string payload = std::to_string(rounded) + prefix;
if (constant_time_equals(token, get_hmac(key, payload, hash_type))) return true;
payload = std::to_string(rounded - interval_sec) + prefix;
if (constant_time_equals(token, get_hmac(key, payload, hash_type))) return true;
payload = std::to_string(rounded + interval_sec) + prefix;
if (constant_time_equals(token, get_hmac(key, payload, hash_type))) return true;
if (rounded >= std::numeric_limits<std::time_t>::min() + interval_sec) {
payload = std::to_string(rounded - interval_sec) + prefix;
if (constant_time_equals(token, get_hmac(key, payload, hash_type))) return true;
}
if (rounded <= std::numeric_limits<std::time_t>::max() - interval_sec) {
payload = std::to_string(rounded + interval_sec) + prefix;
if (constant_time_equals(token, get_hmac(key, payload, hash_type))) return true;
}
return false;
}

Expand Down
57 changes: 57 additions & 0 deletions test_all.cpp
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Original file line number Diff line number Diff line change
@@ -1,9 +1,16 @@
#include <gtest/gtest.h>
#include <string>
#include <stdexcept>
#include <limits>
#include "hmac.hpp"
#include "hmac_utils.hpp"

static std::time_t mock_time_value = 0;
extern "C" std::time_t time(std::time_t* t) {
if (t) *t = mock_time_value;
return mock_time_value;
}

TEST(HashTest, SHA1) {
EXPECT_EQ(hmac_hash::sha1("grape"),
"bc8a2f8cdedb005b5c787692853709b060db75ff");
Expand Down Expand Up @@ -65,6 +72,56 @@ TEST(TokenTest, InvalidInterval) {
EXPECT_THROW(hmac::is_token_valid(token, key, 0), std::invalid_argument);
}

TEST(TokenBoundaryTest, MaxTime) {
const std::string key = "12345";
const int interval = 30;
mock_time_value = std::numeric_limits<std::time_t>::max();
std::string token = hmac::generate_time_token(key, interval);
EXPECT_TRUE(hmac::is_token_valid(token, key, interval));
mock_time_value = std::numeric_limits<std::time_t>::max() - interval;
std::string token_prev = hmac::generate_time_token(key, interval);
mock_time_value = std::numeric_limits<std::time_t>::max();
EXPECT_TRUE(hmac::is_token_valid(token_prev, key, interval));
}

TEST(TokenBoundaryTest, MinTime) {
const std::string key = "12345";
const int interval = 30;
mock_time_value = std::numeric_limits<std::time_t>::min();
std::string token = hmac::generate_time_token(key, interval);
EXPECT_TRUE(hmac::is_token_valid(token, key, interval));
mock_time_value = std::numeric_limits<std::time_t>::min() + interval;
std::string token_next = hmac::generate_time_token(key, interval);
mock_time_value = std::numeric_limits<std::time_t>::min();
EXPECT_TRUE(hmac::is_token_valid(token_next, key, interval));
}

TEST(TokenBoundaryFingerprintTest, MaxTime) {
const std::string key = "12345";
const std::string fingerprint = "fp";
const int interval = 30;
mock_time_value = std::numeric_limits<std::time_t>::max();
std::string token = hmac::generate_time_token(key, fingerprint, interval);
EXPECT_TRUE(hmac::is_token_valid(token, key, fingerprint, interval));
mock_time_value = std::numeric_limits<std::time_t>::max() - interval;
std::string token_prev = hmac::generate_time_token(key, fingerprint, interval);
mock_time_value = std::numeric_limits<std::time_t>::max();
EXPECT_TRUE(hmac::is_token_valid(token_prev, key, fingerprint, interval));
}

TEST(TokenBoundaryFingerprintTest, MinTime) {
const std::string key = "12345";
const std::string fingerprint = "fp";
const int interval = 30;
mock_time_value = std::numeric_limits<std::time_t>::min();
std::string token = hmac::generate_time_token(key, fingerprint, interval);
EXPECT_TRUE(hmac::is_token_valid(token, key, fingerprint, interval));
mock_time_value = std::numeric_limits<std::time_t>::min() + interval;
std::string token_next = hmac::generate_time_token(key, fingerprint, interval);
mock_time_value = std::numeric_limits<std::time_t>::min();
EXPECT_TRUE(hmac::is_token_valid(token_next, key, fingerprint, interval));
}

int main(int argc, char **argv) {
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
Expand Down
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