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[modbus] Fix buffer overflow in modbus (#14719)

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Co-authored-by: J. Nick Koston <nick@home-assistant.io>
This commit is contained in:
Adam DeMuri
2026-03-12 02:00:26 -06:00
committed by GitHub
parent f8a22b87b8
commit 8a5f008aee
2 changed files with 65 additions and 6 deletions
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tests/components/modbus/modbus_test.cpp
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#include <gtest/gtest.h>
#include "esphome/components/modbus/modbus.h"
#include "esphome/core/helpers.h"
namespace esphome::modbus {
// Exposes protected methods for testing.
class TestModbus : public Modbus {
public:
bool test_parse_modbus_byte(uint8_t byte) { return this->parse_modbus_byte_(byte); }
void test_clear_rx_buffer() { this->rx_buffer_.clear(); }
void set_waiting(uint8_t addr) { this->waiting_for_response_ = addr; }
};
class MockDevice : public ModbusDevice {
public:
void on_modbus_data(const std::vector<uint8_t> &data) override { this->data_received = true; }
bool data_received{false};
};
TEST(ModbusTest, TwoByteRegressionTest) {
TestModbus modbus;
modbus.set_role(ModbusRole::CLIENT);
// First byte (at=0)
EXPECT_TRUE(modbus.test_parse_modbus_byte(0x01));
// Second byte (at=1)
// This used to reach raw[2] because it skipped the if(at==2) check, causing a
// buffer overflow.
EXPECT_TRUE(modbus.test_parse_modbus_byte(0x03));
}
TEST(ModbusTest, TestValidFrame) {
TestModbus modbus;
modbus.set_role(ModbusRole::CLIENT);
MockDevice device;
device.set_parent(&modbus);
device.set_address(0x01);
modbus.register_device(&device);
modbus.set_waiting(0x01);
// Address 1, Function 3, Length 2, Data 0x1234
uint8_t frame_data[] = {0x01, 0x03, 0x02, 0x12, 0x34};
uint16_t crc = esphome::crc16(frame_data, sizeof(frame_data));
std::vector<uint8_t> frame;
for (uint8_t b : frame_data)
frame.push_back(b);
frame.push_back(crc & 0xFF);
frame.push_back((crc >> 8) & 0xFF);
for (size_t i = 0; i < frame.size(); i++) {
bool result = modbus.test_parse_modbus_byte(frame[i]);
EXPECT_TRUE(result) << "Failed at byte " << i << " (0x" << std::hex << (int) frame[i] << ")";
}
EXPECT_TRUE(device.data_received);
}
} // namespace esphome::modbus