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[modbus] Simplify payload size validation in modbus_helpers (#15838)

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This commit is contained in:
Rui Marinho
2026-04-20 14:24:07 +01:00
committed by GitHub
parent 73b8e8ac09
commit b72f5447c3
2 changed files with 79 additions and 57 deletions
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esphome/components/modbus/modbus_helpers.cpp
+57 -57
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@@ -5,6 +5,29 @@ namespace esphome::modbus::helpers {
static const char *const TAG = "modbus_helpers";
static size_t required_payload_size(SensorValueType sensor_value_type) {
switch (sensor_value_type) {
case SensorValueType::U_WORD:
case SensorValueType::S_WORD:
return 2;
case SensorValueType::U_DWORD:
case SensorValueType::FP32:
case SensorValueType::U_DWORD_R:
case SensorValueType::FP32_R:
case SensorValueType::S_DWORD:
case SensorValueType::S_DWORD_R:
return 4;
case SensorValueType::U_QWORD:
case SensorValueType::S_QWORD:
case SensorValueType::U_QWORD_R:
case SensorValueType::S_QWORD_R:
return 8;
case SensorValueType::RAW:
default:
return 0;
}
}
void number_to_payload(std::vector<uint16_t> &data, int64_t value, SensorValueType value_type) {
switch (value_type) {
case SensorValueType::U_WORD:
@@ -47,93 +70,70 @@ int64_t payload_to_number(const std::vector<uint8_t> &data, SensorValueType sens
uint32_t bitmask) {
int64_t value = 0; // int64_t because it can hold signed and unsigned 32 bits
if (offset > data.size()) {
ESP_LOGE(TAG, "not enough data for value");
// Validate offset against the buffer for all types, including RAW/unsupported, so
// a malformed or misconfigured frame still produces an error log.
if (static_cast<size_t>(offset) > data.size()) {
ESP_LOGE(TAG, "not enough data for value type=%u offset=%u size=%zu", static_cast<unsigned int>(sensor_value_type),
static_cast<unsigned int>(offset), data.size());
return value;
}
const size_t required_size = required_payload_size(sensor_value_type);
if (required_size == 0) {
return value;
}
if (data.size() - offset < required_size) {
ESP_LOGE(TAG, "not enough data for value type=%u offset=%u size=%zu required=%zu",
static_cast<unsigned int>(sensor_value_type), static_cast<unsigned int>(offset), data.size(),
required_size);
return value;
}
size_t size = data.size() - offset;
bool error = false;
switch (sensor_value_type) {
case SensorValueType::U_WORD:
if (size >= 2) {
value = mask_and_shift_by_rightbit(get_data<uint16_t>(data, offset),
bitmask); // default is 0xFFFF ;
} else {
error = true;
}
value = mask_and_shift_by_rightbit(get_data<uint16_t>(data, offset), bitmask); // default is 0xFFFF ;
break;
case SensorValueType::U_DWORD:
case SensorValueType::FP32:
if (size >= 4) {
value = get_data<uint32_t>(data, offset);
value = mask_and_shift_by_rightbit((uint32_t) value, bitmask);
} else {
error = true;
}
value = get_data<uint32_t>(data, offset);
value = mask_and_shift_by_rightbit((uint32_t) value, bitmask);
break;
case SensorValueType::U_DWORD_R:
case SensorValueType::FP32_R:
if (size >= 4) {
value = get_data<uint32_t>(data, offset);
value = static_cast<uint32_t>(value & 0xFFFF) << 16 | (value & 0xFFFF0000) >> 16;
value = mask_and_shift_by_rightbit((uint32_t) value, bitmask);
} else {
error = true;
}
value = get_data<uint32_t>(data, offset);
value = static_cast<uint32_t>(value & 0xFFFF) << 16 | (value & 0xFFFF0000) >> 16;
value = mask_and_shift_by_rightbit((uint32_t) value, bitmask);
break;
case SensorValueType::S_WORD:
if (size >= 2) {
value = mask_and_shift_by_rightbit(get_data<int16_t>(data, offset),
bitmask); // default is 0xFFFF ;
} else {
error = true;
}
value = mask_and_shift_by_rightbit(get_data<int16_t>(data, offset), bitmask); // default is 0xFFFF ;
break;
case SensorValueType::S_DWORD:
if (size >= 4) {
value = mask_and_shift_by_rightbit(get_data<int32_t>(data, offset), bitmask);
} else {
error = true;
}
value = mask_and_shift_by_rightbit(get_data<int32_t>(data, offset), bitmask);
break;
case SensorValueType::S_DWORD_R: {
if (size >= 4) {
value = get_data<uint32_t>(data, offset);
// Currently the high word is at the low position
// the sign bit is therefore at low before the switch
uint32_t sign_bit = (value & 0x8000) << 16;
value = mask_and_shift_by_rightbit(
static_cast<int32_t>(((value & 0x7FFF) << 16 | (value & 0xFFFF0000) >> 16) | sign_bit), bitmask);
} else {
error = true;
}
value = get_data<uint32_t>(data, offset);
// Currently the high word is at the low position
// the sign bit is therefore at low before the switch
uint32_t sign_bit = (value & 0x8000) << 16;
value = mask_and_shift_by_rightbit(
static_cast<int32_t>(((value & 0x7FFF) << 16 | (value & 0xFFFF0000) >> 16) | sign_bit), bitmask);
} break;
case SensorValueType::U_QWORD:
case SensorValueType::S_QWORD:
// Ignore bitmask for QWORD
if (size >= 8) {
value = get_data<uint64_t>(data, offset);
} else {
error = true;
}
value = get_data<uint64_t>(data, offset);
break;
case SensorValueType::U_QWORD_R:
case SensorValueType::S_QWORD_R: {
// Ignore bitmask for QWORD
if (size >= 8) {
uint64_t tmp = get_data<uint64_t>(data, offset);
value = (tmp << 48) | (tmp >> 48) | ((tmp & 0xFFFF0000) << 16) | ((tmp >> 16) & 0xFFFF0000);
} else {
error = true;
}
uint64_t tmp = get_data<uint64_t>(data, offset);
value = (tmp << 48) | (tmp >> 48) | ((tmp & 0xFFFF0000) << 16) | ((tmp >> 16) & 0xFFFF0000);
} break;
case SensorValueType::RAW:
default:
break;
}
if (error)
ESP_LOGE(TAG, "not enough data for value");
return value;
}
} // namespace esphome::modbus::helpers
tests/components/modbus/modbus_helpers_test.cpp
+22
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@@ -0,0 +1,22 @@
#include <gtest/gtest.h>
#include "esphome/components/modbus/modbus_helpers.h"
namespace esphome::modbus::helpers {
TEST(ModbusHelpersTest, PayloadToNumberRejectsOffsetAtEndOfBuffer) {
const std::vector<uint8_t> data{0x12, 0x34};
EXPECT_EQ(payload_to_number(data, SensorValueType::U_WORD, 2, 0xFFFFFFFF), 0);
}
TEST(ModbusHelpersTest, PayloadToNumberRejectsTruncatedMultiRegisterValue) {
const std::vector<uint8_t> data{0x12, 0x34, 0x56};
EXPECT_EQ(payload_to_number(data, SensorValueType::U_DWORD, 0, 0xFFFFFFFF), 0);
}
TEST(ModbusHelpersTest, PayloadToNumberDecodesValidWord) {
const std::vector<uint8_t> data{0x12, 0x34};
EXPECT_EQ(payload_to_number(data, SensorValueType::U_WORD, 0, 0xFFFFFFFF), 0x1234);
}
} // namespace esphome::modbus::helpers