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[esphome] Fix OTA watchdog resets by validating all magic bytes before blocking (#10401)

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This commit is contained in:
J. Nick Koston
2025-08-28 17:12:38 -05:00
committed by Jesse Hills
parent 015977cfdf
commit ba4789970c
2 changed files with 45 additions and 40 deletions
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77
esphome/components/esphome/ota/ota_esphome.cpp
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@@ -100,8 +100,8 @@ void ESPHomeOTAComponent::handle_handshake_() {
/// Handle the initial OTA handshake.
///
/// This method is non-blocking and will return immediately if no data is available.
/// It waits for the first magic byte (0x6C) before proceeding to handle_data_().
/// A 10-second timeout is enforced from initial connection.
/// It reads all 5 magic bytes (0x6C, 0x26, 0xF7, 0x5C, 0x45) non-blocking
/// before proceeding to handle_data_(). A 10-second timeout is enforced from initial connection.
if (this->client_ == nullptr) {
// We already checked server_->ready() in loop(), so we can accept directly
@@ -126,6 +126,7 @@ void ESPHomeOTAComponent::handle_handshake_() {
}
this->log_start_("handshake");
this->client_connect_time_ = App.get_loop_component_start_time();
this->magic_buf_pos_ = 0; // Reset magic buffer position
}
// Check for handshake timeout
@@ -136,34 +137,47 @@ void ESPHomeOTAComponent::handle_handshake_() {
return;
}
// Try to read first byte of magic bytes
uint8_t first_byte;
ssize_t read = this->client_->read(&first_byte, 1);
// Try to read remaining magic bytes
if (this->magic_buf_pos_ < 5) {
// Read as many bytes as available
uint8_t bytes_to_read = 5 - this->magic_buf_pos_;
ssize_t read = this->client_->read(this->magic_buf_ + this->magic_buf_pos_, bytes_to_read);
if (read == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
return; // No data yet, try again next loop
}
if (read <= 0) {
// Error or connection closed
if (read == -1) {
this->log_socket_error_("reading first byte");
} else {
ESP_LOGW(TAG, "Remote closed during handshake");
if (read == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
return; // No data yet, try again next loop
}
this->cleanup_connection_();
return;
if (read <= 0) {
// Error or connection closed
if (read == -1) {
this->log_socket_error_("reading magic bytes");
} else {
ESP_LOGW(TAG, "Remote closed during handshake");
}
this->cleanup_connection_();
return;
}
this->magic_buf_pos_ += read;
}
// Got first byte, check if it's the magic byte
if (first_byte != 0x6C) {
ESP_LOGW(TAG, "Invalid initial byte: 0x%02X", first_byte);
this->cleanup_connection_();
return;
}
// Check if we have all 5 magic bytes
if (this->magic_buf_pos_ == 5) {
// Validate magic bytes
static const uint8_t MAGIC_BYTES[5] = {0x6C, 0x26, 0xF7, 0x5C, 0x45};
if (memcmp(this->magic_buf_, MAGIC_BYTES, 5) != 0) {
ESP_LOGW(TAG, "Magic bytes mismatch! 0x%02X-0x%02X-0x%02X-0x%02X-0x%02X", this->magic_buf_[0],
this->magic_buf_[1], this->magic_buf_[2], this->magic_buf_[3], this->magic_buf_[4]);
// Send error response (non-blocking, best effort)
uint8_t error = static_cast<uint8_t>(ota::OTA_RESPONSE_ERROR_MAGIC);
this->client_->write(&error, 1);
this->cleanup_connection_();
return;
}
// First byte is valid, continue with data handling
this->handle_data_();
// All 5 magic bytes are valid, continue with data handling
this->handle_data_();
}
}
void ESPHomeOTAComponent::handle_data_() {
@@ -186,18 +200,6 @@ void ESPHomeOTAComponent::handle_data_() {
size_t size_acknowledged = 0;
#endif
// Read remaining 4 bytes of magic (we already read the first byte 0x6C in handle_handshake_)
if (!this->readall_(buf, 4)) {
this->log_read_error_("magic bytes");
goto error; // NOLINT(cppcoreguidelines-avoid-goto)
}
// Check remaining magic bytes: 0x26, 0xF7, 0x5C, 0x45
if (buf[0] != 0x26 || buf[1] != 0xF7 || buf[2] != 0x5C || buf[3] != 0x45) {
ESP_LOGW(TAG, "Magic bytes mismatch! 0x6C-0x%02X-0x%02X-0x%02X-0x%02X", buf[0], buf[1], buf[2], buf[3]);
error_code = ota::OTA_RESPONSE_ERROR_MAGIC;
goto error; // NOLINT(cppcoreguidelines-avoid-goto)
}
// Send OK and version - 2 bytes
buf[0] = ota::OTA_RESPONSE_OK;
buf[1] = USE_OTA_VERSION;
@@ -487,6 +489,7 @@ void ESPHomeOTAComponent::cleanup_connection_() {
this->client_->close();
this->client_ = nullptr;
this->client_connect_time_ = 0;
this->magic_buf_pos_ = 0;
}
void ESPHomeOTAComponent::yield_and_feed_watchdog_() {

8
esphome/components/esphome/ota/ota_esphome.h
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@@ -41,11 +41,13 @@ class ESPHomeOTAComponent : public ota::OTAComponent {
std::string password_;
#endif // USE_OTA_PASSWORD
uint16_t port_;
uint32_t client_connect_time_{0};
std::unique_ptr<socket::Socket> server_;
std::unique_ptr<socket::Socket> client_;
uint32_t client_connect_time_{0};
uint16_t port_;
uint8_t magic_buf_[5];
uint8_t magic_buf_pos_{0};
};
} // namespace esphome