Function Open

internal/dmverity/dmverity_linux.go:126–188

Open creates a read-only device-mapper target for transparent integrity verification. It supports both superblock and no-superblock modes: - Superblock mode (opts == nil or opts.NoSuperblock == false): Reads dm-verity parameters from the superblock at the specified hashOffset. Only rootHash needs t

(dataDevice string, name string, hashDevice string, rootHash string, hashOffset uint64, opts *DmverityOptions)

//     Uses explicitly provided parameters from opts. All dm-verity parameters must be
//     supplied programmatically since there's no superblock to read from.
func Open(dataDevice string, name string, hashDevice string, rootHash string, hashOffset uint64, opts *DmverityOptions) (string, error) {
	if rootHash == "" {
		return "", fmt.Errorf("rootHash cannot be empty")
	}

	rootDigest, err := utils.ParseRootHash(rootHash)
	if err != nil {
		return "", fmt.Errorf("invalid root hash: %w", err)
	}

	var params verity.Params

	if opts != nil && opts.NoSuperblock {
		params, err = convertToVerityParams(opts)
		if err != nil {
			return "", fmt.Errorf("failed to convert options: %w", err)
		}
	} else {
		params = verity.DefaultParams()
		params.HashAreaOffset = hashOffset
	}

	loopParams := mount.LoopParams{
		Readonly:  true,
		Autoclear: true,
	}

	dataLoop, err := mount.SetupLoop(dataDevice, loopParams)
	if err != nil {
		return "", fmt.Errorf("failed to setup loop device for data: %w", err)
	}
	dataLoopDevice := dataLoop.Name()

	var hashLoop *os.File
	var hashLoopDevice string
	if hashDevice != dataDevice {
		hashLoop, err = mount.SetupLoop(hashDevice, loopParams)
		if err != nil {
			dataLoop.Close()
			return "", fmt.Errorf("failed to setup loop device for hash: %w", err)
		}
		hashLoopDevice = hashLoop.Name()
	} else {
		hashLoopDevice = dataLoopDevice
	}

	devicePath, err := verity.Open(&params, name, dataLoopDevice, hashLoopDevice, rootDigest, "", nil)
	if err != nil {
		dataLoop.Close()
		if hashLoop != nil {
			hashLoop.Close()
		}
		return "", fmt.Errorf("failed to open dm-verity device: %w", err)
	}

	// Close file handles now that dm-verity holds a kernel reference to the loop devices.
	dataLoop.Close()
	if hashLoop != nil {