Exception Message Truncation on Windows

[devgc]

On Windows, dfvfs Exceptions can contain messages with returns but without the new line character. This can lead to message truncation when exceptions are thrown.

If I run the following on an image that errors out during the source scanner's Scan:

import sys
from dfvfs.helpers import source_scanner


def main():
    source = sys.argv[1]
    scan_path_spec = None
    scanner = source_scanner.SourceScanner()
    scan_context = source_scanner.SourceScannerContext()
    scan_context.OpenSourcePath(source)

    try:
        scanner.Scan(
            scan_context,
            scan_path_spec=scan_path_spec
        )
    except Exception as error:
        print("---------------------------------------------")
        print("Error Message Without Replacing Returns")
        print(r'print(error)')
        print("---------------------------------------------")
        print(error)
        print("")
        print("")
        print("---------------------------------------------")
        print("Error Message With Replacing Returns")
        print(r'print(str(error).replace("\r", "\n"))')
        print("---------------------------------------------")
        print(str(error).replace("\r", "\n"))
        print("")
        print("")
        print("---------------------------------------------")
        print("On Raise")
        print(r'raise error')
        print("---------------------------------------------")
        raise error


if __name__ == "__main__":
    main()

I get the following output:

---------------------------------------------
Error Message Without Replacing Returns
print(error)
---------------------------------------------
 libbde_volume_open_file_io_handle: unable to read from file IO handle.ntry_read: unsupported FVE metadata entry version.


---------------------------------------------
Error Message With Replacing Returns
print(str(error).replace("\r", "\n"))
---------------------------------------------
pybde_volume_open_file_object: unable to open volume. libbde_metadata_entry_read: unsupported FVE metadata entry version.
 libbde_metadata_read_entries: unable to read metadata entry.
 libbde_metadata_read_block: unable to read metadata header.
 libbde_volume_open_read: unable to read primary metadata block.
 libbde_volume_open_file_io_handle: unable to read from file IO handle.


---------------------------------------------
On Raise
raise error
---------------------------------------------
Traceback (most recent call last):
  File "error_truncation.py", line 40, in <module>
    main()
  File "error_truncation.py", line 36, in main
    raise error
 libbde_volume_open_file_io_handle: unable to read from file IO handle.etadata_entry_read: unsupported FVE metadata entry version.

It has helped me out in some situations to see the extended message, so, I thought I would put it here. Hope this info might help someone else.

[joachimmetz]

The end of line on windows should be '\r\n' https://github.com/libyal/libcerror/blob/master/libcerror/libcerror_error.c#L757

The library error is then transformed into a Python error string https://github.com/libyal/libbde/blob/master/pybde/pybde_error.c#L145

I'll see if I can reproduce this and see if it is some underlying issue.

[joachimmetz]

@devgc which version of libbde did you use in your tests?

[devgc]

I believe it was 20190102. Generally I install from what is available at https://github.com/log2timeline/l2tbinaries/tree/master/win64. But since this error, I have updated to a newer version.

[joachimmetz]

I'll need to have a closer look at this when time permits.