[PATCH] s3:loadparm: Ensure to truncate FS Volume Label at multibyte boundary

[Shyam Rathi]

https://bugzilla.samba.org/show_bug.cgi?id=13947


To reproduce, create a share with a name where 32nd byte is not the first byte of a mutlibyte character. Using CJK characters (3 bytes each) is a possible approach. For example, creating a share with name 에이에프에스삼점오생성 and trying to open a txt file in Notepad gives the following error:

  Invalid character. For multibyte character sets, only the leading byte is
  included without the trailing byte. For Unicode character sets, include
  the characters 0xFFFF and 0xFFFE.

Looking at wireshark capture, the following is seen as source of this issue:

  GetInfo Request FS_INFO/FileFsVolumeInformation File: Rathi9\???????????
  GetInfo Response, Error: STATUS_ILLEGAL_CHARACTER

Proposed solution is to truncate the label name at the end of a multibyte character before the 32nd byte.

Please review and suggest changes, improvements and other approaches.

Regards,
-Shyamsunder Rathi (mailto:shyam.rathi at nutanix.com)


From: Shyam Rathi <shyam.rathi at nutanix.com>
Date: Tuesday, May 14, 2019 at 10:52 AM
To: "samba-technical at lists.samba.org" <samba-technical at lists.samba.org>
Subject: [PATCH] s3:loadparm: Ensure to truncate FS Volume Label at multibyte boundary

For FS_VOLUME_INFO/FS_INFO operation, a maximum of 32 characters are
sent back. However, since Samba chops off any share name with >32
bytes at 32, it is possible that a multi-byte share name can get chopped
off between a full character. This causes the string decoding for unicode
failure which sends back NT_STATUS_ILLEGAL_CHARACTER (EILSEQ) to the client
applications.

On Windows, Notepad doesn't like it, and refuses to open a file in this
case and fails with the following error:

  Invalid character. For multibyte character sets, only the leading byte is
  included without the trailing byte. For Unicode character sets, include
  the characters 0xFFFF and 0xFFFE.

Proposed fix:
- Find the last starting point of a multibyte codepoint if the character
  at 32nd byte is a subsequent byte of a MB codepoint.

Reviewed-by: Hemanth Thummala <mailto:hemanth.thummala at nutanix.com>
Signed-off-by: Shyamsunder Rathi <mailto:shyam.rathi at nutanix.com>


Regards,

-Shyamsunder Rathi (mailto:shyam.rathi at nutanix.com)



-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-s3-loadparm-Ensure-to-truncate-FS-Volume-Label-at-mu.patch
Type: application/octet-stream
Size: 2636 bytes
Desc: 0001-s3-loadparm-Ensure-to-truncate-FS-Volume-Label-at-mu.patch
URL: <http://lists.samba.org/pipermail/samba-technical/attachments/20190514/2ec45c4a/0001-s3-loadparm-Ensure-to-truncate-FS-Volume-Label-at-mu.obj>