[JSch-users] Filename Encoding

[Christian S. <Chr...@so...>]

Hi all,
I try to access files on an SFTP server (using Jsch) which use for their names an encoding different from UTF-8 (in my case, ISO-8859-1). I have found an old discussion about that topic (https://sourceforge.net/p/jsch/mailman/message/26647296/) and a corresponding entry in the changelog for version 0.1.45 ("bugfix: sftp protocol version 3, 4 and 5 should allow only UTF-8 encoding"). However, I think that their might be some misunderstanding about the SFTP version numbers which leads to a still incorrect behavior of Jsch.
Looking at the specs (e.g. https://tools.ietf.org/html/draft-ietf-secsh-filexfer-00), I see that there are 14 versions of the specs. However, these do *not* correspond to the SFTP protocol version in a one-to-one manner. The SFTP protocol version for each of the spec versions is given in the section "Protocol Initialization". Looking at this section, we find that spec versions 0 to 2 describe protocol version 3, spec versions 3 and 4 describe protocol version 4, spec version 5 describe protocol version 5 and spec versions 6 to 13 describe protocol version 6. (This information can also be found at https://en.wikipedia.org/wiki/SSH_File_Transfer_Protocol#History_and_development.)
In the original protocol version 3, the filename encoding is undefined. In protocol versions 4 and 5, the filename encoding must be UTF-8, and in protocol version 6, the filename encoding can be negotiated. This has also been discussed in the old mailing list thread, but the versions mentioned in that thread were the spec versions, and not the protocol versions. So the current implementation ...

    if(3 <= sversion && sversion <= 5 &&
       !encoding.equals(UTF8)){
      throw new SftpException(SSH_FX_FAILURE,
                              "The encoding can not be changed for this sftp server.");
    }

... is not correct in my opinion and should be changed to ...

    if(4 <= sversion && sversion <= 5 &&
       !encoding.equals(UTF8)){
      throw new SftpException(SSH_FX_FAILURE,
                              "The encoding can not be changed for this sftp server.");
    }

... because only protocol versions 4 and 5 hardcoded the encoding to be UTF-8.

Regards,
Christian

PS: This mail doesn't seem to have come through the first time, so I resend it. Please excuse if it actually is a duplicate now.