openssh bugs - Oct 2015 - [Bug 2477] New: backspace in interactive session does not delete multi-byte Unicode characters correctly

https://bugzilla.mindrot.org/show_bug.cgi?id=2477

            Bug ID: 2477
           Summary: backspace in interactive session does not delete
                    multi-byte Unicode characters correctly
           Product: Portable OpenSSH
           Version: 7.1p1
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: sshd
          Assignee: unassigned-bugs at mindrot.org
          Reporter: jjelen at redhat.com

Created attachment 2723
  --> https://bugzilla.mindrot.org/attachment.cgi?id=2723&action=edit
patch adding IUTF8 flag, if available

After report in our bugzilla [1] about utf8 support in remote terminals
I dived a bit into this topic and found that openssh doesn't count with
termios flag IUTF8 for handling utf8 characters interactively. This
flag exists for some time and is available in Linux kernel since
version 2.6. Really nice article [2] describes this issue (last
paragraph).

Minimal test case is also described in original bugzilla, but I will
copy it also here:

1. ssh to machine with openssh
2. $ cat > test
3. Use this as a input for cat command:
?<press backspace once><press CTRL+D><press CTRL+D>
4. $ hexdump test

Actual results:
0000000 00c3                                   
0000001

Expected results:
The file "test" should be empty.

Solution is quite simple. Adding this this mode into ttymodes.h solves
this issue. Problematic is that this changes things on both sides to
apply.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1270248
[2] https://www.cl.cam.ac.uk/~mgk25/unicode.html#mod

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Petr ?pa?ek <pspacek at redhat.com> changed:

           What    |Removed                     |Added
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                 CC|                            |pspacek at redhat.com

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Darren Tucker <dtucker at zip.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |dtucker at zip.com.au

--- Comment #1 from Darren Tucker <dtucker at zip.com.au> ---
Even more problematic is that the value you are using is not defined in
RFC4254 section 8.

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--- Comment #2 from Jakub Jelen <jjelen at redhat.com> ---
Yeah, I see.

Now I found some discussion years ago on IETF and there are much more
about this topic, But having a track about this also in this bugzilla
will not hurt (I hope I didn't miss any dupplicate).
http://www.ietf.org/mail-archive/web/secsh/current/msg00658.html

Yes, this would require addition to protocol specification. Do you know
if is some revision planned in close future? Or is there something I
can help with?

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
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   Attachment #2723|0                           |1
        is obsolete|                            |
                 CC|                            |djm at mindrot.org
   Attachment #2736|                            |ok?(dtucker at zip.com.au)
              Flags|                            |

--- Comment #3 from Damien Miller <djm at mindrot.org> ---
Created attachment 2736
  --> https://bugzilla.mindrot.org/attachment.cgi?id=2736&action=edit
Add terminal mode, document in PROTOCOL

If we do this (and I don't see why we shouldn't), we should mention the
assignment in the PROTOCOL file.

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--- Comment #4 from Darren Tucker <dtucker at zip.com.au> ---
Comment on attachment 2736
  --> https://bugzilla.mindrot.org/attachment.cgi?id=2736
Add terminal mode, document in PROTOCOL

I think we should at least attempt to get this assigned via the proper
process.

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Darren Tucker <dtucker at zip.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Attachment #2736|ok?(dtucker at zip.com.au)     |ok-
              Flags|                            |

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--- Comment #5 from Darren Tucker <dtucker at zip.com.au> ---
Simon Tatham has submitted an internet-draft for this:
http://www.ietf.org/id/draft-sgtatham-secsh-iutf8-00.txt

and it's currently implemented in the development branches of OpenSSH
and PuTTY.

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Darren Tucker <dtucker at zip.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

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Darren Tucker <dtucker at zip.com.au> changed:

           What    |Removed                     |Added
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             Blocks|                            |2543


Referenced Bugs:

https://bugzilla.mindrot.org/show_bug.cgi?id=2543
[Bug 2543] Tracking bug for OpenSSH 7.3 release
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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
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             Status|RESOLVED                    |CLOSED

--- Comment #6 from Damien Miller <djm at mindrot.org> ---
Close all resolved bugs after 7.3p1 release

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