[Bug 3547] New: sftp crash with 'invalid multibyte character' when pressing Tab to complete specific Chinese filenames

[bugzilla-daemon at mindrot.org]

https://bugzilla.mindrot.org/show_bug.cgi?id=3547

            Bug ID: 3547
           Summary: sftp crash with 'invalid multibyte character' when
                    pressing Tab to complete specific Chinese filenames
           Product: Portable OpenSSH
           Version: 8.4p1
          Hardware: amd64
                OS: Linux
            Status: NEW
          Severity: trivial
          Priority: P5
         Component: sftp
          Assignee: unassigned-bugs at mindrot.org
          Reporter: nebclllo0444 at gmail.com

I'm using sftp bundled with OpenSSH 8.4p1-150300.3.15.4 on openSUSE
Leap 15.4. I encountered a problem that when there are some files with
specific Chinese filename. For example:
(using bash with LANG=zh_CN.utf8)
touch （一）
touch （二）
# Create two file that contains character that represents number. They
have the same prefix and suffix. These parentheses are also CJK
characters(Not ASCII).
sftp 127.0.0.1
ls （
# Input the first character(The common prefix of the two filenames)
# And press the Tab to auto-complete
And the client immediately after printing the filenames, leaving the
terminal not usable without a `reset`:
（一） （二）
invalid multibyte character

It seems that only a few combinations will make the client crash. If
these are "（一）" and "（啊）", the client will not crash.

Prefixes and suffixes other than CJK parentheses will make the client
crash, though: 

Input 'ls 啊' and press Tab. "啊一啊" "啊二啊" will crash the client. "啊一啊"
"啊哦啊" will not.

Switching sftp subsystem from external sftp server to 'internal-sftp'
in sshd_config will not fix it.

The same problem also exists on Debian Bullseye (with OpenSSH
1:8.4p1-5+deb11u1)

This is my first bug report for OpenSSH, and I'm not good at English.
Sorry for any inconvenience.

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