I'm running an SFTP server using openssh 1:8.9p1-3ubuntu0.1 on Ubuntu 22.04. A reoccurring issue with connecting clients is the username is prefixed with \357\273\277 one or more times. This is a UTF-8 BOM mark which is not needed and this login attempt fails because the username does not exist as prefixed with a BOM.
I currently work with each client to fix their connection. The one thing that seems to be in common is they are on Windows and use the Sticky Notes app to store their SFTP credentials so possibly that app is what adds the BOM. They are probably all using WinSCP which has some BOM settings, but those seem to be specific to the files that WinSCP transfers.
Is there a way to have openssh or PAM strip the leading BOM(s)?
If it's specific to WinSCP, is there some setting the clients should configure?
Thanks
Relevant /var/log/auth.log entry
Aug 28 16:13:25 sftp1 sshd[1670168]: Failed password for invalid user \357\273\277\357\273\277redacted_sftp_username from 165.165.165.165 port 35970 ssh2
Linux version
sftp1:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 22.04.3 LTS
Release: 22.04
Codename: jammy
Openssh Version
sftp1:~# dpkg -l | grep openssh
ii openssh-client 1:8.9p1-3ubuntu0.1 amd64 secure shell (SSH) client, for secure access to remote machines
ii openssh-server 1:8.9p1-3ubuntu0.1 amd64 secure shell (SSH) server, for secure access from remote machines
ii openssh-sftp-server 1:8.9p1-3ubuntu0.1 amd64 secure shell (SSH) sftp server module, for SFTP access from remote machines
System Locale
sftp1:~# locale
LANG=C.UTF-8
LANGUAGE=
LC_CTYPE="C.UTF-8"
LC_NUMERIC="C.UTF-8"
LC_TIME="C.UTF-8"
LC_COLLATE="C.UTF-8"
LC_MONETARY="C.UTF-8"
LC_MESSAGES="C.UTF-8"
LC_PAPER="C.UTF-8"
LC_NAME="C.UTF-8"
LC_ADDRESS="C.UTF-8"
LC_TELEPHONE="C.UTF-8"
LC_MEASUREMENT="C.UTF-8"
LC_IDENTIFICATION="C.UTF-8"
LC_ALL=
