connecting to Git via ssh on Windows fails - windows

Question

While my Linux machines can access the hosted repositories on the NAS using its hostname, my Windows machine fails to access it from command line / Visual Studio Code. During my debugging attempts I found a way so that at least TortoiseGit can access the repositories: I had to add an env var GIT_SSH_COMMAND=ssh -vvv (besides the already existing GIT_SSH=C:\Program Files\TortoiseGit\bin\TortoiseGitPlink.exe).
When I issue a git pull via cmd for a repository accessed in Git config via url = ssh://gituser#my-devices-hostname/volume1/git/reponame.git I get the following output:
OpenSSH_8.1p1, OpenSSL 1.1.1d 10 Sep 2019
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "my-devices-hostname" port 22
debug2: ssh_connect_direct
debug1: Connecting to my-devices-hostname [192.168.0.50] port 22.
getaddrinfo: atch: Name or service not known
ssh: connect to host my-devices-hostname port 22: failure
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
When I replace the hostname by a static IP I get the same error:
OpenSSH_8.1p1, OpenSSL 1.1.1d 10 Sep 2019
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolve_canonicalize: hostname 192.168.0.50 is address
debug2: ssh_connect_direct
debug1: Connecting to 192.168.0.50 [192.168.0.50] port 22.
getaddrinfo: atch: Name or service not known
ssh: connect to host 192.168.0.50 port 22: failure
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
When doing the same with TortoiseGit, everything works fine, I get:
OpenSSH_8.1p1, OpenSSL 1.1.1d 10 Sep 2019
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "my-devices-hostname" port 22
debug2: ssh_connect_direct
debug1: Connecting to my-devices-hostname [192.168.0.50] port 22.
debug1: Connection established.
...
I've recently set up a new DSL router (Fritz!Box 7590), maybe this is somehow related. Since I guessed that the problem could be related to IPv6, I've disabled IPv6 on the Synology NAS, but no change.
Update:
fedrik asked me to perform a manual ssh. Here are the results:
ssh gituser#my-devices-hostname
fatal: Interactive git shell is not enabled.
hint: ~/git-shell-commands should exist and have read and execute access.
Connection to my-devices-hostname closed.
and surprisingly:
ssh gituser#196.168.0.50
ssh: connect to host 196.168.0.50 port 22: Connection timed out
I updated my Git- and Tortoise installation, now I get
ssh gituser#192.168.0.50
fatal: Interactive git shell is not enabled.
hint: ~/git-shell-commands should exist and have read and execute access.
Connection to 192.168.0.50 closed.
The hostname based ssh remained the same.
Inspired by the answer from VonC, I checked if there are multiple instances of ssh installed on my system. I found the following:
C:\Windows\System32\OpenSSH\ssh.exe
C:\Program Files\Git\usr\bin\ssh.exe
So I checked (after updating Tortoise and Git for Windows), which one is used. First, I left GIT_SSH_COMMAND=ssh -vvv:
git pull
OpenSSH_8.4p1, OpenSSL 1.1.1h 22 Sep 2020
debug1: Reading configuration data /etc/ssh/ssh_config
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/c/Users/user/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/c/Users/user/.ssh/known_hosts2'
debug2: resolving "my-devices-hostname" port 22
debug2: ssh_connect_direct
debug1: Connecting to my-devices-hostname [192.168.0.50] port 22.
getaddrinfo: atch: Name or service not known
ssh: connect to host my-devices-hostname port 22: failure
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
"C:\Program Files\Git\usr\bin\ssh.exe" -vvv gituser#192.168.0.50
OpenSSH_8.4p1, OpenSSL 1.1.1h 22 Sep 2020
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolve_canonicalize: hostname 192.168.0.50 is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/c/Users/bjoer/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/c/Users/bjoer/.ssh/known_hosts2'
debug2: ssh_connect_direct
debug1: Connecting to 192.168.0.50 [192.168.0.50] port 22.
debug1: Connection established.
After I changed the env var: GIT_SSH_COMMAND=C:/Windows/System32/OpenSSH/ssh.exe -vvv I got this:
git pull
OpenSSH_for_Windows_7.7p1, LibreSSL 2.6.5
debug3: Failed to open file:C:/Users/user/.ssh/config error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_config error:2
debug2: resolving "my-devices-hostname" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to my-devices-hostname [192.168.0.50] port 22.
getaddrinfo: atch: Der angegebene Host ist unbekannt.
ssh: connect to host my-devices-hostname port 22: failure
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
C:\Windows\System32\OpenSSH\ssh.exe -vvv gituser#192.168.0.50
OpenSSH_for_Windows_7.7p1, LibreSSL 2.6.5
debug3: Failed to open file:C:/Users/user/.ssh/config error:2
debug3: Failed to open file:C:/ProgramData/ssh/ssh_config error:2
debug2: resolve_canonicalize: hostname 192.168.0.50 is address
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.0.50 [192.168.0.50] port 22.
debug1: Connection established.
When I unset GIT_SSH and GIT_SSH_COMMAND env vars, I get this:
git pull
getaddrinfo: atch: Name or service not known
ssh: connect to host my-devices-hostname port 22: failure
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
So, I can connect via SSH to the Git server, but when issues from the Git executable itself, it fails.
When I launch up a WSL on the same machine, I can perform a git pull without problems.
Any suggestions on how to tackle this issue?

Answer 1

Although this issue appeared somewhat after I installed a new router, the root cause was a defective setup of the Git server on my Synology NAS. After setting up the Git server from scratch following these steps, everything worked fine again:
Setup user and folder
Install WebDAV package via Diskstation Package Manager
Configure WebDAV: Enable HTTP on port 5005 and HTTPS on port 5006
Control Panel -> File Services -> SMB -> Advanced Settings -> Set min and max SMB protocols to SMB1 and SMB3
Create user gituser via Diskstation interface (group users, no access to shared folders, with File Station and WebDAV privilages)
Add new shared folder called git (located at /volume1/git) with read/write access for gituser. This folder will hold all the repos.
Install Git Server package via Diskstation
Open Git Server and allow gituser permissions (one has to login as "admin" to see the available users)
Enable SSH access on Diskstation (Control Panel > Terminal & SNMP > Enable SSH Service)
Activate user home service (Control Panel > Users > Extended > Userbase > Activate user home service)
Configure SSH Access
create ~/.ssh folder for gituser on server
sudo su
mkdir /volume1/homes/gituser/.ssh
create a private/public key pair via PuTTYgen (SSH-2 RSA, 2048 bits)
copy the public key show at top of the window to a file named authorized_keys
copy that file from local computer to gituser account on server
scp authorized_keys username#nas:/volume1/homes/gituser/.ssh
change permissions while logged in as root
cd /volume1/homes/gituser/
sudo chown -R gituser:users .ssh
sudo chmod 700 .ssh
sudo chmod 644 .ssh/authorized_keys
sudo chmod 755 /volume1/homes/gituser
activate public key SSH access by setting the following properties in /etc/ssh/sshd_config
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile %h/.ssh/authorized_keys
disable and then re-enabled the SSH service (Control Panel > Terminal & SNMP > Enable SSH Service)

Answer 2

I was getting this error as a result of setting git config --global ssh.variant plink. By setting git config --global ssh.variant ssh, this error went way. The problem seems to be that git was passing a -batch option, which plink was interpreting as a -b option (hence the strange error involving "atch".

Answer 3

I would try the same ssh call without GIT_SSH set
set GIT_SSH=
With a recent Windows 10, openSSH is either directly installed or provided with Git For Windows.
Make sure to use the latest version of Git, and add its usr/bin folder to your PATH.