使用公共密钥认证为 Windows 设置 OpenSSH

我在使用公共密钥认证为 Windows 设置 OpenSSH 时遇到了问题。

我有这个工作在我的本地桌面，可以 ssh 与一个关键从 Unix 机器或其他 OpenSSH 为 Windows 机器。

我已经将构建版本复制到服务器上，可以很好地使用密码身份验证，但是当我使用密钥时，会出现以下问题:

debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug3: start over, passed a different list publickey,password,keyboard-interactive
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /cygdrive/c/sshusers/jsadmint2232/.ssh/id_rsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
Connection closed by 127.0.0.1

因此，出于测试的目的，我只是尝试使用 SSH 到 localhost，但是即使远程尝试，我也会遇到同样的问题。

更奇怪的是，当我在 sshd_config中同时启用了密码和公钥时，它只会尝试使用密钥，然后用上面的消息轰炸，甚至不会尝试使用密码。

以下是我采取的步骤:

  1. 为 Windows 安装 OpenSSH
  2. mkgroup -l >>..\etc\group(增加的本地组)
  3. mkgroup -d >>..\etc\group(添加的域组)
  4. mkpasswd -L -u openssh >>..\passwd(本地用户添加)
  5. mkpasswd -D -u jsadmint2232 >>..\passwd(添加我的域用户)
  6. 编辑文件 密码中的主目录以指向 c: sshusers% USER%-其中% USER% 是用户名
  7. 启用了密码认证禁用了密钥认证
  8. 为 jsadmint2232/OpenSSH 创建 SSH 密钥，并确保在主目录中创建文件
  9. 为每个用户在. ssh 目录中添加 Authorized_ keys 文件，并为传入的连接用户添加密钥
  10. net stop opensshd/net start opensshd
  11. 测试密码身份验证是否在本地和远程都可以工作
  12. 更新 sshd _ config，以启用密钥 auth-start opensshd
  13. 测试连接并得到以上错误。此外，它甚至不尝试密码验证。
  14. 更新了 sshd _ config，以完全禁用密码身份验证-重新启动 opensshd
  15. 测试连接，仍然得到以上错误

看来服务器出于某种原因中断了连接。

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最佳答案

I have solved the issue...

It is related to the account that started the service - it was using the Local System account - this was stopping it accessing the public key and authorized_keys file.

Once I stopped the service and started as the user I was trying to connect into, it worked!

So basically, you need to start with a service account and then external users connect in as that user.

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If you are using mls-software.com's version of OpenSSH here is another note.

If you install using the SSHD_SERVER account and privilege separation you will be able to use public key authentication (per http://www.mls-software.com/opensshd-pki.html). However if UAC is enable you will not be successful with the install. The user(s) will not be created properly and the service will not be created. Manually trying to get these items up after the fact is very difficult. Simply disabling UAC before installation will allow the installation process to properly create the user(s) and the service. After installation you can re-enable UAC.

When I created the SSHD_SERVER account manually authentication succeed when using password authentication but the client termination the connection with "/bin/bash: Operation not permitted". Authentication with public keys was closed by the server (original error posted by Cambolie).

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I solved it by:

  1. Installing in SSHD_SERVER + privilege separation mode. I also set privilege separation to "yes" in the config manually. This didn't work for me for a lot time, the user didn't get created. Then it worked, I don't know why. I only went to user accounts in control panel to check that UAC is off. I also had /var/empty with full access for everyone.
  2. For C:\openssh\var\empty I've set "attributes get/set" permissions to Everyone and myself and "full" permissions to .\sshd_server. I also made it the owner.
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Following are setup steps for OpenSSH shipped with Windows 10 v.1803 (April 2018 update. See comments to this post, it might not work with 1809).

Server setup (elevated powershell):

  1. Install OpenSSH server: Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0.

  2. Start agent and sshd services: Start-Service ssh-agent; Start-Service sshd (this will generate host keys and default configuration automatically in $env:ProgramData\ssh).

  3. [Optional] Install OpenSSHUtils powershell module: Install-Module -Force OpenSSHUtils

Client setup (non-elevated powershell):

  1. Generate user key: cd $env:USERPROFILE\.ssh; ssh-keygen.exe, follow prompts, agree to the default suggested file location. This will create 2 files: id_rsa and id_rsa.pub;

  2. [Optional] add key to authentication agent, so you don't have to enter password each time you use it: ssh-add .\id_rsa (or whatever file was generated);

Server setup continued (non-elevated powershell):

  1. Log in as a user, for which public key auth to be used
  2. cd $env:USERPROFILE; mkdir .ssh; cd .ssh; New-Item authorized_keys;
  3. Paste the contents of the id_rsa.pub file from the client to the .ssh\authorized_keys file from the previous step.
  4. Setup permissions properly (important!!!):
    1. Run start . to open explorer with the current folder ($env:USERPROFILE\.ssh);
    2. Right click authorized_keys, go to Properties -> Security -> Advanced
    3. Click "Disable inheritance";
    4. Choose "Convert inherited permissions into explicit permissions on this object" when prompted;
    5. (really, really important) Remove all permissions on file except for the SYSTEM and yourself. There must be exactly two permission entries on the file. Some guides suggest running the Repair-AuthorizedKeyPermission $env:USERPROFILE\.ssh\authorized_keys - this will try to add the sshd user to the permission list and it will break the authentication, so, don't do that, or at least do not agree on adding the sshd user). Both SYSTEM and yourself should have full control over the file.
  5. If your Windows build is 1809 or later, it is required to comment out the following lines in C:\ProgramData\ssh\sshd_config file. Then restart the sshd service. 
    # Match Group administrators
#       AuthorizedKeysFile __PROGRAMDATA__/ssh/administrators_authorized_keys

Client:

  1. Run ssh <serverusername>@<serverhostname>. It should work at this point.

Tried that with Windows 10 as server and both itself and a Debian Linux as a client.

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I've thoroughly tested n0rd's solution on multiple Windows Pro 1809 and 2004 computers. I concur with most of his steps.

Server setup (elevated PowerShell): Agree with all.

Client setup (non-elevated PowerShell): Agree with all.

Server setup continued (non-elevated PowerShell): Steps 1,2,3: Agree

Server setup continued (non-elevated PowerShell): Step 4: Do NOT perform anything in step 4.

Server setup continued (non-elevated PowerShell): Step 5: Agree

Server setup continued (non-elevated PowerShell): Step 6: (added) Uncomment (remove #) from C:\ProgramData\ssh\sshd_config: #PasswordAuthentication yes

Server setup continued (non-elevated PowerShell): Step 7: (added) In Services, restart OpenSSH SSH Server.

I did not find any issues, with any file, regarding security, permissions or Unicode. They were all correct out of the box.

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One more tip, if you are stuck, is to run sshd in debug mode. I did this:

  1. Stop the sshd service
  2. Open a PowerShell console with administrator privileges
  3. Type 'sshd -d'
  4. Type login from my client machine

It turns out the key need to be in e.g. C:\ProgramData\ssh\administrators_authorized_keys instead of C:\Users\yourUsser.ssh\authorized_keys.

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This is just my scripted version of @n0rds great answer.

Place this script in a directory w/ your private/public key/pair and run!

PowerShell.exe -ExecutionPolicy Bypass -File "C:\bypass\prompt\standard.ps1" 2>&1>$null


Add-WindowsCapability -Online -Name OpenSSH.Server
New-NetFirewallRule -Name sshd -DisplayName 'OpenSSH SSH Server' -Enabled True -Direction Inbound -Protocol TCP -Action Allow -LocalPort 22 -Program "%WINDIR%\System32\OpenSSH\sshd.exe"


#Must Enable ssh-agent before starting
Set-Service -Name ssh-agent -StartupType Automatic
Set-Service -Name sshd -StartupType Automatic
Start-Service ssh-agent; Start-Service sshd


$sshdir="$env:USERPROFILE\.ssh"
mkdir $sshdir
copy .\id_rsa $sshdir\
cat  $sshdir\id_rsa
copy .\*.pub  $sshdir\authorized_keys
cat $sshdir\authorized_keys
ssh-add $sshdir\id_rsa


$sshd_config="C:\ProgramData\ssh\sshd_config"
(Get-Content $sshd_config) -replace '#PubkeyAuthentication', 'PubkeyAuthentication' | Out-File -encoding ASCII $sshd_config
(Get-Content $sshd_config) -replace 'AuthorizedKeysFile __PROGRAMDATA__', '#AuthorizedKeysFile __PROGRAMDATA__' | Out-File -encoding ASCII $sshd_config
(Get-Content $sshd_config) -replace 'Match Group administrators', '#Match Group administrators' | Out-File -encoding ASCII $sshd_config
cat C:\ProgramData\ssh\sshd_config


Restart-Service ssh-agent; Restart-Service sshd


Write-Host "Use this to Login/test Now"
write-host ssh $env:UserName@localhost
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Use this sequence of commands in PowerShell to correct permission of administrators_authorized_keys

$acl = Get-Acl C:\ProgramData\ssh\administrators_authorized_keys
$acl.SetAccessRuleProtection($true, $false)
$administratorsRule = New-Object system.security.accesscontrol.filesystemaccessrule("Administrators","FullControl","Allow")
$systemRule = New-Object system.security.accesscontrol.filesystemaccessrule("SYSTEM","FullControl","Allow")
$acl.SetAccessRule($administratorsRule)
$acl.SetAccessRule($systemRule)
$acl | Set-Acl

Only SYSTEM and Administrators group must be have permission in file without inherited.

Permission set of administrators_authorized_keys

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This is a very English language centric default Microsoft use. The group match lines currently check for the ENGLISH language version string of the Administrators group called 'administrators' this FAILS on many other language installs of windows. On a German installation that line needs to be 'administratoren' instead. They better make it possible le to match group by SID instead. ( This is even more important in the DenyGroups matching feature - have not tested this yet - but if they check for strings instead of SID there then the denies are meaningless and easily circumvented by using a different windows language install )

( also see https://github.com/MicrosoftDocs/windowsserverdocs/issues/1911#issuecomment-771552030 )

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I ran into a different situation.

First, debug as gWay said, with another terminal windows connecting to the server.

I gotread_keyfile_line: C:\\Users\\yieatn\\.ssh/authorized_keys line 1 exceeds size limit

recode the authorized_keys into utf-8

The reason is that I created authorized_keys with cat id_rsa >> authorized_keys and powershell in Chinese uses UTF-16 to create files.

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n0rd's solution is on the money but there's an added complication for users that are also in the administrator's group. If you're looking for a solution to a situation involving the following conditions:

  • You want to use public keys on a per-user basis (or you don't want to use the administrators_authorized_keys file).
  • And you don't want to use PasswordAuthentication.
  • And some of the users also belong to the admin group.

The issue I ran across is that when I tried n0rd's solution it didn't work for users under the conditions above. After some tinkering, I found a solution that works consistently for me. Follow n0rd's solution and just change the following

In the ssh_config make sure the following settings are set:

AuthorizedKeysFile  .ssh/authorized_keys
PasswordAuthentication no
PubkeyAuthentication yes

Also, make sure to comment out the Match Group Administrators setting:

#Match Group administrators
#       AuthorizedKeysFile __PROGRAMDATA__/ssh/administrators_authorized_keys

Make sure to include the client's public key in the servers C:\Users\username\.ssh\authorized_keys file.

Finally, to help match the user to the account I found it helpful to be more specific with the user data on the client. Instead of using the plain username, I used the username along with the domain of the user on the server. In my case, my client's C:\Users\UserName\.ssh\config file looked like this:

Host my_short_name
HostName my.serveraddress.net
User serversname\username
IdentityFile .ssh\id_rsa

In this case, my Windows 10 server would be called serversname (under device name). By specifying the user in this way I could avoid password authentication.

As an added bonus, this worked very well with a default shell of PowerShell 7. Even my default PowerShell profile worked over ssh and I got full support for posh-git and oh-my-posh. However, I found that the default method suggested for making PowerShell the default shell environment, (by editing the ssh_conf to include 'Subsystem powershell c:/progra~1/powershell/7/pwsh.exe -sshs -NoLogo') did not work for me. Instead, on the server use the command in an elevated PowerShell window:

New-ItemProperty -Path "HKLM:\SOFTWARE\OpenSSH" -Name DefaultShell -Value "c:/progra~1/powershell/7/pwsh.exe" -PropertyType String -Force

This just creates a registry entry. You can always pop in the registry to remove it later if you want.

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I couldn't get it to work with my ed25519 client public key (ssh-keygen -t ed215519) but it does work with an rsa key ( ssh-keygen -t rsa).

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No one has pointed out that the file ~/.ssh/authorization_keys must use DOS/Windows line endings. It won't work with Unix line endings. If you have tried everything and still not working, try this (I am using cygwin):

gawk -v ORS='\r\n' '1' authorized_keys > authorized_keys2

Check that the file has now DOS line endings:

hexdump -C authorization_keys2

Replace the original file:

mv authorized_keys2 authorized_keys

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