Ssh

X11 通過 ssh 轉發僅適用於 sudo

  • October 29, 2020

問題

我無法再以普通使用者的身份通過 ssh 進行 X11 轉發。它在幾個月前起作用，所以無意中改變了一些東西。

我試過的

與 sudo 一起使用：

據我所知，我的 ssh 和 sshd 配置是正確的。事實上，如果我使用 sudo 以 root 身份執行，X11 會正確轉發：

$ ssh -X lm@<ip> -i <key>

lm@localhost:~$ xeyes
Error: Can't open display: localhost:10.0

lm@localhost:~$ sudo xeyes

lm@localhost:~$

使用sudo成功轉發 X似乎是一個常見問題，但這是相反的問題。我不太了解我所看到的有關以 root 或其他使用者身份轉發 X 的資訊，而且我根本不需要以 root 或其他使用者身份轉發。那麼，我怎樣才能將其重置為正常呢？

xauth

對我來說，這是一個身份驗證問題是有道理的。不過，我不確定如何判斷它是否正確。

使用者的 .Xauthority 中有兩個條目

lm@localhost:~$ xauth info
Authority file:       /home/lm/.Xauthority
File new:             no
File locked:          no
Number of entries:    2
Changes honored:      yes
Changes made:         no
Current input:        (argv):1

lm@localhost:~$ xauth list
edare-fmt17138762/unix:10  MIT-MAGIC-COOKIE-1  48081e511d8ba861ccaf146b73a01617
localhost/unix:10  MIT-MAGIC-COOKIE-1  ce23a352c8f10814e103474aa620fc31

我嘗試刪除 .Xauthority 但這並沒有解決問題。

可能相關的主機名問題

主機名應該是edare-fmt17138762，但每次重新啟動都會重置。我已經嘗試再次設置主機名，並將主機名完全重置為 localhost，但這些都沒有對轉發 X 產生任何影響，所以看起來主機名並不是問題所在。

sshd_config 更改

我嘗試使用X11UseLocalhost yes沒有效果。

我也試過X11UseLocalhost no了，它給出了額外且略有不同的錯誤：

$ ssh -Y lm@192.168.0.15 -i <key>
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)

* Documentation:  https://help.ubuntu.com
* Management:     https://landscape.canonical.com
* Support:        https://ubuntu.com/advantage
Last login: Thu Mar  1 14:51:41 2018 from 192.168.0.2
/usr/bin/xauth: (stdin):1:  bad display name "edare-fmt17138762:10.0" in "remove" command
/usr/bin/xauth: (stdin):2:  bad display name "edare-fmt17138762:10.0" in "add" command
lm@edare-fmt17138762:~$ xeyes
Error: Can't open display: edare-fmt17138762:10.0

設置顯示

我還嘗試將 DISPLAY 變數設置為127.0.0.1:10.0：

lm@edare-fmt17138762:~$ export DISPLAY='192.168.0.15:10.0'
lm@edare-fmt17138762:~$ xeyes
X11 connection rejected because of wrong authentication.
Error: Can't open display: 192.168.0.15:12.0

SSH 配置

伺服器

執行標準 OpenSSH 的 Ubuntu 16.04。

# Package generated configuration file
# See the sshd_config(5) manpage for details

# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes

# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024

# Logging
SyslogFacility AUTH
LogLevel INFO

# Authentication:
LoginGraceTime 120
PermitRootLogin prohibit-password
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile %h/.ssh/authorized_keys

# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes

# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Change to no to disable tunnelled clear text passwords
   PasswordAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no

#MaxStartups 10:30:60
#Banner /etc/issue.net

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

Subsystem sftp /usr/lib/openssh/sftp-server

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
   PasswordAuthentication no

客戶

幾個曾經工作過的客戶端也出現了同樣的問題：來自另一台 Ubuntu 16.04 機器的 OpenSSH 和來自 Windows 10 的 puTTy。

ssh -v

OpenSSH_7.2p2 Ubuntu-4ubuntu2.4, OpenSSL 1.0.2g  1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 192.168.0.15 [192.168.0.15] port 22.
debug1: Connection established.
debug1: identity file <my file> type 1
debug1: key_load_public: No such file or directory
debug1: identity file <my file> type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.2 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.0.15:22 as 'lm'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256@libssh.org
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:WVq6hBhuqXF99QGeoyfeiLYk+l7fJOGqpyk52roqdcE
debug1: Host '192.168.0.15' is known and matches the ECDSA host key.
debug1: Found key in /home/jmilloy/.ssh/known_hosts:34
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: <my key>
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug1: Authentication succeeded (publickey).
Authenticated to 192.168.0.15 ([192.168.0.15]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: exec
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Requesting X11 forwarding with authentication spoofing.
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)

關於主機名重置，請檢查您是否安裝並配置了 cloud-config 之類的東西。它確實弄亂了一些東西，您可能需要更改一些選項，例如 update_hostname 或 set_hostname。

關於這個問題，請嘗試將以下內容添加到您的 sshd_config 並重新啟動 sshd。

X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost yes
AddressFamily inet

有同樣的問題，解決方案是：我的主機名（cat /etc/hostname）不在/etc/hosts.

有一個不同的名稱，其中定義了我的 IP 地址/etc/hosts

引用自：https://serverfault.com/questions/899492

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