我怎樣才能讓 sshd 告訴我為什麼它無法通過公鑰身份驗證？

我使用 OpenSSH 6.9p1（在 Lubuntu 上）作為我的 SSH 伺服器。當嘗試連接到它時（在 Cygwin 中使用 SSH 客戶端），我一直被恢復為密碼身份驗證，儘管我已經正確生成了我的密鑰，將它們放在伺服器上的授權密鑰文件中，檢查了權限等。

所以，我看看/var/log/auth.log伺服器說什麼。我發現這個：

Nov  1 09:50:10 er-thinkpad sshd[16148]: Accepted password for joeuser from 192.168.2.6 port 53325 ssh2
Nov  1 09:50:10 er-thinkpad sshd[16148]: pam_unix(sshd:session): session opened for user joeuser by (uid=0)
Nov  1 09:50:10 er-thinkpad systemd-logind[590]: New session 497 of user joeuser.

…在第一行之前沒有關於公鑰認證失敗的任何內容。好的，讓我們增加詳細程度。所以我LogLevel從INFOto更改VERBOSE並再試一次。現在我得到：

Nov  1 09:53:12 er-thinkpad sshd[16269]: Connection from 192.168.2.6 port 53349 on 192.168.2.2 port 22
Nov  1 09:53:12 er-thinkpad sshd[16269]: Failed publickey for joeuser from 192.168.2.6 port 53349 ssh2: RSA SHA256:removedthis
Nov  1 09:53:12 er-thinkpad sshd[16269]: Failed publickey for joeuser from 192.168.2.6 port 53349 ssh2: ECDSA SHA256:removedthis
Nov  1 09:53:15 er-thinkpad sshd[16269]: Accepted password for joeuser from 192.168.2.6 port 53349 ssh2
Nov  1 09:53:15 er-thinkpad sshd[16269]: pam_unix(sshd:session): session opened for user joeuser by (uid=0)
Nov  1 09:53:15 er-thinkpad systemd-logind[590]: New session 499 of user joeuser.
Nov  1 09:53:15 er-thinkpad sshd[16269]: User child is on pid 16271
Nov  1 09:53:15 er-thinkpad sshd[16271]: Starting session: shell on pts/5 for joeuser from 192.168.2.6 port 53349

太好了，它失敗了，但為什麼它失敗了？我怎樣才能讓 sshd 告訴我呢？

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PS - 如您所知，這是客戶所看到的：

debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/joeuser/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Skipping ssh-dss key /home/joeuser/.ssh/id_dsa for not in PubkeyAcceptedKeyTypes
debug1: Offering ECDSA public key: /home/joeuser/.ssh/id_ecdsa
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /home/joeuser/.ssh/id_ed25519
debug1: Next authentication method: password

在伺服器端，將日誌級別設置為DEBUG3. 在客戶端，使用該-vvv選項連接（這也為您DEBUG3提供客戶端）。

引用自：https://serverfault.com/questions/733082