Ssh

為什麼即使使用錯誤的密鑰，我也能通過 SSH 連接遠端機器？

  • August 26, 2021

描述

我已經ssh在我的 MS-Windows PC 和 Raspberry Pi 之間建立了連接。為此，我按照以下步驟操作：

第 1 步：以某種方式獲取 Raspberry Pi 的 IP 地址。它應該是這樣的：192.168.1.52

第 2 步：打開 shell 並通過 ssh 訪問樹莓派：

ssh pi@192.168.1.52

您將需要密碼。

第 3 步：在遠端 pc 的主目錄中使用以下命令：

mkdir .ssh

第 4 步：通過私鑰/公鑰保護 ssh 連接。在本地電腦中使用以下命令：

ssh-keygen -f .ssh/fede_windows -t rsa -b 4096

如果您的本地電腦是基於 Linux 的，請執行此行：

chmod 600 .ssh/fede_windows # if linux

最後：

scp .ssh/fede_windows.pub pi@192.168.1.52:.ssh

第 5 步：在遠端 pc 中使用以下命令：

sudo nano /etc/ssh/sshd_config

並修改配置文件的以下行：

ChallengeResponseAuthentication no
PasswordAuthentication no
UsePAM no

最後：

sudo systemctl reload sshd

第 6 步：在遠端電腦上使用以下命令：

cat ~/.ssh/fede_windows.pub >> ~/.ssh/authorized_keys
chmod 700 ~/.ssh/
chmod 600 ~/.ssh/*

第 7 步：在本地電腦上執行此命令以登錄到遠端電腦：

ssh -i .ssh/fede_windows pi@192.168.1.52

問題：當我通過生成一個名為 fede_ubuntu 的密鑰在我的 Ubuntu Pc 中再次執行所有這些步驟時，看起來無論我在命令中插入什麼內容，我都能夠對我的 Raspberry Pi 進行 ssh：

ssh -i .ssh/fede_xyz pi@192.168.1.52

它一直有效，這不應該發生，因為它應該僅限於我剛剛創建的密鑰。如果我切換到我的 Windows 機器，一切都會按預期工作，並且只有當我指定正確的鍵才能工作。

問題：您能否提出此問題的可能原因以及如何解決？

編輯：通過輸入以下命令ssh -i .ssh/key_that_does_not_exits -v pi@192.168.1.52，我得到：

Warning: Identity file .ssh/key_that_does_not_exits not accessible: No such file or directory.
OpenSSH_8.2p1 Ubuntu-4ubuntu0.3, OpenSSL 1.1.1f  31 Mar 2020
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: Connecting to 192.168.1.52 [192.168.1.52] port 22.
debug1: Connection established.
debug1: identity file /home/federico/.ssh/id_rsa type -1
debug1: identity file /home/federico/.ssh/id_rsa-cert type -1
debug1: identity file /home/federico/.ssh/id_dsa type -1
debug1: identity file /home/federico/.ssh/id_dsa-cert type -1
debug1: identity file /home/federico/.ssh/id_ecdsa type -1
debug1: identity file /home/federico/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/federico/.ssh/id_ecdsa_sk type -1
debug1: identity file /home/federico/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/federico/.ssh/id_ed25519 type -1
debug1: identity file /home/federico/.ssh/id_ed25519-cert type -1
debug1: identity file /home/federico/.ssh/id_ed25519_sk type -1
debug1: identity file /home/federico/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/federico/.ssh/id_xmss type -1
debug1: identity file /home/federico/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.9p1 Raspbian-10+deb10u2+rpt1
debug1: match: OpenSSH_7.9p1 Raspbian-10+deb10u2+rpt1 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.1.52:22 as 'pi'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
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:hC5w2kDxgHH5eFRY1vOJaS7ipPR+8OWX2tkkEZbF194
debug1: Host '192.168.1.52' is known and matches the ECDSA host key.
debug1: Found key in /home/federico/.ssh/known_hosts:1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: federico@federico RSA SHA256:E96Hu2Ee+IyAuoZ06GxTvo+ZmAkzqfihbAKkFqxU1AU agent
debug1: Will attempt key: /home/federico/.ssh/id_rsa 
debug1: Will attempt key: /home/federico/.ssh/id_dsa 
debug1: Will attempt key: /home/federico/.ssh/id_ecdsa 
debug1: Will attempt key: /home/federico/.ssh/id_ecdsa_sk 
debug1: Will attempt key: /home/federico/.ssh/id_ed25519 
debug1: Will attempt key: /home/federico/.ssh/id_ed25519_sk 
debug1: Will attempt key: /home/federico/.ssh/id_xmss 
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Offering public key: federico@federico RSA SHA256:E96Hu2Ee+IyAuoZ06GxTvo+ZmAkzqfihbAKkFqxU1AU agent
debug1: Server accepts key: federico@federico RSA SHA256:E96Hu2Ee+IyAuoZ06GxTvo+ZmAkzqfihbAKkFqxU1AU agent
debug1: Authentication succeeded (publickey).
Authenticated to 192.168.1.52 ([192.168.1.52]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Remote: /home/pi/.ssh/authorized_keys:2: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /home/pi/.ssh/authorized_keys:2: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Sending environment.
debug1: Sending env LC_ADDRESS = it_IT.UTF-8
debug1: Sending env LC_NAME = it_IT.UTF-8
debug1: Sending env LC_MONETARY = it_IT.UTF-8
debug1: Sending env LC_PAPER = it_IT.UTF-8
debug1: Sending env LANG = en_US.UTF-8
debug1: Sending env LC_IDENTIFICATION = it_IT.UTF-8
debug1: Sending env LC_TELEPHONE = it_IT.UTF-8
debug1: Sending env LC_MEASUREMENT = it_IT.UTF-8
debug1: Sending env LC_TIME = it_IT.UTF-8
debug1: Sending env LC_NUMERIC = it_IT.UTF-8
Last login: Sun Aug 22 22:26:00 2021 from 192.168.1.197

從您的日誌中：

debug1: Next authentication method: publickey
debug1: Offering public key: federico@federico RSA SHA256:E96Hu2Ee+IyAuoZ06GxTvo+ZmAkzqfihbAKkFqxU1AU agent
debug1: Server accepts key: federico@federico RSA SHA256:E96Hu2Ee+IyAuoZ06GxTvo+ZmAkzqfihbAKkFqxU1AU agent
debug1: Authentication succeeded (publickey).

這意味著正在使用來自 SSH 代理的密鑰。我假設它是您最近使用的有效密鑰，並且您已經手動添加到代理中，或者由於AddKeysToAgent yes在~/.ssh/config文件中使用而被添加。

從您的 SSH 代理中刪除所有身份，然後重試：ssh-add -D。或者，添加IdentityAgent none到您的 SSH 配置或ssh -o IndentityAgent=none在呼叫時使用ssh.

您還可以從IdentitiesOnly yesSSH 配置中受益，這將使您能夠更好地控制向 SSH 伺服器提供哪些身份。請參閱 中有關此選項的文件ssh_config(5)。

引用自：https://unix.stackexchange.com/questions/666058

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