这个问题已经讨论过很多次了，但是我开设这个主题是因为这个问题略有不同。
这是我尝试使用用户 sshuser 连接到 IP 为 192.168.5.2 的计算机时的日志：
OpenSSH_8.9p1 Ubuntu-3ubuntu0.1, OpenSSL 3.0.2 15 Mar 2022
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 *
debug3: kex names ok: [diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,curve25519-sha256,[email protected],[email protected]]
debug2: resolve_canonicalize: hostname 192.168.5.2 is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/root/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/root/.ssh/known_hosts2'
debug3: ssh_connect_direct: entering
debug1: Connecting to 192.168.5.2 [192.168.5.2] port 22.
debug3: set_sock_tos: set socket 3 IP_TOS 0x10
debug1: Connection established.
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa_sk type -1
debug1: identity file /root/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: identity file /root/.ssh/id_ed25519_sk type -1
debug1: identity file /root/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /root/.ssh/id_xmss type -1
debug1: identity file /root/.ssh/id_xmss-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.1
debug1: Remote protocol version 2.0, remote software version Cisco-1.25
debug1: compat_banner: match: Cisco-1.25 pat Cisco-1.* compat 0x60000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 192.168.5.2:22 as 'sshuser'
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,curve25519-sha256,[email protected],[email protected],ext-info-c
debug2: host key algorithms: ssh-ed25519,[email protected],[email protected],[email protected],ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
debug2: ciphers ctos: 3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],[email protected]
debug2: ciphers stoc: 3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],[email protected]
debug2: MACs ctos: hmac-sha1,hmac-sha1-96,hmac-sha2-256,hmac-sha2-512,hmac-md5,hmac-md5-96,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
debug2: MACs stoc: hmac-sha1,hmac-sha1-96,hmac-sha2-256,hmac-sha2-512,hmac-md5,hmac-md5-96,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa
debug2: ciphers ctos: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: MACs stoc: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: compression ctos: none
debug2: compression stoc: none
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: diffie-hellman-group1-sha1
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: 3des-cbc MAC: hmac-sha1 compression: none
debug1: kex: client->server cipher: 3des-cbc MAC: hmac-sha1 compression: none
debug2: bits set: 516/1024
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: SSH2_MSG_KEX_ECDH_REPLY received
ssh_dispatch_run_fatal: Connection to 192.168.5.2 port 22: Invalid key length
这是我使用 sshuser 连接 IP 为 192.168.5.3 的计算机时的另一个日志：
OpenSSH_8.9p1 Ubuntu-3ubuntu0.1, OpenSSL 3.0.2 15 Mar 2022
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 *
debug3: kex names ok: [diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,curve25519-sha256,[email protected],[email protected]]
debug2: resolve_canonicalize: hostname 192.168.5.3 is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/root/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/root/.ssh/known_hosts2'
debug3: ssh_connect_direct: entering
debug1: Connecting to 192.168.5.3 [192.168.5.3] port 22.
debug3: set_sock_tos: set socket 3 IP_TOS 0x10
debug1: Connection established.
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa_sk type -1
debug1: identity file /root/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: identity file /root/.ssh/id_ed25519_sk type -1
debug1: identity file /root/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /root/.ssh/id_xmss type -1
debug1: identity file /root/.ssh/id_xmss-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.1
debug1: Remote protocol version 2.0, remote software version Cisco-1.25
debug1: compat_banner: match: Cisco-1.25 pat Cisco-1.* compat 0x60000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 192.168.5.3:22 as 'sshuser'
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,curve25519-sha256,[email protected],[email protected],ext-info-c
debug2: host key algorithms: ssh-ed25519,[email protected],[email protected],[email protected],ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
debug2: ciphers ctos: 3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],[email protected]
debug2: ciphers stoc: 3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],[email protected]
debug2: MACs ctos: hmac-sha1,hmac-sha1-96,hmac-sha2-256,hmac-sha2-512,hmac-md5,hmac-md5-96,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
debug2: MACs stoc: hmac-sha1,hmac-sha1-96,hmac-sha2-256,hmac-sha2-512,hmac-md5,hmac-md5-96,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa
debug2: ciphers ctos: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: MACs stoc: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
debug2: compression ctos: none
debug2: compression stoc: none
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: diffie-hellman-group1-sha1
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: 3des-cbc MAC: hmac-sha1 compression: none
debug1: kex: client->server cipher: 3des-cbc MAC: hmac-sha1 compression: none
debug2: bits set: 534/1024
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-rsa SHA256:TG7Wfkw7J0jv8n7R7DXES8gMKF6oACeZ7Uh6aLKEb7o
debug3: record_hostkey: found key type RSA in file /root/.ssh/known_hosts:15
debug3: load_hostkeys_file: loaded 1 keys from 192.168.5.3
debug1: load_hostkeys: fopen /root/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host '192.168.5.3' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:15
debug2: bits set: 546/1024
debug3: send packet: type 21
debug2: ssh_set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: ssh_set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /root/.ssh/id_rsa
debug1: Will attempt key: /root/.ssh/id_ecdsa
debug1: Will attempt key: /root/.ssh/id_ecdsa_sk
debug1: Will attempt key: /root/.ssh/id_ed25519
debug1: Will attempt key: /root/.ssh/id_ed25519_sk
debug1: Will attempt key: /root/.ssh/id_xmss
debug1: Will attempt key: /root/.ssh/id_dsa
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 53
debug3: input_userauth_banner: entering
debug3: receive packet: type 51
debug1: Authentications that can continue: keyboard-interactive,password
debug3: start over, passed a different list keyboard-interactive,password
debug3: preferred gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug3: send packet: type 50
debug2: we sent a keyboard-interactive packet, wait for reply
debug3: receive packet: type 60
debug2: input_userauth_info_req: entering
debug2: input_userauth_info_req: num_prompts 1
([email protected]) Password:
我们首先查看的是 SSH 密钥长度。我们在客户端启用了 diffie-hellman-group1-sha1 协议，这是我们被要求使用的协议（在两个交换机上）。在几个论坛上，人们说问题在于 RSA 密钥的长度，因为 SSH 版本 7.6 不允许密钥短于 1024 位。但是，我们已经进行了相关测试，并验证了它在 IP 为 192.168.5.3 的 cisco 机器上建立连接并登录，尽管密钥长度小于 1024 位。在这台机器上，我们更改并生成了不同 RSA 密钥长度的 RSA 密钥，它可以通过 SSH 连接而没有任何问题（正如我在第二个 LOG 中所示）。我们使用了以下 cisco 命令：
conf t
crypto key zerosize rsa
crypto key generate rsa modulus <bits-size>
end
我们尝试安装'sudo apt 安装 openssh-client-ssh1'但是ubuntu机器已经有了。cisco机器要求我们在登录时使用以下kex算法和密码： ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 -c aes256-cbc[电子邮件保护]连接没有问题。但是 IP 为 192.168.5.2 的思科机器出现错误：'ssh_dispatch_run_fatal：连接到 192.168.5.2 端口 22：密钥长度无效'。当我们通过 ssh 从 ubuntu 22.04 登录到 cisco 交换机时，会发生所有这些情况。有一点需要注意。如果我使用 WinSSHTerm 程序并将其配置为使用 ubuntu 22.04 计算机作为动态 ssh 隧道，然后添加 cisco 计算机通过该隧道进行连接，则它可以毫无问题地连接。这就像 WinSSHTerm 客户端能够重新协商密钥一样。我不知道发生了什么。理想的情况是能够使用 ubuntu 机器而无需创建动态隧道来连接到 IP 为 192.168.5.2 的 cisco。启用协商良好的 ssh cli 客户端，而不必使用 WinSSHTerm。
答案1
理想情况是能够使用 ubuntu 机器而无需创建动态隧道来连接到 IP 为 192.168.5.2 的 cisco。启用协商良好的 ssh cli 客户端，而不必使用 WinSSHTerm。
安装“putty-tools”包，其中有一个名为 的 SSH 客户端plink。使用它代替ssh。
如果我使用 WinSSHTerm 程序并将其配置为使用 ubuntu 22.04 计算机作为动态 ssh 隧道，然后添加 cisco 计算机通过该隧道进行连接，则它可以毫无问题地连接。就好像 WinSSHTerm 客户端能够重新协商密钥一样
不，它只是没有像 OpenSSH 那样自我强加的限制。
通过 Ubuntu 机器连接并不意味着您正在使用 Ubuntu 机器上的 SSH 客户端——Ubuntu 机器所做的只是承载原始 TCP 流。