Openssh
為什麼我可以在沒有密碼或私鑰的情況下登錄遠端主機？
我在這裡使用 Openwrt，我發現我可以在沒有密碼或私鑰的情況下登錄遠端主機。我在 System->Administration 選項卡中添加了一個 SSH-Keys（公鑰），這個公鑰是與遠端主機私鑰的密鑰對。
我以為 ssh 客戶端必須使用私鑰登錄，這裡的情況似乎使用了公鑰？
SSH 調試日誌：
root@OpenWrt:~# ssh <HOST> -p 443 -vvv OpenSSH_6.8p1, OpenSSL 1.0.2e 3 Dec 2015 debug1: Reading configuration data /etc/ssh/ssh_config debug2: ssh_connect: needpriv 0 debug1: Connecting to <HOST> [<HOST>] port 443. debug1: Connection established. debug1: permanently_set_uid: 0/0 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_rsa type -1 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_rsa-cert type -1 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_dsa type -1 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_dsa-cert type -1 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_ecdsa type -1 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_ecdsa-cert type -1 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_ed25519 type -1 debug1: key_load_public: No such file or directory debug1: identity file /root/.ssh/id_ed25519-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.8 debug1: Remote protocol version 2.0, remote software version dropbear_2011.54 debug1: no match: dropbear_2011.54 debug2: fd 3 setting O_NONBLOCK debug3: put_host_port: [<HOST>]:443 debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts" debug3: record_hostkey: found key type RSA in file /root/.ssh/known_hosts:1 debug3: load_hostkeys: loaded 1 keys from [<HOST>]:443 debug3: order_hostkeyalgs: prefer hostkeyalgs: ssh-rsa-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-rsa debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug2: kex_parse_kexinit: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: ssh-rsa-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-rsa,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-dss-cert-v00@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-dss debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-md5-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-md5-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: kex_parse_kexinit: diffie-hellman-group1-sha1,diffie-hellman-group14-sha1 debug2: kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit: aes128-ctr,3des-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes256-cbc debug2: kex_parse_kexinit: aes128-ctr,3des-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes256-cbc debug2: kex_parse_kexinit: hmac-sha1,hmac-md5 debug2: kex_parse_kexinit: hmac-sha1,hmac-md5 debug2: kex_parse_kexinit: none debug2: kex_parse_kexinit: none debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug1: kex: server->client aes128-ctr hmac-sha1 none debug1: kex: client->server aes128-ctr hmac-sha1 none debug1: sending SSH2_MSG_KEXDH_INIT debug2: bits set: 1004/2048 debug1: expecting SSH2_MSG_KEXDH_REPLY debug1: Server host key: ssh-rsa SHA256:H/MgAoUz/bDefD1KiHrrpPjo8BOqXqUDPd0bhlJr4eE debug3: put_host_port: [<HOST>]:443 debug3: put_host_port: [<HOST>]:443 debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts" debug3: record_hostkey: found key type RSA in file /root/.ssh/known_hosts:1 debug3: load_hostkeys: loaded 1 keys from [<HOST>]:443 debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts" debug3: record_hostkey: found key type RSA in file /root/.ssh/known_hosts:1 debug3: load_hostkeys: loaded 1 keys from [<HOST>]:443 debug1: Host '[<HOST>]:443' is known and matches the RSA host key. debug1: Found key in /root/.ssh/known_hosts:1 debug2: bits set: 1008/2048 debug2: set_newkeys: mode 1 debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug2: set_newkeys: mode 0 debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: root@palm-webos (0x77d53ee0), debug2: key: /root/.ssh/id_rsa ((nil)), debug2: key: /root/.ssh/id_dsa ((nil)), debug2: key: /root/.ssh/id_ecdsa ((nil)), debug2: key: /root/.ssh/id_ed25519 ((nil)), debug1: Authentications that can continue: publickey debug3: start over, passed a different list publickey 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: root@palm-webos debug3: send_pubkey_test debug2: we sent a publickey packet, wait for reply debug1: Server accepts key: pkalg ssh-rsa blen 279 debug2: input_userauth_pk_ok: fp SHA256:wfA3yC7+sEIeTSQp6NUmP14XlgEX5WuJyVoL9m3WrX4 debug3: sign_and_send_pubkey: RSA SHA256:wfA3yC7+sEIeTSQp6NUmP14XlgEX5WuJyVoL9m3WrX4 debug1: Authentication succeeded (publickey). Authenticated to <HOST> ([<HOST>]:443). debug1: channel 0: new [client-session] debug3: ssh_session2_open: channel_new: 0 debug2: channel 0: send open debug1: Entering interactive session. debug2: callback start debug2: fd 3 setting TCP_NODELAY debug3: ssh_packet_set_tos: set IP_TOS 0x10 debug2: client_session2_setup: id 0 debug2: channel 0: request pty-req confirm 1 debug2: channel 0: request shell confirm 1 debug2: callback done debug2: channel 0: open confirm rwindow 24576 rmax 32768 debug2: channel_input_status_confirm: type 99 id 0 debug2: PTY allocation request accepted on channel 0 debug2: channel_input_status_confirm: type 99 id 0 debug2: shell request accepted on channel 0我搜尋了
id_rsa文件，但什麼也沒找到root@OpenWrt:~# find / -type f -name id_rsa左邊是問題一，右邊是使用私鑰正常ssh登錄：
更新：更新ssh調試到3級和正常私鑰登錄的對比圖。
debug3: sign_and_send_pubkey: RSA SHA256:wfA3yC7+sEIeTSQp6NUmP14XlgEX5WuJyVoL9m3WrX4 debug1: Authentication succeeded (publickey). Authenticated to <HOST> ([<HOST>]:443).表示您正在使用公鑰身份驗證，成功了。密鑰沒有路徑，很可能是因為它是由
ssh-agent.更新：更新ssh調試到3級和正常私鑰登錄的對比圖。
在圖像中，您將使用一個私鑰的連接與使用不同私鑰的連接進行比較。不同的是，第一個是先發送公鑰測試，驗證是否成功，第二個直接發送簽名，不做這個測試。RFC 4252 第 7 節中描述了有什麼區別