我有一個在 CentOS Linux 7.7 上運行的 Python 3 應用程式，它對遠程主機執行 SSH 命令。它作業正常，但今天我在對“新”遠程服務器（基于 RHEL 6.10 的服務器）執行命令時遇到了一個奇怪的錯誤：
encountered RSA key, expected OPENSSH key
從系統外殼執行相同的命令（當然使用相同的私鑰）作業得很好。
在遠程服務器上，我在 /var/log/secure 中發現，當使用 Python（使用 Paramiko）從源服務器發出 SSH 連接和命令時，sshd 會抱怨不支持的公鑰演算法：
userauth_pubkey: unsupported public key algorithm: rsa-sha2-512
請注意，具有更高 RHEL/CentOS（如 7.x）的目標服務器不會遇到此問題。
當與遠程服務器協商時，Paramiko 似乎選擇/提供了錯誤的演算法，而相反，SSH shell 在這個“舊”目標服務器的背景關系中正確執行協商。如何讓 Python 程式按預期作業？
Python代碼
import paramiko
import logging
ssh_user = "my_user"
ssh_keypath = "/path/to/.ssh/my_key.rsa"
server = "server.tld"
ssh_client = paramiko.SSHClient()
ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh_client.connect(server,port=22,username=ssh_user, key_filename=ssh_keypath)
# SSH command
cmd = "echo TEST : $(hostname)"
stdin, stdout, stderr = ssh_client.exec_command(cmd, get_pty=True)
exit_code = stdout.channel.recv_exit_status()
cmd_raw_output = stdout.readlines()
out = "".join(cmd_raw_output)
out_msg = out.strip()
# Ouput (logger code omitted)
logger.debug(out_msg)
if ssh_client is not None:
ssh_client.close()
Shell 命令等效項
ssh -i /path/to/.ssh/my_key.rsa [email protected] "echo TEST : $(hostname)"
Paramiko 日志（除錯）
DEB [YYYYmmdd-HH:MM:30.475] thr=1 paramiko.transport: starting thread (client mode): 0xf6054ac8
DEB [YYYYmmdd-HH:MM:30.476] thr=1 paramiko.transport: Local version/idstring: SSH-2.0-paramiko_2.9.1
DEB [YYYYmmdd-HH:MM:30.490] thr=1 paramiko.transport: Remote version/idstring: SSH-2.0-OpenSSH_5.3
INF [YYYYmmdd-HH:MM:30.490] thr=1 paramiko.transport: Connected (version 2.0, client OpenSSH_5.3)
DEB [YYYYmmdd-HH:MM:30.498] thr=1 paramiko.transport: === Key exchange possibilities ===
DEB [YYYYmmdd-HH:MM:30.498] thr=1 paramiko.transport: kex algos: diffie-hellman-group-exchange-sha256, diffie-hellman-group-exchange-sha1, diffie-hellman-group14-sha1, diffie-hellman-group1-sha1
DEB [YYYYmmdd-HH:MM:30.498] thr=1 paramiko.transport: server key: ssh-rsa, ssh-dss
DEB [YYYYmmdd-HH:MM:30.498] thr=1 paramiko.transport: client encrypt: aes128-ctr, aes192-ctr, aes256-ctr, arcfour256, arcfour128, aes128-cbc, 3des-cbc, blowfish-cbc, cast128-cbc, aes192-cbc, aes256-cbc, arcfour, [email protected]
DEB [YYYYmmdd-HH:MM:30.498] thr=1 paramiko.transport: server encrypt: aes128-ctr, aes192-ctr, aes256-ctr, arcfour256, arcfour128, aes128-cbc, 3des-cbc, blowfish-cbc, cast128-cbc, aes192-cbc, aes256-cbc, arcfour, [email protected]
DEB [YYYYmmdd-HH:MM:30.499] thr=1 paramiko.transport: client mac: hmac-md5, hmac-sha1, umac-64@openssh.com, hmac-sha2-256, hmac-sha2-512, hmac-ripemd160, [email protected], hmac-sha1-96, hmac-md5-96
DEB [YYYYmmdd-HH:MM:30.499] thr=1 paramiko.transport: server mac: hmac-md5, hmac-sha1, umac-64@openssh.com, hmac-sha2-256, hmac-sha2-512, hmac-ripemd160, [email protected], hmac-sha1-96, hmac-md5-96
DEB [YYYYmmdd-HH:MM:30.499] thr=1 paramiko.transport: client compress: none, [email protected]
DEB [YYYYmmdd-HH:MM:30.499] thr=1 paramiko.transport: server compress: none, [email protected]
DEB [YYYYmmdd-HH:MM:30.499] thr=1 paramiko.transport: client lang: <none>
DEB [YYYYmmdd-HH:MM:30.499] thr=1 paramiko.transport: server lang: <none>.
DEB [YYYYmmdd-HH:MM:30.499] thr=1 paramiko.transport: kex follows: False
DEB [YYYYmmdd-HH:MM:30.500] thr=1 paramiko.transport: === Key exchange agreements ===
DEB [YYYYmmdd-HH:MM:30.500] thr=1 paramiko.transport: Kex: diffie-hellman-group-exchange-sha256
DEB [YYYYmmdd-HH:MM:30.500] thr=1 paramiko.transport: HostKey: ssh-rsa
DEB [YYYYmmdd-HH:MM:30.500] thr=1 paramiko.transport: Cipher: aes128-ctr
DEB [YYYYmmdd-HH:MM:30.500] thr=1 paramiko.transport: MAC: hmac-sha2-256
DEB [YYYYmmdd-HH:MM:30.501] thr=1 paramiko.transport: Compression: none
DEB [YYYYmmdd-HH:MM:30.501] thr=1 paramiko.transport: === End of kex handshake ===
DEB [YYYYmmdd-HH:MM:30.548] thr=1 paramiko.transport: Got server p (2048 bits)
DEB [YYYYmmdd-HH:MM:30.666] thr=1 paramiko.transport: kex engine KexGexSHA256 specified hash_algo <built-in function openssl_sha256>
DEB [YYYYmmdd-HH:MM:30.667] thr=1 paramiko.transport: Switch to new keys ...
DEB [YYYYmmdd-HH:MM:30.669] thr=2 paramiko.transport: Adding ssh-rsa host key for server.tld: b'caea********************.'
DEB [YYYYmmdd-HH:MM:30.674] thr=2 paramiko.transport: Trying discovered key b'b49c********************' in /path/to/.ssh/my_key.rsa
DEB [YYYYmmdd-HH:MM:30.722] thr=1 paramiko.transport: userauth is OK
DEB [YYYYmmdd-HH:MM:30.722] thr=1 paramiko.transport: Finalizing pubkey algorithm for key of type 'ssh-rsa'
DEB [YYYYmmdd-HH:MM:30.722] thr=1 paramiko.transport: Our pubkey algorithm list: ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-rsa']
DEB [YYYYmmdd-HH:MM:30.723] thr=1 paramiko.transport: Server-side algorithm list: ['']
DEB [YYYYmmdd-HH:MM:30.723] thr=1 paramiko.transport: Agreed upon 'rsa-sha2-512' pubkey algorithm
INF [YYYYmmdd-HH:MM:30.735] thr=1 paramiko.transport: Authentication (publickey) failed.
DEB [YYYYmmdd-HH:MM:30.739] thr=2 paramiko.transport: Trying SSH agent key b'9d37********************'
DEB [YYYYmmdd-HH:MM:30.747] thr=1 paramiko.transport: userauth is OK.
DEB [YYYYmmdd-HH:MM:30.748] thr=1 paramiko.transport: Finalizing pubkey algorithm for key of type 'ssh-rsa'
DEB [YYYYmmdd-HH:MM:30.748] thr=1 paramiko.transport: Our pubkey algorithm list: ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-rsa']
DEB [YYYYmmdd-HH:MM:30.748] thr=1 paramiko.transport: Server-side algorithm list: ['']
DEB [YYYYmmdd-HH:MM:30.748] thr=1 paramiko.transport: Agreed upon 'rsa-sha2-512' pubkey algorithm
INF [YYYYmmdd-HH:MM:30.868] thr=1 paramiko.transport: Authentication (publickey) failed...
Shell 命令日志
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug2: resolving "server.tld" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to server.tld [server.tld] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: key_load_public: No such file or directory
debug1: identity file /path/to/.ssh/my_key.rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /path/to/.ssh/my_key.rsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH_5* compat 0x0c000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to server.tld:22 as 'my_user'
debug3: hostkeys_foreach: reading file "/path/to/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /path/to/.ssh/known_hosts:82
debug3: load_hostkeys: loaded 1 keys from server.tld
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],rsa-sha2-512,rsa-sha2-256,ssh-rsa
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: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1,ext-info-c
debug2: host key algorithms: [email protected],rsa-sha2-512,rsa-sha2-256,ssh-rsa,[email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,ssh-dss
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: umac-64[email protected],umac-128[email protected],hmac-sha2-256[email protected],hmac-sha2-512[email protected],[email protected],umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64[email protected],umac-128[email protected],hmac-sha2-256[email protected],hmac-sha2-512[email protected],[email protected],umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
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-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa,ssh-dss
debug2: ciphers ctos: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: ciphers stoc: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: MACs ctos: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: MACs stoc: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: diffie-hellman-group-exchange-sha256
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: aes128-ctr MAC: umac-64@openssh.com compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: umac-64@openssh.com compression: none
debug1: kex: diffie-hellman-group-exchange-sha256 need=16 dh_need=16
debug1: kex: diffie-hellman-group-exchange-sha256 need=16 dh_need=16
debug3: send packet: type 34
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<3072<8192) sent
debug3: receive packet: type 31
debug1: got SSH2_MSG_KEX_DH_GEX_GROUP
debug2: bits set: 1502/3072
debug3: send packet: type 32
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug3: receive packet: type 33
debug1: got SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Server host key: ssh-.:**************************************************
debug3: hostkeys_foreach: reading file "/path/to/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /path/to/.ssh/known_hosts:8..2
debug3: load_hostkeys: loaded 1 keys from server.tld
debug1: Host 'server.tld' is known and matches the RSA host key.
debug1: Found key in /path/to/.ssh/known_hosts:82
debug2: bits set: 1562/3072
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 4294967296 blocks
debug2: key: <foo> (0x55bcf6d1d320), agent
debug2: key: /path/to/.ssh/my_key.rsa ((nil)), explicit
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 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic,password
debug3: preferred gssapi-keyex,gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup gssapi-keyex
debug3: remaining preferred: gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-keyex
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug2: we did not send a packet, disable method
debug3: authmethod_lookup gssapi-with-mic
debug3: remaining preferred: publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-with-mic
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure. Minor code may provide more information
No Kerberos credentials available (default cache: KEYRING:persistent:0)
debug1: Unspecified GSS failure. Minor code may provide more information
No Kerberos credentials available (default cache: KEYRING:persistent:0)
debug2: we did not send a packet, disable method
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: <foo>
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Trying private key: /path/to/.ssh/my_key.rsa
debug3: sign_and_send_pubkey: RSA SHA256:**********************************
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (publickey).
Authenticated to server.tld ([server.tld]:22).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 91
debug2: callback start
debug2: fd 3 setting TCP_NODELAY
debug3: ssh_packet_set_tos: set IP_TOS 0x08
debug2: client_session2_setup: id 0
debug1: Sending environment.
debug3: Ignored env XDG_SESSION_ID
debug3: Ignored env HOSTNAME
debug3: Ignored env SELINUX_ROLE_REQUESTED
debug3: Ignored env TERM
debug3: Ignored env SHELL
debug3: Ignored env HISTSIZE
debug3: Ignored env SSH_CLIENT
debug3: Ignored env SELINUX_USE_CURRENT_RANGE
debug3: Ignored env SSH_TTY
debug3: Ignored env CDPATH
debug3: Ignored env USER
debug3: Ignored env LS_COLORS
debug3: Ignored env SSH_AUTH_SOCK
debug3: Ignored env MAIL
debug3: Ignored env PATH
debug3: Ignored env PWD
debug1: Sending env LANG = xx_XX.UTF-8
debug2: channel 0: request env confirm 0
debug3: send packet: type 98
debug3: Ignored env SELINUX_LEVEL_REQUESTED
debug3: Ignored env HISTCONTROL
debug3: Ignored env SHLVL
debug3: Ignored env HOME
debug3: Ignored env LOGNAME
debug3: Ignored env SSH_CONNECTION
debug3: Ignored env LESSOPEN
debug3: Ignored env XDG_RUNTIME_DIR
debug3: Ignored env _
debug1: Sending command: echo TEST : $(hostname)
debug2: channel 0: request exec confirm 1
debug3: send packet: type 98
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel 0: rcvd adjust 2097152
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: exec request accepted on channel 0
TEST : server.tld
debug3: receive packet: type 96
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: obuf empty
debug2: channel 0: close_write
debug2: channel 0: output drain -> closed
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype [email protected] reply 0
debug2: channel 0: rcvd eow
debug2: channel 0: close_read
debug2: channel 0: input open -> closed
debug3: receive packet: type 97
debug2: channel 0: rcvd close
debug3: channel 0: will not send data after close
debug2: channel 0: almost dead
debug2: channel 0: gc: notify user
debug2: channel 0: gc: user detached
debug2: channel 0: send close
debug3: send packet: type 97
debug2: channel 0: is dead
debug2: channel 0: garbage collecting
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
#0 client-session (t4 r0 i3/0 o3/0 fd -1/-1 cc -1)
debug3: send packet: type 1
Transferred: sent 3264, received 2656 bytes, in 0.0 seconds.
Bytes per second: sent 92349.8, received 75147.4
debug1: Exit status 0
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uj5u.com熱心網友回復：
Imo，這是Paramiko 中的一個錯誤。它不能正確處理server-sig-algs服務器端沒有擴展名的情況。
嘗試rsa-sha2-512完全禁用Paramiko 端：
ssh_client.connect(
server, username=ssh_user, key_filename=ssh_keypath,
disabled_algorithms=dict(pubkeys=["rsa-sha2-512"]))
（請注意，無需指定port=22，因為這是默認設定）
我發現了相關的 Paramiko 問題：
RSA key auth failed from paramiko 2.9.x client to dropbear server
雖然它指的是Paramiko 2.9.0 更改日志，但這似乎暗示該行為是故意的：
當服務器沒有發送時
server-sig-algs，Paramiko 將嘗試上面串列中的第一個演算法。因此，連接到舊服務器的客戶端應該disabled_algorithms用來關閉 SHA2。
強制性警告：請勿使用AutoAddPolicy-這樣做您將失去針對MITM 攻擊的保護。有關正確的解決方案，請參閱Paramiko“未知服務器”。
您等待命令完成并讀取其輸出的代碼也存在缺陷。請參閱等待完成使用 Python Paramiko 執行的命令。對于大多數目的，這get_pty=True也不是一個好主意。
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