Ssh

SSH config ProxyCommand 請求公鑰

  • September 28, 2015

我正在嘗試通過網關連接到 EC2 實例。

如果我連接到網關

local> ssh gateway

然後我可以在沒有密碼的情況下連接到 EC2

gateway> ssh ec2  # works

但是，嘗試通過代理連接似乎需要身份文件。

Host gateway
   HostName <gateway>

Host ec2
   HostName ec2-<ec2>.compute.amazonaws.com
   ProxyCommand ssh gateway -W %h:%p


local> ssh ec2
Permission denied (publickey).

我認為 ProxyCommand 基本上是將我登錄到網關，然後登錄到最終目的地。如果是這樣，當網關設置為不需要公鑰時，為什麼它會要求我提供公鑰？如何以與 ssh 連接到網關然後 ssh 連接到 ec2 相同的方式連接到 ec2 實例？

編輯： rsync 正常工作（不要求密鑰文件）

rsync -pthrvz  --rsync-path=/usr/bin/rsync --rsh='ssh gateway ssh' . ec2:/path

ssh -v 輸出gateway> ssh ec2

gateway> ssh -v ec2
OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to ec2 port 22.
debug1: Connection established.
debug1: identity file <snip> type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.2
debug1: match: OpenSSH_6.2 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'ec2' is known and matches the RSA host key.
debug1: Found key in ~/.ssh/known_hosts:63
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: ~/.ssh/identity
debug1: Offering public key: ~/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 277
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: Sending environment.

ssh -v 嘗試通過代理連接的輸出

local$ ssh -v ec2 
OpenSSH_6.7p1 Ubuntu-5ubuntu1.3, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /home/matt/.ssh/config
debug1: /home/matt/.ssh/config line 9: Applying options for ec2
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Hostname has changed; re-reading configuration
debug1: Reading configuration data /home/matt/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Executing proxy command: exec ssh gateway -W ec2:22
debug1: permanently_drop_suid: 1000
debug1: identity file /home/matt/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/matt/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/matt/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/matt/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/matt/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/matt/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/matt/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/matt/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.7p1 Ubuntu-5ubuntu1.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.2
debug1: match: OpenSSH_6.2 pat OpenSSH* compat 0x04000000
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr umac-64-etm@openssh.com none
debug1: kex: client->server aes128-ctr umac-64-etm@openssh.com none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ECDSA 73:<snip>:0c
debug1: Host 'ec2.compute.amazonaws.com' is known and matches the ECDSA host key.
debug1: Found key in /home/matt/.ssh/known_hosts:11
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/matt/.ssh/id_rsa
debug1: Authentications that can continue: publickey
debug1: Trying private key: /home/matt/.ssh/id_dsa
debug1: Trying private key: /home/matt/.ssh/id_ecdsa
debug1: Trying private key: /home/matt/.ssh/id_ed25519
debug1: No more authentication methods to try.
Permission denied (publickey).

問題似乎是它試圖在我的機器上找到密鑰，而不是從網關機器上獲取它。

ProxyCommand 不像你想像的那樣工作。指定的命令不在網關機器上執行。相反，它在連接的機器上執行。

因此，執行流程是：

  1. ProxyCommand“ssh gateway -W %h:%p”在“本地”機器上執行。這將使用本地機器上的 RSA 身份建立到網關的 SSH 會話。-W 標誌指定 stdin 和 stdout 將連接到網關上的 TCP 會話發起到您的最終目的地。
  2. 建立代理會話後，本地機器上的 ssh 再次使用該會話向遠端 SSH 伺服器進行身份驗證，再次使用本地憑據。

這有點令人困惑，但可以將 ProxyCommand 視為在本地 SSH 客戶端和作為最終目的地的 SSH 伺服器之間簡單地設置“管道”。然後，您的本地 SSH 客戶端使用該啞管道與最終目的地的 SSH 服務通信。

關鍵是因此在您的本地機器上執行了兩個SSH 實例，其中一個是 ProxyCommand，另一個是您要建立的實際 SSH 連接！您應該能夠通過查看本地機器上“ps aux”的輸出來驗證這一點。

這將解釋為什麼它試圖在您的本地盒子上使用密鑰材料，而不是在您的網關上進行身份驗證。:-)

rsync 起作用的原因是，您實際上是在執行“ssh gateway ssh”作為您的 –rsh 命令，它實際上在本地機器上執行 ssh 一次以連接到網關，然後在遠端機器上再次執行，這將然後使用遙控鑰匙材料。

希望這可以幫助。

引用自：https://serverfault.com/questions/724721

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