為什麼 ssh 代理轉發不起作用？

在我自己的電腦上，執行 MacOSX，我在 ~/.ssh/config 中有這個

Host *
ForwardAgent yes
Host b1
ForwardAgent yes

b1 是執行 Ubuntu 12.04 的虛擬機。我像這樣 ssh 到它：

ssh pupeno@b1

我在沒有被要求輸入密碼的情況下登錄，因為我已經複製了我的公鑰。由於轉發，我應該能夠從 b1 ssh 到 pupeno@b1 並且它應該可以工作，而不需要我輸入密碼，但它沒有。它要求我輸入密碼。

我錯過了什麼？

這是第二個 ssh 的詳細輸出：

pupeno@b1:~$ ssh -v pupeno@b1
OpenSSH_5.9p1 Debian-5ubuntu1, OpenSSL 1.0.1 14 Mar 2012
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to b1 [127.0.1.1] port 22.
debug1: Connection established.
debug1: identity file /home/pupeno/.ssh/id_rsa type -1
debug1: identity file /home/pupeno/.ssh/id_rsa-cert type -1
debug1: identity file /home/pupeno/.ssh/id_dsa type -1
debug1: identity file /home/pupeno/.ssh/id_dsa-cert type -1
debug1: identity file /home/pupeno/.ssh/id_ecdsa type -1
debug1: identity file /home/pupeno/.ssh/id_ecdsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1
debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.9p1 Debian-5ubuntu1
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: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ECDSA 35:c0:7f:24:43:06:df:a0:bc:a7:34:4b:da:ff:66:eb
debug1: Host 'b1' is known and matches the ECDSA host key.
debug1: Found key in /home/pupeno/.ssh/known_hosts:1
debug1: ssh_ecdsa_verify: signature correct
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,password
debug1: Next authentication method: publickey
debug1: Trying private key: /home/pupeno/.ssh/id_rsa
debug1: Trying private key: /home/pupeno/.ssh/id_dsa
debug1: Trying private key: /home/pupeno/.ssh/id_ecdsa
debug1: Next authentication method: password
pupeno@b1's password:

原來我的鑰匙不在代理中，這修復了它：

作業系統：

ssh-add -K

Linux/Unix：

ssh-add -k

您可以使用以下命令列出載入的密鑰：

ssh-add -l

ssh-add -L # for more detail

另一個可能的原因是連接共享：一個可能已經在另一台主機上登錄而沒有啟用代理轉發和連接共享。ssh -A通過共享連接使用（或等效地在配置文件中指定）的第二次登錄將靜默忽略該-A標誌。只有在完全註銷或禁用第二次登錄的連接共享後，代理轉發才會起作用。

引用自：https://serverfault.com/questions/404447