macOS ssh error: unable to negot

环境：macOS Mojava version 10.14

在更新了Mac OS以后用ssh push 代码到服务器出现了下面这个错误。

ssh error: unable to negotiate with IP: no matching cipher found.Their offer: aes256-cbc,aes192-cbc,aes128-cbc...

Unable to negotiate with XX.X.X.XXX port XX: no matching cipher found. Their offer: aes256-cbc,aes192-cbc,aes128-cbc
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

出现错误的原因是要连接的代码仓库服务端的ssh版本过低，客户端与服务端的 cipher 没有匹配上，我们需要在自己的客户端（升级OS后的Mac）重新启用老的 cipher ,这样就能重新建立起连接了。

具体步骤如下：

第一步：terminal 输入 sudo nano /etc/ssh/ssh_config

atcs-air:~ XXX$ sudo nano /etc/ssh/ssh_config

第二步：找到 Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc，删除这行前面的#号。

# Host *
#   ForwardAgent no
#   ForwardX11 no
#   PasswordAuthentication yes
#   HostbasedAuthentication no
#   GSSAPIAuthentication no
#   GSSAPIDelegateCredentials no
#   BatchMode no
#   CheckHostIP yes
#   AddressFamily any
#   ConnectTimeout 0
#   StrictHostKeyChecking ask
#   IdentityFile ~/.ssh/id_rsa
#   IdentityFile ~/.ssh/id_dsa
#   IdentityFile ~/.ssh/id_ecdsa
#   IdentityFile ~/.ssh/id_ed25519
#   Port 22
#   Protocol 2
   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc
#   MACs hmac-md5,hmac-sha1,umac-64@openssh.com
#   EscapeChar ~
#   Tunnel no
#   TunnelDevice any:any
#   PermitLocalCommand no
#   VisualHostKey no
#   ProxyCommand ssh -q -W %h:%p gateway.example.com
#   RekeyLimit 1G 1h

Host *
        SendEnv LANG LC_*

第三步：保存 ssh_config 这个文件，退出，然后就可以和以前一样通过ssh连接代码仓库服务器了。

参考链接：
https://www.itechlounge.net/2018/01/macos-unable-to-negotiate-with-0-0-0-0-port-22-no-matching-cipher-found/

https://discussions.apple.com/thread/8196671?answerId=32716986022#32716986022