问题描述：
在Mac OS 系统中，当我们使用Terminal通过ssh去连接一个远程主机，可能会遇到以下报错：
JUNLI5-M-R24U:~ junli$ ssh admin@10.75.169.43
Unable to negotiate with 10.75.169.43 port 22: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1
解决方案
Terminal找不到支持的密钥交换方法，因为新版Openssh中认为SHA1这种hash散列算法过于薄弱，已经不再支持，所以我们需要手动去enable对于SHA1的支持：
JUNLI5-M-R24U:ssh junli$ vim /etc/ssh/ssh_config
取消注释这一行内容： MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160
并且在文件结尾添加：
HostkeyAlgorithms ssh-dss,ssh-rsa
KexAlgorithms +diffie-hellman-group1-sha1
编辑后/etc/ssh/ssh_config完整的文件内容如下：
# $OpenBSD: ssh_config,v 1.30 2016/02/20 23:06:23 sobrado Exp $
# This is the ssh client system-wide configuration file. See
# ssh_config(5) for more information. This file provides defaults for
# users, and the values can be changed in per-user configuration files
# or on the command line.
# Configuration data is parsed as follows:
# 1. command line options
# 2. user-specific file
# 3. system-wide file
# Any configuration value is only changed the first time it is set.
# Thus, host-specific definitions should be at the beginning of the
# configuration file, and defaults at the end.
# Site-wide defaults for some commonly used options. For a comprehensive
# list of available options, their meanings and defaults, please see the
# ssh_config(5) man page.
# Host *
# ForwardAgent no
# ForwardX11 no
# RhostsRSAAuthentication no
# RSAAuthentication yes
# PasswordAuthentication yes
# HostbasedAuthentication no
# GSSAPIAuthentication no
# GSSAPIDelegateCredentials no
# BatchMode no
# CheckHostIP yes
# AddressFamily any
# ConnectTimeout 0
# StrictHostKeyChecking ask
# IdentityFile ~/.ssh/identity
# IdentityFile ~/.ssh/id_rsa
# IdentityFile ~/.ssh/id_dsa
# IdentityFile ~/.ssh/id_ecdsa
# IdentityFile ~/.ssh/id_ed25519
# Port 22
# Protocol 2
# Cipher 3des
# Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160
# EscapeChar ~
# Tunnel no
# TunnelDevice any:any
# PermitLocalCommand no
# VisualHostKey no
# ProxyCommand ssh -q -W %h:%p gateway.example.com
# RekeyLimit 1G 1h
HostkeyAlgorithms ssh-dss,ssh-rsa
KexAlgorithms +diffie-hellman-group1-sha1
配置完无需重启。
