问题

Permissions 0644 for 'xx.pem' are too open. It is required that your private key files are NOT accessible by others. This private key will be ignored. Load key "xx.pem": bad permissions ec2-user@35.77.46.6: Permission denied (publickey,gssapi-keyex,gssapi-with-mic). lost connection

解决方案

看日志报出的错误，"Permissions 0644 for 'xx.pem' are too open"，pen文件的权限太大太open了。
使用ll(ls -al)命令查看了私钥文件的权限，发现和错误一样，是644
所以需要使用chmod命令修改文件的权限

chmod 600 xx.pem
之后再尝试一遍，完美执行