ssh 连接慢问题

连接先看报错：

There were 11 failed login attempts since the last successful login.

先前有上百上千失败login，被攻击了，把短时间尝试登录失败的ip加入黑名单

写个脚本：

#! /bin/bash
cat /var/log/secure|awk '/Failed/{print $(NF-3)}'|sort|uniq -c|awk '{print $2"="$1;}' > /root/black.txt
DEFINE="10"
for i in `cat  /root/black.txt`
do
    IP=`echo | awk '{split("'${i}'", array, "=");print array[1]}'`
    NUM=`echo | awk '{split("'${i}'", array, "=");print array[2]}'`
    if [ $NUM -gt $DEFINE ];then
     grep $IP /etc/hosts.deny > /dev/null
      if [ $? -gt 0 ];then
          echo "sshd:$IP:deny" >> /etc/hosts.deny
      fi
    fi
done　

然后定时执行

crontab -e

*/ * * * *  sh /root/secure_ssh.sh

一分钟执行一次

攻击解决了，但是还是慢

其中xintd安装失败，yum镜像连不上所以换了

    -- :: cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
    -- :: cd /etc/yum.repos.d/
    -- :: wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
    -- :: yum makecache
    -- :: yum -y update
    -- :: vi
    -- :: yum install xinetd.x86_64
    -- :: service xinetd start
    -- :: /bin/systemctl start xinetd.service

各种修改/etc/resolv.conf

#nameserver 183.60.83.19
nameserver 8.8.8.8
nameserver 114.114.114.114
#nameserver 183.60.82.98
#search localdomain
#options timeout: rotate

重启网络

/etc/init.d/network restart

不起作用

把网上流行做法，都做了

systemcts status systemd-logind

因为确实有login超时

也顺便

systemctl restart dbus

了一下，没用

费力气安装stract，用它来查看栈信息

strace -o ~/starce_ssh.txt -T ssh localhost

tail -f ~/starce_ssh.txt

但是看不懂。。。。。。

下面的肯定先做了

vim /etc/ssh/sshd_config

做

UseDNS no

#service sshd restart

修改GSSAPIAuthentication参数为 no，默认是yes

#service sshd restart

显然是没用，采用上上面的方法

也调试日志了

ssh  -vvv root@*.*.*.*

输入密码后，在这里等待

debug1: Next authentication method: password
root@*********'s password:
debug3: packet_send2: adding  (len  padlen  extra_pad )
debug2: we sent a password packet, wait for reply
debug3: Wrote  bytes for a total of
debug1: Authentication succeeded (password).
debug1: channel : new [client-session]
debug3: ssh_session2_open: channel_new:
debug2: channel : send open
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug3: Wrote  bytes for a total of 

很久以后

debug1: Entering interactive session.
debug3: Wrote  bytes for a total of
debug1: client_input_global_request: rtype hostkeys-@openssh.com want_reply
debug2: callback start
debug2: client_session2_setup: id
debug2: channel : request pty-req confirm
debug2: channel : request shell confirm
debug2: fd  setting TCP_NODELAY
debug2: callback done
debug2: channel : open confirm rwindow  rmax
debug3: Wrote  bytes for a total of
debug2: channel_input_status_confirm: type  id
debug2: PTY allocation request accepted on channel
debug2: channel : rcvd adjust
debug2: channel_input_status_confirm: type  id
debug2: shell request accepted on channel
Last failed login: Thu Jun  :: CST  from 112.85.42.201 on ssh:notty
There were  failed login attempts since the last successful login.
Last login: Thu Jun  ::  from 124.204.55.194
[root@VM_128_5_centos ~]#

分析了很久很多停顿时候以及前后的打印信息，对比

这些客户端信息正常

查看服务器日志：

tail -f /var/log/messages

登录时认证很快，并创建session

Jun  :: localhost systemd: Started Session  of user root.
Jun  :: localhost systemd-logind: New session  of user root.
Jun  :: localhost systemd: Starting Session  of user root.

详细日志

Jun  :: localhost sshd[]: Accepted password for root from 124.204.55.194 port  ssh2
Jun  :: localhost systemd: Started Session  of user root.
Jun  :: localhost systemd-logind: New session  of user root.
Jun  :: localhost systemd: Starting Session  of user root.
Jun  :: localhost systemd: Started Session  of user root.
Jun  :: localhost systemd: Starting Session  of user root.
Jun  :: localhost systemd: Started Session  of user root.
Jun  :: localhost systemd: Starting Session  of user root.
Jun  :: localhost systemd: Started Session  of user root.
Jun  :: localhost systemd: Starting Session  of user root.
Jun  :: localhost sshd[]: Failed password for root from 123.59.209.10 port  ssh2
Jun  :: localhost systemd: Started Session  of user root.
Jun  :: localhost systemd: Starting Session  of user root.
Jun  :: localhost sshd[]: Received disconnect from 123.59.209.10 port :: Normal Shutdown, Thank you for playing [preauth]
Jun  :: localhost sshd[]: Disconnected from 123.59.209.10 port  [preauth]
Jun  :: localhost systemd: Started Session  of user root.
Jun  :: localhost systemd: Starting Session  of user root.

前面并没有这么多凭空的session产生，现在为什么这么多？

线索：https://www.depesz.com/2010/12/13/a-tale-of-slow-ssh-connections/

https://major.io/2015/07/27/very-slow-ssh-logins-on-fedora-22/

https://serverfault.com/questions/707377/slow-ssh-login-activation-of-org-freedesktop-login1-timed-out#

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=793814