ELK --- Grok正则过滤Linux系统登录日志

过滤Linux系统登录日志/var/log/secure

登陆成功

Jan  6 17:11:47 localhost sshd[3324]: Received disconnect from 172.16.0.13: 11: disconnected by user
Jan  6 17:11:47 localhost sshd[3324]: pam_unix(sshd:session): session closed for user root
Jan  6 17:11:48 localhost sshd[3358]: Address 172.16.0.13 maps to localhost, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Jan  6 17:11:51 localhost sshd[3358]: Accepted password for root from 172.16.0.13 port 38604 ssh2
Jan  6 17:11:51 localhost sshd[3358]: pam_unix(sshd:session): session opened for user root by (uid=0)

登陆失败

Jan  6 17:13:10 localhost sshd[3380]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=172.16.0.39  user=root
Jan  6 17:13:12 localhost sshd[3380]: Failed password for root from 172.16.0.39 port 58481 ssh2

以上信息中我们只用判断登录成功或失败

Jan  6 17:11:51 localhost sshd[3358]: Accepted password for root from 172.16.0.13 port 38604 ssh2
或者
Jan  6 17:13:12 localhost sshd[3380]: Failed password for root from 172.16.0.39 port 58481 ssh2
--------------------- 

logstash配置

input {
    file {
        path => "/var/log/secure"
    }
}

filter {
    grok {
        match => {
            "message" => ".* sshd\[\d+\]: (?\S+) .* (?(?:\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})?) .*"
        }
        overwrite => ["message"]
    }
}

output {
    if [ClientIP] =~ /\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/ and ([status] == "Accepted" or [status] == "Failed") {
        elasticsearch {
            hosts => "172.16.11.199"
            index => "logstash-%{+YYYY.MM.dd}"
        }
    }
}

配置解释：

• input插件使用file读取日志文件

• filter插件使用grok来匹配相应的日志行

  1. message中定义了两个Fields，分别匹配登录来源IP，和登录状态
  2. overwrite表示重写message行
• output插件指定将过滤出来的信息输出到哪个地方，这里输出到elasticsearch
  1. 一个条件判断，判断filter中定义的两个fields是否匹配，如果匹配则输出到elasticsearch中，如果不匹配则不操作

正则解释

Jan  6 17:11:51 localhost sshd[3358]: Accepted password for root from 172.16.0.13 port 38604 ssh2

• .*匹配Jan 6 17:11:51 localhost
• sshd[\d+]: 匹配sshd[3358]: 段，\d+匹配多个数字

• (?\S+)：
  1.(?正则表达式)：定义一个xxx字段匹配后面正则表达式，类似{xxx:匹配的结果}，在上面output中的条件判断即可使用该字段来使用匹配到的结果
  2.\S+表示多个字符串，也就是匹配Accepted或Failed

• (?(?:\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3})?)
  1.先定义一个ClientIP字段
  2.(?:...)? 表示匹配一个ip但不保存供以后引用，如果(...)则以后可以使用$1来调用匹配到的值，最后一个?表示非贪婪匹配，尽可能少的匹配

最终输出结果：

{
       "message" => "Mar 22 10:16:51 k8s-n2 sshd[27997]: Failed password for root from 10.201.1.10 port 39302 ssh2",
      "@version" => "1",
    "@timestamp" => "2019-03-22T02:16:51.813Z",
          "path" => "/var/log/secure",
          "host" => "k8s-n2",
        "status" => "Failed",
      "ClientIP" => "10.201.1.10"
}