ElastAlert监控日志告警Web攻击行为---tomcat和nginx日志json格式

一、ELK安装

1.2 elk配置

logstash自定义配置文件，取名为filebeat_log.conf ：

input {
  beats {
    port => 5044
    client_inactivity_timeout => 90
    codec => json
  }

}

filter {
  date {
    match => [ "timestamp", "dd/MMM/yyyy:HH:mm:ss Z" ]
    target => ["datetime"]
  }
  geoip {
    source => "remote_addr"
  }

  mutate {
    remove_field => ["tags", "beat"]
  }
}

output {
  stdout {
   codec => rubydebug
  }

  elasticsearch {
    hosts => "localhost:9200"
    index => "logstash-%{+YYYY.MM.dd}"
  }
}

1.3 启动方法

logstash启动

进入/usr/share/logstash/bin：

nohup ./logstash -f filebeat_log.conf> /dev/null 2>&1 &

二、使用filebeat进行分布式收集

下面以tomcat为例子，分享我的配置文件filebeat.yml（nginx的话，修改paths的路径）：

filebeat.prospectors:
- type: log
  enabled: true
  paths:
    - /home/qy/apache-tomcat-9.0.1/logs/localhost_access_log.*.txt
  document_type: tomcat-log
  scan_frequency: 15s
  ignore_older: 20m
  close_inactive: 12m
  clean_inactive: 30m
  close_removed: true
  clean_removed: true
  ....
  #----------------------------- Logstash output --------------------------------

output.logstash:
  hosts: ["188.88.88.88:5044"]

直接解压下载的tar包，进入目录修改配置文件。然后启动filebeat：nohup ./filebeat -e -c filebeat.yml >/dev/null 2>&1 &

三、日志格式转json

为方便kibana分析和elastalert的取值，日志的格式要为json格式，上述的logstash配置文件已适配json格式。

公司的应用服务器中均为nginx和tomcat，故本文只介绍tomcat及nginx的json格式配置方法，其他服务器配置方法请自行搜索。

3.1 tomcat的json格式配置

打开config/server.xml,在最后的位置修改log的输出配置为：

<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="{&quot;time&quot;:&quot;%t&quot;,&quot;remote_addr&quot;:&quot;%h&quot;,&quot;remote_user&quot;:&quot;%l&quot;,&quot;request&quot;:&quot;%r&quot;,&quot;status&quot;:&quot;%s&quot;,&quot;body_bytes_sent&quot;:&quot;%b&quot;,&quot;http_referer&quot;:&quot;%{Referer}i&quot;,&quot;http_user_agent&quot;:&quot;%{User-Agent}i&quot;,&quot;http_x_forwarded_for&quot;:&quot; %{X-Forwarded-For}i&quot;,&quot;request_time&quot;:&quot;%T&quot;,&quot;host&quot;:&quot;%v&quot;,&quot;port&quot;:&quot;%p&quot;}"/>

然后重启tomcat，即生效。

3.2 nginx的json格式配置

进入`/etc/nginx`打开`nginx.conf`，加入如下配置：
http {

    ##
    # Basic Settings
    ##

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    # server_tokens off;

     log_format logstash_json '{"time": "$time_local", '
        '"remote_addr": "$remote_addr", '
        '"remote_user": "$remote_user", '
        '"request": "$request", '
        '"status": "$status", '
        '"body_bytes_sent": "$body_bytes_sent", '
        '"http_referer": "$http_referer", '
        '"http_user_agent": "$http_user_agent", '
        '"http_x_forwarded_for": "$http_x_forwarded_for", '
        '"request_time": "$request_time", '
        '"request_length": "$request_length", '
        '"host": "$http_host"}';
}

最后nginx -s reload即可

四、使用elastalert进行告警

ElastAlert使用python编写，具有容易上手、文档全等特点，虽然这个工具拥有如此多的优点，在搭建过程还是遇到了很多很多的未知错误，主要原因是网上的资料大多是针对es5.x以前的版本而没什么现成的资料可供参考。

4.1 安装elastalert

  git clone https://github.com/Yelp/elastalert.git 
  cd elastalert
  python setup.py install            //可能需要sudo
  Pip install -r requirements.txt    //可能需要sudo
  cp config.yaml.example config.yaml

具体的功能本文就不一一介绍了，请自行前往官方文档了解

4.2 创建索引

安装完成后会系统中会自带三个命令：

elastalert-create-index、elastalert-rule-from-kibana 、elastalert-test-rule

使用elastalert-create-index，根据提示设置es后按回车默认即可。
​ 配置完索引及配置文件后，可以使用elastalert-test-rule进行测试。这里有个bug，如果出现TransportError(400, u'search_phase_execution_exception', u'No mapping found for [alert_time] in order to sort on')之类的错误，在确认没有其他的问题时，可以先删除索引curl -XDELETE http://localhost:9200/*,再使用elastalert-create-index重新生成索引。

4.3 配置config.yaml

  rules_folder: example_rules

  # How often ElastAlert will query Elasticsearch
  # The unit can be anything from weeks to seconds
  run_every:
    seconds: 3   #每三秒向es请求数据
  # ElastAlert will buffer results from the most recent
  # period of time, in case some log sources are not in real time
  buffer_time:
    minutes: 15  
    #日志会延迟进入es，这里是配置query的向前的时间范围，这是15分钟，即查询 time[now-15m, now]

  # The Elasticsearch hostname for metadata writeback
  # Note that every rule can have its own Elasticsearch host
  es_host: 188.88.88.88

  # The Elasticsearch port
  es_port: 9200

  # Optional URL prefix for Elasticsearch
  #es_url_prefix: elasticsearch

  # Connect with TLS to Elasticsearch
  #use_ssl: True

  # Verify TLS certificates
  #verify_certs: True

  # GET request with body is the default option for Elasticsearch.
  # If it fails for some reason, you can pass 'GET', 'POST' or 'source'.
  # See http://elasticsearch-py.readthedocs.io/en/master/connection.html?highlight=send_get_body_as#transport
  # for details
  #es_send_get_body_as: GET

  # Option basic-auth username and password for Elasticsearch
  #es_username: someusername
  #es_password: somepassword

  # The index on es_host which is used for metadata storage
  # This can be a unmapped index, but it is recommended that you run
  # elastalert-create-index to set a mapping
  writeback_index: elastalert_status

  # If an alert fails for some reason, ElastAlert will retry
  # sending the alert until this time period has elapsed
  alert_time_limit:
    days: 1

以上各字段的解释：

Rules_folder：用来加载下一阶段rule的设置，默认是example_rules

Run_every：用来设置定时向elasticsearch发送请求

Buffer_time：用来设置请求里时间字段的范围，默认是45分钟

Es_host：elasticsearch的host地址

Es_port：elasticsearch 对应的端口号

Use_ssl：可选的，选择是否用SSL连接es，true或者false

Verify_certs：可选的，是否验证TLS证书，设置为true或者false，默认为- true

Es_username：es认证的username

Es_password：es认证的password

Es_url_prefix：可选的，es的url前缀（我的理解是https或者http）

Es_send_get_body_as：可选的，查询es的方式，默认的是GET

Writeback_index：elastalert产生的日志在elasticsearch中的创建的索引

Alert_time_limit：失败重试的时间限制

4.4 告警配置介绍

在example_rules目录中新建yaml配置文件 webattack_frequency.yaml,下面分开介绍这个配置文件的内容（下个小节将分享我的配置文件，此小节仅解释其中的必要设置项）：

1、告警规则

ElastAlert支持11种告警规则，本文不一一介绍了，为响应web攻击行为，本文选用的告警规则是frequency。

name: web attack

# (Required)
# Type of alert.
# the frequency rule type alerts when num_events events occur with timeframe time
type: frequency

# (Required, frequency specific)
# Alert when this many documents matching the query occur within a timeframe
num_events: 10

# (Required, frequency specific)
# num_events must occur within this amount of time to trigger an alert
timeframe:
  minutes: 1
  
# (Required)
# Index to search, wildcard supported
index: logstash-*      #对应logstash的配置文件中output的elasticsearch index前缀

filter:
- query_string:
# sql insert  xss detect
        query: "request: select.+(from|limit) OR request: union(.*?)select OR request: into.+(dump|out)file "

上述配置文件的意图即是：在一分钟内将匹配query里面的sql注入规则，若匹配次数达到10次，即进行报警。

2、使用邮箱进行告警

ElastAlert提供了 10 多种通知的类型，本文选用的是邮箱告警，还有微信告警、钉钉告警，若有需要，请自行配置。

smtp_host: smtp.qiye.163.com
smtp_port: 25

smtp_auth_file: /Users/qy/Downloads/work/elastalert/example_rules/smtp_auth_file.yaml
#回复给那个邮箱
email_reply_to: xxx@163.com
#从哪个邮箱发送
from_addr: xxx@163.com



# (Required)
# The alert is use when a match is found
alert:
- "email"

# (required, email specific)
# a list of email addresses to send alerts to
email:
- "shystartree@163.com"

alert_subject: "web attack may be by {} at @{}"
alert_subject_args:
  - remote_addr
  - time

alert_text_type: alert_text_only

alert_text: |
  你好，服务器({})可能正在受到web攻击，请采取手段阻止！！！！
  ### 截止发邮件前匹配到的请求数：{}
  > 发生时间: {}
  > timestamp:{}
  > attacker's ip: {}
  > request: {}
  > status:{}
  > UA头:{}
  >>> 参考来源：{}

alert_text_args:
  - host
  - num_hits
  - time
  - "@timestamp"
  - remote_addr
  - request
  - status
  - http_user_agent
  - source

smtp_auth_file.yaml的配置内容会在下个小节给出，在这个配置中，我自定义了 alert 的内容，更为精确地突出了攻击者ip、受攻击的服务器、攻击事件等信息。

3、减少重复告警的频率

在实际的使用中，若使用上述的配置，受到攻击的时候邮箱将不断地收到邮件，而这些邮件都对应着同一个攻击实例，根本没必要重复收取，于是，我使用了如下的配置：

   # 用来区分报警，跟 realert 配合使用，在这里意味着，
   # 5 分钟内如果有重复报警，那么当 name 不同时，会当做不同的报警处理，可以是数组
   query_key:
     - name

   # 5 分钟内相同的报警不会重复发送
   realert:
     minutes: 5

   # 指数级扩大 realert 时间，中间如果有报警，
   # 则按照 5 -> 10 -> 20 -> 40 -> 60 不断增大报警时间到制定的最大时间，
   # 如果之后报警减少，则会慢慢恢复原始 realert 时间
   exponential_realert:
     hours: 1

在本人实际测试的攻击场景中，发现使用了exponential_realert后，会错过很多告警（这些告警并不是同一个攻击实例），暂时不确定原因，还请读者们自行确定是否开启该设置。

4.5webattack_frequency.yaml及smtp_auth_file.yaml配置文件内容

上述的4.4小节中对每个配置都作了简单的介绍，这里就直接放出web攻击预警的配置文件供各位读者参考。

webattack_frequency.yaml:
# Alert when the rate of events exceeds a threshold

# (Optional)
# Elasticsearch host
#es_host: 188.88.88.88

# (Optional)
# Elasticsearch port
#es_port: 9200

# (OptionaL) Connect with SSL to Elasticsearch
#use_ssl: True

# (Optional) basic-auth username and password for Elasticsearch
#es_username: someusername
#es_password: somepassword

# (Required)
# Rule name, must be unique
name: web attack

realert:
  minutes: 5

# (Required)
# Type of alert.
# the frequency rule type alerts when num_events events occur with timeframe time
type: frequency

# (Required)
# Index to search, wildcard supported
index: logstash-*

# (Required, frequency specific)
# Alert when this many documents matching the query occur within a timeframe
num_events: 10

# (Required, frequency specific)
# num_events must occur within this amount of time to trigger an alert
timeframe:
  #hours: 4
  minutes: 1

# (Required)
# A list of Elasticsearch filters used for find events
# These filters are joined with AND and nested in a filtered query
# For more info: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl.html
#filter:
#- term:
#    some_field: "some_value"

filter:
- query_string:
# sql insert  xss detect
        query: "request: select.+(from|limit) OR request: union(.*?)select OR request: into.+(dump|out)file OR

        request: (base64_decode|sleep|benchmark|and.+1=1|and.+1=2|or%20|exec|information_schema|where%20|union%20|%2ctable_name%20|cmdshell|table_schema) OR

        request: (iframe|script|body|img|layer|div|meta|style|base|object|input|onmouseover|onerror|onload) OR

        request: .+etc.+passwd OR http_user_agent：(HTTrack|harvest|audit|dirbuster|pangolin|nmap|sqln|-scan|hydra|Parser|libwww|BBBike|sqlmap|w3af|owasp|Nikto|fimap|havij|PycURL|zmeu|BabyKrokodil|netsparker|httperf|bench) OR

        status: (400|404|500|501)

        NOT (request:_health.html OR remote_addr:222.222.222.222  )
        "


smtp_host: smtp.qiye.163.com
smtp_port: 25

smtp_auth_file: /Users/qy/Downloads/work/elastalert/example_rules/smtp_auth_file.yaml
#回复给那个邮箱
email_reply_to: xxx@163.com
#从哪个邮箱发送
from_addr: xxx@163.com



# (Required)
# The alert is use when a match is found
alert:
- "email"

# (required, email specific)
# a list of email addresses to send alerts to
email:
- "shystartree@163.com"

alert_subject: "web attack may be by {} at @{}"
alert_subject_args:
  - remote_addr
  - time

alert_text_type: alert_text_only

alert_text: |
  你好，服务器({})可能正在受到web攻击，请采取手段阻止！！！！
  ### 截止发邮件前匹配到的请求数：{}
  > 发生时间: {}
  > timestamp:{}
  > attacker's ip: {}
  > request: {}
  > status:{}
  > UA头:{}
  >>> 参考来源：{}

alert_text_args:
  - host
  - num_hits
  - time
  - "@timestamp"
  - remote_addr
  - request
  - status
  - http_user_agent
  - source
smtp_auth_file.yaml:
user: xxx@163.com
password: password

4.6 运行elastalert

在成功配置完ElastAlert后将生成三个配置文件：

config.yaml、webattack_frequency.yaml、smtp_auth_file.yaml

• 启动elastalert服务，监听elasticsearch：

nohup python -m elastalert.elastalert --verbose --rule webattack_frequency.yaml >/dev/null 2>&1 &

• 为实现守护进程的作用，可以配合supervisor进行使用，本文不再阐述。

4.7 运行效果：

当匹配到自定义攻击规则的时候，ElastAlert将会以邮件方式发送告警信息：

web attack may be by 104.38.13.21 at @[13/Jan/2018:16:06:58 +0800]
xxx 发给 shystartree   
你好，服务器(199.222.36.31)可能正在受到web攻击，请采取手段阻止！！！！
### 截止发邮件前匹配到的请求数：20
> 发生时间: [13/Jan/2018:16:06:58 +0800]
> timestamp:2018-01-13T08:07:04.930Z
> attacker's ip: 184.233.9.121
> request: GET /dbadmin/scripts/setup.php HTTP/1.0
> status:200
> UA头:ZmEu
>>> 参考来源：/log/localhost_access_log.2018-01-13.txt