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="{"time":"%t","remote_addr":"%h","remote_user":"%l","request":"%r","status":"%s","body_bytes_sent":"%b","http_referer":"%{Referer}i","http_user_agent":"%{User-Agent}i","http_x_forwarded_for":" %{X-Forwarded-For}i","request_time":"%T","host":"%v","port":"%p"}"/>
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
