high performance WAF platform with Naxsi and HAProxy
http://blog.exceliance.fr/2012/10/16/high-performance-waf-platform-with-naxsi-and-haproxy/Synopsis
I’ve already described WAF in a previous article, where I spoke about
WAF scalability with apache and modsecurity.
One of the main issue with Apache and modsecurity is the performance. To address this issue, an alternative exists:naxsi, a Web Application Firewall
module fornginx.
So using Naxsi and HAProxy as a load-balancer, we’re able to build a platform which meets the following requirements:
[*]Web Application Firewall: achieved by Apache andmodsecurity
[*]High-availability: application server and WAF monitoring, achieved byHAProxy
[*]Scalability: ability to adapt capacity to the upcoming volume of traffic, achieved byHAProxy
[*]DDOS protection: blind and brutal attacks protection, slowloris protection, achieved byHAProxy
[*]Content-Switching: ability to route only dynamic requests to the WAF, achieved byHAProxy
[*]Reliability: ability to detect capacity overusage, this is achieved byHAProxy
[*]Performance: deliver response as fast as possible, achieved by the whole platform
The picture below provides a better overview:
The LAB platform is composed by 6 boxes:
[*]2 ALOHA Load-Balancers (could be replaced by HAProxy 1.5-dev)
[*]2 WAF servers: CentOS 6.0, nginx and Naxsi
[*]2 Web servers: Debian + apache + PHP + dokuwiki
Nginx and Naxsi installation on CentOS 6
Purpose of this article is not to provide such procedue. So please read this wiki article which summarizeshow to install nginx
and naxsi on CentOS 6.0.
Diagram
The diagram below shows the platform with HAProxy frontends (prefixed byft_) and backends (prefixed by
bk_). Each farm is composed by 2 servers.
Configuration
Nginx and Naxsi
Configure nginx as a reverse-proxy which listen in bk_waf and forward traffic to ft_web. In the mean time,naxsi is there to analyze the requests.
01
server {
02
proxy_set_header Proxy-Connection "";
03
listen 192.168.10.15:81;
04
access_log/var/log/nginx/naxsi_access.log;
05
error_log/var/log/nginx/naxsi_error.log debug;
06
07
location / {
08
include /etc/nginx/test.rules;
09
proxy_pass
http://192.168.10.2:81/;
10
}
11
12
error_page 403 /403.html;
13
location = /403.html {
14
root /opt/nginx/html;
15
internal;
16
}
17
18
location /RequestDenied {
19
return 403;
20
}
21
}
HAProxy Load-Balancer configuration
The configuration below allows the following advanced features:
[*]DDOS protection on the frontend
[*]abuser or attacker detection in bk_waf and blocking on the public interface (ft_waf)
[*]Bypassing WAF when overusage or unavailable
001
######## Default values for all entries till next defaults section
002
defaults
003
optionhttp-server-close
004
optiondontlognull
005
optionredispatch
006
optioncontstats
007
retries 3
008
timeout connect 5s
009
timeout http-keep-alive 1s
010
# Slowloris protection
011
timeout http-request 15s
012
timeout queue 30s
013
timeout tarpit 1m # tarpit hold tim
014
backlog 10000
015
016
# public frontend where users get connected to
017
frontend ft_waf
018
bind 192.168.10.2:80 name http
019
mode http
020
log global
021
option httplog
022
timeout client 25s
023
maxconn 10000
024
025
# DDOS protection
026
# Use General Purpose Couter (gpc) 0 in SC1 as a global abuse counter
027
# Monitors the number of request sent by an IP over a period of 10 seconds
028
stick-table type ip size 1m expire 1m store gpc0,http_req_rate(10s),http_err_rate(10s)
029
tcp-request connection track-sc1 src
030
tcp-request connection reject if { sc1_get_gpc0 gt 0 }
031
# Abuser means more than 100reqs/10s
032
acl abuse sc1_http_req_rate(ft_web) ge 100
033
acl flag_abuser sc1_inc_gpc0(ft_web)
034
tcp-request content reject if abuse flag_abuser
035
036
acl static path_beg /static/ /dokuwiki/images/
037
acl no_waf nbsrv(bk_waf) eq 0
038
acl waf_max_capacity queue(bk_waf) ge 1
039
# bypass WAF farm if no WAF available
040
use_backend bk_web if no_waf
041
# bypass WAF farm if it reaches its capacity
042
use_backend bk_web if static waf_max_capacity
043
default_backend bk_waf
044
045
# WAF farm where users' traffic is routed first
046
backend bk_waf
047
balance roundrobin
048
mode http
049
log global
050
option httplog
051
option forwardfor header X-Client-IP
052
option httpchk HEAD /waf_health_check HTTP/1.0
053
054
# If the source IP generated 10 or more http request over the defined period,
055
# flag the IP as abuser on the frontend
056
acl abuse sc1_http_err_rate(ft_waf) ge 10
057
acl flag_abuser sc1_inc_gpc0(ft_waf)
058
tcp-request content reject if abuse flag_abuser
059
060
# Specific WAF checking: a DENY means everything is OK
061
http-check expect status 403
062
timeout server 25s
063
default-server inter 3s rise 2 fall 3
064
server waf1 192.168.10.15:81 maxconn 100 weight 10 check
065
server waf2 192.168.10.16:81 maxconn 100 weight 10 check
066
067
# Traffic secured by the WAF arrives here
068
frontend ft_web
069
bind 192.168.10.2:81 name http
070
mode http
071
log global
072
option httplog
073
timeout client 25s
074
maxconn 1000
075
# route health check requests to a specific backend to avoid graph pollution in ALOHA GUI
076
use_backend bk_waf_health_check if { path /waf_health_check }
077
default_backend bk_web
078
079
# application server farm
080
backend bk_web
081
balance roundrobin
082
mode http
083
log global
084
option httplog
085
option forwardfor
086
cookie SERVERID insert indirect nocache
087
default-server inter 3s rise 2 fall 3
088
option httpchk HEAD /
089
# get connected on the application server using the user ip
090
# provided in the X-Client-IP header setup by ft_waf frontend
091
source 0.0.0.0 usesrc hdr_ip(X-Client-IP)
092
timeout server 25s
093
server server1 192.168.10.11:80 maxconn 100 weight 10 cookie server1 check
094
server server2 192.168.10.12:80 maxconn 100 weight 10 cookie server2 check
095
096
# backend dedicated to WAF checking (to avoid graph pollution)
097
backend bk_waf_health_check
098
balance roundrobin
099
mode http
100
log global
101
option httplog
102
option forwardfor
103
default-server inter 3s rise 2 fall 3
104
timeout server 25s
105
server server1 192.168.10.11:80 maxconn 100 weight 10 check
106
server server2 192.168.10.12:80 maxconn 100 weight 10 check
Detecting attacks
On the load-balancer
The ft_waf frontend stick table tracks two information:
http_req_rate and http_err_rate which are respectively thehttp request rate and the
http error rate generated by a single IP address.
HAProxy would automatically block an IP which has generated more than 100 requests over a period of 10s or 10 errors (WAF detection 403 responses included) in 10s. The user isblocked for 1 minute as long as he keeps on abusing.
Of course, you can setup above values to whatever you need: it is fully flexible. To know the status of IPs in your load-balancer, just run the command below:
echo show table ft_waf | socat /var/run/haproxy.stat -
# table: ft_waf, type: ip, size:1048576, used:1
0xc33304: key=192.168.10.254 use=0 exp=4555 gpc0=0 http_req_rate(10000)=1 http_err_rate(10000)=1
Note: The ALOHA Load-balancer does not provide watch tool, but you can monitor the content of the table in live with the command below:
while true ; do echo show table ft_waf | socat /var/run/haproxy.stat - ; sleep 2 ; clear ; done
On the Waf
Every Naxsi error log appears in /var/log/nginx/naxsi_error.log. IE:
2012/10/16 13:40:13 10556#0: *10293 NAXSI_FMT: ip=192.168.10.254&server=192.168.10.15&uri=/testphp.vulnweb.com/artists.php&total_processed=3195&total_blocked=2&zone0=ARGS&id0=1000&var_name0=artist, client: 192.168.10.254, server: , request: "GET /testphp.vulnweb.com/artists.php?artist=0+div+1+union%23foo*%2F*bar%0D%0Aselect%23foo%0D%0A1%2C2%2Ccurrent_user HTTP/1.1", host: "192.168.10.15:81"
Naxsi log line is less obvious than modsecurity one. The rule which matched os provided by the argumentidX=abcde.
No false positive during the test, I had to build a request to make Naxsi match it .
conclusion
Today, we saw it’s easy to build a scalable and performing WAF platform in front of any web application.
The WAF is able to communicate to HAProxy which IPs to automatically blacklist (throuth error rate monitoring), which is convenient since the attacker won’t bother the WAF for a certain amount of time
The platform allows to detect WAF farm availability and to bypass it in case of total failure, we even saw it is possible to bypass the WAF for static content if the farm is running out of capacity. Purpose is to deliver a good end-user experience without dropping
too much the security.
Note that it is possible to route all the static content to the web servers (or astatic farm) directly,
whatever the status of the WAF farm.
This make me say that the platform is fully scallable and flexible.
Thanks to HAProxy, the architecture is very flexible: I could switch my apache + modexurity to nginx + naxsi with no issues at all This could be done
as well for any third party waf appliances.
Note that I did not try any naxsi advanced features like learning mode and the UI as well.
Related links
[*]naxsi
[*]HTTP request flood mitigation
[*]Use a load-balancer as a first row of defense against DDOS
Links
[*]Exceliance
[*]Aloha load balancer: HAProxy based LB appliance
[*]HAPee: HAProxy Enterprise Edition
页:
[1]