Randomly, the modsecurity blocks legitimate clients requests giving the error 403. Here is para of the modsec_audit.log:
---d6e99f36-A--
[21/Jun/2020:07:14:45 +0100] Xu761X8AAAEAADI1YrAAAABQ xxx.xxx.xxx.xxx 60036 xxx.xxx.xxx.xxx 443
--d6e99f36-B--
GET /s/p.json?eyJ0IjoyLjksImYiOnsiZmxpX3BsIjoiYXNwZXJzb3IiLCJmbGlfZyI6LTEsImZsaV9jIjotMSwiZmxpX20iOjAsImZsaV9hIjoyMDE1fSwiY3NyZiI6ImE5MDMwMDkxLTBlZjg$
Host: fneon.eu
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:77.0) Gecko/20100101 Firefox/77.0
Accept: */*
Accept-Language: pt-PT,pt;q=0.8,en;q=0.5,en-US;q=0.3
Accept-Encoding: gzip, deflate, br
Referer: https://example.com/
Content-Type: application/json,charset=UTF-8
DNT: 1
Connection: keep-alive
Cookie: jwt=eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIyYzMwOGQwYTc5NGEyZWU2MjMxYzI2M2EyYWMzNjkwMCIsImV4cCI6MTU5MzY0NDQwMCwiaWF0IjoxNTkyNzE5ODg1$
Pragma: no-cache
Cache-Control: no-cache
--d6e99f36-F--
HTTP/1.1 403 Forbidden
X-FRAME-OPTIONS: DENY
X-Content-Type-Options: nosniff
Content-Length: 199
Keep-Alive: timeout=5, max=89
Connection: Keep-Alive
Content-Type: text/html; charset=iso-8859-1
--d6e99f36-E--
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>403 Forbidden</title>
</head><body>
<h1>Forbidden</h1>
<p>You don't have permission to access this resource.</p>
</body></html>
--d6e99f36-H--
Apache-Error: [file "mod_evasive20.c"] [line 259] [level 3] client denied by server configuration: %s
Apache-Handler: proxy-server
Stopwatch: 1592720085355364 815 (- - -)
Stopwatch2: 1592720085355364 815; combined=42, p1=35, p2=0, p3=1, p4=0, p5=5, sr=0, sw=1, l=0, gc=0
Response-Body-Transformed: Dechunked
Producer: ModSecurity for Apache/2.9.0 (http://www.modsecurity.org/).
Server: Apache
Engine-Mode: "ENABLED"
--d6e99f36-Z--
Here is my configuration (only the changes):
/etc/modsecurity/modsecurity.conf
SecRuleEngine On
SecResponseBodyAccess Off
SecRequestBodyLimit 5242880 (15Mb)
/etc/apache2/mods-enabled/evasive.conf
<IfModule mod_evasive20.c>
DOSHashTableSize 3097
DOSPageCount 10
DOSSiteCount 75
DOSPageInterval 5
DOSSiteInterval 1
DOSBlockingPeriod 3000
DOSWhitelist 127.0.0.1
DOSWhitelist xxx.xxx.xxx.xxx
DOSWhitelist xxx.xxx.xxx.xxx
DOSWhitelist xxx.xxx.xxx.xxx
DOSLogDir "/var/log/mod_evasive"
</IfModule>
/etc/apache2/conf-enabled/security.conf
ServerTokens Prod
One way to reproduce the problem is when the client makes this type of request:
https://example.com/s/p.json?eyJ0IjoyLjksImYiOnsiZmxpX3BsIjoiYXNwZXJzb3IiLCJmbGlfZyI6LTEsImZsaV9jIjotMSwiZmxpX20iOjAsImZsaV9hIjoyMDExfSwiY3NyZiI6ImE5MDMwMDkxLTBlZjgtNDcyOC05YjQ1LTU1MWY3M2U5YjQ5MCJ9
...which in my case is a legitimate request. Can anyone tell me how to solve this problem? Thank you.