ModSecurity Core Rule Set Docker Image

What is the Core Rule Set

The Core Rule Set (CRS) is a set of generic attack detection rules for use with ModSecurity or compatible web application firewalls. ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx.

Building

Image building requires make, or you can do the same by calling the src/release.sh helper with the version release you want and the web server, e.g:

$ ./src/release.sh "v3.3.0-apache"
$ docker build --tag owasp/modsecurity-crs:v3.3.0-apache -f v3.3.0-apache/Dockerfile .

If you call make without arguments, will build all releases and web server combinations.

Or use make VERSIONS=v3.3.0-rc1 and it will get the proper release and build the container.

You can also add your local tag, or override the build:

make VERSIONS=v3.3.0 SERVERS=nginx TAG=mytag

CRS Versions

Hey, I used some specific git version with the containers? What happened?

You can achieve the same results just by getting any version you want, and using docker volumes. See this example:

$ git clone https://github.com/coreruleset/coreruleset.git myrules
$ cd myrules
$ git checkout ac2a0d1
$ docker run -p 80:80 -ti -e PARANOIA=4 -v ./rules:/opt/owasp-crs/rules:ro --rm owasp/modsecurity-crs

Apache

The Apache webserver is configured via the httpd-modsecurity.conf file overriding directives from the base file.

Environment Variables

The following environment variables are available to configure the CRS container:

Name	Description
PARANOIA	An integer indicating the paranoia level (Default: 1)
PROXY	An integer indicating if reverse proxy mode is enabled (Default: 0)
UPSTREAM	The IP Address (and optional port) of the upstream server when proxy mode is enabled. (Default: the container's default router, port 81) (Examples: 192.0.2.2 or 192.0.2.2:80)
EXECUTING_PARANOIA	An integer indicating the executing_paranoia_level (Default: paranoia level)
ENFORCE_BODYPROC_URLENCODED	A boolean indicating the enforce_bodyproc_urlencoded (Default: 0)
ANOMALY_INBOUND	An integer indicating the inbound_anomaly_score_threshold (Default: 5)
ANOMALY_OUTBOUND	An integer indicating the outbound_anomaly_score_threshold (Default: 4)
ALLOWED_METHODS	A string indicating the allowed_methods (Default: GET HEAD POST OPTIONS)
ALLOWED_REQUEST_CONTENT_TYPE	A string indicating the allowed_request_content_type (Default: application/x-www-form-urlencoded\|multipart/form-data\|text/xml\|application/xml\|application/soap+xml\|application/x-amf\|application/json\|application/octet-stream\|application/csp-report\|application/xss-auditor-report\|text/plain)
ALLOWED_REQUEST_CONTENT_TYPE_CHARSET	A string indicating the allowed_request_content_type_charset (Default: utf-8\|iso-8859-1\|iso-8859-15\|windows-1252)
ALLOWED_HTTP_VERSIONS	A string indicating the allowed_http_versions (Default: HTTP/1.0 HTTP/1.1 HTTP/2 HTTP/2.0)
RESTRICTED_EXTENSIONS	A string indicating the restricted_extensions (Default: .asa/ .asax/ .ascx/ .axd/ .backup/ .bak/ .bat/ .cdx/ .cer/ .cfg/ .cmd/ .com/ .config/ .conf/ .cs/ .csproj/ .csr/ .dat/ .db/ .dbf/ .dll/ .dos/ .htr/ .htw/ .ida/ .idc/ .idq/ .inc/ .ini/ .key/ .licx/ .lnk/ .log/ .mdb/ .old/ .pass/ .pdb/ .pol/ .printer/ .pwd/ .resources/ .resx/ .sql/ .sys/ .vb/ .vbs/ .vbproj/ .vsdisco/ .webinfo/ .xsd/ .xsx/)
RESTRICTED_HEADERS	A string indicating the restricted_headers (Default: /proxy/ /lock-token/ /content-range/ /if/)
STATIC_EXTENSIONS	A string indicating the static_extensions (Default: /.jpg/ /.jpeg/ /.png/ /.gif/ /.js/ /.css/ /.ico/ /.svg/ /.webp/)
MAX_NUM_ARGS	An integer indicating the max_num_args (Default: unlimited)
ARG_NAME_LENGTH	An integer indicating the arg_name_length (Default: unlimited)
ARG_LENGTH	An integer indicating the arg_length (Default: unlimited)
TOTAL_ARG_LENGTH	An integer indicating the total_arg_length (Default: unlimited)
MAX_FILE_SIZE	An integer indicating the max_file_size (Default: unlimited)
COMBINED_FILE_SIZES	An integer indicating the combined_file_sizes (Default: unlimited)
APACHE_TIMEOUT	Apache integer value indicating the number of seconds before receiving and sending time out (Default: 60)
NGINX_KEEPALIVE_TIMEOUT	Nginx integer value indicating the number of seconds a keep-alive client connection will stay open on the server side (Default: 60)
LOGLEVEL	A string value controlling the number of messages logged to the error_log (Default: warn)
ERRORLOG	A string value indicating the location of the error log file (Default: '/proc/self/fd/2')
PORT	An integer value indicating the port where the webserver is listening to (Default: 80)
USER	A string value indicating the name (or #number) of the user to run httpd as (Default: daemon)
GROUP	Apache string value indicating the name (or #number) of the group to run httpd as (Default: daemon)
SERVERADMIN	A string value indicating the address where problems with the server should be e-mailed (Default: root@localhost)
SERVERNAME	A string value indicating the server name (Default: localhost)
MODSEC_RULE_ENGINE	ModSecurity string value enabling ModSecurity itself (Default: on)
MODSEC_REQ_BODY_ACCESS	ModSecurity string value allowing ModSecurity to access request bodies (Default: on)
MODSEC_REQ_BODY_LIMIT	ModSecurity integer value indicating the maximum request body size accepted for buffering (Default: 13107200)
MODSEC_RESP_BODY_ACCESS	ModSecurity string value allowing ModSecurity to access response bodies (Default: on)
MODSEC_RESP_BODY_LIMIT	ModSecurity integer value indicating the maximum response body size accepted for buffering (Default: 524288)
MODSEC_PCRE_MATCH_LIMIT	ModSecurity integer value indicating the limit for the number of internal executions in the PCRE function (Default: 1000)
MODSEC_PCRE_MATCH_LIMIT_RECURSION	ModSecurity integer value indicating the limit for the depth of recursion when calling PCRE function (Default: 1000)

Notes regarding reverse proxy

In order to more easily test drive the CRS ruleset, we include support for an technique called Reverse Proxy. Using this technique, you keep your pre-existing web server online at a non-standard host and port, and then configure the CRS container to accept public traffic. The CRS container then proxies the traffic to your pre-existing webserver. This way, you can test out CRS with any web server. Some notes:

Proxy is not enabled by default. You'll need to pass the -e PROXY=1 environment variable to enable it.
You'll want to configure your typical webserver to listen on your docker interface only (i.e. 172.17.0.1:81) so that public traffic doesn't reach it.
Do not use 127.0.0.1 as an UPSTREAM address. The loopback interface inside the docker container is not the same interface as the one on docker host.
Note that traffic coming through this proxy will look like it's coming from the wrong address. You may want to configure your pre-existing webserver to use the X-Forwarded-For HTTP header to populate the remote address field for traffic from the proxy.

ModSecurity CRS Tuning

There are two possible ways to pass ModSecurity CRS tuning rules to the container:

To map the ModSecurity tuning file(s) via volumes into the container during the run command
To copy the ModSecurity tuning file(s) into the created container and then start the container

Map ModSecurity tuning file via volume

docker run -dti --rm \
   -p 80:80 \
   -v /path/to/REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf:/etc/modsecurity.d/owasp-crs/rules/REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf \
   -v /path/to/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf:/etc/modsecurity.d/owasp-crs/rules/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf \
   owasp/modsecurity-crs

Copy ModSecurity tuning file into created container

This example can be helpful when no volume mounts are possible (some CI pipelines).

docker create -ti --name modseccrs \
   -p 80:80 \
   owasp/modsecurity-crs

docker cp /path/to/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf \
   modseccrs:/etc/modsecurity.d/owasp-crs/rules/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf

docker start modseccrs

Full docker run example with all possible environment variables

docker run -dti 80:80 --rm \
   -e PARANOIA=1 \
   -e EXECUTING_PARANOIA=2 \
   -e ENFORCE_BODYPROC_URLENCODED=1 \
   -e ANOMALY_INBOUND=10 \
   -e ANOMALY_OUTBOUND=5 \
   -e ALLOWED_METHODS="GET POST PUT" \
   -e ALLOWED_REQUEST_CONTENT_TYPE="text/xml|application/xml|text/plain" \
   -e ALLOWED_REQUEST_CONTENT_TYPE_CHARSET="utf-8|iso-8859-1" \
   -e ALLOWED_HTTP_VERSIONS="HTTP/1.1 HTTP/2 HTTP/2.0" \
   -e RESTRICTED_EXTENSIONS=".cmd/ .com/ .config/ .dll/" \
   -e RESTRICTED_HEADERS="/proxy/ /if/" \
   -e STATIC_EXTENSIONS="/.jpg/ /.jpeg/ /.png/ /.gif/" \
   -e MAX_NUM_ARGS=128 \
   -e ARG_NAME_LENGTH=50 \
   -e ARG_LENGTH=200 \
   -e TOTAL_ARG_LENGTH=6400 \
   -e MAX_FILE_SIZE=100000 \
   -e COMBINED_FILE_SIZES=1000000 \
   -e PROXY=1 \
   -e APACHE_TIMEOUT=60 \
   -e LOGLEVEL=warn \
   -e ERRORLOG='/proc/self/fd/2' \
   -e USER=daemon \
   -e GROUP=daemon \
   -e SERVERADMIN=root@localhost \
   -e SERVERNAME=localhost \
   -e PORT=80 \
   -e MODSEC_RULE_ENGINE=on \
   -e MODSEC_REQ_BODY_ACCESS=on \
   -e MODSEC_REQ_BODY_LIMIT=13107200 \
   -e MODSEC_REQ_BODY_NOFILES_LIMIT=131072 \
   -e MODSEC_RESP_BODY_ACCESS=on \
   -e MODSEC_RESP_BODY_LIMIT=524288 \
   -e MODSEC_PCRE_MATCH_LIMIT=1000 \
   -e MODSEC_PCRE_MATCH_LIMIT_RECURSION=1000
   owasp/modsecurity-crs

timwsuqld/modsecurity-crs-docker