Sizlere Layer 7 tarafında web sunucusu üzerinde bir nebze çözüm sunabilecek bir eklenti olan mod_security nasıl kurulacağını ve yapılandırılacağını anlatacağım. Bu makale’de yapacağınız işlemler sayesinde botların otomatik olarak gerçekleştirdiği taramaları engelleyebilir, saldırı yüzeyinizi daraltabilirsiniz.
Bu eklenti %100 güvenlik sağlamamakla birlikte bilinen atakların %70 kadarını engeller. L7’de tam güvenlik sağlamak istiyorsanız, kendi güvenlik kurallarınızı geliştirmeniz gerekir.
UYARI: Kullanılan bu eklenti web sitenizde ve/veya uygulamalarınızda istenmeyen hatalara sebep olabilir. Lütfen dikkatli kullanınız.
Nasıl Kurulur?
Debian’da uygulamayı derlemek ve ardından kurabilmek amacıyla öncelikli olarak gerekli bağımlılıkları kuralım.
apt install -y apt-utils autoconf automake build-essential git libcurl4-openssl-dev libgeoip-dev liblmdb-dev libpcre++-dev libtool libxml2-dev libyajl-dev pkgconf wget zlib1g-dev gitArdından remi git reposundan gerekli olan dosyaları indiriyoruz. Gerekli derleme işlemlerine başlıyoruz ve modülü ortaya çıkartıyoruz.
git clone --depth 1 -b v3/master --single-branch https://github.com/SpiderLabs/ModSecurity && cd ModSecurity
git submodule init
git submodule update
./build.sh
./configure
make
make installBu işlem yaklaşık olarak 15-30 dakika arasında sisteminizin özelliklerine göre süreceğini unutmayın, Beklemede kalın.
Ardından NGINX üzerinde modüle eklemesi yapılacak ve connector kurulumu gerçekleştirilecek.
git clone --depth 1 https://github.com/SpiderLabs/ModSecurity-nginx.git
wget https://nginx.org/download/nginx-1.19.1.tar.gz
tar zxvf nginx-1.19.1.tar.gz
cd nginx-1.19.1
./configure --with-compat --add-dynamic-module=../ModSecurity-nginx
make modules
cp objs/ngx_http_modsecurity_module.so /etc/nginx/modulesSıra geldi Connector Modülünü nginx kardeşimize eklemeye /etc/nginx/nginx.conf içerisine en üst satıra aşağıdakini ekleyin.
load_module modules/ngx_http_modsecurity_module.so;Ardından NGINX‘i yeniden başlatın, artık mod_security kullanıma hazır.
Mod Security Yapılandırma
Sisteme hali hazırda kurduğumuz, Mod Security için yapılandırmamızı yapmamız ve kuralları tanımlamamız gerekiyor. mkdir /etc/nginx/modsec komutunu verip klasörü oluşturun içerisine modsecurity.conf ekleyin.
SecRuleEngine On
SecRequestBodyAccess On
# Enable XML request body parser.
# Initiate XML Processor in case of xml content-type
#
SecRule REQUEST_HEADERS:Content-Type "(?:application(?:/soap\+|/)|text/)xml" \
"id:'200000',phase:1,t:none,t:lowercase,pass,nolog,ctl:requestBodyProcessor=XML"
# Enable JSON request body parser.
# Initiate JSON Processor in case of JSON content-type; change accordingly
# if your application does not use 'application/json'
#
SecRule REQUEST_HEADERS:Content-Type "application/json" \
"id:'200001',phase:1,t:none,t:lowercase,pass,nolog,ctl:requestBodyProcessor=JSON"
# Maximum request body size we will accept for buffering. If you support
# file uploads then the value given on the first line has to be as large
# as the largest file you are willing to accept. The second value refers
# to the size of data, with files excluded. You want to keep that value as
# low as practical.
#
SecRequestBodyLimit 13107200
SecRequestBodyNoFilesLimit 131072
# What to do if the request body size is above our configured limit.
# Keep in mind that this setting will automatically be set to ProcessPartial
# when SecRuleEngine is set to DetectionOnly mode in order to minimize
# disruptions when initially deploying ModSecurity.
#
SecRequestBodyLimitAction Reject
# Verify that we've correctly processed the request body.
# As a rule of thumb, when failing to process a request body
# you should reject the request (when deployed in blocking mode)
# or log a high-severity alert (when deployed in detection-only mode).
#
SecRule REQBODY_ERROR "!@eq 0" \
"id:'200002', phase:2,t:none,log,deny,status:400,msg:'Failed to parse request body.',logdata:'%{reqbody_error_msg}',severity:2"
# By default be strict with what we accept in the multipart/form-data
# request body. If the rule below proves to be too strict for your
# environment consider changing it to detection-only. You are encouraged
# _not_ to remove it altogether.
#
SecRule MULTIPART_STRICT_ERROR "!@eq 0" \
"id:'200003',phase:2,t:none,log,deny,status:400, \
msg:'Multipart request body failed strict validation: \
PE %{REQBODY_PROCESSOR_ERROR}, \
BQ %{MULTIPART_BOUNDARY_QUOTED}, \
BW %{MULTIPART_BOUNDARY_WHITESPACE}, \
DB %{MULTIPART_DATA_BEFORE}, \
DA %{MULTIPART_DATA_AFTER}, \
HF %{MULTIPART_HEADER_FOLDING}, \
LF %{MULTIPART_LF_LINE}, \
SM %{MULTIPART_MISSING_SEMICOLON}, \
IQ %{MULTIPART_INVALID_QUOTING}, \
IP %{MULTIPART_INVALID_PART}, \
IH %{MULTIPART_INVALID_HEADER_FOLDING}, \
FL %{MULTIPART_FILE_LIMIT_EXCEEDED}'"
# Did we see anything that might be a boundary?
#
# Here is a short description about the ModSecurity Multipart parser: the
# parser returns with value 0, if all "boundary-like" line matches with
# the boundary string which given in MIME header. In any other cases it returns
# with different value, eg. 1 or 2.
#
# The RFC 1341 descript the multipart content-type and its syntax must contains
# only three mandatory lines (above the content):
# * Content-Type: multipart/mixed; boundary=BOUNDARY_STRING
# * --BOUNDARY_STRING
# * --BOUNDARY_STRING--
#
# First line indicates, that this is a multipart content, second shows that
# here starts a part of the multipart content, third shows the end of content.
#
# If there are any other lines, which starts with "--", then it should be
# another boundary id - or not.
#
# After 3.0.3, there are two kinds of types of boundary errors: strict and permissive.
#
# If multipart content contains the three necessary lines with correct order, but
# there are one or more lines with "--", then parser returns with value 2 (non-zero).
#
# If some of the necessary lines (usually the start or end) misses, or the order
# is wrong, then parser returns with value 1 (also a non-zero).
#
# You can choose, which one is what you need. The example below contains the
# 'strict' mode, which means if there are any lines with start of "--", then
# ModSecurity blocked the content. But the next, commented example contains
# the 'permissive' mode, then you check only if the necessary lines exists in
# correct order. Whit this, you can enable to upload PEM files (eg "----BEGIN.."),
# or other text files, which contains eg. HTTP headers.
#
# The difference is only the operator - in strict mode (first) the content blocked
# in case of any non-zero value. In permissive mode (second, commented) the
# content blocked only if the value is explicit 1. If it 0 or 2, the content will
# allowed.
#
#
# See #1747 and #1924 for further information on the possible values for
# MULTIPART_UNMATCHED_BOUNDARY.
#
SecRule MULTIPART_UNMATCHED_BOUNDARY "@eq 1" \
"id:'200004',phase:2,t:none,log,deny,msg:'Multipart parser detected a possible unmatched boundary.'"
# PCRE Tuning
# We want to avoid a potential RegEx DoS condition
#
SecPcreMatchLimit 1000
SecPcreMatchLimitRecursion 1000
# Some internal errors will set flags in TX and we will need to look for these.
# All of these are prefixed with "MSC_". The following flags currently exist:
#
# MSC_PCRE_LIMITS_EXCEEDED: PCRE match limits were exceeded.
#
SecRule TX:/^MSC_/ "!@streq 0" \
"id:'200005',phase:2,t:none,deny,msg:'ModSecurity internal error flagged: %{MATCHED_VAR_NAME}'"
# -- Response body handling --------------------------------------------------
# Allow ModSecurity to access response bodies.
# You should have this directive enabled in order to identify errors
# and data leakage issues.
#
# Do keep in mind that enabling this directive does increases both
# memory consumption and response latency.
#
SecResponseBodyAccess On
# Which response MIME types do you want to inspect? You should adjust the
# configuration below to catch documents but avoid static files
# (e.g., images and archives).
#
SecResponseBodyMimeType text/plain text/html text/xml
# Buffer response bodies of up to 512 KB in length.
SecResponseBodyLimit 524288
# What happens when we encounter a response body larger than the configured
# limit? By default, we process what we have and let the rest through.
# That's somewhat less secure, but does not break any legitimate pages.
#
SecResponseBodyLimitAction ProcessPartial
# -- Filesystem configuration ------------------------------------------------
# The location where ModSecurity stores temporary files (for example, when
# it needs to handle a file upload that is larger than the configured limit).
#
# This default setting is chosen due to all systems have /tmp available however,
# this is less than ideal. It is recommended that you specify a location that's private.
#
SecTmpDir /tmp/
# The location where ModSecurity will keep its persistent data. This default setting
# is chosen due to all systems have /tmp available however, it
# too should be updated to a place that other users can't access.
#
SecDataDir /tmp/
# -- File uploads handling configuration -------------------------------------
# The location where ModSecurity stores intercepted uploaded files. This
# location must be private to ModSecurity. You don't want other users on
# the server to access the files, do you?
#
#SecUploadDir /opt/modsecurity/var/upload/
# By default, only keep the files that were determined to be unusual
# in some way (by an external inspection script). For this to work you
# will also need at least one file inspection rule.
#
#SecUploadKeepFiles RelevantOnly
# Uploaded files are by default created with permissions that do not allow
# any other user to access them. You may need to relax that if you want to
# interface ModSecurity to an external program (e.g., an anti-virus).
#
#SecUploadFileMode 0600
# -- Debug log configuration -------------------------------------------------
# The default debug log configuration is to duplicate the error, warning
# and notice messages from the error log.
#
#SecDebugLog /opt/modsecurity/var/log/debug.log
#SecDebugLogLevel 3
# -- Audit log configuration -------------------------------------------------
# Log the transactions that are marked by a rule, as well as those that
# trigger a server error (determined by a 5xx or 4xx, excluding 404,
# level response status codes).
#
SecAuditEngine RelevantOnly
SecAuditLogRelevantStatus "^(?:5|4(?!04))"
# Log everything we know about a transaction.
SecAuditLogParts ABIJDEFHZ
# Use a single file for logging. This is much easier to look at, but
# assumes that you will use the audit log only ocassionally.
#
SecAuditLogType Serial
SecAuditLog /var/log/modsec_audit.log
# Specify the path for concurrent audit logging.
#SecAuditLogStorageDir /opt/modsecurity/var/audit/
# -- Miscellaneous -----------------------------------------------------------
# Use the most commonly used application/x-www-form-urlencoded parameter
# separator. There's probably only one application somewhere that uses
# something else so don't expect to change this value.
#
SecArgumentSeparator &
# Settle on version 0 (zero) cookies, as that is what most applications
# use. Using an incorrect cookie version may open your installation to
# evasion attacks (against the rules that examine named cookies).
#
SecCookieFormat 0
# Specify your Unicode Code Point.
# This mapping is used by the t:urlDecodeUni transformation function
# to properly map encoded data to your language. Properly setting
# these directives helps to reduce false positives and negatives.
#
SecUnicodeMapFile unicode.mapping 20127
# Improve the quality of ModSecurity by sharing information about your
# current ModSecurity version and dependencies versions.
# The following information will be shared: ModSecurity version,
# Web Server version, APR version, PCRE version, Lua version, Libxml2
# version, Anonymous unique id for host.
SecStatusEngine On
OWASP Kurallarının Dahil Edilmesi
Ön tanımlı olarak pek bir kural seti bulunmamaktadır, sisteminize ücretsiz olarak erişebileceğiniz OWASP kurallarını dahil etmelisiniz, paralı olan kurallarda bulunmaktadır. Ücretsiz olanları için aşağıdaki adımları gerçekleştirin.
wget https://github.com/SpiderLabs/owasp-modsecurity-crs/archive/v3.2.0.tar.gz
tar -xzvf v3.2.0.tar.gz
sudo mv owasp-modsecurity-crs-3.2.0 /usr/local
cd /usr/local/owasp-modsecurity-crs-3.2.0
sudo cp crs-setup.conf.example crs-setup.confHer şey başarılı bir şekilde devam ettiğine göre sıra geldi bütün bu kuralların aktif edilmesinde bu işlem için /etc/nginx/modsec/main.conf dosyasına aşağıdaki satırları ekliyoruz.
# Include the recommended configuration
Include /etc/nginx/modsec/modsecurity.conf
# OWASP CRS v3 rules
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-901-INITIALIZATION.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-903.9001-DRUPAL-EXCLUSION-RULES.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-903.9002-WORDPRESS-EXCLUSION-RULES.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-903.9003-NEXTCLOUD-EXCLUSION-RULES.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-903.9004-DOKUWIKI-EXCLUSION-RULES.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-903.9005-CPANEL-EXCLUSION-RULES.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-903.9006-XENFORO-EXCLUSION-RULES.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-905-COMMON-EXCEPTIONS.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-910-IP-REPUTATION.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-911-METHOD-ENFORCEMENT.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-912-DOS-PROTECTION.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-913-SCANNER-DETECTION.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-920-PROTOCOL-ENFORCEMENT.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-921-PROTOCOL-ATTACK.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-930-APPLICATION-ATTACK-LFI.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-931-APPLICATION-ATTACK-RFI.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-932-APPLICATION-ATTACK-RCE.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-933-APPLICATION-ATTACK-PHP.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-934-APPLICATION-ATTACK-NODEJS.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-941-APPLICATION-ATTACK-XSS.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-942-APPLICATION-ATTACK-SQLI.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-943-APPLICATION-ATTACK-SESSION-FIXATION.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-944-APPLICATION-ATTACK-JAVA.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/REQUEST-949-BLOCKING-EVALUATION.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/RESPONSE-950-DATA-LEAKAGES.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/RESPONSE-951-DATA-LEAKAGES-SQL.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/RESPONSE-952-DATA-LEAKAGES-JAVA.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/RESPONSE-953-DATA-LEAKAGES-PHP.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/RESPONSE-954-DATA-LEAKAGES-IIS.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/RESPONSE-959-BLOCKING-EVALUATION.conf
Include /usr/local/owasp-modsecurity-crs-3.2.0/RESPONSE-980-CORRELATION.confArdından hangi alan adınızda çalışmasını istiyorsanız o server bloğuna aşağıdaki tanımlamayı yapın.
modsecurity on;
modsecurity_rules_file /etc/nginx/modsec/main.conf;Nginx’i yeniden başlattığınızda artık Mod Security tamamen aktif olacak ve güvenlik sorunlarınıza derman olacak.