mod_security на самом деле не блокирует запросы, несмотря на срабатывание правила и возврат 403

Я вытащил палец и установил mod_security, чтобы защитить нашу установку WHMCS (биллинговую систему на основе PHP) от некоторых из наиболее очевидных атак с использованием SQL-инъекций, чтобы попытаться минимизировать нашу восприимчивость к попаданию в окно возможностей между тем, как уязвимость становится известной. и мы узнаем об этом (в этот момент мы развертываем IP ACL или новые правила mod_security в зависимости от ситуации и исправляем, когда исправление доступно)

Проблема в том, что у меня есть некоторые правила, которые я взял из WHT, которые на бумаге выглядят хорошо, и когда я их тестирую, mod_security появляется чтобы сделать это - злонамеренный клиент переключается на 403, но данные POST, похоже, все еще доходят до PHP-скрипта, потому что содержимое базы данных изменяется.

PHP работает с suPHP; Из поисков Google мне не ясно, является ли это возможной причиной проблем - я не могу представить, что это такая необычная конфигурация.

На мой взгляд, вероятная причина заключается в том, что, несмотря на то, что mod_security настроен на отказ, он все равно будет генерировать тело промежуточного ответа (о чем свидетельствует тот факт, что он может регистрировать его под типом E) - это, конечно, включает отправку данных, которые я хочу перестать быть представлен в первую очередь! Однако даже если я установлю для SecResponseBodyAccess значение Off, это не остановит отправку данных - и, честно говоря, я бы не стал необоснованно ожидать, что на этапе запроса сработает правило deny / drop, которое предотвратит любую попытку сгенерировать тело ответа.

Кто-нибудь может пролить свет на это? Есть ли ошибка в этой версии mod_security (маловероятно, что я заметил бы первым), ошибочны ли правила, которые я выбрал (возможно), или есть просто глупая ошибка где-то в моей конфигурации (скорее всего)?

Это система Debian Squeeze; возможно соответствующие пакеты:

ii  apache2                             2.2.16-6+squeeze11                Apache HTTP Server metapackage
ii  libapache2-mod-suphp                0.7.1-1                           Apache2 module to run php scripts with the owner permissions
ii  libapache2-modsecurity              2.6.6-6~bpo60+1                   Tighten web applications security for Apache

/etc/apache2/mods-enabled/modsecurity.load

LoadFile /usr/lib/libxml2.so.2
LoadModule security2_module /usr/lib/apache2/modules/mod_security2.so

/etc/apache2/mods-enabled/modsecurity.conf

<IfModule security2_module>
        # Default Debian dir for modsecurity's persistent data
        SecDataDir /var/cache/modsecurity

        # Include all the *.conf files in /etc/modsecurity.
        # Keeping your local configuration in that directory
        # will allow for an easy upgrade of THIS file and
        # make your life easier
        Include "/etc/modsecurity/*.conf"
</IfModule>

/etc/modsecurity/modsecurity.conf (в значительной степени не изменилась по сравнению с рекомендуемой конфигурацией Debian по умолчанию - кроме изменения SecRuleEngine DetectionOnly на On)

# -- Rule engine initialization ----------------------------------------------

# Enable ModSecurity, attaching it to every transaction. Use detection
# only to start with, because that minimises the chances of post-installation
# disruption.
#
SecRuleEngine On


# -- Request body handling ---------------------------------------------------

# Allow ModSecurity to access request bodies. If you don't, ModSecurity
# won't be able to see any POST parameters, which opens a large security
# hole for attackers to exploit.
#
SecRequestBodyAccess On


# Enable XML request body parser.
# Initiate XML Processor in case of xml content-type
#
SecRule REQUEST_HEADERS:Content-Type "text/xml" \
     "phase:1,t:none,t:lowercase,pass,nolog,ctl:requestBodyProcessor=XML"


# 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

# Store up to 128 KB of request body data in memory. When the multipart
# parser reachers this limit, it will start using your hard disk for
# storage. That is slow, but unavoidable.
#
SecRequestBodyInMemoryLimit 131072

# What do 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" \
"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" \
"phase:2,t:none,log,deny,status:44,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_SEMICOLON_MISSING}, \
IQ %{MULTIPART_INVALID_QUOTING}, \
IQ %{MULTIPART_INVALID_PART}, \
IH %{MULTIPART_INVALID_HEADER_FOLDING}, \
IH %{MULTIPART_FILE_LIMIT_EXCEEDED}'"

# Did we see anything that might be a boundary?
#
SecRule MULTIPART_UNMATCHED_BOUNDARY "!@eq 0" \
"phase:2,t:none,log,deny,status:44,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" \
        "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).
#
# To log, use RelevantOnly
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/apache2/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

Примеры правил, относящихся к моему тесту отправки сообщения с AES_ENCRYPT в полезной нагрузке, из /etc/modsecurity/whmcs_rules.conf:

SecRule REQUEST_URI|ARGS|REQUEST_BODY "aes_encrypt" "id:00101,phase:4,t:urlDecodeUni,t:htmlEntityDecode,t:replaceComments,t:compressWhiteSpace,t:lowercase,log,deny,msg:'WHMCS'"
SecRule REQUEST_URI|ARGS|REQUEST_BODY "aes_encrypt" "id:00102,phase:4,t:urlDecodeUni,t:htmlEntityDecode,t:hexDecode,t:replaceComments,t:compressWhiteSpace,t:lowercase,log,deny,msg:'WHMCS'"

/var/log/modsec_audit.log (фрагмент)

--bc497c3a-A--
[30/Oct/2013:12:33:19 +0000] UnD8jtXm0XMAABtcO10AAABA <client> 65312 <server> 443

--bc497c3a-B--
**logged, but trimmed for privacy**

--bc497c3a-C--
**logged, but trimmed for privacy**

--bc497c3a-F--
HTTP/1.1 403 Forbidden
X-Powered-By: PHP/5.3.3-7+squeeze17, PHP/5.3.3-7+squeeze17
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Vary: Accept-Encoding
Content-Encoding: gzip
Keep-Alive: timeout=15, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: text/html; charset=UTF-8

--bc497c3a-E--
**response that is generated by the PHP script when the POST is submitted**

--bc497c3a-H--
Message: Access denied with code 403 (phase 4). Pattern match "aes_encrypt" at ARGS:firstname. [file "/etc/modsecurity/whmcs_rules.conf"] [line "41"] [id "00101"] [msg "WHMCS"]
Action: Intercepted (phase 4)
Stopwatch: 1383136398855159 530401 (- - -)
Stopwatch2: 1383136398855159 530401; combined=1155, p1=16, p2=14, p3=3, p4=1115, p5=6, sr=0, sw=1, l=0, gc=0
Response-Body-Transformed: Dechunked
Producer: ModSecurity for Apache/2.6.6 (http://www.modsecurity.org/).
Server: Apache/2.2.16 (Debian) mod_ssl/2.2.16 OpenSSL/0.9.8o

--bc497c3a-Z--