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The following section outlines all of the ModSecurity directives.
Most of the ModSecurity directives can be used inside the various Apache
Scope Directives such as VirtualHost,
Location, LocationMatch,
Directory, etc... There are others, however, that can
only be used once in the main configuration file. This information is
specified in the Scope sections below. The first version to use a given
directive is given in the Version sections below.
These rules, along with the Core rules files, should be contained is
files outside of the httpd.conf file and called up with Apache "Include"
directives. This allows for easier updating/migration of the rules. If you
create your own custom rules that you would like to use with the Core
rules, you should create a file called -
modsecurity_crs_15_customrules.conf and place it in
the same directory as the Core rules files. By using this file name, your
custom rules will be called up after the standard ModSecurity Core rules
configuration file but before the other Core rules. This allows your rules
to be evaluated first which can be useful if you need to implement
specific "allow" rules or to correct any false positives in the Core rules
as they are applied to your site.
It is highly encouraged that you do not edit the Core rules files
themselves but rather place all changes (such as
SecRuleRemoveByID, etc...) in your custom rules file.
This will allow for easier upgrading as newer Core rules are released by
Breach Security on the ModSecurity website.
Description: Unconditionally processes the
action list it receives as the first and only parameter. It accepts one
parameter, the syntax of which is identical to the third parameter
of SecRule.
Syntax: SecAction
action1,action2,action3
Example Usage: SecAction
nolog,phase:1,initcol:RESOURCE=%{REQUEST_FILENAME}
Processing Phase: Any
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
SecAction is best used when you unconditionally execute an action.
This is explicit triggering whereas the normal Actions are conditional
based on data inspection of the request/response. This is a useful
directive when you want to run certain actions such as
initcol to initialize collections.
Description: Specifies which character to use
as separator for
application/x-www-form-urlencoded content. Defaults to
&. Applications are sometimes
(very rarely) written to use a semicolon (;).
Syntax: SecArgumentSeparator character
Example Usage: SecArgumentSeparator ;
Processing Phase: Any
Scope: Main
Version: 2.0.0
Dependencies/Notes: None
This directive is needed if a backend web application is using a non-standard argument separator. If this directive is not set properly for each web application, then ModSecurity will not be able to parse the arguments appropriately and the effectiveness of the rule matching will be significantly decreased.
Description: Configures the audit logging engine.
Syntax: SecAuditEngine On|Off|RelevantOnly
Example Usage: SecAuditEngine On
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: Can be set/changed with
the "ctl" action for the current transaction.
Example: The following example shows the various audit directives used together.
SecAuditEngine RelevantOnly SecAuditLog logs/audit/audit.log SecAuditLogParts ABCFHZ SecAuditLogType concurrent SecAuditLogStorageDir logs/audit SecAuditLogRelevantStatus ^(?:5|4\d[^4])
Possible values are:
On - log all transactions
by default.
Off - do not log
transactions by default.
RelevantOnly - by default
only log transactions that have triggered a warning or an error, or
have a status code that is considered to be relevant (see SecAuditLogRelevantStatus).
Description: Defines the path to the main audit log file.
Syntax: SecAuditLog
/path/to/auditlog
Example Usage: SecAuditLog
/usr/local/apache/logs/audit.log
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: This file is open on startup when the server typically still runs as root. You should not allow non-root users to have write privileges for this file or for the directory it is stored in..
This file will be used to store the audit log entries if serial audit logging format is used. If concurrent audit logging format is used this file will be used as an index, and contain a record of all audit log files created. If you are planning to use Concurrent audit logging and sending your audit log data off to a remote Console host or commercial ModSecurity Management Appliance, then you will need to configure and use the ModSecurity Log Collector (mlogc) and use the following format for the audit log:
SecAuditLog "|/path/to/mlogc /path/to/mlogc.conf"
Description: Defines the path to the
secondary audit log index file when concurrent logging is enabled. See
SecAuditLog2 for more details.
Syntax: SecAuditLog2
/path/to/auditlog2
Example Usage: SecAuditLog2
/usr/local/apache/logs/audit2.log
Processing Phase: N/A
Scope: Any
Version: 2.1.2
Dependencies/Notes: A main audit log must be
defined via SecAuditLog before this
directive may be used. Additionally, this log is only used for
replicating the main audit log index file when concurrent audit logging
is used. It will not be used for non-concurrent
audit logging.
Description: Configures the mode
(permissions) of any directories created for concurrent audit logs using
an octal mode (as used in chmod). See SecAuditLogFileMode for controlling the mode
of audit log files.
Syntax: SecAuditLogDirMode octal_mode|"default"
Example Usage: SecAuditLogDirMode 02750
Processing Phase: N/A
Scope: Any
Version: 2.5.10
Dependencies/Notes: This feature is not available on operating systems not supporting octal file modes. The default mode (0600) only grants read/write access to the account writing the file. If access from another account is needed (using mpm-itk is a good example), then this directive may be required. However, use this directive with caution to avoid exposing potentially sensitive data to unauthorized users. Using the value "default" will revert back to the default setting.
The process umask may still limit the mode if it is being more restrictive than the mode set using this directive.
Description: Configures the mode
(permissions) of any files created for concurrent audit logs using an
octal mode (as used in chmod). See SecAuditLogDirMode for controlling the mode of
created audit log directories.
Syntax: SecAuditLogFileMode
octal_mode|"default"
Example Usage: SecAuditLogFileMode 00640
Processing Phase: N/A
Scope: Any
Version: 2.5.10
Dependencies/Notes: This feature is not available on operating systems not supporting octal file modes. The default mode (0600) only grants read/write access to the account writing the file. If access from another account is needed (using mpm-itk is a good example), then this directive may be required. However, use this directive with caution to avoid exposing potentially sensitive data to unauthorized users. Using the value "default" will revert back to the default setting.
The process umask may still limit the mode if it is being more restrictive than the mode set using this directive.
Description: Defines which part of each transaction are going to be recorded in audit log. Each part is assigned a single letter. If a letter appears in the list then the equivalent part of each transactions will be recorded. See below for the list of all parts.
Syntax: SecAuditLogParts PARTS
Example Usage: SecAuditLogParts ABCFHZ
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: At this time ModSecurity
does not log response bodies of stock Apache responses (e.g. 404), or the Server and Date response headers.
Default: ABCFHZ.
Please refer to the ModSecurity Data Formats document for a detailed description of every available part.
Available audit log parts:
A - audit log header
(mandatory)
B - request headers
C - request body (present
only if the request body exists and ModSecurity is configured to
intercept it)
D - RESERVED for
intermediary response headers, not implemented yet.
E - intermediary response
body (present only if ModSecurity is configured to intercept
response bodies, and if the audit log engine is configured to record
it). Intermediary response body is the same as the actual response
body unless ModSecurity intercepts the intermediary response body,
in which case the actual response body will contain the error
message (either the Apache default error message, or the
ErrorDocument page).
F - final response headers
(excluding the Date and Server headers, which are always added by
Apache in the late stage of content delivery).
G - RESERVED for the actual
response body, not implemented yet.
H - audit log
trailer
I - This part is a
replacement for part C. It will log the same data as C in all cases
except when multipart/form-data
encoding in used. In this case it will log a fake application/x-www-form-urlencoded body
that contains the information about parameters but not about the
files. This is handy if you don't want to have (often large) files
stored in your audit logs.
J - RESERVED. This part,
when implemented, will contain information about the files uploaded
using multipart/form-data encoding.
K - This part contains a
full list of every rule that matched (one per line) in the order
they were matched. The rules are fully qualified and will thus show
inherited actions and default operators. Supported as of
v2.5.0
Z - final boundary,
signifies the end of the entry (mandatory)
Description: Configures which response status code is to be considered relevant for the purpose of audit logging.
Syntax: SecAuditLogRelevantStatus REGEX
Example Usage: SecAuditLogRelevantStatus
^(?:5|4\d[^4])
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: Must have the
SecAuditEngine set to
RelevantOnly. The parameter is a regular
expression.
The main purpose of this directive is to allow you to configure audit logging for only transactions that generate the specified HTTP Response Status Code. This directive is often used to the decrease the total size of the audit log file. Keep in mind that if this parameter is used, then successful attacks that result in a 200 OK status code will not be logged.
Description: Configures the storage directory where concurrent audit log entries are to be stored.
Syntax: SecAuditLogStorageDir
/path/to/storage/dir
Example Usage: SecAuditLogStorageDir
/usr/local/apache/logs/audit
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: SecAuditLogType must be set to Concurrent. The directory must already be created before starting Apache and it must be writable by the web server user as new files are generated at runtime.
As with all logging mechanisms, ensure that you specify a file system location that has adequate disk space and is not on the root partition.
Description: Configures the type of audit logging mechanism to be used.
Syntax: SecAuditLogType Serial|Concurrent
Example Usage: SecAuditLogType Serial
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: Must specify
SecAuditLogStorageDir if you use concurrent
logging.
Possible values are:
Serial - all audit log
entries will be stored in the main audit logging file. This is more
convenient for casual use but it is slower as only one audit log
entry can be written to the file at any one file.
Concurrent - audit log
entries will be stored in separate files, one for each transaction.
Concurrent logging is the mode to use if you are going to send the
audit log data off to a remote ModSecurity Console host.
Description: Controls caching of transformations. Caching is off by default starting with 2.5.6, when it was deprecated and downgraded back to experimental.
Syntax: SecCacheTransformations On|Off
[options]
Example Usage: SecCacheTransformations On
"minlen:64,maxlen:0"
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: N/A
First parameter:
On - cache transformations
(per transaction, per phase) allowing identical transformations to
be performed only once. (default)
Off - do not cache any
transformations, forcing all transformations to be performed for
each rule executed.
The following options are allowed (comma separated):
incremental:on|off -
enabling this option will cache every transformation instead of just
the final transformation. (default: off)
maxitems:N - do not allow
more than N transformations to be cached. The cache will then be
disabled. A zero value is interpreted as "unlimited". This option
may be useful to limit caching for a form with a large number of
ARGS. (default: 512)
minlen:N - do not cache the
transformation if the value's length is less than N bytes. (default:
32)
maxlen:N - do not cache the
transformation if the value's length is more than N bytes. A zero
value is interpreted as "unlimited". (default: 1024)
Description: Configures the directory path that will be used to jail the web server process.
Syntax: SecChrootDir
/path/to/chroot/dir
Example Usage: SecChrootDir /chroot
Processing Phase: N/A
Scope: Main
Version: 2.0.0
Dependencies/Notes: This feature is not available on Windows builds. The internal chroot functionality provided by ModSecurity works great for simple setups. One example of a simple setup is Apache serving static files only, or running scripts using modules.builds. Some problems you might encounter with more complex setups:
DNS lookups do not work (this is because this feature requires a shared library that is loaded on demand, after chroot takes place).
You cannot send email from PHP because it uses sendmail and sendmail is outside the jail.
In some cases Apache graceful (reload) no longer works.
You should be aware that the internal chroot feature might not be
100% reliable. Due to the large number of default and third-party
modules available for the Apache web server, it is not possible to
verify the internal chroot works reliably with all of them. A module,
working from within Apache, can do things that make it easy to break out
of the jail. In particular, if you are using any of the modules that
fork in the module initialisation phase (e.g.
mod_fastcgi, mod_fcgid,
mod_cgid), you are advised to examine each Apache
process and observe its current working directory, process root, and the
list of open files. Consider what your options are and make your own
decision.
Description: Appends component signature to the ModSecurity signature.
Syntax: SecComponentSignature
"COMPONENT_NAME/X.Y.Z (COMMENT)"
Example usage: SecComponentSignature
"Core Rules/1.2.3"
Processing Phase: N/A
Scope: Main
Version: 2.5.0
Dependencies/Notes: This directive should be used to make the presence of significant ModSecurity components known. The entire signature will be recorded in transaction audit log. It should be used by ModSecurity module and rule set writers to make debugging easier.
Description: Enables content injection using
actions append and prepend.
Syntax: SecContentInjection
(On|Off)
Example Usage: SecContentInjection
On
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: N/A
Description: Selects the cookie format that will be used in the current configuration context.
Syntax: SecCookieFormat 0|1
Example Usage: SecCookieFormat 0
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Possible values are:
0 - use version 0
(Netscape) cookies. This is what most applications use. It is the
default value.
1 - use version 1
cookies.
Description: Path where persistent data (e.g. IP address data, session data, etc) is to be stored.
Syntax: SecDataDir
/path/to/dir
Example Usage: SecDataDir /usr/local/apache/logs/data
Processing Phase: N/A
Scope: Main
Dependencies/Notes: This directive is needed when initcol, setsid an setuid are used. Must be writable by the web server user.
Description: Path to the ModSecurity debug log file.
Syntax: SecDebugLog
/path/to/modsec-debug.log
Example Usage: SecDebugLog
/usr/local/apache/logs/modsec-debug.log
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Description: Configures the verboseness of the debug log data.
Syntax: SecDebugLogLevel 0|1|2|3|4|5|6|7|8|9
Example Usage: SecDebugLogLevel 4
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: Levels 1 - 3 are always sent to the Apache error log.
Therefore you can always use level 0
as the default logging level in production. Level 5 is useful when debugging. It is not
advisable to use higher logging levels in production as excessive
logging can slow down server significantly.
Possible values are:
0 - no logging.
1 - errors (intercepted
requests) only.
2 - warnings.
3 - notices.
4 - details of how
transactions are handled.
5 - as above, but including
information about each piece of information handled.
9 - log everything,
including very detailed debugging information.
Description: Defines the default action to take on a rule match.
Syntax: SecDefaultAction
action1,action2,action3
Example Usage: SecDefaultAction
log,auditlog,deny,status:403,phase:2
Processing Phase: Any
Scope: Any
Version: 2.0.0
Dependencies/Notes: Rules following a
SecDefaultAction directive will inherit this setting
unless a specific action is specified for an individual rule or until
another SecDefaultAction is specified. Take special
note that in the logging disruptive actions are not allowed, but this
can inadvertently be inherited using a disruptive action in
SecDefaultAction.
The default value is minimal (differing from previous versions):
SecDefaultAction phase:2,log,auditlog,pass
SecDefaultAction must specify a disruptive
action and a processing phase and cannot contain metadata
actions.
SecDefaultAction is not
inherited across configuration contexts. (For an example of why this
may be a problem for you, read the following ModSecurity Blog entry
http://blog.modsecurity.org/2008/07/modsecurity-tri.html).
Description: Defines the path to the geographical database file.
Syntax: SecGeoLookupDb /path/to/db
Example Usage: SecGeoLookupDb
/usr/local/geo/data/GeoLiteCity.dat
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: Check out
maxmind.com for free database files.
Description: Configuration directive to use the httpd-guardian script to monitor for Denial of Service (DoS) attacks.
Syntax: SecGuardianLog |/path/to/httpd-guardian
Example Usage: SecGuardianLog
|/usr/local/apache/bin/httpd-guardian
Processing Phase: N/A
Scope: Main
Version: 2.0.0
Dependencies/Notes: By default httpd-guardian will defend against clients that send more than 120 requests in a minute, or more than 360 requests in five minutes.
Since 1.9, ModSecurity supports a new directive, SecGuardianLog, that is designed to send all access data to another program using the piped logging feature. Since Apache is typically deployed in a multi-process fashion, making information sharing difficult, the idea is to deploy a single external process to observe all requests in a stateful manner, providing additional protection.
Development of a state of the art external protection tool will be a focus of subsequent ModSecurity releases. However, a fully functional tool is already available as part of the Apache httpd tools project. The tool is called httpd-guardian and can be used to defend against Denial of Service attacks. It uses the blacklist tool (from the same project) to interact with an iptables-based (Linux) or pf-based (*BSD) firewall, dynamically blacklisting the offending IP addresses. It can also interact with SnortSam (http://www.snortsam.net). Assuming httpd-guardian is already configured (look into the source code for the detailed instructions) you only need to add one line to your Apache configuration to deploy it:
SecGuardianLog |/path/to/httpd-guardian
Description: Adds a fixed rule marker in the
ruleset to be used as a target in a skipAfter action.
A SecMarker directive essentially creates a rule that
does nothing and whose only purpose it to carry the given ID.
Syntax: SecMarker
ID
Example Usage: SecMarker 9999
Processing Phase: Any
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
SecRule REQUEST_URI "^/$" \
"chain,t:none,t:urlDecode,t:lowercase,t:normalisePath,skipAfter:99"
SecRule REMOTE_ADDR "^127\.0\.0\.1$" "chain"
SecRule REQUEST_HEADERS:User-Agent \
"^Apache \(internal dummy connection\)$" "t:none"
SecRule &REQUEST_HEADERS:Host "@eq 0" \
"deny,log,status:400,id:08,severity:4,msg:'Missing a Host Header'"
SecRule &REQUEST_HEADERS:Accept "@eq 0" \
"log,deny,log,status:400,id:15,msg:'Request Missing an Accept Header'"
SecMarker 99Description: Enables the PDF XSS protection
functionality. Once enabled access to PDF files is tracked. Direct
access attempts are redirected to links that contain one-time tokens.
Requests with valid tokens are allowed through unmodified. Requests with
invalid tokens are also allowed through but with forced download of the
PDF files. This implementation uses response headers to detect PDF files
and thus can be used with dynamically generated PDF files that do not
have the .pdf extension in the request URI.
Syntax: SecPdfProtect On|Off
Example Usage: SecPdfProtect On
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
Description: Configure desired protection
method to be used when requests for PDF files are detected. Possible
values are TokenRedirection and
ForcedDownload. The token redirection approach will
attempt to redirect with tokens where possible. This allows PDF files to
continue to be opened inline but only works for GET requests. Forced
download always causes PDF files to be delivered as opaque binaries and
attachments. The latter will always be used for non-GET requests. Forced
download is considered to be more secure but may cause usability
problems for users ("This PDF won't open anymore!").
Syntax: SecPdfProtectMethod method
Example Usage: SecPdfProtectMethod TokenRedirection
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
Default:
TokenRedirection
Description: Defines the secret that will be used to construct one-time tokens. You should use a reasonably long value for the secret (e.g. 16 characters is good). Once selectode>
Processing Phase: N/A
Scope: Main
Version: 2.5.0
Dependencies/Notes: This directive should be used to make the presence of significant ModSecurity components known. The entire signature will be recorded in transaction audit log. It should be used by ModSecurity module and rule set writers to make debugging easier.
Description: Enables content injection using
actions append and prepend.
Syntax: SecContentInjection
(On|Off)
Example Usage: SecContentInjection
On
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: N/A
Description: Selects the cookie format that will be used in the current configuration context.
Syntax: SecCookieFormat 0|1
Example Usage: SecCookieFormat 0
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Possible values are:
0 - use version 0
(Netscape) cookies. This is what most applications use. It is the
default value.
1 - use version 1
cookies.
Description: Path where persistent data (e.g. IP address data, session data, etc) is to be stored.
Syntax: SecDataDir
/path/to/dir
Example Usage: SecDataDir /usr/local/apache/logs/data
Processing Phase: N/A
Scope: Main
Dependencies/Notes: This directive is needed when initcol, setsid an setuid are used. Must be writable by the web server user.
Description: Path to the ModSecurity debug log file.
Syntax: SecDebugLog
/path/to/modsec-debug.log
Example Usage: SecDebugLog
/usr/local/apache/logs/modsec-debug.log
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Description: Configures the verboseness of the debug log data.
Syntax: SecDebugLogLevel 0|1|2|3|4|5|6|7|8|9
Example Usage: SecDebugLogLevel 4
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: Levels 1 - 3 are always sent to the Apache error log.
Therefore you can always use level 0
as the default logging level in production. Level 5 is useful when debugging. It is not
advisable to use higher logging levels in production as excessive
logging can slow down server significantly.
Possible values are:
0 - no logging.
1 - errors (intercepted
requests) only.
2 - warnings.
3 - notices.
4 - details of how
transactions are handled.
5 - as above, but including
information about each piece of information handled.
9 - log everything,
including very detailed debugging information.
Description: Defines the default action to take on a rule match.
Syntax: SecDefaultAction
action1,action2,action3
Example Usage: SecDefaultAction
log,auditlog,deny,status:403,phase:2
Processing Phase: Any
Scope: Any
Version: 2.0.0
Dependencies/Notes: Rules following a
SecDefaultAction directive will inherit this setting
unless a specific action is specified for an individual rule or until
another SecDefaultAction is specified. Take special
note that in the logging disruptive actions are not allowed, but this
can inadvertently be inherited using a disruptive action in
SecDefaultAction.
The default value is minimal (differing from previous versions):
SecDefaultAction phase:2,log,auditlog,pass
SecDefaultAction must specify a disruptive
action and a processing phase and cannot contain metadata
actions.
SecDefaultAction is not
inherited across configuration contexts. (For an example of why this
may be a problem for you, read the following ModSecurity Blog entry
http://blog.modsecurity.org/2008/07/modsecurity-tri.html).
Description: Defines the path to the geographical database file.
Syntax: SecGeoLookupDb /path/to/db
Example Usage: SecGeoLookupDb
/usr/local/geo/data/GeoLiteCity.dat
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: Check out
maxmind.com for free database files.
Description: Configuration directive to use the httpd-guardian script to monitor for Denial of Service (DoS) attacks.
Syntax: SecGuardianLog |/path/to/httpd-guardian
Example Usage: SecGuardianLog
|/usr/local/apache/bin/httpd-guardian
Processing Phase: N/A
Scope: Main
Version: 2.0.0
Dependencies/Notes: By default httpd-guardian will defend against clients that send more than 120 requests in a minute, or more than 360 requests in five minutes.
Since 1.9, ModSecurity supports a new directive, SecGuardianLog, that is designed to send all access data to another program using the piped logging feature. Since Apache is typically deployed in a multi-process fashion, making information sharing difficult, the idea is to deploy a single external process to observe all requests in a stateful manner, providing additional protection.
Development of a state of the art external protection tool will be a focus of subsequent ModSecurity releases. However, a fully functional tool is already available as part of the Apache httpd tools project. The tool is called httpd-guardian and can be used to defend against Denial of Service attacks. It uses the blacklist tool (from the same project) to interact with an iptables-based (Linux) or pf-based (*BSD) firewall, dynamically blacklisting the offending IP addresses. It can also interact with SnortSam (http://www.snortsam.net). Assuming httpd-guardian is already configured (look into the source code for the detailed instructions) you only need to add one line to your Apache configuration to deploy it:
SecGuardianLog |/path/to/httpd-guardian
Description: Adds a fixed rule marker in the
ruleset to be used as a target in a skipAfter action.
A SecMarker directive essentially creates a rule that
does nothing and whose only purpose it to carry the given ID.
Syntax: SecMarker
ID
Example Usage: SecMarker 9999
Processing Phase: Any
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
SecRule REQUEST_URI "^/$" \
"chain,t:none,t:urlDecode,t:lowercase,t:normalisePath,skipAfter:99"
SecRule REMOTE_ADDR "^127\.0\.0\.1$" "chain"
SecRule REQUEST_HEADERS:User-Agent \
"^Apache \(internal dummy connection\)$" "t:none"
SecRule &REQUEST_HEADERS:Host "@eq 0" \
"deny,log,status:400,id:08,severity:4,msg:'Missing a Host Header'"
SecRule &REQUEST_HEADERS:Accept "@eq 0" \
"log,deny,log,status:400,id:15,msg:'Request Missing an Accept Header'"
SecMarker 99Description: Enables the PDF XSS protection
functionality. Once enabled access to PDF files is tracked. Direct
access attempts are redirected to links that contain one-time tokens.
Requests with valid tokens are allowed through unmodified. Requests with
invalid tokens are also allowed through but with forced download of the
PDF files. This implementation uses response headers to detect PDF files
and thus can be used with dynamically generated PDF files that do not
have the .pdf extension in the request URI.
Syntax: SecPdfProtect On|Off
Example Usage: SecPdfProtect On
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
Description: Configure desired protection
method to be used when requests for PDF files are detected. Possible
values are TokenRedirection and
ForcedDownload. The token redirection approach will
attempt to redirect with tokens where possible. This allows PDF files to
continue to be opened inline but only works for GET requests. Forced
download always causes PDF files to be delivered as opaque binaries and
attachments. The latter will always be used for non-GET requests. Forced
download is considered to be more secure but may cause usability
problems for users ("This PDF won't open anymore!").
Syntax: SecPdfProtectMethod method
Example Usage: SecPdfProtectMethod TokenRedirection
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
Default:
TokenRedirection
Description: Defines the secret that will be used to construct one-time tokens. You should use a reasonably long value for the secret (e.g. 16 characters is good). Once selectode>
Processing Phase: N/A
Scope: Main
Version: 2.5.0
Dependencies/Notes: This directive should be used to make the presence of significant ModSecurity components known. The entire signature will be recorded in transaction audit log. It should be used by ModSecurity module and rule set writers to make debugging easier.
Description: Enables content injection using
actions append and prepend.
Syntax: SecContentInjection
(On|Off)
Example Usage: SecContentInjection
On
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: N/A
Description: Selects the cookie format that will be used in the current configuration context.
Syntax: SecCookieFormat 0|1
Example Usage: SecCookieFormat 0
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Possible values are:
0 - use version 0
(Netscape) cookies. This is what most applications use. It is the
default value.
1 - use version 1
cookies.
Description: Path where persistent data (e.g. IP address data, session data, etc) is to be stored.
Syntax: SecDataDir
/path/to/dir
Example Usage: SecDataDir /usr/local/apache/logs/data
Processing Phase: N/A
Scope: Main
Dependencies/Notes: This directive is needed when initcol, setsid an setuid are used. Must be writable by the web server user.
Description: Path to the ModSecurity debug log file.
Syntax: SecDebugLog
/path/to/modsec-debug.log
Example Usage: SecDebugLog
/usr/local/apache/logs/modsec-debug.log
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Description: Configures the verboseness of the debug log data.
Syntax: SecDebugLogLevel 0|1|2|3|4|5|6|7|8|9
Example Usage: SecDebugLogLevel 4
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: Levels 1 - 3 are always sent to the Apache error log.
Therefore you can always use level 0
as the default logging level in production. Level 5 is useful when debugging. It is not
advisable to use higher logging levels in production as excessive
logging can slow down server significantly.
Possible values are:
0 - no logging.
1 - errors (intercepted
requests) only.
2 - warnings.
3 - notices.
4 - details of how
transactions are handled.
5 - as above, but including
information about each piece of information handled.
9 - log everything,
including very detailed debugging information.
Description: Defines the default action to take on a rule match.
Syntax: SecDefaultAction
action1,action2,action3
Example Usage: SecDefaultAction
log,auditlog,deny,status:403,phase:2
Processing Phase: Any
Scope: Any
Version: 2.0.0
Dependencies/Notes: Rules following a
SecDefaultAction directive will inherit this setting
unless a specific action is specified for an individual rule or until
another SecDefaultAction is specified. Take special
note that in the logging disruptive actions are not allowed, but this
can inadvertently be inherited using a disruptive action in
SecDefaultAction.
The default value is minimal (differing from previous versions):
SecDefaultAction phase:2,log,auditlog,pass
SecDefaultAction must specify a disruptive
action and a processing phase and cannot contain metadata
actions.
SecDefaultAction is not
inherited across configuration contexts. (For an example of why this
may be a problem for you, read the following ModSecurity Blog entry
http://blog.modsecurity.org/2008/07/modsecurity-tri.html).
Description: Defines the path to the geographical database file.
Syntax: SecGeoLookupDb /path/to/db
Example Usage: SecGeoLookupDb
/usr/local/geo/data/GeoLiteCity.dat
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: Check out
maxmind.com for free database files.
Description: Configuration directive to use the httpd-guardian script to monitor for Denial of Service (DoS) attacks.
Syntax: SecGuardianLog |/path/to/httpd-guardian
Example Usage: SecGuardianLog
|/usr/local/apache/bin/httpd-guardian
Processing Phase: N/A
Scope: Main
Version: 2.0.0
Dependencies/Notes: By default httpd-guardian will defend against clients that send more than 120 requests in a minute, or more than 360 requests in five minutes.
Since 1.9, ModSecurity supports a new directive, SecGuardianLog, that is designed to send all access data to another program using the piped logging feature. Since Apache is typically deployed in a multi-process fashion, making information sharing difficult, the idea is to deploy a single external process to observe all requests in a stateful manner, providing additional protection.
Development of a state of the art external protection tool will be a focus of subsequent ModSecurity releases. However, a fully functional tool is already available as part of the Apache httpd tools project. The tool is called httpd-guardian and can be used to defend against Denial of Service attacks. It uses the blacklist tool (from the same project) to interact with an iptables-based (Linux) or pf-based (*BSD) firewall, dynamically blacklisting the offending IP addresses. It can also interact with SnortSam (http://www.snortsam.net). Assuming httpd-guardian is already configured (look into the source code for the detailed instructions) you only need to add one line to your Apache configuration to deploy it:
SecGuardianLog |/path/to/httpd-guardian
Description: Adds a fixed rule marker in the
ruleset to be used as a target in a skipAfter action.
A SecMarker directive essentially creates a rule that
does nothing and whose only purpose it to carry the given ID.
Syntax: SecMarker
ID
Example Usage: SecMarker 9999
Processing Phase: Any
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
SecRule REQUEST_URI "^/$" \
"chain,t:none,t:urlDecode,t:lowercase,t:normalisePath,skipAfter:99"
SecRule REMOTE_ADDR "^127\.0\.0\.1$" "chain"
SecRule REQUEST_HEADERS:User-Agent \
"^Apache \(internal dummy connection\)$" "t:none"
SecRule &REQUEST_HEADERS:Host "@eq 0" \
"deny,log,status:400,id:08,severity:4,msg:'Missing a Host Header'"
SecRule &REQUEST_HEADERS:Accept "@eq 0" \
"log,deny,log,status:400,id:15,msg:'Request Missing an Accept Header'"
SecMarker 99Description: Enables the PDF XSS protection
functionality. Once enabled access to PDF files is tracked. Direct
access attempts are redirected to links that contain one-time tokens.
Requests with valid tokens are allowed through unmodified. Requests with
invalid tokens are also allowed through but with forced download of the
PDF files. This implementation uses response headers to detect PDF files
and thus can be used with dynamically generated PDF files that do not
have the .pdf extension in the request URI.
Syntax: SecPdfProtect On|Off
Example Usage: SecPdfProtect On
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
Description: Configure desired protection
method to be used when requests for PDF files are detected. Possible
values are TokenRedirection and
ForcedDownload. The token redirection approach will
attempt to redirect with tokens where possible. This allows PDF files to
continue to be opened inline but only works for GET requests. Forced
download always causes PDF files to be delivered as opaque binaries and
attachments. The latter will always be used for non-GET requests. Forced
download is considered to be more secure but may cause usability
problems for users ("This PDF won't open anymore!").
Syntax: SecPdfProtectMethod method
Example Usage: SecPdfProtectMethod TokenRedirection
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: None
Default:
TokenRedirection
Description: Defines the secret that will be used to construct one-time tokens. You should use a reasonably long value for the secret (e.g. 16 characters is good). Once selectode>
Processing Phase: N/A
Scope: Main
Version: 2.5.0
Dependencies/Notes: This directive should be used to make the presence of significant ModSecurity components known. The entire signature will be recorded in transaction audit log. It should be used by ModSecurity module and rule set writers to make debugging easier.
Description: Enables content injection using
actions append and prepend.
Syntax: SecContentInjection
(On|Off)
Example Usage: SecContentInjection
On
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: N/A
Description: Selects the cookie format that will be used in the current configuration context.
Syntax: SecCookieFormat 0|1
Example Usage: SecCookieFormat 0
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Possible values are:
0 - use version 0
(Netscape) cookies. This is what most applications use. It is the
default value.
1 - use version 1
cookies.
Description: Path where persistent data (e.g. IP address data, session data, etc) is to be stored.
Syntax: SecDataDir
/path/to/dir
Example Usage: SecDataDir /usr/local/apache/logs/data
Processing Phase: N/A
Scope: Main
Dependencies/Notes: This directive is needed when initcol, setsid an setuid are used. Must be writable by the web server user.
Description: Path to the ModSecurity debug log file.
Syntax: SecDebugLog
/path/to/modsec-debug.log
Example Usage: SecDebugLog
/usr/local/apache/logs/modsec-debug.log
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: None
Description: Configures the verboseness of the debug log data.
Syntax: SecDebugLogLevel 0|1|2|3|4|5|6|7|8|9
Example Usage: SecDebugLogLevel 4
Processing Phase: N/A
Scope: Any
Version: 2.0.0
Dependencies/Notes: Levels 1 - 3 are always sent to the Apache error log.
Therefore you can always use level 0
as the default logging level in production. Level 5 is useful when debugging. It is not
advisable to use higher logging levels in production as excessive
logging can slow down server significantly.
Possible values are:
0 - no logging.
1 - errors (intercepted
requests) only.
2 - warnings.
3 - notices.
4 - details of how
transactions are handled.
5 - as above, but including
information about each piece of information handled.
9 - log everything,
including very detailed debugging information.
Description: Defines the default action to take on a rule match.
Syntax: SecDefaultAction
action1,action2,action3
Example Usage: SecDefaultAction
log,auditlog,deny,status:403,phase:2
Processing Phase: Any
Scope: Any
Version: 2.0.0
Dependencies/Notes: Rules following a
SecDefaultAction directive will inherit this setting
unless a specific action is specified for an individual rule or until
another SecDefaultAction is specified. Take special
note that in the logging disruptive actions are not allowed, but this
can inadvertently be inherited using a disruptive action in
SecDefaultAction.
The default value is minimal (differing from previous versions):
SecDefaultAction phase:2,log,auditlog,pass
SecDefaultAction must specify a disruptive
action and a processing phase and cannot contain metadata
actions.
SecDefaultAction is not
inherited across configuration contexts. (For an example of why this
may be a problem for you, read the following ModSecurity Blog entry
http://blog.modsecurity.org/2008/07/modsecurity-tri.html).
Description: Defines the path to the geographical database file.
Syntax: SecGeoLookupDb /path/to/db
Example Usage: SecGeoLookupDb
/usr/local/geo/data/GeoLiteCity.dat
Processing Phase: N/A
Scope: Any
Version: 2.5.0
Dependencies/Notes: Check out
maxmind.com for free database files.
Description: Configuration directive to use the httpd-guardian script to monitor for Denial of Service (DoS) attacks.
Syntax: SecGuardianLog |/path/to/httpd-guardian
Example Usage: SecGuardianLog
|/usr/local/apache/bin/httpd-guardian
Processing Phase: N/A
Scope: Main
Version: 2.0.0
Dependencies/Notes: By default httpd-guardian will defend against clients that send more than 120 requests in a minute, or more than 360 requests in five minutes.
Since 1.9, ModSecurity supports a new directive, SecGuardianLog, that is designed to send all access data to another program using the piped logging feature. Since Apache is typically deployed in a multi-process fashion, making information sharing difficult, the idea is to deploy a single external process to observe all requests in a stateful manner, providing additional protection.
Development of a state of the art external protection tool will be a focus of subsequent ModSecurity releases. However, a fully functional tool is already available as part of the Apache httpd tools project. The tool is called httpd-guardian and can be used to defend against Denial of Service attacks. It uses the blacklist tool (from the same project) to interact with an iptables-based (Linux) or pf-based (*BSD) firewall, dynamically blacklisting the offending IP addresses. It can also interact with SnortSam (http://www.snortsam.net). Assuming httpd-guardian is already configured (look into the source code for the detailed instructions) you only need to add one line to your Apache configuration to deploy it:
SecGuardianLog |/path/to/httpd-guardian
Description: Adds a fixed rule marker in the
ruleset to be used as a target in a skipAfter action.
A SecMarker directive essentially creates a rule that
does nothing and whose only purpose it to carry the given ID.
Syntax: SecMarker
ID
Example Usage: SecMarker 9999
Processing Phase: Any
Scope: Any
Version: 2.5.0