Container Provided Filters

Table of Contents

Introduction

Tomcat provides a number of Filters which may be configured for use with all web applications using $CATALINA_BASE/conf/web.xml or may be configured for individual web applications by configuring them in the application's WEB-INF/web.xml. Each filter is described below.

This description uses the variable name $CATALINA_BASE to refer the base directory against which most relative paths are resolved. If you have not configured Tomcat for multiple instances by setting a CATALINA_BASE directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME, the directory into which you have installed Tomcat.

Add Default Character Set Filter

Introduction

The HTTP specification is clear that if no character set is specified for media sub-types of the "text" media type, the ISO-8859-1 character set must be used. However, browsers may attempt to auto-detect the character set. This may be exploited by an attacker to perform an XSS attack. Internet Explorer and other browsers have an option to enable this behavior.

This filter prevents the attack by explicitly setting a character set. Unless the provided character set is explicitly overridden by the user the browser will adhere to the explicitly set character set, thus preventing the XSS attack.

Filter Class Name

The filter class name for the Add Default Character Set Filter is org.apache.catalina.filters.AddDefaultCharsetFilter .

Initialisation parameters

The Add Default Character Set Filter supports the following initialization parameters:

Attribute Description
encoding

Name of the character set which should be set, if no other character set was set explicitly by a Servlet. This parameter has two special values default and system. A value of system uses the JVM wide default character set, which is usually set by locale. A value of default will use ISO-8859-1.

CORS Filter

Introduction

This filter is an implementation of W3C's CORS (Cross-Origin Resource Sharing) specification, which is a mechanism that enables cross-origin requests.

The filter works by adding required Access-Control-* headers to HttpServletResponse object. The filter also protects against HTTP response splitting. If request is invalid, or is not permitted, then request is rejected with HTTP status code 403 (Forbidden). A flowchart that demonstrates request processing by this filter is available.

The minimal configuration required to use this filter is:

<filter>
  <filter-name>CorsFilter</filter-name>
  <filter-class>org.apache.catalina.filters.CorsFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>CorsFilter</filter-name>
  <url-pattern>/*</url-pattern>
</filter-mapping>

Filter Class Name

The filter class name for the CORS Filter is org.apache.catalina.filters.CorsFilter.

Initialisation parameters

The CORS Filter supports following initialisation parameters:

Attribute Description
cors.allowed.origins

A list of origins that are allowed to access the resource. A * can be specified to enable access to resource from any origin. Otherwise, a whitelist of comma separated origins can be provided. Eg: http://www.w3.org, https://www.apache.org. Defaults: * (Any origin is allowed to access the resource).

cors.allowed.methods

A comma separated list of HTTP methods that can be used to access the resource, using cross-origin requests. These are the methods which will also be included as part of Access-Control-Allow-Methods header in pre-flight response. Eg: GET, POST. Defaults: GET, POST, HEAD, OPTIONS

cors.allowed.headers

A comma separated list of request headers that can be used when making an actual request. These headers will also be returned as part of Access-Control-Allow-Headers header in a pre-flight response. Eg: Origin,Accept. Defaults: Origin, Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-Headers

cors.exposed.headers

A comma separated list of headers other than simple response headers that browsers are allowed to access. These are the headers which will also be included as part of Access-Control-Expose-Headers header in the pre-flight response. Eg: X-CUSTOM-HEADER-PING,X-CUSTOM-HEADER-PONG. Default: None. Non-simple headers are not exposed by default.

cors.preflight.maxage

The amount of seconds, browser is allowed to cache the result of the pre-flight request. This will be included as part of Access-Control-Max-Age header in the pre-flight response. A negative value will prevent CORS Filter from adding this response header to pre-flight response. Defaults: 1800

cors.support.credentials

A flag that indicates whether the resource supports user credentials. This flag is exposed as part of Access-Control-Allow-Credentials header in a pre-flight response. It helps browser determine whether or not an actual request can be made using credentials. Defaults: true

cors.request.decorate

A flag to control if CORS specific attributes should be added to HttpServletRequest object or not. Defaults: true

Here's an example of a more advanced configuration, that overrides defaults:

<filter>
  <filter-name>CorsFilter</filter-name>
  <filter-class>org.apache.catalina.filters.CorsFilter</filter-class>
  <init-param>
    <param-name>cors.allowed.origins</param-name>
    <param-value>*</param-value>
  </init-param>
  <init-param>
    <param-name>cors.allowed.methods</param-name>
    <param-value>GET,POST,HEAD,OPTIONS,PUT</param-value>
  </init-param>
  <init-param>
    <param-name>cors.allowed.headers</param-name>
    <param-value>Content-Type,X-Requested-With,accept,Origin,Access-Control-Request-Method,Access-Control-Request-Headers</param-value>
  </init-param>
  <init-param>
    <param-name>cors.exposed.headers</param-name>
    <param-value>Access-Control-Allow-Origin,Access-Control-Allow-Credentials</param-value>
  </init-param>
  <init-param>
    <param-name>cors.support.credentials</param-name>
    <param-value>true</param-value>
  </init-param>
  <init-param>
    <param-name>cors.preflight.maxage</param-name>
    <param-value>10</param-value>
  </init-param>
</filter>
<filter-mapping>
  <filter-name>CorsFilter</filter-name>
  <url-pattern>/*</url-pattern>
</filter-mapping>

CORS Filter and HttpServletRequest attributes

CORS Filter adds information about the request, in HttpServletRequest object, for consumption downstream. Following attributes are set, if cors.request.decorate initialisation parameter is true:

  • cors.isCorsRequest: Flag to determine if request is a CORS request.
  • cors.request.origin: The Origin URL, i.e. the URL of the page from where the request originated.
  • cors.request.type: Type of CORS request. Possible values:
    • SIMPLE: A request which is not preceded by a pre-flight request.
    • ACTUAL: A request which is preceded by a pre-flight request.
    • PRE_FLIGHT: A pre-flight request.
    • NOT_CORS: A normal same-origin request.
    • INVALID_CORS: A cross-origin request, which is invalid.
  • cors.request.headers: Request headers sent as Access-Control-Request-Headers header, for a pre-flight request.

CSRF Prevention Filter

Introduction

This filter provides basic CSRF protection for a web application. The filter assumes that it is mapped to /* and that all URLs returned to the client are encoded via a call to HttpServletResponse#encodeRedirectURL(String) or HttpServletResponse#encodeURL(String).

This filter prevents CSRF by generating a nonce and storing it in the session. URLs are also encoded with the same nonce. When the next request is received the nonce in the request is compared to the nonce in the session and only if they are the same is the request allowed to continue.

Filter Class Name

The filter class name for the CSRF Prevention Filter is org.apache.catalina.filters.CsrfPreventionFilter .

Initialisation parameters

The CSRF Prevention Filter supports the following initialisation parameters:

Attribute Description
denyStatus

HTTP response status code that is used when rejecting denied request. The default value is 403.

entryPoints

A comma separated list of URLs that will not be tested for the presence of a valid nonce. They are used to provide a way to navigate back to a protected application after having navigated away from it. Entry points will be limited to HTTP GET requests and should not trigger any security sensitive actions.

nonceCacheSize

The number of previously issued nonces that will be cached on a LRU basis to support parallel requests, limited use of the refresh and back in the browser and similar behaviors that may result in the submission of a previous nonce rather than the current one. If not set, the default value of 5 will be used.

randomClass

The name of the class to use to generate nonces. The class must be an instance of java.util.Random. If not set, the default value of java.security.SecureRandom will be used.

Expires Filter

Introduction

ExpiresFilter is a Java Servlet API port of Apache mod_expires. This filter controls the setting of the Expires HTTP header and the max-age directive of the Cache-Control HTTP header in server responses. The expiration date can set to be relative to either the time the source file was last modified, or to the time of the client access.

These HTTP headers are an instruction to the client about the document's validity and persistence. If cached, the document may be fetched from the cache rather than from the source until this time has passed. After that, the cache copy is considered "expired" and invalid, and a new copy must be obtained from the source.

To modify Cache-Control directives other than max-age (see RFC 2616 section 14.9), you can use other servlet filters or Apache Httpd mod_headers module.

Basic configuration sample

Basic configuration to add 'Expires' and 'Cache-Control: max-age=' headers to images, css and javascript. 

<filter>
 <filter-name>ExpiresFilter</filter-name>
 <filter-class>org.apache.catalina.filters.ExpiresFilter</filter-class>
 <init-param>
    <param-name>ExpiresByType image</param-name>
    <param-value>access plus 10 minutes</param-value>
 </init-param>
 <init-param>
    <param-name>ExpiresByType text/css</param-name>
    <param-value>access plus 10 minutes</param-value>
 </init-param>
 <init-param>
    <param-name>ExpiresByType application/javascript</param-name>
    <param-value>access plus 10 minutes</param-value>
 </init-param>
</filter>
...
<filter-mapping>
 <filter-name>ExpiresFilter</filter-name>
 <url-pattern>/*</url-pattern>
 <dispatcher>REQUEST</dispatcher>
</filter-mapping>

Alternate Syntax

The ExpiresDefault and ExpiresByType directives can also be defined in a more readable syntax of the form: 

<init-param>
 <param-name>ExpiresDefault</param-name>
 <param-value><base> [plus] {<num> <type>}*</param-value>
</init-param>

<init-param>
 <param-name>ExpiresByType type</param-name>
 <param-value><base> [plus] {<num> <type>}*</param-value>
</init-param>

<init-param>
 <param-name>ExpiresByType type;encoding</param-name>
 <param-value><base> [plus] {<num> <type>}*</param-value>
</init-param>

where <base> is one of:

  • access
  • now (equivalent to 'access')
  • modification

The plus keyword is optional. <num> should be an integer value (acceptable to Integer.parseInt()), and <type> is one of:

  • year, years
  • month, months
  • week, weeks
  • day, days
  • hour, hours
  • minute, minutes
  • second, seconds

For example, any of the following directives can be used to make documents expire 1 month after being accessed, by default: 

<init-param>
 <param-name>ExpiresDefault</param-name>
 <param-value>access plus 1 month</param-value>
</init-param>

<init-param>
 <param-name>ExpiresDefault</param-name>
 <param-value>access plus 4 weeks</param-value>
</init-param>

<init-param>
 <param-name>ExpiresDefault</param-name>
 <param-value>access plus 30 days</param-value>
</init-param>

The expiry time can be fine-tuned by adding several '<num> <type>' clauses: 

<init-param>
 <param-name>ExpiresByType text/html</param-name>
 <param-value>access plus 1 month 15 days 2 hours</param-value>
</init-param>

<init-param>
 <param-name>ExpiresByType image/gif</param-name>
 <param-value>modification plus 5 hours 3 minutes</param-value>
</init-param>

Note that if you use a modification date based setting, the Expires header will not be added to content that does not come from a file on disk. This is due to the fact that there is no modification time for such content.

Expiration headers generation eligibility

A response is eligible to be enriched by ExpiresFilter if :

  1. no expiration header is defined (Expires header or the max-age directive of the Cache-Control header),
  2. the response status code is not excluded by the directive ExpiresExcludedResponseStatusCodes,
  3. the Content-Type of the response matches one of the types defined the in ExpiresByType directives or the ExpiresDefault directive is defined.

Note : If Cache-Control header contains other directives than max-age, they are concatenated with the max-age directive that is added by the ExpiresFilter.

Expiration configuration selection

The expiration configuration if elected according to the following algorithm:

  1. ExpiresByType matching the exact content-type returned by HttpServletResponse.getContentType() possibly including the charset (e.g. 'text/xml;charset=UTF-8'),
  2. ExpiresByType matching the content-type without the charset if HttpServletResponse.getContentType() contains a charset (e.g. 'text/xml;charset=UTF-8' -> 'text/xml'),
  3. ExpiresByType matching the major type (e.g. substring before '/') of HttpServletResponse.getContentType() (e.g. 'text/xml;charset=UTF-8' -> 'text'),
  4. ExpiresDefault

Filter Class Name

The filter class name for the Expires Filter is org.apache.catalina.filters.ExpiresFilter .

Initialisation parameters

The Expires Filter supports the following initialisation parameters:

Attribute Description
ExpiresExcludedResponseStatusCodes

This directive defines the http response status codes for which the ExpiresFilter will not generate expiration headers. By default, the 304 status code ("Not modified") is skipped. The value is a comma separated list of http status codes.

This directive is useful to ease usage of ExpiresDefault directive. Indeed, the behavior of 304 Not modified (which does specify a Content-Type header) combined with Expires and Cache-Control:max-age= headers can be unnecessarily tricky to understand.

See sample below the table

ExpiresByType <content-type>

This directive defines the value of the Expires header and the max-age directive of the Cache-Control header generated for documents of the specified type (e.g., text/html). The second argument sets the number of seconds that will be added to a base time to construct the expiration date. The Cache-Control: max-age is calculated by subtracting the request time from the expiration date and expressing the result in seconds.

The base time is either the last modification time of the file, or the time of the client's access to the document. Which should be used is specified by the <code> field; M means that the file's last modification time should be used as the base time, and A means the client's access time should be used. The duration is expressed in seconds. A2592000 stands for access plus 30 days in alternate syntax.

The difference in effect is subtle. If M (modification in alternate syntax) is used, all current copies of the document in all caches will expire at the same time, which can be good for something like a weekly notice that's always found at the same URL. If A ( access or now in alternate syntax) is used, the date of expiration is different for each client; this can be good for image files that don't change very often, particularly for a set of related documents that all refer to the same images (i.e., the images will be accessed repeatedly within a relatively short timespan).

Note: When the content type includes a charset (e.g. 'ExpiresByType text/xml;charset=utf-8'), Tomcat removes blank chars between the ';' and the 'charset' keyword. Due to this, configuration of an expiration with a charset must not include such a space character.

See sample below the table

It overrides, for the specified MIME type only, any expiration date set by the ExpiresDefault directive.

You can also specify the expiration time calculation using an alternate syntax, described earlier in this document.

ExpiresDefault

This directive sets the default algorithm for calculating the expiration time for all documents in the affected realm. It can be overridden on a type-by-type basis by the ExpiresByType directive. See the description of that directive for details about the syntax of the argument, and the "alternate syntax" description as well.

Sample: exclude response status codes 302, 500 and 503

<init-param>
 <param-name>ExpiresExcludedResponseStatusCodes</param-name>
 <param-value>302, 500, 503</param-value>
</init-param>

Sample for ExpiresByType initialization parameter

<init-param>
   <param-name>ExpiresByType text/html</param-name>
   <param-value>access plus 1 month 15   days 2 hours</param-value>
</init-param>

<init-param>
   <!-- 2592000 seconds = 30 days -->
   <param-name>ExpiresByType image/gif</param-name>
   <param-value>A2592000</param-value>
</init-param>

Troubleshooting

To troubleshoot, enable logging on the org.apache.catalina.filters.ExpiresFilter.

Extract of logging.properties 

org.apache.catalina.filters.ExpiresFilter.level = FINE

Sample of initialization log message: 

Mar 26, 2010 2:01:41 PM org.apache.catalina.filters.ExpiresFilter init
FINE: Filter initialized with configuration ExpiresFilter[
 excludedResponseStatusCode=[304],
 default=null,
 byType={
    image=ExpiresConfiguration[startingPoint=ACCESS_TIME, duration=[10 MINUTE]],
    text/css=ExpiresConfiguration[startingPoint=ACCESS_TIME, duration=[10 MINUTE]],
    text/javascript=ExpiresConfiguration[startingPoint=ACCESS_TIME, duration=[10 MINUTE]]}]

Sample of per-request log message where ExpiresFilter adds an expiration date is below. The message is on one line and is wrapped here for better readability. 

Mar 26, 2010 2:09:47 PM org.apache.catalina.filters.ExpiresFilter onBeforeWriteResponseBody
FINE: Request "/tomcat.gif" with response status "200"
 content-type "image/gif", set expiration date 3/26/10 2:19 PM

Sample of per-request log message where ExpiresFilter does not add an expiration date: 

Mar 26, 2010 2:10:27 PM org.apache.catalina.filters.ExpiresFilter onBeforeWriteResponseBody
FINE: Request "/docs/config/manager.html" with response status "200"
 content-type "text/html", no expiration configured

Failed Request Filter

Introduction

This filter triggers parameters parsing in a request and rejects the request if some parameters were skipped during parameter parsing because of parsing errors or request size limitations (such as maxParameterCount attribute in a Connector). This filter can be used to ensure that none parameter values submitted by client are lost.

Note that parameter parsing may consume the body of an HTTP request, so caution is needed if the servlet protected by this filter uses request.getInputStream() or request.getReader() calls. In general the risk of breaking a web application by adding this filter is not so high, because parameter parsing does check content type of the request before consuming the request body.

Note, that for the POST requests to be parsed correctly, a SetCharacterEncodingFilter filter must be configured above this one. See CharacterEncoding page in the FAQ for details.

The request is rejected with HTTP status code 400 (Bad Request).

Filter Class Name

The filter class name for the Failed Request Filter is org.apache.catalina.filters.FailedRequestFilter .

Initialisation parameters

The Failed Request Filter does not support any initialization parameters.

HTTP Header Security Filter

Introduction

There are a number of HTTP headers that can be added to the response to improve the security of the connection. This filter provides a mechanism for adding those headers. Note that security related headers with more complex requirements, like CORS, are implemted as separate Filters.

Filter Class Name

The filter class name for the HTTP Header Security Filter is org.apache.catalina.filters.HttpHeaderSecurityFilter .

Initialisation parameters

The HTTP Header Security Filter supports the following initialization parameters:

Attribute Description
hstsEnabled

Will an HTTP Strict Transport Security (HSTS) header (Strict-Transport-Security) be set on the response for secure requests. Any HSTS header already present will be replaced. See RFC 6797 for further details of HSTS. If not specified, the default value of true will be used.

hstsMaxAgeSeconds

The max age value that should be used in the HSTS header. Negative values will be treated as zero. If not specified, the default value of 0 will be used.

hstsIncludeSubDomains

Should the includeSubDomains parameter be included in the HSTS header. If not specified, the default value of false will be used.

antiClickJackingEnabled

Should the anti click-jacking header (X-Frame-Options) be set on the response. Any anti click-jacking header already present will be replaced. If not specified, the default value of true will be used.

antiClickJackingOption

What value should be used for the ant click-jacking header? Must be one of DENY, SAMEORIGIN, ALLOW-FROM (case-insensitive). If not specified, the default value of DENY will be used.

antiClickJackingUri

IF ALLOW-FROM is used for antiClickJackingOption, what URI should be allowed? If not specified, the default value of an empty string will be used.

blockContentTypeSniffingEnabled

Should the header that blocks content type sniffing (X-Content-Type-Options) be set on every response. If already present, the header will be replaced. If not specified, the default value of true will be used.

Remote Address Filter

Introduction

The Remote Address Filter allows you to compare the IP address of the client that submitted this request against one or more regular expressions, and either allow the request to continue or refuse to process the request from this client.

The syntax for regular expressions is different than that for 'standard' wildcard matching. Tomcat uses the java.util.regex package. Please consult the Java documentation for details of the expressions supported.

Note: There is a caveat when using this filter with IPv6 addresses. Format of the IP address that this valve is processing depends on the API that was used to obtain it. If the address was obtained from Java socket using Inet6Address class, its format will be x:x:x:x:x:x:x:x. That is, the IP address for localhost will be 0:0:0:0:0:0:0:1 instead of the more widely used ::1. Consult your access logs for the actual value.

See also: Remote Host Filter.

Filter Class Name

The filter class name for the Remote Address Filter is org.apache.catalina.filters.RemoteAddrFilter .

Initialisation parameters

The Remote Address Filter supports the following initialisation parameters:

Attribute Description
allow

A regular expression (using java.util.regex) that the remote client's IP address is compared to. If this attribute is specified, the remote address MUST match for this request to be accepted. If this attribute is not specified, all requests will be accepted UNLESS the remote address matches a deny pattern.

deny

A regular expression (using java.util.regex) that the remote client's IP address is compared to. If this attribute is specified, the remote address MUST NOT match for this request to be accepted. If this attribute is not specified, request acceptance is governed solely by the accept attribute.

denyStatus

HTTP response status code that is used when rejecting denied request. The default value is 403. For example, it can be set to the value 404.

Example

To allow access only for the clients connecting from localhost:

    <filter>
      <filter-name>Remote Address Filter</filter-name>
      <filter-class>org.apache.catalina.filters.RemoteAddrFilter</filter-class>
      <init-param>
        <param-name>allow</param-name>
        <param-value>127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1</param-value>
      </init-param>
    </filter>
    <filter-mapping>
      <filter-name>Remote Address Filter</filter-name>
      <url-pattern>/*</url-pattern>
    </filter-mapping>

Remote Host Filter

Introduction

The Remote Host Filter allows you to compare the hostname of the client that submitted this request against one or more regular expressions, and either allow the request to continue or refuse to process the request from this client.

The syntax for regular expressions is different than that for 'standard' wildcard matching. Tomcat uses the java.util.regex package. Please consult the Java documentation for details of the expressions supported.

Note: This filter processes the value returned by method ServletRequest.getRemoteHost(). To allow the method to return proper host names, you have to enable "DNS lookups" feature on a Connector.

See also: Remote Address Filter, HTTP Connector configuration.

Filter Class Name

The filter class name for the Remote Address Filter is org.apache.catalina.filters.RemoteHostFilter .

Initialisation parameters

The Remote Host Filter supports the following initialisation parameters:

Attribute Description
allow

A regular expression (using java.util.regex) that the remote client's hostname is compared to. If this attribute is specified, the remote hostname MUST match for this request to be accepted. If this attribute is not specified, all requests will be accepted UNLESS the remote hostname matches a deny pattern.

deny

A regular expression (using java.util.regex) that the remote client's hostname is compared to. If this attribute is specified, the remote hostname MUST NOT match for this request to be accepted. If this attribute is not specified, request acceptance is governed solely by the accept attribute.

denyStatus

HTTP response status code that is used when rejecting denied request. The default value is 403. For example, it can be set to the value 404.

Remote IP Filter

Introduction

Tomcat port of mod_remoteip, this filter replaces the apparent client remote IP address and hostname for the request with the IP address list presented by a proxy or a load balancer via a request headers (e.g. "X-Forwarded-For").

Another feature of this filter is to replace the apparent scheme (http/https), server port and request.secure with the scheme presented by a proxy or a load balancer via a request header (e.g. "X-Forwarded-Proto").

If used in conjunction with Remote Address/Host filters then this filter should be defined first to ensure that the correct client IP address is presented to the Remote Address/Host filters.

Note: By default this filter has no effect on the values that are written into access log. The original values are restored when request processing leaves the filter and that always happens earlier than access logging. To pass the remote address, remote host, server port and protocol values set by this filter to the access log, they are put into request attributes. Publishing these values here is enabled by default, but AccessLogValve should be explicitly configured to use them. See documentation for requestAttributesEnabled attribute of AccessLogValve.

The names of request attributes that are set by this filter and can be used by access logging are the following:

  • org.apache.catalina.AccessLog.RemoteAddr
  • org.apache.catalina.AccessLog.RemoteHost
  • org.apache.catalina.AccessLog.Protocol
  • org.apache.catalina.AccessLog.ServerPort
  • org.apache.tomcat.remoteAddr

Filter Class Name

The filter class name for the Remote IP Filter is org.apache.catalina.filters.RemoteIpFilter .

Basic configuration to handle 'x-forwarded-for'

The filter will process the x-forwarded-for http header. 

      <filter>
        <filter-name>RemoteIpFilter</filter-name>
        <filter-class>org.apache.catalina.filters.RemoteIpFilter</filter-class>
      </filter>

      <filter-mapping>
        <filter-name>RemoteIpFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher>
      </filter-mapping>

Basic configuration to handle 'x-forwarded-for' and 'x-forwarded-proto'

The filter will process x-forwarded-for and x-forwarded-proto http headers. Expected value for the x-forwarded-proto header in case of SSL connections is https (case insensitive). 

      <filter>
        <filter-name>RemoteIpFilter</filter-name>
        <filter-class>org.apache.catalina.filters.RemoteIpFilter</filter-class>
        <init-param>
          <param-name>protocolHeader</param-name>
          <param-value>x-forwarded-proto</param-value>
        </init-param>
      </filter>

      <filter-mapping>
        <filter-name>RemoteIpFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher>
      </filter-mapping>

Advanced configuration with internal proxies

RemoteIpFilter configuration: 

     <filter>
       <filter-name>RemoteIpFilter</filter-name>
       <filter-class>org.apache.catalina.filters.RemoteIpFilter</filter-class>
       <init-param>
         <param-name>allowedInternalProxies</param-name>
         <param-value>192\.168\.0\.10|192\.168\.0\.11</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpHeader</param-name>
         <param-value>x-forwarded-for</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpProxiesHeader</param-name>
         <param-value>x-forwarded-by</param-value>
       </init-param>
       <init-param>
         <param-name>protocolHeader</param-name>
         <param-value>x-forwarded-proto</param-value>
       </init-param>
     </filter>

Request values:

Property Value Before RemoteIpFilter Value After RemoteIpFilter
request.remoteAddr 192.168.0.10 140.211.11.130
request.header['x-forwarded-for'] 140.211.11.130, 192.168.0.10 null
request.header['x-forwarded-by'] null null
request.header['x-forwarded-proto'] https https
request.scheme http https
request.secure false true
request.serverPort 80 443

Note : x-forwarded-by header is null because only internal proxies has been traversed by the request. x-forwarded-for is null because all the proxies are trusted or internal.

Advanced configuration with trusted proxies

RemoteIpFilter configuration: 

     <filter>
       <filter-name>RemoteIpFilter</filter-name>
       <filter-class>org.apache.catalina.filters.RemoteIpFilter</filter-class>
       <init-param>
         <param-name>allowedInternalProxies</param-name>
         <param-value>192\.168\.0\.10|192\.168\.0\.11</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpHeader</param-name>
         <param-value>x-forwarded-for</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpProxiesHeader</param-name>
         <param-value>x-forwarded-by</param-value>
       </init-param>
       <init-param>
         <param-name>trustedProxies</param-name>
         <param-value>proxy1|proxy2</param-value>
       </init-param>
     </filter>

Request values:

Property Value Before RemoteIpFilter Value After RemoteIpFilter
request.remoteAddr 192.168.0.10 140.211.11.130
request.header['x-forwarded-for'] 140.211.11.130, proxy1, proxy2 null
request.header['x-forwarded-by'] null proxy1, proxy2

Note : proxy1 and proxy2 are both trusted proxies that come in x-forwarded-for header, they both are migrated in x-forwarded-by header. x-forwarded-for is null because all the proxies are trusted or internal.

Advanced configuration with internal and trusted proxies

RemoteIpFilter configuration: 

     <filter>
       <filter-name>RemoteIpFilter</filter-name>
       <filter-class>org.apache.catalina.filters.RemoteIpFilter</filter-class>
       <init-param>
         <param-name>allowedInternalProxies</param-name>
         <param-value>192\.168\.0\.10|192\.168\.0\.11</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpHeader</param-name>
         <param-value>x-forwarded-for</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpProxiesHeader</param-name>
         <param-value>x-forwarded-by</param-value>
       </init-param>
       <init-param>
         <param-name>trustedProxies</param-name>
         <param-value>proxy1|proxy2</param-value>
       </init-param>
     </filter>

Request values:

Property Value Before RemoteIpFilter Value After RemoteIpFilter
request.remoteAddr 192.168.0.10 140.211.11.130
request.header['x-forwarded-for'] 140.211.11.130, proxy1, proxy2, 192.168.0.10 null
request.header['x-forwarded-by'] null proxy1, proxy2

Note : proxy1 and proxy2 are both trusted proxies that come in x-forwarded-for header, they both are migrated in x-forwarded-by header. As 192.168.0.10 is an internal proxy, it does not appear in x-forwarded-by. x-forwarded-for is null because all the proxies are trusted or internal.

Advanced configuration with an untrusted proxy

RemoteIpFilter configuration: 

     <filter>
       <filter-name>RemoteIpFilter</filter-name>
       <filter-class>org.apache.catalina.filters.RemoteIpFilter</filter-class>
       <init-param>
         <param-name>allowedInternalProxies</param-name>
         <param-value>192\.168\.0\.10|192\.168\.0\.11</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpHeader</param-name>
         <param-value>x-forwarded-for</param-value>
       </init-param>
       <init-param>
         <param-name>remoteIpProxiesHeader</param-name>
         <param-value>x-forwarded-by</param-value>
       </init-param>
       <init-param>
         <param-name>trustedProxies</param-name>
         <param-value>proxy1|proxy2</param-value>
       </init-param>
     </filter>

Request values:

Property Value Before RemoteIpFilter Value After RemoteIpFilter
request.remoteAddr 192.168.0.10 untrusted-proxy
request.header['x-forwarded-for'] 140.211.11.130, untrusted-proxy, proxy1 140.211.11.130
request.header['x-forwarded-by'] null proxy1

Note : x-forwarded-by holds the trusted proxy proxy1. x-forwarded-by holds 140.211.11.130 because untrusted-proxy is not trusted and thus, we can not trust that untrusted-proxy is the actual remote ip. request.remoteAddr is untrusted-proxy that is an IP verified by proxy1.

Initialisation parameters

The Remote IP Filter supports the following initialisation parameters:

Attribute Description
remoteIpHeader

Name of the HTTP Header read by this valve that holds the list of traversed IP addresses starting from the requesting client. If not specified, the default of x-forwarded-for is used.

internalProxies

Regular expression (using java.util.regex) that a proxy's IP address must match to be considered an internal proxy. Internal proxies that appear in the remoteIpHeader will be trusted and will not appear in the proxiesHeader value. If not specified the default value of 10\.\d{1,3}\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|169\.254\.\d{1,3}\.\d{1,3}|127\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.1[6-9]{1}\.\d{1,3}\.\d{1,3}|172\.2[0-9]{1}\.\d{1,3}\.\d{1,3}|172\.3[0-1]{1}\.\d{1,3}\.\d{1,3} will be used.

proxiesHeader

Name of the HTTP header created by this valve to hold the list of proxies that have been processed in the incoming remoteIpHeader. If not specified, the default of x-forwarded-by is used.

requestAttributesEnabled

Set to true to set the request attributes used by AccessLog implementations to override the values returned by the request for remote address, remote host, server port and protocol. Request attributes are also used to enable the forwarded remote address to be displayed on the status page of the Manager web application. If not set, the default value of true will be used.

trustedProxies

Regular expression (using java.util.regex) that a proxy's IP address must match to be considered an trusted proxy. Trusted proxies that appear in the remoteIpHeader will be trusted and will appear in the proxiesHeader value. If not specified, no proxies will be trusted.

protocolHeader

Name of the HTTP Header read by this valve that holds the protocol used by the client to connect to the proxy. If not specified, the default of null is used.

portHeader

Name of the HTTP Header read by this valve that holds the port used by the client to connect to the proxy. If not specified, the default of null is used.

protocolHeaderHttpsValue

Value of the protocolHeader to indicate that it is an HTTPS request. If not specified, the default of https is used.

httpServerPort

Value returned by ServletRequest.getServerPort() when the protocolHeader indicates http protocol and no portHeader is present. If not specified, the default of 80 is used.

httpsServerPort

Value returned by ServletRequest.getServerPort() when the protocolHeader indicates https protocol and no portHeader is present. If not specified, the default of 443 is used.

changeLocalPort

If true, the value returned by ServletRequest.getLocalPort() and ServletRequest.getServerPort() is modified by the this filter. If not specified, the default of false is used.

Request Dumper Filter

Introduction

The Request Dumper Filter logs information from the request and response objects and is intended to be used for debugging purposes. When using this Filter, it is recommended that the org.apache.catalina.filter.RequestDumperFilter logger is directed to a dedicated file and that the org.apache.juli.VerbatimFormmater is used.

WARNING: Using this filter has side-effects. The output from this filter includes any parameters included with the request. The parameters will be decoded using the default platform encoding. Any subsequent calls to request.setCharacterEncoding() within the web application will have no effect.

Filter Class Name

The filter class name for the Request Dumper Filter is org.apache.catalina.filters.RequestDumperFilter .

Initialisation parameters

The Request Dumper Filter does not support any initialization parameters.

Sample Configuration

The following entries in a web application's web.xml would enable the Request Dumper filter for all requests for that web application. If the entries were added to CATALINA_BASE/conf/web.xml, the Request Dumper Filter would be enabled for all web applications.

<filter>
    <filter-name>requestdumper</filter-name>
    <filter-class>
        org.apache.catalina.filters.RequestDumperFilter
    </filter-class>
</filter>
<filter-mapping>
    <filter-name>requestdumper</filter-name>
    <url-pattern>*</url-pattern>
</filter-mapping>

The following entries in CATALINA_BASE/conf/logging.properties would create a separate log file for the Request Dumper Filter output.

# To this configuration below, 1request-dumper.org.apache.juli.FileHandler
# also needs to be added to the handlers property near the top of the file
1request-dumper.org.apache.juli.FileHandler.level = INFO
1request-dumper.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
1request-dumper.org.apache.juli.FileHandler.prefix = request-dumper.
1request-dumper.org.apache.juli.FileHandler.formatter = org.apache.juli.VerbatimFormatter
org.apache.catalina.filters.RequestDumperFilter.level = INFO
org.apache.catalina.filters.RequestDumperFilter.handlers = \
  1request-dumper.org.apache.juli.FileHandler

Set Character Encoding Filter

Introduction

User agents don't always include character encoding information in requests. Depending on the how the request is processed, usually the default encoding of ISO-8859-1 is used. This is not always desirable. This filter provides options for setting that encoding or forcing it to a particular value. Essentially this filter calls ServletRequest.setCharacterEncoding() method.

Effectively the value set by this filter is used when parsing parameters in a POST request, if parameter parsing occurs later than this filter. Thus the order of filter mappings is important. Note that the encoding for GET requests is not set here, but on a Connector. See CharacterEncoding page in the FAQ for details.

Filter Class Name

The filter class name for the Set Character Encoding Filter is org.apache.catalina.filters.SetCharacterEncodingFilter .

Initialisation parameters

The Set Character Encoding Filter supports the following initialization parameters:

Attribute Description
encoding

Name of the character encoding which should be set.

ignore

Determines if any character encoding specified by the user agent is ignored. If this attribute is true, any value provided by the user agent is ignored. If false, the encoding is only set if the user agent did not specify an encoding. The default value is false.

WebDAV Fix Filter

Introduction

Microsoft operating systems have two WebDAV clients. One is used with port 80, the other is used for all other ports. The implementation used with port 80 does not adhere to the WebDAV specification and fails when trying to communicate with the Tomcat WebDAV Servlet. This Filter provides a fix for this by forcing the use of the WebDAV implementation that works, even when connecting via port 80.

Filter Class Name

The filter class name for the WebDAV Fix Filter is org.apache.catalina.filters.WebdavFixFilter .

Initialisation parameters

The WebDAV Fix Filter does not support any initialization parameters.

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