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.

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

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

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>

The above configuration enables the filter but does not relax the cross-origin policy. As a minimum, you will need to add a cors.allowed.origins initialisation parameter as described below to enable cross-origin requests. Depending on your requirements, you may need to provide additional configuration.

An instance of this filter can only implement one policy. If you want to apply different policies (e.g. different allowed origins) to different URLs or sets of URLs within your web application you will need to configure a separate instance of this filter for each policy you wish to configure.

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

The CORS Filter supports following initialisation parameters:

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>https://www.apache.org</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 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.

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.

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

The CSRF Prevention Filter supports the following initialisation parameters:

This filter provides basic CSRF protection for REST APIs. The CSRF protection is applied only for modifying HTTP requests (different from GET, HEAD, OPTIONS) to protected resources. It is based on a custom header X-CSRF-Token that provides a valid nonce.

CSRF protection mechanism for REST APIs consists of the following steps:

• Client asks for a valid nonce. This is performed with a non-modifying "Fetch" request to protected resource.
• Server responds with a valid nonce mapped to the current user session.
• Client provides this nonce in the subsequent modifying requests in the frame of the same user session.
• Server rejects all modifying requests to protected resources that do not contain a valid nonce.

On the server side

• All CSRF protected REST APIs should be protected with an authentication mechanism.
• Protect modifying REST APIs with this filter.
• Provide at least one non-modifying operation.

<filter>
  <filter-name>RestCSRF</filter-name>
  <filter-class>org.apache.catalina.filters.RestCsrfPreventionFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>RestCSRF</filter-name>
  <!-- Modifying operations -->
  <url-pattern>/resources/removeResource</url-pattern>
  <url-pattern>/resources/addResource</url-pattern>
  <!-- Non-modifying operations -->
  <url-pattern>/resources/listResources</url-pattern>
</filter-mapping>

On the client side

• Make a non-modifying "Fetch" request in order to obtain a valid nonce. This can be done with sending additional header X-CSRF-Token: Fetch
• Cache the returned session id and nonce in order to provide them in the subsequent modifying requests to protected resources.
• Modifying requests can be denied and header X-CSRF-Token: Required will be returned in case of invalid or missing nonce, expired session or in case the session id is changed by the server.

Client Request:
GET /rest/resources/listResources HTTP/1.1
X-CSRF-Token: Fetch
Authorization: Basic ...
Host: localhost:8080
...

Server Response:
HTTP/1.1 200 OK
Set-Cookie: JSESSIONID=...; Path=/rest; HttpOnly
X-CSRF-Token: ...
...

Client Request:
POST /rest/resources/addResource HTTP/1.1
Cookie: JSESSIONID=...
X-CSRF-Token: ...
Authorization: Basic ...
Host: localhost:8080
...

Server Response:
HTTP/1.1 200 OK
...

When the client is not able to insert custom headers in its calls to REST APIs there is additional capability to configure URLs for which a valid nonce will be accepted as a request parameter.

Note: If there is a X-CSRF-Token header, it will be taken with preference over any parameter with the same name in the request. Request parameters cannot be used to fetch new nonce, only header can be used to request a new nonce.

<filter>
  <filter-name>RestCSRF</filter-name>
  <filter-class>org.apache.catalina.filters.RestCsrfPreventionFilter</filter-class>
  <init-param>
    <param-name>pathsAcceptingParams</param-name>
    <param-value>/resources/removeResource,/resources/addResource</param-value>
  </init-param>
</filter>
<filter-mapping>
  <filter-name>RestCSRF</filter-name>
  <url-pattern>/resources/*</url-pattern>
</filter-mapping>

The filter class name for the CSRF Prevention Filter for REST APIs is org.apache.catalina.filters.RestCsrfPreventionFilter .

The CSRF Prevention Filter for REST APIs supports the following initialisation parameters:

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 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 text/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>

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.

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.

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

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

The Expires Filter supports the following initialisation parameters:

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>

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

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).

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

The Failed Request Filter does not support any initialization parameters.

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 implemented as separate Filters.

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

The HTTP Header Security Filter supports the following initialization parameters:

The Rate Limit Filter can help mitigate Denial of Service (DoS) and Brute Force attacks by limiting the number of a requests that are allowed from a single IP address within a time window (also referred to as a time bucket), e.g. 300 Requests per 60 seconds.

The filter works by incrementing a counter in a time bucket for each IP address, and if the counter exceeds the allowed limit then further requests from that IP are dropped with a "429 Too many requests" response until the bucket time ends and a new bucket starts.

The RateLimiter implementation can be set via the rateLimitClassName init param. The default implementation, org.apache.catalina.util.FastRateLimiter, is optimized for efficiency and low overhead so it converts some configured values to more efficient values. For example, a configuration of a 60 seconds time bucket is converted to 65.536 seconds. That allows for very fast bucket calculation using bit shift arithmetic. In order to remain true to the user intent, the configured number of requests is then multiplied by the same ratio, so a configuration of 100 Requests per 60 seconds, has the real values of 109 Requests per 65 seconds. An alternative implementation, org.apache.catalina.util.ExactRateLimiter, is intended to provide a less efficient but more accurate control, whose effective duration in seconds and number of requests allowed are consist with the configured values. You can specify a different class as long as it implements the org.apache.catalina.util.RateLimiter interface.

It is common to set up different restrictions for different URIs. For example, a login page or authentication script is typically expected to get far less requests than the rest of the application, so you can add a filter definition that would allow only 5 requests per 15 seconds and map those URIs to it.

You can set enforce to false to disable the termination of requests that exceed the allowed limit. Then your application code can inspect the Request Attribute org.apache.catalina.filters.RateLimitFilter.Count and decide how to handle the request based on other information that it has, e.g. allow more requests to certain users based on roles, etc.

exposeHeaders enables the output of the rate limiter configuration and state via an HTTP response header as per RateLimit header fields for HTTP (draft).

WARNING: if Tomcat is behind a reverse proxy then you must make sure that the Rate Limit Filter sees the client IP address, so if for example you are using the Remote IP Filter, then the filter mapping for the Rate Limit Filter must come after the mapping of the Remote IP Filter to ensure that each request has its IP address resolved before the Rate Limit Filter is applied. Failure to do so will count requests from different IPs in the same bucket and will result in a self inflicted DoS attack.

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

The Rate Limit Filter supports the following initialisation parameters:

Set the site rate limit to 300 Requests per minute (default):

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

    <filter-mapping>
        <filter-name>RateLimitFilter Global</filter-name>
        <url-pattern>*</url-pattern>
    </filter-mapping>

Set the /auth/* scripts rate limit to 20 Requests per minute:

    <filter>
        <filter-name>RateLimitFilter Login</filter-name>
        <filter-class>org.apache.catalina.filters.RateLimitFilter</filter-class>
        <init-param>
            <param-name>bucketRequests</param-name>
            <param-value>20</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>RateLimitFilter Login</filter-name>
        <url-pattern>/auth/*</url-pattern>
    </filter-mapping>

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.

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

The Remote Address Filter supports the following initialisation parameters:

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>

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.

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

The Remote Host Filter supports the following initialisation parameters:

The Remote CIDR Filter allows you to compare the IP address of the client that submitted this request against one or more netmasks following the CIDR notation, and either allow the request to continue or refuse to process the request from this client. IPv4 and IPv6 are both fully supported.

This filter mimics Apache httpd's Order, Allow from and Deny from directives, with the following limitations:

• Order will always be allow, deny;
• dotted quad notations for netmasks are not supported (that is, you cannot write 192.168.1.0/255.255.255.0, you must write 192.168.1.0/24;
• shortcuts, like 10.10., which is equivalent to 10.10.0.0/16, are not supported;
• as the filter name says, this is a CIDR only filter, therefore subdomain notations like .mydomain.com are not supported either.

Some more features of this filter are:

• if you omit the CIDR prefix, this filter becomes a single IP filter;
• unlike the Remote Host Filter, it can handle IPv6 addresses in condensed form (::1, fe80::/71, etc).

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

The Remote CIDR Filter supports the following initialisation parameters:

To allow access only for the clients connecting from localhost and from local network 192.68.0.*:

      <filter>
        <filter-name>Remote CIDR Filter</filter-name>
        <filter-class>org.apache.catalina.filters.RemoteCIDRFilter</filter-class>
        <init-param>
          <param-name>allow</param-name>
          <param-value>127.0.0.1, ::1, 192.68.0.0/24</param-value>
        </init-param>
      </filter>

      <filter-mapping>
        <filter-name>Remote CIDR Filter</filter-name>
        <url-pattern>/*</url-pattern>
      </filter-mapping>

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

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

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>

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>

RemoteIpFilter configuration:

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

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

Request values:

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.

RemoteIpFilter configuration:

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

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

Request values:

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.

RemoteIpFilter configuration:

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

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

Request values:

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.

RemoteIpFilter configuration:

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

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

Request values:

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 cannot trust that untrusted-proxy is the actual remote ip. request.remoteAddr is untrusted-proxy that is an IP verified by proxy1.

The Remote IP Filter supports the following initialisation parameters:

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.VerbatimFormatter 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.

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

The Request Dumper Filter does not support any initialization parameters.

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.encoding = UTF-8
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

The Session Initializer Filter initializes the jakarta.servlet.http.HttpSession before the Request is processed. This is required for JSR-356 compliant WebSocket implementations, if the HttpSession is needed during the HandShake phase.

The Java API for WebSocket does not mandate that an HttpSession would be initialized upon request, and thus jakarta.servlet.http.HttpServletRequest's getSession() returns null if the HttpSession was not initialized in advance.

This filter solves that problem by initializing the HttpSession for any HttpServletRequest that matches its url-pattern.

The filter class name for the Session Initializer Filter is org.apache.catalina.filters.SessionInitializerFilter.

The Session Initializer Filter does not support any initialization parameters.

The following entries in the Web Application Deployment Descriptor, web.xml, would enable the Session Initializer Filter for requests that match the given URL pattern (in this example, "/ws/*").

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

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.

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

The Set Character Encoding Filter supports the following initialization parameters:

This filter was written for Windows NT era Microsoft operating systems that shipped with WebDAV clients that were not compliant with the RFC. This filter is no longer required for current WebDAV clients provided by current (Windows 10 / Windows Server 2012 onwards) Windows operating systems. It has been deprecated and will be removed in Tomcat 11 onwards.

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

The WebDAV Fix Filter does not support any initialization parameters.