Reference

Server Request Filters

New Feature

Available since version 2.11.1

Server request filters allow you to modify the initial state of a generated ServerRequest instance as returned from Laminas\Diactoros\ServerRequestFactory::fromGlobals(). Common use cases include:

  • Generating and injecting a request ID.
  • Modifying the request URI based on headers provided (e.g., based on the X-Forwarded-Host or X-Forwarded-Proto headers).

FilerServerRequestInterface

A request filter implements Laminas\Diactoros\ServerRequestFilter\FilterServerRequestInterface:

namespace Laminas\Diactoros\ServerRequestFilter;

use Psr\Http\Message\ServerRequestInterface;

interface FilterServerRequestInterface
{
    public function __invoke(ServerRequestInterface $request): ServerRequestInterface;
}

Implementations

We provide the following implementations:

  • DoNotFilter: returns the provided $request verbatim.
  • FilterUsingXForwardedHeaders: if the originating request comes from a trusted proxy, examines the X-Forwarded-* headers, and returns the request instance with a URI instance that reflects those headers.

DoNotFilter

This filter returns the $request argument back verbatim when invoked.

FilterUsingXForwardedHeaders

Servers behind a reverse proxy need mechanisms to determine the original URL requested. As such, reverse proxies have provided a number of mechanisms for delivering this information, with the use of X-Forwarded-* headers being the most prevalant. These include:

  • X-Forwarded-Host: the original Host header value.
  • X-Forwarded-Port: the original port included in the Host header value.
  • X-Forwarded-Proto: the original URI scheme used to make the request (e.g., "http" or "https").

Laminas\Diactoros\ServerRequestFilter\FilterUsingXForwardedHeaders provides named constructors for choosing whether to never trust proxies, always trust proxies, or choose wich proxies and/or headers to trust in order to modify the URI composed in the request instance to match the original request. These named constructors are:

  • FilterUsingXForwardedHeadersFactory::trustProxies(string[] $proxyCIDRList, string[] $trustedHeaders = FilterUsingXForwardedHeaders::X_FORWARDED_HEADERS): void: when this method is called, only requests originating from the trusted proxy/ies will be considered, as well as only the headers specified. Proxies may be specified by IP address, or using CIDR notation for subnets; both IPv4 and IPv6 are accepted. The special string "*" will be translated to two entries, 0.0.0.0/0 and ::/0.
  • FilterUsingXForwardedHeaders::trustAny(): void: when this method is called, the filter will trust requests from any origin, and use any of the above headers to modify the URI instance. It is functionally equivalent to FilterUsingXForwardedHeaders::trustProxies(['*']).
  • FilterUsingXForwardedHeaders::trustReservedSubnets(): void: when this method is called, the filter will trust requests made from reserved, private subnets. It is functionally equivalent to FilterUsingXForwardedHeaders::trustProxies() with the following elements in the $proxyCIDRList:
  • 10.0.0.0/8
  • 127.0.0.0/8
  • 172.16.0.0/12
  • 192.168.0.0/16
  • ::1/128 (IPv6 localhost)
  • fc00::/7 (IPv6 private networks)
  • fe80::/10 (IPv6 local-link addresses)

Internally, the filter checks the REMOTE_ADDR server parameter (as retrieved from getServerParams()) and compares it against each proxy listed; the first to match indicates trust.

Constants

The FilterUsingXForwardedHeaders defines the following constants for use in specifying various headers:

  • HEADER_HOST: corresponds to X-Forwarded-Host.
  • HEADER_PORT: corresponds to X-Forwarded-Port.
  • HEADER_PROTO: corresponds to X-Forwarded-Proto.

Example usage

Trusting all X-Forwarded-* headers from any source:

$filter = FilterUsingXForwardedHeaders::trustAny();

Trusting only the X-Forwarded-Host header from any source:

$filter = FilterUsingXForwardedHeaders::trustProxies('0.0.0.0/0', [FilterUsingXForwardedHeaders::HEADER_HOST]);

Trusting the X-Forwarded-Host and X-Forwarded-Proto headers from a single Class C subnet:

$filter = FilterUsingXForwardedHeaders::trustProxies(
    '192.168.1.0/24',
    [FilterUsingXForwardedHeaders::HEADER_HOST, FilterUsingXForwardedHeaders::HEADER_PROTO]
);

Trusting the X-Forwarded-Host header from either a Class A or a Class C subnet:

$filter = FilterUsingXForwardedHeaders::trustProxies(
    ['10.1.1.0/16', '192.168.1.0/24'],
    [FilterUsingXForwardedHeaders::HEADER_HOST, FilterUsingXForwardedHeaders::HEADER_PROTO]
);

Trusting any X-Forwarded-* header from any private subnet:

$filter = FilterUsingXForwardedHeaders::trustReservedSubnets();