From: Luca Toscano Strict
option. Due to legacy modules, applications or
custom user-agents which must be deprecated the Unsafe
- option has been added to revert to the legacy behaviors. These rules
- are applied prior to request processing, so must be configured at the
- global or default (first) matching virtual host section, by IP/port
- interface (and not by name) to be honored.
Prior to the introduction of this directive, the Apache HTTP Server
- request message parsers were tolerant of a number of forms of input
- which did not conform to the protocol.
- RFC 7230 §9.4 Request Splitting and
- §9.5 Response Smuggling call out only two of the potential
- risks of accepting non-conformant request messages, while
- RFC 7230 §3.5 "Message Parsing Robustness" identify the
- risks of accepting obscure whitespace and request message formatting.
- As of the introduction of this directive, all grammar rules of the
- specification are enforced in the default Strict
operating
- mode, and the strict whitespace suggested by section 3.5 is enforced
- and cannot be relaxed.
Users are strongly cautioned against toggling the Unsafe
- mode of operation, particularly on outward-facing, publicly accessible
- server deployments. If an interface is required for faulty monitoring
- or other custom service consumers running on an intranet, users should
- toggle the Unsafe option only on a specific virtual host configured
- to service their internal private network.
Reviewing the messages logged to the debug
level,
+ option has been added to revert to the legacy behaviors.
These rules are applied prior to request processing, + so must be configured at the global or default (first) matching + virtual host section, by IP/port interface (and not by name) + to be honored.
+ +The directive accepts three parameters from the following list + of choices, applying the default to the ones not specified:
+ +Prior to the introduction of this directive, the Apache HTTP Server
+ request message parsers were tolerant of a number of forms of input
+ which did not conform to the protocol.
+ RFC 7230 §9.4 Request Splitting and
+ §9.5 Response Smuggling call out only two of the potential
+ risks of accepting non-conformant request messages, while
+ RFC 7230 §3.5 "Message Parsing Robustness" identify the
+ risks of accepting obscure whitespace and request message formatting.
+ As of the introduction of this directive, all grammar rules of the
+ specification are enforced in the default Strict
operating
+ mode, and the strict whitespace suggested by section 3.5 is enforced
+ and cannot be relaxed.
Users are strongly cautioned against toggling the Unsafe
+ mode of operation, particularly on outward-facing, publicly accessible
+ server deployments. If an interface is required for faulty monitoring
+ or other custom service consumers running on an intranet, users should
+ toggle the Unsafe option only on a specific virtual host configured
+ to service their internal private network.
RFC 7231 §4.1 "Request Methods" "Overview" requires that
+ origin servers shall respond with a HTTP 501 status code when an
+ unsupported method is encountered in the request line.
+ This already happens when the LenientMethods
option is used,
+ but administrators may wish to toggle the RegisteredMethods
+ option and register any non-standard methods using the
+ Unsafe
+ option has been toggled.
The RegisteredMethods
option should not
+ be toggled for forward proxy hosts, as the methods supported by the
+ origin servers are unknown to the proxy server.
RFC 2616 §19.6 "Compatibility With Previous Versions" had
+ encouraged HTTP servers to support legacy HTTP/0.9 requests. RFC 7230
+ supersedes this with "The expectation to support HTTP/0.9 requests has
+ been removed" and offers additional comments in
+ RFC 7230 Appendix A. The Require1.0
option allows
+ the user to remove support of the default Allow0.9
option's
+ behavior.
Reviewing the messages logged to the
+ debug
level,
can help identify such faulty requests along with their origin.
Users should pay particular attention to the 400 responses in the access
log for invalid requests which were unexpectedly rejected.
RFC 7231 §4.1 "Request Methods" "Overview" requires that
- origin servers shall respond with an error when an unsupported method
- is encountered in the request line. This already happens when the
- LenientMethods
option is used, but administrators may wish
- to toggle the RegisteredMethods
option and register any
- non-standard methods using the Unsafe
option has been toggled.
- The RegisteredMethods
option should not
- be toggled for forward proxy hosts, as the methods supported by the
- origin servers are unknown to the proxy server.
RFC 2616 §19.6 "Compatibility With Previous Versions" had
- encouraged HTTP servers to support legacy HTTP/0.9 requests. RFC 7230
- supersedes this with "The expectation to support HTTP/0.9 requests has
- been removed" and offers additional comments in
- RFC 7230 Appendix A. The Require1.0
option allows
- the user to remove support of the default Allow0.9
option's
- behavior.