Special HTTP headers

Wordlists:

https://github.com/danielmiessler/SecLists/tree/master/Miscellaneous/web/http-request-headers

Headers to Change Location

Rewrite IP source:

X-Originating-IP: 127.0.0.1
X-Forwarded-For: 127.0.0.1
X-Forwarded: 127.0.0.1
Forwarded-For: 127.0.0.1
X-Remote-IP: 127.0.0.1
X-Remote-Addr: 127.0.0.1
X-ProxyUser-Ip: 127.0.0.1
X-Original-URL: 127.0.0.1
Client-IP: 127.0.0.1
True-Client-IP: 127.0.0.1
Cluster-Client-IP: 127.0.0.1
X-ProxyUser-Ip: 127.0.0.1
Connection: close, X-Forwarded-For Check hop-by-hop headers

Rewrite location:

X-Original-URL: /admin/console
X-Rewrite-URL: /admin/console

Hop-by-Hop headers

A hop-by-hop header is a header which is designed to be processed and consumed by the proxy currently handling the request, as opposed to an end-to-end header.

Connection: close, X-Forwarded-For

{% page-ref page="../../pentesting-web/abusing-hop-by-hop-headers.md" %}

HTTP Request Smuggling

Content-Length: 30
Transfer-Encoding: chunked

{% page-ref page="../../pentesting-web/http-request-smuggling.md" %}

Cache Headers

X-Cache in the response may have the value miss when the request wasn't cached and the value hit when it is cached
Cache-Control indicates if a resource is being cached and when will be the next time the resource will be cached again: Cache-Control: public, max-age=1800
Vary is often used in the response to indicate additional headers that are treated as part of the cache key even if they are normally unkeyed.
Age defines the times in seconds the object has been in the proxy cache.

{% page-ref page="../../pentesting-web/cache-deception.md" %}

Conditionals

Requests using these headers: If-Modified-Since and If-Unmodified-Since will be responded with data only if the response headerLast-Modified contains a different time.
Conditional requests using If-Match and If-None-Match use an Etag value so the web server will send the content of the response if the data Etag has changed. The Etag is taken from the HTTP response.
- The Etag value is usually calculated based on the content of the response. For example, ETag: W/"37-eL2g8DEyqntYlaLp5XLInBWsjWI" indicates that the Etag is the Sha1 of 37 bytes.

Range requests

Accept-Ranges: Indicates if the server supports range requests, and if so in which unit the range can be expressed.
Range: Indicates the part of a document that the server should return.
If-Range: Creates a conditional range request that is only fulfilled if the given etag or date matches the remote resource. Used to prevent downloading two ranges from incompatible version of the resource.
Content-Range: Indicates where in a full body message a partial message belongs.

Message body information

Content-Length: The size of the resource, in decimal number of bytes.
Content-Type: Indicates the media type of the resource
Content-Encoding: Used to specify the compression algorithm.
Content-Language: Describes the human language(s) intended for the audience, so that it allows a user to differentiate according to the users' own preferred language.
Content-Location: Indicates an alternate location for the returned data.

From a pentest point of view this information is usually "useless", but if the resource is protected by a 401 or 403 and you can find some way to get this info, this could be interesting.
For example a combination of Range and Etag in a HEAD request can leak the content of the page via HEAD requests:

A request with the header Range: bytes=20-20 and with a response containing ETag: W/"1-eoGvPlkaxxP4HqHv6T3PNhV9g3Y" is leaking that the SHA1 of the byte 20 is ETag: eoGvPlkaxxP4HqHv6T3PNhV9g3Y

Resources

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers

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