# Server Side Access Authorization Module

This module is the server side interface to Access Authorization (AA) package. It contains code only for server.

Important to know about memory allocation:

Routines in this module use dynamic allocation, but free automatically all the memory reserved by them.

Therefore the caller never has to (and never should) `free()` any object returned by these functions.

Therefore also all the strings returned by this package are only valid until the next call to the same function is made. This approach is selected, because of the nature of access authorization: no string returned by the package needs to be valid longer than until the next call.

This also makes it easy to plug the AA package in: you don't have to ponder whether to `free()` something here or is it done somewhere else (because it is always done somewhere else).

The strings that the package needs to store are copied so the original strings given as parameters to AA functions may be freed or modified with no side effects.

Also note: The AA package does not `free()` anything else than what it has itself allocated.

    #ifndef HTAASERV_H
    #define HTAASERV_H

    #include <stdio.h>		/* FILE			*/
    #include "HTUtils.h"		/* BOOL, PARAMS, ARGS	*/
    #include "HTRules.h"		/* This module interacts with rule system */
    #include "HTAAUtil.h"		/* Common parts of AA	*/
    #include "HTAuth.h"		/* Authentication	*/

    #ifdef SHORT_NAMES
    #define HTAAstMs	HTAA_statusMessage
    #define HTAAchAu	HTAA_checkAuthorization
    #define HTAAcoAH	HTAA_composeAuthHeaders
    #define HTAAsLog	HTAA_startLogging
    #endif /*SHORT_NAMES*/

## Check Access Authorization

`HTAA_checkAuthorization()` is the main access authorization function.

    /* PUBLIC					      HTAA_checkAuthorization()
    **		CHECK IF USER IS AUTHORIZED TO ACCESS A FILE
    ** ON ENTRY:
    **	req	data structure representing the request.
    **
    ** ON EXIT:
    **	returns	status codes uniform with those of HTTP:
    **	  200 OK	   if file access is ok.
    **	  401 Unauthorized if user is not authorized to
    **			   access the file.
    **	  403 Forbidden	   if there is no entry for the
    **			   requested file in the ACL.
    **
    ** NOTE:
    **	This function does not check whether the file
    **	exists or not -- so the status  404 Not found
    **	must be returned from somewhere else (this is
    **	to avoid unnecessary overhead of opening the
    **	file twice).
    **
    */
    PUBLIC int HTAA_checkAuthorization PARAMS((HTRequest * req));

## Compose Status Line Message

    /* SERVER PUBLIC					HTAA_statusMessage()
    **		RETURN A STRING EXPLAINING ACCESS
    **		AUTHORIZATION FAILURE
    **		(Can be used in server reply status line
    **		 with 401/403 replies.)
    ** ON ENTRY:
    **	req	failing request.
    ** ON EXIT:
    **	returns	a string containing the error message
    **		corresponding to internal HTAAFailReason.
    */
    PUBLIC char *HTAA_statusMessage PARAMS((HTRequest * req));

## Compose "Authenticate:" Header Lines for Server Reply

    /* SERVER PUBLIC				    HTAA_composeAuthHeaders()
    **		COMPOSE WWW-Authenticate: HEADER LINES
    **		INDICATING VALID AUTHENTICATION SCHEMES
    **		FOR THE REQUESTED DOCUMENT
    ** ON ENTRY:
    **	req	request.
    **
    ** ON EXIT:
    **	returns	a buffer containing all the WWW-Authenticate:
    **		fields including CRLFs (this buffer is auto-freed).
    **		NULL, if authentication won't help in accessing
    **		the requested document.
    */
    PUBLIC char *HTAA_composeAuthHeaders PARAMS((HTRequest * req));

## Start Access Authorization Logging

    /* PUBLIC						HTAA_startLogging()
    **		START UP ACCESS AUTHORIZATION LOGGING
    ** ON ENTRY:
    **	fp	is the open log file.
    **
    */
    PUBLIC void HTAA_startLogging PARAMS((FILE * fp));

    #endif	/* NOT HTAASERV_H */

End of file HTAAServ.h.