/*	$OpenBSD: read_service_key.c,v 1.6 1998/02/25 15:51:35 art Exp $	*/
/* $KTH: read_service_key.c,v 1.8 1997/03/23 03:53:16 joda Exp $ */

/*
 * This source code is no longer held under any constraint of USA
 * `cryptographic laws' since it was exported legally.  The cryptographic
 * functions were removed from the code and a "Bones" distribution was
 * made.  A Commodity Jurisdiction Request #012-94 was filed with the
 * USA State Department, who handed it to the Commerce department.  The
 * code was determined to fall under General License GTDA under ECCN 5D96G,
 * and hence exportable.  The cryptographic interfaces were re-added by Eric
 * Young, and then KTH proceeded to maintain the code in the free world.
 *
 */

/* 
 *  Copyright (C) 1989 by the Massachusetts Institute of Technology
 *
 *  Export of this software from the United States of America is assumed
 *  to require a specific license from the United States Government.
 *  It is the responsibility of any person or organization contemplating
 *  export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 *
 */

#include "krb_locl.h"

/*
 * The private keys for servers on a given host are stored in a
 * "srvtab" file (typically "/etc/srvtab").  This routine extracts
 * a given server's key from the file.
 *
 * read_service_key() takes the server's name ("service"), "instance",
 * and "realm" and a key version number "kvno", and looks in the given
 * "file" for the corresponding entry, and if found, returns the entry's
 * key field in "key".
 * 
 * If "instance" contains the string "*", then it will match
 * any instance, and the chosen instance will be copied to that
 * string.  For this reason it is important that the there is enough
 * space beyond the "*" to receive the entry.
 *
 * If "kvno" is 0, it is treated as a wild card and the first
 * matching entry regardless of the "vno" field is returned.
 *
 * This routine returns KSUCCESS on success, otherwise KFAILURE.
 *
 * The format of each "srvtab" entry is as follows:
 *
 * Size			Variable		Field in file
 * ----			--------		-------------
 * string		serv			server name
 * string		inst			server instance
 * string		realm			server realm
 * 1 byte		vno			server key version #
 * 8 bytes		key			server's key
 * ...			...			...
 */


int
read_service_key(char *service,	/* Service Name */
		 char *instance, /* Instance name or "*" */
		 char *realm,	/* Realm */
		 int kvno,	/* Key version number */
		 char *file,	/* Filename */
		 char *key)	/* Pointer to key to be filled in */
{
    char serv[SNAME_SZ];
    char inst[INST_SZ];
    char rlm[REALM_SZ];
    unsigned char vno;          /* Key version number */
    int wcard;

    int stab;

    if ((stab = open(file, O_RDONLY, 0)) < 0)
        return KFAILURE;

    if (instance == NULL)
	return KFAILURE;

    wcard = (instance[0] == '*') && (instance[1] == '\0');

    while (getst(stab, serv, SNAME_SZ) > 0) { /* Read sname */
        getst(stab, inst, INST_SZ); /* Instance */
        getst(stab, rlm, REALM_SZ); /* Realm */
        /* Vers number */
        if (read(stab, &vno, 1) != 1) {
	    close(stab);
            return KFAILURE;
	}
        /* Key */
        if (read(stab, key, 8) != 8) {
	    close(stab);
            return KFAILURE;
	}
        /* Is this the right service */
        if (service != NULL && strcmp(serv, service))
            continue;
        /* How about instance */
        if (wcard == '\0' && strcmp(inst,instance))
            continue;
        if (wcard != 0) {
            strncpy(instance, inst, INST_SZ);
	    instance[INST_SZ - 1] = '\0';
	}
        /* Is this the right realm */
        if (realm != NULL && strcmp(rlm, realm)) 
	    continue;

        /* How about the key version number */
        if (kvno && kvno != (int) vno)
            continue;

        close(stab);
        return KSUCCESS;
    }

    /* Can't find the requested service */
    close(stab);
    return(KFAILURE);
}