/*
 * kadmin/v5server/keytab.c
 *
 * Copyright 1995 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   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.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * 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 <string.h>

#include "k5-int.h"
#include "kdb_kt.h"

static int
is_xrealm_tgt(krb5_context, krb5_const_principal);

krb5_error_code krb5_ktkdb_close (krb5_context, krb5_keytab);

krb5_error_code krb5_ktkdb_get_entry (krb5_context, krb5_keytab, krb5_const_principal,
		   krb5_kvno, krb5_enctype, krb5_keytab_entry *);

static krb5_error_code
krb5_ktkdb_get_name(krb5_context context, krb5_keytab keytab,
		    char *name, unsigned int namelen)
{
    if (namelen < sizeof("KDB:"))
	return KRB5_KT_NAME_TOOLONG;
    strcpy(name, "KDB:");
    return 0;
}

krb5_kt_ops krb5_kt_kdb_ops = {
    0,
    "KDB", 	/* Prefix -- this string should not appear anywhere else! */
    krb5_ktkdb_resolve,		/* resolve */
    krb5_ktkdb_get_name,	/* get_name */
    krb5_ktkdb_close,		/* close */
    krb5_ktkdb_get_entry,	/* get */
    NULL,			/* start_seq_get */
    NULL,			/* get_next */
    NULL,			/* end_get */
    NULL,			/* add (extended) */
    NULL,			/* remove (extended) */
    NULL, 		/* (void *) &krb5_ktfile_ser_entry */
};

typedef struct krb5_ktkdb_data {
    char * name;
} krb5_ktkdb_data;

krb5_error_code
krb5_ktkdb_resolve(context, name, id)
    krb5_context  	  context;
    const char		* name;
    krb5_keytab		* id;
{
    if ((*id = (krb5_keytab) malloc(sizeof(**id))) == NULL)
        return(ENOMEM);
    (*id)->ops = &krb5_kt_kdb_ops;
    (*id)->magic = KV5M_KEYTAB;
    return(0);
}

krb5_error_code
krb5_ktkdb_close(context, kt)
     krb5_context context;
     krb5_keytab kt;
{
  /*
   * This routine is responsible for freeing all memory allocated 
   * for this keytab.  There are no system resources that need
   * to be freed nor are there any open files.
   *
   * This routine should undo anything done by krb5_ktkdb_resolve().
   */

  kt->ops = NULL;
  krb5_xfree(kt);

  return 0;
}

static krb5_context ktkdb_ctx = NULL;

/*
 * Set a different context for use with ktkdb_get_entry().  This is
 * primarily useful for kadmind, where the gssapi library context,
 * which will be used for the keytab, will necessarily have a
 * different context than that used by the kadm5 library to access the
 * database for its own purposes.
 */
krb5_error_code
krb5_ktkdb_set_context(krb5_context ctx)
{
    ktkdb_ctx = ctx;
    return 0;
}

krb5_error_code
krb5_ktkdb_get_entry(in_context, id, principal, kvno, enctype, entry)
    krb5_context 	  in_context;
    krb5_keytab 	  id;
    krb5_const_principal  principal;
    krb5_kvno 	 	  kvno;
    krb5_enctype 	  enctype;
    krb5_keytab_entry 	* entry;
{
    krb5_context	  context;
    krb5_keyblock       * master_key;
    krb5_error_code 	  kerror = 0;
    krb5_key_data 	* key_data;
    krb5_db_entry 	  db_entry;
    krb5_boolean 	  more = 0;
    int 	 	  n = 0;
    int xrealm_tgt;
    krb5_boolean similar;

    if (ktkdb_ctx)
	context = ktkdb_ctx;
    else
	context = in_context;

    xrealm_tgt = is_xrealm_tgt(context, principal);

    /* Open database */
    /* krb5_db_init(context); */
    if ((kerror = krb5_db_open_database(context)))
        return(kerror);

    /* get_principal */
    kerror = krb5_db_get_principal(context, principal, &
				       db_entry, &n, &more);
    if (kerror) {
        krb5_db_close_database(context);
        return(kerror);
    }
    if (n != 1) {
	krb5_db_close_database(context);
	return KRB5_KT_NOTFOUND;
    }

    if (db_entry.attributes & KRB5_KDB_DISALLOW_SVR
	|| db_entry.attributes & KRB5_KDB_DISALLOW_ALL_TIX) {
	kerror = KRB5_KT_NOTFOUND;
	goto error;
    }

    /* match key */
    kerror = krb5_db_get_mkey(context, &master_key);
    if (kerror)
	goto error;

    /* For cross realm tgts, we match whatever enctype is provided;
     * for other principals, we only match the first enctype that is
     * found.  Since the TGS and AS code do the same thing, then we
     * will only successfully decrypt  tickets we have issued.*/
    kerror = krb5_dbe_find_enctype(context, &db_entry,
				   xrealm_tgt?enctype:-1,
				   -1, kvno, &key_data);
    if (kerror)
	goto error;


    kerror = krb5_dbekd_decrypt_key_data(context, master_key,
					 key_data, &entry->key, NULL);
    if (kerror)
	goto error;

    if (enctype > 0) {	
	kerror = krb5_c_enctype_compare(context, enctype,
					entry->key.enctype, &similar);
	if (kerror)
	    goto error;

	if (!similar) {
	    kerror = KRB5_KDB_NO_PERMITTED_KEY;
	    goto error;
	}
    }
    /*
     * Coerce the enctype of the output keyblock in case we got an
     * inexact match on the enctype.
     */
    entry->key.enctype = enctype;

    kerror = krb5_copy_principal(context, principal, &entry->principal);
    if (kerror)
	goto error;

    /* Close database */
  error:
    krb5_dbe_free_contents(context, &db_entry);
    krb5_db_close_database(context);
    return(kerror);
}

/*
 * is_xrealm_tgt: Returns true if the principal is a cross-realm  TGT
 * principal-- a principal with first component  krbtgt and second
 * component not equal to realm.
 */
static int
is_xrealm_tgt(krb5_context context, krb5_const_principal princ)
{
    krb5_data *dat;
    if (krb5_princ_size(context, princ) != 2)
	return 0;
    dat = krb5_princ_component(context, princ, 0);
    if (strncmp("krbtgt", dat->data, dat->length) != 0)
	return 0;
    dat = krb5_princ_component(context, princ, 1);
    if (dat->length != princ->realm.length)
	return 1;
    if (strncmp(dat->data, princ->realm.data, dat->length) == 0)
	return 0;
    return 1;

}

