heimdal/lib/gssapi/sequence.c

/*
 * Copyright (c) 2003 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden). 
 * All rights reserved. 
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 *
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the distribution. 
 *
 * 3. Neither the name of the Institute nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
 * SUCH DAMAGE. 
 */

#include "gssapi_locl.h"

RCSID("$Id$");

#define DEFAULT_JITTER_WINDOW 20

struct gss_msg_order {
    OM_uint32 flags;
    OM_uint32 start;
    OM_uint32 length;
    OM_uint32 jitter_window;
    OM_uint32 first_seq;
    OM_uint32 elem[1];
};

/*
 *
 */

OM_uint32
gssapi_msg_order_create(OM_uint32 *minor_status,
			struct gss_msg_order **o, 
			OM_uint32 flags, 
			OM_uint32 seq_num, 
			OM_uint32 jitter_window)
{
    size_t len;

    if (jitter_window == 0)
	jitter_window = DEFAULT_JITTER_WINDOW;

    len = jitter_window * sizeof((*o)->elem[0]);
    len += sizeof(**o);
    len -= sizeof((*o)->elem[0]);
    
    *o = malloc(len);
    if (*o == NULL) {
	*minor_status = ENOMEM;
	return GSS_S_FAILURE;
    }	
    memset(*o, 0, len);
    (*o)->flags = flags;
    (*o)->length = 0;
    (*o)->first_seq = seq_num;
    (*o)->jitter_window = jitter_window;
    (*o)->elem[0] = seq_num - 1;

    *minor_status = 0;
    return GSS_S_COMPLETE;
}

OM_uint32
gssapi_msg_order_destroy(struct gss_msg_order **m)
{
    free(*m);
    *m = NULL;
    return GSS_S_COMPLETE;
}

static void
elem_set(struct gss_msg_order *o, unsigned int slot, OM_uint32 val)
{
    o->elem[slot % o->jitter_window] = val;
}

static void
elem_insert(struct gss_msg_order *o, 
	    unsigned int after_slot,
	    OM_uint32 seq_num)
{
    assert(o->jitter_window > after_slot);

    if (o->length > after_slot)
	memmove(&o->elem[after_slot + 1], &o->elem[after_slot],
		(o->length - after_slot - 1) * sizeof(o->elem[0]));

    elem_set(o, after_slot, seq_num);

    if (o->length < o->jitter_window)
	o->length++;
}

/* rule 1: expected sequence number */
/* rule 2: > expected sequence number */
/* rule 3: seqnum < seqnum(first) */
/* rule 4+5: seqnum in [seqnum(first),seqnum(last)]  */

OM_uint32
gssapi_msg_order_check(struct gss_msg_order *o, OM_uint32 seq_num)
{
    OM_uint32 r;
    int i;

    if (o == NULL)
	return GSS_S_COMPLETE;

    if ((o->flags & (GSS_C_REPLAY_FLAG|GSS_C_SEQUENCE_FLAG)) == 0)
	return GSS_S_COMPLETE;

    /* check if the packet is the next in order */
    if (o->elem[0] == seq_num - 1) {
	elem_insert(o, 0, seq_num);
	return GSS_S_COMPLETE;
    }

    r = (o->flags & (GSS_C_REPLAY_FLAG|GSS_C_SEQUENCE_FLAG))==GSS_C_REPLAY_FLAG;

    /* sequence number larger then largest sequence number 
     * or smaller then the first sequence number */
    if (seq_num > o->elem[0]
	|| seq_num < o->first_seq
	|| o->length == 0) 
    {
	elem_insert(o, 0, seq_num);
	if (r) {
	    return GSS_S_COMPLETE;
	} else {
	    return GSS_S_GAP_TOKEN;
	}
    }

    assert(o->length > 0);

    /* sequence number smaller the first sequence number */
    if (seq_num < o->elem[o->length - 1]) {
	if (r)
	    return(GSS_S_OLD_TOKEN);
	else
	    return(GSS_S_UNSEQ_TOKEN);
    }

    if (seq_num == o->elem[o->length - 1]) {
	return GSS_S_DUPLICATE_TOKEN;
    }

    for (i = 0; i < o->length - 1; i++) {
	if (o->elem[i] == seq_num)
	    return GSS_S_DUPLICATE_TOKEN;
	if (o->elem[i + 1] < seq_num && o->elem[i] < seq_num) {
	    elem_insert(o, i, seq_num);
	    if (r)
		return GSS_S_COMPLETE;
	    else
		return GSS_S_UNSEQ_TOKEN;
	}
    }

    return GSS_S_FAILURE;
}

OM_uint32
gssapi_msg_order_f(OM_uint32 flags)
{
    return flags & (GSS_C_SEQUENCE_FLAG|GSS_C_REPLAY_FLAG);
}