/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright 1993 by OpenVision Technologies, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appears in all copies and
 * that both that copyright notice and this permission notice appear in
 * supporting documentation, and that the name of OpenVision not be used
 * in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission. OpenVision makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 * OPENVISION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL OPENVISION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
 * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * $Id$
 */

/*
 * functions to check sequence numbers for replay and sequencing
 */

#include "gssapiP_generic.h"
#include <string.h>

#define QUEUE_LENGTH 20

typedef struct _queue {
    int do_replay;
    int do_sequence;
    int start;
    int length;
    gssint_uint64 firstnum;
    /* Stored as deltas from firstnum.  This way, the high bit won't
       overflow unless we've actually gone through 2**n messages, or
       gotten something *way* out of sequence.  */
    gssint_uint64 elem[QUEUE_LENGTH];
    /* All ones for 64-bit sequence numbers; 32 ones for 32-bit
       sequence numbers.  */
    gssint_uint64 mask;
} queue;

/* rep invariant:
 *  - the queue is a circular queue.  The first element (q->elem[q->start])
 * is the oldest.  The last element is the newest.
 */

#define QSIZE(q) (sizeof((q)->elem)/sizeof((q)->elem[0]))
#define QELEM(q,i) ((q)->elem[(i)%QSIZE(q)])

static void
queue_insert(queue *q, int after, gssint_uint64 seqnum)
{
    /* insert.  this is not the fastest way, but it's easy, and it's
       optimized for insert at end, which is the common case */
    int i;

    /* common case: at end, after == q->start+q->length-1 */

    /* move all the elements (after,last] up one slot */

    for (i=q->start+q->length-1; i>after; i--)
        QELEM(q,i+1) = QELEM(q,i);

    /* fill in slot after+1 */

    QELEM(q,after+1) = seqnum;

    /* Either increase the length by one, or move the starting point up
       one (deleting the first element, which got bashed above), as
       appropriate. */

    if (q->length == QSIZE(q)) {
        q->start++;
        if (q->start == QSIZE(q))
            q->start = 0;
    } else {
        q->length++;
    }
}

gss_int32
g_order_init(void **vqueue, gssint_uint64 seqnum,
             int do_replay, int do_sequence, int wide_nums)
{
    queue *q;

    if ((q = (queue *) malloc(sizeof(queue))) == NULL)
        return(ENOMEM);

    /* This stops valgrind from complaining about writing uninitialized
       data if the caller exports the context and writes it to a file.
       We don't actually use those bytes at all, but valgrind still
       complains.  */
    memset(q, 0xfe, sizeof(*q));

    q->do_replay = do_replay;
    q->do_sequence = do_sequence;
    q->mask = wide_nums ? ~(gssint_uint64)0 : 0xffffffffUL;

    q->start = 0;
    q->length = 1;
    q->firstnum = seqnum;
    q->elem[q->start] = ((gssint_uint64)0 - 1) & q->mask;

    *vqueue = (void *) q;
    return(0);
}

gss_int32
g_order_check(void **vqueue, gssint_uint64 seqnum)
{
    queue *q;
    int i;
    gssint_uint64 expected;

    q = (queue *) (*vqueue);

    if (!q->do_replay && !q->do_sequence)
        return(GSS_S_COMPLETE);

    /* All checks are done relative to the initial sequence number, to
       avoid (or at least put off) the pain of wrapping.  */
    seqnum -= q->firstnum;
    /* If we're only doing 32-bit values, adjust for that again.

       Note that this will probably be the wrong thing to if we get
       2**32 messages sent with 32-bit sequence numbers.  */
    seqnum &= q->mask;

    /* rule 1: expected sequence number */

    expected = (QELEM(q,q->start+q->length-1)+1) & q->mask;
    if (seqnum == expected) {
        queue_insert(q, q->start+q->length-1, seqnum);
        return(GSS_S_COMPLETE);
    }

    /* rule 2: > expected sequence number */

    if ((seqnum > expected)) {
        queue_insert(q, q->start+q->length-1, seqnum);
        if (q->do_replay && !q->do_sequence)
            return(GSS_S_COMPLETE);
        else
            return(GSS_S_GAP_TOKEN);
    }

    /* rule 3: seqnum < seqnum(first) */

    if ((seqnum < QELEM(q,q->start)) &&
        /* Is top bit of whatever width we're using set?

           We used to check for greater than or equal to firstnum, but
           (1) we've since switched to compute values relative to
           firstnum, so the lowest we can have is 0, and (2) the effect
           of the original scheme was highly dependent on whether
           firstnum was close to either side of 0.  (Consider
           firstnum==0xFFFFFFFE and we miss three packets; the next
           packet is *new* but would look old.)

           This check should give us 2**31 or 2**63 messages "new", and
           just as many "old".  That's not quite right either.  */
        (seqnum & (1 + (q->mask >> 1)))
    ) {
        if (q->do_replay && !q->do_sequence)
            return(GSS_S_OLD_TOKEN);
        else
            return(GSS_S_UNSEQ_TOKEN);
    }

    /* rule 4+5: seqnum in [seqnum(first),seqnum(last)]  */

    else {
        if (seqnum == QELEM(q,q->start+q->length-1))
            return(GSS_S_DUPLICATE_TOKEN);

        for (i=q->start; i<q->start+q->length-1; i++) {
            if (seqnum == QELEM(q,i))
                return(GSS_S_DUPLICATE_TOKEN);
            if ((seqnum > QELEM(q,i)) && (seqnum < QELEM(q,i+1))) {
                queue_insert(q, i, seqnum);
                if (q->do_replay && !q->do_sequence)
                    return(GSS_S_COMPLETE);
                else
                    return(GSS_S_UNSEQ_TOKEN);
            }
        }
    }

    /* this should never happen */
    return(GSS_S_FAILURE);
}

void
g_order_free(void **vqueue)
{
    queue *q;

    q = (queue *) (*vqueue);

    free(q);

    *vqueue = NULL;
}

/*
 * These support functions are for the serialization routines
 */
gss_uint32
g_queue_size(void *vqueue, size_t *sizep)
{
    *sizep += sizeof(queue);
    return 0;
}

gss_uint32
g_queue_externalize(void *vqueue, unsigned char **buf, size_t *lenremain)
{
    if (*lenremain < sizeof(queue))
        return ENOMEM;
    memcpy(*buf, vqueue, sizeof(queue));
    *buf += sizeof(queue);
    *lenremain -= sizeof(queue);

    return 0;
}

gss_uint32
g_queue_internalize(void **vqueue, unsigned char **buf, size_t *lenremain)
{
    void *q;

    if (*lenremain < sizeof(queue))
        return EINVAL;
    if ((q = malloc(sizeof(queue))) == 0)
        return ENOMEM;
    memcpy(q, *buf, sizeof(queue));
    *buf += sizeof(queue);
    *lenremain -= sizeof(queue);
    *vqueue = q;
    return 0;
}
