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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/gssapi/generic/util_seqstate.c - sequence number checking */
/*
* Copyright (C) 2014 by the Massachusetts Institute of Technology.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDER 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 "gssapiP_generic.h"
#include <string.h>
struct g_seqnum_state_st {
/* Flags to indicate whether we are supposed to check for replays or
* enforce strict sequencing. */
int do_replay;
int do_sequence;
/* UINT32_MAX for 32-bit sequence numbers, UINT64_MAX for 64-bit. Mask
* against this after arithmetic to stay within the correct range. */
uint64_t seqmask;
/* The initial sequence number for this context. This value will be
* subtracted from all received sequence numbers to simplify wraparound. */
uint64_t base;
/* The expected next sequence number (one more than the highest previously
* seen sequence number), relative to base. */
uint64_t next;
/*
* A bitmap for the 64 sequence numbers prior to next. If the 1<<(i-1) bit
* is set, then we have seen seqnum next-i relative to base. The least
* significant bit is always set if we have received any sequence numbers,
* and indicates the highest sequence number we have seen (next-1). When
* we advance next, we shift recvmap to the left.
*/
uint64_t recvmap;
};
long
g_seqstate_init(g_seqnum_state *state_out, uint64_t seqnum, int do_replay,
int do_sequence, int wide)
{
g_seqnum_state state;
*state_out = NULL;
state = malloc(sizeof(*state));
if (state == NULL)
return ENOMEM;
state->do_replay = do_replay;
state->do_sequence = do_sequence;
state->seqmask = wide ? UINT64_MAX : UINT32_MAX;
state->base = seqnum;
state->next = state->recvmap = 0;
*state_out = state;
return 0;
}
OM_uint32
g_seqstate_check(g_seqnum_state state, uint64_t seqnum)
{
uint64_t rel_seqnum, offset, bit;
if (!state->do_replay && !state->do_sequence)
return GSS_S_COMPLETE;
/* Use the difference from the base seqnum, to simplify wraparound. */
rel_seqnum = (seqnum - state->base) & state->seqmask;
if (rel_seqnum >= state->next) {
/* seqnum is the expected sequence number or in the future. Update the
* received bitmap and expected next sequence number. */
offset = rel_seqnum - state->next;
state->recvmap = (state->recvmap << (offset + 1)) | 1;
state->next = (rel_seqnum + 1) & state->seqmask;
return (offset > 0 && state->do_sequence) ? GSS_S_GAP_TOKEN :
GSS_S_COMPLETE;
}
/* seqnum is in the past. Check if it's too old for replay detection. */
offset = state->next - rel_seqnum;
if (offset > 64)
return state->do_sequence ? GSS_S_UNSEQ_TOKEN : GSS_S_OLD_TOKEN;
/* Check for replay and mark as received. */
bit = (uint64_t)1 << (offset - 1);
if (state->do_replay && (state->recvmap & bit))
return GSS_S_DUPLICATE_TOKEN;
state->recvmap |= bit;
return state->do_sequence ? GSS_S_UNSEQ_TOKEN : GSS_S_COMPLETE;
}
void
g_seqstate_free(g_seqnum_state state)
{
free(state);
}
/*
* These support functions are for the serialization routines
*/
void
g_seqstate_size(g_seqnum_state state, size_t *sizep)
{
*sizep += sizeof(*state);
}
long
g_seqstate_externalize(g_seqnum_state state, unsigned char **buf,
size_t *lenremain)
{
if (*lenremain < sizeof(*state))
return ENOMEM;
memcpy(*buf, state, sizeof(*state));
*buf += sizeof(*state);
*lenremain -= sizeof(*state);
return 0;
}
long
g_seqstate_internalize(g_seqnum_state *state_out, unsigned char **buf,
size_t *lenremain)
{
g_seqnum_state state;
*state_out = NULL;
if (*lenremain < sizeof(*state))
return EINVAL;
state = malloc(sizeof(*state));
if (state == NULL)
return ENOMEM;
memcpy(state, *buf, sizeof(*state));
*buf += sizeof(*state);
*lenremain -= sizeof(*state);
*state_out = state;
return 0;
}
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