mirror of
https://github.com/cryb-to/cryb-otp.git
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96 lines
2.9 KiB
C
96 lines
2.9 KiB
C
/*-
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* Copyright (c) 2013-2018 The University of Oslo
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* Copyright (c) 2016-2018 Dag-Erling Smørgrav
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "cryb/impl.h"
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#include <stddef.h>
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#include <stdint.h>
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#include <cryb/assert.h>
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#include <cryb/oath.h>
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#include <cryb/otp.h>
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#include "cryb_otp_impl.h"
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/*
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* Resynchronize a desynchronized event-mode key.
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*
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* XXX review carefully for off-by-one errors, and write unit tests
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*/
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static int
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otp_resync_recursive(oath_key *key, unsigned long *response,
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unsigned int n, unsigned int w)
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{
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uint64_t first, prev, last;
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int ret;
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first = key->counter;
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last = first + w;
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while (w > 0) {
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prev = key->counter;
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ret = oath_hotp_match(key, response[0], last - key->counter);
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if (ret < 1)
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return (ret);
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assertf(key->counter > prev, "counter did not advance");
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w -= key->counter - prev;
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if (n == 1)
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return (key->counter - prev);
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prev = key->counter;
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ret = otp_resync_recursive(key, response + 1, n - 1, w);
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if (ret > 0)
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return (ret);
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key->counter = prev;
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}
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return (0);
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}
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int
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otp_resync(oath_key *key, unsigned long *response, unsigned int n)
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{
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unsigned int i, w;
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int ret;
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/* only applicable to RFC 4226 HOTP for now */
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/* note: n == 1 is identical to otp_verify() */
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if (key->mode != om_hotp || n < 1)
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return (-1);
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/* compute window size based on number of responses */
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for (i = 0, w = 1; i < n; ++i)
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w = w * (HOTP_WINDOW + 1);
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/* recursive search within window */
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ret = otp_resync_recursive(key, response, n, w);
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/* ... */
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return (ret);
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}
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