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https://github.com/cryb-to/cryb-to.git
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f82bbc1400
Add an oath_mode(3) function which translates from mode names to numbers. Consistently use UINT_MAX, not -1, to indicate an invalid response. Change the meaning of the window parameter to always indicate the number of codes to check *in addition* to the current code. Note that for TOTP, the window goes in both directions; a window of 1 means to check the current code plus the previous and next.
129 lines
3.6 KiB
C
129 lines
3.6 KiB
C
/*-
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* Copyright (c) 2012-2013 The University of Oslo
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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 <limits.h>
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#include <stdint.h>
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#include <string.h>
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#include <cryb/hmac_sha1.h>
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#include <cryb/oath.h>
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#define StToNum(St) (St)
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static uint32_t
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DT(const uint8_t *String)
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{
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uint8_t OffsetBits;
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int Offset;
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uint32_t P;
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OffsetBits = String[19] & 0x0f;
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Offset = StToNum(OffsetBits);
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P = (uint32_t)String[Offset + 0] << 24 |
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(uint32_t)String[Offset + 1] << 16 |
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(uint32_t)String[Offset + 2] << 8 |
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(uint32_t)String[Offset + 3];
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return (P & 0x7fffffffUL);
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}
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unsigned int
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oath_hotp(const uint8_t *K, size_t Klen, uint64_t seq, unsigned int Digit)
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{
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hmac_sha1_ctx ctx;
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uint8_t C[8];
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uint8_t HS[20];
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uint32_t Sbits, Snum;
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unsigned int mod, D;
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for (int i = 7; i >= 0; --i) {
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C[i] = seq & 0xff;
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seq >>= 8;
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}
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/* HS = HMAC-SHA-1(K,C) */
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hmac_sha1_init(&ctx, K, Klen);
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hmac_sha1_update(&ctx, (const uint8_t *)&C, sizeof C);
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hmac_sha1_final(&ctx, HS);
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Sbits = DT(HS);
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Snum = StToNum(Sbits);
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for (mod = 1; Digit > 0; --Digit)
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mod *= 10;
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D = Snum % mod;
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return (D);
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}
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/*
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* Computes the current code for the given key and advances the counter.
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*/
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unsigned int
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oath_hotp_current(struct oath_key *k)
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{
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unsigned int code;
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if (k == NULL)
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return (UINT_MAX);
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if (k->mode != om_hotp)
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return (UINT_MAX);
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if (k->counter == UINT64_MAX)
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return (UINT_MAX);
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code = oath_hotp(k->key, k->keylen, k->counter, k->digits);
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k->counter += 1;
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return (code);
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}
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/*
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* Compares the code provided by the user with expected values within a
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* given window. Returns 1 if there was a match, 0 if not, and -1 if an
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* error occurred. Also advances the counter if there was a match.
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*/
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int
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oath_hotp_match(struct oath_key *k, unsigned int response, int window)
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{
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unsigned int code;
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if (k == NULL)
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return (-1);
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if (window < 0)
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return (-1);
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if (k->mode != om_hotp)
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return (-1);
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if (k->counter >= UINT64_MAX - window - 1)
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return (-1);
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for (int i = 0; i <= window; ++i) {
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code = oath_hotp(k->key, k->keylen, k->counter + i, k->digits);
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if (code == response && !k->dummy) {
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k->counter = k->counter + i;
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return (1);
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}
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}
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return (0);
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}
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