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/*
* Copyright (c) 2008-2010 Moxie Marlinspike
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*/
#include "HOTP.h"
#include "Util.h"
#include <stdlib.h>
#include <string.h>
#include <openssl/hmac.h>
#include <security/pam_modules.h>
#include <security/pam_ext.h>
#include <syslog.h>
#undef DEBUG
#define HMAC_SIZE 20
#define OFFSET_BYTE 19
HOTP::HOTP(const pam_handle_t *pamh, const unsigned char *key,
uint32_t keyLength, uint64_t counter, uint32_t pin)
{
this->pamh = pamh;
uint32_t pinActivatedKeyLength = keyLength + sizeof(pin);
unsigned char *pinActivatedKey = (unsigned char*)malloc(pinActivatedKeyLength);
memcpy(pinActivatedKey, key, keyLength);
Util::int32ToArrayBigEndian(pinActivatedKey + keyLength, pin);
#ifdef DEBUG
for (int i=0;i<pinActivatedKeyLength;i++) {
pam_syslog(pamh, LOG_EMERG, "Key[%d]: %x", i, pinActivatedKey[i]);
}
#endif
unsigned char counterData[sizeof(counter)];
Util::int64ToArrayBigEndian(counterData, counter);
unsigned char hmac[HMAC_SIZE];
HMAC(EVP_sha1(), pinActivatedKey, pinActivatedKeyLength,
counterData, sizeof(counterData), hmac, NULL);
#ifdef DEBUG
for (int i=0;i<sizeof(hmac);i++) {
pam_syslog(pamh, LOG_EMERG, "HMAC[%d]: %d", i, hmac[i]);
}
#endif
otp = truncate(hmac);
#ifdef DEBUG
pam_syslog(pamh, LOG_EMERG, "OTP Calculated: %d", otp);
#endif
memset(counterData, 0, sizeof(counterData));
memset(hmac, 0, sizeof(hmac));
memset(pinActivatedKey, 0, pinActivatedKeyLength);
free(pinActivatedKey);
}
uint32_t HOTP::getOneTimePasscode() {
return otp;
}
uint32_t HOTP::truncate(unsigned char *hmac) {
uint8_t offset = hmac[OFFSET_BYTE] & 0xf;
uint32_t binCode =
(hmac[offset] & 0x7f) << 24
| (hmac[offset+1] & 0xff) << 16
| (hmac[offset+2] & 0xff) << 8
| (hmac[offset+3] & 0xff) ;
return binCode % 1000000;
}
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