135 lines
4.0 KiB
C
135 lines
4.0 KiB
C
/** BEGIN COPYRIGHT BLOCK
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* Additional permission under GPLv3 section 7:
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*
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* In the following paragraph, "GPL" means the GNU General Public
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* License, version 3 or any later version, and "Non-GPL Code" means
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* code that is governed neither by the GPL nor a license
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* compatible with the GPL.
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*
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* You may link the code of this Program with Non-GPL Code and convey
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* linked combinations including the two, provided that such Non-GPL
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* Code only links to the code of this Program through those well
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* defined interfaces identified in the file named EXCEPTION found in
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* the source code files (the "Approved Interfaces"). The files of
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* Non-GPL Code may instantiate templates or use macros or inline
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* functions from the Approved Interfaces without causing the resulting
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* work to be covered by the GPL. Only the copyright holders of this
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* Program may make changes or additions to the list of Approved
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* Interfaces.
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*
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* Authors:
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* Nathaniel McCallum <npmccallum@redhat.com>
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*
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* Copyright (C) 2013 Red Hat, Inc.
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* All rights reserved.
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* END COPYRIGHT BLOCK **/
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/*
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* This file contains an implementation of HOTP (RFC 4226) and TOTP (RFC 6238).
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* For details of how these algorithms work, please see the relevant RFCs.
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*/
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#include "hotp.h"
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#include <endian.h>
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#include <string.h>
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#include <syslog.h>
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#include <time.h>
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#include <openssl/hmac.h>
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struct digest_buffer {
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unsigned char buf[EVP_MAX_MD_SIZE];
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unsigned int len;
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};
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static const struct {
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const char *algo;
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const char *sn_mech;
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} algo2mech[] = {
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{ "sha1", SN_sha1 },
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{ "sha256", SN_sha256 },
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{ "sha384", SN_sha384 },
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{ "sha512", SN_sha512 },
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{ }
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};
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static bool hmac(const struct hotp_token_key *key, const char *sn_mech,
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uint64_t counter, struct digest_buffer *out)
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{
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unsigned char in[sizeof(uint64_t)];
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const EVP_MD *evp;
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memcpy(in, &counter, sizeof(uint64_t));
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evp = EVP_get_digestbyname(sn_mech);
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if (evp == NULL) {
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return false;
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}
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if (!HMAC(evp, (void *)key->bytes, key->len, in, sizeof(in),
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out->buf, &out->len)) {
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return false;
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}
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return true;
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}
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/*
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* An implementation of HOTP (RFC 4226).
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*/
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bool hotp(const struct hotp_token *token, uint64_t counter, uint32_t *out)
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{
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const char *mech = SN_sha1;
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struct digest_buffer digest;
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unsigned char counter_buf[sizeof(uint64_t)];
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int digits = token->digits;
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int i;
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uint64_t div, offset, binary;
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/* Convert counter to network byte order. */
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counter = htobe64(counter);
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/* Copy counter to buffer */
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memcpy(counter_buf, &counter, sizeof(uint64_t));
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/* Find the mech. */
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for (i = 0; algo2mech[i].algo; i++) {
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if (strcasecmp(algo2mech[i].algo, token->algo) == 0) {
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mech = algo2mech[i].sn_mech;
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break;
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}
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}
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/* Create the digits divisor. */
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for (div = 1; digits > 0; digits--) {
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div *= 10;
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}
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/* Do the digest. */
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if (!hmac(&(token->key), mech, counter, &digest)) {
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return false;
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}
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/* Truncate. */
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offset = digest.buf[digest.len - 1] & 0xf;
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binary = (digest.buf[offset + 0] & 0x7f) << 0x18;
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binary |= (digest.buf[offset + 1] & 0xff) << 0x10;
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binary |= (digest.buf[offset + 2] & 0xff) << 0x08;
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binary |= (digest.buf[offset + 3] & 0xff) << 0x00;
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binary = binary % div;
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*out = binary;
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return true;
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}
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