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/** BEGIN COPYRIGHT BLOCK
* 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, see <http://www.gnu.org/licenses/>.
*
* Additional permission under GPLv3 section 7:
*
* In the following paragraph, "GPL" means the GNU General Public
* License, version 3 or any later version, and "Non-GPL Code" means
* code that is governed neither by the GPL nor a license
* compatible with the GPL.
*
* You may link the code of this Program with Non-GPL Code and convey
* linked combinations including the two, provided that such Non-GPL
* Code only links to the code of this Program through those well
* defined interfaces identified in the file named EXCEPTION found in
* the source code files (the "Approved Interfaces"). The files of
* Non-GPL Code may instantiate templates or use macros or inline
* functions from the Approved Interfaces without causing the resulting
* work to be covered by the GPL. Only the copyright holders of this
* Program may make changes or additions to the list of Approved
* Interfaces.
*
* Authors:
* Nathaniel McCallum <npmccallum@redhat.com>
*
* Copyright (C) 2013 Red Hat, Inc.
* All rights reserved.
* END COPYRIGHT BLOCK **/
/*
* This file contains an implementation of HOTP (RFC 4226) and TOTP (RFC 6238).
* For details of how these algorithms work, please see the relevant RFCs.
*/
#include "librfc.h"
#include <time.h>
#include <nss.h>
#include <pk11pub.h>
#include <hasht.h>
#include <prnetdb.h>
struct digest_buffer {
uint8_t buf[SHA512_LENGTH];
unsigned int len;
};
static const struct {
const char *algo;
CK_MECHANISM_TYPE mech;
} algo2mech[] = {
{ "sha1", CKM_SHA_1_HMAC },
{ "sha256", CKM_SHA256_HMAC },
{ "sha384", CKM_SHA384_HMAC },
{ "sha512", CKM_SHA512_HMAC },
{ }
};
/*
* This code is mostly cargo-cult taken from here:
* http://www.mozilla.org/projects/security/pki/nss/tech-notes/tn5.html
*
* It should implement HMAC with the given mechanism (SHA: 1, 256, 384, 512).
*/
static bool hmac(SECItem *key, CK_MECHANISM_TYPE mech, const SECItem *in,
struct digest_buffer *out)
{
SECItem param = { siBuffer, NULL, 0 };
PK11SlotInfo *slot = NULL;
PK11SymKey *symkey = NULL;
PK11Context *ctx = NULL;
bool ret = false;
SECStatus s;
slot = PK11_GetBestSlot(mech, NULL);
if (slot == NULL) {
slot = PK11_GetInternalKeySlot();
if (slot == NULL) {
goto done;
}
}
symkey = PK11_ImportSymKey(slot, mech, PK11_OriginUnwrap,
CKA_SIGN, key, NULL);
if (symkey == NULL)
goto done;
ctx = PK11_CreateContextBySymKey(mech, CKA_SIGN, symkey, ¶m);
if (ctx == NULL)
goto done;
s = PK11_DigestBegin(ctx);
if (s != SECSuccess)
goto done;
s = PK11_DigestOp(ctx, in->data, in->len);
if (s != SECSuccess)
goto done;
s = PK11_DigestFinal(ctx, out->buf, &out->len, sizeof(out->buf));
if (s != SECSuccess)
goto done;
ret = true;
done:
if (ctx != NULL)
PK11_DestroyContext(ctx, PR_TRUE);
if (symkey != NULL)
PK11_FreeSymKey(symkey);
if (slot != NULL)
PK11_FreeSlot(slot);
return ret;
}
/*
* An implementation of HOTP (RFC 4226).
*/
bool hotp(const struct hotp_token *token, uint64_t counter, uint32_t *out)
{
const SECItem cntr = { siBuffer, (uint8_t *) &counter, sizeof(counter) };
SECItem keyitm = { siBuffer, token->key.bytes, token->key.len };
CK_MECHANISM_TYPE mech = CKM_SHA_1_HMAC;
PRUint64 offset, binary, div;
struct digest_buffer digest;
int digits = token->digits;
int i;
/* Convert counter to network byte order. */
counter = PR_htonll(counter);
/* Find the mech. */
for (i = 0; algo2mech[i].algo; i++) {
if (strcasecmp(algo2mech[i].algo, token->algo) == 0) {
mech = algo2mech[i].mech;
break;
}
}
/* Create the digits divisor. */
for (div = 1; digits > 0; digits--) {
div *= 10;
}
/* Do the digest. */
if (!hmac(&keyitm, mech, &cntr, &digest)) {
return false;
}
/* Truncate. */
offset = digest.buf[digest.len - 1] & 0xf;
binary = (digest.buf[offset + 0] & 0x7f) << 0x18;
binary |= (digest.buf[offset + 1] & 0xff) << 0x10;
binary |= (digest.buf[offset + 2] & 0xff) << 0x08;
binary |= (digest.buf[offset + 3] & 0xff) << 0x00;
binary = binary % div;
*out = binary;
return true;
}
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