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/* gc-pbkdf2-sha1.c --- Password-Based Key Derivation Function a'la PKCS#5
Copyright (C) 2002-2006, 2009-2019 Free Software Foundation, Inc.
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 2, 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 <https://www.gnu.org/licenses/>. */
/* Written by Simon Josefsson. */
#include <config.h>
#include "gc.h"
#include <stdlib.h>
#include <string.h>
/* Implement PKCS#5 PBKDF2 as per RFC 2898. The PRF to use is hard
coded to be HMAC-SHA1. Inputs are the password P of length PLEN,
the salt S of length SLEN, the iteration counter C (> 0), and the
desired derived output length DKLEN. Output buffer is DK which
must have room for at least DKLEN octets. The output buffer will
be filled with the derived data. */
Gc_rc
gc_pbkdf2_sha1 (const char *P, size_t Plen,
const char *S, size_t Slen,
unsigned int c,
char *DK, size_t dkLen)
{
unsigned int hLen = 20;
char U[20];
char T[20];
unsigned int u;
unsigned int l;
unsigned int r;
unsigned int i;
unsigned int k;
int rc;
char *tmp;
size_t tmplen = Slen + 4;
if (c == 0)
return GC_PKCS5_INVALID_ITERATION_COUNT;
if (dkLen == 0)
return GC_PKCS5_INVALID_DERIVED_KEY_LENGTH;
if (dkLen > 4294967295U)
return GC_PKCS5_DERIVED_KEY_TOO_LONG;
l = ((dkLen - 1) / hLen) + 1;
r = dkLen - (l - 1) * hLen;
tmp = malloc (tmplen);
if (tmp == NULL)
return GC_MALLOC_ERROR;
memcpy (tmp, S, Slen);
for (i = 1; i <= l; i++)
{
memset (T, 0, hLen);
for (u = 1; u <= c; u++)
{
if (u == 1)
{
tmp[Slen + 0] = (i & 0xff000000) >> 24;
tmp[Slen + 1] = (i & 0x00ff0000) >> 16;
tmp[Slen + 2] = (i & 0x0000ff00) >> 8;
tmp[Slen + 3] = (i & 0x000000ff) >> 0;
rc = gc_hmac_sha1 (P, Plen, tmp, tmplen, U);
}
else
rc = gc_hmac_sha1 (P, Plen, U, hLen, U);
if (rc != GC_OK)
{
free (tmp);
return rc;
}
for (k = 0; k < hLen; k++)
T[k] ^= U[k];
}
memcpy (DK + (i - 1) * hLen, T, i == l ? r : hLen);
}
free (tmp);
return GC_OK;
}
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