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/*
* Copyright (C) 2013 Tobias Brunner
* HSR Hochschule fuer Technik Rapperswil
*
* 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 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* 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.
*/
#include "pkcs12.h"
#include <library.h>
#include <utils/debug.h>
/**
* v * ceiling(len/v)
*/
#define PKCS12_LEN(len, v) (((len) + v-1) & ~(v-1))
/**
* Copy src to dst as many times as possible
*/
static inline void copy_chunk(chunk_t dst, chunk_t src)
{
size_t i;
for (i = 0; i < dst.len; i++)
{
dst.ptr[i] = src.ptr[i % src.len];
}
}
/**
* Treat two chunks as integers in network order and add them together.
* The result is stored in the first chunk, if the second chunk is longer or the
* result overflows this is ignored.
*/
static void add_chunks(chunk_t a, chunk_t b)
{
uint16_t sum;
uint8_t rem = 0;
ssize_t i, j;
for (i = a.len - 1, j = b.len -1; i >= 0 && j >= 0; i--, j--)
{
sum = a.ptr[i] + b.ptr[j] + rem;
a.ptr[i] = (u_char)sum;
rem = sum >> 8;
}
for (; i >= 0 && rem; i--)
{
sum = a.ptr[i] + rem;
a.ptr[i] = (u_char)sum;
rem = sum >> 8;
}
}
/**
* Do the actual key derivation with the given hasher, password and id.
*/
static bool derive_key(hash_algorithm_t hash, chunk_t unicode, chunk_t salt,
uint64_t iterations, char id, chunk_t result)
{
chunk_t out = result, D, S, P = chunk_empty, I, Ai, B, Ij;
hasher_t *hasher;
size_t Slen, v, u;
uint64_t i;
bool success = FALSE;
hasher = lib->crypto->create_hasher(lib->crypto, hash);
if (!hasher)
{
DBG1(DBG_ASN, " %N hash algorithm not available",
hash_algorithm_names, hash);
return FALSE;
}
switch (hash)
{
case HASH_MD2:
case HASH_MD5:
case HASH_SHA1:
case HASH_SHA224:
case HASH_SHA256:
v = 64;
break;
case HASH_SHA384:
case HASH_SHA512:
v = 128;
break;
default:
goto end;
}
u = hasher->get_hash_size(hasher);
D = chunk_alloca(v);
memset(D.ptr, id, D.len);
Slen = PKCS12_LEN(salt.len, v);
I = chunk_alloca(Slen + PKCS12_LEN(unicode.len, v));
S = chunk_create(I.ptr, Slen);
P = chunk_create(I.ptr + Slen, I.len - Slen);
copy_chunk(S, salt);
copy_chunk(P, unicode);
Ai = chunk_alloca(u);
B = chunk_alloca(v);
while (TRUE)
{
if (!hasher->get_hash(hasher, D, NULL) ||
!hasher->get_hash(hasher, I, Ai.ptr))
{
goto end;
}
for (i = 1; i < iterations; i++)
{
if (!hasher->get_hash(hasher, Ai, Ai.ptr))
{
goto end;
}
}
memcpy(out.ptr, Ai.ptr, min(out.len, Ai.len));
out = chunk_skip(out, Ai.len);
if (!out.len)
{
break;
}
copy_chunk(B, Ai);
/* B = B+1 */
add_chunks(B, chunk_from_chars(0x01));
Ij = chunk_create(I.ptr, v);
for (i = 0; i < I.len; i += v, Ij.ptr += v)
{ /* Ij = Ij + B + 1 */
add_chunks(Ij, B);
}
}
success = TRUE;
end:
hasher->destroy(hasher);
return success;
}
/*
* Described in header
*/
bool pkcs12_derive_key(hash_algorithm_t hash, chunk_t password, chunk_t salt,
uint64_t iterations, pkcs12_key_type_t type, chunk_t key)
{
chunk_t unicode = chunk_empty;
bool success;
int i;
if (password.len)
{ /* convert the password to UTF-16BE (without BOM) with 0 terminator */
unicode = chunk_alloca(password.len * 2 + 2);
for (i = 0; i < password.len; i++)
{
unicode.ptr[i * 2] = 0;
unicode.ptr[i * 2 + 1] = password.ptr[i];
}
unicode.ptr[i * 2] = 0;
unicode.ptr[i * 2 + 1] = 0;
}
success = derive_key(hash, unicode, salt, iterations, type, key);
memwipe(unicode.ptr, unicode.len);
return success;
}
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