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/*
* Copyright (C) 2006 Martin Willi
* 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 "fips_prf.h"
#include <arpa/inet.h>
#include <debug.h>
typedef struct private_fips_prf_t private_fips_prf_t;
/**
* Private data of a fips_prf_t object.
*/
struct private_fips_prf_t {
/**
* Public fips_prf_t interface.
*/
fips_prf_t public;
/**
* key of prf function, "b" long
*/
u_int8_t *key;
/**
* size of "b" in bytes
*/
size_t b;
/**
* Keyed SHA1 prf: It does not use SHA1Final operation
*/
prf_t *keyed_prf;
/**
* G function, either SHA1 or DES
*/
void (*g)(private_fips_prf_t *this, chunk_t c, u_int8_t res[]);
};
/**
* sum = (a + b) mod 2 ^ (length * 8)
*/
static void add_mod(size_t length, u_int8_t a[], u_int8_t b[], u_int8_t sum[])
{
int i, c = 0;
for(i = length - 1; i >= 0; i--)
{
u_int32_t tmp;
tmp = a[i] + b[i] + c;
sum[i] = 0xff & tmp;
c = tmp >> 8;
}
}
/**
* calculate "chunk mod 2^(length*8)" and save it into buffer
*/
static void chunk_mod(size_t length, chunk_t chunk, u_int8_t buffer[])
{
if (chunk.len < length)
{
/* apply seed as least significant bits, others are zero */
memset(buffer, 0, length - chunk.len);
memcpy(buffer + length - chunk.len, chunk.ptr, chunk.len);
}
else
{
/* use least significant bytes from seed, as we use mod 2^b */
memcpy(buffer, chunk.ptr + chunk.len - length, length);
}
}
/**
* Implementation of prf_t.get_bytes.
*
* Test vector:
*
* key:
* 0xbd, 0x02, 0x9b, 0xbe, 0x7f, 0x51, 0x96, 0x0b,
* 0xcf, 0x9e, 0xdb, 0x2b, 0x61, 0xf0, 0x6f, 0x0f,
* 0xeb, 0x5a, 0x38, 0xb6
*
* seed:
* 0x00
*
* result:
* 0x20, 0x70, 0xb3, 0x22, 0x3d, 0xba, 0x37, 0x2f,
* 0xde, 0x1c, 0x0f, 0xfc, 0x7b, 0x2e, 0x3b, 0x49,
* 0x8b, 0x26, 0x06, 0x14, 0x3c, 0x6c, 0x18, 0xba,
* 0xcb, 0x0f, 0x6c, 0x55, 0xba, 0xbb, 0x13, 0x78,
* 0x8e, 0x20, 0xd7, 0x37, 0xa3, 0x27, 0x51, 0x16
*/
static void get_bytes(private_fips_prf_t *this, chunk_t seed, u_int8_t w[])
{
int i;
u_int8_t xval[this->b];
u_int8_t xseed[this->b];
u_int8_t sum[this->b];
u_int8_t *xkey = this->key;
u_int8_t one[this->b];
memset(one, 0, this->b);
one[this->b - 1] = 0x01;
/* 3.1 */
chunk_mod(this->b, seed, xseed);
/* 3.2 */
for (i = 0; i < 2; i++) /* twice */
{
/* a. XVAL = (XKEY + XSEED j) mod 2^b */
add_mod(this->b, xkey, xseed, xval);
DBG3(DBG_LIB, "XVAL %b", xval, this->b);
/* b. wi = G(t, XVAL ) */
this->g(this, chunk_create(xval, this->b), &w[i * this->b]);
DBG3(DBG_LIB, "w[%d] %b", i, &w[i * this->b], this->b);
/* c. XKEY = (1 + XKEY + wi) mod 2b */
add_mod(this->b, xkey, &w[i * this->b], sum);
add_mod(this->b, sum, one, xkey);
DBG3(DBG_LIB, "XKEY %b", xkey, this->b);
}
/* 3.3 done already, mod q not used */
}
/**
* Implementation of prf_t.get_block_size.
*/
static size_t get_block_size(private_fips_prf_t *this)
{
return 2 * this->b;
}
/**
* Implementation of prf_t.allocate_bytes.
*/
static void allocate_bytes(private_fips_prf_t *this, chunk_t seed, chunk_t *chunk)
{
*chunk = chunk_alloc(get_block_size(this));
get_bytes(this, seed, chunk->ptr);
}
/**
* Implementation of prf_t.get_key_size.
*/
static size_t get_key_size(private_fips_prf_t *this)
{
return this->b;
}
/**
* Implementation of prf_t.set_key.
*/
static void set_key(private_fips_prf_t *this, chunk_t key)
{
/* save key as "key mod 2^b" */
chunk_mod(this->b, key, this->key);
}
/**
* Implementation of the G() function based on SHA1
*/
void g_sha1(private_fips_prf_t *this, chunk_t c, u_int8_t res[])
{
u_int8_t buf[64];
if (c.len < sizeof(buf))
{
/* pad c with zeros */
memset(buf, 0, sizeof(buf));
memcpy(buf, c.ptr, c.len);
c.ptr = buf;
c.len = sizeof(buf);
}
else
{
/* not more than 512 bits can be G()-ed */
c.len = sizeof(buf);
}
/* use the keyed hasher, but use an empty key to use SHA1 IV */
this->keyed_prf->set_key(this->keyed_prf, chunk_empty);
this->keyed_prf->get_bytes(this->keyed_prf, c, res);
}
/**
* Implementation of prf_t.destroy.
*/
static void destroy(private_fips_prf_t *this)
{
this->keyed_prf->destroy(this->keyed_prf);
free(this->key);
free(this);
}
/*
* Described in header.
*/
fips_prf_t *fips_prf_create(pseudo_random_function_t algo)
{
private_fips_prf_t *this = malloc_thing(private_fips_prf_t);
this->public.prf_interface.get_bytes = (void (*) (prf_t *,chunk_t,u_int8_t*))get_bytes;
this->public.prf_interface.allocate_bytes = (void (*) (prf_t*,chunk_t,chunk_t*))allocate_bytes;
this->public.prf_interface.get_block_size = (size_t (*) (prf_t*))get_block_size;
this->public.prf_interface.get_key_size = (size_t (*) (prf_t*))get_key_size;
this->public.prf_interface.set_key = (void (*) (prf_t *,chunk_t))set_key;
this->public.prf_interface.destroy = (void (*) (prf_t *))destroy;
switch (algo)
{
case PRF_FIPS_SHA1_160:
{
this->g = g_sha1;
this->b = 20;
this->keyed_prf = lib->crypto->create_prf(lib->crypto, PRF_KEYED_SHA1);
if (this->keyed_prf == NULL)
{
free(this);
return NULL;
}
break;
}
case PRF_FIPS_DES:
/* not implemented yet */
default:
free(this);
return NULL;
}
this->key = malloc(this->b);
return &this->public;
}
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