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/*
* Copyright (c) 2006 - 2007 Kungliga Tekniska Högskolan
* (Royal Institute of Technology, Stockholm, Sweden).
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <roken.h>
#include <krb5-types.h>
#include <rfc2459_asn1.h>
#include <dh.h>
/**
* @page page_dh DH - Diffie-Hellman key exchange
*
* Diffie-Hellman key exchange is a protocol that allows two parties
* to establish a shared secret key.
*
* Include and example how to use DH_new() and friends here.
*
* See the library functions here: @ref hcrypto_dh
*/
/**
* Create a new DH object using DH_new_method(NULL), see DH_new_method().
*
* @return a newly allocated DH object.
*
* @ingroup hcrypto_dh
*/
DH *
DH_new(void)
{
return DH_new_method(NULL);
}
/**
* Create a new DH object from the given engine, if the NULL is used,
* the default engine is used. Free the DH object with DH_free().
*
* @param engine The engine to use to allocate the DH object.
*
* @return a newly allocated DH object.
*
* @ingroup hcrypto_dh
*/
DH *
DH_new_method(ENGINE *engine)
{
DH *dh;
dh = calloc(1, sizeof(*dh));
if (dh == NULL)
return NULL;
dh->references = 1;
if (engine) {
ENGINE_up_ref(engine);
dh->engine = engine;
} else {
dh->engine = ENGINE_get_default_DH();
}
if (dh->engine) {
dh->meth = ENGINE_get_DH(dh->engine);
if (dh->meth == NULL) {
ENGINE_finish(dh->engine);
free(dh);
return 0;
}
}
if (dh->meth == NULL)
dh->meth = DH_get_default_method();
(*dh->meth->init)(dh);
return dh;
}
/**
* Free a DH object and release related resources, like ENGINE, that
* the object was using.
*
* @param dh object to be freed.
*
* @ingroup hcrypto_dh
*/
void
DH_free(DH *dh)
{
if (dh->references <= 0)
abort();
if (--dh->references > 0)
return;
(*dh->meth->finish)(dh);
if (dh->engine)
ENGINE_finish(dh->engine);
#define free_if(f) if (f) { BN_free(f); }
free_if(dh->p);
free_if(dh->g);
free_if(dh->pub_key);
free_if(dh->priv_key);
free_if(dh->q);
free_if(dh->j);
free_if(dh->counter);
#undef free_if
memset(dh, 0, sizeof(*dh));
free(dh);
}
/**
* Add a reference to the DH object. The object should be free with
* DH_free() to drop the reference.
*
* @param dh the object to increase the reference count too.
*
* @return the updated reference count, can't safely be used except
* for debug printing.
*
* @ingroup hcrypto_dh
*/
int
DH_up_ref(DH *dh)
{
return ++dh->references;
}
/**
* The maximum output size of the DH_compute_key() function.
*
* @param dh The DH object to get the size from.
*
* @return the maximum size in bytes of the out data.
*
* @ingroup hcrypto_dh
*/
int
DH_size(const DH *dh)
{
return BN_num_bytes(dh->p);
}
/**
* Set the data index idx in the DH object to data.
*
* @param dh DH object.
* @param idx index to set the data for.
* @param data data to store for the index idx.
*
* @return 1 on success.
*
* @ingroup hcrypto_dh
*/
int
DH_set_ex_data(DH *dh, int idx, void *data)
{
dh->ex_data.sk = data;
return 1;
}
/**
* Get the data for index idx in the DH object.
*
* @param dh DH object.
* @param idx index to get the data for.
*
* @return the object store in index idx
*
* @ingroup hcrypto_dh
*/
void *
DH_get_ex_data(DH *dh, int idx)
{
return dh->ex_data.sk;
}
/**
* Generate DH parameters for the DH object give parameters.
*
* @param dh The DH object to generate parameters for.
* @param prime_len length of the prime
* @param generator generator, g
* @param cb Callback parameters to show progress, can be NULL.
*
* @return the maximum size in bytes of the out data.
*
* @ingroup hcrypto_dh
*/
int
DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb)
{
if (dh->meth->generate_params)
return dh->meth->generate_params(dh, prime_len, generator, cb);
return 0;
}
/**
* Check that the public key is sane.
*
* @param dh the local peer DH parameters.
* @param pub_key the remote peer public key parameters.
* @param codes return that the failures of the pub_key are.
*
* @return 1 on success, 0 on failure and *codes is set the the
* combined fail check for the public key
*
* @ingroup hcrypto_dh
*/
int
DH_check_pubkey(const DH *dh, const BIGNUM *pub_key, int *codes)
{
BIGNUM *bn = NULL, *sum = NULL;
int ret = 0;
*codes = 0;
/**
* Checks that the function performs are:
* - pub_key is not negative
*/
if (BN_is_negative(pub_key))
goto out;
/**
* - pub_key > 1 and pub_key < p - 1,
* to avoid small subgroups attack.
*/
bn = BN_new();
if (bn == NULL)
goto out;
if (!BN_set_word(bn, 1))
goto out;
if (BN_cmp(bn, pub_key) >= 0)
*codes |= DH_CHECK_PUBKEY_TOO_SMALL;
sum = BN_new();
if (sum == NULL)
goto out;
BN_uadd(sum, pub_key, bn);
if (BN_cmp(sum, dh->p) >= 0)
*codes |= DH_CHECK_PUBKEY_TOO_LARGE;
/**
* - if g == 2, pub_key have more then one bit set,
* if bits set is 1, log_2(pub_key) is trival
*/
if (!BN_set_word(bn, 2))
goto out;
if (BN_cmp(bn, dh->g) == 0) {
unsigned i, n = BN_num_bits(pub_key);
unsigned bits = 0;
for (i = 0; i < n; i++)
if (BN_is_bit_set(pub_key, i))
bits++;
if (bits < 2) {
*codes |= DH_CHECK_PUBKEY_TOO_SMALL;
goto out;
}
}
ret = 1;
out:
if (bn)
BN_free(bn);
if (sum)
BN_free(sum);
return ret;
}
/**
* Generate a new DH private-public key pair. The dh parameter must be
* allocted first with DH_new(). dh->p and dp->g must be set.
*
* @param dh dh parameter.
*
* @return 1 on success.
*
* @ingroup hcrypto_dh
*/
int
DH_generate_key(DH *dh)
{
return dh->meth->generate_key(dh);
}
/**
* Complute the shared secret key.
*
* @param shared_key the resulting shared key, need to be at least
* DH_size() large.
* @param peer_pub_key the peer's public key.
* @param dh the dh key pair.
*
* @return 1 on success.
*
* @ingroup hcrypto_dh
*/
int
DH_compute_key(unsigned char *shared_key,
const BIGNUM *peer_pub_key, DH *dh)
{
int codes;
/**
* Checks that the pubkey passed in is valid using
* DH_check_pubkey().
*/
if (!DH_check_pubkey(dh, peer_pub_key, &codes) || codes != 0)
return -1;
return dh->meth->compute_key(shared_key, peer_pub_key, dh);
}
/**
* Set a new method for the DH keypair.
*
* @param dh dh parameter.
* @param method the new method for the DH parameter.
*
* @return 1 on success.
*
* @ingroup hcrypto_dh
*/
int
DH_set_method(DH *dh, const DH_METHOD *method)
{
(*dh->meth->finish)(dh);
if (dh->engine) {
ENGINE_finish(dh->engine);
dh->engine = NULL;
}
dh->meth = method;
(*dh->meth->init)(dh);
return 1;
}
/*
*
*/
static int
dh_null_generate_key(DH *dh)
{
return 0;
}
static int
dh_null_compute_key(unsigned char *shared,const BIGNUM *pub, DH *dh)
{
return 0;
}
static int
dh_null_init(DH *dh)
{
return 1;
}
static int
dh_null_finish(DH *dh)
{
return 1;
}
static int
dh_null_generate_params(DH *dh, int prime_num, int len, BN_GENCB *cb)
{
return 0;
}
static const DH_METHOD dh_null_method = {
"hcrypto null DH",
dh_null_generate_key,
dh_null_compute_key,
NULL,
dh_null_init,
dh_null_finish,
0,
NULL,
dh_null_generate_params
};
extern const DH_METHOD _hc_dh_ltm_method;
static const DH_METHOD *dh_default_method = &_hc_dh_ltm_method;
/**
* Return the dummy DH implementation.
*
* @return pointer to a DH_METHOD.
*
* @ingroup hcrypto_dh
*/
const DH_METHOD *
DH_null_method(void)
{
return &dh_null_method;
}
/**
* Set the default DH implementation.
*
* @param meth pointer to a DH_METHOD.
*
* @ingroup hcrypto_dh
*/
void
DH_set_default_method(const DH_METHOD *meth)
{
dh_default_method = meth;
}
/**
* Return the default DH implementation.
*
* @return pointer to a DH_METHOD.
*
* @ingroup hcrypto_dh
*/
const DH_METHOD *
DH_get_default_method(void)
{
return dh_default_method;
}
/*
*
*/
static int
bn2heim_int(BIGNUM *bn, heim_integer *integer)
{
integer->length = BN_num_bytes(bn);
integer->data = malloc(integer->length);
if (integer->data == NULL) {
integer->length = 0;
return ENOMEM;
}
BN_bn2bin(bn, integer->data);
integer->negative = BN_is_negative(bn);
return 0;
}
/**
*
*/
int
i2d_DHparams(DH *dh, unsigned char **pp)
{
DHParameter data;
size_t size;
int ret;
memset(&data, 0, sizeof(data));
if (bn2heim_int(dh->p, &data.prime) ||
bn2heim_int(dh->g, &data.base))
{
free_DHParameter(&data);
return -1;
}
if (pp == NULL) {
size = length_DHParameter(&data);
free_DHParameter(&data);
} else {
void *p;
size_t len;
ASN1_MALLOC_ENCODE(DHParameter, p, len, &data, &size, ret);
free_DHParameter(&data);
if (ret)
return -1;
if (len != size) {
abort();
return -1;
}
memcpy(*pp, p, size);
free(p);
*pp += size;
}
return size;
}
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