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/*
This file is part of TALER
Copyright (C) 2015-2020 Taler Systems SA
TALER 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, or (at your option) any later version.
TALER 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
TALER; see the file COPYING. If not, see
<http://www.gnu.org/licenses/>
*/
/**
* @file lib/exchange_api_refresh_common.c
* @brief Serialization logic shared between melt and reveal steps during refreshing
* @author Christian Grothoff
*/
#include "platform.h"
#include "exchange_api_refresh_common.h"
/**
* Free all information associated with a melted coin session.
*
* @param mc melted coin to release, the pointer itself is NOT
* freed (as it is typically not allocated by itself)
*/
static void
free_melted_coin (struct MeltedCoin *mc)
{
if (NULL != mc->pub_key.rsa_public_key)
GNUNET_CRYPTO_rsa_public_key_free (mc->pub_key.rsa_public_key);
if (NULL != mc->sig.rsa_signature)
GNUNET_CRYPTO_rsa_signature_free (mc->sig.rsa_signature);
}
/**
* Free all information associated with a melting session. Note
* that we allow the melting session to be only partially initialized,
* as we use this function also when freeing melt data that was not
* fully initialized (i.e. due to failures in #TALER_EXCHANGE_deserialize_melt_data_()).
*
* @param md melting data to release, the pointer itself is NOT
* freed (as it is typically not allocated by itself)
*/
void
TALER_EXCHANGE_free_melt_data_ (struct MeltData *md)
{
free_melted_coin (&md->melted_coin);
if (NULL != md->fresh_pks)
{
for (unsigned int i = 0; i<md->num_fresh_coins; i++)
if (NULL != md->fresh_pks[i].rsa_public_key)
GNUNET_CRYPTO_rsa_public_key_free (md->fresh_pks[i].rsa_public_key);
GNUNET_free (md->fresh_pks);
}
for (unsigned int i = 0; i<TALER_CNC_KAPPA; i++)
GNUNET_free_non_null (md->fresh_coins[i]);
/* Finally, clean up a bit...
(NOTE: compilers might optimize this away, so this is
not providing any strong assurances that the key material
is purged.) */
memset (md,
0,
sizeof (struct MeltData));
}
/**
* Serialize information about a coin we are melting.
*
* @param mc information to serialize
* @param buf buffer to write data in, NULL to just compute
* required size
* @param off offeset at @a buf to use
* @return number of bytes written to @a buf at @a off, or if
* @a buf is NULL, number of bytes required; 0 on error
*/
static size_t
serialize_melted_coin (const struct MeltedCoin *mc,
char *buf,
size_t off)
{
struct MeltedCoinP mcp;
void *pbuf;
size_t pbuf_size;
void *sbuf;
size_t sbuf_size;
sbuf_size = GNUNET_CRYPTO_rsa_signature_encode (mc->sig.rsa_signature,
&sbuf);
pbuf_size = GNUNET_CRYPTO_rsa_public_key_encode (mc->pub_key.rsa_public_key,
&pbuf);
if (NULL == buf)
{
GNUNET_free (sbuf);
GNUNET_free (pbuf);
return sizeof (struct MeltedCoinP) + sbuf_size + pbuf_size;
}
if ( (sbuf_size > UINT16_MAX) ||
(pbuf_size > UINT16_MAX) )
{
GNUNET_break (0);
return 0;
}
mcp.coin_priv = mc->coin_priv;
TALER_amount_hton (&mcp.melt_amount_with_fee,
&mc->melt_amount_with_fee);
TALER_amount_hton (&mcp.fee_melt,
&mc->fee_melt);
TALER_amount_hton (&mcp.original_value,
&mc->original_value);
for (unsigned int i = 0; i<TALER_CNC_KAPPA; i++)
mcp.transfer_priv[i] = mc->transfer_priv[i];
mcp.expire_deposit = GNUNET_TIME_absolute_hton (mc->expire_deposit);
mcp.pbuf_size = htons ((uint16_t) pbuf_size);
mcp.sbuf_size = htons ((uint16_t) sbuf_size);
memcpy (&buf[off],
&mcp,
sizeof (struct MeltedCoinP));
memcpy (&buf[off + sizeof (struct MeltedCoinP)],
pbuf,
pbuf_size);
memcpy (&buf[off + sizeof (struct MeltedCoinP) + pbuf_size],
sbuf,
sbuf_size);
GNUNET_free (sbuf);
GNUNET_free (pbuf);
return sizeof (struct MeltedCoinP) + sbuf_size + pbuf_size;
}
/**
* Deserialize information about a coin we are melting.
*
* @param[out] mc information to deserialize
* @param buf buffer to read data from
* @param size number of bytes available at @a buf to use
* @param[out] ok set to #GNUNET_NO to report errors
* @return number of bytes read from @a buf, 0 on error
*/
static size_t
deserialize_melted_coin (struct MeltedCoin *mc,
const char *buf,
size_t size,
int *ok)
{
struct MeltedCoinP mcp;
size_t pbuf_size;
size_t sbuf_size;
size_t off;
if (size < sizeof (struct MeltedCoinP))
{
GNUNET_break (0);
*ok = GNUNET_NO;
return 0;
}
memcpy (&mcp,
buf,
sizeof (struct MeltedCoinP));
pbuf_size = ntohs (mcp.pbuf_size);
sbuf_size = ntohs (mcp.sbuf_size);
if (size < sizeof (struct MeltedCoinP) + pbuf_size + sbuf_size)
{
GNUNET_break (0);
*ok = GNUNET_NO;
return 0;
}
off = sizeof (struct MeltedCoinP);
mc->pub_key.rsa_public_key
= GNUNET_CRYPTO_rsa_public_key_decode (&buf[off],
pbuf_size);
off += pbuf_size;
mc->sig.rsa_signature
= GNUNET_CRYPTO_rsa_signature_decode (&buf[off],
sbuf_size);
off += sbuf_size;
if ( (NULL == mc->pub_key.rsa_public_key) ||
(NULL == mc->sig.rsa_signature) )
{
GNUNET_break (0);
*ok = GNUNET_NO;
return 0;
}
mc->coin_priv = mcp.coin_priv;
TALER_amount_ntoh (&mc->melt_amount_with_fee,
&mcp.melt_amount_with_fee);
TALER_amount_ntoh (&mc->fee_melt,
&mcp.fee_melt);
TALER_amount_ntoh (&mc->original_value,
&mcp.original_value);
for (unsigned int i = 0; i<TALER_CNC_KAPPA; i++)
mc->transfer_priv[i] = mcp.transfer_priv[i];
mc->expire_deposit = GNUNET_TIME_absolute_ntoh (mcp.expire_deposit);
return off;
}
/**
* Serialize information about a denomination key.
*
* @param dk information to serialize
* @param buf buffer to write data in, NULL to just compute
* required size
* @param off offeset at @a buf to use
* @return number of bytes written to @a buf at @a off, or if
* @a buf is NULL, number of bytes required
*/
static size_t
serialize_denomination_key (const struct TALER_DenominationPublicKey *dk,
char *buf,
size_t off)
{
void *pbuf;
size_t pbuf_size;
uint32_t be;
pbuf_size = GNUNET_CRYPTO_rsa_public_key_encode (dk->rsa_public_key,
&pbuf);
if (NULL == buf)
{
GNUNET_free (pbuf);
return pbuf_size + sizeof (uint32_t);
}
be = htonl ((uint32_t) pbuf_size);
memcpy (&buf[off],
&be,
sizeof (uint32_t));
memcpy (&buf[off + sizeof (uint32_t)],
pbuf,
pbuf_size);
GNUNET_free (pbuf);
return pbuf_size + sizeof (uint32_t);
}
/**
* Deserialize information about a denomination key.
*
* @param[out] dk information to deserialize
* @param buf buffer to read data from
* @param size number of bytes available at @a buf to use
* @param[out] ok set to #GNUNET_NO to report errors
* @return number of bytes read from @a buf, 0 on error
*/
static size_t
deserialize_denomination_key (struct TALER_DenominationPublicKey *dk,
const char *buf,
size_t size,
int *ok)
{
size_t pbuf_size;
uint32_t be;
if (size < sizeof (uint32_t))
{
GNUNET_break (0);
*ok = GNUNET_NO;
return 0;
}
memcpy (&be,
buf,
sizeof (uint32_t));
pbuf_size = ntohl (be);
if (size < sizeof (uint32_t) + pbuf_size)
{
GNUNET_break (0);
*ok = GNUNET_NO;
return 0;
}
dk->rsa_public_key
= GNUNET_CRYPTO_rsa_public_key_decode (&buf[sizeof (uint32_t)],
pbuf_size);
if (NULL == dk->rsa_public_key)
{
GNUNET_break (0);
*ok = GNUNET_NO;
return 0;
}
return sizeof (uint32_t) + pbuf_size;
}
/**
* Serialize information about a fresh coin we are generating.
*
* @param fc information to serialize
* @param buf buffer to write data in, NULL to just compute
* required size
* @param off offeset at @a buf to use
* @return number of bytes written to @a buf at @a off, or if
* @a buf is NULL, number of bytes required
*/
static size_t
serialize_fresh_coin (const struct TALER_PlanchetSecretsP *fc,
char *buf,
size_t off)
{
if (NULL != buf)
memcpy (&buf[off],
fc,
sizeof (struct TALER_PlanchetSecretsP));
return sizeof (struct TALER_PlanchetSecretsP);
}
/**
* Deserialize information about a fresh coin we are generating.
*
* @param[out] fc information to deserialize
* @param buf buffer to read data from
* @param size number of bytes available at @a buf to use
* @param[out] ok set to #GNUNET_NO to report errors
* @return number of bytes read from @a buf, 0 on error
*/
static size_t
deserialize_fresh_coin (struct TALER_PlanchetSecretsP *fc,
const char *buf,
size_t size,
int *ok)
{
if (size < sizeof (struct TALER_PlanchetSecretsP))
{
GNUNET_break (0);
*ok = GNUNET_NO;
return 0;
}
memcpy (fc,
buf,
sizeof (struct TALER_PlanchetSecretsP));
return sizeof (struct TALER_PlanchetSecretsP);
}
/**
* Serialize melt data.
*
* @param md data to serialize
* @param[out] res_size size of buffer returned
* @return serialized melt data
*/
static char *
serialize_melt_data (const struct MeltData *md,
size_t *res_size)
{
size_t size;
size_t asize;
char *buf;
size = 0;
asize = (size_t) -1; /* make the compiler happy */
buf = NULL;
/* we do 2 iterations, #1 to determine total size, #2 to
actually construct the buffer */
do {
if (0 == size)
{
size = sizeof (struct MeltDataP);
}
else
{
struct MeltDataP *mdp;
buf = GNUNET_malloc (size);
asize = size; /* just for invariant check later */
size = sizeof (struct MeltDataP);
mdp = (struct MeltDataP *) buf;
mdp->rc = md->rc;
mdp->num_fresh_coins = htons (md->num_fresh_coins);
}
size += serialize_melted_coin (&md->melted_coin,
buf,
size);
for (unsigned int i = 0; i<md->num_fresh_coins; i++)
size += serialize_denomination_key (&md->fresh_pks[i],
buf,
size);
for (unsigned int i = 0; i<TALER_CNC_KAPPA; i++)
for (unsigned int j = 0; j<md->num_fresh_coins; j++)
size += serialize_fresh_coin (&md->fresh_coins[i][j],
buf,
size);
} while (NULL == buf);
GNUNET_assert (size == asize);
*res_size = size;
return buf;
}
/**
* Deserialize melt data.
*
* @param buf serialized data
* @param buf_size size of @a buf
* @return deserialized melt data, NULL on error
*/
struct MeltData *
TALER_EXCHANGE_deserialize_melt_data_ (const char *buf,
size_t buf_size)
{
struct MeltData *md;
struct MeltDataP mdp;
size_t off;
int ok;
if (buf_size < sizeof (struct MeltDataP))
return NULL;
memcpy (&mdp,
buf,
sizeof (struct MeltDataP));
md = GNUNET_new (struct MeltData);
md->rc = mdp.rc;
md->num_fresh_coins = ntohs (mdp.num_fresh_coins);
md->fresh_pks = GNUNET_new_array (md->num_fresh_coins,
struct TALER_DenominationPublicKey);
for (unsigned int i = 0; i<TALER_CNC_KAPPA; i++)
md->fresh_coins[i] = GNUNET_new_array (md->num_fresh_coins,
struct TALER_PlanchetSecretsP);
off = sizeof (struct MeltDataP);
ok = GNUNET_YES;
off += deserialize_melted_coin (&md->melted_coin,
&buf[off],
buf_size - off,
&ok);
for (unsigned int i = 0; (i<md->num_fresh_coins) && (GNUNET_YES == ok); i++)
off += deserialize_denomination_key (&md->fresh_pks[i],
&buf[off],
buf_size - off,
&ok);
for (unsigned int i = 0; i<TALER_CNC_KAPPA; i++)
for (unsigned int j = 0; (j<md->num_fresh_coins) && (GNUNET_YES == ok); j++)
off += deserialize_fresh_coin (&md->fresh_coins[i][j],
&buf[off],
buf_size - off,
&ok);
if (off != buf_size)
{
GNUNET_break (0);
ok = GNUNET_NO;
}
if (GNUNET_YES != ok)
{
TALER_EXCHANGE_free_melt_data_ (md);
GNUNET_free (md);
return NULL;
}
return md;
}
/**
* Melt (partially spent) coins to obtain fresh coins that are
* unlinkable to the original coin(s). Note that melting more
* than one coin in a single request will make those coins linkable,
* so the safest operation only melts one coin at a time.
*
* This API is typically used by a wallet. Note that to ensure that
* no money is lost in case of hardware failures, this operation does
* not actually initiate the request. Instead, it generates a buffer
* which the caller must store before proceeding with the actual call
* to #TALER_EXCHANGE_melt() that will generate the request.
*
* This function does verify that the given request data is internally
* consistent. However, the @a melts_sigs are NOT verified.
*
* Aside from some non-trivial cryptographic operations that might
* take a bit of CPU time to complete, this function returns
* its result immediately and does not start any asynchronous
* processing. This function is also thread-safe.
*
* @param melt_priv private key of the coin to melt
* @param melt_amount amount specifying how much
* the coin will contribute to the melt (including fee)
* @param melt_sig signature affirming the
* validity of the public keys corresponding to the
* @a melt_priv private key
* @param melt_pk denomination key information
* record corresponding to the @a melt_sig
* validity of the keys
* @param fresh_pks_len length of the @a pks array
* @param fresh_pks array of @a pks_len denominations of fresh coins to create
* @param[out] res_size set to the size of the return value, or 0 on error
* @return NULL
* if the inputs are invalid (i.e. denomination key not with this exchange).
* Otherwise, pointer to a buffer of @a res_size to store persistently
* before proceeding to #TALER_EXCHANGE_melt().
* Non-null results should be freed using GNUNET_free().
*/
char *
TALER_EXCHANGE_refresh_prepare (
const struct TALER_CoinSpendPrivateKeyP *melt_priv,
const struct TALER_Amount *melt_amount,
const struct TALER_DenominationSignature *melt_sig,
const struct TALER_EXCHANGE_DenomPublicKey *melt_pk,
unsigned int fresh_pks_len,
const struct TALER_EXCHANGE_DenomPublicKey *fresh_pks,
size_t *res_size)
{
struct MeltData md;
char *buf;
struct TALER_Amount total;
struct TALER_CoinSpendPublicKeyP coin_pub;
struct TALER_TransferSecretP trans_sec[TALER_CNC_KAPPA];
struct TALER_RefreshCommitmentEntry rce[TALER_CNC_KAPPA];
GNUNET_CRYPTO_eddsa_key_get_public (&melt_priv->eddsa_priv,
&coin_pub.eddsa_pub);
/* build up melt data structure */
memset (&md, 0, sizeof (md));
md.num_fresh_coins = fresh_pks_len;
md.melted_coin.coin_priv = *melt_priv;
md.melted_coin.melt_amount_with_fee = *melt_amount;
md.melted_coin.fee_melt = melt_pk->fee_refresh;
md.melted_coin.original_value = melt_pk->value;
md.melted_coin.expire_deposit
= melt_pk->expire_deposit;
GNUNET_assert (GNUNET_OK ==
TALER_amount_get_zero (melt_amount->currency,
&total));
md.melted_coin.pub_key.rsa_public_key
= GNUNET_CRYPTO_rsa_public_key_dup (melt_pk->key.rsa_public_key);
md.melted_coin.sig.rsa_signature
= GNUNET_CRYPTO_rsa_signature_dup (melt_sig->rsa_signature);
md.fresh_pks = GNUNET_new_array (fresh_pks_len,
struct TALER_DenominationPublicKey);
for (unsigned int i = 0; i<fresh_pks_len; i++)
{
md.fresh_pks[i].rsa_public_key
= GNUNET_CRYPTO_rsa_public_key_dup (fresh_pks[i].key.rsa_public_key);
if ( (GNUNET_OK !=
TALER_amount_add (&total,
&total,
&fresh_pks[i].value)) ||
(GNUNET_OK !=
TALER_amount_add (&total,
&total,
&fresh_pks[i].fee_withdraw)) )
{
GNUNET_break (0);
TALER_EXCHANGE_free_melt_data_ (&md);
return NULL;
}
}
/* verify that melt_amount is above total cost */
if (1 ==
TALER_amount_cmp (&total,
melt_amount) )
{
/* Eh, this operation is more expensive than the
@a melt_amount. This is not OK. */
GNUNET_break (0);
TALER_EXCHANGE_free_melt_data_ (&md);
return NULL;
}
/* build up coins */
for (unsigned int i = 0; i<TALER_CNC_KAPPA; i++)
{
struct GNUNET_CRYPTO_EcdhePrivateKey *tpk;
tpk = GNUNET_CRYPTO_ecdhe_key_create ();
md.melted_coin.transfer_priv[i].ecdhe_priv = *tpk;
GNUNET_free (tpk);
GNUNET_CRYPTO_ecdhe_key_get_public (
&md.melted_coin.transfer_priv[i].ecdhe_priv,
&rce[i].transfer_pub.ecdhe_pub);
TALER_link_derive_transfer_secret (melt_priv,
&md.melted_coin.transfer_priv[i],
&trans_sec[i]);
md.fresh_coins[i] = GNUNET_new_array (fresh_pks_len,
struct TALER_PlanchetSecretsP);
rce[i].new_coins = GNUNET_new_array (fresh_pks_len,
struct TALER_RefreshCoinData);
for (unsigned int j = 0; j<fresh_pks_len; j++)
{
struct TALER_PlanchetSecretsP *fc = &md.fresh_coins[i][j];
struct TALER_RefreshCoinData *rcd = &rce[i].new_coins[j];
struct TALER_PlanchetDetail pd;
TALER_planchet_setup_refresh (&trans_sec[i],
j,
fc);
if (GNUNET_OK !=
TALER_planchet_prepare (&md.fresh_pks[j],
fc,
&pd))
{
GNUNET_break_op (0);
TALER_EXCHANGE_free_melt_data_ (&md);
return NULL;
}
rcd->dk = &md.fresh_pks[j];
rcd->coin_ev = pd.coin_ev;
rcd->coin_ev_size = pd.coin_ev_size;
}
}
/* Compute refresh commitment */
TALER_refresh_get_commitment (&md.rc,
TALER_CNC_KAPPA,
fresh_pks_len,
rce,
&coin_pub,
melt_amount);
/* finally, serialize everything */
buf = serialize_melt_data (&md,
res_size);
for (unsigned int i = 0; i < TALER_CNC_KAPPA; i++)
{
for (unsigned int j = 0; j < fresh_pks_len; j++)
GNUNET_free_non_null (rce[i].new_coins[j].coin_ev);
GNUNET_free_non_null (rce[i].new_coins);
}
TALER_EXCHANGE_free_melt_data_ (&md);
return buf;
}
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